To see the other types of publications on this topic, follow the link: Correlations.
Dissertations / Theses on the topic 'Correlations'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Correlations.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Toy, Randy Scott. "CORRELATIONS." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd_retro/7.
Full textAbstract:
I explore visual and process-based systems to solidify the allusive nature of conceptual ideas. Impermanence, time and interdependence are reoccurring themes that stem from an interest in Eastern philosophy. Oscillating from representation to abstract minimalism, printmaking to sculpture, each element in a work is tailored to the concept. The minimalist appearance suggests simplicity, however elaborate planning and systematic execution are at the heart of my practice. Systems create great constraint, yet provide great freedom.
2
Hystad, Grethe. "Periodic Ising Correlations." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/196130.
Full textAbstract:
We consider the finite two-dimensional Ising model on a lattice with periodic boundaryconditions. Kaufman determined the spectrum of the transfer matrix on the finite,periodic lattice, and her derivation was a simplification of Onsager's famous result onsolving the two-dimensional Ising model. We derive and rework Kaufman's resultsby applying representation theory, which give us a more direct approach to computethe spectrum of the transfer matrix. We determine formulas for the spin correlationfunction that depend on the matrix elements of the induced rotation associated withthe spin operator. The representation of the spin matrix elements is obtained byconsidering the spin operator as an intertwining map. We wrap the lattice aroundthe cylinder taking the semi-infinite volume limit. We control the scaling limit of themulti-spin Ising correlations on the cylinder as the temperature approaches the criticaltemperature from below in terms of a Bugrij-Lisovyy conjecture for the spin matrixelements on the finite, periodic lattice. Finally, we compute the matrix representationof the spin operator for temperatures below the critical temperature in the infinite-volume limit in the pure state defined by plus boundary conditions.
3
Martinsson, Engshagen Jan. "Nothing is normal in nance! : On Tail Correlations and Robust Higher Order Moments in Normal Portfolio Frameworks." Thesis, KTH, Matematik (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102699.
Full textAbstract:
Abstract This thesis project is divided in two parts. The first part examines the possibility that correlation matrix estimates based on an outlier sample would contain information about extreme events. According to my findings, such methods do not perform better than simple shrinkage methods where robust shrinkage targets are used. The method tested is especially outperformed when it comes to the extreme events, where a shrinkage of the correlation matrix towards the identity matrix seems to give the best result. The second part is about valuation of skewness in marginal distributions and the penalizing of heavy tails. I argue that it is reasonable to use a degrees of freedom parameter instead of kurtosis and a certain regression parameter, that I develop, instead of skewness due to robustness issues. When minimizing the one period draw-down is our target, the "value" of skewness seems to have a linear relationship with expected returns. Re-valuing of expected returns, in terms of skewness, in the standard Markowitz framework will tend to lower expected shortfall (ES), increase skewness and lower the realized portfolio variance. Penalizing of heavy tails will most times in the same way lower ES, lower kurtosis and realized portfolio variance. The results indicate that the parameters representing higher order moments in some way characterize the assets and also reflect their future behavior. These properties can be used in a simple optimization framework and seem to have a positive impact even on portfolio level
4
Perarnau, Llobet Martí. "Thermodynamics and quantum correlations." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404732.
Full textAbstract:
Thermodynamics traditionally deals with macroscopic systems at thermal equilibrium. However, since the very beginning of the theory, its range of applicability has only increased, nowadays being applied to virtually every field of science, and to systems of extremely different size.
This thesis is devoted to the study of thermodynamics in the quantum regime. It contains original results on topics that include: Work extraction from quantum systems, fluctuations of work, the energetic value of correlations and entanglement, and the thermodynamics of closed quantum many body systems.
First, we study work extraction from thermally isolated systems. Here the notion of passive states naturally arises, as those quantum states from which no work can be extracted. We start by characterising the set of passive states, and find the most energetic passive states, a dual family to the well known Gibbs (or thermal) states. Remarkably, passive states have the property of activation: When considered as a whole, several copies of passive states can become nonpassive. We study the dynamics of activation processes, and find a relation between the entanglement generated and the speed of the process.
Next, we consider the possibility of extracting work from a system using an auxiliary thermal bath. In this case, according to the second law of thermodynamics, the amount of work is bounded by the free energy difference.
We develop corrections to this law which arise from the finite size and the structure of the bath.
We go on by studying the fluctuations of work. Fluctuations are particularly relevant for small systems, where their relative size is comparable to the average value itself. However, characterising the fluctuations in the quantum regime is particularly difficult, as measurements generically disturb the state. In fact, we derive a no go result, showing that it is not possible to exactly measure the fluctuations of work in quantum coherent processes. Despite this result, we develop a new scheme that allows for their approximate measurement.
An important part of this thesis is devoted to the relation between quantum correlations and work. We start by considering a set of correlated states which are thermal at the local level, in which case the extractable work can only come from the correlations. We compute the amount of work that can be stored in entangled, separable and correlated states with a fixed entropy, by finding the corresponding optimal states and protocols. These results provide fundamental bounds on the potential of different type of correlations for work storage and extraction. Next, we consider the converse scenario, and study the creation of correlations from thermal states. We find thresholds on the maximal temperature for the generation of entanglement. We also work out the minimal work cost of creating different types of correlations, including total correlations, entanglement, and genuine multipartite entanglement.
Finally, we study the thermodynamics of closed quantum systems. Here we use one of the most important recent insights from the study of equilibration in quantum systems: Closed many body systems do not equilibrate, but can be effectively described as if they had equilibrated when looking at a restricted, physically relevant, class of observables. Importantly, the corresponding equilibrium state is not necessarily a Gibbs state, but may be very well given by a Generalized Gibbs ensemble state. With this in mind, we develop a framework for studying entropy production and work extraction in closed quantum systems.<br>La termodinàmica va néixer com una teoria dedicada a l'estudi de cossos macroscòpics en equilibri tèrmic. A partir d'aquell moment, l'abast de la teoria no ha deixat d'augmentar, aplicant-se en l'actualitat a gran part de les disciplines científiques, així com a objectes de mides extremadament diferents. La present tesis està dedicada a l'estudi de la termodinàmica de sistemes quàntics. Conté resultats originals en diferents temes, que inclouen l'extracció de treball de sistemes quàntics, les fluctuacions de treball, la relació entre l'energia i les correlacions quàntiques, i la termodinàmica de sistemes de molts cossos. La primera part de la tesis està dedicada a l'estudi de l'extracció de treball de sistemes quàntics. En aquest context la noció d'estat passiu (un estat del qual no es pot extreure treball) és fonamental. Primer de tot, caracteritzem el conjunt d'estats passius, i en particular trobem els més energètics, que es troben a l'altre extrem dels estats tèrmics (o de Gibbs). Notablement, els estats passius poden ser activats, en el sentit que es pot extreure treball d'un conjunt suficientment gran de còpies d'un estat passiu. Estudiant en detall l'esmentat procés d'activació, trobem una relació entre la velocitat del procés i l'entrellaçament generat. Seguidament, considerem la possibilitat d'extreure treball d'un sistema utilitzant un bany tèrmic. En aquest cas, d'acord amb la segona llei de la termodinàmica, la quantitat de treball està limitada per l'energia lliure. Per sistemes quàntics, en molts casos no és possible extreure tota l'energia lliure, i desenvolupem correccions de la segona llei que depenen només de la mida del bany i de la seva estructura. A continuació estudiem les fluctuacions termodinàmiques (en particular del treball), que són especialment rellevants per sistemes microscòpics. La seva descripció en el règim quàntic és especialment difícil, donat que les mesures tenen un efecte invasiu en l'estat. De fet, mostrem que és impossible mesurar exactament les fluctuacions d'energia en processos que involucren coherència quàntica. Malgrat aquest resultat, també desenvolupem un sistema per mesurar les fluctuacions del treball de forma aproximada. Una part important d'aquesta tesis està dedicada a la relació entre les correlacions (quàntiques) i el treball. Comencem considerant un conjunt d'estats correlacionats, que individualment es troben en un estat tèrmic. La motivació és que en aquest cas el treball contingut en els estats prové únicament de les correlacions. En aquest escenari, calculem la quantitat de treball que es pot extreure d'estats entrellaçats, estats separables i estats correlacionats amb una determinada entropia. És a dir, calculem el treball màxim que es pot extreure de les correlacions, tan clàssiques com quàntiques. A continuació, considerem el procés invers, és a dir, la creació de correlacions en estats tèrmics. En aquest cas derivem límits en la temperatura màxima per poder crear diferents tipus entrellaçament, i el corresponent cost energètic. Finalment, estudiem la termodinàmica de sistemes de molts cossos. Aquí fem servir un dels resultats més importants relacionats amb l'equilibració en sistemes quàntics: sistemes quàntics tancats que involucren moltes partícules no arriben a l'equilibri, però es comporten com si hi haguessin arribat per la majoria d'observables (incloent observables rellevants des d'un punt de vista físic com l'energia). Tanmateix, el corresponent estat d'equilibri no és sempre tèrmic, i a vegades només es pot descriure mitjançant un estat generalitzat de Gibbs (GGE). La nostra contribució consisteix en desenvolupar un formalisme que permet estudiar la producció d'entropia i l'extracció del treball en estats GGE, el qual apliquem a sistemes de fermions.
5
Matte, Robert. "Correlations and multifractal measures." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56945.
Full textAbstract:
This thesis explores the relationships between multifractal measures, multiplicative cascades and correlations. A review of fractal geometry, multifractal formalism and multiplicative cascades is offered. The importance of the Legendre transformation in multifractal formalism is highlighted, especially for multifractal spectrums which are not convex or twice differentiable. By reconsidering the scaling assumption $N sb{p}( alpha$) d$ alpha$ = $ sigma( alpha) rho sp{-f( alpha)} d alpha$, we show that subsets of a measure may offer a different multifractal spectrum. A gradation of self-similarity and scaling vis-a-vis canonicity is offered. Localized and generalized correlations are introduced, and two-point correlations are revisited for multiplicative cascades. A three-point correlation function is presented and discussed. The presence of an integral scale is shown to produce a more involved correlation scaling behaviour.
6
Parker, Jane Ker. "Crystal structure reactivity correlations." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316782.
Full text
7
Lothian, Paul James Gillougley. "On correlations of sequences." Thesis, Royal Holloway, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286326.
Full text
8
Ekert, Artur Konrad. "Correlations in quantum optics." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293479.
Full text
9
Saunders, Christopher Glenn. "Magnetostructural Correlations in Tetrahalocuprates." Thesis, University of Canterbury. Chemistry, 2012. http://hdl.handle.net/10092/8651.
Full textAbstract:
This thesis describes the preparation and characterisation of a number of tetrahalocuprate complexes. The compounds were made by reacting the chosen organic cation with the desired copper(II) salt. Three series of tetrahalocuprates were studied; (1) 5-amino-2-substituted pyridines, (2) mixed halide tetrahalocuprates using different dimethylpyridine isomers and (3) imidazolium ions.
The structure of thirty three compounds were determined using single crystal X-ray crystallography. The compounds studied gave a wide range of different structures.
The 5-amino-2-substituted pyridines showed four distinct structural types; (1) two isolated protonated pyridines and a single tetrahalocuprate anion, (2) unexpected bromine substitution on the pyridine rings, (3) Cu₃Cl chains with two pyridines bound to each terminal copper and (4) water bridged copper chloride chains for the iodo substituted pyridine.
The mixed halide dimethylpyridine series illustrated the effects of varying the ratio of the halides in the tetrahalocuprate anions on the crystal packing of the compounds. A number of different structures for each isomer were studied.
Attempts were made using a range of different imidazolium ions to form tetrahalocuprates. These ions would not require acid protonation and are unknown in the literature in this manner.
10
Hughes, John Rhys. "Octupole correlations in '2'2'5Th." Thesis, University of York, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235660.
Full text
11
Jones, Nicholas Steven. "Correlations : quantum and classical." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424643.
Full text
12
Menga, Marina. "Entanglement detection measuring classical correlations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13510/.
Full textAbstract:
L'entanglement è un fenomeno di natura puramente quantistica ed è considerato la principale risorsa dei protocolli quantistici di manipolazione e trasmissione di informazione.
Lo studio e la caratterizzazione dell'entanglement rivestono dunque un ruolo cruciale nello sviluppo della teoria dell'informazione quantistica e nella comprensione delle strutture fondamentali della meccanica quantistica non relativistica.
Uno dei principali problemi legati alla teoria dell'entanglement è quello di trovare dei criteri ottimali per la rilevazione, la caratterizzazione e la quantificazione dell'entanglement. Ad oggi, non esiste una soluzione completa per questo problema.
In questo lavoro di tesi, abbiamo esaminato e generalizzato un criterio per la rilevazione dell'entanglement basato sulla misura delle correlazioni classiche esistenti tra osservabili locali complementari di un sistema bipartito. In particolare, ci siamo occupati dei criteri che si basano sulla misura dell'informazione mutua, e abbiamo analizzato le prestazioni di questo criterio per una generica coppia di osservabili, non necessariamente complementari. Le prestazioni del nuovo criterio, in termini di efficienza, robustezza ed applicabilità, sono state analizzate in dettaglio per sistemi bipartiti di qubit, poichè in questo caso l'entanglement è completamente caratterizzato e sono a disposizione strumenti di confronto. In particolare, il criterio è stato utilizzato per la rivelazione di entanglement in presenza di rumore esterno e decoerenza.
L'analisi condotta in questa tesi ha mostrato che il criterio presentato è robusto, dal momento che la percentuale di stati rivelati non cala in maniera drammatica quando ci si sposta dalla condizione di complementarietà, e inoltre, pur non avendo performance ottimali rispetto ad altri metodi di rilevazione dell'entanglement, è interessante dal punto di vista applicativo poichè si è rivelato affidabile e complessivamente efficiente.
13
Tröster, Tilman. "Weak gravitational lensing cross-correlations." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62592.
Full textAbstract:
The matter content of the Universe is dominated by dark matter. Beyond its abundance and its lack of non-gravitational interactions with standard model matter, little is known about the nature of dark matter. This thesis attempts to illuminate different aspects of dark matter by using gravitational lensing in conjunction with other cosmological probes. Gravitational lensing describes the deflection of light by gravitational potentials and is a direct and unbiased probe of the matter distribution in the Universe.
We investigate the weakly interacting massive particle (WIMP) model of dark matter by performing a tomographic and spectral cross-correlation between weak gravitational lensing from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), Red Cluster Sequence Lensing Survey (RCSLenS), and Kilo-Degree Survey (KiDS), and gamma rays from Fermi-LAT. The non-detection of a correlation allows us to constrain the allowed masses, annihilation cross-sections, and decay rates of WIMP dark matter.
Even though most matter in the Universe is dark matter, about 16% is baryonic matter. To make precision measurements of the dark matter distribution with gravitational lensing, it is therefore necessary to understand the behaviour and distribution of baryonic matter. We measure and analyse the cross-correlation between weak gravitational lensing from RCSLenS and the thermal Sunyaev-Zeldovich (tSZ) effect from the Planck satellite to constrain the effect of baryon physics on the matter distribution.
Models of gravitational lensing often make use of a range of approximations. We study the effect of dropping these approximations on the cross-correlation between gravitational lensing and tSZ by performing a detailed calculation up to fourth order in the gravitational potential. We find that the common approximations are sufficiently accurate even for future surveys.
Finally, we explore the growth of structure and the effect of residual weak lensing systematics in a tomographic cross-correlation between weak gravitational lensing from KiDS and lensing of the cosmic microwave background (CMB) from Planck.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
14
Korkusinski, Marek. "Correlations in semiconductor quantum dots." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29128.
Full textAbstract:
In this Thesis, I present a theoretical study of correlation effects in strongly interacting electronic and electron-hole systems confined in semiconductor quantum dots. I focus on three systems: N electrons in a two-dimensional parabolic confinement in the absence and in the presence of a magnetic field, an electron-hole pair confined in a vertically coupled double-quantum-dot molecule, and a charged exciton in a quantum-ring confinement in a magnetic field.
To analyse these systems I use the exact diagonalisation technique in the effective-mass approximation. This approach consists of three steps: construction of a basis set of particle configurations, writing the Hamiltonian in this basis in a matrix form, and numerical diagonalisation of this matrix. Each of these steps is described in detail in the text.
Using the exact diagonalisation technique I identify the properties of the systems due to correlations and formulate predictions of how these properties could be observed experimentally. I confront these predictions with results of recent photoluminescence and transport measurements.
First I treat the system of N electrons in a parabolic confinement in the absence of magnetic field and demonstrate how its properties, such as magnetic moments, can be engineered as a function of the system parameters and the size of the Hilbert space.
Next I analyse the evolution of the ground state of this system as a function of the magnetic field. In the phase diagram of the system I identify the spin-singlet nu = 2 phase and discuss how correlations influence its phase boundaries both as a function of the magnetic field and the number of electrons.
I also demonstrate that in higher magnetic fields electronic correlations lead to the appearance of spin-depolarised phases, whose stability regions separate the weakly correlated phases with higher spin. Further on, I consider electron-hole systems. I show that the Coulomb interaction leads to entanglement of the states of an electron and a hole confined in a pair of vertically coupled quantum dots.
Finally I consider the system of two electrons and one hole (a negatively charged exciton) confined in a quantum ring and in the presence of the magnetic field. I show that the energy of a single electron in the ring geometry exhibits the Aharonov-Bohm oscillations as a function of the magnetic field. In the case of the negatively charged exciton these oscillations are nearly absent due to correlations among particles, and as a result the photoluminescence spectra of the charged complex are dominated by the energy of the final-state electron. The Aharonov-Bohm oscillations of the energy of a single electron are thus observed directly in the optical spectra.
15
Sloggett, Clare Physics Faculty of Science UNSW. "Electron correlations in mesoscopic systems." Awarded by:University of New South Wales. School of Physics, 2007. http://handle.unsw.edu.au/1959.4/31875.
Full textAbstract:
This thesis deals with electron correlation effects within low-dimensional, mesoscopic systems. We study phenomena within two different types of system in which correlations play an important role. The first involves the spectra and spin structure of small symmetric quantum dots, or "eartificial atoms"e. The second is the "e0.7 structure"e, a well-known but mysterious anomalous conductance plateau which occurs in the conductance profile of a quantum point contact. Artificial atoms are manufactured mesoscopic devices: quantum dots which resemble real atoms in that their symmetry gives them a "eshell structure"e. We examine two-dimensional circular artificial atoms numerically, using restricted and unrestricted Hartree-Fock simulation. We go beyond the mean-field approximation by direct calculation of second-order correlation terms; a method which works well for real atoms but to our knowledge has not been used before for quantum dots. We examine the spectra and spin structure of such dots and find, contrary to previous theoretical mean-field studies, that Hund's rule is not followed. We also find, in agreement with previous numerical studies, that the shell structure is fragile with respect to a simple elliptical deformation. The 0.7 structure appears in the conductance of a quantum point contact. The conductance through a ballistic quantum point contact is quantised in units of 2e^2/h. On the lowest conductance step, an anomalous narrow conductance plateau at about G = 0.7 x 2e^2/h is known to exist, which cannot be explained in the non-interacting picture. Based on suggestive numerical results, we model conductance through the lowest channel of a quantum point contact analytically. The model is based on the screening of the electron-electron interaction outside the QPC, and our observation that the wavefunctions at the Fermi level are peaked within the QPC. We use a kinetic equation approach, with perturbative account of electron-electron backscattering, to demonstrate that these simple features lead to the existence of a 0.7-like structure in the conductance. The behaviour of this structure reproduces experimentally observed features of the 0.7 structure, including the temperature dependence and the behaviour under applied in-plane magnetic fields.
16
Syratt, Richard William. "Angular correlations of speckle patterns." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261820.
Full text
17
Girolami, Davide. "Quantum correlations in information theory." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13397/.
Full textAbstract:
The project concerned the study of quantum correlations (QC) in compound systems, i.e. statistical correlations more general than entanglement which are predicted by quantum mechanics but not described in any classical scenario. I aimed to understand the technical and operational properties of the measures of QC, their interplay with entanglement quantifiers and the experimental accessibility. In the first part of my research path, after having acquired the conceptual and technical rudiments of the project, I provided solutions for some computational issues: I developed analytical and numerical algorithms for calculating bipartite QC in finite dimensional systems. Then, I tackled the problem of the experimental detection of QC. There is no Hermitian operator associated with entanglement measures, nor with QC ones. However, the information encoded in a density matrix is redundant to quantify them, thus the full knowledge of the state is not required to accomplish the task. I reported the first protocol to measure the QC of an unknown state by means of a limited number of measurements, without performing the tomography of the state. My proposal has been implemented experimentally in a NMR (Nuclear Magnetic Resonance) setting. In the final stage of the project, I explored the foundational and operational merits of QC. I showed that the QC shared by two subsystems yield a genuinely quantum kind of uncertainty on single local observables. The result is a promising evidence of the potential exploitability of separable (unentangled) states for quantum metrology in noisy conditions.
18
Tipton, Denver Leonard John. "Electron correlations in quantum dots." Thesis, King's College London (University of London), 2001. https://kclpure.kcl.ac.uk/portal/en/theses/electron-correlations-in-quantum-dots(b6e1a547-fbb8-41f7-9d2b-f235b68b85be).html.
Full text
19
Norrköping, Symfoniorkestern. "Quantum correlations in various systems." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411371.
Full text
20
Stratton, B. "Aspects of structure-reactivity correlations." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382852.
Full text
21
Thirukkonda, Sreeram (Sreeram Radhakrishnan) 1975. "Correlations in firm default behavior." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55245.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 67-68).<br>Modeling credit risk using Structural and Reduced Form models has been a popular and apropos topic of research. This work makes an attempt to better understand correlations in firm default. A review of contemporary research reveals several models with varying degrees of assumptions around firm default and how they relate to macroeconomic variables. More recent literature also makes use of a doubly stochastic assumption which in essence holds that given a certain path of covariates the default probabilities of two similar firms is independent. We explore empirical evidence which points to correlated defaults conditional on various explanatory covariates. Given the strong similarities in underlying firm structure and relationship to macro-economic environment, it can be hypothesized that there exist correlations in default behavior among similar firms.<br>by Sreeram Thirukkonda.<br>S.M.
22
Marianetti, Chris 1975. "Electronic correlations in Lix̳ CoO₂." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30120.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.<br>In title on t.p., double-underscored "x" appears as subscript.<br>Includes bibliographical references (p. 120-123).<br>The purpose of this thesis is further the understanding of the electronic properties of LixCoO2 using density functional theory (DFT) and the dynamical mean-field theory (DMFT). Three main problems are addressed. First, the influence of hybridization among the eg and oxygen orbitals is studied using DFT and a modified Hubbard model which is solved within DMFT. It has long been known that doping holes into the t2g bands are accompanied by a rehybridization which causes electron density to be added to the eg states and hole density to the oxygen states. This so-called rehybridization mechanism has been demonstrated to be a competition between the hybridization, which prefers to occupy the eg orbitals, and the Co on-site coulomb repulsion, which prefers to have the eg orbitals empty to avoid the strong coulomb interaction. It is also shown that eg-oxygen hybridization effectively screens the low energy t2g excitations, which has implications for the low energy Hamiltonian corresponding to hydrated Nal/3CoO2. Second, the hereto anomalous first-order metal-insulator transition in LixCoO2 (0.75 < x < 0.95) is identified as a Mott transition of impurity states. DFT supercell calculations indicate that for dilute Li vacancy concentrations (ie x > 0.95), the vacancy potential binds its hole and forms an impurity state which leads to a Mott insulator. We argue that the first-order transition is due to a decomposition of the impurity band, and is perhaps the only known example of a first-order Mott transition in a doped semiconductor. Third, LiCoO2 possesses a high energy photoemission satellite which hereto could not be predicted by any first-principles method. LDA+DMFT solved within multi-band iterated perturbation theory successfully predicts the satellite.<br>by Chris A. Marianetti.<br>Ph.D.
23
Ainsley, Anne Elizabeth. "Interplot correlations in variety trials." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/13828.
Full text
24
Cheong, Pak Leng. "Genotype-Phenotype Correlations in Porphyria." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13647.
Full textAbstract:
The porphyrias are a group of disorder resulting from defects in the haem biosynthesis pathway. The majority of defects are genetic in origin. The clinical penetrance of porphyria is variable and cannot be explained by environmental factors alone. It is therefore likely that genetic modifiers are present to influence the phenotypic outcome of the disease. In the first part of this study, variants in ABCB6, a member of the ATP-Binding Cassette transporter, were detected in a high proportion (62.5%) of severely affected porphyria patients. In vitro functional studies revealed that these ABCB6 variants either affect dimer formation (p.Arg276Trp, p.Thr521Ser, p.Gly588Ser and p.Ala681Thr), or has decreased ATPase activity (p.Ala492Thr). In a double knock out mouse model deficiency in Fech (Fechm1Pas) and Abcb6 showed a more severe phenotype compared to Fechm1Pas-only mice. The results support that ABCB6 acts as a genetic modifier for porphyria patients. In the second part of this study, detailed study on a patient with fatal liver failure secondary to erythropoietic protoporphyria (EPP) revealed an atypical low expression FECH allele and a maternally inherited FECH p.Phe260Leu mutation giving rise to the EPP. Exome sequencing of this EPP patient and her parents revealed multiple functional variants and a novel 0.79Mb duplication, all involving genes in the bile secretion pathway. These variants affect both the basolateral re-uptake and canalicular secretion of bile acids as well as their constitution. In EPP, the excessive haem intermediate protoporphyrin IX is excreted in bile. The results here suggest that genetic variants in the bile secretion pathway may contribute to the risk of liver failure in EPP patients.
25
Ibnouhsein, Mohamed Issam. "Quantum correlations and causal structures." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112426/document.
Full textAbstract:
Les travaux récents en fondements de la théorie quantique (des champs) et en information quantique relativiste tentent de mieux comprendre les effets des contraintes de causalité imposées aux opérations physiques sur la structure des corrélations quantiques. Le premier chapitre de cette thèse est consacré à l'étude des implications conceptuelles de la non-localité quantique, notion qui englobe celle d'intrication dans un sens précis. Nous détaillons comment les récentes approches informationnelles tentent de saisir la structure des corrélations non-locales, ainsi que les questions que ces dernières soulèvent concernant la capacité d'un observateur localisé à isoler un système de son environnement. Le second chapitre détaille les effets de l'invariance de Poincaré sur la détection et la quantification de l'intrication. Cette invariance impose que tous les systèmes soient modélisés en dernière instance dans le cadre de la théorie des champs, ce qui implique qu'aucun système à énergie finie ne puisse être localisé, ainsi que la divergence de toute mesure d'intrication pour des observateurs localisés. Nous fournissons une solution à ces deux problèmes en démontrant l'équivalence générique qui existe entre une résolution spatiale finie des appareils de mesure et l'exclusion des degrés de liberté de haute énergie de la définition du système observé. Cette équivalence permet une interprétation épistémique du formalisme quantique standard décrivant les systèmes localisés non-relativistes et leurs corrélations, clarifiant ainsi l'origine des mesures finies d'intrication pour de tels systèmes. Le dernier chapitre explore un cadre théorique récemment introduit qui prédit l'existence de corrélations quantiques sans ordre causal défini. Procédant par analogie avec le cas des corrélations non-locales, nous présentons quelques principes informationnels contraignant la structure de ces corrélations dans le but de mieux en comprendre l'origine physique<br>Recent works in foundations of quantum (field) theory and relativistic quantum information try to better grasp the interplay between the structure of quantum correlations and the constraints imposed by causality on physical operations. Chapter 1 is dedicated to the study of the conceptual implications of quantum nonlocality, a concept that subsumes that of entanglement in a certain way. We detail the recent information-theoretic approaches to understanding the structure of nonlocal correlations, and the issues the latter raise concerning the ability of local observers to isolate a system from its environment. Chapter 2 reviews in what sense imposing Poincaré invariance affects entanglement detection and quantification procedures. This invariance ultimately forces a description of all quantum systems within the framework of quantum field theory, which leads to the impossibility of localized finite-energy states and to the divergence of all entanglement measures for local observers. We provide a solution to these two problems by showing that there exists a generic equivalence between a finite spatial resolution of the measurement apparatus and the exclusion of high-energy degrees of freedom from the definition of the observed system. This equivalence allows for an epistemic interpretation of the standard quantum formalism describing nonrelativistic localized systems and their correlations, hence a clarification of the origin of the finite measures of entanglement between such systems. Chapter 3 presents a recent theoretical framework that predicts the existence of correlations with indefinite causal order. In analogy to the information-theoretic approaches to nonlocal correlations, we introduce some principles that constrain the structure of such correlations, which is a first step toward a clear understanding of their physical origin
26
Rabenseifner, Adrian. "Oblivious transfer from non-local correlations." Zurich : ETH, Swiss Federal Institute of Technology Zurich, Department of Computer Science, Group of Quantum Information, 2009. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=446.
Full text
27
Guerini, de Souza Leonardo. "Simulating quantum measurements and quantum correlations." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/482108.
Full textAbstract:
This PhD thesis is focused on the quantum measurement simulability problem, that is, deciding whether a given measurement can be simulated when only a restricted subset of measurements is accessible. We provide an operational framework for this problem based on classical manipulations over the set of simulators. Particular cases of interest are further investigated, in which the simulators are taken to be projective measurements, measurements of a fixed number of outcomes, and arbitrary sets of fixed cardinality. In each of these situations we derive either necessary or sufficient conditions for simulability, and full characterisations in terms of semidefinite programming for some specific cases. Since joint measurability is a particular case of simulability, we also present a natural generalisation for it.
Besides deciding whether a given measurement is simulable by some set of simulators, we also pose the question of what are the most robust measurements against simulability. We provide a strategy for approximating the set of quantum measurements based on relaxing the positivity constraint. This allows us to identify the most robust qubit measurement in terms of projective
simulability, as well as the most incompatible sets of N measurements, for N = 1, . . . , 5, which notably are found to be always projective.
By applying our simulability results in the context of Einstein-Podolsky-Rosen steering and Bell nonlocality we are able to construct improved and more general local models. Starting from models for a finite number of measurements we obtain the first general method for constructing local models for arbitrary families of quantum states. Similarly, our study on projective simulability
yields a strategy for extending models for projective measurements to arbitrary ones, culminating in the most efficient local model for two-qubit Werner states and general measurements<br>Esta tese de doutorado é centrada no problema de simulação de medições quânticas, ou seja, em decidir se uma dada medição pode ser simulada quando temos acesso a apenas um subconjunto restrito de medições. Apresentamos um framework operacional para esse problema, baseado em manipulações clássicas sobre o conjunto de simuladores. Casos particulares de interesse são estudados em detalhe, nos quais o conjunto de simuladores é dado por medições projetivas, medições de um número fixo de outcomes, e conjuntos arbitrários
de cardinalidade fixada. Em cada uma dessas situações, derivamos condições necessárias ou suficientes para simulabilidade, e uma caracterização completa em termos de programação semidefinida em alguns casos específicos. Como comensurabilidade é um caso particular de simulabilidade, apresentamos também uma generalização natural para esse conceito.
Além de decidir se uma dada medição é simulável ou não, também exploramos a questão de quais são as medições mais robustas contra simulabilidade.
Apresentamos então uma estratégia para aproximar o conjunto das medições quânticas baseada em uma relaxação da condição de positividade. Isso nos permite identificar a medição mais robusta contra simulabilidade projetiva em dimensão 2, assim como os conjuntos de N medições mais incompatíveis, para N = 1, . . . , 5, que notavelmente se revelam ser projetivas em todos esses casos.
Aplicando nossos resultados de simulabilidade no contexto de Einstein-Podolsky-Rosen steering e não-localidade de Bell, somos capazes de construir modelos locais melhores e mais gerais. Partindo de modelos para um número finito de medições, obtemos o primeiro método geral para construção de modelos locais para famílias arbitrárias de estados quânticos. De forma similar, nosso estudo de simulabilidade projetiva fornece uma estratégia para estender modelos locais para medições projetivas a medições arbitrárias, culminando no mais eficiente modelo local para estados de Werner de dois qubits e medições quaisquer<br>Aquesta tesi doctoral se centra en el problema de la simulació de mesures quàntiques, és a dir, en decidir si es pot simular una determinada mesura quan només tenim accés a un subconjunt restringit de mesures diferents. Presentem un marc operacional per a aquest problema, basat en manipulacions clàssiques sobre el conjunt de simuladors. Casos particulars d’interès son estudiat en detall, on el conjunt de simuladors està donat per mesures projectius, mesures d’un nombre fix de resultats i conjunts arbitraris de cardinalitat fixa.
En cadascuna d’aquestes situacions, derivem condicions necessaris o suficients per a la simulació, i una caracterització completa en termes de programació semi-definida en alguns casos específics. Com la mensurabilitat conjunta és un cas particular de simulació, presentem també una generalització natural per a aquest concepte.
A més de decidir si un mesura és simulable o no, també exploram la qüestió de quines son las mesures més robustes contra la simulabilitat. A continuació, presentem una estratègia per aproximar el conjunt de mesures quàntiques basat en una relaxació de la condició de positivitat. Això permet la identificació de la mesura més robusta envers la simulació projectiva en dimensió 2, així com els conjunts més incompatibles de N mesures, per N = 1, . . . , 5, que notablement resulten ser projectivas en tots aquests casos.
Aplicant els nostres resultats de simulació en el context d’Einstein-Podolsky-Rosen steering i no-localitat de Bell, som capaços de construir models locals millors i més generals. A partir de models per a un nombre finit de mesures, obtenim el primer mètode general per a la construcció de models locals per a famílies arbitràries d’estats quàntics. De la mateixa manera, el nostre estudi de la simulació projectiva proporciona una estratégia per ampliar models locals per a mesures projectivas a mesures arbitraris, culminant en el model local més eficient per als estats de Werner de dos qubits i mesures generals
28
Kidun, Oleg. "Investigation of electronic correlations in nanostructures." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=972491562.
Full text
29
Hogan, Patrick. "Correlations in geometrically frustrated spin systems." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491535.
Full textAbstract:
In this thesis we study the quantum and statistical mechanics of geometrically frustrated antiferromagnets. In particular, we develop a novel, general approach for studying the disordered phases of systems comprised of vertex-sharing fully frustrated spin clusters, in which every pair of spins is coupled equally by antiferromagnetic Heisenberg interactions. The novel feature of our approach is the use of conjugate Hubbard-Stratonovich fields associated with each fully frustrated cluster of spins, rather than with the spin sites themselves, to decouple all the individual spin-spin exchange interactions in the system. The individual spins in the system may then be integrated out, leaving behind a conjugate lattice of conjugate fields, coupled to each other through the spin-sites that were common to neighbouring clusters. By investigating the behaviour of these remaining conjugate fields, we may probe the properties and behaviour of the original system, and we hope this novel approach will provide a framework for a better theoretical understanding of such frustrated systems. One of the key strengths of our conjugate-field approach is the ability to make controlled, accurate approximations about the ground state in geometrically frustrated systems which support large low-temperature spin fluctuations, due to the presence of a barrierless, massively degenerate ground-state manifold. This is possible as our Hubbard-Stratonovich fields are conjugate to our spins, and so have correspondingly only small fluctuations about their ground-state. We first introduce our conjugate-field approach by studying the quantum mechanics of a single fully frustrated cluster of spins, for which we recover an exact expression for the finite-temperature partition function as a finite sum of single integrals. Extending our approach to treat more complex frustrated systems of coupled clusters, we find that the clusters are decoupled by different conjugate fields which have partial correlations. This complicates the implementation of our approach considerably, and the remainder of the thesis focuses on how we may make controlled approximations to recover correlation functions in such systems in both the classical and quantum limits.
30
Guimarães, Dias Ricardo Assis. "Anomalous correlations in low dimensional metals." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/251598.
Full textAbstract:
Dimensionality is a determinant factor in the behaviour of interacting electron systems. The cuprates and the organic superconductors are examples of systems of reduced dimensionality with anomalous normal state correlations. This thesis presents a study of one and two-particle correlations, namely, the single particle spectral function and the pair propagator, for electron systems with low dimensionality. The single particle spectral function is probed by angle resolved photoemission experiments. Theories of photoemission are presented. One dimensional metals belong to the Luttinger liquid universality class, sharing the low energy properties of the Luttinger Model. A study of the spectral and Green's functions of this model is given. The spectral functions reflect the Fermi liquid breakdown due to the anomalous correlations and spin-charge separation which are typical of this model. The upper critical field <I>H</I><SUB>c2</SUB> of a type-II superconductor is a probe of anomalous normal state pair correlations. We study the weak coupling superconducting instability equation for a simple quasi-one dimensional system, the two-dimensional highly anisotropic tight-binding model for each typical filling. The magnetic field in conjunction with the underlying lattice induces a dimensional crossover which leads to divergent mean field <I>H</I><SUB>c2</SUB> curves in the strong anisotropy limit. We study the suppression of the mean field superconducting instability of a clean weak coupling BCS superconductor in a finite magnetic field at a 2D van-Hove singularity. The absence of a velocity scale is shown to lead a spectacular deviation from the Fermi liquid BCS result, such as upward curvature and a strong enhancement of the upper critical field relative to <I>T</I><SUB>c</SUB>, <I>H</I><SUB>c2</SUB>(0) <I>T</I><SUB>c</SUB><SUP>√2</SUP> in contrast with the conventional BCS scaling <I>H</I><SUB>c2</SUB>(0) <I>T</I><SUB>c</SUB><SUP>2</SUP>. The consequences for the superconducting transition of a Luttinger liquid-like spin-charge separated normal state are explored. We show that spin-charge separation leads to an enhancement of the superconducting critical temperature compared with the conventional BCS result. The spatial decay of the pair propagator is shown to contain a logarithmic correction relative to the free Fermi gas result in a finite interval between the spin and charge thermal lengths which leads to deviations from the usual BCS parabolic-like <I>H</I><SUB>c2</SUB> behaviour.
31
Burke, Georgina. "Genotype - phenotype correlations in congenital myasthenia." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437178.
Full text
32
Nunnenkamp, Andreas. "Strong correlations in ultracold atomic gases." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:6e09e9d3-f5cd-4580-a667-6599203162e2.
Full textAbstract:
In this thesis we investigate strongly-correlated states of ultracold bosonic atoms in rotating ring lattices and arrays of double-well potentials. In the first part of the thesis, we study the tunneling dynamics of ultracold bosons in double-well potentials. In the non-interacting limit single-particle transitions dominate, while in the interaction-dominated regime correlated tunneling of all particles prevails. At intermediate times of the many-particle flopping process correlated states occur, but the timescales of these processes increase dramatically with the number of particles. Using an array of double-well potentials, a large number of such few-particle superposition states can be produced in parallel. In the second part of the thesis, we study the effects of rotation on ultracold bosons confined to one-dimensional ring lattices. We find that at commensurate filling there exists a critical rotation frequency, at which the ground state of the weakly-interacting gas is fragmented into a macroscopic superposition of different quasi-momentum states. We demonstrate that the generation of such superposition states using slightly non-uniform ring lattices has several practical advantages. Moreover, we show that different quasi-momentum states can be distinguished in time-of-flight absorption imaging and propose to probe correlations via the many-body oscillations induced by a sudden change in the rotation frequency. Finally, we compare these macroscopic superposition states to those occurring in superconducting quantum interference devices. In the third part of the thesis, we demonstrate the creation of entangled states with ultracold bosonic atoms by dynamical manipulation of the shape of the lattice potential. To this end, we consider an optical superlattice that allows both the splitting of each site into a double-well potential and the variation of the height of the potential barrier between the sites. We show how to use this array of double-well potentials to perform entangling operations between neighboring qubits encoded on the Zeeman levels of the atoms. As one possible application, we present a method of realizing a resource state for measurement-based quantum computation via Bell-pair measurements. In the final part of the thesis, we study ultracold bosons on a two-dimensional square lattice in the presence of an effective magnetic field and point out a couple of features this system has in common with ultracold bosons in one-dimensional rotating ring lattices.
33
Collins, Jeremy Charles. "Grammaticalization and Greenberg's word order correlations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50534130.
Full textAbstract:
Word order universals constitute a well-known problem in language typology, first outlined in Greenberg (1963). It has been firmly established in databases of over 1500 languages that languages with verb-object ordering are very likely to have prepositions and noun-genitive ordering, while languages with object-verb ordering are very likely to have postpositions and genitive-noun ordering (Dryer and Haspelmath 2011). This thesis attempts to give a historical explanation for these facts in terms of the origin of syntactic categories: adpositions have historically developed from nouns and verbs (Givon 1984, Aristar 1991); and verbs often develop from nominalizations used with a genitive object. These types of grammaticalization can explain why adpositions retain the ordering of their source nouns or verbs, and why verb/object ordering often parallels noun/genitive ordering.
This historical explanation is elaborated on, with data from different language families. Examples of verbs grammaticalizing from nominalizations used with genitive objects are given, drawing on historical work such as Salanova (2007) on Brazilian Jê languages and Starosta, Pawley and Reid (1982) on Austronesian. Different languages show varying degrees of 'nominalism', the morphosyntactic resemblance between verb forms and noun phrases/nominalizations. Other languages show a less developed distinction between adpositions and verbs/nouns. These examples of gradience in syntactic categories are argued to be behind resemblances in word orderings. Language contact is responsible for preserving word order types, when languages undergo change in more than one word order (e.g. Greenberg 1969); and the difference in rates of word order change across constructions is argued to be behind hierarchies such as Hawkins (1983)'s Prepositional Noun Modifier Hierarchy. This explanation of word order universals contrasts with more mainstream accounts such as Hawkins (1994) in terms of processing efficiency, and Kirby and Christiansen (2003) in terms of learnability. While these explanations are perhaps compatible with the historical explanation, they are argued to be redundant; grammaticalization arguably is not driven or constrained by learnability and processing efficiency, with memetics, 'typological poise' (Enfield 2003) and language contact given as alternatives. Instead of reflecting functional biases, word order patterns are argued to reflect language history, both the history of language contact, and the history of syntactic categories developing through grammaticalization.<br>published_or_final_version<br>Linguistics<br>Master<br>Master of Philosophy
34
Lyamzin, Dmitry. "Correlations in populations of sensory neurons." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-176398.
Full text
35
Lang, Guillaume. "Correlations in low-dimensional quantum gases." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY076/document.
Full textAbstract:
Les gaz d'atomes utlra-froids sont adaptés pour simuler des phénomènes observés en physique de la matière condensée, de part le haut degré d'ajustabilité de l'ensemble des paramètres avec une précision exceptionnelle.En particulier, la réalisation de pièges hautement anisotropes permet de confiner ces gaz en basse dimension, où le rôle des fluctuations quantiques est accru.Je m'attache en particulier au modèle de gaz de Bose unidimensionel dont les atomes interagissent localement, connu sous le nom de modèle de Lieb et Liniger. Les outils théoriques que j'emploie sont l'Ansatz de Bethe, la théorie conforme des champs, le formalisme des liquides de Tomonaga-Luttinger, ainsi qu'une équivalence exacte entre bosons et fermions.Ces méthodes exactes ou d'approximation me donnent accès, avec une précision remarquable, à la thermodynamique de l'état fondamental, au spectre d'excitations et aux fonctions de corrélation, depuis les corrélations locales à k corps jusqu'à la distribution en impulsion, ainsi qu'au facteur de structure dynamique. Ces observables fournissent des informations concernant les propriétés de cohérence et de superfluidité du gaz. Plus particulièrement, en me servant de la théorie de la réponse linéaire, j'étudie la force de traînée exercée par un faisceau laser gaussien remué dans le gaz.Enfin, je considère la situation où, en relâchant un degré de contrainte dû au piège, une structure à plusieurs modes apparaît et conduit à une augmentation progressive de la dimension effective du système. Tout du long, j'étudie l'effet d'un piège harmonique dans la dimension principale à travers le formalisme de l'Approximation de Densité Locale<br>Ultracold atom gases are a versatile platform to simulate condensed matter physics phenomena, as virtually any parameter is experimentally tunable with a high accuracy.In particular, highly anisotropic traps allow the realization of low-dimensional systems, where the role of quantum fluctuations is enhanced. I investigate the paradigmatic model of a one-dimensional Bose gas with contact interactions, a.k.a the Lieb-Liniger model, using powerful analytical tools such as Bethe Ansatz, Conformal Field Theory and the Tomonaga-Luttinger liquid formalism, as well as the Bose-Fermi mapping.These exact and approximate methods allow me to investigate with high accuracy its Ground-State energy and thermodynamics, excitation spectra and correlation functions, from the k-body local correlations to the momentum distribution and the dynamical structure factor. These quantities yield useful informations on the coherence and superfluidity of a gas. In particular, I study the drag force exerted by a gaussian laser beam stirred into the gas in linear response theory.Then, releasing a transverse trapping, I study the appearance of a multimode structure and the dimensional crossover. All along, the effect of a harmonic trap in the longitudinal direction is studied within the Local Density Approximation
36
FIELDS, PATRICK-PIERRE. "Correlations radio-serologiques des polyarthrites rhumatoides." Aix-Marseille 2, 1988. http://www.theses.fr/1988AIX20491.
Full text
37
Schneider, William. "Strong Correlations in Ultracold Fermi Gases." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316447449.
Full text
38
Brézin, Antoine P. "Glaucome chronique : genetique et correlations cliniques." Paris 7, 2001. http://www.theses.fr/2001PA077064.
Full textAbstract:
Le glaucome primitif a angle ouvert (gpao), deuxieme cause de handicap visuel irreversible dans les pays riches, entraine une neuropathie optique progressive. La maladie est asymptomatique avant ses stades avances. Le principal facteur de risque de gpao est l'elevation de la pression intraoculaire (pio). Lorsque le glaucome est depiste a temps, des traitements hypotonisants oculaires peuvent prevenir la progression des deficits fonctionnels visuels. Situe en 1q21-31 au locus glc1a, tigr / myoc (trabecular meshwork-inducible glucocorticoid response / myociline) a ete le premier gene identifie associe au glaucome. Nos travaux ont compare les phenotypes de formes familiales de glaucome liees ou non liees a glc1a. Un pronostic significativement plus severe etait observe en cas de liaison a glc1a. Dans ces formes, la mediane de debut de la maladie etait inferieure a 40 ans et les pio maximales etaient elevees (en moyenne > 35 mmhg). Dans les formes non liees a glc1a, les phenotypes etaient plus heterogenes, avec coexistence de cas de gpao et d'hypertonies oculaires non compliquees. Secondairement, l'identification de mutations de myoc, toutes situees dans le domaine olfactomedine de la proteine, a confirme les etudes de liaison. Une heterogeneite des phenotypes etait correlee aux types de mutations detectees. La mediane de l'age de diagnostic de la maladie variait de 10 ans pour la mutation pro370leu a 35 ans pour la mutation asn480lys. Nos etudes ont egalement mis en evidence un effet fondateur, responsable de nombreux cas de glaucomes chez des sujets originaires du nord de la france. Au locus glc1a un haplotype commun etait mis en evidence chez 71 patients presentant la mutation asn480lys de myoc. Une heterogeneite phenotypique etait notee chez les patients de cette famille, l'age de diagnostic variant de 10 ans a plus de 60 ans. Un suivi prospectif est en cours chez 24 porteurs sains de mutations myoc, ayant beneficie d'un diagnostic predictif de glaucome.
39
Zhang, Zhihong. "Feature selection from higher order correlations." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3340/.
Full textAbstract:
This thesis addresses the problems in feature selection, particularly focusing on selecting features from higher order correlations. To this end, we present two supervised feature selection approaches named \emph{Graph based Information-theoretic Feature Selection} and \emph{Hypergraph based Information-theoretic Feature Selection} respectively, which are capable of considering third or even higher order dependencies between the relevant features and capturing the optimal size of relevant feature subset. Furthermore, we develop two unsupervised feature selection methods which can evaluate features jointly rather than individually. In this case, larger feature combinations are considered. The reason for this is that although an individual feature may have limited relevance to a particular class, when taken in combination with other features it may be strongly relevant to the class. In Chapter $2$, we thoroughly review the relevant literature of the classifier independent (filter-based) feature selection methods. One dominant direction of research in this area is exemplified by the so-called information theoretic feature selection criteria, which is measuring the mutual dependence of two variables. Another influential direction is the graph-based feature selection methods, which are to select the features that best preserve the data similarity or a manifold structure derived from the entire feature set. We notice that most existing feature selection methods evaluate features individually or just simply consider pairwise feature interaction, and hence cannot handle redundant features. Another shortcoming of existing feature selection methods is that most of them select features in a greedy way and do not provide a direct measure to judge whether to add additional features or not. To deal with this problem, they require a user to supply the number of selected features in advance. However, in real applications, it is hard to estimate the number of useful features before the feature selection process. This thesis addresses these weaknesses, and fills a gap in the literature of selecting features from higher order correlations. In Chapter $3$ we propose a graph based information-theoretic approach to feature selection. There are three novel ingredients. First, by incorporating mutual information (MI) for pairwise feature similarity measure, we establish a novel feature graph framework which is used for characterizing the informativeness between the pair of features. Secondly, we locate the relevant feature subset (RFS) from the feature graph by maximizing features' average pairwise relevance. The RFS is expected to have little redundancy and very strong discriminating power. This strategy reduces the optimal search space from the original feature set to the relatively smaller relevant feature subset, and thus enable an efficient computation. Finally, based on RFS, we evaluate the importance of unselected features by using a new information theoretic criterion referred to as the multidimensional interaction information (MII). The advantage of MII is that it can go beyond pairwise interaction and consider third or higher order feature interactions. As a result, we can evaluate features jointly, and thus avoid the redundancies arising in individual feature combinations. Experimental results demonstrate the effectiveness of our feature selection method on a number of standard data-sets. In Chapter $4$, we find that in some situations the graph representation for relational patterns can lead to substantial loss of information. This is because in real-world problems objects and their features tend to exhibit multiple relationships rather than simple pairwise ones. This motive us to establish a feature hypergraph (rather than feature graph) to characterize the multiple relationships among features. We draw on recent work on hyper-graph clustering to select the most informative feature subset (mIFS) from a set of objects using high-order (rather than pairwise) similarities. There are two novel ingredients. First, we use MII to measure the significance of different feature combinations with respect to the class labels. Secondly, we use hypergraph clustering to select the most informative feature subset (mIFS), which has both low redundancy and strong discriminating power. The advantage of MII is that it incorporates third or higher order feature interactions. Hypergraph clustering, which extracts the most informative features. The size of the most informative feature subset (mIFS) is determined automatically. Experimental results demonstrate the effectiveness of our feature selection method on a number of standard data-sets. In addition to the supervised feature selection methods, we present two novel unsupervised feature selection methods in Chapter $5$ and Chapter $6$. Specifically, we propose a new two-step spectral regression technique for unsupervised feature selection in Chapter $5$. In the first step, we use kernel entropy component analysis (kECA) to transform the data into a lower-dimensional space so as to improve class separation. Second, we use $\ell_{1}$-norm regularization to select the features that best align with the data embedding resulting from kECA. The advantage of kECA is that dimensionality reducing data transformation maximally preserves entropy estimates for the input data whilst also best preserving the cluster structure of the data. Using $\ell_{1}$-norm regularization, we cast feature discriminant analysis into a regression framework which accommodates the correlations among features. As a result, we can evaluate joint feature combinations, rather than being confined to consider them individually. Experimental results demonstrate the effectiveness of our feature selection method on a number of standard face data-sets. In Chapter $6$, by incorporating MII for higher order similarities measure, we establish a novel hypergraph framework which is used for characterizing the multiple relationships within a set of samples (e.g. face samples under varying illumination conditions). Thus, the structural information latent in the data can be more effectively modeled. We then explore a strategy to select the discriminating feature subset on the basis of the hypergraph representation. The strategy is based on an unsupervised method which derive the hypergraph embedding view of feature selection. We develop the strategy based on a number of standard image datasets, and the results demonstrate the effectiveness of our feature selection method. We summarize the contributions of this thesis in Chapter $7$, and analyze the developed methods. Finally, we give some suggestions to the future work in feature selection.
40
Bennet, Adam Joseph. "Optical Experiments on Shared Quantum Correlations." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/365930.
Full textAbstract:
Shared quantum correlations find application in a wide range of modern quantum information protocols. This thesis presents several optical experiments towards the improved certification of shared quantum correlations, using photonic qubits.
The first experiment demonstrates the Einstein–Podolsky–Rosen (EPR) steering effect with no detection loophole. Polarisation–entangled photon pairs generated in a Sagnac interferometer were used to test new loss–tolerant EPR steering inequalities. To test the robustness of the loss–tolerant EPR steering nequalities, a transmission loss of −4.3dB was introduced using a 1km optical fibre loop, finding inequality violations for n = 10 and n = 16 measurement settings with no detection loophole (equating to a total loss of
87%). The findings demonstrate how the new loss–tolerant protocols can be used to certify the EPR steering effect for arbitrarily high losses, and may find application in one–sided device–independent quantum key distribution protocols.
The second experiment introduces EPR steering in the context of an EPR steering game. The rules of the game allow for certification of shared quantum correlations via EPR steering inequalites without requiring trust in devices or parties external to a quantum referee. In particular, the experiment successfully demonstrates EPR steering in a measurement–device independent framework; a framework which has typically been accessible only through Bell inequality violations. The findings suggest the possibility for quantum–refereed one–sided device–independent quantum key distribution protocols.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Biomolecular and Physical Sciences<br>Science, Environment, Engineering and Technology<br>Full Text
41
Wolstenhulme, Richard. "Three-point phase correlations in cosmology." Thesis, University of Cambridge, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.762062.
Full text
42
Chrzanowski, Helen Mary. "Extracting quantum correlations from gaussian states." Phd thesis, Canberra, ACT : The Australian National University, 2014. http://hdl.handle.net/1885/14511.
Full textAbstract:
The Gaussian toolbox of the continuous variables provides for deterministic, high-efficiency operations with non-classical states. Its very Gaussian nature, however, restricts its reach for quantum information and communication applications. This thesis comprises three experimental works, which seek to examine the strengths of this toolbox and address some of its weaknesses. The measurement-based non-linearity of a conditional photon-counting measurement can be used to de-Gaussify' a Gaussian state of light. Here, we propose a continuous variable analog of just such a 'heralding' measurement, replacing a non-deterministic photon-counting measurement with a deterministic measurement of the field quadratures. Such a technique cannot be used to prepare a non-Gaussian state, but it can, on average, yield the same non-Gaussian statistics. We demonstrate this technique by reconstructing the statistics of non-Gaussian photon-subtracted squeezed vacuum states. We then consider the problem of noiseless linear amplification. We experimentally demonstrate that in certain scenarios, the requirement for a physical noiseless linear amplifier can be exchanged for a straightforward post-selection of the measurement record. We apply our 'virtual' noiseless amplifier to entanglement degraded by transmission loss of up to the equivalent of 100km of optical fibre. We extract an effective entangled resource stronger than even that achievable with a maximally entangled resource passively transmitted through the same channel. We also provide a proof-of-principle demonstration of the value of the measurement-based noiseless linear amplifier for quantum key distribution, extracting a secret key from an otherwise insecure regime. Lastly, we turn to the recently popularised measure of all quantum correlations: quantum discord. Quantum discord has emerged as a measure of quantum correlations beyond entanglement, with significant ramifications for our understanding of Gaussian states. Here, we introduce a simple protocol that yields an operational interpretation of quantum discord: that discord describes information only accessible via coherent interactions. We first experimentally encode information within the discordant correlations of two separable Gaussian states. The amount of extra information recovered by coherent interactions is directly linked to the discord of the original state.
43
RICCARDI, ALBERTO. "UNCERTAINTY RELATIONS, QUANTUM CORRELATIONS AND APPLICATIONS." Doctoral thesis, Università degli studi di Pavia, 2020. http://hdl.handle.net/11571/1317091.
Full text
44
Abedinpour, Harzand Saeed. "Correlations in low-dimensional electron liquids." Doctoral thesis, Scuola Normale Superiore, 2007. http://hdl.handle.net/11384/85852.
Full text
45
AVRIL, GEORGES-ANTOINE. "Plaques d'endarteriectomie carotidienne : correlations anatomo-cliniques." Nice, 1989. http://www.theses.fr/1989NICE6022.
Full text
46
Simon, Florian. "Band quantum geometry and electronic correlations." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP151.
Full textAbstract:
Deux des piliers actuels de la matière condensée sont d'une part la matière corrélée et d'autre part la matière topologique, avec la géométrie quantique comme sous-jaçent. La physique des matériaux corrélés, en tant que domaine de recherche, a pris forme vers le milieu du 20ème siècle avec la découverte des isolants de Mott et de l'effet Kondo. Le domaine des matiériaux topologiques a quant à lui ses origines dans les années 1980 avec l'effet Hall quantique entier, et a globalement pris forme dans les années 2000. La géométrie quantique, qui sous-tend la topologie, repose sur la théorie des bandes, qui décrit les matériaux en termes d'excitations élémentaires. Les domaines de la matière topologique et de la matière corrélée sont donc très différents, et se sont développés séparément. Un effort de recherche est en cours pour rapprocher ces deux domaines, et cette thèse en fait partie. En effet, dans cette thèse nous explorons des exemples de relations entre la géométrie quantique venant de la théorie des bandes et les interactions électroniques. Dans la première partie de cette thèse, nous passons en revue les fondements de la théorie des bandes ainsi que de ses extensions géométrique et topologique. Nous faisons ceci afin de soutenir que les excitations élémentaires décrites par la théorie des bandes sont des quasiparticules, appelées fermions de Bloch, dont le charactère émergent leur confère des propriétés que n'ont pas les électrons élémentaires. Un exemple notable est la géométrie quantique. Nous soutenons que cette dernière quantifie la non-localité du fermion de Bloch, qui elle-même provient des transitions interbandes virtuelle. Nous présentons de plus les fondements de la théorie BCS ainsi que des fonctions de Green. Motivés par l'éventuelle différence entre des paires de Cooper formées par des fermions de Bloch et par des électrons, la seconde partie de la thèse est dévouée à la relation entre la géométrie quantique de l'état normal et l'état supraconducteur. Nous trouvons que cette relation est ambivalente, et qu'elle peut largement être comprise en invoquant la non-localité des fermions de Bloch. D'une part, cette non-localité engendre un supercourant piloté par les mouvements de point-zéro. D'autre part, cette même non-localité affaiblit l'interaction d'appariement du fait d'un terme de Darwin émergent. Dernièrement, dans la troisième partie du manuscript nous explorons la relation entre la géométrie quantique, la topologie et les fonctions de Green. Nous montrons que dans les systèmes sans interactions les propriétés analytiques de la fonction de Green peuvent être mises à profit pour extraire les invariants topologiques ℤ₂. Nous terminons en proposant une généralisation de la géométrie quantique au-delà de la limite des fermions libres en utilisant la fonction de Green<br>Two pillars of contemporary condensed matter physics research are correlated matter and topological matter, with its underlier quantum geometry. The physics of materials whose properties are governed electronic correlations as a research domain has taken shape around the midth of the 20th century with the discovery of Mott insulators and the Kondo effect. In contrast, the field of topological matter is more recent as it originated from the integer quantum Hall effect in the 1980s, and has largely taken shape in the 2000s. Quantum geometry relies on band theory, which describes materials in terms of single-particle excitations. The fields of topological matter and correlated matter are thus significantly different fields that have mostly evolved separately. A contemporary research effort is underway to bring these two pillars of condensed matter physics closer. As part of that effort, this PhD thesis explores interplays between quantum geometry and electronic interactions. In the first part of the manuscript, we extensively review the foundations of band theory and its geometrical and topological extensions. We do so to argue that the single-particle excitations described by band theory are quasiparticles, dubbed Bloch fermions, whose emergence endows them with properties not shared with elementary electrons, one notable example being quantum geometry. We argue that the latter quantifies the non-locality of the Bloch fermion that arises from virtual interband transitions. We additionally discuss the fundamentals of BCS theory and of Green's functions. Motivated by the apparent difference between Cooper pairs formed by Bloch fermions and by elementary electrons, the second part of the manuscript is devoted to the study of the relation between the normal state quantum geometry and the superconducting state. Our findings show that this relation is ambivalent, and can largely be understood using the non-locality argument. On one hand, the non-locality of the Bloch fermions allows for zero-point motion-driven supertransport. On the other hand, their non-locality weakens the pairing interaction through an emergent Darwin term. Lastly, in the third part of the manuscript we investigate interplays between quantum geometry, topology and Green functions. We show that in non-interacting systems the analytic properties of the Green's function can be used to extract the value of ℤ₂ topological invariants. Finally, we propose a generalization of quantum geometry beyond the free-fermion limit using Green functions
47
Thomsen, Laura Kathrine Wehde, and n/a. "Using Quantum Feedback to Control Nonclassical Correlations in Light and Atoms." Griffith University. School of Science, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040406.124012.
Full textAbstract:
This thesis considers two types of applications of quantum feedback control; feedback creation of
nonclassical states of light, and controlling nonclassical properties of an ensemble of atoms. An electro-optical feedback loop will create an in-loop field with nonclassical photon statistics similar to squeezed light, resulting in fluorescence line-narrowing of a two-level atom coupled to such light. We extend this theory to study a three-level atom coupled to broadband squashed light, and confirm the two-level atom line-narrowing using a more realistic non-Markovian description of the feedback loop. The second type of application utilizes continuous QND measurement of atomic ensembles. If we measure the collective spin, then the system experiences conditional spin squeezing dependent on the measurement results. We show that feedback based on these results can continuously drive the system into the same conditioned state, resulting in deterministically reproducible spin squeezing. If we measure the atom number fluctuations of a BEC, then, due to the nonlinearity of atomic self interactions, this is also information about phase fluctuations. We show that feedback based on this information can greatly reduce the collisional broadening of the linewidth of an atom laser out-coupled from the condensate.
48
Thomsen, Laura Kathrine Wehde. "Using Quantum Feedback to Control Nonclassical Correlations in Light and Atoms." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/367297.
Full textAbstract:
This thesis considers two types of applications of quantum feedback control; feedback creation of nonclassical states of light, and controlling nonclassical properties of an ensemble of atoms. An electro-optical feedback loop will create an in-loop field with nonclassical photon statistics similar to squeezed light, resulting in fluorescence line-narrowing of a two-level atom coupled to such light. We extend this theory to study a three-level atom coupled to broadband squashed light, and confirm the two-level atom line-narrowing using a more realistic non-Markovian description of the feedback loop. The second type of application utilizes continuous QND measurement of atomic ensembles. If we measure the collective spin, then the system experiences conditional spin squeezing dependent on the measurement results. We show that feedback based on these results can continuously drive the system into the same conditioned state, resulting in deterministically reproducible spin squeezing. If we measure the atom number fluctuations of a BEC, then, due to the nonlinearity of atomic self interactions, this is also information about phase fluctuations. We show that feedback based on this information can greatly reduce the collisional broadening of the linewidth of an atom laser out-coupled from the condensate.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Science<br>Full Text
49
Thongchua, Chalita, and Wenjin Yang. "Correlations between Requirement Attributes and Process Attributes : Identifying and quantifying the correlations in a rapid software development process." Thesis, Blekinge Tekniska Högskola, Avdelningen för programvarusystem, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2206.
Full textAbstract:
It is reported that the market-driven product development is becoming common in the software industry. There are two challenges in the market-driven product development: time-to-market and meeting customers’ requirements. A rapid software development process is regarded as a good way to solve those two challenges. Streamline development process (SLDP) is aligned with a rapid software development process, which is an in-house development process of Ericsson AB. In this study, seven completed projects from the streamline development process were investigated. The correlations between requirement attributes and process attributes were identified and quantified in the SLDP. Nine hypotheses were assumed. Four hypotheses were derived from the correlations from the other software development processes, and the other five hypotheses were derived from new requirement attributes and process attributes in SLDP. Two statistical software applications were used in the hypotheses testing. The results of those hypotheses showed that too much time spent in the early phase of streamline development would not reduce the time to market. A SLDP measurement program contains the measurements of requirement attributes and process attributes. This measurement program was mainly composed of four core attributes (size, effort, schedule, and fault), the requirement volatility, the completeness, the resource overrun, and the estimation accuracy. The results of the SLDP measurement program reflected four challenges in the SLDP: the requirement engineering process, the release planning, the estimation accuracy at each development phase, and the quality of the documentation. At last, based on those four challenges (the requirement engineering process, the release planning, the estimation accuracy at each development phase, and the quality of the documentation) and the defined correlations between requirement attributes and process attributes in the SLDP, the improvement opportunities were proposed for the SLDP.
50
Nilsson, Johanna. "CORRELATIONS BETWEEN PHYSICOCHEMICAL PROPERTIES IN MATERIALS COMPRISING MICROFIBRILLATED CELLULOSE : CORRELATIONS BETWEEN PHYSICOCHEMICAL PROPERTIES IN MATERIALS COMPRISING MICROFIBRILLATED CELLULOSE." Thesis, Umeå universitet, Kemiska institutionen, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185526.
Full textAbstract:
Microfibrillated cellulose (MFC) films have gained a lot of industrial interest lately dueto their good barrier properties and good mechanical strength. In this study it wasinvestigated whether rheological characteristics and conductivity of MFC dispersionscomprised of different MFC grades could be correlated to tensile properties of the MFCfilms produced from the corresponding MFC dispersion. A rheological characterizationmethod was developed for MFC dispersions with 3 wt% MFC and a secret additiveusing a dynamic rotational rheometer and a smooth “plate to plate” geometry. Themethod consisted of an amplitude sweep, a frequency sweep, and a controlled shearrate measurement. Two predicting OPLS models were created in SIMCA: model 1correlated values from rheological measurements and ionic conductivity to tensileproperties and model 2 correlated MFC grades to tensile properties. A slight correlationbetween MFC rheology and tensile properties could be observed, but due to the lowpredictive ability of model 1 (Q2=0.47) it was deemed that the model was insufficientas a tool for facilitated predictions of new samples. It was concluded that tensileproperties are more correlated to the composition of MFC dispersions than whatrheological characteristics and ionic conductivity the dispersions display, based on thegood predictive ability of model 2 (Q2=0.59).