Дисертації: "Finite density QCD"

1

Crompton, P. R. "Lee-Yang zeros analysis of finite density lattice QCD." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368583.

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2

Hatta, Yoshitaka. "The QCD phase transition at finite temperature and density." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147809.

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3

Vuorinen, Aleksi. "The pressure of QCD at finite temperature and quark number density." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/vuorinen/.

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4

Morrison, Susan Elizabeth. "Lattice QCD at finite baryon density with an implementation of dynamical fermions." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363152.

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5

Bluhm, Marcus. "QCD equation of state of hot deconfined matter at finite baryon density : a quasiparticle perspective." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1232358506561-61975.

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Анотація:

The quasiparticle model, based on quark and gluon degrees of freedom, has been developed for the description of the thermodynamics of a hot plasma of strongly interacting matter which is of enormous relevance in astrophysics, cosmology and for relativistic heavy-ion collisions as well. In the present work, this phenomenological model is extended into the realm of imaginary chemical potential and towards including, in general, different and independent quark flavour chemical potentials. In this way, nonzero net baryon-density effects in the equation of state are self-consistently attainable. Furthermore, a chain of approximations based on formal mathematical manipulations is presented which outlines the connection of the quasiparticle model with the underlying gauge field theory of strong interactions, QCD, putting the model on firmer ground. A comparison of quasiparticle model results with available lattice QCD data for, e. g., basic bulk thermodynamic quantities and various susceptibilities such as diagonal and off-diagonal susceptibilities, which provide a rich and sensitive testing ground, is found to be successful. Furthermore, different thermodynamic quantities and the phase diagram for imaginary chemical potential are faithfully described. Thus, the applicability of the model to extrapolate the equation of state known from lattice QCD at zero baryon density to nonzero baryon densities is shown. In addition, the ability of the model to extrapolate results to the chiral limit and to asymptotically large temperatures is illustrated by confrontation with available first-principle lattice QCD results. These extrapolations demonstrate the predictive power of the model. Basing on these successful comparisons supporting the idea that the hot deconfined phase can be described in a consistent picture by dressed quark and gluon degrees of freedom, a reliable QCD equation of state is constructed and baryon-density effects are examined, also along isentropic evolutionary paths. Scaling properties of the equation of state with fundamental QCD parameters such as the number of active quark flavour degrees of freedom, the entering quark mass parameters or the numerical value of the deconfinement transition temperature are discussed, and the robustness of the equation of state in the regions of small and large energy densities is shown. Uncertainties arising in the transition region are taken into account by constructing a family of equations of state whose members differ from each other in the specific interpolation prescription between large energy density region and a realistic hadron resonance gas equation of state at low energy densities. The obtained family of equations of state is applied in hydrodynamic simulations, and the implications of variations in the transition region are discussed by considering transverse momentum spectra and differential elliptic flow of directly emitted hadrons, in particular of strange baryons, for both, RHIC top energy and LHC conditions. Finally, with regard to FAIR physics, implications of the possible presence of a QCD critical point on the equation of state are outlined both, in an exemplary toy model and for an extended quasiparticle model.

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6

Bluhm, Marcus. "QCD equation of state of hot deconfined matter at finite baryon density : a quasiparticle perspective." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23996.

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Анотація:

The quasiparticle model, based on quark and gluon degrees of freedom, has been developed for the description of the thermodynamics of a hot plasma of strongly interacting matter which is of enormous relevance in astrophysics, cosmology and for relativistic heavy-ion collisions as well. In the present work, this phenomenological model is extended into the realm of imaginary chemical potential and towards including, in general, different and independent quark flavour chemical potentials. In this way, nonzero net baryon-density effects in the equation of state are self-consistently attainable. Furthermore, a chain of approximations based on formal mathematical manipulations is presented which outlines the connection of the quasiparticle model with the underlying gauge field theory of strong interactions, QCD, putting the model on firmer ground. A comparison of quasiparticle model results with available lattice QCD data for, e. g., basic bulk thermodynamic quantities and various susceptibilities such as diagonal and off-diagonal susceptibilities, which provide a rich and sensitive testing ground, is found to be successful. Furthermore, different thermodynamic quantities and the phase diagram for imaginary chemical potential are faithfully described. Thus, the applicability of the model to extrapolate the equation of state known from lattice QCD at zero baryon density to nonzero baryon densities is shown. In addition, the ability of the model to extrapolate results to the chiral limit and to asymptotically large temperatures is illustrated by confrontation with available first-principle lattice QCD results. These extrapolations demonstrate the predictive power of the model. Basing on these successful comparisons supporting the idea that the hot deconfined phase can be described in a consistent picture by dressed quark and gluon degrees of freedom, a reliable QCD equation of state is constructed and baryon-density effects are examined, also along isentropic evolutionary paths. Scaling properties of the equation of state with fundamental QCD parameters such as the number of active quark flavour degrees of freedom, the entering quark mass parameters or the numerical value of the deconfinement transition temperature are discussed, and the robustness of the equation of state in the regions of small and large energy densities is shown. Uncertainties arising in the transition region are taken into account by constructing a family of equations of state whose members differ from each other in the specific interpolation prescription between large energy density region and a realistic hadron resonance gas equation of state at low energy densities. The obtained family of equations of state is applied in hydrodynamic simulations, and the implications of variations in the transition region are discussed by considering transverse momentum spectra and differential elliptic flow of directly emitted hadrons, in particular of strange baryons, for both, RHIC top energy and LHC conditions. Finally, with regard to FAIR physics, implications of the possible presence of a QCD critical point on the equation of state are outlined both, in an exemplary toy model and for an extended quasiparticle model.

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7

Mogliacci, Sylvain [Verfasser]. "Probing the finite density equation of state of QCD via resummed perturbation theory / Sylvain Mogliacci." Bielefeld : Universitätsbibliothek Bielefeld, 2014. http://d-nb.info/1053467508/34.

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8

Müller, Daniel Verfasser], Jochen [Akademischer Betreuer] [Wambach, and Michael [Akademischer Betreuer] Buballa. "QCD at finite density with Dyson-Schwinger equations / Daniel Müller. Betreuer: Jochen Wambach ; Michael Buballa." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2013. http://d-nb.info/1106454871/34.

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9

Müller, Daniel [Verfasser], Jochen [Akademischer Betreuer] Wambach, and Michael [Akademischer Betreuer] Buballa. "QCD at finite density with Dyson-Schwinger equations / Daniel Müller. Betreuer: Jochen Wambach ; Michael Buballa." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2013. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-34836.

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10

Li, Anyi. "STUDY OF QCD CRITICAL POINT USING CANONICAL ENSEMBLE METHOD." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/756.

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Анотація:

QCD at non-zero baryon density is expected to have a critical point where the finite temperature crossover at zero density turns into a first order phase transition. To identify this point, we use the canonical ensemble approach to scan the temperaturedensity plane through lattice QCD simulations with Wilson-type fermions. In order to scan a wide range of the phase diagram, we develop an algorithm, the ”winding number expansion method” (WNEM) to fix the numerical instability problem due to the discrete Fourier transform for calculating the projected determinant. For a given temperature, we measure the chemical potential as a function of the baryon number and look for the signal of a first order phase transition. We carry out simulations using clover fermions with mπ ≈ 800MeV on 63 × 4 lattices. As a benchmark, we run simulations for the four degenerate flavor case where we observe a clear signal of the first order phase transition. In the two flavor case we do not see any signal for temperatures as low as 0.83 Tc. To gauge the discretization errors, we also run a set of simulations using Wilson fermions and compare the results to those from the clover fermion. The three flavor case is close to realistic QCD with two light u and d quarks and one heavier s quark. Any hint of the existence of the first order phase transition and, particularly, its critical end point will be valuable for the planned relativistic heavy-ion experiments to search for such a point. In the three flavor case we found a clear signal for the first order phase transition, the critical point is located at a temperature of 0.93(2) Tc and a baryon chemical potential of 3.25(7) Tc. Since the quark mass in our present simulation is relatively heavy, we would like to repeat it with lighter quark masses and larger volumes.

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11

Scior, Philipp Verfasser], Lorenz von [Akademischer Betreuer] Smekal, and Jochen [Akademischer Betreuer] [Wambach. "Lattice Simulations of QCD-like Theories at Finite Baryon Density / Philipp Scior. Betreuer: Lorenz von Smekal ; Jochen Wambach." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1112333193/34.

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12

Scior, Philipp Friedrich [Verfasser], Lorenz von Akademischer Betreuer] Smekal, and Jochen [Akademischer Betreuer] [Wambach. "Lattice Simulations of QCD-like Theories at Finite Baryon Density / Philipp Scior. Betreuer: Lorenz von Smekal ; Jochen Wambach." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-56253.

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13

Glesaaen, Jonas Rylund [Verfasser], Owe [Akademischer Betreuer] [Gutachter] Philipsen, and Dirk-Hermann [Gutachter] Rischke. "Heavy quark QCD at finite temperature and density using an effective theory / Jonas Rylund Glesaaen ; Gutachter: Owe Philipsen, Dirk-Hermann Rischke ; Betreuer: Owe Philipsen." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2017. http://d-nb.info/1129254267/34.

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14

Hilger, Thomas. "Medium Modifications of Mesons." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-94078.

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Анотація:

Das Zusammenspiel von Hadronen und Modifikationen ihrer Eigenschaften auf der einen Seite und spontaner chiraler Symmetriebrechung und Restauration auf der anderen Seite wird untersucht. Es werden die QCD Summenregeln für D und B Mesonen in kalter Materie berechnet. Wir bestimmen die Massenaufspaltung von D - D-bar und B - B-bar Mesonen als Funktion der Kerndichte und untersuchen den Einfluss verschiedener Kondensate in der Näherung linearer Dichteabhängigkeit. Die Analyse beinhaltet ebenfalls D_s und D^*_0 Mesonen. Es werden QCD Summenregeln für chirale Partner mit offenem Charmfreiheitsgrad bei nichtverschwindenden Nettobaryonendichten und Temperaturen vorgestellt. Es wird die Differenz sowohl von pseudoskalaren und skalaren Mesonen, als auch von Axialvektor- und Vektormesonen betrachtet und die entsprechenden Weinberg-Summenregeln hergeleitet. Basierend auf QCD Summenregeln werden die Auswirkungen eines Szenarios auf das rho Meson untersucht, in dem alle chiral ungeraden Kondensate verschwinden wohingegen die chiral symmetrischen Kondensate ihren Vakuumwert behalten. Die komplementären Folgerungen einer Massenverschiebung und Verbreiterung der rho Mesonanregung werden diskutiert. Ein alternativer Zugang basierend auf gekoppelten Dyson-Schwinger- und Bethe-Salpeter-Gleichungen für Quarkbindungszustände wird untersucht. Zu diesem Zwecke wird die analytische Struktur des Quarkpropagators in der komplexen Ebene numerisch untersucht und die Möglichkeit getestet die Anwendbarkeit auf den Sektor der schwer-leicht Quark Systeme im skalaren und pseudoskalaren Kanal, wie dem D Meson, durch Variation des Impulsteilungsparameters zu erweitern. Die Lösungen der Dyson-Schwinger-Gleichung in der Wigner-Weyl-Phase der chiralen Symmetrie bei nichtverschwindenden Stromquarkmassen wird benutzt um den Fall einer expliziten Symmetriebrechung ohne spontane Symmetriebrechung zu untersuchen
The interplay of hadron properties and their modification in an ambient nuclear medium on the one hand and spontaneous chiral symmetry breaking and its restoration on the other hand is investigated. QCD sum rules for D and B mesons embedded in cold nuclear matter are evaluated. We quantify the mass splitting of D - D-bar and B - B-bar mesons as a function of the nuclear matter density and investigate the impact of various condensates in linear density approximation. The analysis also includes D_s and $D^*_0 mesons. QCD sum rules for chiral partners in the open-charm meson sector are presented at nonzero baryon net density or temperature. We focus on the differences between pseudo-scalar and scalar as well as vector and axial-vector D mesons and derive the corresponding Weinberg type sum rules. Based on QCD sum rules we explore the consequences of a scenario for the rho meson, where the chiral symmetry breaking condensates are set to zero whereas the chirally symmetric condensates remain at their vacuum values. The complementarity of mass shift and broadening is discussed. An alternative approach which utilizes coupled Dyson-Schwinger and Bethe-Salpter equations for quark-antiquark bound states is investigated. For this purpose we analyze the analytic structure of the quark propagators in the complex plane numerically and test the possibility to widen the applicability of the method to the sector of heavy-light mesons in the scalar and pseudo-scalar channels, such as the D mesons, by varying the momentum partitioning parameter. The solutions of the Dyson-Schwinger equation in the Wigner-Weyl phase of chiral symmetry at nonzero bare quark masses are used to investigate a scenario with explicit but without dynamical chiral symmetry breaking

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15

Petit, Frédéric. "Reverberation Chamber Modeling Using Finite-Difference Time-Domain Method." Diss., University of Marne la Vallée, 2002. http://hdl.handle.net/10919/71555.

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Since the last few years, the unprecedented growth of communication systems involving the propagation of electromagnetic waves is particularly due to developments in mobile phone technology. The reverberation chamber is a reliable bench-test, enabling the study of the effects of electromagnetic waves on a specific electronic appliance. However, the operating of a reverberation chamber being rather complicated, development of numerical models are of utmost importance to determine the crucial parameters to be considered.This thesis consists in the modelling and the simulation of the operating principles of a reverberation chamber by means of the Finite-Difference Time-Domain method. After a brief study based on field and power measurements performed in a reverberation chamber, the second chapter deals with the different problems encountered during the modelling. The consideration of losses being a very important factor in the operating of the chamber, two methods of implementation of these losses are set out in this chapter. Chapter~3 consists in the analysis of the influence of the stirrer on the first eigenmodes of the chamber; the latter modes can undergo a frequency shift of several MHz. Chapter~4 shows a comparison of results issued from high frequency simulations and theoretical statistical results. The problem of an object placed in the chamber, resulting in a field disturbance is also tackled. Finally, in the fifth chapter, a comparison of statistical results for stirrers having different shapes is set out.

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16

Müller, Daniel. "QCD at finite density with Dyson-Schwinger equations." Phd thesis, 2013. http://tuprints.ulb.tu-darmstadt.de/3483/1/main.pdf.

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In this work we investigate QCD at finite density with Dyson-Schwinger equations. In the first part we consider color-superconducting phases, which occur at high densities through the formation of quark-quark pairs. We describe 2SC and CFL phases with massive strange quarks. We calculate the phase diagram in a hard-thermal-loop / hard-dense-loop approximation which describes the back-coupling of massless quarks to the gluons. We fixed the vertex parameters to a chiral critical temperature of Tc=150 MeV. This approximation results in low critical temperatures for the color-superconducting phases around 20-30 MeV and a too large pion decay constant. To improve the truncation we couple the full color-superconducting quark propagator back to the gluons. In addition to more realistic vacuum observables also the critical temperatures increase to 40-60 MeV. We find a dominant CFL phase at high densities, while at intermediate chemical potential, the ground state is a 2SC phase which also extents to a small band between CFL and normal conducting phase. We also calculate Debye and Meissner masses of the gluons, which can reproduce the results of weak-coupling calculations. In the second part of this work we consider chiral condensates with the possibility of spatial modulations. We investigate 1-dimensional modulations with plane-wave shape, which oscillate between a scalar and a pseudoscalar condensate, in the Dyson-Schwinger formalism. We find an inhomogeneous phase that covers the original first-order chiral phase transition, which is in agreement with similar model calculations.

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17

竹本, 真平, and Shinpei Takemoto. "Holographic Mean-Field Theory for QCD at Finite Density." Thesis, 2012. http://hdl.handle.net/2237/16589.

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18

Scior, Philipp. "Lattice Simulations of QCD-like Theories at Finite Baryon Density." Phd thesis, 2016. http://tuprints.ulb.tu-darmstadt.de/5625/1/main.pdf.

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The exploration of the phase diagram of quantum chromodynamics (QCD) is of great importance to describe e.g. the properties of neutron stars or heavy-ion collisions. Due to the sign problem of lattice QCD at finite chemical potential we need effective theories to study QCD at finite density. Here, we will use a three-dimensional Polyakov-loop theory to study the phase diagrams of QCD-like theories. In particular, we investigate the heavy quark limit of the QCD-like theories where the effective theory can be derived from the full theory by a combined strong coupling and hopping expansion. This expansion can be systematically improved order by order. Since there is no sign problem for the QCD-like theories we consider, we can compare our results to data from lattice calculations of the full theories to make qualitative and quantitative statements of the effective theory’s validity. We start by deriving the effective theory up to next-to-next-to leading-oder, in particular for two-color and G2-QCD where replace the three colors in QCD with only two colors or respectively replace the gauge group SU(3) of QCD with G2. We will then apply the effective theory at finite temperature mainly to test the theory and the implementation but also to make some predictions for the deconfinement phase transition in G2 Yang-Mills theory. Finally, we will turn our attention to the cold and dense regime of the phase diagram where we observe a sharp increase of the baryon density with the quark chemical potential μ, when μ reaches half the diquark mass. At vanishing temperature this is expected to happen in a quantum phase transition with Bose-Einstein-condensation of diquarks. In contrast to the liquid-gas transition in QCD, the phase transition to the Bose-Einstein condensate is continuous. We find evidence that the effective theories for heavy quarks are able to describe the qualitative difference between first and second order phase transitions. For even higher μ we find the rise of the Polyakov loop as well as the quark number density up to the characteristic saturation of the respective theory on a finite lattice.

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19

Kwon, Youngshin [Verfasser]. "QCD sum rule studies at finite density and temperature / Youngshin Kwon." 2009. http://d-nb.info/1000455432/34.

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20

Thakkar, Rishabh. "Mesonic screening mass at zero and finite chemical potential." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5980.

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The finite temperature analysis of QCD is challenging since perturbation theory is not applicable in that regime. A non-perturbative method like lattice QCD is thus required to obtain an estimate of the necessary observables. In this Ph.D. thesis, we study the symmetries of the chiral phase transition and its transition temperature. This is undertaken by measuring the screening masses of those mesons that rotate amongst themselves under the symmetries. Firstly, we discuss the regime of zero chemical potential where it is easy to obtain the correlators using which we calculate the meson screening masses. We discuss the different computational techniques used for calculating the screening masses on lattice following which we do their continuum extrapolate, to obtain their physical values. Using them, we notice the temperatures at which the symmetries get restored. Finally, we expand our analysis to finite chemical potential. Including the non-zero value of chemical potential to the action makes it imaginary resulting in what is called the sign problem. This imaginary action cannot be used to simulate the system on a lattice. We avoid this problem by expanding the screening correlators in a Taylor series expansion in our analysis. Thus, this gives us an estimate of the screening mass at a small finite chemical potential.

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21

Bluhm, Marcus [Verfasser]. "QCD equation of state of hot deconfined matter at finite baryon density : a quasiparticle perspective / vorgelegt von Marcus Bluhm." 2008. http://d-nb.info/992785448/34.

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Дисертації з теми "Finite density QCD"

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