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1
Dzhugan, Aleksandr <1994>. « Advanced properties of some nonlocal operators ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/10002/3/PhD%20Thesis%20Dzhugan.pdf.
Texte intégralRésumé :
In this thesis, we deal with problems, related to nonlocal operators. In particular, we introduce a suitable notion of integral operators acting on functions with minimal requirements at infinity. We also present results of stability under the appropriate notion of convergence and
compatibility results between polynomials of different orders. The theory is developed not only in the pointwise sense, but also in viscosity setting. Moreover, we discover the main properties of extremal type operators,
with some applications. Then using the notion of viscosity solutions and Ishii-Lions technique, we give a different proof of the regularity of the solutions to equations involving fully nonlinear nonlocal operators. In the last part of the thesis we deal with domain variation solutions
and with notions of a viscosity solution to two phase free boundary problem. We are looking at minima of energy functionals, the latter involving p(x)-Laplace operator or a non-negative matrix. Apart from the Riemannian case, we also consider the related Bernoulli functional in
noncommutative framework. Finally, we formulate the suitable definition of a viscosity solution in Carnot groups.
2
Schulze, Tim [Verfasser]. « Nonlocal operators with symmetric kernels / Tim Schulze ». Bielefeld : Universitätsbibliothek Bielefeld, 2020. http://d-nb.info/1206592125/34.
Texte intégral
3
Bucur, C. D. « SOME NONLOCAL OPERATORS AND EFFECTS DUE TO NONLOCALITY ». Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/488032.
Texte intégralRésumé :
In this thesis, we deal with problems related to nonlocal operators, in particular to the fractional Laplacian and some other types of fractional derivatives. We make an extensive introduction to the fractional Laplacian and to some related contemporary research themes. We add to this some original material: the potential theory of this operator and a proof of Schauder estimates with the potential theory approach, the study of a fractional elliptic problem in $mathbb{R}^n$ with convex nonlinearities and critical growth, and a stickiness property of $s$-minimal surfaces as $s$ gets small. Also, focusing our attention on some particular traits of the fractional Laplacian, we prove that other fractional operators have a similar behavior: Caputo stationary functions satisfy a particular density property in the space of smooth functions; an extension operator can be build for Marchaud-stationary functions.
4
BUCUR, CLAUDIA DALIA. « Some nonlocal operators and effects due to nonlocality ». Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/10281/277792.
Texte intégralRésumé :
In this thesis, we deal with problems related to nonlocal operators, in particular to the fractional Laplacian and to some other types of fractional derivatives (the Caputo and the Marchaud derivatives). We make an extensive introduction to the fractional Laplacian, we present some related
contemporary research results and we add some original material. Indeed, we study the potential theory of this operator, introduce a new proof of Schauder estimates using the potential theory approach, we study a fractional elliptic problem in Rn with convex nonlinearities and critical growth
and we present a stickiness property of nonlocal minimal surfaces for small values of the fractional parameter. Also, we point out that the (nonlocal) character of the fractional Laplacian gives rise to some surprising nonlocal effects. We prove that other fractional operators have a similar behavior:
in particular, Caputo-stationary functions are dense in the space of smooth functions; moreover, we introduce an extension operator for Marchaud-stationary functions.
5
Voigt, Paul [Verfasser], et Moritz [Akademischer Betreuer] KaßMann. « Nonlocal operators on domains / Paul Voigt ; Betreuer : Moritz Kaßmann ». Bielefeld : Universitätsbibliothek Bielefeld, 2017. http://d-nb.info/1139117726/34.
Texte intégral
6
Felsinger, Matthieu [Verfasser]. « Parabolic equations associated with symmetric nonlocal operators / Matthieu Felsinger ». Bielefeld : Universitätsbibliothek Bielefeld, 2013. http://d-nb.info/1042557322/34.
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7
FRASSU, SILVIA. « Dirichlet problems for several nonlocal operators via variational and topological methods ». Doctoral thesis, Università degli Studi di Cagliari, 2021. http://hdl.handle.net/11584/309589.
Texte intégralRésumé :
The main topic of the thesis is the study of elliptic differential equations with fractional order driven by nonlocal operators, as the fractional p-Laplacian, the fractional Laplacian for p=2, the general nonlocal operator and its anisotropic version.
Recently, great attention has been focused on the study of fractional and nonlocal operators of elliptic type, both for pure mathematical research and in view of concrete real-world applications. This type of operators arises in a quite natural way in many different contexts, such as, among others, game theory, image processing, optimization, phase transition, anomalous diffusion, crystal dislocation, water waves, population dynamics and geophysical fluid dynamics. The main reason is that nonlocal operators are the infinitesimal generators of Lévy-type stochastic processes. Such processes extend the concept of Brownian motion, where the infinitesimal generator is the Laplace operator, and may contain jump discontinuities.
Our aim is to show existence and multiplicity results for nonlinear elliptic Dirichlet problems, driven by a nonlocal operator, by applying variational and topological methods. Such methods usually exploit the special form of the nonlinearities entering the problem, for instance its symmetries, and offer complementary information. They are powerful tools to show the existence of multiple solutions and establish qualitative results on these solutions, for instance information regarding their location. The topological and variational approach provides not just existence of a solution, usually several solutions, but allow to achieve relevant knowledge about the behavior and properties of the solutions, which is extremely useful because generally the problems cannot be effectively solved, so the precise expression of the solutions is unknown. As a specific example of property of a solution that we look for is the sign of the solution, for example to be able to determine whether it is positive, or negative, or nodal (i.e., sign changing).
8
Abatangelo, N. « Large Solutions for Fractional Laplacian Operators ». Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/320258.
Texte intégralRésumé :
The thesis studies linear and semilinear Dirichlet problems driven by different fractional Laplacians. The boundary data can be smooth functions or also Radon measures. The goal is to classify the solutions which have a singularity on the boundary of the prescribed domain. We first remark the existence of a large class of harmonic functions with a boundary blow-up and we characterize them in terms of a new notion of degenerate boundary trace. Via some integration by parts formula, we then provide a weak theory of Stampacchia's sort to extend the linear theory to a setting including these functions: we study the classical questions of existence, uniqueness, continuous dependence on the data, regularity and asymptotic behaviour at the boundary. Afterwards we develop the theory of semilinear problems, by adapting and generalizing some sub- and supersolution methods. This allows us to build the fractional counterpart of large solutions in the elliptic PDE theory of nonlinear equations, giving sufficient conditions for the existence. The thesis is concluded with the definition and the study of a notion of nonlocal directional curvatures.
9
Foghem, Gounoue Guy Fabrice [Verfasser]. « $L^2$-Theory for nonlocal operators on domains / Guy Fabrice Foghem Gounoue ». Bielefeld : Universitätsbibliothek Bielefeld, 2020. http://d-nb.info/1219215139/34.
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10
Chaker, Jamil [Verfasser], et Moritz [Akademischer Betreuer] KaßMann. « Analysis of anisotropic nonlocal operators and jump processes / Jamil Chaker ; Betreuer : Moritz Kaßmann ». Bielefeld : Universitätsbibliothek Bielefeld, 2017. http://d-nb.info/1150181672/34.
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11
Ghilli, Daria. « Some Results in Nonlinear PDEs : Large Deviations Problems, Nonlocal Operators, and Stability for Some Isoperimetric Problems ». Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424479.
Texte intégralRésumé :
This thesis is concerned with various problems arising in the study of nonlinear elliptic PDE. It is divided into three parts.
In the first part we consider the short time behaviour of stochastic systems affected by a stochastic volatility evolving at a faster time scale. Our mathematical framework is that of multiple time scale systems and singular perturbations.
We are concerned with the asymptotic behaviour of a logarithmic functional of the process, which we study by methods of the theory of homogenization and singular perturbations for fully nonlinear PDEs. We point out three regimes depending on how fast the volatility oscillates relative to the horizon length. We provide some financial applications, namely we prove a large deviation principle for each regime and apply it to the asymptotics of option prices near maturity.
In the second part we are concerned with the well-posedness of Neumann boundary value problems for nonlocal Hamilton-Jacobi equations related to jump processes in general (enough smooth) domains. We consider a nonlocal diffusive term of censored type of order less than 1 and Hamiltonian both in coercive form and in noncoercive Bellman form, whose growth in the gradient make them the leading term in the equation. We prove a comparison principle for bounded sub-and supersolutions in the context of viscosity solutions with generalized boundary conditions, and consequently by Perron's method we get the existence and uniqueness of continuous solutions.
We give some applications in the evolutive setting, proving the large time behaviour of the associated evolutive problem under suitable
assumptions on the data.
In the last part we present some stability results for a class of integral inequalities, the Borell-Brascamp-Lieb inequality and we strengthen, in two different ways, these inequalities in the class of power concave functions.
Then we present some applications to prove analogous quantitative results for certain type of isoperimetric inequalities satisfied by a wide class of variational functionals that can be written in terms of the solution of a suitable elliptic boundary value problem. As a toy model, we consider the torsional rigidity and prove quantitative results for its Brunn-Minkowski inequality and for its consequent (Urysohn type) isoperimetric inequality.Questa tesi si occupa di vari problemi che sorgono nello studio di equazioni alle derivate parziali ellittiche e paraboliche. La tesi è divisa in tre parti. Nella prima parte studiamo il comportamento per tempi brevi di sistemi dinamici a volatilità stocastica che evolve in una scala temporale più veloce.Ci occupiamo di perturbazioni singolari di sistemi a scala temporale multipla. Il nostro primo obiettivo è lo studio del comportamento asintotico di un funzionale logaritmico del processo stocastico, attraverso i metodi della teoria dell' omogeneizzazione e delle perturbazioni singolari per equazioni alle derivate parziali completamente non lineari. Individuiamo tre regimi a seconda della velocità con cui la volatilità oscilla rispetto alla lunghezza dell'orizzonte temporale. Inoltre forniamo alcune applicazioni finanziarie, in particolare proviamo un principio di grandi deviazioni in ogni regime e lo applichiamo per derivare una stima asintotica dei prezzi di opzioni vicino alla maturità e una formula asintotica per la volatilità di Black-Scholes implicita. Nella seconda parte studiamo la buona definizione di problemi al contorno di tipo Neumann, in domini generali (sufficientemente regolari), per equazioni tipo Hamilton-Jacobi con termini non locali che derivano da processi discontinui a salti. Consideriamo un termine diffusivo non locale di tipo censored, di ordine strettamente minore di 1, e un' Hamiltoniana, sia in forma coerciva sia di tipo Bellman non necessariamente coerciva, la cui crescita nel gradiente la rende il termine principale nell'equazione. Dimostriamo un principio di confronto per sotto e sopra soluzioni limitate (in senso di viscosità) con condizioni al contorno generalizzate, e di conseguenza tramite il metodo di Perron otteniamo l'esistenza e l'unicità di soluzioni continue. Diamo alcune applicazioni nel caso evolutivo, dimostrando la convergenza per tempi grandi della soluzione del problema evolutivo alla soluzione del problema stazionario associato, supponendo opportune ipotesi sui dati. Nell'ultima parte presentiamo alcuni risultati di stabilità per una classe di diseguaglianze integrali, le disuguaglianze Borrell-Brascamp-Lieb e rafforziamo, in due modi diversi, queste disuguaglianze nella classe di funzioni a potenza concava. Come applicazione di questo risultato, presentiamo analoghi risultati quantitativi per alcuni tipi di disuguaglianze isoperimetriche soddisfatte da un'ampia classe di funzionali variazionali che possono essere scritti in termini della soluzione di un opportuno problema al contorno ellittico. Come modello giocattolo, consideriamo la rigidità torsionale e dimostriamo risultati quantitativi per la sua disuguaglianza Brunn-Minkowski e per la sua conseguente disuguaglianza isoperimetrica di tipo Urysohn.
12
Cao, Xinlin. « Geometric structures of eigenfunctions with applications to inverse scattering theory, and nonlocal inverse problems ». HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/754.
Texte intégralRésumé :
Inverse problems are problems where causes for desired or an observed effect are to be determined. They lie at the heart of scientific inquiry and technological development, including radar/sonar, medical imaging, geophysical exploration, invisibility cloaking and remote sensing, to name just a few. In this thesis, we focus on the theoretical study and applications of some intriguing inverse problems. Precisely speaking, we are concerned with two typical kinds of problems in the field of wave scattering and nonlocal inverse problem, respectively. The first topic is on the geometric structures of eigenfunctions and their applications in wave scattering theory, in which the conductive transmission eigenfunctions and Laplacian eigenfunctions are considered. For the study on the intrinsic geometric structures of the conductive transmission eigenfunctions, we first present the vanishing properties of the eigenfunctions at corners both in R2 and R3, based on microlocal analysis with the help of a particular type of planar complex geometrical optics (CGO) solution. This significantly extends the previous study on the interior transmission eigenfunctions. Then, as a practical application of the obtained geometric results, we establish a unique recovery result for the inverse problem associated with the transverse electromagnetic scattering by a single far-field measurement in simultaneously determining a polygonal conductive obstacle and its surface conductive parameter. For the study on the geometric structures of Laplacian eigenfunctions, we separately discuss the two-dimensional case and the three-dimensional case. In R2, we introduce a new notion of generalized singular lines of Laplacian eigenfunctions, and carefully investigate these singular lines and the nodal lines. The studies reveal that the intersecting angle between two of those lines is closely related to the vanishing order of the eigenfunction at the intersecting point. We provide an accurate and comprehensive quantitative characterization of the relationship. In R3, we study the analytic behaviors of Laplacian eigenfunctions at places where nodal or generalized singular planes intersect, which is much more complicated. These theoretical findings are original and of significant interest in spectral theory. Moreover, they are applied directly to some physical problems of great importance, including the inverse obstacle scattering problem and the inverse diffraction grating problem. It is shown in a certain polygonal (polyhedral) setup that one can recover the support of the unknown scatterer as well as the surface impedance parameter by finitely many far-field patterns. Our second topic is concerning the fractional partial differential operators and some related nonlocal inverse problems. We present some prelimilary knowledge on fractional Sobolev Spaces and fractional partial differential operators first. Then we focus on the simultaneous recovery results of two interesting nonlocal inverse problems. One is simultaneously recovering potentials and the embedded obstacles for anisotropic fractional Schrödinger operators based on the strong uniqueness property and Runge approximation property. The other one is the nonlocal inverse problem associated with a fractional Helmholtz equation that arises from the study of viscoacoustics in geophysics and thermoviscous modelling of lossy media. We establish several general uniqueness results in simultaneously recovering both the medium parameter and the internal source by the corresponding exterior measurements. The main method utilized here is the low-frequency asymptotics combining with the variational argument. In sharp contrast, these unique determination results are unknown in the local case, which would be of significant importance in thermo- and photo-acoustic tomography.
13
Pagliardini, Dayana. « Fractional minimal surfaces and Allen-Cahn equations ». Doctoral thesis, Scuola Normale Superiore, 2018. http://hdl.handle.net/11384/85738.
Texte intégralRésumé :
In recent years fractional operators have received considerable attention both in pure and applied mathematics. They appear in biological observations, finance, crystal dislocation, digital image reconstruction and minimal surfaces.
In this thesis we study nonlocal minimal surfaces which are boundaries of sets minimizing certain integral norms and can be interpreted as a non-infinitesimal version of classical minimal surfaces. In particular, we consider critical points, with or withouth constraints, of suitable functionals, or approximations through diffuse models as the
Allen-Cahn’s.
In the first part of the thesis we prove an existence and multiplicity result for critical points of the fractional analogue of the Allen-Cahn equation in bounded domains.
We bound the functional using a standard nonlocal tool: we split the domain in two regions and we analyze the three significative interactions. Then, the proof becomes an application of a classical Krasnoselskii’s genus result.
Then, we consider a fractional mesoscopic model of phase transition i.e. the fractional Allen-Cahn equation with the addition of a mesoscopic term changing the ‘pure phases’ ±1 in periodic functions. We investigate geometric properties of the interface of the associated minimal solutions. Then we construct minimal interfaces lying to a strip
of prescribed direction and universal width. We provide a geometric and variational technique adapted to deal with nonlocal interactions.
In the last part of the thesis, we study functionals involving the fractional perimeter.
In particular, first we study the localization of sets with constant nonlocal mean curvature and small prescribed volume in an open bounded domain, proving that these sets are ‘sufficiently close’ to critical points of a suitable potential. The proof is an application of the Lyupanov-Schmidt reduction to the fractional perimeter.
Finally, we consider the fractional perimeter in a half-space. We prove the existence of a minimal set with fixed volume and some of its properties as intersection with the hyperplane {xN = 0}, symmetry, to be a graph in the xN-direction and smoothness.
14
Abatangelo, Nicola. « Large solutions for fractional Laplacian operators ». Thesis, Amiens, 2015. http://www.theses.fr/2015AMIE0019/document.
Texte intégralRésumé :
La thèse étudie les problèmes de Dirichlet linéaires et semilinéaires pour différents opérateurs du type Laplacien fractionnaire. Les données peuvent être des fonctions régularières [régulières] ou plus généralement des mesures de Radon. Le but est de classifier les solutions qui présentent une singularité au bord du domaine prescrit. Nous remarquons d'abord l'existence de toute une gamme de fonctions harmoniques explosant au bord et nous les caractérisons selon une nouvelle notion de trace au bord. A l'aide d'une nouvelle formule d'intégration par parties, nous élaborons ensuite une théorie faible de type Stampacchia pour étendre la théorie linéaire à un cadre qui comprend ces fonctions : nous étudions les questions classiques d'existence, d'unicité, de dépendance à l'égard des données, la régularité et le comportement asymptotique au bord. Puis, nous développons la théorie des problèmes sémilinéaires, en généralisant la méthode des sous- et sursolutions. Cela nous permet de construire l'analogue fractionnaire des grandes solutions dans la théorie des EDPs elliptiques nonlinéaires, en donnant des conditions suffisantes pour l'existence. La thèse se termine par la définition et l'étude d'une notion de courbures directionnelles nonlocalesThe thesis studies linear and semilinear Dirichlet problems driven by different fractional Laplacians. The boundary data can be smooth functions or also Radon measures. The goal is to classify the solutions which have a singularity on the boundary of the prescribed domain. We first remark the existence of a large class of harmoni functions with a boundary blow-up and we characterize them in termsof a new notion of degenerate boundary trace. Via some integration by parts formula, we then provide a weak theory of Stampacchia's sort to extend the linear theory to a setting including these functions: we study the classical questions of existence, uniqueness, continuous dependence on the data, regularity and asymptotic behaviour at the boundary. Afterwards we develop the theory of semilinear problems, by adapting and generalizing some sub- and supersolution methods. This allows us to build the fractional counterpart of large solutions in the elliptic PDE theory of nonlinear equations, giving sufficient conditions for the existence. The thesis is concluded with the definition and the study of a notion of nonlocal directional curvatures
15
Almutairi, Fahad. « Nonlocal vector calculus ». Kansas State University, 2018. http://hdl.handle.net/2097/38781.
Texte intégralRésumé :
Master of ScienceDepartment of Mathematics
Bacim Alali
Nonlocal vector calculus, introduced in generalizes differential operators' calculus to nonlocal calculus of integral operators. Nonlocal vector calculus has been applied to many fields including peridynamics, nonlocal diffusion, and image analysis. In this report, we present a vector calculus for nonlocal operators such as a nonlocal divergence, a nonlocal gradient, and a nonlocal Laplacian. In Chapter 1, we review the local (differential) divergence, gradient, and Laplacian operators. In addition, we discuss their adjoints, the divergence theorem, Green's identities, and integration by parts. In Chapter 2, we define nonlocal analogues of the divergence and gradient operators, and derive the corresponding adjoint operators. In Chapter 3, we present a nonlocal divergence theorem, nonlocal Green's identities, and integration by parts for nonlocal operators. In Chapter 4, we establish a connection between the local and nonlocal operators. In particular, we show that, for specific integral kernels, the nonlocal operators converge to their local counterparts in the limit of vanishing nonlocality.
16
Lopez, Rios Luis Fernando. « Two problems in nonlinear PDEs : existence in supercritical elliptic equations and symmetry for a hypo-elliptic operator ». Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4701/document.
Texte intégralRésumé :
Le travail présenté est dédié à des problèmes d'EDP non linéaires. L'idée principale est de construire des solutions régulières á certaines EDPs elliptiques et hypo-elliptiques et étudier leur propriétés qualitatives. Dans une première partie, on considère un problème sur-critique du type $$-Delta u = lambda e^u$$ avec $lambda > 0$ posé dans un domaine extérieur avec conditions de Dirichlet homogènes. Une réduction en dimension finie permet de prouver l'existence d'un nombre infini de solutions régulières quand $lambda$ est assez petit. Dans une deuxième partie, on étudie la concentration de solutions d'un problème non local $$(-Delta)^s u = u^{p pm epsilon}, u>0, epsilon > 0$$ dans un domaine borné, régulier sous conditions de Dirichlet homogènes. Ici, on prend $0 < s < 1$ et $p:=(N+2s)/(N-2s)$, l'exposant de Sobolev critique. Une réduction en dimension finie dans des espaces fonctionnels bien choisis est utilisée. La partie principale de la fonction réduite est donnée en termes des fonctions de Green et Robin sur le domaine. On prouve que l'existence de solutions dépend des points critiques de la fonction susmentionnée augmentée d'une condition de non-dégénérescence. Enfin, on considère un problème non local dans le groupe de Heisenberg $H$. On s'intéresse à des propriétés de rigidité des solutions stables de $(-Delta_H)^s v = f(v)$ sur $H$, $s in (0,1)$. Une inégalité de type Poincaré connectée à un problème dégénéré dans $R^4_+$ est prouvée. Au travers d'une procédure d'extension, cette inégalité est utilisée pour donner un critère sous lequel les lignes de niveaux de la solution de l'EDP sont des surfaces minimales dans $H$This work is devoted to nonlinear PDEs. The aim is to find regular solutions to some elliptic and hypo-elliptic PDEs and study their qualitative properties. The first part deals with the supercritical problem $$ -Delta u = lambda e^u,$$ $lambda > 0$, in an exterior domain under zero Dirichlet condition. A finite-dimensional reduction scheme provides the existence of infinitely many regular solutions whenever $lambda$ is sufficiently small.The second part is focused on the existence of bubbling solutions for the non-local equation $$ (-Delta)^s u =u^p, ,u>0,$$in a bounded, smooth domain under zero Dirichlet condition; where $0 0$ small). To this end, a finite-dimensional reduction scheme in suitable functional spaces is used, where the main part of the reduced function is given in terms of the Green's and Robin's functions of the domain. The existence of solutions depends on the existence of critical points of such a main term together with a non-degeneracy condition.In the third part, a non-local entire problem in the Heisenberg group $H$ is studied. The main interests are rigidity properties for stable solutions of $$(-Delta_H)^s v = f(v) in H,$$ $s in (0,1)$. A Poincaré-type inequality in connection with a degenerate elliptic equation in $R^4_+$ is provided. Through an extension (or ``lifting") procedure, this inequality will be then used to give a criterion under which the level sets of the above solutions are minimal surfaces in $H$, i.e. they have vanishing mean $H$-curvature
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Veruete, Mario. « Étude d'équations de réplication-mutation non locales en dynamique évolutive ». Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS012/document.
Texte intégralRésumé :
Nous analysons trois modèles non-locaux décrivant la dynamique évolutive d’un trait phénotypique continu soumis à l’action conjointe des mutations et de la sélection. Nous établissons l’existence et l’unicité des solutions du problème de Cauchy, et donnons la description du comportement en temps long de la solution. Dans le premier travail nous étudions l’équation du réplicateur-mutateur en domaine non borné et généralisons aux cas des valeurs sélectives confinantes les résultats connus dans le cas harmonique. À savoir, l’existence d’une unique solution globale, régulière, convergeant en temps long vers un profil universel ; pour cela, nous employons des techniques de décomposition spectrale d’opérateurs de Schrödinger. Le deuxième travail traite d’un modèle dont la valeur sélective est densité-dépendante. Afin de montrer le caractère bien posé de l’équation, nous combinons deux approches. La première est basée sur l’étude de la fonction génératrice des cumulants, satisfaisant une équation de transport non locale et permettant d’obtenir implicitement le trait moyen. La deuxième exploite un changement de variable (formule d’Avron-Herbst), permettant d’écrire la solution en termes du trait moyen et de la solution de l’équation de la chaleur avec même donnée initiale. Finalement, nous étudions un modèle dont le taux de mutation est proportionnel à la valeur moyenne du trait. Nous établissons un lien bijectif entre ce dernier modèle et le deuxième, permettant ainsi de décrire finement la dynamique de la solution. Nous montrons en particulier la croissance exponentielle du trait moyenWe analyze three non-local models describing the evolutionary dynamics of a continuous phenotypic trait undergoing the joint action of mutations and selection. We establish the existence and uniqueness of the solutions to the Cauchy problem, and give a description of the long-time behaviour of the solution. In the first work we study the replicator-mutator equation in the unbounded domain and generalize to cases of selective values confining the known results in the harmonic case. Namely, the existence of a unique global regular solution, converging towards a universal profile; for this, we use spectral decomposition techniques of Schrödinger operators. In the second work, we discuss a model whose fitness value is density-dependent. In order to show the well-posedness of the equation, we combine two approaches. The first is based on the study of the cumulant generating functions, satisfying a non-local transport equation and making it possible to implicitly obtain the average trait. The second uses a change of variable (Avron-Herbst formula), allowing the solution to be written in terms of the average trait and the solution of the heat equation with the same initial data. Finally, we study a model whose mutation rate is proportional to the average value of the trait. We establish a bijective link between this last model and the second, thus making it possible to describe the dynamics of the solution in detail. In particular, we show the exponential growth of the average trait
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Drungilaitė, Jolanta. « Diferencialinio uždavinio su nelokaliosiomis sąlygomis kompleksinių tikrinių reikšmių tyrimas ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130617_181725-06707.
Texte intégralRésumé :
Šiame magistro baigiamajame darbe nagrinėjamas paprastasis diferencialinis operatorius su viena klasikine (pirmo arba antro tipo) sąlyga kairiajame intervalo krašte ir kita nelokaliąja (integraline, Samarskio ir Bitsadzės ar antro tipo) sąlyga dešiniajame intervalo gale. Mokslinėje literatūroje nemažai rašoma apie tokio uždavinio realiojo spektro struktūrą, tačiau kompleksinis spektras yra pakankamai mažai nagrinėjamas. Magistro baigiamajame darbe aprašyta šio uždavinio realiojo ir kompleksinio spektro struktūra, ištirtos kompleksinių tikrinių reikšmių teigiamųjų realiųjų dalių egzistavimo sąlygos, bei jų priklausomybė nuo nelokaliųjų kraštinių sąlygų parametrų.In this master thesis there is investigated ordinary differential operator with one classical (first or second type) boundary condition in the left side of the interval and other nonlocal (integral, Samarski – Bitsadze or second type) boundary condition in the right side of the interval. The structure of the real spectrum of this problem is quite wide described in the scientific literature, but the complex spectrum is investigated not enough. There is described the real and complex spectrum structure of this problem. Also in the master thesis there are analyzed existence conditions of positive real parts of complex eigenvalues, and their dependence on nonlocal boundary condition parameters.
19
Dilley, Daniel Jacob. « An Insight on Nonlocal Correlations in Two-Qubit Systems ». OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2069.
Texte intégralRésumé :
In this paper, we introduce the motivation for Bell inequalities and give some background on two different types: CHSH and Mermin's inequalities. We present a proof for each and then show that certain quantum states can violate both of these inequalities. We introduce a new result stating that for four given measurement directions of spin, two respectively from Alice and two from Bob, which are able to produce a violation of the Bell inequality for an arbitrary shared quantum state will also violate the Bell inequality for a maximally entangled state. Then we provide another new result that characterizes all of the two-qubit states that violate Mermin's inequality.
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Rapalytė, Svajūnė. « Diferencialinio uždavinio su kintamais koeficientais tyrimas ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120620_114424-38644.
Texte intégralRésumé :
Magistro baigiamajame darbe nagrinėjamas diferencialinis operatorius su kintamais koeficientais ir viena klasikine, o kita nelokaliąja Samarskio ir Bitsadzės kraštine sąlyga. Šis uždavinys suvedamas į kanoninį pavidalą. Tiriamos kintamo koeficiento savybės, kaip jos keičiasi suvedant uždavinį į kanoninį pavidalą, taip pat tiriama šio uždavinio spektro priklausomybė nuo nelokaliosios kraštinės sąlygos parametrų.In the Master's Thesis there is investigated a differential operator with variable coefficients, one classical and other nonlocal Samarskii-Bitsadze type boundary condition. There is written the canonical form of this problem. In the thesis there is analyzed the properties of variable coefficients, how they are changing when differential problem is written in the canonical form. Also the dependence of this problem spectrum on nonlocal boundary condition parameters is investigated.
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Šiaulytė, Austėja. « Parabolinės lygties su nelokaliąja integraline Robino sąlyga išreikštinė skirtuminė schema ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130617_182830-33054.
Texte intégralRésumé :
Magistro darbe yra tiriama parabolinės lygties su nelokaliąja integraline Robino sąlyga skirtuminė schema. Skirtuminės schemos stabilumui nagrinėti naudojama skirtuminio operatoriaus su nelokaliąja sąlyga spektro struktūros tyrimo metodika bei Maple programa, skirta kompiuteriniams eksperimentams atlikti. Atlikto magistro darbo rezultatai papildo iki šiol kitų mokslininkų gautus rezultatus tiriant parabolinių lygčių su nelokaliosiomis sąlygomis išreikštinių skirtuminių schemų tyrimus. Magistro darbą sudaro: įvadas, šešios pagrindinės dalys bei išvados. Įvadiniame skyriuje aptariamas temos aktualumas ir darbo tikslas, nurodomi naudojami tyrimo metodai. Antrajame ir trečiajame skyriuose suformuluojama parabolinės lygties su nelokaliąja integraline Robino išreikštinė skirtuminė schema bei jos pakankamoji stabilumo sąlyga. Ketvirtajame, penktajame ir šeštajame skyriuose randamas išreikštinės schemos stabilumas įvairiais atvejais bei pateikiama gautų rezultatų analizė. Septintajame skyriuje atliktas skaitinis eksperimentas. Pateikiamos viso darbo bendrosios išvados.In the master work, explicit difference scheme for parabolic equation with nonlocal integral Robin condition, is considered. Stability condition of difference scheme is used to examine spectrum structure of differential operator with nonlocal condition and software of Maple, which perform of sacred to the computer experiment. My the master work extends and suplements the results of other scientists in analysis for explicit difference scheme for parabolic equation with nonlocal conditions. The master work consists of the introduction, six chapters and the conclusions. In the introduction the topicality of the problem and object of work are defined, also methods of analysis is presented. In the second and third chapters, explicit difference scheme for parabolic equation with nonlocal integral Robin condition is formulated and also the sufficient stability condition of the difference sheme. In the fourth, fifth and the sixth chapters the stability explicit difference scheme is considered and analysis the results is presented. In the seventh chapter the numerical experiment is used. The conlusions are presented.
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Ren, Huilong [Verfasser], Timon [Akademischer Betreuer] Rabczuk, Klaus [Gutachter] Guerlebeck et Klaus [Gutachter] Hackl. « Dual-horizon peridynamics and Nonlocal operator method / Huilong Ren ; Gutachter : Klaus Guerlebeck, Klaus Hackl ; Betreuer : Timon Rabczuk ». Weimar : Bauhaus-Universität Weimar, 2021. http://d-nb.info/1231715081/34.
Texte intégral
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Savin, Anton Yu, et Boris Yu Sternin. « Index defects in the theory of nonlocal boundary value problems and the η-invariant ». Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2008/2614/.
Texte intégralRésumé :
The paper deals with elliptic theory on manifolds with boundary represented as a covering space. We compute the index for a class of nonlocal boundary value problems. For a nontrivial covering, the index defect of the Atiyah-Patodi-Singer boundary value problem is computed. We obtain the Poincaré duality in the K-theory of the corresponding manifolds with singularities.
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Cozzi, M. « QUALITATIVE PROPERTIES OF SOLUTIONS OF NONLINEAR ANISOTROPIC PDES IN LOCAL AND NONLOCAL SETTINGS ». Doctoral thesis, Università degli Studi di Milano, 2016. http://hdl.handle.net/2434/345873.
Texte intégralRésumé :
La tesi è dedicata allo studio di varie proprietà qualitative possedute dalle soluzioni di equazioni ellittiche poste nello spazio euclideo. L'attenzione principale del lavoro è rivolta a soluzioni intere di equazioni anisotrope/eterogenee che mostrano qualche genere di proprietà di simmetria e, in particolare, che posseggono simmetria unidimensionale.
L'elaborato è diviso in due parti. La prima parte è riservata ad equazioni alle derivate parziali locali, mentre la seconda si concentra su di una classe meno usuale di equazioni non locali, determinate da operatori integrali.The thesis is concerned with the study of several qualitative properties shared by the solutions of elliptic equations set in the Euclidean space. The main focus of the work is on entire solutions of anisotropic/heterogeneous equations that show some kind of symmetric properties and, in particular, that possess one-dimensional symmetry. The dissertation is divided into two parts. The first part deals with local partial differential equations, while the second one addresses a class of less familiar nonlocal equations driven by integral operators.
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Debroux, Noémie. « Mathematical modelling of image processing problems : theoretical studies and applications to joint registration and segmentation ». Thesis, Normandie, 2018. http://www.theses.fr/2018NORMIR02/document.
Texte intégralRésumé :
Dans cette thèse, nous nous proposons d'étudier et de traiter conjointement plusieurs problèmes phares en traitement d'images incluant le recalage d'images qui vise à apparier deux images via une transformation, la segmentation d'images dont le but est de délimiter les contours des objets présents au sein d'une image, et la décomposition d'images intimement liée au débruitage, partitionnant une image en une version plus régulière de celle-ci et sa partie complémentaire oscillante appelée texture, par des approches variationnelles locales et non locales. Les relations étroites existant entre ces différents problèmes motivent l'introduction de modèles conjoints dans lesquels chaque tâche aide les autres, surmontant ainsi certaines difficultés inhérentes au problème isolé. Le premier modèle proposé aborde la problématique de recalage d'images guidé par des résultats intermédiaires de segmentation préservant la topologie, dans un cadre variationnel. Un second modèle de segmentation et de recalage conjoint est introduit, étudié théoriquement et numériquement puis mis à l'épreuve à travers plusieurs simulations numériques. Le dernier modèle présenté tente de répondre à un besoin précis du CEREMA (Centre d'Études et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement) à savoir la détection automatique de fissures sur des images d'enrobés bitumineux. De part la complexité des images à traiter, une méthode conjointe de décomposition et de segmentation de structures fines est mise en place, puis justifiée théoriquement et numériquement, et enfin validée sur les images fourniesIn this thesis, we study and jointly address several important image processing problems including registration that aims at aligning images through a deformation, image segmentation whose goal consists in finding the edges delineating the objects inside an image, and image decomposition closely related to image denoising, and attempting to partition an image into a smoother version of it named cartoon and its complementary oscillatory part called texture, with both local and nonlocal variational approaches. The first proposed model addresses the topology-preserving segmentation-guided registration problem in a variational framework. A second joint segmentation and registration model is introduced, theoretically and numerically studied, then tested on various numerical simulations. The last model presented in this work tries to answer a more specific need expressed by the CEREMA (Centre of analysis and expertise on risks, environment, mobility and planning), namely automatic crack recovery detection on bituminous surface images. Due to the image complexity, a joint fine structure decomposition and segmentation model is proposed to deal with this problem. It is then theoretically and numerically justified and validated on the provided images
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MIRAGLIO, PIETRO. « ESTIMATES AND RIGIDITY FOR STABLE SOLUTIONS TO SOME NONLINEAR ELLIPTIC PROBLEMS ». Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/704717.
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Questa tesi è incentrata sullo studio di equazioni differenziali alle derivate parziali di tipo ellittico. La prima parte della tesi riguarda la regolarità delle soluzioni stabili per un'equazione nonlineare con il p-Laplaciano, in un dominio limitato dello spazio Euclideo. La tecnica è basata sull'uso di disuguaglianze di tipo Hardy-Sobolev su ipersuperfici, del quale viene approfondito lo studio. Nella seconda parte viene preso in esame un problema nonlocale di tipo Dirichlet-Neumann. Studiamo la simmetria unidimensionale di alcune sottoclassi di soluzioni stabili, ottenendo risultati in dimensione n=2, 3. Inoltre, studiamo il comportamento asintotico dell'operatore associato a questo problema nonlocale, usando tecniche di Γ-convergenza.This thesis deals with the study of elliptic PDEs. The first part of the thesis is focused on the regularity of stable solutions to a nonlinear equation involving the p-Laplacian, in a bounded domain of the Euclidean space. The technique is based on Hardy-Sobolev inequalities in hypersurfaces involving the mean curvature, which are also investigated in the thesis. The second part concerns, instead, a nonlocal problem of Dirichlet-to-Neumann type. We study the one-dimensional symmetry of some subclasses of stable solutions, obtaining new results in dimensions n=2, 3. In addition, we carry out the study of the asymptotic behaviour of the operator associated with this nonlocal problem, using Γ-convergence techniques.
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CRUZ, Thamires Santos. « Uma teoria de regularidade para equações de volterra fracionárias com dados iniciais locais e não locais ». Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18454.
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CNPQ
Este trabalho trata da teoria de existência, unicidade, regularidade, continuação e alternativa de Blow-up de solução brandas para Equação de Volterra Fracionarias com condições iniciais locais cujo termo não linear satisfaz certas propriedades localmente Lipschitz. Analisamos também o caso de condições iniciais não locais e não linearidades verificando condições do tipo Caratheodory. Neste caso estudamos as propriedades topológicas do conjunto soluções de tais equações.
his work deals with existence, uniqueness, regularity, continuation and Blow up Alternative of mild solutions for Fractional Volterra Equations with local initial conditions, whose nonlinear terms satisfy some locally Lipschitz properties. Moreover we analyse thecase of nonlocal initial conditions and nonlinearities of Caratheodory type. In this case, we study topological properties of the solution set of such equations.
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Tapdigoglu, Ramiz. « Inverse problems for fractional order differential equations ». Thesis, La Rochelle, 2019. http://www.theses.fr/2019LAROS004/document.
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Dans cette thèse, nous nous intéressons à résoudre certains problèmes inverses pour des équations différentielles aux dérivées fractionnaires. Un problème inverse est généralement mal posé. Un problème mal posé est un problème qui ne répond pas à l’un des trois critères de Hadamard pour être bien posé, c’est-à-dire, soit l’existence, l’unicité ou une dépendance continue aux données n'est plus vraie, à savoir, des petits changements dans les données de mesure entraînent des changements indéfiniment importants dans la solution. La plupart des difficultés à résoudre des problèmes mal posés sont causées par l’instabilité de la solution. D’autre part, les équations différentielles fractionnaires deviennent un outil important dans la modélisation de nombreux problèmes de la vie réelle et il y a eu donc un intérêt croissant pour l’étude des problèmes inverses avec des équations différentielles fractionnaires. Le calcul fractionnaire est une branche des mathématiques qui fait référence à l’extension du concept de dérivation classique à la dérivation d’ordre non entier. Calculer une dérivée fractionnaire à un certain moment exige tous les processus précédents avec des propriétés de mémoire. C’est l’avantage principal du calcul fractionnaire d’expliquer les processus associés aux systèmes physiques complexes qui ont une mémoire à long terme et / ou des interactions spatiales à longue distance. De plus, les équations différentielles fractionnaires peuvent nous aider à réduire les erreurs découlant de paramètres négligés dans la modélisation des phénomènes physiquesIn this thesis, we are interested in solving some inverse problems for fractional differential equations. An inverse problem is usually ill-posed. The concept of an ill-posed problem is not new. While there is no universal formal definition for inverse problems, Hadamard [1923] defined a problem as being ill-posed if it violates the criteria of a well-posed problem, that is, either existence, uniqueness or continuous dependence on data is no longer true, i.e., arbitrarily small changes in the measurement data lead to indefinitely large changes in the solution. Most difficulties in solving ill-posed problems are caused by solution instability. Inverse problems come into various types, for example, inverse initial problems where initial data are unknown and inverse source problems where the source term is unknown. These unknown terms are to be determined using extra boundary data. Fractional differential equations, on the other hand, become an important tool in modeling many real-life problems and hence there has been growing interest in studying inverse problems of time fractional differential equations. The Non-Integer Order Calculus, traditionally known as Fractional Calculus is the branch of mathematics that tries to interpolate the classical derivatives and integrals and generalizes them for any orders, not necessarily integer order. The advantages of fractional derivatives are that they have a greater degree of flexibility in the model and provide an excellent instrument for the description of the reality. This is because of the fact that the realistic modeling of a physical phenomenon does not depend only on the instant time, but also on the history of the previous time, i.e., calculating timefractional derivative at some time requires all the previous processes with memory and hereditary properties
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Nguyen, Thi Tuyen. « Comportement en temps long des solutions de quelques équations de Hamilton-Jacobi du premier et second ordre, locales et non-locales, dans des cas non-périodiques ». Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S089/document.
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La motivation principale de cette thèse est l'étude du comportement en temps grand des solutions non-bornées d'équations de Hamilton-Jacobi visqueuses dans RN en présence d'un terme d'Ornstein-Uhlenbeck. Nous considérons la même question dans le cas d'une équation de Hamilton-Jacobi du premier ordre. Dans le premier cas, qui constitue le cœur de la thèse, nous généralisons les résultats de Fujita, Ishii et Loreti (2006) dans plusieurs directions. La première est de considérer des opérateurs de diffusion plus généraux en remplaçant le Laplacien par une matrice de diffusion quelconque. Nous considérons ensuite des opérateurs non-locaux intégro-différentiels de type Laplacien fractionnaire. Le second type d'extension concerne le Hamiltonien qui peut dépendre de x et est seulement supposé sous-linéaire par rapport au gradientThe main aim of this thesis is to study large time behavior of unbounded solutions of viscous Hamilton-Jacobi equations in RN in presence of an Ornstein-Uhlenbeck drift. We also consider the same issue for a first order Hamilton-Jacobi equation. In the first case, which is the core of the thesis, we generalize the results obtained by Fujita, Ishii and Loreti (2006) in several directions. The first one is to consider more general operators. We first replace the Laplacian by a general diffusion matrix and then consider a non-local integro-differential operator of fractional Laplacian type. The second kind of extension is to deal with more general Hamiltonians which are merely sublinear
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(6368468), Daesung Kim. « Stability for functional and geometric inequalities and a stochastic representation of fractional integrals and nonlocal operators ». Thesis, 2019.
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The dissertation consists of two research topics.
The first research direction is to study stability of functional and geometric inequalities. Stability problem is to estimate the deficit of a functional or geometric inequality in terms of the distance from the class of optimizers or a functional that identifies the optimizers. In particular, we investigate the logarithmic Sobolev inequality, the Beckner-Hirschman inequality (the entropic uncertainty principle), and isoperimetric type inequalities for the expected lifetime of Brownian motion.
The second topic of the thesis is a stochastic representation of fractional integrals and nonlocal operators. We extend the Hardy-Littlewood-Sobolev inequality to symmetric Markov semigroups. To this end, we construct a stochastic representation of the fractional integral using the background radiation process. The inequality follows from a new inequality for the fractional Littlewood-Paley square function. We also prove the Hardy-Stein identity for non-symmetric pure jump Levy processes and the L^p boundedness of a certain class of Fourier multiplier operators arising from non-symmetric pure jump Levy processes. The proof is based on Ito's formula for general jump processes and the symmetrization of Levy processes.