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Kungsman, Jimmy. "Resonances of Dirac Operators." Doctoral thesis, Uppsala universitet, Matematiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-223841.
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This thesis consists of a summary of four papers dealing with resonances of Dirac operators on Euclidean 3-space. In Paper I we show that the Complex Absorbing Potential (CAP) method is valid in the semiclassical limit for resonances sufficiently close to the real line if the potential is smooth and compactly supported. In Paper II we continue the investigations initiated in Paper I but here we study clouds of resonances close to the real line and show that in some sense the CAP method remains valid also for multiple resonances. In Paper III we study perturbations of Dirac operators with smooth decaying scalar potentials and show that these possess many resonances near certain points related to the maximum and the minimum of the potential. In Paper IV we show a trace formula of Poisson type for Dirac operators having compactly supported potentials which is related to resonances. The techniques mainly stem from complex function theory and scattering theory.
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Ginoux, Nicolas. "Dirac operators on Lagrangian submanifolds." Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/562/.
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We study a natural Dirac operator on a Lagrangian submanifold of a Kähler manifold. We first show that its square coincides with the Hodge - de Rham Laplacian provided the complex structure identifies the Spin structures of the tangent and normal bundles of the submanifold. We then give extrinsic estimates
for the eigenvalues of that operator and discuss some examples.
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Fischmann, Matthias. "Conformally covariant differential operators acting on spinor bundles and related conformal covariants." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2013. http://dx.doi.org/10.18452/16703.
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Konforme Potenzen des Dirac Operators einer semi Riemannschen Spin-Mannigfaltigkeit werden untersucht. Wir präsentieren einen neuen Beweis, basierend auf dem Traktor Kalkül, für die Existenz von konformen ungeraden Potenzen des Dirac Operators auf semi Riemannschen Spin-Mannigfaltigkeiten. Desweiteren konstruieren wir eine neue Familie von konform kovarianten linearen Differentialoperatoren auf dem standard spin Traktor Bündel. Weiterhin verallgemeinern wir den Existenzbeweis für konforme ungerade Potenzen des Dirac Operators auf semi Riemannsche Spin-Mannigfaltigkeiten. Da die Existenzbeweise konstruktive sind, erhalten wir explizite Formeln für die konforme dritte und fünfte Potenz des Dirac Operators. Basierend auf den expliziten Formeln zeigen wir, dass die konforme dritte und fünfte Potenz des Dirac Operators formal selbstadjungiert (anti selbstadjungiert) bezüglich des L2-Skalarproduktes auf dem Spinorbündel ist. Abschliessend präsentieren wir neue Strukturen der konformen ersten, dritten und fünften Potenz des Dirac Operators: Es existieren lineare Differentialoperatoren auf dem Spinorbündel der Ordnung kleiner gleich eins, so dass die konforme erste, dritte und fünfte Potenz des Dirac Operators ein Polynom in jenen Operatoren ist.Conformal powers of the Dirac operator on semi Riemannian spin manifolds are investigated. We give a new proof of the existence of conformal odd powers of the Dirac operator on semi Riemannian spin manifolds using the tractor machinery. We will also present a new family of conformally covariant linear differential operators on the standard spin tractor bundle. Furthermore, we generalize the known existence proof of conformal power of the Dirac operator on Riemannian spin manifolds to semi Riemannian spin manifolds. Both proofs concering the existence of conformal odd powers of the Dirac operator are constructive, hence we also derive an explicit formula for a conformal third- and fifth power of the Dirac operator. Due to explicit formulas, we show that the conformal third- and fifth power of the Dirac operator is formally self-adjoint (anti self-adjoint), with respect to the L2-scalar product on the spinor bundle. Finally, we present a new structure of the conformal first-, third- and fifth power of the Dirac operator: There exist linear differential operators on the spinor bundle of order less or equal one, such that the conformal first-, third- and fifth power of the Dirac operator is a polynomial in these operators.
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Stadtmüller, Christoph Martin. "Horizontal Dirac Operators in CR Geometry." Doctoral thesis, Humboldt-Universität zu Berlin, 2017. http://dx.doi.org/10.18452/18130.
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In dieser Dissertation beschäftigen wir uns mit angepassten Zusammenhängen und ihren (horizontalen) Dirac-Operatoren auf strikt pseudokonvexen CR-Mannigfaltigkeiten. Einen Zusammenhang nennen wir dann angepasst, wenn er die relevanten Daten parallelisiert. Wir beschreiben den Raum der angepassten Zusammenhänge, indem wir ihre Torsionstensoren studieren, von denen gewisse Teile durch die Geometrie der Mannigfaltigkeit festgelegt sind, während andere frei wählbar sind. Als Anwendung betrachten wir die Eigenschaften der Dirac-Operatoren, die zu diesen Zusammenhängen gehören.
Weiter betrachten wir horizontale Dirac-Operatoren, die nur in Richtung des horizontalen Bündels H ableiten. Diese Operatoren sind besser an die Sub-Riemannsche Struktur einer CR-Mannigfaltigkeit angepasst als die vollen Dirac-Operatoren. Wir diskutieren, wann diese Operatoren formal selbstadjungiert sind und beweisen eine Weitzenböck-Typ-Formel. Wir konzentrieren uns dann auf den horizontalen Dirac-Operator zum Tanaka-Webster-Zusammenhang. Dieser ändert sich konform kovariant, wenn wir die Kontaktform konform ändern. Für diesen Operator betrachten wir weiterhin zwei Beispiele: Wir betrachten S^1-Bündel über Kähler-Mannigfaltigkeiten, insbesondere berechnen wir für Sphären einen Teil des Spektrums. Außerdem betrachten wir kompakte Quotienten der Heisenberggruppe und berechnen hier in den Dimensionen 3 und 5 das volle Spektrum.
Die horizontalen Dirac-Operatoren sind nicht mehr elliptisch, sondern „elliptisch in Richtung von H“. Mithilfe des Heisenbergkalküls stellen wir fest, dass die horizontalen Dirac-Operatoren nicht hypoelliptisch sind. Im Fall des Tanaka-Webster-Zusammenhangs lässt sich aber zeigen, dass der zugehörige Operator auf gewissen Teilen des Spinorbündels hypoelliptisch ist. Dies genügt, um zu beweisen, dass er (nun auf dem gesamten Spinorbündel) ein reines Punktspektrum hat und die Eigenräume, bis auf den Kern, endlich-dimensional sind und aus glatten Eigenspinoren bestehen.In the present thesis, we study adapted connections and their (horizontal) Dirac operators on strictly pseudoconvex CR manifolds. An adapted connection is one that parallelises the relevant data. We describe the space of adapted connections through their torsion tensors, certain parts of which are determined by the geometry of the manifold, while others may be freely chosen. As an application, we study the properties of the Dirac operators induced by these connections. We further consider horizontal Dirac operators, which only derive in the direction of the horizontal bundle H. These operators are more adapted to the essentially sub-Riemannian structure of a CR manifold than the full Dirac operators. We discuss the question of their self-adjointness and prove a Weitzenböck type formula for these operators. Focusing on the horizontal Dirac operator associated with the Tanaka-Webster connection, we show that this operator changes in a covariant way if we change the contact form conformally. Moreover, for this operator we discuss two examples: On S^1-bundles over Kähler manifolds, we can compute part of the spectrum and for compact quotients of the Heisenberg group, we determine the whole spectrum in dimensions three and five. The horizontal Dirac operators are not elliptic, but rather "elliptic in some directions". We review the Heisenberg Calculus for such operators and find that in general, the horizontal Dirac operators are not hypoelliptic. However, in the case of the Tanaka-Webster connection, the associated horizontal Dirac operator is hypoelliptic on certain parts of the spinor bundle and this is enough to prove that its spectrum consists only of eigenvalues and except for the kernel, the corresponding eigenspaces are finite-dimensional spaces of smooth sections.
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Yang, Fangyun Ph D. Massachusetts Institute of Technology. "Dirac operators and monopoles with singularities." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41723.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2007.Includes bibliographical references (p. 75-77).
This thesis consists of two parts. In the first part of the thesis, we prove an index theorem for Dirac operators of conic singularities with codimension 2. One immediate corollary is the generalized Rohklin congruence formula. The eta function for a twisted spin Dirac operator on a circle bundle over a even dimensional spin manifold is also derived along the way. In the second part, we study the moduli space of monopoles with singularities along an embedded surface. We prove that when the base manifold is Kahler, there is a holomorphic description of the singular monopoles. The compactness for this case is also proved.
by Fangyun Yang.
Ph.D.
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Savale, Nikhil Jr (Nikhil A. ). "Spectral asymptotics for coupled Dirac operators." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77804.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 137-139).
In this thesis, we study the problem of asymptotic spectral flow for a family of coupled Dirac operators. We prove that the leading order term in the spectral flow on an n dimensional manifold is of order r n+1/2 followed by a remainder of O(r n/2). We perform computations of spectral flow on the sphere which show that O(r n-1/2) is the best possible estimate on the remainder. To obtain the sharp remainder we study a semiclassical Dirac operator and show that its odd functional trace exhibits cancellations in its first n+3/2 terms. A normal form result for this Dirac operator and a bound on its counting function are also obtained.
by Nikhil Savale.
Ph.D.
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Kim, Yonne Mi. "Unique continuation theorems for the Dirac operator and the Laplace operator." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14469.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1989.Title as it appeared in M.I.T. Graduate List, Feb. 1989: Carleman inequalities and strong unique continuation.
Includes bibliographical references (leaf 59).
by Yonne Mi Kim.
Ph.D.
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Le, Thu Hoai. "Hyperholomorphic structures and corresponding explicit orthogonal function systems in 3D and 4D." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-150508.
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Die Reichhaltigkeit und breite Anwendbarkeit der Theorie der holomorphen Funktionen in der komplexen Ebene ist stark motivierend eine ähnliche Theorie für höhere Dimensionen zu entwickeln. Viele Forscher waren und sind in diese Aufgaben involviert, insbesondere in der Entwicklung der Quaternionenanalysis. In den letzten Jahren wurde die Quaternionenanalysis bereits erfolgreich auf eine Vielzahl von Problemen der mathematischen Physik angewandt. Das Ziel der Dissertation besteht darin, holomorphe Strukturen in höheren Dimensionen zu studieren. Zunächst wird ein neues Holomorphiekonzept vorgelegt, was auf der Theorie rechtsinvertierbarer Operatoren basiert und nicht auf Verallgemeinerungen des Cauchy-Riemann-Systems wie üblich. Dieser Begriff umfasst die meisten der gut bekannten holomorphen Strukturen in höheren Dimensionen. Unter anderem sind die üblichen Modelle für reelle und komplexe quaternionenwertige Funktionen sowie Clifford-algebra-wertige Funktionen enthalten. Außerdem werden holomorphe Funktionen mittels einer geeignete Formel vom Taylor-Typ durch spezielle Funktionen lokal approximiert. Um globale Approximationen für holomorphe Funktionen zu erhalten, werden im zweiten Teil der Arbeit verschiedene Systeme holomorpher Basisfunktionen in drei und vier Dimensionen mittels geeigneter Fourier-Entwicklungen explizit konstruiert. Das Konzept der Holomorphie ist verbunden mit der Lösung verallgemeinerter Cauchy-Riemann Systeme, deren Funktionswerte reellen Quaternionen bzw. reduzierte Quaternionen sind. In expliziter Form werden orthogonale holomorphe Funktionensysteme konstruiert, die Lösungen des Riesz-Systems bzw. des Moisil-Teodorescu Systems über zylindrischen Gebieten im R3, sowie Lösungen des Riesz-Systems in Kugeln des R4 sind. Um konkrete Anwendungen auf Randwertprobleme realisieren zu können wird eine orthogonale Zerlegung eines Rechts-Quasi-Hilbert-Moduls komplex-quaternionischer Funktionen unter gegebenen Bedingungen studiert. Die Ergebnisse werden auf die Behandlung von Maxwell-Gleichungen mit zeitvariabler elektrischer Dielektrizitätskonstante und magnetischer Permeabilität angewandtThe richness and widely applicability of the theory of holomorphic functions in complex analysis requires to perform a similar theory in higher dimensions. It has been developed by many researchers so far, especially in quaternionic analysis. Over the last years, it has been successfully applied to a vast array of problems in mathematical physics. The aim of this thesis is to study the structure of holomorphy in higher dimensions. First, a new concept of holomorphy is introduced based on the theory of right invertible operators, and not by means of an analogue of the Cauchy-Riemann operator as usual. This notion covers most of the well-known holomorphic structures in higher dimensions including real, complex, quaternionic, Clifford analysis, among others. In addition, from our operators a local approximation of a holomorphic function is attained by the Taylor type formula. In order to obtain the global approximation for holomorphic functions, the second part of the thesis deals with the construction of different systems of basis holomorphic functions in three and four dimensions by means of Fourier analysis. The concept of holomorphy is related to the null-solutions of generalized Cauchy-Riemann systems, which take either values in the reduced quaternions or real quaternions. We obtain several explicit orthogonal holomorphic function systems: solutions to the Riesz and Moisil-Teodorescu systems over cylindrical domains in R3, and solutions to the Riesz system over spherical domains in R4. Having in mind concrete applications to boundary value problems, we investigate an orthogonal decomposition of complex-quaternionic functions over a right quasi-Hilbert module under given conditions. It is then applied to the treatment of Maxwell’s equations with electric permittivity and magnetic permeability depending on the time variable
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Bär, Christian. "Das Spektrum von Dirac-Operatoren." Bonn : [s.n.], 1991. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=003506032&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Afentoulidis-Almpanis, Spyridon. "Noncubic Dirac Operators for finite-dimensional modules." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0035.
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Cette thèse porte sur l’étude des opérateurs de Dirac non-cubiques dans le cadre de la théorie des représentations des groupes de Lie. Après avoir présenté des notions de la théorie de Lie et des algèbres de Clifford, nous rappelons les propriétés principales des opérateurs de Dirac cubiques D introduits par Kostant en 1999. Ces résultats ont rapidement suscité un vif intérêt. En particulier, à la fin des années 2000, Vogan introduit une cohomologie définie par l’opérateur de Kostant et suggère une classification cohomologique des représentations. La cohomologie de Dirac a été calculée pour diverses familles de représentations, telles que les séries discrètes, les modules Aq(>) ou les modules de dimension finie. Pour les modules de dimension finie, la cohomologie de Dirac coïncide avec le noyau de D. Il apparait que l’opérateur de Dirac de Kostant est une version algébrique d’un opérateur différentiel issu d’une famille continue d’opérateurs de Dirac géométriques introduits par Slebarski dans les années 1980 dans le cadre de fibrés au- dessus d’espaces homogènes G/H de groupes compacts. Ce qui distingue l’opérateur de Dirac de Kostant est qu’il est le seul membre de cette famille dont le carré, généralisant une formule de Parthasarathy, diffère de l’opérateur de Casimir à un scalaire près. Cette propriété a des applications importantes en théorie des représentations des groupes de Lie. Le carré des opérateurs de Dirac non-cubiques, i.e des autres membres de la famille d’opérateurs de Slebarski, a été calculé par Agricola qui a également établit des liens précis entre ces opérateurs non-cubiques et la théorie des cordes en physique. Par ailleurs, les opérateurs de Dirac non-cubiques sont des opérateurs différentiels invariants, et donc leur noyau est le siège de représentations (de dimension finie) de groupes compacts. Dans cette thèse nous étudions le noyau des opérateurs de Dirac non-cubiques, et nous montrons, sous certaines conditions sur les espaces homogènes G/H, que ce noyau contient le noyau de l’opérateur de Dirac cubique. Nous obtenons en fait une formule explicite pour le noyau que nous appliquons aux cas des algèbres de Lie classiques et des algèbres de Lie exceptionnelles. Nous constatons que certaines propriétés des opérateurs non-cubiques sont analogues à celles de l’opérateur de Dirac de Kostant, tel que l’indice. Nous déduisons également quelques observations sur les opérateurs de Dirac géométrique non-cubiquesThis thesis focuses on the study of noncubic Dirac operators within the framework of representation theory of Lie groups. After recalling basic notions of Lie theory and Clifford algebras, we present the main properties of cubic Dirac operators D introduced by Kostant in 1999. These results quickly aroused great interest. In particular, in the late 1990’s, Vogan introduced a cohomology defined by Kostant operator D and suggested a cohomological classification of representations. Dirac cohomology was computed for various families of representations, such as the discrete series, Aq(>) modules or finite dimensional representations. It turns out that for finite dimensional modules, Dirac cohomology coincides with the kernel of D. It appears that Kostant’s Dirac operator is an algebraic version of a specific member of a continuous family of geometric Dirac operators introduced by Slebarski in the mid 1980’s in the context of bundles over homogeneous spaces G/H of compact groups. What distinguishes the cubic Dirac operator is that it is the only member of this family whose square, generalizing Parthasarathy’s formula, differs from the Casimir operator up to a scalar. This property has important applications in representation theory of Lie groups. The square of the noncubic Dirac operators, i.e. of the other members of Slebarski’s family, was calculated by Agricola who also established precise links between these noncubic operators and string theory in physics. Actually, noncubic Dirac operators are invariant differential operators, and therefore their kernels define (finite-dimensional) representations of compact groups. In this thesis we study the kernel of noncubic Dirac operators, and we show that, under certain conditions on the homogeneous spaces G/H, the kernel contains the kernel of the cubic Dirac operator. We obtain an explicit formula for the kernel which we apply to the case of classical Lie algebras and of exceptional Lie algebras. We remark that some properties of noncubic operators are analogous to those of Kostant cubic Dirac operator, such as the index. We also deduce some observations on noncubic geometric Dirac operators
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Anghel, Nicolae. "L²-index theorems for perturbed Dirac operators /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487598303839391.
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Wittmann, Anja [Verfasser], and Sebastian [Akademischer Betreuer] Goette. "Eta-forms and adiabatic limits for fibrewise Dirac operators with varying kernel dimension = Eta-Formen und adiabatische Limiten für faserweise Dirac Operatoren mit variierender Kern-Dimension." Freiburg : Universität, 2016. http://d-nb.info/1122647476/34.
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Pfäffle, Frank [Verfasser]. "Eigenwertkonvergenz für Dirac-Operatoren / Frank Pfäffle." Aachen : Shaker, 2003. http://d-nb.info/1179023595/34.
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Nita, A. "Essential Self-Adjointness of the Symplectic Dirac Operators." Thesis, University of Colorado at Boulder, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10108819.
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The main problem we consider in this thesis is the essential self-adjointness of the symplectic Dirac operators D and D constructed by Katharina Habermann in the mid 1990s. Her constructions run parallel to those of the well-known Riemannian Dirac operators, and show that in the symplectic setting many of the same properties hold. For example, the symplectic Dirac operators are also unbounded and symmetric, as in the Riemannian case, with one important difference: the bundle of symplectic spinors is now infinite-dimensional, and in fact a Hilbert bundle. This infinite dimensionality makes the classical proofs of essential self-adjointness fail at a crucial step, namely in local coordinates the coefficients are now seen to be unbounded operators on L2(Rn). A new approach is needed, and that is the content of these notes. We use the decomposition of the spinor bundle into countably many finite-dimensional subbundles, the eigenbundles of the harmonic oscillator, along with the simple behavior of D and D with respect to this decomposition, to construct an inductive argument for their essential self-adjointness. This requires the use of ancillary operators, constructed out of the symplectic Dirac operators, whose behavior with respect to the decomposition is transparent. By an analysis of their kernels we manage to deduce the main result one eigensection at a time.
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Fletcher, Daniel. "Simple collision operators for direct Vlasov solvers." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63944/.
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Existing codes for directly solving for the particle distribution function in laser plasma interaction studies either assume a collisionless plasma or solve for the full Fokker-Planck collision term. The former approach is the basis of an existing code at Warwick (VALIS). The latter approach is computationally expensive and often relies on a spherical harmonic expansion of the distribution function, making the implementation of a laser driver difficult. Here the existing collisionless code is extended by including reduced collision operators based on both the Krook and Fokker-Planck operator. The formulation of a fully conservative velocity-dependent Krook operator that shows agreement classical transport co-efficients in the regimes they are valid. The accuracy of the operator is shown to be improved using a normalisation method to ensure the Krook model yields the same heat flux as the Fokker-Planck model. The Krook model is also shown to be in agreement with full Vlasov-Fokker-Planck simulations of non-local transport. Two forms of a model Fokker-Planck operator are also included as a comparison to other reduced models of collisions.
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Scott, Simon Gareth. "Determinants of Dirac operators over a manifold with boundary." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306706.
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Thumstädter, Torsten. "Parameteruntersuchungen an Dirac-Modellen." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10633955.
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Dumais, Guy. "Killing spinors and spectral properties of the Dirac operator." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55442.
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A survey of the spectral properties of the classical Dirac operator on a Riemannian spin manifold is made. Killing spinors, which are special eigenfunctions of the Dirac operator, are studied and necessary conditions for their existence are given. Killing spinors on $ IR sp{n}$, $S sp{n}$ and $H sp{n}$ are also computed explicitly. Finally the transformation law for Dirac operator under conformal change of the metric is computed and a lower bound for the eigenvalues is given.
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Andersson, Linnéa. "Linear-scaling recursive expansion of the Fermi-Dirac operator." Thesis, Uppsala universitet, Tillämpad matematik och statistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-382829.
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Li, Liangpan. "Local spectral asymptotics and heat kernel bounds for Dirac and Laplace operators." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/23004.
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In this dissertation we study non-negative self-adjoint Laplace type operators acting on smooth sections of a vector bundle. First, we assume base manifolds are compact, boundaryless, and Riemannian. We start from the Fourier integral operator representation of half-wave operators, continue with spectral zeta functions, heat and resolvent trace asymptotic expansions, and end with the quantitative Wodzicki residue method. In particular, all of the asymptotic coefficients of the microlocalized spectral counting function can be explicitly given and clearly interpreted. With the auxiliary pseudo-differential operators ranging all smooth endomorphisms of the given bundle, we obtain certain asymptotic estimates about the integral kernel of heat operators. As applications, we study spectral asymptotics of Dirac type operators such as characterizing those for which the second coefficient vanishes. Next, we assume vector bundles are trivial and base manifolds are Euclidean domains, and study non-negative self-adjoint extensions of the Laplace operator which acts component-wise on compactly supported smooth functions. Using finite propagation speed estimates for wave equations and explicit Fourier Tauberian theorems obtained by Yuri Safarov, we establish the principle of not feeling the boundary estimates for the heat kernel of these operators. In particular, the implied constants are independent of self-adjoint extensions. As a by-product, we affirmatively answer a question about upper estimate for the Neumann heat kernel. Finally, we study some specific values of the spectral zeta function of two-dimensional Dirichlet Laplacians such as spectral determinant and Casimir energy. For numerical purposes we substantially improve the short-time Dirichlet heat trace asymptotics for polygons. This could be used to measure the spectral determinant and Casimir energy of polygons whenever the first several hundred or one thousand Dirichlet eigenvalues are known with high precision by other means.
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Richert, Manfred. "Streutheorie für Diracsche Aussenraumaufgaben." Bonn : [Math.-Naturwiss. Fak. der Univ.], 1992. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=005421124&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Orduz, Barrera Juan Camilo. "Induced Dirac-Schrödinger operators on $S^1$-semi-free quotients." Doctoral thesis, Humboldt-Universität zu Berlin, 2017. http://dx.doi.org/10.18452/18565.
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John Lott berechnete eine Signatur mit ganzzahligen Werten für den Orbitraum einer kompakten, orientierbaren (4k + 1)-Mannigfaltigkeit mit einer halbfreien S1-Wirkung. Diese Signatur ist eine Homotopieinvariante für den Orbitraum. Allerdings konstruierte er keinen Operator vom Dirac-Typ, der die Signatur als Index besitzt. In dieser Arbeit konstruieren wir einen solchen Operator auf dem Orbitraum der S1-Wirkung, einem Thom-Mather stratifizierten Raum mit einem singulären Stratum von positiver Dimension, und wir zeigen, dass der Operator im wesentlichen eindeutig bestimmt ist. Ferner zeigen wir, dass sein Index mit Lotts Signatur übereinstimmt, zumindest wenn der stratifizierte Raum die sogenannte Witt-Bedingung erfüllt. Wirnennendiesen Operator den induzierten Dirac-Schrödinger Operator. Unsere Konstruktionsstrategie ist es, einen geeigneten S1-invarianten transversal elliptischen Operator erster Ordnung auf den S1-invarianten Differentialformen zu definieren, der den gesuchten Operator auf den Differentialformen des Orbitraums induziert.
Die Witt-Bedingung, eine topologische Bedingung, welche in diesem Fall von der Kodimension der betrachteten Punktmenge abhängt, lässt verschiedene analytische Schlussfolgerungen zu. Insbesondere ist, wenn die Bedingung nicht erfüllt ist, der Hodge-de Rham Operator auf dem Quotientenraum nicht notwendigerweise essentiell selbstadjungiert und die Wahl einer Randbedingung ist daher notwendig. Diese Wahlfreiheit erscheint unnatürlich in Anbetracht der Tatsache, dass Lotts Signatur unabhängig von der Witt-Bedingung wohldefiniert ist.
Der Dirac-Schrödinger Operator, der in dieser Arbeit konstruiert wird, unterschei- det sich vom Hodge-de Rham Operator durch einen Term nullter Ordnung, welcher sicherstellt, dass der Operator wesentlich selbstadjungiert ist. Außerdem antikommutiert dieser Term nullter Ordnung mit der Signatur-Involution, wodurch der gesamte Operator zerfällt und so der Index berechnet werden kann, auch wenn die Witt-Bedingung nicht erfüllt ist.John Lott has computed an integer-valued signature for the orbit space of a compact orientable (4k + 1) manifold with a semi-free S1-action, which is a homotopy invariant of that space, but he did not construct a Dirac type operator which has this signature as its index. In this Thesis, we construct such operator on the orbit space, a Thom-Mather stratified space with one singular stratum of positive dimension, and we show that it is essentially unique and that its index coincides with Lott’s signature, at least when the stratified space satisfies the so called Witt condition. We call this operator the induced Dirac-Schrödinger operator. The strategy of the construction is to “push down” an appropriate S1-invariant first order transversally elliptic operator to the quotient space. The Witt condition, a topological condition which in this case depends on the codi- mension of the fixed point set, has various analytic consequences. In particular, when not satisfied, the Hodge-de Rham operator on the quotient space does not need to be essentially self-adjoint and therefore a choice of boundary conditions is required. This choice freedom is not natural in view of the fact that Lott’s signature is well defined independently of the Witt condition. The Dirac-Schrödinger operator constructed in this Thesis differs from the Hodge-de Rham operator by a zero order term which ensures it to be essentially self-adjoint. Moreover, this zero order term anti-commutes with the chirality involution allowing the whole operator to split so that the index can be computed even if the Witt condition is not satisfied.
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Hughes, Daniel Gordon John. "Spectral analysis of Dirac operators under integral conditions on the potential." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/43141/.
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We show that the absolutely continuous part of the spectral function of the one-dimensional Dirac operator on a half-line with a constant mass term and a real, square-integrable potential is strictly increasing throughout the essential spectrum (-∞,-1]U[1,∞). The proof is based on estimates for the transmission coefficient for the full-line scattering problem with a truncated potential and a subsequent limiting procedure for the spectral function. Furthermore, we show that the absolutely continuous spectrum persists when an angular momentum term is added, thus establishing the result for spherically symmetric Dirac operators in higher dimensions, too. Finally, with regard to this problem, we show that a sparse perturbation of a square integrable potential does not cause the absolutely continuous spectrum to become larger in the one-dimensional case. The final problem considered is regarding bound states, where we show that if the electric potential obeys the asymptotic bound C:=\lim sup_x→∞_ x|q(x)|<∞ then the eigenvalues outside of the spectral gap [-m,m] must obey Σ_n_(λ²_n-1)
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Hachem, Ghias. "Théorie spectrale de l'opérateur de Dirac avec un potentiel électromagnétique à croissance linéaire à l'infini." Paris 13, 1988. http://www.theses.fr/1988PA132008.
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L'objet de cette thèse est la théorie spectrale de l'opérateur de Dirac associé à un champ électrique extérieur. Notre approche est celle de la théorie de la diffusion. Dans un premier temps on étudie l'opérateur non perturbe dont le potentiel est une fonction linéaire d'une variable (champ électrique constant). On construit alors les fonctions propres généralisées de cet opérateur, pour cela on étudie une équation différentielle du second ordre dépendant d'un paramètre. On donne ensuite des estimations pour les fonctions propres généralisées et le théorème d'absorption limite. Dans la deuxième partie on étudie les perturbations de cet opérateur de base par des potentiels de courte portée, on donne une description du spectre de ces opérateurs, on obtient la représentation spectrale de ces opérateurs ainsi que des estimations montrant la décroissance dans le temps des états de diffusion.
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Bär, Christian, and Nicolas Ginoux. "Classical and quantum fields on Lorentzian manifolds." Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/5997/.
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We construct bosonic and fermionic locally covariant quantum fields theories on curved backgrounds for large classes of fields. We investigate the quantum field and n-point functions induced by suitable states.
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Zalczer, Sylvain. "Propriétés spectrales de modèles de graphène périodique et désordonné." Thesis, Toulon, 2020. http://www.theses.fr/2020TOUL0003.
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Cette thèse traite de différents aspects de la théorie spectrale d’opérateurs utilisés pour modéliser le graphène. Elle est constituée de deux parties. La première traite du cas périodique. Je commence par présenter la théorie générale des systèmes périodiques. J’introduis ensuite les différents modèles de graphène en les comparant. Enfin, je m’intéresse à différentes façons de rendre le graphène semi-conducteur. Je fais en particulier une étude de nanorubans de divers types et présente un résultat d’ouverture d’une lacune spectrale pour un opérateur pseudo-différentiel. La deuxième partie traite du cas désordonné. Je commence par présenter la théorie générale des opérateurs aléatoires. J’explique ensuite succinctement l’analyse multi-échelles qui est la méthode permettant de montrer le résultat essentiel de cette théorie, appelé localisation d’Anderson. Enfin, je donne la preuve de cette localisation pour un modèle de graphène ainsi qu’un résultat sur la densité d’états intégréeThis thesis deals with various aspects of spectral theory of operators used to model graphene. It is made of two parts.The first parts deals with the periodic case. I begin by presenting a general theory of periodic systems. I introduce then different models of graphene and compare them. Finally, I look at various ways to make graphene a semiconductor. In particular, I study different types of nanoribbons and I give a result of gap opening for a pseudodifferential operator. The second part deals with the disordered case. I begin by presenting a general theory of random operators. Then, I briefly explain multiscale analysis, which is the method used to prove the main result of this theory, which is called Anderson localization. Finally, I give a proof of this localization for a model of graphene and a result on the integrated density of states
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Gajdzinski, Cezary. "L2-Indices for Perturbed Dirac Operators on Odd Dimensional Open Complete Manifolds." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40151.
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For perturbations of the Callias and Anghel type the L2-index of the perturbed Dirac operator on a Spin c -manifold is realized as the result of pairing an element in K -homology with an element of compactly supported K -cohomology. This is achieved by putting the problem of calculating the Fredholm index of the perturbed Dirac operator in the framework of KK-theory and using the identification of K-groups with KK-groups. The formula for the Fredholm index is given in terms of topological data of the Spin c-manifold and the structure of the perturbation.Ph. D.
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Kusterer, Daniel-Jens. "Quark properties, topology and confinement from Lattice Gauge Theory." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11514075.
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Jakubassa-Amundsen, Doris. "Spectral Theory of the Atomic Dirac Operator in the No-Pair Formalism." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-23824.
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Tạ, Ngọc Trí. "Results on the number of zero modes of the Weyl-Dirac operator." Thesis, Lancaster University, 2009. http://eprints.lancs.ac.uk/30804/.
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For a given magnetic potential A one can define the Weyl-Dirac operator σ·(-i∇-A) on R³. An L² eigenfunction of σ·(-i∇-A) corresponding to 0 is called a zero mode. In this thesis we will be concerned with the zero mode problem for the Weyl-Dirac operator and some related problems. The main results are: (i) upper bounds for the number of zero modes of the Weyl-Dirac operator in three dimensions when scaling a given magnetic field. A similar version for the Dirac operator in two dimensions is also obtained. There are also related results to estimate the number of zero modes of the massless Dirac operator, and the dimension of the eigenspaces at threshold energies for the Dirac operator with positive mass. (ii) construction of Dirac operators on the unit ball S² of R³ as well as the determination of their spectrum in case of "constant" magnetic fields. We also show another proof for the Aharonov-Casher theorem for S² based on results about spectral properties of Dirac operators that we have obtained. (iii) a formula giving the number of zero modes of the Weyl-Dirac operator for a special magnetic field, which is the result of pullbacks from the "constant" volume form of S². We also obtain a lower bound for the number of zero modes for the Weyl-Dirac operator corresponding to certain scaled magnetic fields; the magnetic fields are parallel to fibres of the Hopf fibration (pulled-back to R³ using inverse stereographic projection).
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Roos, Saskia [Verfasser]. "The Dirac operator under collapse with bounded curvature and diameter / Saskia Roos." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1170777902/34.
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Kramer, Wolfram. "Der Diracoperator auf Faserungen." Bonn : [s.n.], 1999. http://catalog.hathitrust.org/api/volumes/oclc/41464666.html.
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Inyangala, Edward Buhuru. "Categorical semi-direct products in varieties of groups with multiple operators." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/4890.
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The notion of a categorical semidirect product was introduced by Bourn and Janelidze as a generalization of the classical semidirect product in the category of groups. The main aim of this work is to study the general properties of semidirect products of groups with operators, describe them in various classical varieties of such algebraic structures and apply the results to homological algebra and related areas of modern algebra. The context in which the study is done is a semiabelian category (that is, a pointed, Barr-exact and Bourn-protomodular category). The main result in the thesis is the construction of the semidirect product in a variety -RLoop of right -loops as the product of underlying sets equipped with the -algebra structure. A variety of right -loops is a variety that is pointed, has a binary + (not necessarily associative or commutative) and a binary satisfying the identities 0 + x = x, x + 0 = x, (x + y) y = x and (x - y) + y = x. Thus, -RLoop is a generalization of the variety of -groups introduced by Higgins and the results obtained are valid for varieties of -loops. We also describe precrossed and crossed modules in the variety -RLoop. The theory of crossed modules developed is independent of that developed by Janelidze for crossed modules in an arbitrary semiabelian category and gives simplified explicit formulae for crossed modules in -RLoop. Finally, we mention that our constructions agree with the known ones in the familiar algebraic categories, specifically the categories of groups, rings and Lie algebras.
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Downes, Robert James. "Cosserat elasticity, spectral theory of first order systems, and the massless Dirac operator." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1417503/.
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This thesis is concerned with the study of the massless Dirac operator in dimension three and is, in part, based upon [12, 22, 21, 26, 25]. An introduction is given in Chapter 1. In Chapter 2 we study a special version of Cosserat elasticity, with deformations induced by rotations only, and no displacements. We prove that for a particular choice of elastic moduli and in the stationary setting (harmonic dependence on time) our mathematical model reduces to the massless Dirac equation. Chapter 3 contains a description of the progress recently made in the spectral theory of first order systems, with a particular focus on dimension three presented in Chapter 4. We prove in Chapter 5 that the second asymptotic coefficient of the counting function of a first order system has the geometric meaning of the massless Dirac action. Finally, in Chapter 6 we examine the spectral asymmetry of the massless Dirac operator. We work on a 3-torus equipped, initially, with a Euclidean metric and consider the behaviour of the spectrum under a perturbation of the metric. We derive an explicit asymptotic formula for the eigenvalue closest to zero.
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Lapp, Frank. "An index theorem for operators with horn singularities." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2013. http://dx.doi.org/10.18452/16838.
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Die abgeschlossenen Erweiterungen der sogenannten geometrischen Operatoren (Spin-Dirac, Gauß-Bonnet und Signatur-Operator) auf Mannigfaltigkeiten mit metrischen Hörnern sind Fredholm-Operatoren und ihr Index wurde von Matthias Lesch, Norbert Peyerimhoff und Jochen Brüning berechnet. Es wurde gezeigt, dass die Einschränkungen dieser drei Operatoren auf eine punktierte Umgebung des singulären Punkts unitär äquivalent zu irregulär singulären Operator-wertigen Differentialoperatoren erster Ordnung sind. Die Lösungsoperatoren der dazugehörigen Differentialgleichungen definierten eine Parametrix, mit deren Hilfe die Fredholmeigenschaft bewiesen wurde. In der vorliegenden Doktorarbeit wird eine Klasse von irregulären singulären Differentialoperatoren erster Ordnung, genannt Horn-Operatoren, eingeführt, die die obigen Beispiele verallgemeinern. Es wird bewiesen, dass ein elliptischer Differentialoperator erster Ordnung, dessen Einschränkung auf eine punktierte Umgebung des singulären Punkts unitär äquivalent zu einem Horn-Operator ist, Fredholm ist, und sein Index wird berechnet. Schließlich wird dieser abstrakte Index-Satz auf geometrische Operatoren auf Mannigfaltigkeiten mit "multiply warped product"-Singularitäten angewendet, welche eine wesentliche Verallgemeinerung der metrischen Hörner darstellen.The closed extensions of geometric operators (Spin-Dirac, Gauss-Bonnet and Signature operator) on a manifold with metric horns are Fredholm operators, and their indices were computed by Matthias Lesch, Norbert Peyerimhoff and Jochen Brüning. It was shown that the restrictions of all three operators to a punctured neighbourhood of the singular point are unitary equivalent to a class of irregular singular operator-valued differential operators of first order. The solution operators of the corresponding differential equations defined a parametrix which was applied to prove the Fredholm property. In this thesis a class of irregular singular differential operators of first order - called horn operators - is introduced that extends the examples mentioned above. It is proved that an elliptic differential operator of first order whose restriction to the neighbourhood of the singular point is unitary equivalent to a horn operator is Fredholm and its index is computed. Finally, this abstract index theorem is applied to compute the indices of geometric operators on manifolds with multiply warped product singularities that extend the notion of metric horns considerably.
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Tyni, T. (Teemu). "Direct and inverse scattering problems for perturbations of the biharmonic operator." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526220789.
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Abstract This dissertation is a combination of four articles on the topic of scattering problems for a biharmonic operator. The operator of interest has two coefficients which may be complex-valued and singular. Each of the articles concerns a different aspect of the problem. Namely, the first article discusses the direct scattering problem in higher dimensions and culminates in a proof of Saito's formula, which yields a uniqueness result for the inverse scattering problem. The second paper is about a backscattering problem in two and three dimensions. We prove that the inverse Born approximation can be used to recover the singularities in the coefficients of the operator. The third article fills in an answer to the question about recovering the complex-valued coefficients in three dimensions that was left open in the second article. The final article studies the inverse scattering problem on the line for a quasi-linear operatorTiivistelmä Väitöskirjatyö koostuu neljästä artikkelista, jotka käsittelevät sirontaongelmia biharmoniselle operaattorille. Työn kohteena olevalla operaattorilla on kaksi kerrointa, jotka voivat olla kompleksiarvoisia ja singulaarisia. Kukin artikkeli käsittelee sirontaongelmaa eri näkökulmasta. Ensimmäinen artikkeli koostuu pääasiassa suorasta sirontateoriasta korkeammissa ulottuvuuksissa huipentuen lopulta Saiton kaavan todistukseen, jonka seurauksena saadaan yksikäsitteisyystulos käänteiselle sirontaongelmalle. Toisen artikkelin aiheena on takaisinsirontaongelma kahdessa ja kolmessa ulottuvuudessa. Todistamme, että käänteistä Bornin approksimaatiota voidaan käyttää paikantamaan kertoimien mahdolliset singulariteetit. Kolmas artikkeli vastaa toisessa artikkelissa avoimeksi jääneeseen kysymykseen kompleksiarvoisien kertoimien rekonstruoimisesta kolmessa ulottuvuudessa. Viimeisessä artikkelissa tutkitaan käänteistä sirontaongelmaa kvasilineaariselle operaattorille yhdessä ulottuvuudessa
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Shi, Qiang. "Sharp estimates of the transmission boundary value problem for dirac operators on non-smooth domains." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4358.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 1, 2007) Vita. Includes bibliographical references.
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Vieira, Nelson Felipe Loureiro. "Theory of the parabolic Dirac operators and its applications to non-linear differential equations." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2924.
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Mbarek, Aiman. "Études théorème d'absorption limite pour les opérateurs de Schrödinger et Dirac avec un potentiel oscillant." Thesis, Cergy-Pontoise, 2017. http://www.theses.fr/2017CERG0839/document.
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Dans cette thèse nous avons étudié, d'une part le théorème d'absorption limitepour des opérateurs de Schrödinger et de Dirac avec des potentiels oscillants. Lefait de considérer des potentiels oscillants est intéressant dans la mesure où ses opé-rateurs peuvent avoir des valeurs propres plongées dans le spectre continu (c'est lecas pour Schrödinger), ce qui est plutôt inhabituel et introduit de nouvelles di-cultés. L'étude du théorème d'absorption limite est très importante pour la théoriede la diffusion. Un intérêt particulier du sujet réside dans le fait que l'outil naturelpour procéder à l'étude en question, à savoir la théorie du commutateur de Mourre,ne s'applique pas. Une alternative récente a été développée par les co-directeurs dela thèse Thierry Jecko et Sylvain Golénia. Elle a été appliquée à un opérateur deSchrödinger avec potentiel oscillant. Il s'agit donc d'améliorer les résultats sur lesopérateurs de Schrödinger et de traiter le cas des opérateurs de Dirac. D'autre part,nous avons montré un résultat de type Helffer-Sjöstrand pour les opérateurs unitaires.Et pour finir, nous avons pu montrer l'existence des valeurs propre plongéespour l'opérateur de Dirac avec des potentiels relativement compact par rapport àl'opérateur de Dirac libre sur son spectre essentielIn this thesis, we have studied the limit absorption theorem for Schrödinger andDirac operators with oscillating potentials. Considering oscillating potentials is interestinginsofar as its operators can have of the eigenvalues plunged into the continuousspectrum (this is the case for Schrödinger), which is rather unusual and introducesnew dificulties. The study of the limit absorption theorem is very important for thetheory of diffusion. A particular interest of the subject lies in the fact that the naturaltool for the study in question, namely the Mourre switch theory, does not apply. Arecent alternative has been developed by the co-directors Thierry Jecko and SylvainGolénia. It has been applied to a Schrödinger operator with oscillating potential. Itis therefore a question of improving the results on the Schrödinger operators and oftreating the case of Dirac operators. Secondly, we have shown a Helffer-Sjöstrandformula for the unit operators and finally we have been able to show the existenceof the eigenvalues plunged for the Dirac operator with relatively compact potentialsrelative to the operator of free Dirac on its essential spectrum
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Smith, Douglas Andrew. "Structure of the QCD vacuum and low-lying eigenmodes of the Wilson-Dirac operator." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/11413.
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This thesis details a study of the vacuum structure of QCD using the tool of lattice gauge theory. Chapter 1 gives an introduction to path integrals, semi-classical approximations to path integrals, instantons, topological charge and instanton phenomenology. Chapter 2 introduces lattice gauge theory and the problems of studying topological charge on the lattice. The cooling method and its pitfalls are discussed and details are given of a study undertaken of under-relaxed cooling. In Chapter 3 the algorithms that were developed to study the instantons on the cooled configurations are discussed. Chapter 4 gives the results for the structure of the vacuum: size distributions, spatial distributions, correlations between charges, and scaling of distributions with the lattice spacing. Chapter 5 discusses an exploratory study of the low-lying eigenmodes of the Wilson-Dirac operator. The zero-modes of both the unimproved and improved operators on cold and heated instantons are calculated and the lattice artefacts investigated. Chapter 6 contains my conclusions and suggestions for future work.
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Kultima, J. (Jaakko). "Direct and inverse scattering problems for quasi-linear biharmonic operator in 3D." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201908272824.
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Abstract. We consider direct and inverse scattering problems for three-dimensional biharmonic operator
\(Hu = ∆^2u + Vu\),
where \(∆\) is the Laplacian and \(V\) is a scalar valued perturbation. The scattering problem for this operator is given as a partial differential equation \(Hu = k^4u\), with a parameter \(k\).
In the direct scattering problem, our goal is to find the solution \(u\) while the perturbation (V\) is known. We also assume that the solution \(u\) can be written as a sum of two functions \(u_{0}\) and \(u_{sc}\), where \(u_{0}\) is a plane wave and \(u_{sc}\) is an outgoing wave in the sense that it satisfies to the Sommerfeld radiation conditions at the infinity. Our approach in this text is to first modify the partial differential equation into an integral equation by using the fundamental solution. Next, we show that this integral equation is solvable, and it has a unique solution. Finally, we prove two main results of this text; an asymptotic formula for the solution with large values of \(x ∈ \mathbb{R}^3\) and Saito’s formula. The asymptotic behaviour of the solution leads us to defining the scattering amplitude.
In the inverse scattering problem, the goal is to gather some information about the unknown perturbation V while the behaviour of the function u is known. With Saito’s formula we obtain two corollaries regarding the inverse scattering problem, namely uniqueness and a representation formula for the function \(V(x, 1)\), when the scattering amplitude is known. We end the text by first defining the inverse Born approximation for both full scattering data and backscattering data. We also discuss some results that have been obtained previously with this approach.
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Tveiten, Ketil. "Period integrals and other direct images of D-modules." Doctoral thesis, Stockholms universitet, Matematiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116790.
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This thesis consists of three papers, each touching on a different aspect of the theory of rings of differential operators and D-modules. In particular, an aim is to provide and make explicit good examples of D-module directimages, which are all but absent in the existing literature.The first paper makes explicit the fact that B-splines (a particular class of piecewise polynomial functions) are solutions to D-module theoretic direct images of a class of D-modules constructed from polytopes.These modules, and their direct images, inherit all the relevant combinatorial structure from the defining polytopes, and as such are extremely well-behaved.The second paper studies the ring of differential operator on a reduced monomial ring (aka. Stanley-Reisner ring), in arbitrary characteristic.The two-sided ideal structure of the ring of differential operators is described in terms of the associated abstract simplicial complex, and several quite different proofs are given.The third paper computes the monodromy of the period integrals of Laurent polynomials about the singular point at the origin. The monodromy is describable in terms of the Newton polytope of the Laurent polynomial, in particular the combinatorial-algebraic operation of mutation plays an important role. Special attention is given to the class of maximally mutable Laurent polynomials, as these are one side of the conjectured correspondance that classifies Fano manifolds via mirror symmetry.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Accepted. Paper 2: Manuscript. Paper 3: Manuscript.
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Savin, Anton, and Boris Sternin. "Eta invariant and parity conditions." Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2008/2586/.
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We give a formula for the η-invariant of odd order operators on even-dimensional manifolds, and for even order operators on odd-dimensional manifolds. Geometric second order operators are found with nontrivial η-invariants. This solves a problem posed by P. Gilkey.
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Leão, Rafael de Freitas 1979. "Auto-valores do operador de Dirac e do laplaciano de Dobeault." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306021.
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Orientador: Marcos Benevenuto JardimTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
Made available in DSpace on 2018-08-08T16:20:15Z (GMT). No. of bitstreams: 1 Leao_RafaeldeFreitas_D.pdf: 1758484 bytes, checksum: a1d5ed8e2a4224e43550ff157cc3a680 (MD5) Previous issue date: 2007
Resumo: Nesta tese estudamos basicamente como o acoplamento por uma conexão arbitraria influencia o comportamento do espectro do operador de Dirac, real e complexo. Atraves dos resultados classicos da literatura, e destes resultados vemos que, de modo geral, estruturas geometricas influenciam o espectro do operador de Dirac, acoplado ou não. Embora exista uma grande literatura a respeito de estruturas geometricas e o operador de Dirac, sobretudo para o operador não acoplado, existem alguns casos, possivelmente bastante interessantes, que não foram considerados. Com o recente desenvolvimento de geometria complexa generalizada, podemos nos perguntar sobre a possibilidade de definirmos operadores de Dirac neste contexto e se isto traz resultados novos ou entendimento sobre resultados ja conhecidos. Por se tratar de uma area recente existem varios problemas envolvidos na tentativa de estudarmos operadores de Dirac sobre variedades com estruturas complexas generalizadas. O proprio conceito de conexão para este tipo de geometria ainda não e muito claro, uma vez que não assumimos a priori uma metrica na variedade base não podemos considerar a conexão Levi-Civita, ficando a pergunta que se neste contexto existe alguma conexão natural analoga a conexão de Levi-Civita. Outra questão importante e com relação ao fibrado de spinores. No caso de variedades riemannianas a maneira mais usual de construirmos fibrados de Dirac e atraves de uma estrutura Spin na variedade base. Porem este tipo de estrutura tambem e definida em termos de uma metrica ficando a pergunta de como poderíamos construir fibrados de Dirac de maneira natural sobre uma variedade complexa generalizada. Caso seja possível respondermos estas questões podemos falar em operadores de Dirac sobre variedades complexas generalizadas. Podendo, a partir dai, investigar formulas do tipo Weitzenbock e o comportamento do espectro do operador de Dirac. Alem disso podemos nos perguntar se este tipo de operador e de fato um objeto totalmente novo ou se o mesmo se relaciona com operadores conhecidos da variedade base. Outro situação pouco explorada na literatura e a de operadores de Dirac sobre variedades algebricas imersas em CPn. Na literatura existem artigos, [5, 16], que exploram sobretudo estruturas Spin e spinores. Mas não existe tentativas de usar explicitamente que certas variedades podem ser consideradas como variedades algebricas imersas em CPn para tentar obter estimativas mais finas para o espectro do operador de Dirac, como por exemplo e feito para subvariedades Lagrangianas em [8]. Para considerarmos este problema devemos entender como considerar explicitamente que estamos lidando com variedades algebricas imersas em CPn. É possível que existam duas formas de fazermos isto. A primeira e aparentemente mais direta e considerar a imersão em si, na linha do que foi feito com subvariedades Lagrangianas em [8], e estudar propriedades da mesma. Para fazermos isto é possiível que tenhamos que restringir a classe de variedades em questão. A segunda forma, que parece ser um pouco mais delicada, é tentar escrever o operador de Dirac de forma a levar em consideração a estrutura algebrica da variedade. Pode ser possível que escrevendo o operador de Dirac na linguagem algebrica obtenhamos informações que nos permitirão encontrar estimativas para o espectro do mesmo
Abstract: Not informed.
Doutorado
Geometria
Doutor em Matemática
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Becker-Bender, Julia [Verfasser], and Ilka [Akademischer Betreuer] Agricola. "Dirac-Operatoren und Killing-Spinoren mit Torsion / Julia Becker-Bender. Betreuer: Ilka Agricola." Marburg : Philipps-Universität Marburg, 2013. http://d-nb.info/103231477X/34.
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Müller, David [Verfasser], and Heinz [Akademischer Betreuer] Siedentop. "Projizierte gestörte Coulomb-Dirac-Operatoren und ihre Eigenwerte / David Müller ; Betreuer: Heinz Siedentop." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1164376950/34.
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Esfahani, Zadeh Mostafa. "A family index theorem for foliated manifolds with boundary." Paris 7, 2005. http://www.theses.fr/2005PA077138.
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Tyni, T. (Teemu). "Direct and inverse scattering problems for operator of order 4 on the line." Master's thesis, University of Oulu, 2015. http://jultika.oulu.fi/Record/nbnfioulu-201505091502.
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Abstract. We study both the direct and the inverse scattering problems for a differential operator of order 4 on the line. In the direct scattering problem we start by forming a differential equation from our operator. By applying the fundamental solution of the differential operator we turn the differential equation into an integral equation, and proceed to solve it.
Having found the solution to the integral equation we study the asymptotic behaviour of the solution. We conclude the study of the direct scattering problem by defining so called transmission and reflection coefficients, that are needed to solve the inverse scattering problem.
In the inverse scattering problem we simplify the operator by choosing its coefficients suitably. It turns out that the operator includes one interesting potential function V. The inverse problem is formulated as follows: find and construct the jumps and singularities of the potential V. By using the reflection coefficient defined previously we define the so called inverse Born approximation V_B. We prove that the difference V-V_B is a continuous function. This means that the jumps and singularities of potential V can be found by calculating V_B.Suora ja käänteinen sirontaongelma neljännen kertaluvun operaattorille. Tiivistelmä. Työssä tutkitaan sekä suoraa että käänteistä sirontaongelmaa neljännen kertaluvun differentiaalioperaattorille. Suorassa sirontaongelmassa käytämme operaattoria muodostaaksemme differentiaaliyhtälön. Soveltaen operaattorin perusratkaisua, voimme muuntaa differentiaaliyhtälön integraaliyhtälöksi ja ratkaista sen.
Kun integraaliyhtälön ratkaisu on löydetty, tutkimme sen asymptoottista käyttäytymistä. Päätämme suoran sirontaongelman tarkastelun määrittelemällä asymptoottien avulla ns. välitys- ja heijastuskertoimet, joita tarvitaan käänteisen sirontaongelman ratkaisussa.
Käänteisessä sirontaongelmassa yksinkertaistamme operaattoria hieman. Käy ilmi, että operaattori sisältää tällöin yhden kiinnostavan potentiaalifunktion V. Käänteisen sirontaongelman asettelu on seuraava: etsi potentiaalin V mahdolliset hyppyepäjatkuvuudet ja singulariteetit, kun heijastuskerroin on tunnettu. Heijastuskertoimen avulla voimme määritellä ns. käänteisen Bornin approksimaation V_B. Osoitamme, että erotus V-V_B on jatkuva funktio. Tällöin potentiaalin V hypyt ja singulariteetit voidaan löytää laskemalla V_B.
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Stadtmüller, Christoph Martin [Verfasser], Helga [Gutachter] Baum, Bernd [Gutachter] Ammann, and Uwe [Gutachter] Semmelmann. "Horizontal Dirac Operators in CR Geometry / Christoph Martin Stadtmüller ; Gutachter: Helga Baum, Bernd Ammann, Uwe Semmelmann." Berlin : Humboldt-Universität zu Berlin, 2017. http://d-nb.info/1189326345/34.
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Buggisch, Lukas Werner [Verfasser], and Johannes [Akademischer Betreuer] Ebert. "The spectral flow theorem for families of twisted Dirac operators / Lukas Werner Buggisch ; Betreuer: Johannes Ebert." Münster : Universitäts- und Landesbibliothek Münster, 2019. http://d-nb.info/1190724960/34.
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