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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 161 for “"Heisenberg"”.
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Magnetic properties of Heisenberg antiferromagnetic EuTe/PbTe superlattices
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1996.
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Quantum mechanical studies of Heisenberg antiferromagnetic spin chains
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1999.
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On the Phase Diagram of the Heisenberg Gamma Ladder
… components, mediated by $\Gamma$, along with a Heisenberg interaction controlled by $J$. By parameterizing these couplings by an angle $\phi$, we produce a phase diagram of the system using the Infinite Density Matrix Renormalization Group (iDMRG) numerical technique. In order to classify the …
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Untersuchungen zu uniaxial anisotropen Heisenberg-Antiferromagneten in zwei Dimensionen
… two-dimensional Ising and anisotropic Heisenberg models have been studied. Ising models with mobile and pinned defects are shown to describe the formation and thermal destruction of defect stripes. Modelling a specific "telephone number compound", a realistic Heisenberg model with …
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Laplacians on Nonisotropic Heisenberg Groups with Multi-Dimensional Center
… begin with the construction of the nonisotropic Heisenberg group with multi- dimensional center. The sub-Laplacian on it is introduced. By taking the inverse Fourier transform of the sub-Laplacian with respect to the center, we get a family of twisted Laplacians. They are proved to be globally …
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Projections, slicings and Fourier transforms in the Heisenberg group
… study of projection and slicing problems in the Heisenberg group from the point of view of Hausdorff dimension distortion. It then gives a short summary of research done in this area up to date before introducing and explaining my own contributions to it. Finally, the group Fourier transform in …
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Grundzustandseigenschaften von anisotropen antiferromagnetischen Heisenberg-Ketten mit Spin S = 1
In this thesis ground state properties of S = 1 spin chains with exchange and single-ion anisotropy are analysed. Following earlier publications two cases are mainly considered: A fixed ratio of the two anisotropies as well as a fixed and strong exchange anisotropy. The method primarily employed is …
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Weyl Pseudodifferential Calculus and the Heisenberg Group in New Settings
… both Weyl pseudodifferential calculus and the Heisenberg group in new settings, through two published papers and a chapter representing work towards a construction of Haar bases of unimodular LC groups. We finish with some remarks about an extension of both Heisenberg group and …
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High-temperature critical indices for the classical anisotropic Heisenberg model
The classical anisotropic Heisenberg model is studied by means of high-temperature expansions. The purpose of the work is to determine (in the context of the model) how many phase transitions (as characterized by the critical exponents) there are, and which features of the dynamics and kinematics …
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Von Neumann algebras, affiliated operators and representations of the Heisenberg relation
… Neumann algebra never form such an algebra. The Heisenberg commutation relation, QP -- PQ = --ihI , is the most fundamental relation of quantum mechanics. Heisenberg's encoding of the ad-hoc quantum rules in this simple relation embodies the characteristic indeterminacy and uncertainty of quantum …
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Spin Dynamics in a Tunable Heisenberg Magnet Realized with Ultracold Atoms
… interactions. This system is described by the Heisenberg model, a paradigmatic model, which has been studied for almost a century now. But so far, experiments on spin dynamics have been mostly limited to isotropic spin-spin interactions. In this work we use ultracold atoms to implement the …
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Intrinsic Lipschitz graphs in Heisenberg groups and non linear sub-elliptic PDEs
… Moreover we study the obstacle problem in the Heisenberg group and we prove a geometric Poincarè inequality for a class of semilinear equations in the Engel group.
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Adams inequalities with exact growth condition : on Rn and the Heisenberg group
… equation. Lastly, we extend our result to the Heisenberg group. By applying the same technique used in R[superscript n], we derive a sharp Adams inequality with critical growth condition on H[superscript n] for integral operators whose kernels are strictly Riesz-like on H[superscript n]. As a …
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Dynamics of vortices in the two-dimensional anisotropic Heisenberg model with magnetic fields.
The subject of this work is the dynamics of a vortex in a classical 2-dimensional spin system with anisotropic exchange interaction under the combined action of magnetic fields and damping. Static as well as dynamic magnetic fields were employed (as dynamical field we used a homogeneous field which …
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From Homological Algebra To Topology via Type B Zigzag Algebra and Heisenberg Algebra
… $\Z[t,t^{-1}]$ for a crossingless matching using Heisenberg algebra. We conjecture that the span of such vectors forms a Temperley-Lieb representation, and hence, a new presentation of Jones polynomial can be obtained.
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From Homological Algebra To Topology via Type B Zigzag Algebra and Heisenberg Algebra
… $\Z[t,t^{-1}]$ for a crossingless matching using Heisenberg algebra. We conjecture that the span of such vectors forms a Temperley-Lieb representation, and hence, a new presentation of Jones polynomial can be obtained.
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Geometric mapping theory of the Heisenberg group, sub-Riemannian manifolds, and hyperbolic spaces
We discuss the Heisenberg group $\Heis^n$ and its mappings from three perspectives. As a nilpotent Lie group, $\Heis^n$ can be viewed as a generalization of the real numbers, leading to new notions of base-$b$ expansions and continued fractions. As a metric space, $\Heis^n$ serves as an …
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