Julia Sets and Complex Singularities of Free Energies
Julia Sets and Complex Singularities of Free Energies

Author: Jianyong Qiao

Publisher: American Mathematical Soc.

Published: 2015-02-06

Total Pages: 102

ISBN-13: 1470409828

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The author studies a family of renormalization transformations of generalized diamond hierarchical Potts models through complex dynamical systems. He proves that the Julia set (unstable set) of a renormalization transformation, when it is treated as a complex dynamical system, is the set of complex singularities of the free energy in statistical mechanics. He gives a sufficient and necessary condition for the Julia sets to be disconnected. Furthermore, he proves that all Fatou components (components of the stable sets) of this family of renormalization transformations are Jordan domains with at most one exception which is completely invariant. In view of the problem in physics about the distribution of these complex singularities, the author proves here a new type of distribution: the set of these complex singularities in the real temperature domain could contain an interval. Finally, the author studies the boundary behavior of the first derivative and second derivative of the free energy on the Fatou component containing the infinity. He also gives an explicit value of the second order critical exponent of the free energy for almost every boundary point.

On the Singular Set of Harmonic Maps into DM-Complexes
On the Singular Set of Harmonic Maps into DM-Complexes

Author: Georgios Daskalopoulos

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 102

ISBN-13: 1470414600

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The authors prove that the singular set of a harmonic map from a smooth Riemammian domain to a Riemannian DM-complex is of Hausdorff codimension at least two. They also explore monotonicity formulas and an order gap theorem for approximately harmonic maps. These regularity results have applications to rigidity problems examined in subsequent articles.

Geometric Complexity Theory IV: Nonstandard Quantum Group for the Kronecker Problem
Geometric Complexity Theory IV: Nonstandard Quantum Group for the Kronecker Problem

Author: Jonah Blasiak

Publisher: American Mathematical Soc.

Published: 2015-04-09

Total Pages: 176

ISBN-13: 1470410117

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The Kronecker coefficient is the multiplicity of the -irreducible in the restriction of the -irreducible via the natural map , where are -vector spaces and . A fundamental open problem in algebraic combinatorics is to find a positive combinatorial formula for these coefficients. The authors construct two quantum objects for this problem, which they call the nonstandard quantum group and nonstandard Hecke algebra. They show that the nonstandard quantum group has a compact real form and its representations are completely reducible, that the nonstandard Hecke algebra is semisimple, and that they satisfy an analog of quantum Schur-Weyl duality.

Higher Moments of Banach Space Valued Random Variables
Higher Moments of Banach Space Valued Random Variables

Author: Svante Janson

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 124

ISBN-13: 1470414651

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The authors define the :th moment of a Banach space valued random variable as the expectation of its :th tensor power; thus the moment (if it exists) is an element of a tensor power of the original Banach space. The authors study both the projective and injective tensor products, and their relation. Moreover, in order to be general and flexible, we study three different types of expectations: Bochner integrals, Pettis integrals and Dunford integrals.

Global Carleman Estimates for Degenerate Parabolic Operators with Applications
Global Carleman Estimates for Degenerate Parabolic Operators with Applications

Author: P. Cannarsa

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 225

ISBN-13: 1470414961

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Degenerate parabolic operators have received increasing attention in recent years because they are associated with both important theoretical analysis, such as stochastic diffusion processes, and interesting applications to engineering, physics, biology, and economics. This manuscript has been conceived to introduce the reader to global Carleman estimates for a class of parabolic operators which may degenerate at the boundary of the space domain, in the normal direction to the boundary. Such a kind of degeneracy is relevant to study the invariance of a domain with respect to a given stochastic diffusion flow, and appears naturally in climatology models.

Irreducible Geometric Subgroups of Classical Algebraic Groups
Irreducible Geometric Subgroups of Classical Algebraic Groups

Author: Timothy C. Burness,

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 100

ISBN-13: 1470414945

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Let be a simple classical algebraic group over an algebraically closed field of characteristic with natural module . Let be a closed subgroup of and let be a non-trivial irreducible tensor-indecomposable -restricted rational -module such that the restriction of to is irreducible. In this paper the authors classify the triples of this form, where is a disconnected maximal positive-dimensional closed subgroup of preserving a natural geometric structure on .

Stability of Line Solitons for the KP-II Equation in $\mathbb {R}^2$
Stability of Line Solitons for the KP-II Equation in $\mathbb {R}^2$

Author: Tetsu Mizumachi

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 110

ISBN-13: 1470414244

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The author proves nonlinear stability of line soliton solutions of the KP-II equation with respect to transverse perturbations that are exponentially localized as . He finds that the amplitude of the line soliton converges to that of the line soliton at initial time whereas jumps of the local phase shift of the crest propagate in a finite speed toward . The local amplitude and the phase shift of the crest of the line solitons are described by a system of 1D wave equations with diffraction terms.

Faithfully Quadratic Rings
Faithfully Quadratic Rings

Author: M. Dickmann

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 148

ISBN-13: 1470414686

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In this monograph the authors extend the classical algebraic theory of quadratic forms over fields to diagonal quadratic forms with invertible entries over broad classes of commutative, unitary rings where is not a sum of squares and is invertible. They accomplish this by: (1) Extending the classical notion of matrix isometry of forms to a suitable notion of -isometry, where is a preorder of the given ring, , or . (2) Introducing in this context three axioms expressing simple properties of (value) representation of elements of the ring by quadratic forms, well-known to hold in the field case.

Stability of KAM Tori for Nonlinear Schrödinger Equation
Stability of KAM Tori for Nonlinear Schrödinger Equation

Author: Hongzi Cong

Publisher: American Mathematical Soc.

Published: 2016-01-25

Total Pages: 100

ISBN-13: 1470416573

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The authors prove the long time stability of KAM tori (thus quasi-periodic solutions) for nonlinear Schrödinger equation subject to Dirichlet boundary conditions , where is a real Fourier multiplier. More precisely, they show that, for a typical Fourier multiplier , any solution with the initial datum in the -neighborhood of a KAM torus still stays in the -neighborhood of the KAM torus for a polynomial long time such as for any given with , where is a constant depending on and as .