A Geometric Theory for Hypergraph Matching
A Geometric Theory for Hypergraph Matching

Author: Peter Keevash

Publisher: American Mathematical Soc.

Published: 2014-12-20

Total Pages: 108

ISBN-13: 1470409658

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The authors develop a theory for the existence of perfect matchings in hypergraphs under quite general conditions. Informally speaking, the obstructions to perfect matchings are geometric, and are of two distinct types: `space barriers' from convex geometry, and `divisibility barriers' from arithmetic lattice-based constructions. To formulate precise results, they introduce the setting of simplicial complexes with minimum degree sequences, which is a generalisation of the usual minimum degree condition. They determine the essentially best possible minimum degree sequence for finding an almost perfect matching. Furthermore, their main result establishes the stability property: under the same degree assumption, if there is no perfect matching then there must be a space or divisibility barrier. This allows the use of the stability method in proving exact results. Besides recovering previous results, the authors apply our theory to the solution of two open problems on hypergraph packings: the minimum degree threshold for packing tetrahedra in -graphs, and Fischer's conjecture on a multipartite form of the Hajnal-Szemerédi Theorem. Here they prove the exact result for tetrahedra and the asymptotic result for Fischer's conjecture; since the exact result for the latter is technical they defer it to a subsequent paper.

Recent Trends in Combinatorics
Recent Trends in Combinatorics

Author: Andrew Beveridge

Publisher: Springer

Published: 2016-04-12

Total Pages: 775

ISBN-13: 3319242989

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This volume presents some of the research topics discussed at the 2014-2015 Annual Thematic Program Discrete Structures: Analysis and Applications at the Institute for Mathematics and its Applications during Fall 2014, when combinatorics was the focus. Leading experts have written surveys of research problems, making state of the art results more conveniently and widely available. The three-part structure of the volume reflects the three workshops held during Fall 2014. In the first part, topics on extremal and probabilistic combinatorics are presented; part two focuses on additive and analytic combinatorics; and part three presents topics in geometric and enumerative combinatorics. This book will be of use to those who research combinatorics directly or apply combinatorial methods to other fields.

Theory and Applications of Models of Computation
Theory and Applications of Models of Computation

Author: T.V. Gopal

Publisher: Springer

Published: 2017-04-13

Total Pages: 722

ISBN-13: 3319559117

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This book constitutes the refereed proceedings of the 14th Annual Conference on Theory and Applications of Models of Computation, TAMC 2017, held in Bern, Switzerland, in April 2017. The 45 revised full papers presented together with 4 invited papers were carefully reviewed and selected from 103 submissions. The main themes of TAMC 2017 have been computability, computer science logic, complexity, algorithms, and models of computation and systems theory.

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.

The Seventh European Conference on Combinatorics, Graph Theory and Applications
The Seventh European Conference on Combinatorics, Graph Theory and Applications

Author: Jaroslav Nešetřil

Publisher: Springer Science & Business Media

Published: 2014-01-18

Total Pages: 612

ISBN-13: 887642475X

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In the tradition of EuroComb'01 (Barcelona), Eurocomb'03 (Prague), EuroComb'05 (Berlin), Eurocomb'07 (Seville), Eurocomb'09 (Bordeaux), and Eurocomb'11 (Budapest), this volume covers recent advances in combinatorics and graph theory including applications in other areas of mathematics, computer science and engineering. Topics include, but are not limited to: Algebraic combinatorics, combinatorial geometry, combinatorial number theory, combinatorial optimization, designs and configurations, enumerative combinatorics, extremal combinatorics, ordered sets, random methods, topological combinatorics.

Poincare-Einstein Holography for Forms via Conformal Geometry in the Bulk
Poincare-Einstein Holography for Forms via Conformal Geometry in the Bulk

Author: A. Rod Gover

Publisher: American Mathematical Soc.

Published: 2015-04-09

Total Pages: 108

ISBN-13: 1470410923

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The authors study higher form Proca equations on Einstein manifolds with boundary data along conformal infinity. They solve these Laplace-type boundary problems formally, and to all orders, by constructing an operator which projects arbitrary forms to solutions. They also develop a product formula for solving these asymptotic problems in general. The central tools of their approach are (i) the conformal geometry of differential forms and the associated exterior tractor calculus, and (ii) a generalised notion of scale which encodes the connection between the underlying geometry and its boundary. The latter also controls the breaking of conformal invariance in a very strict way by coupling conformally invariant equations to the scale tractor associated with the generalised scale.

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 .

Deformation Theory and Local-Global Compatibility of Langlands Correspondences
Deformation Theory and Local-Global Compatibility of Langlands Correspondences

Author: Martin Luu

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 116

ISBN-13: 1470414228

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The deformation theory of automorphic representations is used to study local properties of Galois representations associated to automorphic representations of general linear groups and symplectic groups. In some cases this allows to identify the local Galois representations with representations predicted by a local Langlands correspondence.

On the Theory of Weak Turbulence for the Nonlinear Schrodinger Equation
On the Theory of Weak Turbulence for the Nonlinear Schrodinger Equation

Author: M. Escobedo

Publisher: American Mathematical Soc.

Published: 2015-10-27

Total Pages: 120

ISBN-13: 1470414341

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The authors study the Cauchy problem for a kinetic equation arising in the weak turbulence theory for the cubic nonlinear Schrödinger equation. They define suitable concepts of weak and mild solutions and prove local and global well posedness results. Several qualitative properties of the solutions, including long time asymptotics, blow up results and condensation in finite time are obtained. The authors also prove the existence of a family of solutions that exhibit pulsating behavior.

On the Differential Structure of Metric Measure Spaces and Applications
On the Differential Structure of Metric Measure Spaces and Applications

Author: Nicola Gigli

Publisher: American Mathematical Soc.

Published: 2015-06-26

Total Pages: 104

ISBN-13: 1470414201

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The main goals of this paper are: (i) To develop an abstract differential calculus on metric measure spaces by investigating the duality relations between differentials and gradients of Sobolev functions. This will be achieved without calling into play any sort of analysis in charts, our assumptions being: the metric space is complete and separable and the measure is Radon and non-negative. (ii) To employ these notions of calculus to provide, via integration by parts, a general definition of distributional Laplacian, thus giving a meaning to an expression like , where is a function and is a measure. (iii) To show that on spaces with Ricci curvature bounded from below and dimension bounded from above, the Laplacian of the distance function is always a measure and that this measure has the standard sharp comparison properties. This result requires an additional assumption on the space, which reduces to strict convexity of the norm in the case of smooth Finsler structures and is always satisfied on spaces with linear Laplacian, a situation which is analyzed in detail.