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On the Splitting of Invariant Manifolds in Multidimensional Near-Integrable Hamiltonian Systems
  • Language: en
  • Pages: 162

On the Splitting of Invariant Manifolds in Multidimensional Near-Integrable Hamiltonian Systems

Presents the problem of the splitting of invariant manifolds in multidimensional Hamiltonian systems, stressing the canonical features of the problem. This book offers introduction of a canonically invariant scheme for the computation of the splitting matrix.

Sum Formula for SL$_2$ over a Totally Real Number Field
  • Language: en
  • Pages: 96

Sum Formula for SL$_2$ over a Totally Real Number Field

The authors prove a general form of the sum formula $\mathrm{SL}_2$ over a totally real number field. This formula relates sums of Kloosterman sums to products of Fourier coefficients of automorphic representations. The authors give two versions: the spectral sum formula (in short: sum formula) and the Kloosterman sum formula. They have the independent test function in the spectral term, in the sum of Kloosterman sums, respectively.

Rank One Higgs Bundles and Representations of Fundamental Groups of Riemann Surfaces
  • Language: en
  • Pages: 86

Rank One Higgs Bundles and Representations of Fundamental Groups of Riemann Surfaces

This expository article details the theory of rank one Higgs bundles over a closed Riemann surface $X$ and their relation to representations of the fundamental group of $X$. The authors construct an equivalence between the deformation theories of flat connections and Higgs pairs. This provides an identification of moduli spaces arising in different contexts. The moduli spaces are real Lie groups. From each context arises a complex structure, and the different complex structures define a hyperkähler structure. The twistor space, real forms, and various group actions are computed explicitly in terms of the Jacobian of $X$. The authors describe the moduli spaces and their geometry in terms of the Riemann period matrix of $X$.

Canonical Wick Rotations in 3-Dimensional Gravity
  • Language: en
  • Pages: 181

Canonical Wick Rotations in 3-Dimensional Gravity

The authors develop a canonical Wick rotation-rescaling theory in $3$-dimensional gravity. This includes (a) A simultaneous classification: this shows how maximal globally hyperbolic spacetimes of arbitrary constant curvature, which admit a complete Cauchy surface and canonical cosmological time, as well as complex projective structures on arbitrary surfaces, are all different materializations of ``more fundamental'' encoding structures. (b) Canonical geometric correlations: this shows how spacetimes of different curvature, that share a same encoding structure, are related to each other by canonical rescalings, and how they can be transformed by canonical Wick rotations in hyperbolic $3$-manifolds, that carry the appropriate asymptotic projective structure. Both Wick rotations and rescalings act along the canonical cosmological time and have universal rescaling functions. These correlations are functorial with respect to isomorphisms of the respective geometric categories.

The Recognition Theorem for Graded Lie Algebras in Prime Characteristic
  • Language: en
  • Pages: 164

The Recognition Theorem for Graded Lie Algebras in Prime Characteristic

"Volume 197, number 920 (second of 5 numbers)."

Index Theory, Eta Forms, and Deligne Cohomology
  • Language: en
  • Pages: 134

Index Theory, Eta Forms, and Deligne Cohomology

This paper sets up a language to deal with Dirac operators on manifolds with corners of arbitrary codimension. In particular the author develops a precise theory of boundary reductions. The author introduces the notion of a taming of a Dirac operator as an invertible perturbation by a smoothing operator. Given a Dirac operator on a manifold with boundary faces the author uses the tamings of its boundary reductions in order to turn the operator into a Fredholm operator. Its index is an obstruction against extending the taming from the boundary to the interior. In this way he develops an inductive procedure to associate Fredholm operators to Dirac operators on manifolds with corners and develops the associated obstruction theory.

Brownian Brownian Motion-I
  • Language: en
  • Pages: 208

Brownian Brownian Motion-I

A classical model of Brownian motion consists of a heavy molecule submerged into a gas of light atoms in a closed container. In this work the authors study a 2D version of this model, where the molecule is a heavy disk of mass $M \gg 1$ and the gas is represented by just one point particle of mass $m=1$, which interacts with the disk and the walls of the container via elastic collisions. Chaotic behavior of the particles is ensured by convex (scattering) walls of the container. The authors prove that the position and velocity of the disk, in an appropriate time scale, converge, as $M\to\infty$, to a Brownian motion (possibly, inhomogeneous); the scaling regime and the structure of the limit process depend on the initial conditions. The proofs are based on strong hyperbolicity of the underlying dynamics, fast decay of correlations in systems with elastic collisions (billiards), and methods of averaging theory.

The Mapping Class Group from the Viewpoint of Measure Equivalence Theory
  • Language: en
  • Pages: 206

The Mapping Class Group from the Viewpoint of Measure Equivalence Theory

The author obtains some classification result for the mapping class groups of compact orientable surfaces in terms of measure equivalence. In particular, the mapping class groups of different closed surfaces cannot be measure equivalent. Moreover, the author gives various examples of discrete groups which are not measure equivalent to the mapping class groups. In the course of the proof, the author investigates amenability in a measurable sense for the actions of the mapping class group on the boundary at infinity of the curve complex and on the Thurston boundary and, using this investigation, proves that the mapping class group of a compact orientable surface is exact.

Limit Theorems of Polynomial Approximation with Exponential Weights
  • Language: en
  • Pages: 178

Limit Theorems of Polynomial Approximation with Exponential Weights

The author develops the limit relations between the errors of polynomial approximation in weighted metrics and apply them to various problems in approximation theory such as asymptotically best constants, convergence of polynomials, approximation of individual functions, and multidimensional limit theorems of polynomial approximation.

The Stable Manifold Theorem for Semilinear Stochastic Evolution Equations and Stochastic Partial Differential Equations
  • Language: en
  • Pages: 120

The Stable Manifold Theorem for Semilinear Stochastic Evolution Equations and Stochastic Partial Differential Equations

The main objective of this paper is to characterize the pathwise local structure of solutions of semilinear stochastic evolution equations and stochastic partial differential equations near stationary solutions.