We discuss how BMM affects the large cardinal
structure of V as well as the size of \theta^{L(R)}. BMM proves
that V is closed under sharps (and more), and BMM plus the
existence of a precipitous ideal on \omega_1 proves that
\delta^1_2 = \aleph_2. Part of this is joint work with my
student Ben Claverie.
For an uncountable graph $X$ let $S(X)$ denote
the set of chromatic numbers of subgraphs of $X$
and $I(X)$ the analogous set for induced subgraphs.
We investigate the properties of $I(X)$ and $S(X)$.
The talk deals with the spectral analysis of Jacobi matrices superimposed
with random perturbations that decay in a certain sense.
We shall focus our attention on two problems: The first is the analysis of
spectral stability. We show that the absolutely continuous spectrum
associated with bounded generalized eigenfunctions, for Jacobi matrices with
a mild growth restriction on the off-diagonal terms, is stable under random
Hilbert-Schmidt perturbations. We also give some results for singular
spectral types. This is joint work with Yoram Last.
The second problem is the spectral analysis of Jacobi matrices arising in
the study of Gaussian \beta ensembles of Random Matrix Theory. These
matrices may be viewed as simple Jacobi matrices (with growing off-diagonal
terms) with a random perturbation that decays in a certain sense. With the
help of the appropriately modified methods, we analyze the behavior of the
generalized eigenfunctions and the Hausdorff dimension of the spectral
measure. Some of this work is joint with Peter Forrester and Uzy Smilansky.
In this talk I will present some recent results
on perturbations of almost-periodic Jacobi matrices with a
finite number of gaps in the spectrum. In particular, I will
discuss a Szego-type theorem which provides a description of
all Jacobi matrices with spectral measures satisfying a
Szego-type condition. I will also address a limit almost
periodic behavior of coefficients for such Jacobi matrices.
This talk is based on joint work in progress with Jacob
Christiansen and Barry Simon.
A non-zero Abelian differential in a compact Riemann surface of genus $g \geq 1$ endows the surface with an atlas (outside the zeroes) whose coordinate changes are translations. There is a natural ``vertical flow'' (moving up with unit speed) associated with the translation structure, generalizing the genus $1$ case of irrational flows on the torus.
The Teichm\"uller flow in the moduli space of Abelian differentials can be seen as the renormalization operator of translation flows. In this talk, we will discuss how the chaoticity of the Teichm\"uller flow dynamics reflects on the (non-chaotic) dynamics of the associated vertical flows (for typical parameters), and the closely related interval exchange transformations.
We collect together a number of examples of random walk
where the characteristic function of the first step has a
singularity at the point t=0. The function \log\varphi(t) has
two different expansions for positive and negative $t$ near the
origin; we call the coefficients of these expansions left and
right quasicumulants. Such examples include the trace of a
two dimensional random walk {(X_n,Y_n)} on the x-axis, and the
subordinated random walk (X_{\tau_n}) where (\tau_n) is an
appropriate sequence of random times. Using quasicumulants we derive an asymptotic expansion for the distribution of the sums of i.i.d. random variables, and assuming
further differentiability condition we are able to give sharp
estimate in the variable x of the remainder term.
We survey the general methodology in developing asymptotic preserving schemes for physical problems with multiple spatial and temporal scales. These schemes are first-principle based, and automatically become macroscopic solvers when the microscoipic scales are not resolved numerically. They avoid the coupling of models of different
scales, thus do not face the difficult task of transfering data from one scale to the other as in most multiscale methods. These schemes are very effective for the coupling of kinetic and hydrodynamic equations, and problems with fast reactions.
Classical ideal fluid motion is described by Euler and Navier-Stokes equations. For real fluids, their motions are more complicated and governed by Euler and Navier-Stokes equations coupled with various constitutive equations. We study viscoelastic models whose motions are
carried out by the competition between the kinetic energies and internal elastic energies. The deformation tensor plays an essential role in our studies. We will present how to use the heuristics coming from the special
structure of the deformation tensor to establish the global well-posedness results for several viscoelastic models, but will focus on a 2D Strain-Rotation model.
In this talk, I will present recent results on wave localization in nonlinear random media in the frame work of the stochastic Gross-Pitaevskii equation (describing Bose-Einstein condensation). In particular, it is shown numerically that the disorder average spatial extension of the stationary density profile decreases with
an increasing strength of the disordered potential both for repulsive and attractive interactions.