Entropy and the Central Limit Theorem

Speaker: 

Professor Nicolai Haydn

Institution: 

USC

Time: 

Tuesday, February 24, 2009 - 3:00pm

Location: 

RH 440 R

For an ergodic system, the theorem of Shannon-McMillan-Breiman states that for every finite generating partition the exponential decay rate of the measure of cylinder sets equals the metric entropy almost everywhere. In 1962 Ibragimov showed that the distribution of the measure of cylinder sets is lognormally distributed provided the measure is strong mixing and its conditional entropy function is sufficiently well approximable.
Carleson (1958) and Chung (1960) generalised the theorem of SMB to infinite partitions (provided the entropy is finite). We show that the measures of cylinder sets are lognormally distributed for uniformly strong mixing systems and infinite partitions and show that the rate of convergence is polynomial. Apart from the mixing property we require that a higher than fourth moment of the information function is finite. Also, unlike previous results by Ibragimov and others which only apply to finite partitions, here we do not require any regularity of the conditional entropy function. We also obtain the law of the iterated logarithm and the weak invariance principle for the information function.

"Continuum limits for beta ensembles"

Speaker: 

Professor Brian Rider

Institution: 

University of Colorado

Time: 

Tuesday, March 3, 2009 - 11:00am

Location: 

RH 306

The beta ensembles of random matrix theory are natural generalizations of the Gaussian Orthogonal, Unitary, and Symplectic Ensembles, these classical cases corresponding to beta = 1, 2, and 4. We prove that the extremal eigenvalues for the general ensembles have limit laws described by the low lying spectrum of certain raandom Schroedinger operators, as conjectured by Edelman-Sutton. As a corollary, a second characterization of these laws is made the explosion probability of a simple one-dimensional diffusion. A complementary pictures is developed for beta versions of random sample-covariance matrices. (Based on work with J. Ramirez and B. Virag.)

On Arithmetic in Mordell-Weil groups

Speaker: 

Grzegorz Banaszak

Institution: 

Adam Mickiewicz University, Poznan, Poland

Time: 

Tuesday, April 21, 2009 - 2:00pm

Location: 

RH 306

Let $A/F$ be an abelian variety over a number field F, let $P \in A(F)$ and $\Lambda \subset A(F)$ be a subgroup of the Mordell-Weil group. For a prime $v$ of good reduction let $r_v : A(F) \rightarrow A_v(k_v)$ be the reduction map. During my talk I will show that the condition $r_v(P) \in r_v(\Lambda)$ for almost all primes $v$ imply that $P \in \Lambda + A(F)_{tor}$ for a wide class of abelian varieties.

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