# Events for October 18, 2017 from General and Seminar calendars

## Postdoc Lunch Time Talks

**Time:** 12:00PM - 12:20PM

**Location:** BLOC 220

**Speaker:** Cong Gu, Texas A&M University

**Description:**Title: Iterative Scaling Method for Numerical Solution of Kirchhoff-type Problems

Abstract: Kirchhoff-type problems considered here are quasilinear elliptic PDEs that involve the H1-norm of the solution as a perturbation to the coefficients. An implicit scaling iterative algorithm is proposed to numerically solve such problems. Some desirable properties of the algorithm are proved. The numerical solutions obtained can help with the understanding of such problems in areas like the sharpness of analytical results.

## Postdoc Lunch Time Talks

**Time:** 12:35PM - 12:55PM

**Location:** BLOC 220

**Speaker:** Yue Cai, Texas A&M University

**Description:**Title: Counting with Borel's triangle

Abstract: Borel’s triangle is an array of integers closely related to the classical Catalan numbers. In this talk we present various combinatorial interpretations of Borel’s triangle in terms of lattice paths, binary trees, and pattern avoiding permutations and matchings.

## Postdoc Lunch Time Talks

**Time:** 12:55PM - 1:15PM

**Location:** BLOC 220

**Speaker:** Souvik Goswami, Texas A&M University

**Description:**Heights: Archimedean and non-Archimedean aspects.

The notion of heights on projective space and smooth projective varieties, are classical and well studied. Beilinson built on it to develop a height pairing on certain class of algebraic cycles. This pairing has two components, the non-Archimedean component, which depends on the integer primes, and the Archimedean component, which depends on the complex primes. I will give a glimpse on both, and discuss a new direction.....probably.

## Student Working Seminar in Groups and Dynamics

**Time:** 1:00PM - 2:00PM

**Location:** BLOC 628

**Speaker:** Mehrzad Monzavi

**Title:** *Shannon's Entropy III*

**Abstract:**I will talk about conditional Shannon entropy, conditional typicality and with time's permission, conditional asymptotic equipartition property.

## Number Theory Seminar

**Time:** 1:45PM - 2:45PM

**Location:** BLOC 220

**Speaker:** Junehyuk Jung, Texas A&M University

**Title:** *Counting immersed totally geodesic surfaces via arithmetic means*

**Abstract:**The prime geodesic theorem allows one to count the number of closed geodesics having length less than X in a given hyperbolic manifold. As a naive generalization of the prime geodesic theorem, we are interested in the the number of immersed totally geodesic surfaces in a given hyperbolic manifold. I am going to talk about this question when the underlying hyperbolic manifold is an arithmetic hyperbolic $3$-manifold corresponding to a Bianchi group SL(2,O_{-d}), where O_{-d} is the ring of integers of Q[sqrt{-d}] for some positive integer d.

**URL:** *Link*

## Numerical Analysis Seminar

**Time:** 3:00PM - 4:00PM

**Location:** BLOC 628

**Speaker:** Peter Jantsch, TAMU

**Title:** *The Lebesgue Constant for Leja Points on Unbounded Domains*

**Abstract:**The standard Leja points are a nested sequence of points defined on a compact subset of the real line, and can be extended to unbounded domains with the introduction of a weight function $w : R \rightarrow [0, 1]$. Due to a simple recursive formulation, such abcissas show promise as a foundation for high-dimensional approximation methods such as sparse grid collocation, deterministic least squares, and compressed sensing. Just as in the unweighted case of interpolation on a compact domain, we use results from potential theory to prove that the Lebesgue constant for the Leja points grows subexponentially with the number of interpolation nodes.

## Groups and Dynamics Seminar

**Time:** 3:00PM - 4:00PM

**Location:** BLOC 220

**Speaker:** Robin Tucker-Drob, Texas A&M

**Title:** *Cocycle Superrigidity of Bernoulli shifts and Compact actions*

**Abstract:**I will discuss two results about cocycle superrigidity; the first, which is joint work with Adrian Ioana, is that Bernoulli shift of any nonamenable, inner amenable group, is cocycle superrigid. The second, which is joint with Damien Gaboriau and Adrian Ioana, is that, under a mild strong ergodicity assumption, any left-right translation action of a product group Γ×Λ on a profinite or connected compact group is virtually cocycle superrigid. The proofs of both results use the framework of deformation/rigidity.

## AMUSE

**Time:** 6:00PM - 7:00PM

**Location:** BLOC 220

**Speaker:** Dr. Prabir Daripa, Texas A&M University, Department of Mathematics

**Title:** *Mathematics of "Stability Theory" and "Chaos Theory"*

**Abstract:**"When the present determines the future but the approximate present does not approximately determine the future", we will call it Chaos and study of this phenomena goes by the name "Chaos Theory" (In Wikipedia, you find this as one of the definitions of "Chaos" within "Chaos Theory"). "When the present determines the future and the approximate present does determine the future but may be a drastically different one", then what do we call the theory of this. For now let us call it: "Stability Theory". As you notice just from these definitions, there is a subtle but drastic difference between these two theories. In one case you treat the future (or outcome) as a random variable where as in the later case, you treat it as a deterministic variable. The goal of this seminar is to demystify and exemplify this difference using simple maps, linear algebra and many events, some extreme ones such hurricane Harvey, around us. The content of the talk will be kept very simple so that it is accessible to even first year undergraduate students.