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# Events for 09/13/2019 from all calendars

## Mathematical Physics and Harmonic Analysis Seminar

## Student/Postdoc Working Geometry Seminar

## Algebra and Combinatorics Seminar

## Noncommutative Geometry Seminar

**Time:** 1:50PM - 2:50PM

**Location:** BLOC 628

**Speaker:** Selim Sukhtaiev, Rice University

**Title:** *Hadamard-type formulas and resolvent expansions*

**Abstract:** In this talk I will discuss an Hadamard-type variation formula for eigenvalue curves of one-parameter families of self-adjoint operators. The main application will be given to computation of the spectral flow of differential operators in terms of the signature of the Maslov form. This is joint work (in progress) with Y. Latushkin.

**Time:** 2:00PM - 3:00PM

**Location:** BLOC 624

**Speaker:** C.J. Bott, TAMU

**Title:** *The cactus variety of the Veronese after the Buczynski family*

**Abstract:** discussion of https://arxiv.org/pdf/1012.3563.pdf

**Time:** 3:00PM - 3:50PM

**Location:** BLOC 628

**Speaker:** Alexander Ruys de Perez, Texas A&M University

**Title:** *Max Intersection Complete Codes and the Factor Complex*

**Abstract:** A place cell is a neuron corresponding to a subset of Euclidean space known as a place field, that will fire if and only if the individual to which the neuron belongs is within that place field. The firing patterns of a collection of n place fields can be represented by a neural code C on n neurons, which is a subset of 2n . Determining whether C is convex, meaning that there is an arrangement of convex place fields for which C is the code, remains an open problem. A sufficient condition for convexity is being max intersection complete: any intersection of maximal codewords is also a codeword. Currently, the only way to determine this property is to evaluate all such intersections. We present a new method to determine max intersection completeness by introducing a simplicial complex for a code C called the factor complex ∆O(C) of C. We show how to construct ∆O(C) using Stanley-Reisner theory, describe how ∆O(C) encodes information about C, and give an algorithm to check whether C is max intersection complete using the factor complex of a closely related code.

**Time:** 4:00PM - 5:00PM

**Location:** BLOC 220

**Speaker:** Caterina Consani, Johns Hopkins University

**Title:** *[Colloquium] Under and above Spec(Z)*

**Abstract:** The talk will describe some recent geometric constructions related to the algebraic spectrum of the integers and the adele class space of the rationals which are part of a joint work with A. Connes.

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