Colloquium [Department of Mathematics and Statistics, Binghamton University]

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====== Colloquium ======

Unless stated otherwise, colloquia are scheduled for Thursdays 4:00-5:00pm in WH-100E with refreshments served from 3:45-4:00 pm in WH-102.

Organizers: [[people:dobbins:start]], [[people:kargin:start|Vladislav Kargin]], [[people:malkiewich:start]], 
 [[people:adrian:start]], and [[people:ewyman:start]]


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==== Fall 2025 ====

**Thursday Nov 6 4:00-5:00pm, WH-100E**\\  //Speaker//: ** [[ https://blogs.baruch.cuny.edu/aobus/ | Andrew Obus]] ** (CUNY) \\ //Topic//: **//The lifting problem for covers of curves, particularly its group-theoretical aspects//** \\ 

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**//Abstract//**:
Whenever a mathematical object is given in
characteristic p, one can ask whether it is the reduction, in some
sense, of an analogous structure in characteristic zero.  If so, the
structure in characteristic zero is called a "lift" of the structure
in characteristic p.  The most famous example is Hensel's Lemma about
lifting solutions of polynomials in Z/p to solutions in the p-adic
integers Z_p.

The “lifting problem” we consider is more geometric: given a smooth curve X in
characteristic p with an action of a finite group G, is there a curve
in characteristic zero with G-action that reduces to X?  Unsurprisingly, the answer is related to the group theory of G (for instance, if p does not divide |G| or if G is cyclic, then the curve with the G-action always lifts, but if G has an abelian, non-cyclic, non-p-subgroup that fixes a point on X, then the curve does not lift with the action).  After giving an introduction to the lifting problem and some examples, we will discuss well-established ways that the problem interacts with group theory, as well as more recent advances relating the problem to representation theory.\\
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==== Spring 2026 ====

**March 13th** \\ **[[hiltonmemorial:lecture2026|PETER HILTON MEMORIAL LECTURE]]** \\    **SPECIAL TIME AND LOCATION: March 13, 3:30pm, Alumni Lounge at Old O'Connor Hall** \\ Speaker: **Martin Bridson** (University of Oxford) \\ Title: **//Chasing finite shadows of infinite groups through geometry//** <WRAP box>// Abstract: // There are many situations in geometry or elsewhere in mathematics where it is natural or convenient to explore infinite groups of symmetries via their actions on finite objects. But how hard is it find these finite manifestations and  to what extent does the collection of all such actions determine the infinite group? 


In this colloquium, I will sketch some of the rich history of  such problems and then describe some of the great advances in recent years. I'll describe pairs of distinct groups that have the same finite images and I'll sketch the proof of some "profinite rigidity results", i.e. theorems showing that in certain circumstances one can identify an infinite group if one knows its set of finite images. \\
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**Thursday May 7, 2026 2:45-3:45pm, WH-100E**\\  //Speaker//: ** [[ https://sites.math.washington.edu/~novik/ | Isabella Novik]] ** (University of Washington) \\ //Topic//: **//Lower bounds on face numbers//** \\ 

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**//Abstract//**:
In this talk, I will discuss several approaches to studying the face numbers of simplicial complexes, with a particular focus on obtaining lower bounds. These approaches include classical rigidity theory, Stanley-Reisner rings, and higher‑dimensional stress spaces. I will also describe a number of both classical and recent results on face numbers that have been obtained using these tools.

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Archive:

/*  * [[http://www.math.binghamton.edu/dept/colloquia/old.html|1996-2013]] */
/*  * [[http://www.math.binghamton.edu/dept/colloquia/index.html|2013-2014]] */
/*  * [[seminars:colloquium:2014_2015|2014-2015]]*/
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