Differences

This shows you the differences between two versions of the page.

--- seminars:template [2026/08/06 20:01] – jlasseter
+++ seminars:template [2026/08/07 13:24] (current) – jlasseter
@@ Line 8: / Line 8: @@
 -----
-=====<CURRENT SEMESTER>=====
+==== Fall 2025 ====
-  * **<DATE>** \\ Speaker: ** <SPEAKER> ** \\ Title: **TBA** <WRAP box>// Abstract: lorem ipsum ...//
-TBA\\ </WRAP>
+**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//** \\
+<WRAP box 90%>
+**//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.\\
+</WRAP>
 -----