Local-to-Global Extensions for Wildly Ramified Covers of Curves

Algebra and Number Theory Seminar

Meeting Details

For more information about this meeting, contact Kristin Berrigan, Robert Vaughan, Mihran Papikian, Ae Ja Yee, Kirsten Eisentraeger, Jack Huizenga.

Speaker: Renee Bell, UPenn

Abstract: Given a Galois cover of curves $X \to Y$ with Galois group $G$ which is totally ramified at a point $x$ and unramified elsewhere, restriction to the punctured formal neighborhood of $x$ induces a Galois extension of Laurent series rings $k((u))/k((t))$. If we fix a base curve $Y$, we can ask when a Galois extension of Laurent series rings comes from a global cover of $Y$ in this way. Harbater proved that over a separably closed field, every Laurent series extension comes from a global cover for any base curve if $G$ is a $p$-group, and he gave a condition for the uniqueness of such an extension. Using a generalization of Artin--Schreier theory to non-abelian $p$-groups, we fully characterize the curves $Y$ for which this extension property holds and for which it is unique up to isomorphism, but over a more general ground field.

Room Reservation Information

Room Number: 106 McAllister

Date: 04/25/2019

Time: 11:00am - 11:50am