Department of

# Mathematics

Seminar Calendar
for events the day of Tuesday, February 2, 2021.

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events for the
events containing

More information on this calendar program is available.
Questions regarding events or the calendar should be directed to Tori Corkery.
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Tuesday, February 2, 2021

11:00 am in Zoom,Tuesday, February 2, 2021

#### Redshift in algebraic K-theory

###### Jeremy Hahn (MIT)

Abstract: I will describe work, joint with Dylan Wilson, about the redshifting properties of algebraic K-theory. I will focus on concrete examples, sketching proofs at the prime 2 that K(ko) has chromatic height 2 and K(tmf) has chromatic height 3.

For Zoom info, please email vesna@illinois.edu

2:00 pm in Zoom,Tuesday, February 2, 2021

#### Acyclic graphs with at least 2L + 1 vertices are L-recognizable

###### Dara Zirlin (UIUC)

Abstract: The $(n-L)$-deck of an $n$-vertex graph is the multiset of subgraphs obtained from it by deleting $L$ vertices. A family of $n$-vertex graphs is $L$-recognizable if every graph having the same $(n-L)$-deck as a graph in the family is also in the family. We prove that the family of $n$-vertex graphs having no cycles is $L$-recognizable when $n\geq 2L+1$ (except when $(n,L)=(5,2)$). It is already known that this fails when $n=2L$ and when $(n,L)=(5,2)$.

This is joint work with Alexandr V. Kostochka, Mina Nahvi, and Douglas B. West.

For Zoom information, please contact Sean at SEnglish (at) illinois (dot) edu.