October 25th, 2022

  • Date:


  • Speaker:

    Goulnara Arzhantseva (University of Vienna)

  • Title

    Logarithmic girth expander Cayley graphs



    An expander is an infinite family of finite graphs, with a growing number of vertices, that are low vertex degree yet highly connected. Expanders are ubiquitous in mathematics and computer science. In this talk, we focus on expanders with girth tending to infinity. First, we briefly indicate their importance for recent results in group theory, metric geometry and operator K-theory. Then we discuss our new explicit construction of finite 4-regular graphs as in the title. For each dimension n≥2, our graphs are suitable Cayley graphs of SLn(Fp) as prime p → ∞.  These are the first explicit examples in all dimensions n≥2 (all prior examples were in n=2). Together with Margulis' and Lubotzky-Phillips-Sarnak's classical constructions, these new graphs are the only known explicit logarithmic girth Cayley graph expanders. This is a joint work with Arindam Biswas.



    10:00 - 11:30 RTG Lecture 1 (Ana Chavez Caliz)  | INF 267, BioQuant, EG, SR 043
    11:30 - 12:00 Get-Together with speaker | INF 267, BioQuant, EG, SR 043
    12:00 - 13:00 Common lunch | reserved at BräuStadel
    13:00 - 13:30 Informal meeting of PhD students | INF 205, Mathematikon, SR B
    13:30 - 14:30 RTG Colloquium: Goulnara Arzhantseva | INF 205, Mathematikon, SR B
    14:30 - 15:15 Common coffee/ tea | INF 205, Mathematikon, Foyer UG
    15:15 - 16:45 RTG Lecture 2 (Wilderich Tuschmann) | INF 267, BioQuant, EG, SR 043

  • Place: