Date |
Speaker |
Title |

Apr. 22, 1:30pm | Roman Golovko (Charles University Prague) |
TBA |

Apr. 15, 1:30pm | Juanita Pinzon-Caicedo (University of Notre Dame) |
TBA |

Apr. 8, 1:30pm | Patricia Cahn (Smith College) |
TBA |

Feb. 11, 1:30pm | Josh Howie (UC Davis) |
TBA |

Feb. 4, 1:30pm | Rima Chatterjee (LSU) |
TBA |

Jan. 14, 11am | Rustam Sadykov (KSU) |
Lusternik-Schnirelmann theory of 4-manifolds |

Jan. 7, 11am | Mikhail Tyomkin (Higher School of Economics, Moscow) |
Alexander polynomial of string links and Gassner matrix |

**Abstracts**

#### April 22, 2021: Roman Golovko "TBA"

*Abstract: *

#### April 15, 2021: Juanita Pinzon-Caicedo "TBA"

*Abstract: *

#### April 8, 2021: Patricia Cahn "TBA"

*Abstract: *

#### February 11, 2021: Josh Howie "TBA"

*Abstract: *

#### February 4, 2021: Rima Chatterjee "TBA"

*Abstract: *

#### January 14, 2021: Rustam Sadykov "Lusternik-Schnirelmann theory of 4-manifolds"

*Abstract: The Lusternik-Schnirelmann category of a topological space X is a minimal number of open sets U_i in a cover of X such that each set U_i is contractible in X. I will discuss various versions of the Lusternik-Schnirelmann category of 4-manifolds. In particular, I will discuss the relation of the Lusternik-Schnirlemann theory of 4-manifolds to Gay-Kirby trisections.
This is a joint work with Stanislav Trunov. *

#### January 7, 2021: Mikhail Tyomkin "Alexander polynomial of string links and Gassner matrix"

*Abstract: String link is a certain generalization of a pure braid, where we
allow string to go upwards. One can define
Alexander polynomial of a string link in the same manner as for the
usual honest closed link in a 3-sphere. On the other hand, given
string link L one can consider its closure \hat{L}, which is a closed
link. We will discuss a formula which relates Alexander polynomials of
L and \hat{L}. Namely, these two polynomials differ by a determinant
of a Gassner matrix --- a certain invariant of a string link, which is
interesting by itself. We assume no prerequisites.*