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JOURNALS // Doklady Rossijskoj Akademii Nauk. Mathematika, Informatika, Processy Upravlenia // Archive

Dokl. RAN. Math. Inf. Proc. Upr., 2022 Volume 507, Pages 57–60 (Mi danma319)

MATHEMATICS

Bruhat numbers of a strong Morse function

P. E. Pushkar'ab, M. Tyomkinac

a National Research University Higher School of Economics, Moscow, Russia
b Independent University of Moscow, Moscow, Russia
c Dartmouth College, Hanover, USA

Abstract: Let $f$ be a Morse function on a manifold M such that all its critical values are pairwise distinct. Given such a function (together with a certain choice of orientations) and a field $\mathbb F$, we construct a set of nonzero elements of the field, which are called Bruhat numbers. Under certain acyclicity conditions on $M$, the alternating product of all the Bruhat numbers does not depend on $f$ (up to sign); thus, it is an invariant of the manifold. For any typical one-parameter family of functions on $M$, we provide a relation that links the Bruhat numbers of the boundary functions of the family with the number of bifurcations happening along a path in the family. This relation generalizes the result from [1].

Keywords: Morse theory, Cerf theory, topology of manifolds.

UDC: 515.16

Presented: V. A. Vassiliev
Received: 15.05.2020
Revised: 27.10.2020
Accepted: 27.10.2020

DOI: 10.31857/S2686954322700047


 English version:
Doklady Mathematics, 2022, 106:3, 454–457

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© Steklov Math. Inst. of RAS, 2024