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Mat. Sb., 2025 Volume 216, Number 6, Pages 94–106 (Mi sm10131)

Topological properties of caustics in five-dimensional spaces

V. D. Sedykh

National University of Oil and Gas "Gubkin University", Moscow, Russia

Abstract: We present a list of universal linear relations between the Euler characteristics of manifolds of multisingularities of a generic Lagrangian map to a five-dimensional space. From these relations it follows, in particular, that the numbers $D_5A_2$, $A_4A_3$ and $A_4A_2^2$ of isolated self-intersection points of the corresponding types on any generic compact four-dimensional caustic are even. The numbers $D_4^+A_3+D_4^-A_3+E_6$ and $D_4^+A_2^2+D_4^-A_2^2+\frac12A_4A_3$ are also even.
Bibliography: 7 titles.

Keywords: Lagrangian map, caustic, $ADE$ singularities, multisingularities, adjacency index, Euler characteristic.

MSC: 53D12, 57R45

Received: 31.05.2024 and 15.12.2024

DOI: 10.4213/sm10131


 English version:
Sbornik: Mathematics, 2025, 216:6, 822–834

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© Steklov Math. Inst. of RAS, 2026