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Symplectic semi-characteristics

Hao Zhuang

Vol. 343 (2026), No. 2, 485–507
Abstract

We define and study the symplectic semi-characteristic of a closed 4n-dimensional symplectic manifold, based on the even-degree part of the primitive cohomology. Using a vector field with nondegenerate zero points, we prove a counting formula for the symplectic semi-characteristic. As corollaries of the counting formula, we obtain a vanishing property and the fact that the definition of the symplectic semi-characteristic is independent of the choice of symplectic forms.

Keywords
mod 2 index, primitive cohomology, symplectic semi-characteristic
Mathematical Subject Classification
Primary: 58J20
Secondary: 53D05
Milestones
Received: 30 October 2025
Revised: 10 March 2026
Accepted: 21 April 2026
Published: 22 May 2026
Authors
Hao Zhuang
Beijing International Center for Mathematical Research
Peking University
Beijing
China

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