MathOverflow 512579, revision 1: The elementary symmetric inequality for a Hermitian Jordan product
We answer the first question in Malkoun's MathOverflow 512579, revision 1: for positive semidefinite Hermitian X,Y, every elementary symmetric function of the eigenvalues of XY+YX is at most its counterpart for X^2+Y^2. The written proof establishes the stronger absolute-value inequality for arbitrary Hermitian X,Y and for H=A*B+B*A, R=A*A+B*B with arbitrary rectangular complex A,B. Cauchy-Binet and Cauchy-Schwarz bound each principal determinant, including singular cases. The pinned Lean declaration proves the original positive-semidefinite assertion; the extensions have written proofs and accompanying exact finite checks.
Authors
- Wenlin Zhang (ORCID: https://orcid.org/0009-0005-2414-7968)
- Haobo Ma
Institutions
- National University of Singapore (SG)
Publication Details
- Journal
- Zenodo (CERN European Organization for Nuclear Research)
- Published
- 2026-11-03
- DOI
- https://doi.org/10.5281/zenodo.23920582
- Primary Topic
- Mathematical Inequalities and Applications
- Type
- preprint