Sum of Squares Decompositions for Structured Biquadratic Forms

Fuente: arXiv
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Main Authors: Xu, Yi, Cui, Chunfeng, Qi, Liqun
Format: Preprint
Published: 2025
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author Xu, Yi
Cui, Chunfeng
Qi, Liqun
author_facet Xu, Yi
Cui, Chunfeng
Qi, Liqun
contents This paper studies sum-of-squares (SOS) representations for structured biquadratic forms. We prove that diagonally dominated symmetric biquadratic tensors are always SOS. For the special case of symmetric biquadratic forms, we establish necessary and sufficient conditions for positive semi-definiteness of monic symmetric biquadratic forms, characterize the geometry of the corresponding PSD cone as a convex polyhedron, and prove that every such PSD form is SOS for any dimensions $m$ and $n$. We also formulate conjectures regarding SOS representations for symmetric M-biquadratic tensors and symmetric $\mathrm{B}_{0}$-biquadratic tensors, discussing their likelihood and potential proof strategies. Our results advance the understanding of when positive semi-definiteness implies sum-of-squares decompositions for structured biquadratic forms.
format Preprint
id arxiv_https___arxiv_org_abs_2512_02734
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Sum of Squares Decompositions for Structured Biquadratic Forms
Xu, Yi
Cui, Chunfeng
Qi, Liqun
Optimization and Control
This paper studies sum-of-squares (SOS) representations for structured biquadratic forms. We prove that diagonally dominated symmetric biquadratic tensors are always SOS. For the special case of symmetric biquadratic forms, we establish necessary and sufficient conditions for positive semi-definiteness of monic symmetric biquadratic forms, characterize the geometry of the corresponding PSD cone as a convex polyhedron, and prove that every such PSD form is SOS for any dimensions $m$ and $n$. We also formulate conjectures regarding SOS representations for symmetric M-biquadratic tensors and symmetric $\mathrm{B}_{0}$-biquadratic tensors, discussing their likelihood and potential proof strategies. Our results advance the understanding of when positive semi-definiteness implies sum-of-squares decompositions for structured biquadratic forms.
title Sum of Squares Decompositions for Structured Biquadratic Forms
topic Optimization and Control
url https://arxiv.org/abs/2512.02734