PreprintCC BY-NC-ND 4.0arXiv
Quadratic polynomials preserving free infinite divisibility
Abstract
We characterize non-commutative polynomials of degree 2 which preserve free infinite divisibility as self-adjoint Lie polynomials of degree 2. This extends previous results which characterized homogeneous quadratic forms only. The proof is based on an involution of colored noncrossing partitions cancelling many terms; positive definiteness of the remaining terms is established by an explicit operator model on Fock space. Examples show that higher order Lie polynomials do not preserve free infinite divisibility.
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BibTeX
@misc{ejsmont2026quadratic,
title = {{Quadratic polynomials preserving free infinite divisibility}},
author = {Wiktor Ejsmont and Franz Lehner and Mihai Popa and Kamil Szpojankowski},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.15320},
eprint = {2610.15320},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.15320},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Quadratic polynomials preserving free infinite divisibility
AU - Wiktor Ejsmont
AU - Franz Lehner
AU - Mihai Popa
AU - Kamil Szpojankowski
PY - 2026
DA - 2026/10/11
PB - arXiv
DO - 10.48550/arxiv.2610.15320
UR - https://arxiv.org/abs/2610.15320
AB - We characterize non-commutative polynomials of degree 2 which preserve free infinite divisibility as self-adjoint Lie polynomials of degree 2. This extends previous results which characterized homogeneous quadratic forms only. The proof is based on an involution of colored noncrossing partitions cancelling many terms; positive definiteness of the remaining terms is established by an explicit operator model on Fock space. Examples show that higher order Lie polynomials do not preserve free infinite divisibility.
ER -