TY - JOUR
T1 - Bounding the Frobenius norm of a q-deformed commutator
AU - Chruściński, Dariusz
AU - Kimura, Gen
AU - Ohno, Hiromichi
AU - Singal, Tanmay
N1 - Funding Information:
D.C. was supported by the Polish National Science Centre Project No. 2018/30/A/ST2/00837 . G. K. was supported in part by JSPS KAKENHI Grants No. 17K18107 .
Publisher Copyright:
© 2022 The Authors
PY - 2022/8/1
Y1 - 2022/8/1
N2 - For two n×n complex matrices A and B, we define the q-deformed commutator as [A,B]q:=AB−qBA for a real parameter q. In this paper, we investigate a generalization of the Böttcher-Wenzel inequality which gives the sharp upper bound of the (Frobenius) norm of the commutator. In our generalisation, we investigate sharp upper bounds on the q-deformed commutator. This generalization can be studied in two different scenarios: firstly bounds for general matrices, and secondly for traceless matrices. For both scenarios, partial answers and conjectures are given for positive and negative q. In particular, denoting the Frobenius norm by ||.||F, when A or B is normal, we prove the following inequality to be true and sharp: ||[A,B]q||F2≤(1+q2)||A||F2||B||F2 for positive q. Also, we conjecture that the same bound is true for positive q when A or B is traceless. For negative q, we conjecture other sharp upper bounds to be true for the generic scenarios and the scenario when A or B is traceless. All conjectures are supported with numerics and proved for n=2.
AB - For two n×n complex matrices A and B, we define the q-deformed commutator as [A,B]q:=AB−qBA for a real parameter q. In this paper, we investigate a generalization of the Böttcher-Wenzel inequality which gives the sharp upper bound of the (Frobenius) norm of the commutator. In our generalisation, we investigate sharp upper bounds on the q-deformed commutator. This generalization can be studied in two different scenarios: firstly bounds for general matrices, and secondly for traceless matrices. For both scenarios, partial answers and conjectures are given for positive and negative q. In particular, denoting the Frobenius norm by ||.||F, when A or B is normal, we prove the following inequality to be true and sharp: ||[A,B]q||F2≤(1+q2)||A||F2||B||F2 for positive q. Also, we conjecture that the same bound is true for positive q when A or B is traceless. For negative q, we conjecture other sharp upper bounds to be true for the generic scenarios and the scenario when A or B is traceless. All conjectures are supported with numerics and proved for n=2.
KW - Böttcher-Wenzel inequality
KW - Deformed commutator
KW - Frobenius norm
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U2 - 10.1016/j.laa.2022.03.021
DO - 10.1016/j.laa.2022.03.021
M3 - Article
AN - SCOPUS:85127506767
SN - 0024-3795
VL - 646
SP - 95
EP - 106
JO - Linear Algebra and Its Applications
JF - Linear Algebra and Its Applications
ER -