PreprintCC BY 4.0arXiv
Applications of C*-Entropy to Representation Growth for Discrete Groups
Abstract
The topological $1$-bounded entropy htop(C*(Γ)) of the full group C*-algebra of a finitely generated group Γ is given a representation-theoretic interpretation. The implications of Hilbert-Schmidt stability and matricial stability are investigated within this setting, recovering and strengthening a representation growth result of Hadwin and Shulman. The entropy framework is used to prove upper bounds on representation growth for superrigid groups and property (T) groups. This recovers a result of De La Harpe, Robinson, and Valette on the growth rate of the irreducible unitary representations of a property (T) group within the framework of $1$-bounded entropy. A soft proof that SLn(Z) admits subexponential representation growth is recorded.
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BibTeX
@misc{macmahon2026applications,
title = {{Applications of $C^*$-Entropy to Representation Growth for Discrete Groups}},
author = {Connor MacMahon},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21080},
eprint = {2610.21080},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21080},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Applications of C^*-Entropy to Representation Growth for Discrete Groups
AU - Connor MacMahon
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.21080
UR - https://arxiv.org/abs/2610.21080
AB - The topological $1$-bounded entropy h^top(C^*(Γ)) of the full group C^*-algebra of a finitely generated group Γ is given a representation-theoretic interpretation. The implications of Hilbert-Schmidt stability and matricial stability are investigated within this setting, recovering and strengthening a representation growth result of Hadwin and Shulman. The entropy framework is used to prove upper bounds on representation growth for superrigid groups and property (T) groups. This recovers a result of De La Harpe, Robinson, and Valette on the growth rate of the irreducible unitary representations of a property (T) group within the framework of $1$-bounded entropy. A soft proof that SL_n(Z) admits subexponential representation growth is recorded.
ER -