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New York Journal of Mathematics
Volume 32 (2026), 436-460

  

Arup Chattopadhyay and Saikat Giri

Singular traces and perturbation formulae for tuples of commuting unitaries

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Published: March 19, 2026.
Keywords: Krein trace formula, Neidhardt trace formula, Lorentz ideal, singular trace.
Subject [2010]: 47A55, 47B10, 47A13.

Abstract
We derive a natural generalization of the Krein and Neidhardt trace formulas for tuples of commuting unitaries via a multiplicative path, allowing perturbations to be in a family of Lorentz ideals of bounded linear operators.

Acknowledgements

The authors would like to heartily thank the anonymous referee for a careful reading of the manuscript and several helpful suggestions. They also gratefully acknowledge useful conversations with Chandan Pradhan. A. Chattopadhyay is supported by the Core Research Grant (CRG), File No: CRG/2023/004826, from SERB. S. Giri is grateful to the Ministry of Education, Government of India, for financial support through the Prime Minister's Research Fellowship (PMRF-ID: 1902164) grant.


Author information

Arup Chattopadhyay
Department of Mathematics
Indian Institute of Technology Guwahati
Guwahati, 781039, India

arupchatt@iitg.ac.in

Saikat Giri
Department of Mathematics
Indian Institute of Technology Guwahati
Guwahati, 781039, India

saikat.giri@iitg.ac.in