Weak type estimates for the absolute value mapping

TL;DR

This paper establishes weak type estimates for the absolute value mapping of operators, showing that the difference of absolute values belongs to a specific ideal when the operators differ by a trace class operator.

Contribution

It introduces new weak type estimates for the absolute value mapping in operator theory, extending previous results to a semifinite setting and providing commutator estimates.

Findings

|A| - |B| belongs to L_{1,} when A-B is trace class

Provides eigenvalue decay estimates for |A| - |B|

Extends results to semifinite von Neumann algebras

Abstract

We prove that if A and B are bounded self-adjoint operators such that A-B belongs to the trace class, then |A| -|B| belongs to the principal ideal L_{1,\infty} in the algebra L(H) of all bounded operators on an infinite-dimensional Hilbert space generated by an operator whose sequence of eigenvalues is {1, 1/2, 1/3, 1/4, ...}. Moreover, \mu(j;|A| -|B|)\leq const(1 + j)^{-1}\|A-B\|_1. We also obtain a semifinite version of this result, as well as the corresponding commutator estimates.