Illinois Journal of Mathematics

Unitary approximation of positive operators

Abstract

Of concern are some operators inequalities arising in quantum chemistry. Let $A$ be a positive operator on a Hilbert space $\mathcal{H}$. We consider the minimization of $||U-A||_{p}$ as $U$ ranges over the unitary operators in $\mathcal{H}$ and prove that in most cases the minimum is attained when $U$ is the identity operator. The norms considered are the Schatten $p$-norms. The methods used are of independent interest; application is made of noncommutative differential calculus.

Article information

Source
Illinois J. Math., Volume 24, Issue 1 (1980), 61-72.

Dates
First available in Project Euclid: 20 October 2009

https://projecteuclid.org/euclid.ijm/1256047797

Digital Object Identifier
doi:10.1215/ijm/1256047797

Mathematical Reviews number (MathSciNet)
MR550652

Zentralblatt MATH identifier
0404.47014

Citation

Aiken, John G.; Erdos, John A.; Goldstein, Jerome A. Unitary approximation of positive operators. Illinois J. Math. 24 (1980), no. 1, 61--72. doi:10.1215/ijm/1256047797. https://projecteuclid.org/euclid.ijm/1256047797