On the Index of Fredholm Pairs of Idempotents

作     者：Yue Qing WANG Hong Ke DU Yan Ni DOU 

作者机构：Department of Mathematics and Physics Chongqing University of Science and Technology Chongqing 400042 P. R. China College of Mathematics and Information Science Shaanxi Normal University Xi'an 710062 P. R. China 

出 版 物：《Acta Mathematica Sinica,English Series》 (数学学报（英文版）)

年 卷 期：2009年第25卷第4期

页      面：679-686页

核心收录：

学科分类：07[理学] 070104[理学-应用数学] 0701[理学-数学] 

基　　金：Supported by the National Natural Science Foundation of China (10871224) 

主　　题：Fredholm orthogonal projection positive operator 

摘      要：Using the technique of block-operators, in this note, we prove that if P and Q are idempotents and （P - Q）^2n＋1 is in the trace class, then （P - Q）^2m＋1 is also in the trace class and tr（P - Q）^2m＋1 = dim（k（P） ∩ k（Q）^⊥） -dim（k（P）^⊥ N k（Q））, for all m ≥ n. Moreover, we prove that dim（k（P）∩ k（Q）^⊥） = dim（k（P）^⊥ ∩k（Q）） if and only if there exists a unitary U such that UP = QU and PU = UQ, where k（T） denotes the range of T. Keywords Fredholm, orthogonal projection, positive operator