Quantum contact interactions

Abstract

The existence of several exotic phenomena, such as duality and spectral anholonomy is pointed out in one-dimensional quantum wire with a single defect. The topological structure in the spectral space which is behind these phenomena is identified.Comment: A lecture presented at the 2nd Winter Institute on Foundations of Quantum Theory and Quantum Optics (WINST02), Jan. 2-11, 2002, S.N.Bose Institute, Calcutta, India: 8 pages latex with Indian Acad. Sci. style fil