Schiffer's Conjecture, Interior Transmission Eigenvalues and   Invisibility Cloaking: Singular Problem vs. Nonsingular Problem
  In this note, we present some interesting observations on the Schiffer's conjecture, interior transmission eigenvalue problem and their connections to singular and nonsingular invisibility cloaking problems of acoustic waves. 
Hongyu Liu
math.AP math-ph math.DG math.MP