“…In [BK,M2,MO], it was showed that the Gauss sum which is a number theoretic object plays the central roles in an interference phenomenon, the fractional Talbot phenomenon [WW]. As I investigated the algebraic structures behind the connection between wave physics and number theory, there are SL(2, R) and SL(2, Z) ⊂ SL(2, R) [M2].…”