TURKISH JOURNAL OF MATHEMATICS, cilt.43, sa.3, ss.1770-1775, 2019 (SCI İndekslerine Giren Dergi)
Makale / Tam Makale
TURKISH JOURNAL OF MATHEMATICS
We study the involution of the real line, induced by Dyer's outer automorphism of PGL(2,Z). It is continuous at irrationals with jump discontinuities at rationals. We prove that its derivative exists almost everywhere and vanishes almost everywhere.