An involution of reals, discontinuous on rationals, and whose derivative vanishes a.e.

ULUDAĞ A. M. , Ayral H.

TURKISH JOURNAL OF MATHEMATICS, cilt.43, ss.1770-1775, 2019 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 43 Konu: 3
  • Basım Tarihi: 2019
  • Doi Numarası: 10.3906/mat-1903-34
  • Dergi Adı: TURKISH JOURNAL OF MATHEMATICS
  • Sayfa Sayıları: ss.1770-1775

Özet

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.