BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Reciprocal geodesics and dihedral subgroups of lattices in PSL(2\,
  R)  - Viveka Erlandsson (Bristol)
DTSTART:20221123T160000Z
DTEND:20221123T170000Z
UID:TALK192548@talks.cam.ac.uk
CONTACT:Oscar Randal-Williams
DESCRIPTION:I will discuss the growth of the number of infinite dihedral s
 ubgroups of lattices in PSL(2\, R). Such subgroups exist whenever the latt
 ice has 2-torsion and they are related to so-called reciprocal geodesics o
 n the corresponding quotient orbifold.  These are closed geodesics passing
  through an even order orbifold point\, or equivalently\, homotopy classes
  of closed curves having a representative in the fundamental group that’
 s conjugate to its own inverse. We obtain the asymptotic growth of the num
 ber of reciprocal geodesics (or infinite dihedral subgroups) in any orbifo
 ld\, generalizing earlier work of Sarnak and Bourgain-Kontorivich on the g
 rowth of the number of reciprocal geodesics on the modular surface. Time a
 llowing\, I will explain how our methods also show that reciprocal geodesi
 cs are equidistributed in the unit tangent bundle. This is joint work with
  Juan Souto. 
LOCATION:MR13
END:VEVENT
END:VCALENDAR