BEGIN:VCALENDAR
VERSION:2.0
PRODID:https://murmitoyen.com/events/vanille/udem/
X-WR-TIMEZONE:America/Montreal
BEGIN:VEVENT
UID:69e1226384d61
DTSTAMP:20260416T135443
DTSTART:20130514T113000
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20130514T123000
URL:https://murmitoyen.com/events/vanille/udem/detail/230137
LOCATION:Université de Montréal - Pavillon J.-Armand-Bombardier\, 5155\, 
 chemin de la rampe \, Montréal\, QC\, Canada\, H3T 2B2
SUMMARY:Macroscopic spin tunnelling with two interacting spins
DESCRIPTION:Manu Paranjape\, Département de physique\, Université de Mont
 réal\, Montréal\, QC\, CanadaWe study a simple Hamiltonian of two\, larg
 e\, equal\, coupled spins\, of total spin s\, which are subject to an exte
 rnal easy axis potential and a standard exchange coupling. In the absence 
 of the coupling\, the ground state is four fold degenerate\, corresponding
  to the states where the individual spins are in their highest weight or l
 owest weight states. The two states up-up and down-down remain exact\, deg
 enerate\, eigenstates\, even in the presence of the interaction. They are 
 the ground states for a ferromagnetic coupling. For an anti-ferromagnetic 
 coupling the ground state is non-degenerate and given by the symmetric sup
 erposition (up-down + down-up)\, for integer spins while the combination (
 up-down - down-up) for half odd integer spins. The mixing of the two state
 s\, up-down and down-up first occurs only at 2s order in perturbation theo
 ry. Indeed\, we find the mixing as a consequence of macroscopic spin tunne
 lling via the spin coherent state path integral. The instantons are only d
 efined for complex field configurations\, and their contribution is obtain
 able only by deformation of the contour of path integration into the space
  of complex fields.Site web du groupe du  Prof. ParanjapeCette conférence
  est présentée par le RQMP Versant Nord du Département de physique de 
 l'Université de Montréal et le Département de génie physique de Polyte
 chnique Montréal.
END:VEVENT
BEGIN:VTIMEZONE
TZID:America/Montreal
X-LIC-LOCATION:America/Montreal
END:VTIMEZONE
END:VCALENDAR