BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-9763
DTSTART:20260914T170000Z
DTEND:20260914T180000Z
DTSTAMP:20260823T200719Z
LAST-MODIFIED:20260729T175901Z
LOCATION:2241 Chamberlin Hall
SUMMARY:Painleve property: from dynamical accessibility of phase-space
  holes and gravity cusps in 1D Vlasov-Poisson dynamics to stellarator 
 optimization for quasisymmetry\, Plasma Physics (Physics/ECE/NE 922) S
 eminar\, Wrick Sengupta\, Princeton University
DESCRIPTION:We address the dynamical accessibility of a quasistationar
 y state from the infinitely many formal equilibria of the Vlasov-Poiss
 on system. We give a first-principles asymptotic selection theory for 
 Bernstein-Greene-Kruskal (BGK) holes produced by two-stream relaxation
  and cold gravitational clumps produced by collisionless collapse base
 d on two central ideas. First\, repeated shell crossing leads to parti
 cle bunching and phase-space granulation through caustic formations. N
 onlinear phase mixing erases the angle information but preserves the a
 ction dependence of the distribution function (DF). Following Berry an
 d O'Dell's work on caustic whorls\, and Jarzynski's least-biased infor
 mation-theoretic interpretation\, we show that the resulting coarse-gr
 ained DF is a circus-tent DF\, made self-consistent for Vlasov-Poisson
  dynamics. Second\, the selected potential is constrained by the Painl
 eve property (PP) of Poisson's equation written in Sagdeev form. PP im
 plies that the once-integrated Poisson equation must belong to an alge
 braic class reducible to Riccati or Weierstrass form up to suitable va
 riable transformations\, which must be determined by the underlying ph
 ysical processes. The adiabatic theory describes the regular coherent 
 self-organized state in both BGK and gravity. The excluded regions whe
 re action-angle variables fail: the O-point caustic sheet in gravity a
 nd the X-point separatrix sheet in BGK\, require a phase-space-turbule
 nce analysis\, which we leave for subsequent work. Finally\, we show t
 hat PP is also directly relevant to a very different area of plasma ph
 ysics: the  neoclassical optimization of stellarators. PP enables the 
 construction of a reduced phase space for quasisymmetry where the well
  known quasisymmetric configurations such as the Landreman-Paul are co
 nstrained to live. Analytical predictions are thoroughly benchmarked a
 gainst existing configurations such as those from the QUASR database. 
URL:https://www.physics.wisc.edu/events/?id=9763
END:VEVENT
END:VCALENDAR