Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution

Details Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution

Jun 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt.........6m&link_type=abstract

Thesis (PhD). QUEEN'S UNIVERSITY AT KINGSTON (CANADA), Source DAI-B 63/12, p. 5891, Jun 2003, 138 pages.

Computer Science

Scientific paper

In this thesis, I present results from the numerical study of the collapse of a self-gravitating collisionless stellar system. This investigation is divided into three parts. In the first stage, the system is taken to have a distribution function (DF) which is initially polytropic, with one spatial (r) and two velocity (vr, j 2) phase space directions. Although this system is stable to linear perturbations I introduce a non-linear disturbance by ‘cooling’ the system abruptly relative to virial equilibrium. Time evolution is followed using the coupled Collisionless Boltzmann (CBE) and Poisson's equations (or Vlasov equation [83]). By cooling clouds of various polytropic index n I am able to reproduce an instability observed by Henriksen & Widrow [31] in their investigation of self-similar collapse which may be the driving mechanism toward the complete relaxation of the system. In the second stage, the constraint of spherical symmetry is removed and a treecode is used to follow the evolution of the system. The initial distribution was taken to be a lowered Evans model (Kuijken & Dubinski [47]) which emulates a galactic halo, destabilized as above. Each particle is tagged with the value of the DF at its initial phase- space position. This allows us to observe the evolution of the velocity distribution directly as the system relaxes to a new equilibrium. I have shown in both the spherical and non-spherical collapse simulations evolution to new equilibrium configurations in which the velocity distribution approaches a Gaussian form. The evolution to this state has long been an open question, and in this work I am able to elucidate the process responsible and confirm predictions made from statistical considerations (Lynden-Bell [53]; Nakamura [63]). The third stage consists of a series of simulations of merging haloes. These simulations show a transition to a Gaussian velocity distribution which is increasingly suppressed as the initial separation is increased. Possible reasons for this are discussed.

Affiliated with

Also associated with

No associations

Rating

Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Relaxation of a collisionless system and the transition to a new equilibrium velocity distribution will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1534732