12,437 research outputs found
Spindensities in Pseudo-classical kinetic theory
In this paper the classical limit of relativistic transport theories for spin
1/2 fermions is examined through a comparison with the classical kinetic theory
derived from N=1 supersymmetric classical mechanics. The conclusion is that in
the classical limit spindensities, i.e. the axial-vector contribution to the
relativistic Wigner-function, vanishes and dipole-densities, i.e. the
spin-tensor contributions to the relativistic Wigner function, may survive.Comment: Latex 22 pages, 63628 bytes. No figure
Construction of a Lax Pair for the -Painlev\'e System
We construct a Lax pair for the -Painlev\'e system from first
principles by employing the general theory of semi-classical orthogonal
polynomial systems characterised by divided-difference operators on discrete,
quadratic lattices [arXiv:1204.2328]. Our study treats one special case of such
lattices - the -linear lattice - through a natural generalisation of the big
-Jacobi weight. As a by-product of our construction we derive the coupled
first-order -difference equations for the -Painlev\'e
system, thus verifying our identification. Finally we establish the
correspondences of our result with the Lax pairs given earlier and separately
by Sakai and Yamada, through explicit transformations
Tidal interaction of a rotating 1 Msun star with a binary companion
We calculate the tidal torque on a uniformly rotating 1 Msun star at various
stages of core hydrogen burning by an orbiting companion. We apply the
`traditional approximation' and solve the radial part of the tidal
perturbations by matrix inversion of the set of finite difference equations on
a very fine grid. We have identified resonances with gravity- and
quasi-toroidal modes with up to 1000 radial nodes in the more evolved stellar
models. For low forcing frequencies we find significant tidal response due to
viscous damping of inertial modes in the convective envelope of the solar-type
star. We conclude that effects due to stellar rotation (including resonance
locking) may considerably enhance the speed of tidal evolution in solar-type
stars.Comment: accepted for publ. in A&A, 11 pages, 6 figure
Tidal evolution of eccentric orbits in massive binary systems; a study of resonance locking
We study the tidal evolution of a binary system consisting of a 1.4 Msun
compact object in elliptic orbit about a 10 Msun uniformly rotating main
sequence star for various values of the initial orbital parameters. We apply
our previously published results of 2D non-adiabatic calculations of the
non-radial g- and r-mode oscillations of the uniformly rotating MS star, and
include the effects of resonant excitation of these modes in the tidal
evolution calculations. A high orbital eccentricity enhances the effectiveness
of the tidal interaction because of the large number of harmonic components of
the tidal potential and the reduced orbital separation near periastron. By
including the evolution of the MS star, especially of its rotation rate, many
resonance crossings occur with enhanced tidal interaction. We analyse the
phenomenon of resonance locking whereby a particular tidal harmonic is kept
resonant with a stellar oscillation mode. Resonance locking of prograde g-modes
appears an effective mechanism for orbital circularization of eccentric orbits.
We consider the orbital evolution of the binary pulsar PSR J0045-7319 and
conclude that resonance locking could explain the observed short orbital decay
time of this system if the B-star spins in the direction counter to the orbital
motion.Comment: 21 pages, 11 figures; some at reduced resolution, accepted for
publication in A&
- …