Aug 3, 2000
R-Modes in Relativistic Stars
Nils Andersson (Univ Southampton, Math)
**
In this talk I describe recent progress into the study of r-modes and rotational
``hybrid'' modes of relativistic
stars. It is shown that - as in Newtonian gravity - the spectrum of
low-frequency rotational
modes is highly sensitive to the stellar equation of state.
If the star
and its perturbations obey the same one-parameter equation of state
(when there is no stratification in the star) there exist no pure r-modes at
all - no modes
whose limit, for a star with zero angular velocity, is an axial-parity
perturbation. Rotating stars of this kind similarly have no pure
g-modes, no modes whose spherical limit is a perturbation with polar
parity and vanishing perturbed pressure and density.
In spherical stars of this kind, the r-modes and g-modes form a
degenerate zero-frequency subspace. Our results show that rotation splits the
degeneracy to zeroth order in the star's angular velocity
and the resulting modes are generically hybrids with both axial and polar parts.
Non-stratified Newtonian stars retain a vestigial set of purely
axial modes (those with l=m); however, for corresponding relativistic
stars we show that these modes must also be replaced by axial-led hybrids.
On the other hand, if the star is stratified (if
the perturbed star obeys an equation of state that differs from that of
the unperturbed star) the r-modes alone span the degenerate zero-frequency
subspace of the spherical star. In Newtonian stars, this degeneracy is
split only by the higher order rotational corrections. However, when
relativistic effects are included the degeneracy is again broken at zeroth
order.
Finally, I discuss results for the first post-Newtonian corrections to the
Newtonian r-modes for both stratified and non-stratified stars.
**

gr-qc/00008019
**
**
Audio for this talk requires sound hardware, and RealPlayer or RealAudio
by RealNetworks.

Begin continuous audio for the whole talk:
high bandwidth or low bandwidth.
(Or, right-click to download the whole audio file.)

To begin viewing slides, click on the first slide below.

Author entry (protected)