arXiv subjects
Publications and source records attributed to Nicholas Neary.
The r-mode frequencies of the Tolman VII solution for the slowly rotating non-barotropic approximation within the low frequency regime are estimated. The relativistic correction to Newtonian r-mode calculations is shown as function of the tenuity $\frac{R}{M}$ and is shown to be significant only for very compact neutron stars.
The Tolman VII solution is an exact static spherically symmetric perfect fluid solution of Einstein's equations that exhibits a surprisingly good approximation to a neutron star. We show that this solution exhibits trapped null orbits in a causal region even for a tenuity (total radius to mass ratio) $> 3$. In this region the dynamical part of the potential for axial w - modes dominates over the centrifugal part.
An explicit necessary condition for the occurrence of resonance scattering of axial gravitational waves, along with the internal trapping of null geodesics, is proposed for static spherically symmetric perfect fluid solutions to Einstein's equations. Some exact inhomogeneous solutions which exhibit this trapping are given with special attention to boundary conditions and the physical acceptability of the space times. In terms of the tenuity ($α= R/M$ at the boundary) all the examples given lie in the narrow range $2.8 < α< 2.9$. The tenuity can be raised to more interesting values by the addition of an envelope without altering the trapping.
This paper explores properties of the instantaneous ergo surface of a Kerr black hole. The surface area is evaluated in closed form. In terms of the mass ($m$) and angular velocity ($a$), to second order in $a$, the area of the ergo surface is given by $16 πm^2 + 4 πa^2$ (compared to the familiar $16 πm^2 - 4 πa^2$ for the event horizon). Whereas the total curvature of the instantaneous event horizon is $4 π$, on the ergo surface it ranges from $4 π$ (for $a=0$) to 0 (for $a=m$) due to conical singularities on the axis ($θ=0,π$) of deficit angle $2 π(1-\sqrt{1-(a/m)^2})$. A careful application of the Gauss-Bonnet theorem shows that the ergo surface remains topologically spherical. Isometric embeddings of the ergo surface in Euclidean 3-space are defined for $0 \leq a/m \leq 1$ (compared to $0 \leq a/m \leq \sqrt{3}/2$ for the horizon).