Andrew DeBenedictis

Phantom stars and topology change

In this work, we consider time-dependent dark-energy star models, with an evolving parameter {omega} crossing the phantom divide {omega}=-1. Once in the phantom regime, the null energy condition is violated, which physically implies that the negative radial pressure exceeds the energy density. Therefore, an enormous negative pressure in the center may, in principle, imply a topology change, consequently opening up a tunnel and converting the dark-energy star into a wormhole. The criteria for this topology change are discussed and, in particular, we consider a Casimir energy approach involving quasilocal energy difference calculations that may reflect or measure the occurrence of a topology change. We denote these exotic geometries consisting of dark-energy stars (in the phantom regime) and phantom wormholes as phantom stars. The final product of this topological change, namely, phantom wormholes, have far-reaching physical and cosmological implications, as in addition to being used for interstellar shortcuts, an absurdly advanced civilization may manipulate these geometries to induce closed timelike curves, consequently violating causality.

Matter conditions for regular black holes in

We study the conditions imposed on matter to produce a regular (non-singular) interior of a class of spherically symmetric black holes in the

f(T)

f(T)

gravity

extension of teleparallel gravity. The class of black holes studied is necessarily singular in general relativity. We derive a tetrad which is compatible with the black hole interior and utilize this tetrad in the gravitational equations of motion to study the black hole interior. It is shown that in the case where the gravitational Lagrangian is expandable in a power series

A note on the symmetry reduction of SU(2) on horizons of various topologies

f(T)=T+underset{nneq 1}{sum} b_{n}T^{n}

The Evolution of Lambda Black Holes in the Mini-Superspace Approximation of Loop Quantum Gravity

that black holes can be non-singular while respecting certain energy conditions in the matter fields. Thus the black hole singularity may be removed and the gravitational equations of motion can remain valid throughout the manifold. This is true as long as

Junction Conditions for F(T) Gravity from a Variational Principle

n

Anisotropic structures and wormholes with loop quantum gravity holonomy corrections

is positive, but is not true in the negative sector of the theory. Hence, gravitational

Loop Quantum Corrected Einstein Yang-Mills Black Holes

f(T)

Energy condition respecting warp drives: The role of spin in Einstein-Cartan theory

Lagrangians which are Taylor expandable in powers of