Ellis wormholes in anti-de Sitter space

We construct traversable wormholes with anti-de Sitter asymptotics supported by a phantom field. These wormholes are massless and symmetric with respect to reflection of the radial coordinate $$\eta \rightarrow - \eta $$ η → - η . Their circumferential radius decreases monotonically from radial infinity to their single throat. Analogous to their asymptotically flat counterparts, these anti-de Sitter wormholes possess an unstable radial mode.

The evolutionary pictures for phantom field in loop quantum cosmology

The evolutionary pictures for phantom field in loop quantum cosmology are discussed in this paper. Comparing the dynamical behaviors of the phantom field with one of the canonical scalar fields in loop quantum cosmology scenario, we found that the [Formula: see text] phase trajectories are the same, but the [Formula: see text] phase-spaces are very different, and the phantom field with considering potentials can drive neither super inflation nor slow-roll inflation in loop quantum cosmology (LQC) scenario. While the universe is filled with multiple dark fluids, to ensure that the condition [Formula: see text] does not violate, the energy density of dark matter [Formula: see text] and the equation-of-state of phantom field [Formula: see text] should satisfy the condition [Formula: see text] at the bounce point. If this constraint condition holds, the universe can enter an inflationary stage, and it is possible to unify the description of phantom field, dark matter and inflation. We introduced a toy model which has the same form of the general Chaplygin gas to unify the dark energy, dark matter and slow-roll inflation, and the slow-roll inflation of the toy model has also been discussed.

Phantom-Like Behavior in Modified Teleparallel Gravity

The recent data from Planck2018 shows that the equation of state parameter of effective cosmic fluid today is w0=-1.03±0.03. This indicates that it is possible for the universe to be in a phantom dominated era today. While a phantom field is essentially capable of explaining this observation, it suffers from some serious problems such as instabilities and violation of the null energy condition. So, it would be interesting to realize this effective phantom behavior without adopting a phantom field. In this paper, we study possible realization of an effective phantom behavior in modified teleparallel gravity. We show that modified teleparallel gravity is able essentially to realize an effective phantom-like behavior in the absence of a phantom field. For this purpose, we choose some observationally viable f(T) functions and prove that there are some subspaces of the models parameter space capable of realizing a phantom-like behavior without adopting a phantom field.