MG14 - Talk detail

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Abstract

An interesting cosmological history was proposed by Prigogine {\it et al.} who considered the Universe as a thermodynamically open system. This scenario is characterized by a process of matter creation, which corresponds to an irreversible energy flow from the gravitational field to the pressureless matter fluid. Here, we show that the gravitationally induced particle production may arise from a nonminimal curvature-matter coupling. By considering the equivalent scalar-tensor theory, the cosmological implications of the model are discussed. As all known natural systems tend to a state of thermodynamic equilibrium, and assuming the universe is not different in this respect, we also discuss the conditions to attain the equilibrium state.

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Accepted

Yes

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Time

Talk

Title

Abstract

We consider the possibility of multiply-connected spacetimes, ranging from the Flamm-Einstein-Rosen bridge, geons, and the modern renaissance of traversable wormholes. A fundamental property in wormhole physics is the flaring-out condition of the throat, which through the Einstein field equation entails the violation of the null energy condition. In the context of modified theories of gravity, it has also been shown that the normal matter can be imposed to satisfy the energy conditions, and it is the higher order curvature terms, interpreted as a gravitational fluid, that sustain these non-standard wormhole geometries, fundamentally different from their counterparts in general relativity. In addition to exploring interesting features of these geometries, in particular, the physical properties and characteristics of these 'exotic spacetimes,' we also analyze other non-trivial general relativistic geometries which generate closed timelike curves. All these aspects are analyzed in this talk.​

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Session

Accepted

Yes

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Time

Talk

Title

Abstract

We present a novel framework that can be adapted to a wide class of generic spherically symmetric thin-shell wormholes. By using the cut-and-paste procedure, we analyze the stability of arbitraryspherically symmetric thin-shell wormholes to linearized spherically symmetric perturbations around static solutions. We demonstrate in full generality that the stability of the wormhole is equivalent to choosing suitable properties for the exotic material residing on the wormhole throat. As an application, we also consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. (Based on arXiv:1112.2057 [gr-qc] and arXiv:1407.7758 [gr-qc])

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Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

We develop an extremely general and robust framework that can be adapted to wide classes of generic spherically symmetric thin-shell gravastars. The thin shell (transition layer) will be permitted to move freely in the bulk spacetimes, permitting a fully dynamic analysis. This will then allow us to perform a general stability analysis, where it is explicitly shown that the gravastar stability is related to the properties of the matter residing in the thin-shell transition layer. (Based on: JCAP 1203, 034 (2012) [arXiv:1112.5253 [gr-qc]])

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