CAAUL Seminar - Geon, spacetime tunnels and time travel - 4 novembro 2013

Geon, spacetime tunnels and time travel 

Francisco Lobo

CAAUL

Abstract / Resumo

We consider the possibility of multiply-connected spacetimes, ranging from the Einstein-Rosen bridge, geons, and the modern renaissance of space-time tunnels/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. A closed timelike curve (CTC) allows time travel, in the sense that an observer that travels on a trajectory in spacetime along this curve, may return to an event before his departure. This fact apparently violates causality, therefore time travel and its associated paradoxes have to be treated with great caution. The paradoxes fall into two broad groups, namely the consistency paradoxes and the causal loops. All these aspects are analyzed in this talk.

4 de novembro de 2013 | 11:00

Local

Faculdade de Ciências da Universidade de Lisboa

Edifício C8 | Sala 1.67