SPEAKER: Franscisco Lobo (CAAUL, Lisbon)
ABSTRACT: 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. We also briefly present a mechanism for the ER=EPR schematic relationship recently proposed by Maldacena and Susskind, using geons in the context of quadratic Palatini gravity. All these aspects are analyzed in this talk.