Talk detail

Participant	Sengupta, Sandipan
Institution	Indian Institute of Technology Kharagpur - Dept of Physics, IIT Kharagpur Campus - Kharagpur, West Midnapore - West Bengal - India

Session	AT3	Accepted		Order	Time
Talk	Oral abstract	Title	Time Travel Using Degenerate Metrics
Coauthors
Abstract	In classical gravity theory, we present explicit examples of vacuum solutions that admit the possibility of time travel (to the past) through their geodesics. These geometries are built upon metrics whose determinant can continuously go to zero over some extended region of the spacetime. These solutions to the first order field equations satisfy the energy conditions. One may see the existence of these solutions as a motivation to revisit the status of causality in the formulation of classical gravity.
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Session	BH2	Accepted		Order	Time
Talk	Oral abstract	Title	Degenerate Extensions Of Schwarzschild Exterior As Alternatives To Black Hole Geometries
Coauthors
Abstract	We present vacuum spacetime solutions of first order gravity, which are described by the exterior Schwarzschild geometry in one region and by degenerate tetrads in the other. Unlike the Kruskal-Szekeres construction based on invertible metrics, these spacetimes represent extensions of the exterior Schwarzschild geometry based on degenerate tetrads. The invertible and noninvertible phases of the tetrad meet at an intermediate hypersurface across which the components of the metric, affine connection and field-strength are all continuous. Within the degenerate spacetime region, the noninvertibility of the tetrad leads to nonvanishing torsion. In contrast to the Schwarzschild spacetime which is the unique spherically symmetric solution of Einsteinian gravity, all the field-strength components associated with these vacuum geometries remain finite everywhere. These vacuum geometries could be particularly relevant in the context of singularities in general relativity as well as that of the information loss problem.
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