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Atlantic GR Seminar: Nicholas Layden (Dalhousie) and Sharmin Akhter (MUN)

August 26, 2020 @ 1:00 pm - 2:00 pm

Geometric Horizons in the Szekeres Spacetime

Nicholas Layden (Dalhousie University)

A new conjecture for geometric horizons has been introduced which may provide a potential alternative to using apparent horizons and related surfaces for analyzing the dynamics of black hole spacetimes. In particular, using two examples of black hole formation in a collapsing universe in the Szekeres spacetime, the formation, evolution, and detection of geometric horizons are shown. In addition, a function for detecting apparent horizons in the Szekeres spacetime is also considered, and it is shown that the apparent horizon in the Szekeres model, is in fact, a geometric horizon. The Cartan-Karlhede algorithm for determining local equivalences of spacetimes is used to compute an invariant frame in the Newman Penrose frame formalism, and Cartan invariants derived from the spacetime in this frame are shown to detect the geometric horizons under various conditions on the curvature tensors of the spacetime. One model for primordial black hole formation and another for galactic black hole formation are considered with non-zero cosmological constants, generalizing work published previously on these models with zero cosmological constant. Future work utilizing geometric horizons may provide benefits in gravitational wave research involving black hole mergers.

Rigidity of Marginally Outer Trapped Surfaces in RNdS Spacetime

Sharmin Akhter (Memorial University of Newfoundland)

We investigate the rigidity of MOTS in four dimensional Reissner-Nordstrom-de Sitter spacetime. This is connected to the study of the first order derivative of stability operator (and hence the second derivative of outgoing null expansion). Since the stability operator has a zero eigenvalue in our case, we use the Lyapunov-Schmidt reduction to establish rigidity.

The Atlantic General Relativity 2020 online postdoc/student seminar series is in the tradition of the annual AGR meetings, providing a forum not only for students and postdocs to present their research and make professional contacts but also to facilitate connections and collaborations between all Atlantic Canadian relativists. The series is student-organized and includes all areas of classical and quantum gravity. Talks will occur on the last Wednesday of every month, with each session consisting of two 30 minute talks. If you would like to attend, please email the organizers for connection details.


August 26, 2020
1:00 pm - 2:00 pm
Event Category:


Zoom seminar