## Seminars

### Summer term 2019

### Black-hole evolution from stellar collapse

Abstract: We present a local approach towards black-hole evaporation, which relies on the absence of quantum phase transition across the stellar surface. We show that this approach augmented with Bekensteinâ€™s black-hole entropy gives the Hawking effect if the null energy condition is violated in the initial quantum-field vacuum. If otherwise, an astrophysical black hole may then be expanding, that corresponds to the anti-Hawking effect, i.e. a positive-energy radiation flows into the black hole, taking its origin far away from the event horizon. This quantum process is reverse to the Hawking effect, as the latter is described by a negative-energy influx nearby the horizon, which goes over to a positive-energy outflux in the far-horizon region. We also provide examples of quantum vacua well-known in the literature, which give rise to both quantum effects from stellar collapse.

### Canonical quantization of minisuperspace models with variational symmetries

Abstract: In this talk I will describe how the symmetries of the minisuperspace action are used to integrate the system at the classical and quantum level. For the latter case, we use the canonical quantisation and impose the symmetries as operators on the wave function together with the constraints. This leads to a selection rule which prevents their simultaneous imposition on the wave function and consequently to the choice of subalgebras. Some of them lead to the classical solution but there are cases where we obtain quantum corrections. These, in the Bohmian interpretation we used, are indicated when the quantum potential in the quantum Hamiltonâ€“Jacobi equation does not vanish. I will discuss some examples of physical interest.

Date | Time | Speaker | Topic | Room |
---|---|---|---|---|

April 2, 2019 | 12:00 |
Viacheslav Emelyanov (KIT, Karlsruhe) |
Black-hole evolution from stellar collapse | Konferenzraum 1 (Neubau) |

April 9 | 12:00 |
Adamantia Zampeli (Charles University, Prague) |
Canonical quantization of minisuperspace models with variational symmetries | Konferenzraum 1 (Neubau) |

April 23 | 12:00 |
Yi-Fan Wang (Uni Cologne) |
Dynamically assisted Schwinger effect | Konferenzraum 1 (Neubau) |

April 30 | 12:00 |
Tatevik Vardanyan (Uni Bonn) |
TBA | Konferenzraum 1 (Neubau) |

May 21 | 12:00 |
Victor Berezin (Moscow) |
TBA | Konferenzraum 1 (Neubau) |

June 4 | 12:00 |
Branislav Nikolic (Uni Cologne; disputation) |
TBA | Konferenzraum 1 (Neubau) |

## Past seminars

Winter term 2018/19

Summer term 2018

Winter term 2017/18

Summer term 2017

Winter term 2016/17

Summer term 2016

Winter term 2015/16

Summer term 2015

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