The lectures take place in room 0.03 on the ground floor.

### Saturday (December 10th):

9:00–9:45 | Helmut Friedrich, Gravitational waves and asymptotic flatness |

9:45–10:30 | Roger Penrose, Gravitational waves in Our Aeon, and from the Previous One |

10:30–11:00 | coffee break |

11:00–11:45 | Andrzej Trautman, Gravitational waves: what little I remember of my early work on the subject |

11:45–12:30 | Pawel Nurowski, Towards a theory of gravitational radiation |

12:30–14:00 | lunch |

14:00–14:30 | Piotr Chruściel, Radiating solutions of the vacuum Einstein equations |

14:30–15:00 | Igor Novikov, Wormholes and detection of gravitational waves |

15:00–15:30 | Joerg Frauendiener, Gravitational waves and black holes: a global computational approach |

15:30–16:00 | coffee break |

16:00–16:30 | Petr Horava, Quantum Gravity and Naturalness in the Aristotelian Spacetime |

16:30–17:00 | Iwo Białynicki-Birula, Is there a vacuum state of the gravitational radiation? |

17:00–17:30 | Jerzy Kijowski, The Trautman-Bondi energy: how to measure the amount of radiated energy? |

### Sunday (December 11th):

9:30–10:00 | Uwe Semmelmann, Spinors in Riemannian geometry |

10:00–10:30 | Jacek Tafel, Optical geometries and algebraically special spacetimes |

10:30–11:00 | Paul Tod, A positive Bondi–type mass in asymptotically de Sitter spacetimes |

11:00–11:30 | coffee break |

11:30–12:00 | Piotr Jaranowski, Post-Newtonian modelling of gravitational-wave sources |

12:00–12:30 | Andrzej Królak, First detections of gravitational wave signals |

## List of speakers and abstracts

- Iwo Białynicki-Birula,
*Is there a vacuum state of the gravitational radiation?* - Piotr Chruściel,
*Radiating solutions of the vacuum Einstein equations*

I will describe some global properties of the Robinson-Trautman metrics, as well as some progress concerning existence and properties of asymptotically flat space-times containing gravitational radiation.

- Joerg Frauendiener,
*Gravitational waves and black holes: a global computational approach*

It is well known that gravitational waves interact in a non-linear way. This makes it difficult to describe them rigourously. The cleanest description is based on a certain conformal invariance of the Einstein equations — a fact which was established by R. Penrose and was used by H. Friedrich to prove several important global results for general relativistic space-times. The so called conformal field equations implement this conformal invariance on the level of partial differential equations. They provide various well-posed initial (boundary) value problems for use in different situations. The talk will give a computational perspective on the non-linear interaction of plane gravitational waves and also present preliminary results of a simulation of the behaviour of an initially spherically symmetric black hole under the impact of a gravitational wave burst.

- Helmut Friedrich,
*Gravitational radiation and asymptotic flatness*

The radiation fields associated with localized gravitational wave generation processes are based on idealizations involving asymptotically flat far fields. In the talk will be discussed various questions arising from the ambiguities in the definitions of asymptotic flatness at space-like or null infinity.

- Petr Horava,
*Quantum Gravity and Naturalness in the Aristotelian Spacetime* - Piotr Jaranowski,
*Post-Newtonian modelling of gravitational-wave sources* - Jerzy Kijowski,
*The Trautman-Bondi energy* - Andrzej Królak,
*First detections of gravitational wave signals* - Igor Novikov,
*Wormholes and detection of the gravitational waves* - Paweł Nurowski,
*Towards a theory of gravitational radiation* - Roger Penrose,
*Gravitational waves in Our Aeon, and from the Previous One*

The recent discovery of gravitational waves by the LIGO team demonstrated not only the precision of Einstein’s General Relativity in its prediction of black holes and the emission of gravitational waves when pairs of them engulf one another, but also of the importance of detailed computer calculations describing such events. In the theory of conformal cyclic cosmology, another role can be found for such calculations, where it is argued that encounters between supermassive black holes in the aeon prior to ours produce signals detectable in our cosmic microwave background.

- Uwe Semmelmann,
*Spinors in Riemannian geometry* - Paul Tod,
*A positive Bondi–type mass in asymptotically de Sitter spacetimes*

There are well-motivated definitions of total momentum for asymptotically-flat and asymptotically-anti de Sitter space-times, which also have desirable properties of positivity and rigidity (in the sense that their vanishing implies flatness). Much less has been done for asymptotically-de Sitter space-times, though it is attracting more interest. In this talk I describe a spinor-based approach to the problem of defining mass at infinity in space-times with positive Λ (and therefore with space-like ℐ).

Based on arXiv:1505.06637 with Laszlo Szabados, and arXiv:1505.06123; the problem was discussed in Penrose GRG 43 (2011), 3355–3366 and has been considered by Ashtekar and coworkers in arXiv:1409.3816, 1506.06152, 1510.05593, and others more recently.

- Andrzej Trautman,
*Gravitational waves: what little I remember of my early work on the subject*