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The Kerr-de Sitter metric, originally proposed by Carter in four dimensions and later extended by Gibbons, Lü, Page and Pope to all dimensions, is likely to play a relevant role among Lambda positive vacuum spacetimes. To better understand what makes it special, we calculate the asymptotic data characterizing the metric near conformal infinity. This requires a review of tools in conformal geometry, such as the Fefferman-Graham expansion, and its relation with the asymptotic initial value problem in arbitrary dimensions. The asymptotic data obtained for Kerr-de Sitter admits a straightforward generalization to a broader class of spacetimes that depends on a set of parameters, which we refer to as Kerr-de Sitter-like class. This class of metrics is obtained explicitly as limits or analytic extensions of Kerr-de Sitter and the space of parameters inherits a natural topological structure from the asymptotic data. Furthermore, we discuss additional characterizations within the Kerr-Schild type metrics and the algebraically special metrics that highlight the geometrical significance of the class.

Speaker: Carlos Peón Nieto (UPM, Madrid)
Friday 24 January 2025, 13:00-14:00
Venue: Potter Room / Zoom link https://cam-ac-uk.zoom.us/j/87235967698.
Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.

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Mon 16 Jun 13:00: Title to be confirmed

Upcoming talks - Fri, 17/01/2025 - 11:21

Title to be confirmed

Abstract not available

Speaker: Hendrik Hildebrandt (Ruhr University Bochum)
Monday 16 June 2025, 13:00-14:00
Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
Series: Cosmology Lunch; organiser: Louis Legrand.

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Mon 12 May 13:00: Title to be confirmed

Upcoming talks - Fri, 17/01/2025 - 11:20

Title to be confirmed

Abstract not available

Speaker: Arnaud de Mattia (IRFU, CEA, Université Paris-Saclay)
Monday 12 May 2025, 13:00-14:00
Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
Series: Cosmology Lunch; organiser: Louis Legrand.

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Mon 19 May 13:00: Title to be confirmed

Upcoming talks - Fri, 17/01/2025 - 11:19

Title to be confirmed

Abstract not available

Speaker: Adrien La Posta (University of Oxford)
Monday 19 May 2025, 13:00-14:00
Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
Series: Cosmology Lunch; organiser: Louis Legrand.

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Tue 11 Feb 13:00: Effects of dynamical interactions on stars and planets in their birth environment

None - Fri, 17/01/2025 - 10:52

Effects of dynamical interactions on stars and planets in their birth environment

Most stars form in grouped or clustered environments with other stars. These star-forming regions can survive for millions of years but can change dramatically over just a short period of time – either collapsing under their own gravity or expanding. So, what we see today might not be what they looked like initially during their formation. While a cluster is contracting or expanding, stars can pass very close to each other. This can lead to them being flung out of their birth region to become runaway stars. Planets that might already exist in an exoplanet system may have their orbits altered compared to their formation, be ejected from their system, be stolen by passing stars, or collide with each other. In this seminar, I will discuss how N-body simulations and observations can be used to investigate these interactions. I will talk about how runaway stars can tell us something about the initial conditions of these regions. How observations from telescopes like Gaia, can be used to search for these ejected stars in the night sky. I will then move on to the planetary systems and how they are affected and possibly altered by interactions in their birth environment. In particular, I will discuss, if the Kepler dichotomy (the apparent excess of single-transit systems compared to multi-transit systems) can be explained by birth environment interactions and if there is a difference in the effects of internal and external perturbations on planet systems.

Speaker: Christina Schoettler (Keele University)
Tuesday 11 February 2025, 13:00-14:00
Venue: HOYLE LECTURE THEATRE + ONLINE - Details to be sent by email.
Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Tue 11 Feb 13:00: Effects of dynamical interactions on stars and planets in their birth environment

Upcoming talks - Fri, 17/01/2025 - 10:52

Effects of dynamical interactions on stars and planets in their birth environment

Most stars form in grouped or clustered environments with other stars. These star-forming regions can survive for millions of years but can change dramatically over just a short period of time – either collapsing under their own gravity or expanding. So, what we see today might not be what they looked like initially during their formation. While a cluster is contracting or expanding, stars can pass very close to each other. This can lead to them being flung out of their birth region to become runaway stars. Planets that might already exist in an exoplanet system may have their orbits altered compared to their formation, be ejected from their system, be stolen by passing stars, or collide with each other. In this seminar, I will discuss how N-body simulations and observations can be used to investigate these interactions. I will talk about how runaway stars can tell us something about the initial conditions of these regions. How observations from telescopes like Gaia, can be used to search for these ejected stars in the night sky. I will then move on to the planetary systems and how they are affected and possibly altered by interactions in their birth environment. In particular, I will discuss, if the Kepler dichotomy (the apparent excess of single-transit systems compared to multi-transit systems) can be explained by birth environment interactions and if there is a difference in the effects of internal and external perturbations on planet systems.

Speaker: Christina Schoettler (Keele University)
Tuesday 11 February 2025, 13:00-14:00
Venue: HOYLE LECTURE THEATRE + ONLINE - Details to be sent by email.
Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Thu 13 Feb 16:00: New frontiers in transient astrophysics: gravitational-wave multi-messenger sources and r-process nucleosynthesis

Upcoming talks - Thu, 16/01/2025 - 13:28

New frontiers in transient astrophysics: gravitational-wave multi-messenger sources and r-process nucleosynthesis

The detection of GW170817 enabled us to track down and watch the cataclysmic event in multiple wavelengths of light, allowing us to scrutinize the source of these cosmic ripples for the first time. This discovery provided the first solid evidence that neutron-star smashups are the source of much of the Universe’s gold, platinum and other heavy elements in the Universe. With a single event, we were able to answer fundamental questions in general relativity, cosmology, nuclear physics, and astrophysics. However, other parts of the story told by these events are still shrouded in mystery. For astronomers and physicists across disciplines, this is an extremely exciting time to be alive.