Next External Talks

Prebiotic chemistry these days on Earth operates on two different metaphorical “worlds”. On one, leading with the elegant work of the Sutherland, Simons, and Leverhulme teams, the focus is on surface photochemistry of molecules arising from hazy reduced atmospheres, in particular, those where nitrogen is at the oxidation level of ammonia. It has not (yet) produced a single molecule of RNA , the (proposed) informational molecule that (purportedly) initiated Darwinian evolution.

In this talk, a visitor from the other world will show how oligomeric RNA with 3’,5’-linkages 150 ± 50 nucleotides long forms as the natural outcome of “privileged” chemistry beneath redox neutral atmospheres that are transiently reduced by Vesta-to-Ceres sized impactors. On Earth, this most likely happened 4.30 ± 0.05 billion years ago.

This RNA is long enough, and stereoregular enough, to have provided catalysts to support an “RNA World”. This World invented protein translation 4.20 ±0.11 billion years ago (based on arguable molecular clocks), and was sufficiently widespread to have left isotope enriched carbon entrapped in zircons dated at 4.10 billion years ago.

The production of pentoses (like ribose, ~100 kg/km2 per year ) cannot NOT happen on such worlds, if covered by basalts that deliver borate and condensed polyphosphates. Borate and condensed polyphosphate likewise privilege post-impact steps that yield ribonucleosides, ribonucleotides, and RNA .

Speaker: Steven Benner (FfAME Distinguished Fellow)
Tuesday 06 May 2025, 11:00-12:00
Venue: East Seminar Room, Ray Dolby Centre.
Series: LCLU Coffee Meetings; organiser: Paul B. Rimmer.

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Tue 17 Jun 11:15: Love Bites: The Deadly Romance of Spider Pulsars

Thu, 01/05/2025 - 10:25

Love Bites: The Deadly Romance of Spider Pulsars

Pulsars in binary systems are fantastic physics laboratories, primarily because their orbital dynamics allow us to probe binary evolution, test gravity theories, measure neutron star masses, etc. Among them are the “black widows” and “redbacks”, which are nicknamed after the deadly arachnids because the millisecond pulsar they contain gradually destroys their low mass companion. The strongly irradiated dayside displayed by the low-mass companions in these systems is reminiscent of what is observed in exoplanets called “hot jupiters”. In the last decade, the number of known spiders has grown exponentially to the point of becoming the most prevalent type of fast rotating binary pulsars. In this talk, I will present some of the recent efforts undertaken with the MeerKAT telescope to uncover these pulsars and review some of the key advances they have provided for our understanding of binary evolution, stellar physics under extreme irradiation, and measurement of neutron star masses.

Speaker: Prof. Rene Breton (University of Manchester)
Tuesday 17 June 2025, 11:15-12:00
Venue: Martin Ryle Seminar Room, Kavli Institute.
Series: Hills Coffee Talks; organiser: Charles Walker.

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Fri 20 Jun 13:00: Well-posed initial value formulation of general effective field theories of gravity

Wed, 30/04/2025 - 16:38

Well-posed initial value formulation of general effective field theories of gravity

In this talk, I will show that all higher-derivative effective field theories (EFTs) of vacuum gravity admit a well-posed initial value formulation when augmented by suitable regularising terms. These regularising terms can be obtained by field redefinitions and do not affect the dynamics in the regime of validity of EFT . I will explain how our result applies to the quadratic, cubic, and quartic truncations of the EFT of gravity and to various truncations of a simple EFT of a scalar field. Finally, I will also discuss some numerical results on the non-linear dynamics of this simple scalar field theory.

Speaker: Aron Kovacs, Queen Mary University of London
Friday 20 June 2025, 13:00-14:00
Venue: Potter room/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.

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Tue 06 May 13:00: Updates on fundamental science from the secondary CMB

Tue, 29/04/2025 - 15:19

Updates on fundamental science from the secondary CMB

A major frontier in cosmic microwave background (CMB) science is the study of secondary anisotropies—temperature and polarization anisotropies induced by the gravitational, electromagnetic, or beyond-standard-model (BSM) interactions of CMB photons with large-scale structure (LSS) over cosmic history. Leveraging their distinct statistical properties and cross-correlations with LSS enables us to isolate these secondary anisotropies from the primary CMB and extract new astrophysical and cosmological information. In this talk, I discuss how secondary anisotropies from electromagnetic interactions (Sunyaev-Zel’dovich effects) and hypothetical BSM particles (dark screening) can serve as probes of fundamental physics. I present a general formalism for capturing the information content of secondary anisotropies. I then give a summary of existing measurements of the kinetic Sunyaev-Zel’dovich (kSZ), polarized Sunyaev-Zel’dovich (pSZ), and dark screening effects. Next I provide an update on how these measurements constrain large-scale homogeneity, primordial non-Gaussianity, isocurvature, and BSM particles (axions and dark photons). Looking ahead to the high-resolution, low-noise, large-volume frontier, I discuss how upcoming observations from the Simons Observatory, combined with LSS surveys like DESI and LSST , will significantly improve these results and allow for novel tests of fundamental physics.

Speaker: Matthew Johnson (Perimeter Institute and York University)
Tuesday 06 May 2025, 13:00-14:00
Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
Series: Cosmology Lunch; organiser: Thomas Colas.

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Fri 30 May 13:00: Gravitational Wave Signatures of Dark Matter in Neutron Star Mergers

Tue, 29/04/2025 - 12:38

Gravitational Wave Signatures of Dark Matter in Neutron Star Mergers

Binary neutron star mergers provide insights into strong-field gravity and the properties of ultra-dense nuclear matter. These events offer the potential to search for signatures of physics beyond the standard model, including dark matter. We present the first numerical-relativity simulations of binary neutron star mergers admixed with dark matter, based on constraint-solved initial data. Modeling dark matter as a non-interacting fermionic gas, we investigate the impact of varying dark matter fractions and particle masses on the merger dynamics, ejecta mass, post-merger remnant properties, and the emitted gravitational waves. Our simulations suggest that the dark matter morphology – a dense core or a diluted halo – may alter the merger outcome. Scenarios with a dark matter core tend to exhibit a higher probability of prompt collapse, while those with a dark matter halo develop a common envelope, embedding the whole binary. Furthermore, gravitational wave signals from mergers with dark matter halo configurations exhibit significant deviations from standard models when the tidal deformability is calculated in a two-fluid framework neglecting the dilute and extended nature of the halo. This highlights the need for refined models in calculating the tidal deformability when considering mergers with extended dark matter structures. These initial results provide a basis for further exploration of dark matter’s role in binary neutron star mergers and their associated gravitational wave emission and can serve as a benchmark for future observations from advanced detectors and multi-messenger astrophysics.

Speaker: Violetta Sagun, University of Southampton
Friday 30 May 2025, 13:00-14:00
Venue: MR9/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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Fri 16 May 13:00: TBC

Tue, 29/04/2025 - 12:36

TBC

Abstract not available

Speaker: Benjamin Elder, Imperial College London
Friday 16 May 2025, 13:00-14:00
Venue: MR20/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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Fri 09 May 13:00: TBC

Tue, 29/04/2025 - 12:34

TBC

Abstract not available

Speaker: Robbie Hennigar, Durham University
Friday 09 May 2025, 13:00-14:00
Venue: MR9/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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Fri 06 Jun 13:00: A Spacetime Interpretation of the Confluent Heun Functions in Black Hole Perturbation Theory

Tue, 29/04/2025 - 12:32

A Spacetime Interpretation of the Confluent Heun Functions in Black Hole Perturbation Theory

In Black Hole Perturbation Theory, confluent Heun functions appear as solutions to the radial Teukolsky equation, which governs perturbations in black hole spacetimes. While these functions are typically studied for their analytic properties, their connection to the underlying spacetime geometry has received less attention. In this talk, I will propose a spacetime interpretation of the confluent Heun functions, demonstrating how their behaviour near their singular points reflects the structure of key surfaces in Kerr spacetimes. By interpreting homotopic transformations of these functions as changes in the spacetime foliation, I will establish a connection between these solutions and various regions of the black hole’s global structure. I will also explore their relationship with the hyperboloidal formulation of the radial Teukolsky equation.

Speaker: Marica Minucci, Bohr Inst., Copenhagen
Friday 06 June 2025, 13:00-14:00
Venue: Potter room/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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Fri 30 May 13:00: Gravitational Wave Signatures of Dark Matter in Neutron Star Mergers

Mon, 28/04/2025 - 19:30

Gravitational Wave Signatures of Dark Matter in Neutron Star Mergers

Binary neutron star mergers provide insights into strong-field gravity and the properties of ultra-dense nuclear matter. These events offer the potential to search for signatures of physics beyond the standard model, including dark matter. We present the first numerical-relativity simulations of binary neutron star mergers admixed with dark matter, based on constraint-solved initial data. Modeling dark matter as a non-interacting fermionic gas, we investigate the impact of varying dark matter fractions and particle masses on the merger dynamics, ejecta mass, post-merger remnant properties, and the emitted gravitational waves. Our simulations suggest that the dark matter morphology – a dense core or a diluted halo – may alter the merger outcome. Scenarios with a dark matter core tend to exhibit a higher probability of prompt collapse, while those with a dark matter halo develop a common envelope, embedding the whole binary. Furthermore, gravitational wave signals from mergers with dark matter halo configurations exhibit significant deviations from standard models when the tidal deformability is calculated in a two-fluid framework neglecting the dilute and extended nature of the halo. This highlights the need for refined models in calculating the tidal deformability when considering mergers with extended dark matter structures. These initial results provide a basis for further exploration of dark matter’s role in binary neutron star mergers and their associated gravitational wave emission and can serve as a benchmark for future observations from advanced detectors and multi-messenger astrophysics.

Speaker: Violetta Sagun, University of Southampton
Friday 30 May 2025, 13:00-14:00
Venue: Potter room/Zoom.
Series: DAMTP Friday GR Seminar; organiser: Xi Tong.

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Fri 02 May 13:00: The Black Hole Threshold

Mon, 28/04/2025 - 12:16

The Black Hole Threshold

Numerical evolutions show that, in spherical symmetry, as we move through the solution space of GR to the threshold of black hole formation, the resulting spacetimes tend to display a surprising degree of simplicity. A heuristic description of this behavior, called critical collapse, has been built around this empirical fact. Less is known when symmetry is dropped. In this presentation I will review the current status of the topic, focusing in particular on the struggle to understand the situation in axisymmetry.