Fri 02 May 13:00: 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.
- Speaker: David Hilditch, IST Lisbon
- Friday 02 May 2025, 13:00-14:00
- Venue: Potter room/Zoom https://cam-ac-uk.zoom.us/j/87235967698.
- Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.
Thu 01 May 16:00: Irradiated brown dwarfs
Brown dwarfs are often described as failed stars, however the flip side of this description is that they can also be described as over-ambitious planets. With masses between 13-70 Jupiter masses they have cool atmospheres dominated by cloud features, molecules and show features due to weather. These atmospheres have a lot of similarities with atmospheres we see in planets in our solar system, and also directly imaged exoplanets. The question then is: How like hot Jupiters are irradiated brown dwarfs? In this seminar I will describe the known irradiated brown dwarfs and how they evolve into post-common envelope systems containing a white dwarf. These rare binaries have very short periods (~hrs) and the brown dwarf is irradiated by the white dwarf companion, often with large amounts of UV radiation. I will discuss the atmospheres of these highly irradiated brown dwarfs and their similarities with irradiated exoplanets.
- Speaker: Dr Sarah Casewell
- Thursday 01 May 2025, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Fri 20 Jun 13:00: TBC
Abstract not available
- 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: Xi Tong.
Fri 30 May 13:00: TBC
Abstract not available
- 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.
Fri 16 May 13:00: TBC
Abstract not available
- Speaker: Benjamin Elder, Imperial College London
- Friday 16 May 2025, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Fri 09 May 13:00: TBC
Abstract not available
- Speaker: Robbie Hennigar, Durham University
- Friday 09 May 2025, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Mon 16 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Gavin Coleman [Queen Mary University London]
- Monday 16 June 2025, 14:00-15:00
- Venue: Venue to be confirmed.
- Series: DAMTP Astrophysics Seminars; organiser: Thomas Jannaud.
Thu 05 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Jonathan Squire [Otago, New Zealand]
- Thursday 05 June 2025, 14:00-15:00
- Venue: MR20 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Loren E. Held.
Mon 02 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Florence Marcotte [Université Côte d'Azur, Nice, France]
- Monday 02 June 2025, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Mattias Brynjell-Rahkola.
Mon 12 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Maarit Korpi-Lagg [Helsinki/Espoo]
- Monday 12 May 2025, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Mattias Brynjell-Rahkola.
Mon 19 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Morgan Williams [Imperial College London]
- Monday 19 May 2025, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Thomas Jannaud.
Tue 27 May 14:00: Title to be confirmed
Abstract not available
- Speaker: David Melon-Fuksman [MPIA Heidelberg]
- Tuesday 27 May 2025, 14:00-15:00
- Venue: MR4 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Loren E. Held.
Thu 29 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Martin Pessah [NBIA Copenhagen]
- Thursday 29 May 2025, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Loren E. Held.
Tue 29 Apr 13:00: Formation of planetary cores in spontaneously generated dust traps during the secular evolution of magnetized protoplanetary disks
An outstanding gap in the current planet formation theory is about the first steps of the planet formation process; namely how, when and where the initially ISM like solid dust particles grow into pebbles and planetesimals, the building blocks of planetary cores. Protoplanetary disks provide the initial conditions for the planet formation process. They are weakly magnetized accretion disks that are subject to the magnetorotational instability (MRI), one of the main magnetized processes responsible for their angular momentum transport and gas turbulence. The nonideal magnetohydrodynamic (MHD) effects prevent the MRI from operating everywhere in PPDs, leading to a complex dichotomy between MRI active regions with higher gas turbulence and non-MRI regions with lower gas turbulence. In this talk, I will present the first numerical framework that describes the evolution of PPDs over millions of years powered by the MRI . It captures the MRI driven gas evolution via nonideal MHD calculations, which accounts for the dynamics and growth of the solid dust particles. An MRI powered mechanism that can spontaneously generate short- and long-lived pressure maxima in the PPD is unveiled. Within the long-lived pressure maxima, solid dust particles can be efficiently trapped, grow into pebbles, and reach high enough dust-to-gas mass ratios to potentially trigger the formation of planetesimals via the streaming instability. These planetesimals and pebbles can further rapidly interact to form planetary cores.
- Speaker: Timmy Delage (Imperial)
- Tuesday 29 April 2025, 13:00-14:00
- Venue: Ryle seminar room + ONLINE - Details to be sent by email.
- Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.
Fri 25 Apr 11:30: The Thesan-Zoom simulations: Studying high-redshift galaxy formation with cosmological radiation-hydrodynamics simulations
Abstract not available
- Speaker: Ewald Puchwein (AIP)
- Friday 25 April 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Mon 09 Jun 13:00: Title to be confirmed
Abstract not available
- Speaker: Gianmassimo Tasinato (Swansea University)
- Monday 09 June 2025, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Fri 25 Apr 13:00: Black hole radiation from non-vacuum initial states
Hawking derived the black hole thermal radiation state by comparing the vacuum state at the future null infinity I+ with that at the past null infinity I-. We revisit Hawking’s computation, considering a non-vacuum initial state at the past of the black hole geometry. We show in which cases the black hole radiation arising from the initial matter state differs from the well-known thermal state. We moreover classify what initial states are distinguishable from one another through measurements on the black hole radiation in this framework. Finally we provide a physical interpretation of the classification, using Algebraic Quantum Field Theory localisation.
- Speaker: Ali Akil, Hong Kong University
- Friday 25 April 2025, 13:00-14:00
- Venue: Potter room/Zoom: https://cam-ac-uk.zoom.us/j/88420112623?pwd=uogMItLtNT8pn4aks1hO4nJVmonbpV.1.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Mon 06 Oct 13:00: Title to be confirmed
Abstract not available
- Speaker: Etienne Camphuis (Institut d'Astrophysique de Paris)
- Monday 06 October 2025, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Fri 23 May 11:30: Between the extremes -- the physics of the first stars, galaxies, and black holes
The emergence of the first sources 13.6 billion years ago had a profound effect on the Universe, initiating its last major phase-change and ending the so-called Cosmic Dark Ages. Unlocking the physics of those primordial sources thus represents a fundamental step towards a comprehensive understanding of the initial conditions that formed the building blocks for the Universe we see today. While Hubble painted a fairly straight forward picture, early JWST data revealed an infant Universe far more remarkable and exotic than previously thought, with hyper-luminous galaxies detected out to z=14, chemically-enriched and Nitrogen-enhanced interstellar media out to z=12, and apparently over-massive black holes to z=10. Are these sources representative of the global population, or do they reflect peculiar objects at a particular evolutionary phase? In this talk I will present efforts to address these questions through the spectroscopic study of statistical samples of high-redshift (z>5-14) galaxies with JWST /NIRSpec, establishing a benchmark for their chemical enrichment journeys, ISM conditions, (re)ionizing capabilities, and spectroscopic fingerprints. Additionally, I will showcase the importance of utilizing unbiased samples of galaxies to gain representative insight into the ISM conditions and evolutionary pathways of the most luminous populations uncovered by JWST .
- Speaker: Guido Roberts-Borsani (UCL)
- Friday 23 May 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Fri 30 May 11:30: Chasing the Light: Shadowing, Collimation, and the Rapid Growth of Infant Black Holes
Observations with the James Webb Space Telescope (JWST) have uncovered a substantial population of high-redshift broad-line active galactic nuclei (AGNs) characterized by moderate luminosities, weak X-ray emissions, and faint high-ionization lines, challenging conventional models of AGN activity. In this talk I will propose that these sources are accreting at super-Eddington rates, and discuss how such accretion flows, shaped by thick disk geometries and anisotropic radiation fields, may provide new insights into black hole growth in the early Universe.
- Speaker: Piero Madau (UCSC)
- Friday 30 May 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.