Wed 08 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Vyacheslav Rychkov, Institut des Hautes Études Scientifiques
- Wednesday 08 May 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Ronak M Soni.
Wed 01 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Eric Perlmutter, IPhT
- Wednesday 01 May 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Ronak M Soni.
Mon 20 May 13:00: Title to be confirmed
Abstract not available
- Speaker: Silvia Galli (Institut Astrophysique de Paris)
- Monday 20 May 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Fiona McCarthy.
Tue 19 Mar 11:15: Source dynamics and evolution of low-luminosity FRII radio galaxies
I will present new VLA observations that reveal the structure of a new population of low-luminosity FRII radio galaxies discovered in LoTSS. Fanaroff and Riley (1974) identified a luminosity break between their two morphological classes. FRIs are defined to be low-luminosity, centre bright jets and the higher luminosity FRI Is have jets that are edge brightened and terminate in hotspots. Using LoTSS DR1 , Mingo et al (2019) demonstrated an overlap in luminosity between FRI and FRII morphology rather than a clear divide, discovering a sub-sample of FRI Is with luminosities up to 3 magnitudes lower than the typical FR break. A population of low-luminosity FRI Is raises questions about their origins; are they older, fading FRI Is, or hosted by lower mass galaxies? Our new VLA observations of a sample of LoTSS-selected low-luminosity FRI Is allow us to make comparisons between the two FRII luminosity populations on the prevalence of hotspots, as well as morphological and spectral differences.
- Speaker: Dr. Bonny Barkus (University of Hertfordshire)
- Tuesday 19 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Fri 15 Mar 13:00: Fully general Cauchy evolution of asymptotically AdS spacetimes: the non-linear instability of Kerr-AdS
In addition to being at the core of the widely employed AdS/CFT correspondence, asymptotically anti-de Sitter (AdS) spacetimes with reflective boundary conditions can serve as the arena for a range of strong gravity effects: arbitrarily small perturbations are bound to remain in the bulk, where they continue to interact and typically become sizeable. Initially, I will review a numerical scheme that enables the Cauchy evolution of these spacetimes to be performed in full generality. Then, I will present the first simulations of the trapping mechanism occurring in the exterior of a Kerr-AdS black hole. This mechanism has been conjectured to cause a non-linear instability, the existence of which remains a topic of debate. The simulations offer insights into this debate, providing new perspectives on the non-linear instability of Kerr-AdS.
- Speaker: Lorenzo Rossi, Queen Mary University of London
- Friday 15 March 2024, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Tue 07 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Alvaro Ribas (IOA Cambridge)
- Tuesday 07 May 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.
Mon 11 Mar 13:00: Parity Violation in Cosmology
Parity symmetry is known to be violated in the weak interaction. Do the physical laws behind the unsolved problems of modern cosmology – cosmic inflation, dark matter, and dark energy – also violate parity symmetry? In this talk, we will discuss theoretical and observational possibilities of parity violation in cosmology, a topic that has received much attention in recent years.
- Speaker: Eiichiro Komatsu (MPA Garching)
- Monday 11 March 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Inigo Zubeldia.
Mon 13 May 13:00: Which universes does the no-boundary wave function favour?
Abstract not available
- Speaker: Jean-Luc Lehners (MPI for Gravitational Physics, Potsdam)
- Monday 13 May 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Tue 05 Mar 11:15: New Space & the CubeSat Revolution
CubeSats stand at the forefront of the New Space Revolution, a paradigm shift in space exploration characterised by reduced launch costs and increased accessibility to space. These miniature satellites, defined by their standardised dimensions and modular design, have emerged as a pivotal technology with some implications for research in astronomy. With their standardised dimensions and modular design, these Nanosatellites enable a wide range of experiments that were previously the domain of larger, more costly missions. In my talk, I aim to introduce you to valuable opportunities that can emerge by leading a CubeSat project with a special interest in payloads dedicated to astrophysics research. As a cost-effective space instrument, CubeSats unlock observational windows across the ultraviolet, far-infrared, and low-frequency radio spectra, which are inaccessible from Earth’s surface. Beyond their technical capabilities, these satellites enable sustained observations of celestial bodies over extended periods, free from the scheduling constraints of larger telescopes.
- Speaker: Dr. Dolev Bashi
- Tuesday 05 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Dr. Dolev Bashi.
Fri 08 Mar 13:00: The Fate of Matter Fields in Metric-Affine Gravity
General relativity (GR) exists in different formulations. They are equivalent in pure gravity but generically lead to distinct predictions once matter is included. After a brief overview of various versions of GR, I will focus on metric-affine gravity, which avoids any assumption about the vanishing of curvature, torsion, or nonmetricity. With a view toward the Standard Model, we can construct a generic model of (complex) scalar, fermionic, and gauge fields coupled to GR and derive an equivalent metric theory, which features numerous new interaction terms. There are multiple phenomenological consequences, which I will detail: an improved setting for Higgs inflation, a new (purely gravitational) production channel for fermionic dark matter, and an outlook on axion inflation.
- Speaker: Claire Rigouzzo (KCL)
- Friday 08 March 2024, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.
Tue 05 Mar 11:15: New Space & the CubeSat Revolution
CubeSats stand at the forefront of the New Space Revolution, a paradigm shift in space exploration characterised by reduced launch costs and increased accessibility to space. These miniature satellites, defined by their standardised dimensions and modular design, have emerged as a pivotal technology with some implications for research in astronomy. With their standardised dimensions and modular design, these Nanosatellites enable a wide range of experiments that were previously the domain of larger, more costly missions. In my talk, I aim to introduce you to valuable opportunities that can emerge by leading a CubeSat project with a special interest in payloads dedicated to astrophysics research. As a cost-effective space instrument, CubeSats unlock observational windows across the ultraviolet, far-infrared, and low-frequency radio spectra, which are inaccessible from Earth’s surface. Beyond their technical capabilities, these satellites enable sustained observations of celestial bodies over extended periods, free from the scheduling constraints of larger telescopes.
- Speaker: Dolev Bashi
- Tuesday 05 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Dolev Bashi.
Wed 06 Mar 14:00: Applying Quantum Computing to HEP
In this talk I will discuss several studies in which quantum computers have been proposed as tools for studying particle theories. The first study uses quantum annealers to implement simple scalar field theories and observe quantum tunnelling, which follows the expected analytic behaviour: for example the decay rate follows the WKB approximation. The second more recent idea uses photonic devices to implement quantum tunnelling. In principle in both of these studies we are observing non-perturbative effects, suggesting that these and similar methods may be of interest in understanding a wide range of phenomena. The talk will be pedagogical.
- Speaker: Steve Abel (IPPP)
- Wednesday 06 March 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Hannah Banks.
Mon 04 Mar 14:00: The First Ionization Potential Effect in Solar/Stellar Coronae and Winds
Since 1963, we have known, or at least suspected, that element abundances in the solar corona and wind are different to those in the photosphere. Elements that are predominantly ionized in the photosphere and chromosphere, e.g. Fe, Si, Mg, are observed to be enhanced in abundance once transported to the corona and wind by a factor of typically 3-4, while elements that are mainly neutral are relatively unaffected. Due to the dependence on the ionization potential, this phenomenon has been dubbed the First Ionization Potential (FIP) Effect. A model capturing the FIP and effect and the various modifications to it seen in different coronal regions and the solar wind invokes ion-neutral separation by the ponderomotive force due to Alfven and magnetosonic waves propagating through the chromosphere. This acts on ions, but not neutrals, and depends on the interaction of the waves with the magnetic geometry of the solar atmosphere.
The launch of the Extreme Ultraviolet Explorer (EUVE) in 1992 afforded us the first observations of abundances in stellar coronae. This, and succeeding missions like Chandra, XMM -Newton and Suzaku, have shown that solar-like stars show a similar FIP effect, which transitions to Inverse FIP (IFIP), i.e. a coronal depletion of Fe, Si, Mg, etc., as the activity level increases.
In this presentation, I will review the theoretical basis of FIP and IFIP fractionation by the ponderomotive force. Fractionation by such means is new to solar physics and astrophysics, but is not new to science. Manipulation of atoms, molecules, biological samples, etc. by the forces due to refraction of photons from lasers, known as “optical tweezers”, has a rather long history in optical sciences, and won Nobel Prizes for Steven Chu (in 1997) and Arthur Ashkin (in 2018). Our model is a precise analog of this work, but with magnetohydrodynamic waves instead of optical photons. This connection leads to a better physical understanding of the mechanisms at work in FIP fractionated plasma.
Work supported by NASA Heliophysics Supporting Research Program (80HQTR20T0076), and by Basic Research Funds of the Office of Naval Research.
- Speaker: Martin Laming (Naval Research Laboratory, Washington DC)
- Monday 04 March 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.
Mon 04 Mar 13:00: Fifth forces in and around galaxies
Light scalar fields are often considered as part of explanations for dark energy and dark matter. They also appear in theories in which gravity is modified on cosmological scales. If the scalar field theory has a screening mechanism, the fifth forces that the scalar mediates can be significant in the cosmological vacuum but suppressed on Earth and in the solar system. It has been claimed that current data from galaxy surveys is sufficient to exclude the possibility that these theories could be relevant on astrophysical or cosmological scales. In this talk I will consider how such scalar fields behave in galaxies, and show that they may not be excluded after all.
- Speaker: Clare Burrage (Nottingham)
- Monday 04 March 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Dr Dong-Gang Wang.
Fri 01 Mar 13:00: AdS Black Holes and Their Microstates
Investigating the fundamental origins of Bekenstein-Hawking entropy is a profound challenge in theoretical physics. This investigation is especially relevant for anti de Sitter (AdS) black holes, where it is proposed that the entropy can be explained through the microstates of the holographic dual quantum field theory, in line with the AdS/CFT correspondence. In this talk, I will review recent advancements in deriving the Bekenstein-Hawking entropy for various supersymmetric AdS black holes across different dimensions.
- Speaker: Seyed Morteza Hosseini, Imperial College London
- Friday 01 March 2024, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Tue 05 Mar 11:15: New Space & the CubeSat Revolution
CubeSats stand at the forefront of the New Space revolution, a paradigm shift in space exploration characterised by reduced launch costs and increased accessibility to space. These miniature satellites, defined by their standardised dimensions and modular design, have emerged as a pivotal technology with some implications of research in astronomy. With their standardised dimensions and modular design, these Nanosatellites enable a wide range of experiments that were previously the domain of larger, more costly missions. In my talk, I aim to introduce you to valuable opportunities that can emerge by leading a CubeSat project with special interest in payloads dedicated to astrophysics research. As a cost-effective space instrument, CubeSats unlock observational windows across the ultraviolet, far-infrared, and low-frequency radio spectra, which are inaccessible from Earth’s surface. Beyond their technical capabilities, these satellites enable sustained observations of celestial bodies over extended periods, free from the scheduling constraints of larger telescopes.
- Speaker: Dolev Bashi
- Tuesday 05 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Dolev Bashi.
Tue 27 Feb 11:15: Real-time pipelines for SKA — Progress and challenges
The Square Kilometre Array (SKA) will be the largest interferometric radio telescope to date, with unprecedented resolution and sensitivity to study various phenomena of the universe. In data processing pipelines for radio telescopes, real time calibration, such as beam former and pointing offset calibration, are crucial for obtaining high-quality interferometric data from the observations. As an example, I will discuss the design and ongoing implementation of the pointing offset calibration pipeline within SKA ’s data processing software, describing the steps carried out to integrate the pipeline into telescope execution control and data queue system, as well as outlining challenges and greater implications on the data processing algorithm and software within the radio astronomy community.
- Speaker: Dr. Ying-He Celeste Lü (Cavendish Astrophysics)
- Tuesday 27 February 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Mon 13 May 13:00: Title to be confirmed
Abstract not available
- Speaker: Jean-Luc Lehners (MPI for Gravitational Physics, Potsdam)
- Monday 13 May 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Mon 17 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Claudio Zanni (INAF Turin)
- Monday 17 June 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.
Mon 10 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Chris Osborne (Glasgow)
- Monday 10 June 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.