[Astro] [CAPT] Particle Cosmology and Gravity Seminars this week

Swagat Mishra Swagat.Mishra at nottingham.ac.uk
Thu Oct 10 13:21:39 BST 2024 

A gentle reminder of today's seminar


  1.
Speaker: Kieran Wood (Nottingham)

            Seminar date: 10 October, Thursday 3 pm (Journal Club time)

           Venue: Seminar Room A 113

            Title: Multi-metric black holes and the Gregory-Laflamme instability

Abstract: Multi-metric gravity is the umbrella term for a class of modified gravitational theories, motivated by a number of problems at the interface between gravity and particle physics, that extend general relativity (GR) via the inclusion of additional interacting massive spin-2 fields beyond the single massless graviton of GR. Nonlinearly, the extra interactions manifest as a framework where multiple metric tensors interact with one another on the same spacetime manifold (hence the name). To date, black hole solutions of these multi-metric theories are only understood for the simplest case of bigravity (N=2 metrics) in 4 dimensions. It is, for example, known that one class of bigravity black holes is unstable for certain values of the graviton mass, with the instability taking the same form as the notorious Gregory-Laflamme (GL) instability plaguing higher dimensional black strings, although this feature has previously been viewed as little more than a peculiarity. In this talk, I will show how to generalise the 4d bigravity results to the full multi-metric theory in arbitrary dimension, constructing a wide class of black hole solutions of the general theory, and determine their linear stability. I will also elucidate the link between the instabilities of these multi-metric black holes and those of higher dimensional black strings. The result seems to suggest that the GL instability may be more fundamentally linked to the nature of massive spin-2 interactions.


Link to join: https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d

With Regards,
-Swagat



Swagat Saurav Mishra,

Postdoctoral Research Associate

​

Particle Cosmology Group,

Centre for Astronomy and Particle Theory,

University of Nottingham, Nottingham NG7 2RD, UK.

Website: https://swagatam18.wordpress.com/

Research Link:https://inspirehep.net/authors/1517353

________________________________
From: Maths-quantum-gravity-group <maths-quantum-gravity-group-bounces at lists.nottingham.ac.uk> on behalf of Swagat Mishra <Swagat.Mishra at nottingham.ac.uk>
Sent: 07 October 2024 08:00
To: capt at nottingham.ac.uk <capt at nottingham.ac.uk>; maths-quantum-gravity-group at lists.nottingham.ac.uk <maths-quantum-gravity-group at lists.nottingham.ac.uk>; O365-Gravity Laboratory <o365-gravitylaboratory at UniofNottm.onmicrosoft.com>
Cc: Ella Batchelor (staff) <ppzeb1 at exmail.nottingham.ac.uk>; Drande Patogu <ppydp10 at exmail.nottingham.ac.uk>; Bobby Acharya <bacharya at ictp.it>
Subject: [Maths-quantum-gravity-group] Particle Cosmology and Gravity Seminars this week

Dear All,
                    We have two seminars this week, as given below.

  1.
Speaker: Theo Anton  (QMUL)

            Seminar date: 8 October, Tuesday 1 pm

           Venue: Seminar Room A 113

            Title: Generalised tests of gravity in cosmology

Abstract: A plethora of modified theories of gravity have been proposed over the last several decades. Testing them all observationally is a considerable challenge, so it is advantageous to develop theory-independent approaches that constrain deviations from General Relativity in a systematic way. Many of the most precise such constraints to date are obtained from astrophysical measurements, for which deviations from GR are described by the parameterised post-Newtonian (PPN) parameters. Some attempts have been made to perform similarly general tests on cosmological scales, but it is not clear that they refer to the same couplings as the PPN formalism does, and so interpreting results from these disparate regimes physically is difficult and potentially misleading. With that problem in mind, I will introduce a framework, called parameterised post-Newtonian cosmology, that allows information from cosmological and astrophysical regimes to be combined consistently. I will present novel constraints on the evolution of the PPN parameters over cosmic history, using data from CMB anisotropies and Solar System experiments concurrently, and I will explain how these ideas can be further applied to test cosmological gravity to high precision.


  1.
Speaker: Kieran Wood (Nottingham)

            Seminar date: 10 October, Thursday 3 pm (Journal Club time)

           Venue: Seminar Room A 113

            Title: Multi-metric black holes and the Gregory-Laflamme instability

Abstract: Multi-metric gravity is the umbrella term for a class of modified gravitational theories, motivated by a number of problems at the interface between gravity and particle physics, that extend general relativity (GR) via the inclusion of additional interacting massive spin-2 fields beyond the single massless graviton of GR. Nonlinearly, the extra interactions manifest as a framework where multiple metric tensors interact with one another on the same spacetime manifold (hence the name). To date, black hole solutions of these multi-metric theories are only understood for the simplest case of bigravity (N=2 metrics) in 4 dimensions. It is, for example, known that one class of bigravity black holes is unstable for certain values of the graviton mass, with the instability taking the same form as the notorious Gregory-Laflamme (GL) instability plaguing higher dimensional black strings, although this feature has previously been viewed as little more than a peculiarity. In this talk, I will show how to generalise the 4d bigravity results to the full multi-metric theory in arbitrary dimension, constructing a wide class of black hole solutions of the general theory, and determine their linear stability. I will also elucidate the link between the instabilities of these multi-metric black holes and those of higher dimensional black strings. The result seems to suggest that the GL instability may be more fundamentally linked to the nature of massive spin-2 interactions.


Link to join: https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d


[cid:92c71ee3-6d9f-4702-90c9-b28b609b0ff2]<https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d>
Join conversation<https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d>
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A list of upcoming seminars for this term (with rough titles)

·   15 Oct | Eemeli Tomberg (Lancaster U) | Compaction function for Primordial Black Holes
·    22 Oct | Ayngaran Thavanesan (DAMTP Cambridge) | Cosmological CPT theorem
·    29 Oct | Santiago Agui Salcedo (DAMTP Cambridge) | Open EFT for inflation
·    05 Nov | Yuyu Mo (Edinburgh Higgs Centre) | Bootstrap
·   12 Nov | Alex Jenkins (UCL) | Quantum Matter, Analogue Gravity
·   19 Nov |  Bjoern Friedrich (Heidelberg) | String Phenomenology
·    26 Nov | Tamara Evstafyeva (DAMTP Cambridge) | Gravitational Waves
·    03 Dec | Emma Albertini (Imperial College London) | Gravity, Scattering Amplitudes
·    10 Dec | TBD

With Regards,
-Swagat



Swagat Saurav Mishra,

Postdoctoral Research Associate

​

Particle Cosmology Group,

Centre for Astronomy and Particle Theory,

University of Nottingham, Nottingham NG7 2RD, UK.

Website: https://swagatam18.wordpress.com/

Research Link:https://inspirehep.net/authors/1517353

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