Gravitational Probes of the Early Universe

4 Jun 2025, 10:00 → 6 Jun 2025, 14:20 Europe/London

TBC (Strand Campus King's College London)

Lucien Heurtier (King's College London), Panagiotis Giannadakis (King's College London)

Early Universe cosmology is a growing field of research in which gravity plays a crucial role, from the primordial evolution of cosmic perturbations to the way it shaped our observable universe today. One of the biggest challenges of early universe theories is to identify clear observables that can be used to test such theories. Gravitational relics, such as primordial black holes or gravitational waves, are examples of such probes and will be at the centre of this workshop.

This event is organised by King's College London and funded by the Global Engagement Fund, aiming to create new collaborations between King's College London and international institutions.

Registration includes lunch, a reception, and a conference dinner. Note that the workshop will start in the late morning on Wednesday and end at the beginning of the afternoon on Friday to allow time for participants to travel to and back from the workshop. 

Location(s): 

• Wednesday/Thursday: Macadam Building (Map Link Here), room MB 4.2
• Friday: King's Building (Map Link Here), room K3.11

 

Conference Dinner: 19:30 at the Ciao Bella restaurant (https://ciaobellarestaurant.co.uk/), which is located here: https://maps.app.goo.gl/jwSjBJ3UroPxTnmw8

Confirmed Speakers:

Thomas Colas (University of Cambridge)

Joe Conlon (University of Oxford)

Djuna Croon (Durham University)

Yann Gouttenoire (LPTHE, Paris)

Andrew Gow (University of Portsmouth)

Aaron Held (ENS, Paris) 

Laura Iacconi (QMUL, London)

Yann Mambrini (IJCLab, Orsay)

David Marsh (King's College London)

Swagat Mishra (University of Nottingham)

Daniele Steer (ENS, Paris)

Vincent Vennin (ENS, Paris)

David Wands (University of Portsmouth)

 

Organisers: 

 

Lucien Heurtier

Macolm Fairbairn

Pannagiotis Giannadakis

Ruth Gregory

Eugene Lim

Mairi Sakellariadou

 

 

Wednesday 4 June

10:00 → 10:30 Registration

10:30 → 10:35 Opening Words

10:35 → 11:30 Axion phenomenology from string theory to the lab

Axions are a hypothetical class of particle predicted in a variety of settings and of utility in solving many mysteries of theoretical physics, most notably as dark matter candidates and solving the strong CP problem. I will describe recent dramatic progress in understanding what string theory predicts about the properties of axions, and the door this opens to test quantum gravity with cosmological observations, and in the lab. I will thus describe the cosmology of axions, how they differ from other dark matter candidates, and how we might discover evidence for them. Axion stars and axion miniclusters are novel sources of grvitational waves and multimessenger probes of the pre-reionization Universe. Axion haloscopes experiments can be repurposed for high frequency gravitational wave searches. Recently discovered axion quasiparticles can be used not only to detect axion dark matter but also as "analogue" laboratories for exotic physics, such as the gravitational Chern-Simons interaction.

Speaker: David Marsh (King's College London)

Marsh_String_Lab.pdf

Marsh_String_Lab.pptx

11:30 → 12:45 Lunch at Bushouse Restaurant

12:45 → 14:15 TPPC Seminar (Strand Building): David Tong

mapBushHouse.png

14:15 → 15:00 Open effective field theories for primordial gravitational waves

Speaker: Thomas Colas (DAMTP - University of Cambridge)

OpenGW.pdf

15:00 → 15:30 Coffee Break

15:30 → 16:15 WIMPs and New Physics Interpretations of the PTA Signal are Incompatible

Speaker: Yann Gouttenoire (MITP)

KCL_2025_YG.pdf

16:15 → 17:15 Gravitational microlensing and the dark (and early) Universe

Speaker: Dr Djuna Croon (IPPP Durham)

KCL25.pdf

17:15 → 19:15 Reception

Thursday 5 June

09:00 → 09:45 Practical challenges in stochastic inflation

Speaker: Andrew Gow (Institute of Cosmology and Gravitation, University of Portsmouth)

20250605 GOW, Andrew.pdf

09:45 → 10:45 Harvesting primordial black holes from stochastic trees

Speaker: Vincent VENNIN (LPENS Paris)

Kings_2025.pdf

network.html

network.pdf

10:45 → 11:15 Coffee Break

11:15 → 12:00 Cosmic Stasis

Speaker: Lucien Heurtier

Heurtier_stasis.pdf

12:00 → 13:00 New cosmological results from the Atacama Cosmology Telescope

I will show new results from the Atacama Cosmology Telescope (ACT), including cosmological constraints from the sixth data release. Using data gathered from 2017 - 2022, the new maps cover 40% of the microwave sky with five times the angular resolution and three times the depth in polarization as the Planck satellite. The improved cosmic microwave background (CMB) measurements at small scales complement the larger-scale information from Planck. I will describe how we use these datasets, along with tracers of large-scale-structure, to test the cosmological model and probe fundamental physics.

Speaker: Jo Dunkley

kcl_jun5_dunkley.pdf

13:00 → 14:00 Lunch at Bushouse Restaurant

14:00 → 15:00 Induced gravitational wave probes of the primordial black hole reheating scenario

Speaker: Yann MAMBRINI

15:00 → 15:30 Coffee Break

15:30 → 16:30 Superstring Phases in the Early Universe

Speaker: Joseph Conlon (Oxford University)

16:30 → 17:00 Cosmological trackers from perturbations

Speaker: Martin Mosny (University of Oxford)

KCLTalk.pdf

17:00 → 17:30 Inflation with Numerical Relativity

Speaker: Panagiotis Giannadakis (King's College London)

Early Universe Workshop Inflation.pdf

19:30 → 21:30 Workshop Dinner

Friday 6 June

09:30 → 10:15 Inflationary Gravitational Waves as a Probe of the Unknown Expansion History of the early Universe

Speaker: Swagat Saurav Mishra (University of Nottingham, UK)

SSM_GWs_KCL_2025.pdf

10:15 → 10:45 Coffee Break

10:45 → 11:45 Mapping inflationary loop corrections to boundary terms

Speaker: Dr Laura Iacconi (Queen Mary University of London)

11:45 → 12:30 Stability of ghostly interactions in classical field theories

I will demonstrate that opposite-sign kinetic terms are no obstruction for long-lived classical motion. I start with a class of polynomial point-particle models for which integrability allows to prove global stability despite the presence of opposite-sign kinetic terms and identify respective physical criteria for the interaction potential. I then generalise to (1+1) dimensional scalar field theories to clarify that (i) even the unquenched classical instability is not instantaneous, (ii) higher frequency modes become more not less stable, and (iii) heavy ghosts can be integrated out. Finally, I connect the above insights to recent progress concerning well-posed classical time evolution in higher-derivative theories of gravity. The latter opens up a novel pathway to access the strong-field regime in gravitational effective field theories. I look forward to discussing implications for cosmology.

Speaker: Aaron Held

12:30 → 12:35 Final Words

12:40 → 14:10 Lunch at Bushouse Restaurant