Opening Words Room: TBC

Axion phenomenology from string theory to the lab

• David Marsh (King's College London)

Room: TBC 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.

Open effective field theories for primordial gravitational waves

• Thomas Colas (DAMTP - University of Cambridge)

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WIMPs and New Physics Interpretations of the PTA Signal are Incompatible

• Yann Gouttenoire (MITP)

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Gravitational microlensing and the dark (and early) Universe

• Djuna Croon (IPPP Durham)

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Practical challenges in stochastic inflation

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

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Harvesting primordial black holes from stochastic trees

• Vincent VENNIN (LPENS Paris)

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Cosmic Stasis

• Lucien Heurtier

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New cosmological results from the Atacama Cosmology Telescope

• Jo Dunkley

Room: TBC 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.

Induced gravitational wave probes of the primordial black hole reheating scenario

• Yann MAMBRINI

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Superstring Phases in the Early Universe

• Joseph Conlon (Oxford University)

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Cosmological trackers from perturbations

• Martin Mosny (University of Oxford)

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Inflation with Numerical Relativity

• Panagiotis Giannadakis (King's College London)

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Inflationary Gravitational Waves as a Probe of the Unknown Expansion History of the early Universe

• Swagat Saurav Mishra (University of Nottingham, UK)

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Mapping inflationary loop corrections to boundary terms

• Laura Iacconi (Queen Mary University of London)

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Stability of ghostly interactions in classical field theories

• Aaron Held

Room: TBC 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.