UK-QFT XIV

Contribution List

9. Matter Sourced Bubble Nucleation in the Asymmetron Scalar-Tensor Theory

Usama Syed Aqeel (University of Nottingham)

26/11/2025, 10:00

Talk

I

We investigate how matter density distributions affect thin-wall bubble formation in the asymmetron mechanism, a scalar–tensor theory with a universal coupling to matter and explicit symmetry-breaking, and analyse the stability of its metastable state. We show that the screening mechanism of the asymmetron inside dense objects induces a surface tension associated with the boundary of the...

3. Quantum Corrections to Fifth Forces

Michael Udemba (University of Manchester)

26/11/2025, 10:25

Talk

I

Non-linear scalar-tensor theories of modified gravity may explain observations attributed to dark matter and dark energy. Much is understood of their classical properties, but their quantum nature is relatively unexplored. We discuss a Green's function method for obtaining the leading order quantum corrections to the classical symmetron field in the vicinity of a spherically symmetric extended...

17. Hawking radiation from double-copy

Karthik Rajeev (University of Edinburgh)

26/11/2025, 10:50

Talk

I

Gravity and gauge theory are connected in a precise way through the double copy correspondence. While this relationship has been extensively explored in the context of perturbative scattering in vacuum, much less is understood about its non-perturbative features or its extensions to nontrivial backgrounds. In this work, we demonstrate how Hawking radiation in a collapsing spacetime—along with...

15. Spectral Functions of Lorentzian Quantum Gravity

Gabriel Assant

26/11/2025, 11:45

Talk

II

The asymptotic safety scenario, according to which a quantum field theory of gravity is made non-perturbatively renormalizable via an interacting renormalisation group fixed point, is a viable contender for the theory of quantum gravity.

Using modern functional RG methods adapted to Lorentzian signatures, we compute the asymptotically safe non-perturbative Kallen-Lehmann spectral functions...

11. Hamiltonian Truncation Framework for Gauge Theories on the Interval

James Ingoldby (Durham (IPPP))

26/11/2025, 12:10

Talk

II

Gauge theories in two dimensions provide a powerful testing ground for understanding strongly coupled quantum field theories. In this talk, I’ll present an alternative numerical approach based on Hamiltonian truncation for investigating these theories nonperturbatively. We work on a spatial interval and fix to axial gauge, eliminating gauge field degrees of freedom entirely, thus allowing us...

5. Lattice defect networks in 2d Yang-Mills

Elisa Iris Marieni (University of Southampton)

26/11/2025, 12:35

Talk

II

In the context of quantum field theory (QFT), there are no known examples of non-topological fully local theories. In the topological case, constructing a fully local theory is equivalent to finding all defects. We extend this framework to non-topological theories, proposing that defects might arise from quantising classical degrees of freedom. This idea seems particularly plausible within the...

2. An Open System Approach to Gravity

Lennard Dufner (University of Cambridge)

26/11/2025, 14:00

Talk

III

Several major open problems in cosmology involve spacetime-filling media with unknown microphysics, and can only be probed through their gravitational effects. This observation motivates a systematic open-system approach, in which gravity evolves in the presence of a generic, unobservable environment.

After a brief review of the Schwinger–Keldysh path integral formalism for open systems, I...

19. Counting degrees of freedom in open systems

Enrica Lausdei (University of Cambridge)

26/11/2025, 14:25

Talk

III

Cosmological systems involve unknown microphysics with which gravity interacts. To circumvent the lack of a precise description of all cosmic constituents, it is necessary to adopt an open-system approach, in which interactions between the fields of interest and an unspecified environment are modelled through dissipation and stochastic noise. Within this framework, the concept of physical...

12. Spinning Boundary Correlators from AdS4 Twistors

Theo Keseman (Imperial College London)

26/11/2025, 14:50

Talk

III

We develop a twistor-space framework to compute boundary correlators via a boundary limit of nested Penrose transforms in (A)dS$_4$. Starting from correlators of (anti-)self-dual bulk fields, the boundary limit reproduces the correlators of the dual conserved currents; we demonstrate this explicitly for two- and three-point functions. The two-point correlator is rendered finite by working in...

10. Massive spinning fields during inflation

Trevor Cheung (University of Nottingham)

26/11/2025, 15:15

Talk

III

There are two major descriptions of massive spinning fields during inflation, coined as cosmological collider (CC) physics and cosmological condensed matter (CCM) physics. We will go through each description, how it couples to the inflaton, and compare the cosmological signatures each description can produce. If time allows, we will also go into corrections to Feynman rules of the CC...

8. Vacuum decay in theories with no instanton solutions

Kinga Gawrych (Imperial College London)

26/11/2025, 16:10

Talk

IV

In QFT, a metastable vacuum state can decay through quantum tunnelling. The calculation of the decay rate relies on instantons — non-trivial classical solutions in the Euclideanized theory, saddle points of the Euclidean action. However, sometimes theories with metastable vacua do not have any instanton solutions, thus rendering the usual method of calculating decay rates unusable. An...

18. Gravitational Waves from Confinement in SU(N) Yang-Mills Theory

Rory Phipps (University of Sussex)

26/11/2025, 16:35

Talk

IV

The advent of gravitational wave astronomy has brought with it the potential for novel approaches to study physics beyond the Standard Model. In particular, the null searches for signatures of dark matter at direct and indirect detection experiments has left the so-called “nightmare scenario”, where the dark matter interacts with the Standard Model only through gravity, a distinct possibility....

16. EFT for strong phase transitions

Farbod Rassouli (University of Nottingham)

26/11/2025, 17:00

Talk

IV

I present an EFT framework for strong, indeed the strongest, cosmological phase transitions this is precisely where standard high-temperature dimensional reduction fails. After reviewing high-temperature dimensional reduction for weak and intermediate transitions and pinpointing where its standard assumptions fail we construct EFTs that remain valid for very strong transitions. The approach...