YTF 23

14 Dec 2023, 14:00 → 15 Dec 2023, 17:15 Europe/London

Centre for Particle Theory

Welcome to YTF 2023! 

YTF exists to bring together postgraduate students working in theoretical physics/applied maths and encourage them to share their research. YTF 23 is a great opportunity for presenting your work, while also engaging and collaborating with students from different universities. YTF 23 will feature:

• 20 minute talks, with 5 minutes of questions 
• Gong Show Talks (shorter 5 minute talks)
• Evening poster session  

There will also be a talk from a plenary speaker, this year it will be Clare Burrage from University of Nottingham!

YTF 23 will be held at Durham University over two days: Thursday 14th and Friday 15th December 2023, registration is on a first-come first-served basis.

We want to make sure YTF is as inclusive as possible. All attendees must abide by the code of conduct and any breaches or concerns can be reported to the EDI officer who will be present during the conference. A quiet room will be provided at the venue. All talks will be broadcast on Zoom, and closed captions will be automatically generated for all talks. All presenters are encouraged to consider using colour-blind friendly styles for their materials.

If you have any childcare needs during YTF please feel free to contact us so we can help you in this regard.

In addition, please let us know through the registration form of any access requirements you have.

For information regarding travel and accommodation, please review the travel and accommodation tab.

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Topics expected to be discussed include:

• Amplitudes
• Astroparticle physics
• BSM physics
• Cosmology
• Flavour physics
• Generalised symmetries
• Gravity
• Holography
• Lattice QCD
• Machine learning
• Non-perturbative QFT
• Phenomenology
• QCD
• String theory
• SUSY

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If you have any questions, do get in touch with our communications officer Malina at malina.rosca@durham.ac.uk. You can also follow us on social media on Twitter (X) @Durham_YTF or Instagram @YTF_2023 to keep up-to-date with the latest from the team. 

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We could not hope to run this conference every year without the generous support of our sponsors to whom we are extremely grateful. For YTF 23 we are proud to be supported by:

• IOP HEPP Group
• IOP Mathematical and Theoretical Physics
• IOP Early Career Members
• UK Lattice Field Theory (UKLFT) Centre
• Fundamental Physics UK (FPUK) Virtual Centre
• Tshirt Studio

YTF_23_poster.pdf

Thursday, 14 December

General Address: Welcome & Introduction

Mia West & Samson Chan

Barbie Animated-2.pptx

Gong Show Talks

Chair: Guillaume Rostagni

1 Listening for dark matter: Macroscopic dark matter searches with acoustic neutrino detectors

Macroscopic Dark Matter (or Macros) are a general class of dark matter models with masses $\gtrsim M_{pl}$ (often parameterised in grams rather than GeV) and geometric cross sections $\sigma_\chi$. Due to their very low number density, the range of macro cross sections is relatively unconstrained by conventional DM detectors, and instead require novel detection methods with high exposure. Here we consider the constraining power of proposed high exposure acoustic neutrino experiments to macroscopic dark matter.

Speaker: Damon Cleaver (King's College London)

YTF23Presentation_DamonCleaver_no_animations.pdf

YTF23Presentation_DamonCleaver.pdf

2 Computing Conformal 4-Point Functions

By the AdS-CFT correspondence, a 4-point function in a CFT is equal to the scattering amplitude of particle states in the dual AdS gravitational theory. These important functions can also tell us other things, such as the spectrum of operators in a theory, and are heavily researched objects. The expressions for general 2- and 3-point functions in a CFT have explicitly known and very simple forms but there is not a simple, general expression for 4-point functions. In my talk, I will briefly discuss different methods, which I will be using in future work, that have been found for both constraining and computing 4-point functions/scattering amplitudes. These include utilising the OPE, bootstrapping, working in Mellin space and using dispersive sum rules.

Speaker: Matthew Rochford (Department of Physics, University of Southampton)

Conformal 4-Point Functions Durham.pdf

3 A brief geometrical introduction to the Penrose Transform

In this talk, I'll introduce some of the ingredients and motivations in twistor theory and sketch the geometrical idea underlying the Penrose transform in the simplest non-trivial case.

Speaker: Diego Hernandez-Kent (University of Edinburgh)

DHernandez_YTF_Presentation.pdf_compressed.pdf

4 Phenomenological Predictions for Four Top Production at the LHC

A more accurate measurement of the cross section of the production of four top quarks in proton-proton collisions is now possible, thanks to the increased centre-of-mass energy and luminosity of the Large Hadron Collider (LHC). This motivates a corresponding improved accuracy for the theoretical predictions. I will begin the talk by explaining the reproduction of previously known results for differential cross section distributions for the production of four top quarks at LO and NLO. I will discuss the results of our new predictions at LO and NLO that are made with varied values of the mass of the top quark and with different Parton Distribution Function (PDF) sets, at varied renormalisation and factorisation scales. The implications of the results and their utility in determining the mass of the top quark with increased precision and constraining PDF sets will be highlighted.

Speaker: Mr Vishakha Lingadahally (Royal Holloway, University of London)

Durham_Four-Top_Vishakha.pdf

5 Manifestly Causal QFT

A new method of performing calculations in QFT is presented, in which algebraic manipulations are performed at the probability level and propagators are expressed in terms of Pauli-Jordan (commutator) and Hadamard (anti-commutator) functions. This novel approach can be made manifestly causal, with other potential advantages including avoiding infrared singularities. This method has been applied to particle scattering and 2-level Fermi atom calculations, with hopes to apply it to scenarios involving the Unruh effect and black hole geomteries.

Speaker: Ross Jenkinson (University of Manchester)

YTF_2023_Presentation_Ross_Jenkinson.pdf

6 What can Hidden Conformal Symmetries tell us about Black Holes?

It is well known that the Kerr and Reissner-Nordstrom geometries exhibit near-horizon conformal symmetries; in this talk I will present a brief introduction to hidden conformal symmetries, namely symmetries that are not immediately manifest in the background geometry. These hidden symmetries reveal interesting properties of our Black Hole systems, both in traditional General Relativity and further into modified gravity models. The implications of this will be discussed within the context of modern day gravitational wave experiments.

Speaker: Bill Atkins (Swansea University)

hidden conf symmetry.pdf

7 Re-Evaluation of the HVP Contribution to the Anomalous Magnetic Moment of the Muon

Recent results from the muon $g-2$ experiment at Fermilab suggest a possible discrepancy between the experimental value of and the theoretical prediction for the muon anomalous magnetic moment $a_\mu$. Results from lattice QCD and the recent CMD-3 experiment make the situation more complicated and raise further questions.

An updated theoretical prediction for $a_\mu$ should be prepared for comparison to the upcoming analysis of the Fermilab run 4 to 6 data. I will present work from updating the KNT compilation of hadronic cross section data used for the $a_\mu$ prediction, focusing on the creation of a relational database and the introduction of blinding to the analysis.

Speaker: Aidan Wright (University of Liverpool)

AWright_YTF_HVP_Presentation.pdf

8 Probing the curvature of the cosmos from quantum entanglement due to gravity

Ideas from quantum information theory are becoming increasingly useful to tackle problems in quantum gravity. Gravity mediated entanglement has emerged as a novel idea to understand whether the gravitational field is (at least perturbatively) quantum. If gravity is quantum then two massive particles must become entangled through their gravitational interaction. In this work, we seek to understand how this would play out for two massive particles in an expanding background. We show how the the background curvature manifests in the entanglement generated between two oscillating massive particles. More generally, we argue that gravity mediated entanglement is sensitive to the background curvature and can thus be a probe of spacetime curvature.

Speaker: Abhinove Nagarajan Seenivasan (The University of Sheffield)

YTF23_GME_GongTalk.pdf

9 Long-Lived Heavy Neutral Leptons in Cosmology

Heavy Neutral Leptons (HNLs) are a popular extension of the Standard Model to explain the lightness of neutrino masses and the matter-antimatter asymmetry through leptogenesis. Cosmology can constraint the regime of active-sterile neutrino mixing in a standard Seesaw scenario of neutrino mass generation for HNL masses around $m_N \lesssim 1$~GeV. Motivated by this, we analyse HNL-ALP coupling and its impact on cosmology. Following an analytic discussion of the Big Bang Nucleosynthesis, ALP populations and other cosmological facts which can constraint the nature of sterile neutrinos and ALPs.

Speaker: Zhong Zhang (UCL)

zhongzhangYTF23.pdf

15:10 Coffee Break

Beyond the Standard Model: EFTs

Chair: Tommy Smith

10 On-shell matching in effective field theories

Effective field theories (EFTs) have become an essential tool in the search of new physics beyond the Standard Model. The calculation of the Wilson coefficients of the EFT for specific new physics models is usually performed by matching off-shell one-light-particle irreducible Green functions, which requires an off-shell basis of effective operators. This so-called Green's basis includes some operators that are redundant and can be written in terms of a minimal, physical basis when computing on-shell observables. This reduction is traditionally achieved by applying field redefinitions and equations of motion (EOMs). However, the absence of a systematic way of identifying the optimal field redefinition, coupled with the limitation that EOMs are only valid up to linear order in the perturbative expansion, calls for the search of a more systematic approach to the reduction of the Green's basis.

Our proposed method consists on performing a tree-level on-shell matching between the Green's and the physical bases. This matching requires a delicate cancellation between non-local contributions in both theories that we sidestep by evaluating the amplitudes with randomly generated physical momenta. Here, we present the application of this procedure to the dimension-eight Green's basis reduction of a toy model consisting on a real scalar field with $\mathbb{Z}_2$ symmetry. Furthermore, we derive the reduction of a set of bosonic operators in the SMEFT.

Speaker: Javier López Miras (Universidad de Granada)

YTF2023-on-shell-matching-EFTs.pdf

11 Plan B: New Z′ models for B-anomalies

Observations of lepton flavour universality violating effects may hint at new physics, prompting analysis of the phenomenology for models with new heavy mediators of these effects, such as a $Z’$. A new physics field coupling to di-muon pairs may explain the anomalous B-meson decay measurements, including measurements of $b\rightarrow s\mu ^+ \mu ^-$ with the 2022 LHCb reanalysis of lepton flavour universality observables $R_K$ and $R_{K*}$. However, the reanalysis also poses the possibility of similar strength new physics couplings to di-electron pairs. These new interactions are naturally described on a TeV scale in the language of a dimension-6 SMEFT, with operators constrained to their most likely strengths by fits to data. We compare the statistical likelihood of couplings to di-muon and di-electron pairs, revealing new bounds for fits of a class of anomaly-free models which span scenarios encompassing dominant couplings for electrons to compare with muons. Pertinent measurements lead us to a close-to-optimal fit for a $3B_3-L_e-2L_{\mu}$ model, allowing us to draw conclusions about the likelihood of lepton flavour universality effects in this class of models.

Speaker: Anna Mullin (University of Cambridge)

YTF_AMullin(1).pdf

12 Froggatt-Nielsen Models Meet the SMEFT

The Froggatt-Nielsen (FN) mechanism is one of the oldest and simplest attempts at explaining the striking hierarchies observed in the fermion masses and mixings. Given that FN models give rise to the correct fermion masses and mixings by construction and that the new particles predicted by the models are typically assumed to be heavy, it is not clear if the models are experimentally falsifiable. In this talk, we try to shed light on the question of falsifiability by analysing the infrared features of FN models whilst staying maximally agnostic about the fine details of the model. We achieve our goal by writing down a FN effective field theory, capturing all the local interactions allowed in the ultraviolet, and matching it to the Standard Model effective field theory (SMEFT) at the tree- and 1-loop-level. Our results indicate a rich and non-trivial signature of FN models on the SMEFT Wilson coefficients, leaving us with concrete, falsifiable predictions that could be studied at current and future colliders.

Speaker: Eetu Loisa (University of Cambridge)

durham.pdf

Black Holes

Chair: Thomas Bartsch

13 Slowly-rolling scalars around rotating black holes

Primordial black holes could play a significant role in cosmological history, yet fully consistent treatments of their evolution remain limited. The well-known paradigm of slow-roll inflation treats a slowly evolving scalar field in an isotropic universe, and some authors have extended this to include a spherically symmetric black hole. In this talk, I will discuss recent analytic progress on understanding slowly-rolling scalar fields in rotating black hole backgrounds, representing a significant increase in the complexity of the problem. I will compare this with earlier treatments and results, which often neglect cosmological expansion.

Speaker: Lewis Croney (King's College London)

YTF 2023 PPT Final.pptx

14 Adiabatic inspirals under electromagnetic radiation reaction on Kerr spacetime

Consider an electrically charged particle orbiting a spinning black hole, described by the Kerr spacetime. As the charged particle moves it undergoes a radiation-reaction process, driven by the electromagnetic force, causing it to lose energy and angular momentum, inspiraling towards the black hole until the final plunge. In this work we calculate how the orbital parameters for eccentric orbits change along the inspiral. We make comparisons to gravitationally driven inspirals and non-relativistic Keplerian approximations based on the Abraham-Lorentz force law. We find the electromagnetic inspirals circularize less efficiently than gravitational inspirals, and we quantify the effect of the black hole spin.

Speaker: Ethan James German (University of Sheffield)

YTF_Presentation-8.pdf

15 Primordial Black Holes & Leptogenesis

Among mechanisms for generating the baryon asymmetry of the universe,
leptogenesis is attractive since it simultaneously explains the small
neutrino masses via the seesaw mechanism. Experiments offer some
valuable constraints, but the parameter space of even minimal
leptogenesis models are high-dimensional and difficult to probe
directly. However the parameter space of leptogenesis models can be
indirectly and severely constrained by populations of Primordial Black
Holes (PBHs). Also notoriously difficult to probe, PBHs may form via the
collapse of inflationary perturbations and inject particles and entropy
into the universe. PBHs can have masses as small as 1 gram, in this
limit they can evaporate completely so rapidly as to potentially affect
leptogenesis. In this talk I discuss how we can probe the parameter
spaces of PBHs via leptogenesis and vice versa. I also discuss recent
and ongoing works in the phenomenological consequences of hot-spots
around PBHs

Speaker: Jacob Gunn (University of Naples Federico II)

YTFslides.pdf

17:00 Coffee Break

CFTs & Holography

Chair: Jiajie Mei

16 Towards Momentum Space Correlators in N=4 SYM

Conformal invariance implies strong constraints on the form of correlation functions of gauge invariant operators, and these correlators diverge when their conformal dimensions satisfy certain relations. These divergences and their renormalization has been understood up to three-point functions and in general dimension, and for specific dimensions for holographic 4-point function in d=3. Going from odd to even dimensions increases the complexity of the analysis and in this work we discuss how to renormalize holographic 4-point functions in d=4. The analysis shows that new features arise and renormalization may impose constraints on the spectrum of the CFT.

Speaker: Pratyusha Chowdhury (University of Southampton)

Pratyusha_Chowdhury_YTF23.pdf

17 (Quasi)Poisson structures, reduction, affinization and enhancement of the $\text{AdS}_3$/$\text{CFT}_2$ correspondence

$\text{AdS}/\text{CFT}$ is one of the most striking correspondences in modern physics, establishing a rich and useful bridge between gravity and (conformal) gauge theories. In this talk we focus on the $\text{AdS}_3$/$\text{CFT}_2$ encarnation and use simple topological arguments to exhibit how the (quasi)Poisson structures on the phase spaces of both theories are in 1-1 correspondence. Additionally, we will indicate how this correspondence behaves under (Quasi)Poisson reduction, affinization and enhancement to supergroups. (This talk is based on joint work with Bernd Schroers).

Speaker: Juan Carlos Morales Parra (Heriot-Watt University)

JCMP_YTFPresentation.pdf

18 Exact results in large-N CFTs

Some CFTs permit exact evaluation of their CFT data; these often come from large-N limits. We review the calculation of these data, and observe the intricate structure of CFTs of tensorial type when considered as a function of continuous dimension.

Speaker: Ludo Fraser-Taliente (Oxford)

LFT - YTF 2023 - large-N CFTs.pdf

Lattice Physics

Chair: Samson Chan

19 Spectroscopy on the lattice using spectral density reconstruction.

Spectroscopy is a fundamental matter in lattice gauge theories. In this talk, I will inspect a new technique used to perform finite volume spectroscopy, i.e. fitting spectral densities. This will be shown, giving an overview of how I give estimation of such spectral density, and how I fit it, using a mixed representation ($N_{\rm f} = 2$ fundamental fermions and $N_{\rm as} = 3$ 2-index antisymmetric fermions) Sp(4) gauge theory as a case study. Estimation of systematics and comparisons with GEVP results will be discussed as well.

Speaker: Niccolo Forzano (Swansea University)

Seminar_YTF_2023.pdf

20 Towards interpretable machine learning with Restricted Boltzmann Machine

Restricted Boltzmann Machines (RBMs) are energy-based machine learning models inspired by the spin-glass system. Using its energy function, we can analyse its training dynamics in terms of statistical mechanics and map its hyperparameters to thermodynamic quantities. This interpretability unravels the black-box nature of the machine-learning process and allows us to understand the underlying mechanisms.

Speaker: Chanju Park (Swansea University)

cjpark_ytf.pdf

21 DK scattering and an exotic pole at the SU(3) flavour point using lattice QCD

With perturbative QCD unable to explain the phenomenon of confinement and predict the spectrum/dynamics of hadrons that comes with it, an alternative framework must be used. Lattice QCD along with the two-particle finite-volume formalism can be used to obtain scattering amplitudes non-perturbatively, whose analytic structure yields information about hadronic resonances.
      In this talk, I will discuss my recent project using this formalism to investigate $DK$ scattering in the $J^P=0^+$ open-charm sector with $SU(3)$ flavour symmetry. By considering equal up, down, and strange quark masses, the pole structure of this sector can be resolved into different $SU(3)$ flavour irreps and studied. We find a pole in the conventional flavour irrep consistent with quark model predictions and interesting physics in an exotic flavour sector.

Speaker: Daniel Yeo (University of Cambridge)

Poster Session & Dinner

22 Information recovery in JT gravity

Recent developments on the black hole information problem have shown how tools like the quantum extremal surface prescription and entanglement wedge reconstruction may be used to obtain a Page curve and reproduce the Hayden-Preskill decoding criterion. This poster is based on work where we applied these tools to study information recovery from black holes in a simple model of 2d gravity. We show how to reproduce the Hayden-Preskill decoding criterion with some refinements.

Speaker: Neil Talwar (Swansea university)

23 Worldline Monte Carlo: a numerical implementation of the first quantised approach to QFT

We present the Worldline Monte Carlo method, a direct numerical evaluation of quantum mechanical path integrals. We prove the validity of the method by simulating the QED effective action and we illustrate some improvements to the sampling trajectories with a quantum mechanical system. Finally, we discuss a numerical implementation for the evaluation of Grassmann path integrals with the aim of incorporating spin within the Worldline Monte Carlo formalism.

Speaker: Ivan Ahumada Hernandez (University of Plymouth)

YTF2023_Poster-Ivan.pdf

24 Quark Mass Anomalous Dimension in the mMOM Scheme to the Five Loop Level

We calculate the five-loop contribution to the quark bi-linear, ghost, gluon and quark field anomalous dimension for the minimal momentum subtraction (mMOM) scheme when fixed in the linear covariant gauge. The coupling constant gauge parameter plane is then analysed for fixed points with the corresponding critical exponents evaluated. which is used to consider bounds on the conformal window.

Speaker: Robert Mason

mMOM_5L_Anomalous_Dimensions_Poster-9.pdf

25 Deconfinement in Sp(4) gauge theory

In this contribution I will discuss how lattice simulations can be used to determine thermodynamic properties of physics beyond the standard model. Using the density of states method I analyse deconfinement in $Sp(4)$ pure Yang-Mills theory and demonstrate it's first order nature through the characteristic swallow-tail structure in the free-energy.

Speaker: David Mason (University of Swansea)

Deconfinement_in_Sp_4__gauge_theory-4-1.pdf

26 Generalised Global Symmetries

Over the past few years, the notion of global symmetry in quantum field theory has undergone a vast generalisation. This includes higher group symmetries as well as more exotic non-invertible symmetries. In my poster, I will try to motivate this generalised notion of symmetry and provide simple examples.

Speaker: Thomas Bartsch (Department of Mathematics, Durham University)

27 Implementation of Precision Parton Shower Physics into the Herwig Event Generator for LHC Simulation

My PhD project aims to enhance the Parton shower simulation of the Herwig event generator, which is used by particle physicists at the Large Hadron Collider to generate simulated data for comparing detector results and testing new models. My objective is to update the dipole parton shower to account for global recoil. This will make the simulation next to leading logarithmically accurate for global observables and leading logarithmically accurate for non-global observables.

Speaker: Siddharth Sule (The University of Manchester (UK))

s-sule-ytf-poster.pdf

Friday, 15 December

09:00 General Address: Friday Welcome

Livia Maskos

Gravity

Chair: Ryan Cullinan

28 Spacetime Charge and The End of Predictability

A novel theory has recently surfaced, proposing a generically covariant and anomaly-free canonical modified theory of gravity. This theory posits the emergence of a spacetime line element from phase space variables by ensuring the covariance of the metric components. Besides the holonomy-like correction resembling correction in the effective loop quantum cosmology, anomaly-free condition introduces an extra unfixed function denoted as $q$. This function must reverse its sign in tandem with the phase space momenta for the theory to maintain invariance under time reversal. As a result, this formulation brings forth the concept of spacetime charge. The current research demonstrates that in the presence of any non-vanishing spacetime charge, the vacuum solution comprises asymptotes separated by an Euclidean region. Notably, no physical trajectories can penetrate the transition surface, irrespective of its regular characteristics, which indicates the end of predictability. However, the Euclidean radius is replaced by a bouncing surface (minimum radius or wormhole throat), in the limit when the spacetime charge vanishes, which resurrected the black-to-white hole transition picture.

Speaker: Idrus Husin Belfaqih (University of Edinburgh)

29 Stability of Quantised Vortices in Two-Component Condensates

Vortices in quantum fluids, such as Bose-Einstein condensates, have discrete charges associated with their circulations. Higher charged quantum vortices have dynamical instabilities which arise from bound states inside the vortex core, resulting in vortex splitting. These multiply charged quantum vortices can be stabilised by adding a second component to the condensate. This talk will introduce this stabilisation mechanism, and explore some of its novel consequences such as orbit reversal and vortex recombination. This has potential applications in experiments looking to probe black holes via analogue gravity.

Speaker: Ansh Gupta (King's College London)

QFT: The Standard Model

Chair: Malina Rosca

30 The Semi-Leptonic Weak Hamiltonian: Going Beyond Two-Loops

The unitarity condition of the Cabibbo-Kobayashi-Maskawa provides an important precision test of the Standard Model. This test requires a good control of different theoretical contributions. In our work, we discuss the short-distance corrections to the weak effective theory as well as the lattice-to-continuum matching for the semi-leptonic four-fermion operator. We compare different renormalization schemes used in the computation of these radiative corrections, namely the $W$-Mass scheme and the $\overline{\rm MS}$ scheme. We also discuss the calculation of the two-loop $\mathcal{O}(\alpha \alpha_s)$ electroweak corrections and the corresponding three-loop $\mathcal{O}(\alpha\alpha_s^2)$ anomalous dimension for the effective theory Wilson coefficient. We also present numerical results for the $\mathcal{O}(\alpha \alpha_s)$ conversion factor to the regularisation independent scheme, which is used in Lattice calculations.

Speaker: Francesco Moretti (University of Liverpool)

YTF_2023_Talk.pdf

31 Crewther's relation in gauge-parameter dependent schemes

We discuss Crewther's relation for gauge-parameter dependent scheme and present an extension to this relation that includes terms codifying the running of the gauge parameter. We argue for the new form of this relation holding in a variety of renormalization schemes and with different gauge fixing terms as evidenced by fixed point data and renormalization group transformations. The Crewther relation structure is then presented for the minimal momentum subtraction scheme.

Speaker: Robert Mason

Crewthers Relation in Gauge Parameter Dependent Schemes.pdf

32 QED Sum Rules in B physics

In the era of precision phenomenology, quantum electrodynamic (QED) effects are of increasing relevance. However traditional interpolating operators used for dispersive sum rule calculations do not conserve charge. We study QED corrections to leptonic B decays in a new manifestly gauge invariant formalism paying particular attention to large collinear logarithms. Using the same techniques we also can predict heavy meson isospin mass differences in a model independent way.

Speaker: Matthew Rowe (Edinburgh)

YTF23_Talk_Matt_Rowe_final.pdf

10:40 Coffee Break

Beyond the Standard Model: New Particles

Chair: Sofie Nordahl Erner

33 A Flavour of Grand Unified Composite Higgs

Composite Higgs models present an elegant solution to the naturalness issue associated with the Higgs mass. Furthermore, due to the supposition of new physics at the TeV scale, the flavour physics associated with these models must be non-generic in order to pass tight experimental constraints. This talk presents research into extending a composite Higgs model based off an $SO\left(11\right) / SO\left(10\right)$ global symmetry breaking pattern, to include all three generations of fermions in a manner that is consistent with observation.

Speaker: Matthew Starbuck (University of Sussex)

YTF talk Matt Starbuck.pdf

34 Combating gravity gradient noise in atom interferometer searches for ultra-light dark matter

Several upcoming experiments propose using new quantum sensing technology, long-baseline atom interferometers (AIs), to search for new fundamental physics including gravitational waves and ultra-light dark matter (ULDM). Previous studies have shown the sensitivity of AIs to scalar ULDM, but there are higher-spin bosonic candidates that these experiments could be sensitive to including vector ULDM (e.g. dark photons) and tensor ULDM (e.g. massive gravitons from bi-metric theory). Different models have varying phenomenology which needs to be accounted for when these experiments come online in the coming years.

However, another important consideration is the noise-limited sensitivity of these terrestrial experiments. One of the biggest noise sources comes in the form of local gravitational fluctuations from seismic, atmospheric and even human/animal-sourced activity. In this talk I will characterise these noise sources and show their impact on experimental searches for different models of ULDM, offering potential mitigation strategies and detection limits.

Speaker: John Carlton (King's College London)

YTF_2023_JC.pdf

String Theory

Chair: Rūdolfs Treilis

35 Understanding the target space of string theory at large alpha'

As a theory of quantum gravity, string theory is defined perturbatively around a fixed background metric. We quantify these perturbations to the metric using the inverse string tension, alpha'. We usually consider the supergravity limit of small alpha', yet it known to be possible to study beyond this regime when the background takes the form of a group manifold, such as AdS3. In this talk, I will discuss the interpretation of the target space geometry in the minimal tension limit of string theory on AdS3. We will find that the theory is most naturally written in the language of twistor theory and yet it will be possible to reinstate a more conventional spacetime interpretation. Time permitting, we will discuss applications to AdS/CFT.

Speaker: Nathan McStay (University of Cambridge)

YTF - Understanding the target space of string theory at large alpha prime.pptx

36 Courant Algebroid Relations and T-duality

We develop a new approach to T-duality based on Courant algebroid relations which subsumes the usual T-duality as well as its various generalisations. We introduce the relation associtated to Courant algebroid reduction, and describe how to transfer the information of generalised metrics through the reduction, via transverse generalised metrics and isometries. This is used to construct T-dual backgrounds as generalised metrics on reduced Courant algebroids which are related by a generalised isometry. There is a existence and uniqueness result for generalised isometric exact Courant algebroids coming from reductions.

Speaker: Thomas De Fraja (Heriot-Watt University)

CArelationsslides (2).pdf

12:00 Buffet Lunch

Plenary Speaker: Professor Clare Burrage

What is dark energy and how do we find it?

I will briefly review the cosmological constant problems, and our motivations for indroducing a new dark energy component into our model of cosmology. I will discuss why this motivates us to think about including light scalar fields which can mediate fifth forces. We will discuss how non-linearities can change the behaviour of these fifth forces, both allowing them to hide from traditional searches as well as allowing new opportunities for detection.

Chair: Tom Stone

YTF_2023.pptx

14:00 Coffee Break

QFT: Formal Aspects

Chair: Lucca Fazza Macron

37 Aspects of dimensional reduction in thermal QFT

As a quantum field theory (QFT), the Standard Model describes particle interactions at zero temperature with remarkable accuracy. However, at high temperatures, such as those in the early universe, its constituents become an interacting plasma of elementary particles which is best described by combining quantum statistical mechanics with relativistic field theory. One of the preferred formalisms in thermal QFT is the imaginary time, or Matsubara, formalism in which time is compactified and fields are decomposed into Fourier modes, with different thermal masses, that live in a three-dimensional Euclidean space. At sufficiently high temperatures, the heavy Matsubara modes can be integrated out and all thermodynamical variables can be computed from a three-dimensional effective theory (3dEFT) where the Wilson coefficients explicitly depend on the temperature scale.

In this talk we will summarize the key concepts in this thermal QFT formalism. We will then present a description of the EFT-building procedure and apply it to the dimensional reduction of a simple real scalar field theory with $\mathbb{Z}_2$-symmetry to a perturbative order higher than previously worked out in the literature, particularly including operators with up to four derivatives which are instrumental in the search for stable non-trivial topological field configurations, and potentially also for an accurate prediction of the parameters of first order phase transitions.

Speaker: Luis Gil Martín (Universidad de Granada)

GilMartin_TQFT.pdf

38 Null energy bounds for non-minimally coupled scalar fields

Quantum energy inequalities (QEIs) are restrictions on the duration and magnitude of the negative values that the renormalized energy density can admit in the context of quantum field theory. They have been proven for several free fields in flat and curved spacetimes. Non-minimally coupled scalar classical fields can violate all the main pointwise energy conditions. In this work, we calculate the constraints obeyed by the null energy of non-minimally coupled scalar fields at classical and quantum levels. We also discuss the theory in both Jordan and Einstein frames.

Speaker: Diego Pardo Santos (King's College London)

YTH23_DPardo.pdf

15:15 General Address: Farewell Address

Jack Franklin