This talk will discuss scenarios where the gauge/gravity duality can be applied to non-perturbative regimes in physics. The standard model explains many phenomena seen in nature but relies on techniques that only work in small coupling. The gauge/gravity duality is a way in which we can try to obtain theoretical predictions for areas such as strongly coupled condensed matter and the low energy...
I will present a study of the KSVZ axion model with quasi-degenerate vacua as a minimal model for dark energy and dark matter. I will review axions as dark matter and provide an explanation for dark energy in the form of a difference in vacuum energy density between the electroweak vacuum and a second degenerate minimum in the effective potential, which can be achieved via the scalar threshold effect.
Through a web of string dualities, M5-brane configurations in M-theory can be mapped to geometrical features. In particular, I will discuss this map via heterotic/F-theory duality, using a Horava-Witten description of heterotic $\mathrm{E}_8 \times \mathrm{E}_8$ string theory as the connection to M-theory. Intersecting or coincident M5-branes are mapped to singular base geometries in F-theory,...
An increasingly attractive alternative to the WIMP model is that of an `isolated' dark sector - i.e. one which interacts with the standard model only via gravity and which therefore is unbounded by direct detection. We present a possible production mechanism for this sector in the early Universe (Hawking emission from primordial black holes) as well as predictions for the subsequent evolution...
M-theory is a candidate for a theory of quantum gravity. Its fundamental objects are called M2-branes and M5-branes. The low-energy theory describing coincident M5-branes is poorly understood in many respects, with holography providing one of the most useful tools to further that understanding. It is known that the theory should possess solitonic solutions called "self-dual strings". I will...
The Hot Big Bang model of cosmology requires very finely-tuned initial conditions in order to explain the degree of flatness and homogeneity we observe in the Universe today. This has led the community to embrace the theory of inflation, since it readily explains these features. But are the initial conditions required to initiate inflation more or less finely-tuned than those required by the...
In the new era of gravitational-wave astronomy, one of the most exciting targets for future observations is the stochastic gravitational-wave background (SGWB). While we have yet to detect the SGWB, we expect that by studying the angular power spectrum of its anisotropies, we may learn about the large-scale structure of the Universe (analogous to studies of the CMB). With this in mind, we...
The AdS/CFT correspondence links type IIB string theory on $AdS_5 \times S^5$ to $\mathcal{N}=4$ super Yang-Mills with gauge group $U(N)$. In 1998, Witten showed that taking an orientifold quotient of the $S^5$ factor - identifying anti-podal points so as to replace $S^5$ with $\mathbb{RP}^5$ - can be understood on the gauge theory side by replacing the $U(N)$ gauge group with either $SO(N)$...
The aim of the talk is to present the construction of a new family of smooth horizonless solutions of supergravity that have the same charges as the supersymmetric D1-D5-P black hole. We will begin with a brief review of the Fuzzball proposal for black holes, which states that at the length scale of the horizon a new, fuzzy, phase takes over, allowing outside observers to distinguish between...
Interacting fixed points in three dimensions have been investigated using modern renormalisation group methods. Investigations focus on the seminal Wilson-Fisher fixed point solution in O(N) symmetric scalar theories and asymptotically safe UV fixed points in fermionic Gross-Neveu models. The main novelty of the study is the use of Padé approximants. Padé approximants have been used to extend...
M-Theory has been conjectured as a single theory in which we can find each of the various superstring theories, and as such provides a UV completion of 11d supergravity. Instead of strings, we have M2-branes and M5-branes. The classic Horava-Witten result says that a compactification of M-theory on $S^1/\mathbb{Z}_2$ retrieves the $E_8\times E_8$ heterotic theory, with the wrapped M2-brane as...
The renormalization group properties of a QFT are of profound importance to the theory. In quantum gravity, one runs into the problem that the kinetic term for the dilaton (or conformal mode) has the wrong sign, causing the Euclidean partition function to be (worse than usually) ill-defined. Imposing a new quantization condition allows us to not only make sense of this, but also potentially...
For closed universes, the Einstein equations (EE) are linearisation unstable. Perturbing around any background with Killing symmetries the linearised EE admit solutions which are not themselves linearisations of solutions to the non-linear EE. To control these spurious solutions, quadratic linearisation stability conditions are imposed. However, in the quantum theory these stability conditions...
It is long established that the Standard Model is not a complete theory of nature and at the LHC we hope to see hints of some new physics beyond our current understanding. This project seeks to improve current techniques of jet clustering, in particular from some extended BSM Higgs sector, such as those in 2 Higgs Doublet Models, which include additional particles alongside the 125 GeV SM...
Knots are deceivingly simple mathematical objects. Showing whether two knots are the same or not is a hard problem. While it can be done easily by inspection for simple knots, the problem becomes hard very quickly. Ideally, to distinguish between inequivalent knots we have to define knot invariants. At first sight, this may not have anything to do with quantum computation or field theories....
Localization is a powerful technique utilised in supersymmetric field theories to reduce troublesome infinite dimensional path integrals to pleasant finite dimensional integrals. The aim of this talk is to provide an introduction to this topic and discuss its applications. In particular, I will explain how this technique is used to compute the exact partition function and the expectation...
I am working with Professor Stefano Moretti and Doctor Andrew Akeroyd on charged Higgs phenomenology in the University of Southampton recently. We posted the paper in October 2018 on arXiv:1810.05403.
The possibility of a light charged Higgs boson H± that decays predominantly to quarks (cs and/or cb) and with a mass in the range 80 GeV ≤ mH± ≤ 90 GeV is studied in the context of Three-...
Recently it has been pointed out that associated production of dark matter with single top quark could also provide an interesting reach for dark matter (DM) searches at LHC. I will discuss this in context of simplified dark matter models and in two Higgs doublet model. The top quark produced via this channel is polarized and the polarization depends on the CP of the mediator (simplified dark...
Divergent perturbation series are prevalent in all of physics. Notable examples include sums of Feynman diagrams in QFT and sums over Riemann surfaces in string scattering. I will first give a brief introduction to Resurgence theory, starting with ways of summing divergent series which will lead us to Borel summation and then looking at the analytic continuation of the path integrals which...
We study flavour-violation in a SU(5) setup inspired by flavoured GUTs. We investigate the impact of various observables at low scales on the high-energy parameters of the theory including mu->e gamma and the relic density of dark matter. An interesting interplay between the quark and lepton sectors becomes apparent due to the cohabitation of various fields in representations of the unifying...
Modern amplitudes techniques offer the tantalising possibility of greatly simplifying theoretical predictions for precision gravitational wave astronomy. One exciting example is the double copy, an enigmatically simple connection between Yang-Mills theory and gravity. In this talk I will discuss our recent work on rigorously obtaining classical scattering observables from quantum amplitudes,...
I will present some recent results of higher order QCD calculations in vector boson processes at colliders using the Monte Carlo framework NNLOJET. Recent developments are opening up a new world of precision phenomenology for study, improving our understanding of QCD/EW interactions at a fundamental level.
Perturbative QCD suffers from multitudes of large logarithms, arising from the miscancellation of infra-red poles. These logarithms can cause enhancements of high order terms and spoil perturbative convergence. Historically there has been two disjoint approaches to solving this problem; resummations and parton showers. Nowadays resummations are performed at high accuracy and are rigorously...
In semiclassical gravity, the expectation value of the stress-energy operator $\left\langle T_{\mu\nu}\right\rangle$ is an infinite quantity. To avoid having to renormalize it, one can calculate the difference in $\left\langle T_{\mu\nu}\right\rangle$ between a pair of quantum states in such a manner that the divergent parts cancel. However, another technique explored more recently is to...
The discovery in 2012 of the Higgs boson provided evidence for our understanding of the origin of mass. However there still remain some unanswered questions one of which is the "Naturalness Problem".
Like the other fundamental particles, the Higgs acquires loop corrections to its mass due to its interaction with the quarks, the leptons and itself. If we impose an ultraviolet cutoff,...
Anti-de Sitter spacetime is a solution of Einstein’s equations with a negative cosmological constant. This fact allows for unusual black hole solutions with non-spherical horizon topology. We calculate the renormalised vacuum polarisation for black holes with spherical, flat and hyperbolic event horizons, following the “extended coordinates” method, which uses a mode-sum representation for the...
Lattice QFT is a method for calculating non-perturbative physics and has been used extensively to calculate properties of low energy QCD. Over the last decade calculation's of a number of non-perturbative QCD quantities have reached a good precision, with agreement from across the lattice community.
In general isospin breaking (IB) effects have not been included in these calculations because...
In this brief talk I discuss two aspects of a novel approach to quantum gravity, the first of these is the construction of evanescent operators of the dilaton which provides an initial direction to finding solutions to the inherent problems of non-renormalizability of quantum gravity. The second is the use of the Batalin-Vilkovisky anti-field technique and how this can be used with...
