New Horizons in Quantum Field Theory, Particle Physics and String Phenomenology

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Theoretical investigations of the Standard Model have underpinned experimental discoveries and have been instrumental in shaping our current knowledge of the nature of matter and its interactions. At a time when the standard model (SM) has finally been completed by the discovery of the Higgs boson, deep and profound mysteries remain in our understanding of the Universe. The existence of dark matter necessitates new physics beyond the SM, and crucial issues concerning dark energy and the unification of gravity with the other forces remain unaddressed. Meanwhile, the mathematical structures that underlie quantum field theory are far from fully explored; and there are important open questions about the dynamics of matter within the SM, especially in extreme environments.The Theoretical Physics group in Liverpool is contributing to searches for New Physics from three complementary directions. (i) We carry out perturbative calculations within the standard model to an unprecedented precision. This is essential if deviations of observables from their SM predictions, occurring due to new physics, are to be detected in accelerator experiments. Concurrently, we are using our theoretical expertise to explore promising extensions of the Standard Model and to inform the development of experiments that are well placed to discover new physics. (ii) These efforts are complemented by large scale computer based calculations. This non-perturbative approach is essential for unlocking certain inputs for standard model theory predictions, which are beyond the reach of perturbation theory. The current lack of precision in these inputs limits the usefulness of experimental observations. Our simulations are state-of-the-art and are now including electro-magnetic corrections (QED) to the theory of strong interactions QCD. (iii) We determine the fingerprints that Beyond the Standard Model (BSM) physics could produce in experimental data and observations. Such work includes the use of astrophysical and cosmological data, e.g. from dark energy surveys and gravitational waves, and it leads to constraints that complement laboratory based searches. This is accompanied by rigorous studies in string theory. In addition to progressing towards an understanding of quantum gravity, our work in this direction informs and inspires BSM model building.We also explore terra incognita within the Standard Model itself: we will study the phases of strongly interacting matter in particular at finite densities, and we will embark on the study of real-time dynamics in quantum field theory using first principle computer simulations. A key challenge is to understand how quarks and gluons form hadrons, the basic building blocks of matter. The standard explanation for forming hadrons out of a heavy ion collision fireball invokes a local thermal equilibrium, which might or might not be justified. A distinctive alternative to explain observations is a genuine quantum effect called entanglement, which we will endeavour to explore.