The Universe in Light of Fundamental Physics

Particle physics and cosmology are merging. In recent years, the cross-pollination of ideas between the fields has accelerated, fueled by the availability of a wealth of new raw astrophysical data and increased realization of the intimate theoretical connection between particle physics and cosmology. Now that the LHC is online, particle physics is returning the favour with high-quality data on the building-blocks of cosmology. With the coming release of data from the PLANCK satellite and many balloon experiments, the Advanced LIGO gravitational-wave detectors, the AMS-02 space-based particle detector, the Dark Energy Survey (DES), and many other experiments searching for dark matter, this cross-pollination of ideas and data is destined to continue.

The scientific programme proposed here by the Theoretical Particle Physics and Cosmology (TPPC) Group in the Physics Department of King's College London is focused on the the analysis and interpretation of data from observational cosmology and high-energy astrophysics using insights from fundamental physics.

Although the LHC now makes possible direct studies in the laboratory of fundamental physics processes at unprecedented energies, these are eclipsed by the energies attained in the Very Early Universe and in the ultra-high-energy cosmic rays that may be produced by Active Galactic Nuclei (AGNs), gamma-ray bursters (GRBs), supernovae, black holes and pulsars. The cosmic microwave background (CMB) and violent astrophysical events therefore provide unique laboratories for studying new fundamental physics. However, while searching for observational signatures of new physics, one must model known physics accurately, taking into account the information provided by the LHC and other accelerators. For example, the wealth of new data on the CMB and large-scale structure (LSS) necessitates the development of new analysis tools to probe and interpret possible signatures of new physics such as primordial non-Gaussianities and small neutrino masses, so as to distinguish them from more conventional phenomena. Likewise, searches for dark matter require accurate modelling of dark matter halos in order to calculate reliably density and velocity distributions as well as to probe for deviations from the usual weakly-interacting dark matter paradigm, such as self-interactions. Moreover, high-energy emissions from astrophysical sources provide unique opportunities to search for new physics that complement particle colliders and could yield striking observational signatures.

These projects will enable the King's Theoretical Particle Physics and Cosmology Group to have significant global impact at the interfaces between early-Universe cosmology, high-energy astrophysics and fundamental physics.

1) Predictions and Observations of Non-Linear Physics in the Early Universe: We will develop new methodologies and observables to probe the Early Universe, enlarging the theoretical and observational window into theories of the Early Universe. We will build a full general relativistic numerical code with adaptive mesh refinement that is applicable to cosmological problems -- a code we intend to make publicly available. We will test and confirm (or disprove) several conjectures of strong gravity physics in cosmology such as the formation of black holes in cosmological collisions, and the stability of Black Rings.

2) Astrophysical Modelling of Dark Matter: We will obtain a greater understanding of the distribution of dark matter in galaxies. We will create new methods of analysing data based on higher moments of the Jeans equation, enabling us to constrain further the dark matter parameter space and provide an additional astrophysical window into the nature of dark matter, be it cold, warm, self-annihilating or
self-interacting. We will measure the expansion history of the Universe with high-energy gamma rays and place independent constraints upon the equation of state of dark energy (or equivalently the nature of modified gravity). We will test fundamental physics by looking for the observational effects of axion-like dark matter candidates.

3) Signatures of Fundamental Symmetries in Astrophysics: We will obtain new and better contraints on the amplitude and type of Lorentz Symmetry violations. We will obtain the strongest possible astrophysical constraints on the principle of equivalence with time-varying sources of high-energy particles. We will develop new modeling techniques of energy astrophysical sources, and test fundamental symmetries using data from Fermi, HESS II and CTA.

These projects will have significant impact on several academic communities: observers seeking to characterize phenomena in the early Universe, astrophysicists seeking to characterize dark matter, general relativists seeking a new generation of numerical tools, and particle physicists developing theories beyond the Standard Model.