REVEALING THE STRUCTURE OF THE UNIVERSE: GRAVITATIONAL WAVES, COSMOLOGY AND EXOPLANETS

This is an ambitious proposal to advance our understanding of the structures in our Universe, exploiting the latest STFC observational programmes in gravitational waves, the cosmic microwave background, galaxy surveys and exoplanets. Our main goals are:

1. We will investigate the statistics of matter in the Universe using the latest galaxy survey data (the Dark Energy Survey), as well as maps of the cosmic microwave background, the relic radiation left over from the Big Bang. Determining whether these statistics are Gaussian (obey the normal distribution), we will be able to better understand gravitational collapse and to look for primordial signals from the early Universe, testing theories for the origin of galaxies.

2. In this project, we will develop new approaches to the study of CMB lensing, the gravitational deflection of relic light from the Big Bang, and apply them to the state-of-the-art Simons Observatory experiment. With our novel methods for extracting and inverting the lensing deflection, we will provide a clearer view of the beginning of the universe and the distribution of dark matter.

3. The spatial distribution of everything on cosmological distances, from atoms to light, from energy to spacetime itself was set up in the first fraction of a second after the big bang, in an era called inflation. By studying models of inflation, we will predict specific patterns of regularity in this apparently haphazard distribution and search for evidence of this signal in the Cosmic Microwave Background.

4. One of the most spectacular discoveries from astrophysics and cosmology is that most of the Universe's matter content is dark, i.e. invisible in electromagnetic observations. The 2017 Nobel-Prize winning detection of gravitational waves now provides us with a new channel to search for the enigmatic dark matter. For this purpose we will compute how dark matter environments manifest themselves in the gravitational wave signal from black hole binaries.

5. The recent direct detection of gravitational waves emitted in black hole mergers provides an unprecedented opportunity to test Einstein's General Relativity (GR) for strong gravitational fields. To do this we need theoretical predictions for how a deviation from GR would affect the gravitational waves emitted in a black hole merger. We will develop the mathematics needed to perform supercomputer simulations of black hole mergers in a very broad class of theories. It will use these to identify how the predictions of such theories differ from those of GR in the strong gravity regime.

6. Discoveries of the gravitational wave sources by LIGO/Virgo observatory necessitate the need to understand the origin of the objects that produce them - binary black holes and neutron stars. This project takes a fresh look at the dynamical evolution of such relativistic binaries in dense stellar clusters to understand their contribution to LIGO/Virgo discoveries.

7. We will study the breaking of tidal waves in stars caused by close exoplanets, to understand the rates at which their orbits are shrinking. We will also provide the scientific community with efficient codes to compute tidal dissipation in rotating and evolving stars and giant planets, so that the origins and orbital evolution of many observed exoplanet systems can be understood.

8. Planets are born in the disks of gas and dust encircling very young stars. These disks are both turbulent and magnetised; we will seek, via computer simulations, how these two processes influence the formation of planets, and the evolution of the disks that bear them.

9. We have embarked on a joint outreach venture with the Discovery Channel to reach a very large international audience through the launch of a new multimedia Video on Demand service. It will use content we supply from our gravitation and cosmology research projects, on which we will also base our talks and websites for the public and schools.

Our group has a long record of accomplishment in astrophysics, cosmology and gravitation, and of disseminating the fruits of our research to the public. The global coverage of Stephen Hawking's passing was a reminder of the enormous impact he has had in making physics and cosmology accessible and exciting to the public through his books, television series, lectures and media appearances. The live-streamed video of the 2017 Public Symposium we organised to mark his 75th birthday has received over five million views (speakers included Brian Cox, Gabriela Gonzalez (chief LIGO spokesperson), Lord Rees and Stephen Hawking). He raised the profile of STFC's cosmology programme in ways that continue to resonate through many media.

Our research conferences have always included a major public outreach programme of talks with high-profile speakers, and this will continue with public talks closely tied to the research projects in gravitational waves, modified gravity, black holes, inflation, the microwave background and galaxy surveys. For example, our upcoming COST Gravitational Waves Summer School will benefit young researchers in this cutting-edge branch of observational astronomy, and will feature an evening of talks about the implications for the GWs discovery which will be open to the public and live-streamed. The group holds an annual high profile public outreach lecture, entitled the Andrew Chamblin lecture, with speakers in recent years including Kip Thorne, Gerard t'Hooft, Frank Wilczek, Michel Mayor, Sir Roger Penrose and Jim Al-Khalili.

Our group faculty and other members give regular talks to non-university audiences that increase the impact of the research conducted on the grant, including the encouraging of girls to study physics and mathematical sciences. We also have a strong presence at the annual Cambridge Science Festival, holding talks and demonstrations, and at the regular DAMTP open days (attended by over 800).

A major new venture is a collaboration with the Discovery Channel with their new Video on Demand service and then for a new app. Science Surrounds Us, which will feature multimedia and articles by our researchers, which will create massive public reach and enduring impact for our STFC research projects. The content we create will appear on Facebook, YouTube and other social media websites, and we will extend the impact on our own group webpages, using this material for talks and interactions with the public.

The new STFC Centre for Doctoral Training in Data Intensive Science in Cambridge continues to develop many industrial partnerships through internships and studentships, developed and overseen by our faculty member James Fergusson.

As host of the award-winning COSMOS Intel Parallel Computing Centre (IPCC), we will continue to have a significant economic and technical impact on high performance computing (HPC). It is through this that we offer broader support to researchers outside Cambridge (e.g. supporting the public release of the powerful new GRChombo numerical relativity code) and also HPC and research programming courses for doctoral students. The COSMOS IPCC will continue its industrial collaboration with the world-leading HPC vendors Intel and HPE. In this, we build on a record of high impact, which includes public demonstrations at most of the recent major international HPC conferences (Supercomputing '15, 16, 18 and ISC '15, 16, 18). We will continue to engage proactively with our industrial project partners as we explore emerging technologies, presenting our results in industry-wide HPC conferences, articles and white papers.