I am Professor of Cosmology at the Institute of Cosmology and Gravitation at the University of Portsmouth. My research area is observational cosmology – this means I study the properties of dark energy, dark matter and gravity, using the large-scale structure of the Universe and based on galaxy survey data collected by the leading ground-based and space telescopes.

My background

I grew up in Delhi, India, where I did my undergraduate degree at the University of Delhi. I won a Rhodes Scholarship to the University of Oxford in 2005, where I took an MPhys and then a DPhil in theoretical physics. After short postdoctoral postitions at the University of Bielefeld and the University of Helsinki, I came to Portsmouth as Marie Skłodowska-Curie Fellow and Dennis Sciama fellow in 2015. After winning an Ernest Rutherford Fellowship I briefly left Portsmouth for UCL in 2021, before returning as (proleptic) Senior Lecturer in 2022.

My research

I study the large-scale structure of the Universe, analysing the statistical patterns in the distribution of millions of galaxies to uncover cosmological information. I am particularly known for my work on baryon acoustic oscillations and the development of new methods beyond two-point clustering statistics, such as cosmic voids or density-split statistics. More generally I have worked on a wide range of other areas in cosmology, including redshift-space distortions, clustering of the Lyman-alpha forest and gravitational lensing, as well as theoretical models of dark matter, dark energy and inflation.

A large fraction of my work involves the Dark Energy Spectroscopic Instrument survey, or DESI. DESI is a 8-year spectroscopic survey programme to map the positions of 60 million galaxies and quasars in order to determine the dark energy equation of state, the neutrino mass scale, and a host of other science results. I led the Galaxy and Quasar Clustering working group in DESI from 2022-2025, when we published our major results from the first two data releases.

Another large part of my work is within the Euclid Consortium. Euclid is a space telescope, which combines spectroscopic measurements of around 30 million galaxies with weak lensing and photometric surveys of over a billion. I lead a group at Portsmouth funded by the UK Space Agency that is creating the spectroscopic galaxy catalogues and visibility mask for Euclid clustering science. I also coordinate the Euclid DR1 Key Project on measuring baryon acoustic oscillations.

My research has been funded by the Science and Technology Facilities Council (STFC), the UK Space Agency (UKSA), and the European Commission.

Media and public lectures

I regularly give public talks on cosmology around the south-east within striking distance of Portsmouth. If your society or group is interested in hearing about DESI and dark energy, get in touch via my university email.

A few examples of recent media coverage: BBC, The Guardian, Nature, Quanta, Scientific American. I appeared on The Sky At Night and with Hannah Fry on Hannah Fry’s Mysterious World of Maths, both aired on BBC4.

Miscellaneous

When I was younger and more care-free, I was a keen mountaineer and climber: I have climbed, organised expeditions and recorded occasional first ascents in the Indian Himalaya, the Alps, the Dolomites, the Moroccan Anti-Atlas, and the Pyrenees. These days such adventures are limited to my local gym or occasionally bouldering in Fontainebleau. I have played recreational club cricket at various – mostly low – standards in three different countries (can you guess which three?), and still play most weekends for my local club in Portsmouth.