Postdoctoral Fellow · TIFR, Mumbai

Sukhdeep Singh Gill

I study the large-scale structure of the Universe, using galaxies and the 21-cm signal of neutral hydrogen to learn how cosmic structure grew.

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An illustration of the cosmic web: galaxies trace filaments, knots and voids.

About

Cosmology explores the ultimate story of the Universe: its origins, its composition, and its eventual fate.

I work on these questions as a theoretical and computational cosmologist, in a field where physics and mathematics are closely woven together. I am a postdoctoral fellow in the Department of Theoretical Physics at the Tata Institute of Fundamental Research (TIFR) in Mumbai.

My research focuses on the large-scale structure of the Universe: the vast cosmic web of galaxies and gas. I study the higher-order correlations in this structure through galaxy clustering and fluctuations in the 21-cm signal from neutral hydrogen (HI). Alongside this, I develop cosmological simulations and constrain key parameters governing both cosmic expansion and galaxy formation.

I earned my PhD at IIT Kharagpur under the supervision of Prof. Somnath Bharadwaj, where I used observational data and simulations to analyze the bispectrum (a three-point statistic) of galaxy and HI distributions. I am also a member of the SKA-India consortium on 21-cm cosmology, investigating Cosmic Dawn, the Epoch of Reionization, and the post-reionization era.

Research at a glance

Six threads, one cosmic web

Read about my research

Power spectrum & bispectrumThe two- and three-point statistics of large-scale structure. Galaxy clusteringWhat the 3D distribution of galaxies tells us about cosmology. 21-cm cosmologyRadio observations of neutral hydrogen across cosmic time. ReionizationThe Epoch of Reionization and the era that followed it. Dark energyThe accelerating expansion of the Universe. Constraining CosmologyPinning down cosmological parameters from survey data.

Now

What I am working on

Late-time Universe

Galaxies as a 3D map

Galaxy surveys provide a rich, three-dimensional map of the cosmos. I build statistical tools to unlock this data—even on small, non-linear scales—to trace how the late-time Universe evolved.

Epoch of Reionization

Hydrogen and the first light

The 21-cm line of neutral hydrogen offers a direct window into the Epoch of Reionization. By mapping the radio sky with interferometers, we can decode the physics hidden in 21-cm fluctuations. Currently, I am using 21-cm forest data to tightly constrain reionization models.

Open source

Public tools for higher-order statistics

See all code

Galaxy surveysBARBIERedshift-space bispectrum multipoles from 3D galaxy fields. 21-cm cosmologyViBERThe angular bispectrum from single-frequency radio visibilities. 21-cm cosmologyAMBERMulti-frequency angular and 3D bispectra from radio visibilities.

Latest publications

All publications

2026The Epoch of Reionization 21 cm bispectrum at z = 8.2 from MWA data. II. Smooth component filteringGill, Elahi, Bharadwaj, Sethi & Patwa · The Astrophysical Journal 1003, 189
2025Probing gravity beyond general relativity with bispectrum multipoles of cosmological tracers. I. Theoretical foundationsGill · Publications of the Astronomical Society of Australia 42, e116
2025The Epoch of Reionization 21 cm bispectrum at z = 8.2 from MWA data. I. Foregrounds and preliminary upper limitsGill, Bharadwaj, Elahi, Sethi & Patwa · The Astrophysical Journal 993, 56

“I think nature’s imagination is so much greater than man’s, she’s never going to let us relax.”

Richard P. Feynman