Research

I am a data-driven astrophysicist and cosmologist, interested in bridging the gap between theory and data. As such, I work at the interface between the two, developing novel theoretical and statistical techniques to test our physical theories. I have explored topics spanning the formation of structures in the Universe, the first stars and galaxies, the late-time acceleration due to Dark Energy, the nature of Dark Matter, and the very early Universe. My most important contributions have been finding innovative ways to test physical theories using astrophysical observations. Other recent examples include an analysis of the Covid-19 pandemic and the spectral properties of non-stationary random signals. You can check out my publication list for a more complete list of topics I work on.

I also play a leading role in some of the most promising current and future cosmological surveys, outlined below.

Topics:

The CMB as a "backlight": cross-correlations with Large-Scale Structure

My group pioneered the use of the cosmic microwave background as a backlight to map the distribution of gas and dark matter in and around galaxies, groups, and clusters. By combining CMB lensing, thermal and kinetic SZ measurements, and large-scale structure data, my work uncovers the physical processes that shape galaxy evolution and provides new, model-independent constraints on cosmology. We also use complementary probes such as X-rays or Fast Radio Bursts (FRBs).

Making the largest 3D map of the Universe

DESI is creating the largest 3D map of the Universe, measuring tens of millions of galaxy spectra to study cosmic acceleration and the growth of structure with unprecedented precision. My group combines DESI’s galaxy maps with CMB lensing and SZ data to map dark matter and baryons, achieving some of the strongest current constraints on structure growth, dark energy, and gravity on cosmological scales.

The early Universe

My research develops cutting‑edge methods to detect primordial gravitational waves in the CMB and rigorously model potential contaminants. I also designed novel probes of axion-string networks, including cosmic birefringence, and pioneered techniques to search for primordial non‑Gaussianity in large-scale structure, advancing our ability to test inflation and high-energy physics in the early Universe.

CMB and galaxy weak gravitational lensing

A central focus of my work is transforming CMB and galaxy weak lensing into precision tools for cosmology. By developing advanced reconstruction techniques and by cross‑correlating CMB and galaxy lensing maps to calibrate systematic biases, I enable robust measurements of structure growth, dark energy, neutrino mass, and tests of gravity on cosmological scales.

Next-generation of galaxy and intensity mapping surveys

I have led the work motivating the science goals of next-generation galaxy and intensity mapping surveys, including DESI‑II, Spec-S5, and line intensity mapping, which aim to map vast high-redshift volumes and access an unprecedented number of modes. These surveys will enable transformative studies of the early universe, dark energy, primordial non-Gaussianity, and light relics, while complementing CMB and imaging datasets.

The Epoch of Reionization

I developed novel methods to isolate the subtle imprints of patchy reionization in the CMB, enabling us to disentangle the effects of early ionizing sources from other signals. This provides a clearer view of the timing, duration, and structure of reionization and has become a key tool for major CMB collaborations, helping to reveal how the first stars and galaxies shaped the evolution of the cosmos.

Experiments:

DESI

The Dark Energy Spectroscopic Instrument (DESI) is mapping tens of millions of galaxies and quasars across more than a third of the sky, creating an unprecedented 3D view of the Universe to study dark energy, the growth of cosmic structure, and galaxy evolution.

Within DESI, I chaired one of the largest science working groups with over 50 active projects and over 100 members, and I was a member of the main science governing board. I was responsible for coordinating the work on small-scale clustering, clustering beyond the power spectrum, clusters and cross-correlations. As part of that effort, I led the negotiations and coordination of the MoU between ACT and DESI. My current research focuses on combining DESI spectroscopy with CMB data to probe structure growth, baryons, and velocities, unlocking powerful synergies between galaxy surveys and CMB experiments.

Simons Observatory and Atacama Cosmology Telescope

The Simons Observatory (SO) is a cutting-edge cosmic microwave background experiment in Chile that uses a powerful combination of large- and small-aperture telescopes to produce ultra-precise maps of the early Universe, probing 13 billion years of cosmic history—from the first moments after the Big Bang through the formation of the first stars and galaxies to the physics of the present-day cosmos.

My group's work in SO focuses on secondary anisotropies, primarily CMB lensing and SZ, as well as searches for new Physics with CMB temperature and polarization. I led the SZ and reionization science working group, and I was the pipeline lead for the lensing cross-correlations analysis working group. I am also an active member of the Atacama Cosmology Telescope (ACT).

Rubin Observatory and LSST DESC

The Rubin Observatory’s Legacy Survey of Space and Time (LSST) will deliver one of the deepest, widest optical imaging surveys ever undertaken, mapping billions of galaxies over a decade to trace the growth of structure, dark energy, and transient phenomena with unprecedented precision.

My group focuses on leveraging LSST’s imaging in combination with complementary spectroscopic and CMB datasets, exploiting synergies that maximize scientific return. We work on jointly analyzing LSST galaxies with spectroscopic samples (e.g., DESI and future surveys) and with CMB lensing maps to improve constraints on structure growth and dark energy, while simultaneously developing methods to control key systematics such as photometric-redshift calibration, shear biases, and contamination.

DESI-II and Stage-5 spectroscopy

The proposed "spectroscopic roadmap" for the next generation of spectroscopic surveys starts with DESI-II, which will pilot observations of galaxies both at much higher densities and extending to higher redshifts. A Stage-5 experiment (Spec-S5) would build out those high-density and high-redshift observations, mapping hundreds of millions of stars and galaxies in three dimensions, to address the problems of inflation, dark energy, light relativistic species, and dark matter. These spectroscopic data will also complement the next generation of weak lensing, line intensity mapping, and CMB experiments and allow them to reach their full potential.

My group led the forecasting and optimization work that shaped the roadmap. You can read a summary of the science reach here, along with detailed forecasts here. We are now committed to helping realize this vision and to ensuring that these surveys deliver maximal scientific return, including strong synergies with imaging data, CMB experiments, and other cosmological probes.

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