Cosmologie

The Present and Future of CMB Polarization Observations

One of the big goals of today’s CMB experiments is to look for the faint signature of primordial gravitational waves in the B-mode polarization. Finding it would give us a unique window into the physics of the very early Universe and the Inflationary epoch.

Beyond the Limits of Quintessence

Current cosmological data seem to point beyond the limits of quintessence for the behavior of dark energy accelerating the universe. This requires challenging physics such as modified gravity, interactions, or altered vacuum, in analogy with how non-Gaussianity in inflation requires physics beyond standard dynamics. We explore some possibilities.

Prospects for Measurements of Spectral Distortions and Intensity Mapping

The experimental quest to extract the full information content of the anisotropies of the Cosmic Microwave Background (CMB) has lead to a Moore's Law-like evolution in instrument capabilities. In this seminar, I explore adapting the technologies developed for the CMB to two other, more challenging science goals: Spectral Distortions, and Intensity Mapping.   I will discuss these science topics and present concepts for instruments that could make precise measurements of these signals. I present the SPECTER instrument concept.

Probing the nature of dark energy with DESI DR2

DESI is the first new generation galaxy survey to take data with the goal to shed light on the mechanism that drives the acceleration of the cosmic expansion. We postulate the existence of a mysterious component, dark energy, responsible for such acceleration, and we assume, in our current cosmological model, that dark energy takes the form of a cosmological constant Lambda.

Energy flow of λ in Hořava-Lifshitz cosmology

Hořava-Lifshitz gravity is  perturbatively renormalizable quantum gravity model candidate with an anisotropic UV-scaling between space and time. I would like to present a cosmological background analysis of the minimal projectable formulations of the theory, with particular focus on the running of the parameter λ with energy.

Spectroscopic surveys: DESI, DESI-2, Spec-S5

The DESI experiment will put tight constraints on the dark energy with the observation of more than 40 million spectroscopic redshifts, mostly at z < 2. It started its Main Survey in May, 2021, making it the first Stage-IV cosmological experiment to go on-sky. Cosmological analysis of the Y1 data acquisition were made public in Apr. 2024, and the Y3 data acquisition is done. I will present the DESI survey current status, along with the proposed extension of operations. I will then present the DESI-2 and Spec-S5 experiments.

A Big Telescope and a Big Computer: How HPC and AI Will Enable Next Breakthroughs in Our Understanding of the Universe

The upcoming mega-telescopes, such as European Space Agency’s recently launched Euclid satellite, and the upcoming radio Square Kilometer Array (SKA), will provide images of our universe over 10 billion years of cosmic history, and enable us to study its evolution with unprecedented level of detail. In the framework of simulations-based inference, the big telescopes deliver a throve of high-resolution observations and big computers provide the feature-rich numerical theory prediction.

Confronting the Cosmological Principle: How secure are the foundations of the cosmos?

I will present our recent work using quasars and radio galaxies to confront the cosmological principle, the idea that sits at the heart of modern cosmological theories. Whilst the cosmological principle states that the universe is isotropic and homogeneous, our observations of the Cosmic Microwave Background (CMB) reveal a pronounced dipole, interpreted as our kinematic departure from the local Hubble flow.
Cosmologie