Conveners
Afternoon 2
- Ariel Goobar
Afternoon 2
- Eleonora Di Valentino (University of Sheffield)
Afternoon 2
- There are no conveners in this block
Strong gravitational lensing is a powerful tool for mapping the distribution of dark matter and testing various cosmological parameters. One such parameter is the Hubble Constant, which can be determined by measuring the time delay between lensed images. Our study focuses on the detection of lensed quasars by forthcoming Nancy Grace Roman Space Telescope (Roman) survey. Based on the capability...
I will review the essence of the Hubble tension, its current observational status and the three classes of theoretical models that attempt to address it. Then I will focus on the level of the tension in redshift bins as expressed by the mismatch between distances measured by BAO data and by SnIa data calibrated respectively by the CMB sound horizon scale and by the Cepheid based distance...
Cosmic shear, the weak gravitational lensing effect on distant galaxies due to matter in the foreground, is a powerful tool to study the distribution of matter, to probe its large-scale structure, and infer the cosmological model of the Universe. Standard analyses are typically based on the assumption of a Gaussian likelihood with a parameter-independent covariance, but these assumptions may...
We present recent advances in combining Nested Sampling and Simulation Based Inference, and show these are performant for cosmological scale problems. Nested sampling [1,2] is a numerical Bayesian inference tool for performing model comparison and parameter estimation, and has been widely applied across cosmology & particle physics. Simulation based inference (SBI) is an emerging new paradigm...
In this talk I will develop a method to constrain the Cosmological Constant Λ from binary galaxies, focusing on the Milky Way and Andromeda. I will provide an analytical solution to the two-body problem with Λ and show that the ratio between the Keplerian period and TΛ = 2π/(c √ Λ) ≈ 63.2 Gyr controls the importance of effects from the Cosmological Constant. The Andromeda-Milky Way orbit has a...
Early data from the James Webb Space Telescope (JWST) has uncovered the
existence of a surprisingly abundant population of very massive galaxies at extremely high redshift, which are hard to accommodate within the standard ΛCDM cosmology. We explore whether the JWST observations may be pointing towards more complex dynamics in the dark energy (DE) sector. Motivated by the ubiquity of anti-de...
Despite decades of research, cosmology still lacks reliable probes to study the Universe in the intermediate redshift regime (from z = 1 up to z = 1100). Very few astronomical objects observed at such high distances can be standardized. We present the case of two such sources: Gamma-Ray Bursts (GRBs, $z<9.4$) and Quasars (QSOs, $z<7.4$). For GRBs, the observational luminosity distance can be...
In this talk, we present a novel approach to accelerate the Bayesian inference process, focusing specifically on the nested sampling algorithms. Our method utilizes the power of deep learning, employing feedforward neural networks to approximate the likelihood function dynamically during the Bayesian inference process. Unlike traditional approaches, our method trains neural networks on-the-fly...
