Date: April 17 2024
Venue: Room 1403 Pab. 0 DF-UBA & zoom (plase fill this form to get the link: https://forms.gle/6Dwth5UaGSywwMf58)
PROGRAM
10:00h: Tomás Ferreira Chase (DF-UBA)
Title: Ultralight vector dark matter, anisotropies and cosmological adiabatic modes
Abstract:
Ultralight dark matter models have received a lot of attention in the past years due to its correct predictions of cosmological observables at large scales, and its differences with respect to LCDM at small scales. In this talk we present an ultralight vector field dark matter model and its corresponding implementation in CLASS. Vector field models break the isotropy assumption at large scales. In particular, we show that in order for the model to be consistent at early times, it is necessary to generalize the FRW metric to a Bianchi I geometry to correctly describe the anisotropies. Finally, we show the matter power spectrum of the theory and analyse the main differences with respect to LCDM and scalar models.
11:00h: café
11:30h: Anibal Varela (UNSMAM)
Title: Assessing the combination of Vera Rubin and Nancy Grace Roman observatories for enhanced characterization of microlensing events
Abstract: The gravitational lensing of stars by condensed objects, such as other stars, black holes, planets, or dark matter candidates produces a time dependent magnification effect known as microlensing and can be detected in time-domain observations.
The Nancy Grace Roman Space Telescope is scheduled to begin its science operations in approximately 2027. It will undertake two main surveys, one of which focuses on exoplanet exploration. By utilizing microlensing, Roman is expected to make significant discoveries of planets (including "free floating" ones) and, possibly, low-mass primordial black holes, due to its high cadence.
In parallel, the Vera Rubin Observatory is scheduled to have its first light in the current year. It holds the distinction of being the first super-telescope with a large field of view (9.9 square degrees). Its observing strategy is unique, as it covers nearly the entire visible sky within a single night. Rubin LSST will allow microlensing to be discovered throughout the celestial sphere, providing a census of the distribution of compact objects in the galaxy, particularly non-visible ones, such as planets and black holes. In particular, this would allow us to check if these objects are consistent with stellar and planetary evolution or if they could be a component of dark matter, for example, in the form of primordial black holes.
The objective of this work is to evaluate the potential enhancement in the discovery rate when data from both the Roman and Rubin telescopes are combined. To achieve this, we conduct detailed simulations of microlensing events as if they were measured by these observatories. Through the estimation of the uncertainties in the parameters of the model, we quantify the improvements in terms of the ability to characterize and detect these systems. This assessment aims to provide valuable insights into the synergy and complementarity of data obtained from Roman and Rubin, thereby advancing our understanding of systems detectable through the microlensing technique.
12:30h: Almuerzo
14:00h: Arttu Rajantie (Imperial College London)
Title: Stochastic effective theory for scalar fields in de Sitter spacetime
Abstract: The dynamics of the Higgs and other light scalar fields during inflation can have important cosmological consequences, but because of the infrared problem, they cannot be computed using perturbation theory. A powerful alternative is the stochastic Starobinsky-Yokoyama approach, which is based on the observation that on superhorizon distances the field behaves classically, with a noise term produced by subhorizon quantum modes. It has been mostly used to calculate the one-point probability distribution of the field, but its real power lies in describing the asymptotic long-distance behaviour of correlation functions through a spectral expansion. I demonstrate this by calculating isocurvature constraints for scalar dark matter models and decay rates of metastable vacua. I also show how to extend the stochastic theory beyond the overdamped approximation used by Starobinsky and Yokoyama. The parameters of this effective theory are determined at one-loop order in perturbation theory, and do not suffer from the same infrared problems as a direct perturbative computation of observables. Therefore it provides a powerful and accurate way of computing cosmological observables.
15:00h: café
15:30h: Federico Ravanedo (UNSMAM)
Title: Search for Dark Matter in LIGO
Abstract: The extreme sensitivity of LIGO's detectors in detecting changes in the length of its arms makes both detectors in conjunction a perfect instrument to measure Gravitational Waves. Moreover, it is such a sensitive instrument that it can also be activated by tiny signals such as trucks driving on nearby roads, farmers plowing fields, and even local winds, among others. However, in these latter cases, the activation occurs in only one of the LIGO detectors, which can discard a gravitational wave signal. Furthermore, in many cases, one of the LIGO detectors registers a signal, and there is not yet a conclusive understanding of what produced it. These are usually referred to as glitches in the LIGO jargon. We are studying whether these glitches could be produced by the passage of a Dark Matter (DM) clumps through one of the LIGO detectors. In this talk, we present the recent results of this study, preceded by a brief introduction to the motivations and the mathematical and physical concepts that allow us to carry out this study.