Séminaire

Phenomenology and theory of galactic cosmic-ray propagation

Understanding the cosmic-ray (CR) transport in the Milky Way magnetic field is fundamental to unveil their galactic factories. While we know now that they can be created in supernovas, there may be other sources available for CR acceleration. To trace back CR origins we can look at what they are made of. By weighing the different isotopes of elements that hit CR detectors, we can infer global properties as the galactic grammage and escape time.

Simulating gravitational wave production during a vacuum phase transition

In this talk I will discuss cosmological first-order phase transitions. These phase transitions which proceed through the nucleation and merger of bubbles on the new phase are known to source gravitational waves. If one of these events occurred in the early universe then upcoming space based gravitational wave detectors like LISA may be able to detect the resulting gravitational wave background that remains today. In this talk I will focus on transitions in which the bubble wall accelerates until collision.

Webinaire_Annonce de la publication du GWTC-2

Bonjour,

Publication par Virgo et LIGO du catalogue GWTC-2 contenant 39 détections

La classification et l’analyse finale des 39 événements détectés par
Virgo et LIGO lors de la prise de données « O3a » (1er avril – 1er
octobre 2019) ont été publiées le 29 octobre 2020. La plupart des
sources O3a sont des fusions de trous noirs. Une probable fusion d’un
système binaire d’étoiles à neutrons et deux possibles systèmes
« hybrides » – formés d’un trou noir et d’une étoile à neutrons –
figurent également au tableau de chasse de O3a. Si quatre de ces

Evolution of magnetic fields in the early Universe

Magnetic fields are observed on virtually all astrophysical scales of the modern Universe, from planets and stars to galaxies and galaxy clusters. Observations of blazars suggest that even the intergalactic medium is permeated by magnetic fields. Such large-scale fields were most likely generated very shortly after the Big Bang and therefore are a unique window into the physics of the very early Universe.

Euclidean Wormholes and Holography

Wormholes are exotic solutions of General Relativity that still challenge our physical intuition. In this talk I will first review and distinguish various types of wormholes along with their expected physical properties. I will then focus on asymptotically AdS wormhole solutions in the context of holography. I will explain how to compute correlation functions of local operators as well as non local observables such as correlation functions of Wilson loops on the distinct boundaries and discuss their behavior.

The European Low Frequency Survey: observing the radio sky to understand the beginning of the Universe

Nowadays the leading contender to understand the initial conditions of the Big Bang is inflation, which predicts the existence of a primordial background of gravitational waves that must have left its imprint in the CMB polarization: the so-called ​ B-modes. The main difficulty in measuring the ​ B-modes comes not just from its sheer faintness but from the fact that many other objects in the universe also emit polarized microwaves.

Free falling with a pulsar in a triple system 

Universality of free fall, famously depicted by Galileo's letting down various masses from the top of Pisa's tower, is a cornerstone of General Relativity to the extent that any alternative theory of gravity would almost certainly break that principle. This is why it is being tested by ever more sensitive experiments in the Solar system, such as the recent Microscope satellite.
Séminaire