Cosmology News & Events

Abstract: I will present the influence of the chiral anomaly on the evolution of magnetohydrodynamics. In the early universe, before electroweak symmetry breaking, and in systems at high enough temperatures such that the electron mass can be ignored, the general description of a charged plasma needs to take into account the triangle anomaly. The interplay between turbulence and chiral magnetic effect can have important consequences on the evolution of magnetic fields, leading to the creation of maximally-helical fields from initially non-helical ones. Chiral effects can support a turbulent inverse cascade, causing a slower decrease of magnetic field with time and a faster growth of correlation length, when compared to the evolution predicted by the standard magnetohydrodynamical description. Using the weak anomaly approximation, specific solutions for the inverse cascade regime that show how chiral effects support it are derived.

Abstract: We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10^−6–10^−4 eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall–Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane.

Abstract: In this talk, I will first discuss the challenges one faces when trying to explain the observed late-time acceleration of our Universe, due to the obstacles which the yet unkown physics of dark energy and dark matter place when we try to understand the true theory of gravity at large scales. In this context, I will further explain how model-independent observables have the potential to reveal whether gravity is truly modified at large scales, and will describe a fundamental, underlying relation between large-scale modifications of gravity and the (non-trivial) propagation of gravitational waves, as well as its observational implications for cosmology and astrophysics.

Abstract: Inflationary cosmology is the most successful explanation of the large scale features of our universe, such as the uniform tempertaure distribution of the Cosmic microwave background radiation (CMB) and the near flat global geometry of the universe. Satellite based measurements of the CMB in the past 2 decades by COBE, WMAP, and Planck have shown the predictions of inflation to be consistent with data. The most recent of these, the Planck Satellite, has provided the most precise measurement of the CMB ever and offers the best possibility to learn details about the dynamics during the early universe. I will first explain what sort of information can be obtained from measuring the CMB for understanding large scale structure and then review the results of measurement of the CMB made by these satellite experiments. Included in this discussion will be a summary on polarization and non-gaussianity measurements. I will then discuss the two dynamical descriptions of inflation, warm and cold, and present various models in both cases and their predictions for the CMB. I will then discuss how well CMB data has been able to discriminate between the different inflation models.