عبدالعلی بنی هاشمی (دانشکده فیزیک دانشگاه شهید بهشتی)
Abstract: In this talk, first we will take a brief look at some LCDM tensions; then we explain our idea for lessening them by giving a new model for the evolution of the universe. Our idea is based on supposing a phase transition for Dark Energy, where we study this phase transition in the framework of Landau-Ginzburg theory. In the end, we will show that the results of our model are promising and reduce the tensions.
Department of Theoretical Physics of the University of Geneva
Abstract: I’m going to introduce a new instability in partial differential equations, which also can be present in some dark energy and cosmological models. We have studied k-essence scalar field and have developed an N-body code, k-evolution, in which we consider non-linearities. We have proved that the k-essence non-linearities suffer from the new instability and blowup in finite time; I’ll show the solution and blowup time for different initial conditions. Moreover, to understand the new instability, I will solve the traffic flow as a similar dynamical system and show how shock waves are produced in the traffic flow.
Department of Physics and Astronomy at the University of Pennsylvania
Abstract: Nonlinear structure formation is an important area in the modern cosmology, where deep questions can be addressed by large-scale structure data, especially the questions which are related to the dark universe – the physics of dark matter and dark energy. In this arena, the abundance and clustering of dark matter halos probe important features of the standard model of cosmology. The excursion set approach is a framework for estimating how the statistical properties of nonlinear structures in the cosmos depend on the history of the universe and the nature of gravity. In this theory, one associates a random walk with each position in the initial density field, and the barrier to be crossed is determined by the collapse model. The main problem here is the first passage time problem and the first up-crossing distribution is the quantity which is related to the abundance of nonlinear objects. My recent work is about approximations of the first up-crossing distribution (for non-Markovian walks) and modeling the abundance of halos, and in this talk, I would like to show the associated implications for halo bias.
Department of Physics and Astronomy at the University of Pennsylvania
“Gaia is an ambitious mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. This amounts to about 1 per cent of the Galactic stellar population.” From http://sci.esa.int/gaia/
For registration: Send an email to baghram@sharif.edu till Sunday December 30, 2018 with the title GAIA-Workshop.
