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- 30.10.2020, Angelo Ricciardione (INFN Padua): Characterization of Cosmological Gravitational Waves with the LISA Detector
Abstract: Primordial Gravitational Waves (GWs) represent a key key test of inflation and they are a unique tool to explore the physics and the microphysics of the early Universe. After the GW detections by the LIGO/Virgo collaboration the next target of modern cosmology is the detection of stochastic background of GWs. Even if the main probe of primordial GWs is the Cosmic Microwave Background, we will see in this talk how we can extract information about primordial GWs at smaller smaller scale. In particular the space based LISA interferometer, in addiction to detection and characterization of GWs of astrophysical origin, will give compelling information about the cosmological background of GWs. In this talk I will summarise part of the activity developed within the LISA Cosmology working group, and, in particular, I will discuss on the ability of LISA to test primordial well motivated model of inflation and I will discuss about peculiar features of the SGWB, like anisotropy and non-Gaussian. - 20.11.2020, Tor Nordam (NTNU) : Eulerian and Lagrangian methods for advection-diffusion problems
Abstract: In applied environmental science, such as oceanography and meteorology, transport problems are a common topic. The focus could be the movement of the ocean and atmosphere themselves, or transport of other substances such as pollutants, algae, fish eggs, etc. Different numerical approaches are used, and it is common to separate between Eulerian methods, where you solve the advection-diffusion PDE directly, and Lagrangian methods, where you simulate the random motion of an ensemble of "particles". The idea in the latter case is that the distribution of particles should evolve like the distribution described by the PDE. Mathematically, Lagrangian methods are numerical solutions of a Stochastic Differential Equation (SDEs), whose Fokker-Planck equation is the advection diffusion equation. In this talk, I will describe and illustrate the Eulerian and Lagrangian approaches, using simple 1D examples. I will discuss strengths and weaknesses of the two different approaches, and the conditions that must be satisfied for the two approaches to be equivalent. Finally, I will present some "pitfalls", where a naïve approach can lead to wrong answers. - 22.1.2021, Marco Muzio (NYU)
Germano Nardini (UiS)
Alexander Stasik (UiO)
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