"Theory of Particle Physics and Cosmology" Seminar
2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024
2017-10-26 (Thursday)
room B0.14, Pasteura 5 at 12:15 
Alon Faraggi (University of Liverpool, UK)The quest for unification
The quest for unification is a prevailing theme is physics, from Newton who unified terrestrial and celestial mechanics, to modern day efforts to synthesize general relativity and quantum mechanics. I will describe contemporary work on two fronts in this direction. The first is the construction of phenomenological heterotic-string models and the study of a particular class that produced solely the spectrum of the Minimal Supersymmetric Standard Model in their low energy effective field theory. I will describe efforts to extract experimental predictions beyond the Standard Model in the form of extra Z' and dark matter candidates. The role of fundamental symmetries in the construction, as well as fundamental principles that may underline quantum gravity will be discussed. The presentation will be non--technical and suitable for a general audience.
2017-10-19 (Thursday)
room B0.14, Pasteura 5 at 12:15
Janusz Rosiek (IFT UW)Physical structure, quantization and interactions in the Standard Model Effective Field Theory
Effects of high scale "New Physics" can be always parametrized using the Effective Field Theory approach, where Standard Model (SM) interactions are extended by operators of higher dimensions. I will discuss the structure of the SM extended by all gauge invariant operators of dimension 5 and 6, physical field states in such a model, its quantization in R_xi gauges and generation of Feynman rules for the tree-level and loop calculations.
2017-10-12 (Thursday)
room B0.14, Pasteura 5 at 12:15
Da Huang (IFT UW)Strongly Self-Interacting Vector Dark Matter via Freeze-in
In the view of strong constraints from dark matter (DM) direct and indirect searches on the conventional self-interacting DM model in which the DM is generated by the freeze-out mechanism, we study a vector DM (VDM) model in which the VDM can be produced by the freeze-in mechanism through the Higgs portal to the Standard Model sector. It turns out that the electroweak phase transition have a substantial impact on the prediction of the VDM relic density. We further assume that the dark Higgs boson which gives the VDM mass is so light that it can induce strong VDM self-interactions and solve the small-scale structure problems of the Universe. As illustrated by the latest LUX data, the extreme smallness of the Higgs portal coupling required by the freeze-in mechanism implies that the dark matter direct detection bounds are easily satisfied. However, the model is well constrained by the DM indirect detection data from BBN, CMB, AMS-02, and diffuse γ/X-rays. Consequently, only when the dark Higgs mass is at most of O(keV) does there exist a parameter region which leads to a correct amount of VDM relic abundance and an appropriate VDM self-scattering while satisfying all other constraints simultaneously.
2017-10-05 (Thursday)
room B0.14, Pasteura 5 at 12:15
Alexei A. Starobinsky (Landau Institute for Theoretical Physics RAS, Moscow-Chernogolovka, Russia)Reconstruction and formation of inflation in f(R) gravity
f(R) gravity represents the simplest purely geometrical generalization of the Einstein general theory of relativity without undesirable ghosts. The pioneer R+R^2 model of inflation (AS, 1980) contains only one adjustable parameter taken from observations, has a graceful exit from inflation and a natural mechanism for creation and heating of matter after its end, and produces a very good fit to existing observational data on the power spectrum of primordial scalar (adiabatic density) perturbations. Regarding its possible UV completion, it was recently shown that this model can be included as a particular solution into a weakly non-local UV-complete generalization of quantum gravity which is super-renormalizable or finite and does not contain ghosts. I consider the inverse problem of reconstruction of inflationary models in f(R) gravity using information on the power spectrum of scalar perturbations only, ambiguity in this procedure and how it can be fixed by some aesthetic assumptions on the absence of new physical scales during and after inflation. Also discussed is the problem on formation of inflation from generic classical curvature singularity preceding it, and which conditions are needed for this. Since this process is generic, too, for inflation to begin inside a patch including the observable part of the Universe, causal connection inside the whole patch is not necessary. However, it becomes obligatory for a graceful exit from inflation in order to have practically the same number of e-folds during inflation inside this patch.