Theorie Palaver

Programm für das Wintersemester 2019/2020

Dienstags, 14:30 Uhr s.t.

Ort: Institut für Physik, MITP seminar room

15.10.19Fatemeh Elahi, IPM, Tehran
A few hundred cold gas clouds were recently discovered, each situated a few hundred parsecs from the center of the Milky Way Galaxy. These gas clouds can provide unprecedented sensitivity to dark matter-standard model interactions. The main physical basis is simple: dark matter tends to have a higher temperature than the coldest interstellar and intergalactic gas. Therefore, dark matter can heat the gas to higher-than-observed temperatures, if dark matter interacts enough with baryons or electrons in the gas cloud. In this talk, I will discuss the bounds cold gas clouds give on ultra-light dark photon, vector portal, and millicharged dark matter.
22.10.19Andreas Helset, Bohr Institute
We formulate an effective field theory describing large mass scalars and fermions minimally coupled to gravity. The operators of this effective field theory are organized in powers of the transfer momentum divided by the mass of the matter field, an expansion which lends itself to the efficient extraction of classical contributions from loop amplitudes in both the post-Newtonian and post-Minkowskian regimes. We use this effective field theory to calculate the classical and leading quantum gravitational scattering amplitude of two heavy spin-1/2 particles at the second post-Minkowskian order.
29.10.19Alexey Vladimirov, Regensburg University
The evolution of transverse momentum dependent distributions or TMD-evolution differs from ordinary renormalization group evolution in several aspects. Two main ones are its double-scale nature and the presence of non-perturbative component. In the talk, I review the recent progress in studies of TMD-evolution, including the proof of rapidity-divergence renormalization, soft-rapidity correspondence, zeta-prescription, and comparison with the experimental measurements.
05.11.19Enrico Morgante, Johannes Gutenberg-Universität
The relaxion mechanism is a proposed solution to the hierarchy problem, in which the EW scale is set by the classical evolution of a scalar field in the early universe. In this talk, I will review this construction and discuss some recent developments.
zukünftige Termine
19.11.19Leonardo Vernazza, Nikhef
Scattering processes near threshold develop large logarithms, that need to be resummed. In my talk I will focus in particular on electroweak annihilation processes, such as Drell-Yan and Higgs production in gluon fusion, and discuss the underlying factorisation theorems which allow the resummation of such logarithms at next-to-leading power, comparing diagrammatic and effective field theory methods.
03.12.19Matthias Heller, Johannes Gutenberg-Universität
10.12.19Guoxing Wang, Peking University
17.12.19Fazlollah Hajkarim, Frankfurt University
Using the quantum chromodynamics (QCD) equation of state (EoS) from lattice calculations we investigated QCD effects on the first order primordial gravitational waves (PGWs) produced during the inflationary era. We also considered the cases for vanishing and nonvanishing lepton asymmetry where the latter one is constrained by cosmic microwave background experiments. Also, we investigated scenarios that inflation is succeeded by a phase where the energy density of the Universe was dominated by a scalar component with a general equation of state. Then we evaluated the spectrum of primordial gravitational waves induced in the post-inflationary Universe. We showed that if the energy density of the Universe was dominated by some specific fluid 𝜙 before Big Bang Nucleosynthesis (BBN), its equation of state could be constrained by gravitational wave experiments. Moreover, we studied the effect of QCD and electroweak transitions on the induced (or second order) PGW from scalar perturbations which is different from the first order PGW spectrum. Finally, I briefly discuss the production of dark matter (DM) in an early matter era dominated by a heavy long lived scalar field.
Koordinator und Kontakt:
Dr. Zoltan Ször
Institut für Physik, THEP