Cosmology Seminars

Cosmology Seminars

 

We have weekly seminars dedicated to Cosmology and Astroparticle Physics (we also have other regular weekly meetings to discuss the latest results in our field). Former presentations are available from the past cosmology seminars pages. Please write to the contact below to join the mailing list.

Time: Wednesdays 14:15-15:15, during term time.

Place: room A315  (3rd floor of the Physicum building)

Format: 50′ + 10′ for questions

Contact: Sofie Koksbang, Francesco Montanari

 

Scheduled Seminars

Spring Term

Autumn Term

    • 29.08.2018 Toyokazu Sekiguchi (University of Tokyo)
      Simulation of the axion electrodynamics and some cosmological applications.
      Abstract: In this talk, I will describe a novel simulation method for the axion electrodynamics. We extend the classical Yee’s algorithm to incorporate the axion. This allows efficient mixing of the dynamics of the axion and electromagnetic fields in addition to accurate conservation of the constraint equations. We then present two cosmological applications of our simulation method. One is suppression of the abundance of the QCD axion via couplings to a hidden photon. The other is the late-time axion magnetogenesis in the presence of magnetic mixing between the SM electromagnetic and a hidden photon fields.
    • 12.09.2018 Eleonora Villa (CTP Warsaw)
      Relativistic perturbation theory in ΛCDM and beyond: Effects on cosmological dynamics and observations.
      Abstract: We present results from the relativistic treatment of cosmological perturbation theory in two contexts. From the theoretical side, we study relativistic corrections to the Newtonian evolution of cosmological perturbations up to second order for a CDM universe with a cosmological constant. We use coordinate systems that extend the Eulerian and Lagrangian pictures to General Relativity. Our novel expressions for all the metric perturbations, matter density and velocity extend previous results in the literature.
      From the observational side, we study the impact of a relativistic derivation of galaxy number counts for future galaxy surveys, considering the ΛCDM model and two extensions: massive neutrinos and modifications of General Relativity. Our study focuses on the biases on the constraints and on the estimation of the cosmological parameters. Our findings show the importance of including lensing in galaxy clustering analyses for testing General Relativity.
    • 10.10.2018 Andi Hektor (KBFI, Tallinn)
      Speculations of new physics on the EDGES 21cm anomaly.
      Abstract: The EDGES experiment has published the first positive results of the measurement of the global cosmological 21cm signal from the young Universe. The surprise was a two times lower baryonic temperature or, alternatively, an enhanced radio background compared to the one predicted by the standard cosmology. As the new physics alone can explain the drop in the temperature or the extra radio background, it has triggered a wave of explanations involving new physics or doubts about the signal extraction. In general, any hypothetical tiny signal of new physics can be more visible in the less complex cosmological and astrophysical environment of the cosmic dawn. For example, an energetic signal from the annihilation or decay of dark matter particle contrasts out more easily. As the baryonic content of the Universe has its coldest moment at the end of cosmic dark ages and just before the first stars start to form (at the redshifts ~20) it allows to search many interesting signals of new physics: milli-charged dark matter, various exotic remnants (axion miniclusters, cosmic defects, primordial black holes), charged exotic particles, earlier shorter epochs of dark energy domination etc. During the upcoming next years, the field will be under very exciting and intensive development. A number of experiments will test the results of EDGES: PRIZM, SARAS2, LEDA, SCI-HI, HYPERION, CPT etc. If the EDGES results will be proven our understanding of the Universe needs some serious revisions. The talk is based on the recent papers: 1805.09319, 1805.06513, 1803.09697, 1803.03245 and the discussions at the workshop, https://indico.cern.ch/event/730318.

Past seminars