Wednesday Colloquium


"Non-standard cosmological tests of gravity"

Wojciech Hellwing (Center for Theoretical Physics, Polish Academy of Sciences, Warsaw)

GR is a "perfect" theory that in the last century successfully undergo many stringent observational tests. Its unchallenged position in both small (Solar System) scales and strong field limits (i.e. BH and NS) made it a natural candidate for the fundamental building block for standard cosmological model (LCDM). However, GR has not been so far rigorously tested in the very low-densities and at intergalactic scales. Thus the reality doors are still quite open for many prospective alternative theories commonly dubbed Modified Gravity. I shall recapture the general landscape of the currently very vibrant field of modified gravity theories. I will also discuss why is it absolutely crucial to find and provide as many as possible independent cosmological tests of GR and its competitors. Finally, I will present some of quite non-standard cosmological tests of gravity that me and my collaborators have put forward recently. These include hierarchical amplitudes (scaled higher-order central moments of the density field) and halo/galaxy clustering ratios.


"Adventures with blazar 3C 279"

Krzysztof Nalewajko (CAMK, Warsaw)

I will present a story of 3C 279, one of the most thoroughly investigated blazars. This will include my own efforts, starting in 2009, in close collaboration with Grzegorz Madejski, Masaaki Hayashida and Marek Sikora.


"Infrared features in the ISM and host galaxies of Young Radio Sources"

Emily Kosmaczewski (Rensselaer Polytechnic Institute (Troy, NY))

I will present on the importance of tracing infrared features in interstellar medium and in the host galaxies of young radio sources. Specifically, I will show the breakdown of polycyclic aromatic hydrocarbon (PAH) infrared emission features, the analysis and fitting of such features, the importance of certain features as tracers for star activity, as well as key correlations in the analysis of ISM.


"50 Years of Pulsars"

Bryn Haskell (NCAC, Warsaw)

Neutron stars are the most exotic nuclear physics laboratories in the universe. With a mass similar to that of the sun, packed in a 10 km radius, their interior densities can exceed nuclear density, and constituents are expected to be superfluid and superconducting. These stars also carry some of the strongest magnetic fields in nature (more than a million times that of the Earth, even for the most weakly magnetised stars), and thus allow us to probe the fundamental forces of nature in extreme conditions. Neutron stars were first observed 50 years ago as pulsating radio sources, or 'pulsars'. In this talk I will review this discovery and what we have learned in these 50 years, including how neutron stars can be used to test general relativity, explore high density physics and even detect gravitational waves.