HIP NEWS May 9th 2016
DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS
Tuesday 10 May 2016 at 10.15 in A315
Kai Schmidt-Hoberg (Desy)
The case for dark matter self interactions – evidence in Abell 3827?
Abstract: I will review motivations for the existence of self interacting dark matter and discuss possible astrophysical observables. Self-interactions of dark matter particles can potentially lead to an observable separation between the dark matter halo and the stars of a galaxy moving through a region of large dark matter density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. I discuss the DM self-interaction cross section needed to reproduce the observed effects.
Wednesday 11 May 2016 at 14.15 in A315
David Wiltshire (Canterbury University)
Models of inhomogeneity and backreaction in cosmology: A status report
Abstract: The possibility of backreaction – that inhomogeneous structures on small (< 100/h Mpc) scales change average cosmic evolution relative to a homogeneous isotropic FLRW cosmology – can be tested in different ways. 1. In our own < 100/h Mpc environment the assumption of a FLRW geometry can be tested model-independently. We present very strong Bayesian evidence that the standard CMB rest frame is not the frame in which the spherically averaged variation of the Hubble expansion is minimized. Using large ray tracing simulations in exact solutions of Einstein’s equations we further show that observations are consistent with a 0.5% differential expansion of space on 100/h Mpc scales detailed models of backreaction are required for cosmological tests. The Timescape Cosmology provides such a phenomenology, without dark energy. We report on the status of observational tests of this model, including fits of the acoustic peaks in the CMB anisotropy spectrum. The Timescape Cosmology passes current tests, and can be distinguished from the FLRW cosmology with future Euclid satellite data. In terms of the CMB we find that the effects of backreaction in the primordial plasma still need to accounted for to deal with systematic uncertainties of 8-13% in particular cosmological parameters.
Deadline for registration May 15th 2016: The Helsinki Workshop on Quantum Gravity
A workshop on quantum gravity will be held in the Physics department the 1st to 3rd of June 2016. The idea of the workshop is to introduce the subject of quantum gravity in Finland. In particular to the interested student.
Deadline for registration: 15th of May 2016
Further information: miklos.langvik[AT]helsinki.fi
The organizing committee
(Esko Keski-Vakkuri, Antti Kupiainen, Miklos Långvik, Kari Rummukainen, Aleksi Vuorinen)
Finnish for international personnel, summer 2016
The summer 2016 course programme is available at helsinki.fi/finnishcourses
Upcoming Events: Nuclear Science and Technology Symposium – NST2016
The Finnish Nuclear Society (FNS) organizes the Nuclear Science and
Technology Symposium – NST2016 on November 2-3, 2016 in Helsinki. The
symposium gathers together research, industry and authority
representatives from Finland and abroad for scientific talks and
industry presentations. The FNS 50-year anniversary dinner and lectures
for the general public are held in connection with the symposium. For
details see the webpage http://www.ats-fns.fi/en/nst2016.
B.S. DiNunno 1.6. – 3.7. (NJ)
M. Hindmarsh 29.4. – 12.6. (KR)
A. Lopez 29.4. – 13.6. (MH, KR)
J. Pedraza 1.6. – 7.6. (NJ)
D. Wiltshire 10.5. – 12.5. (FM)