HIP NEWS February 9th 2015
HIP Staff News
Former HIP Director Dan-Olof Riska has been elected Chair of the Board of Trustees of the Cyprus Institute (www.cyi.ac.cy). The Cyprus Institute is a research oriented university in Nicosia.
DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS
Tuesday 10 February 2015 at 10.15 in A315
K. Kajantie (Helsinki)
Phases and phase transitions of hot QCD with lots of massless quarks
Abstract: For this talk QCD has Nc=3 colors and we want to study what happens when the number of quarks, assumed to be massless, grows, Nf=0,3,6,… We pretend that these numbers are so big that we can use holography, solve the equation of state from a 5-dimensional gravity model. The chirally symmetric quark-gluon plasma phase then is straightforward: temperature and entropy are those of a classical gravity black hole solution. However, at low T there are hadrons, but there is no classical solution giving their hadron gas thermodynamics – there is a T=0 solution from which masses of low-lying states can be computed. So we approach the problem phenomenologically and put in an ansatz for the hadron spectrum. Because of chiral symmetry breaking there at low T are at least Nf^2 massless Goldstone bosons, further there is a partly calculable Hagedorn spectrum of massive states. We try to see how the properties of the chiral phase transition constrain the hadron gas model and show explicitly how the equation of state looks like for a third order phase transition. These phenomenological constructions can be interpreted as 1-loop or even stringy corrections to the classical gravity dual. The final word on phase transition properties lies with lattice Monte Carlo, but imposing zero quark masses is very difficult on the lattice.
Thursday 12 February at 10:15 in E205
Jun’ichi Yokoyama (University of Tokyo)
Magnetogenesis and Schwinger effects in inflationary universe
Abstract: It has been claimed that cosmological magnetic field is ubiquitous even in void regions. Such a maganetic field may have been generated during inflation in the early Universe by breaking the conformal invariance of the gauge field. But in order to avoid the strong coupling problem, one may end up with a larger electric field than the magnetic field. This motivates us to study the Schwinger effect during inflation or in de Sitter space. Making use of a simple model we calculate how Schwinger effect may operate in de Sitter background and discuss its possible implication to inflationary magnetogenesis.
Thursday 12 February at 14:15 in A311
Francesco Montanari (University of Geneva)
Relativistic galaxy number counts: spectrum and bispectrum
Abstract: The fully relativistic expression for galaxy number counts is considered up to second order in perturbation theory. We propose to determine the truly observed galaxy spectrum and bispectrum as function of angles and redshifts. We show that neglecting integrated relativistic terms may bring significant bias on cosmological parameter constraints for future large-scale and deep-redshift galaxy surveys.
New tax cards valid as of 1 February 2015
Old employees: No need to submit your tax card to the employer if your tax information has not changed.
New employees: Submit your tax card to the employer
Please check Flamma https://flamma.helsinki.fi/en/notifications/new-tax-cards-valid-as-of-1-february-2015
F. Montanari 9.2. – 13.2. (KE,SN)
J. Yokoyama 10.2. – 13.2. (KE,SN)