Seminars
Our seminars take place usually in the library of the Main Building (Praha–Sporilov, see
Contacts).
Scheduled:
11.05.2009 14:00
Michal Dovciak
Astronomical Institute, Academy of Sciences, Prague
Newman-Penrose formalism and Walker-Penrose theorem
Abstract
Michal Dovciak
Newman-Penrose formalism and Walker-Penrose theorem
In general relativity in the limit of geometrical optics the
polarization vector is parallelly transported along the light ray.
Therefore in general relativistic polarization calculations the parallel
transfer of vectors along the null geodesic is important. According to
the Walker-Penrose theorem there exists a complex constant that fully
describes this transfer in the black hole solutions of Einstein's
equations. In this talk a proof of the theorem will be given (or rather
sketched). To this purpose firstly the basic concept of Newman-Penrose
formalism will be shown.
18.05.2009 14:00
Birgitta Nordstrom
Niels Bohr Institute, Copenhagen
Our Galactic neighbourhood - a melting pot of migration
Abstract
Birgitta Nordstrom
Our Galactic neighbourhood - a melting pot of migration
Spiral galaxies are an important part of the visible Universe. In the prototype, our own Milky Way, we can observe the most important component of a spiral galaxy - the disk - in unprecedented detail. In the Solar neighbourhood we can determine the numbers, ages, detailed chemical compositions, and galactic orbits of stars from the entire history of the disk with a completeness and accuracy not available anywhere else in the Universe. Therefore, the solar neighbourhood is a fundamental benchmark for all models of the evolution of galaxy disks.
The Geneva-Copenhagen Survey (Nordström et al. 2004 and Holmberg et al. 2007, 2008) has full spatial, kinematic, metallicity and age information for 14,000 long-lived stars and provides a rich source of data for tests of models of evolution and formation of the Galaxy.
We find that classical evolution paradigm of gradual enrichment and dynamical heating of the Galactic disk seem to fail several of the standard tests related to the stellar metallicity distribution, age-metallicity relation, and age-velocity relation. Both dynamical and kinematic evolution need to be taken into account in sufficient detail by the models to match the best data. A search for signatures of past accretion events in the Milky Way (Helmi et al. 2006) has yielded evidence of ancient substructure in the Galactic Disk and a project to study possible chemical signatures is ongoing.
Previous:
16.04.2009 14:30
Luigi Stella
INAF - Osservatorio Astronomico di Roma
Approaching the dawn of gravitational wave astronomy: new inputs from magnetars and short gamma ray bursts
Abstract
Luigi Stella
Approaching the dawn of gravitational wave astronomy: new inputs from magnetars and short gamma ray bursts
The first generation of gravitational wave interferometers has now reached design sensitivity and extensive coordinated scientific runs are about to start. Second generation interferometers, such as Advanced LIGO/Virgo will follow in 4-5 years, are effectively opening the new field of gravitational wave astronomy. Much is still to be learned about the gravitational wave sources from current astrophysical observations
and theory.
I will survey the recent progress achieved in this field through the study of magnetars, neutron stars whose electromagnetic emission is powered by the decay of their extremely high magnetic field, and short gamma ray bursts, which are believed to originate from coalescing neutron star/neutron star of neutron star/black hole binaries.
We try hard to meet regularly to discuss ongoing research projects and recent astro-ph papers.
If you would like to give a seminar in our group, please contact Vladimir Karas.
Everybody is welcome.
Archive
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