Cosmo-torun February 2012

cosmo-torun@cosmo.torun.pl

2 participants
2 discussions

cosmo workshop Fri 2 March @15.00 @KRA: Jan Ostrowski on Cactus: numerical relativity
by Boud Roukema 02 Mar '12

02 Mar '12

hi cosmo-torun Cactus: numerical relativity cosmo workshop Fri 2 March @15.00 @KRA Jan Ostrowski Jan is doing very interesting work in finding out how to do numerical relativity. One way of saying it is the following: "Normal" cosmological N-body simulations consist of *Newtonian* gravity simulated on a highly simplified (perfectly homogeneous) relativistic "background". In formal scientific language, this is called a "heuristic" approach; in informal language, it's called "a fudge" - it's a mathematical shortcut that seems like it should work and lets us quickly compare some sort of "model" to observations instead of waiting 50 years for the mathematics to be solved. In principle, every scientist using the heuristic/fudge is aware of this. Pure theory is very difficult to apply to the real world. Relativistic cosmological simulations should be "directly" relativistic, consistent with the Einstein equations, without using the heuristic/fudge of adding "perturbations" that obey Newtonian gravity to a relativistic "background". So these simulations can be called "background-free". How can we do background-free cosmology simulations? Jan will present a discussion on this. pozdr boud

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grey extinction
by Boud Roukema 27 Feb '12

27 Feb '12

Witam After this morning's seminar, here seem to be a few articles on grey extinction and the \ddot{a}/a > 0 interpretation of the SNe Ia experiments: http://arxiv.org/abs/0909.0231 Grey Milky Way Extinction from SDSS Stellar Photometry Authors: Evgeny Gorbikov, Noah Brosch http://arxiv.org/abs/astro-ph/0701259 Redshift-distance relations from type Ia supernova observations. New constraints on grey dust models Authors: A.R. Robaina, J. Cepa http://arxiv.org/abs/astro-ph/0603833 The Impact of Cosmic Dust on Supernova Cosmology Authors: Pier Stefano Corasaniti http://arxiv.org/abs/astro-ph/0505446 No evidence of "gray" dust from composite quasar spectra Authors: Chris J. Willott http://arxiv.org/abs/astro-ph/0410501 Limiting the dimming of distant type Ia supernovae Authors: Linda Ostman, Edvard Mortsell http://arxiv.org/abs/astro-ph/0306459 Extinction by grey dust in the intergalactic medium Authors: Ernst Fischer pozdr boud

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Cosmo-torun February 2012