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July 2012

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2 discussions

Newtonian N-body wrong in EdS relativistic 2nd order perturbation theory above 10 Mpc
by Boud Roukema 04 Nov '12

04 Nov '12

hi everyone http://arxiv.org/abs/1207.2035 Newtonian versus relativistic cosmology Authors: Samuel F. Flender, Dominik J. Schwarz Abstract: We show how the relativistic matter and velocity power spectra behave in different gauges. We construct a new gauge where both spectra coincide with Newtonian theory on all scales. However, in this gauge there are geometric quantities present which do not exist in Newtonian theory, for example the local variation of the Hubble parameter. Comparing this quantity to second order Newtonian quantities, we find that Newtonian theory is wrong on scales larger than 10 Mpc. This undermines the reliability of Newtonian cosmological N-body simulations on these scales. What's surprising is that this is still only *perturbation* theory, it's not fully relativistic, if I understand the paper correctly. Fully relativistic calculations still remain to be done. pozdr boud _______________________________________________ Cosmo-torun mailing list Cosmo-torun(a)cosmo.torun.pl http://cosmo.torun.pl/mailman/listinfo/cosmo-torun

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A spiral galaxy at z=2.18
by Andrzej Marecki 20 Jul '12

20 Jul '12

Can a grand-design *spiral* galaxy be located at a redshift z=2.18? Yes it can! http://www.nature.com/nature/journal/v487/n7407/full/nature11256.html -- am _______________________________________________ Cosmo-torun mailing list Cosmo-torun(a)cosmo.torun.pl http://cosmo.torun.pl/mailman/listinfo/cosmo-torun

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