Astrophysics Seminar: Exploring the dynamical radio sky

Dr. Assaf Horesh, Caltech

10 April 2013, 14:00 
Shenkar Building, Hotcblat Hall 007 
Astrophysics Seminar


I will discuss the recent work on light-cone averaging inhomogeneities in General Relativity and demonstrate its implications for cosmology in the case of the luminosity-redshift relation.  I will present some general results followed by the calculation of the averaged luminosity-redshift relation to second order in perturbations in the concordance model.  The calculation shows that inhomogeneities not only cannot avoid the need for dark energy, but also cannot prevent, in principle the determination of the concordance model parameters to an accuracy of order 10^{-3}-10^{-5} depending on the averaged observable and the regime of the power spectrum considered. However, we predict an irreducible scatter, or dispersion, of the data at the level of 10%, which will necessarily limit the attainable precision. This predicted dispersion is in good agreement with current observational estimates, and represents a challenge to future precision measurements.  If time permits, I will show how this dispersion in the luminosity-redshift relation can be used to constrain the primordial power spectrum on scales out of reach of CMB experiments.


Seminar Organiser: Prof. Rennan Barkana

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