|Title:||Weighing the Universe with the Lightest Elements|
|Speaker:||Max Pettini (University of Cambridge)|
|Date:||Thursday, 26 March 2015|
|Time:||11:00 - 12:00|
The nucleosynthesis of the lightest elements of the periodic table, hydrogen, helium, lithium and their isotopes, during the first few minutes of our Universe’s history is one of the cornerstones of the standard model of cosmology and particle physics. In the last few years, it has become possible to determine the primordial abundances of these elements with high precision, finally realising their long-appreciated potential for measuring the cosmic density of ordinary matter. In this colloquium, I shall review the latest developments in the determination of the primordial abundance of deuterium in particular, using the technique of QSO Absorption Line Spectroscopy. The ‘punch line’ is that independent measures of the density of baryons at different cosmic epochs are in excellent mutual agreement. Such concordance places interesting limits on the existence of relativistic particles beyond the standard model of physics.