Cosmology and neutrino masses - an update

Present cosmological observations yield an upper bound on the neutrino mass which is significantly stronger than laboratory bounds. However, the exact value of the cosmological bound is model dependent and therefore less robust. Here, I review the current status of cosmological neutrino mass bounds and also discuss implications for sterile neutrinos and LSND in particular.Comment: 5 pages, 2 figures, invited talk at neutrino session, EPS 2003 meeting in Aache

Cosmological bounds on masses of neutrinos and other thermal relics

With the advent of precision data, cosmology has become an extremely powerful tool for probing particle physics. The prime example of this is the cosmological bound on light neutrino masses. Here I review the current status of cosmological neutrino mass bounds as well as the various uncertainties involved in deriving them. From WMAP, SDSS, and Lyman-alpha forest data an upper bound on the sum of neutrino masses of 0.65 eV (95% C.L.) can be derived with any assumptions about bias. I also present new limits on other light, thermally produced particles. For example, a hypothetical new Majorana fermion decoupling around the electroweak phase transition must have m < 5 eV.Comment: 10 pages, 3 figures, to appear in SeeSaw '25 proceedings, references update

Neutrino cosmology - an update

Present cosmological observations yield an upper bound on the neutrino mass which is significantly stronger than laboratory bounds. However, the exact value of the cosmological bound is model dependent and therefore less robust. Here, I review the current status of cosmological neutrino mass bounds and also discuss implications for sterile neutrinos and LSND in particular.Comment: Invited talk at Thinking, observing, and mining the universe, Sorrento, Italy (22-27 September 2003

Non-equilibrium effects on particle freeze-out in the early universe

We investigate the possible effects that deviations from kinetic equilibrium can have on massive particles as they decouple from chemical equilibrium. Different methods of solving the Boltzmann equation yield significantly different relic number densities of such particles. General considerations concerning the Dirac or Majorana structure of the particles are discussed. It is shown that non-equilibrium effects are small for particles decoupling while strongly non-relativistic, as will be the case for most cold dark matter candidates.Comment: 9 pages REVTEX, to appear in New Astronom

Neutrino physics from Cosmology

In recent years precision cosmology has become an increasingly powerful probe of particle physics. Perhaps the prime example of this is the very stringent cosmological upper bound on the neutrino mass. However, other aspects of neutrino physics, such as their decoupling history and possible non-standard interactions, can also be probed using observations of cosmic structure. Here, I review the current status of cosmological bounds on neutrino properties and discuss the potential of future observations, for example by the recently approved EUCLID mission, to precisely measure neutrino properties.Comment: 8 pages, 2 figures, to appear in the proceedings of Pontecorvo100 - Symposium in honour of Bruno Pontecorv