81,706 research outputs found
The Neutrino Mass Window for Baryogenesis
Interactions of heavy Majorana neutrinos in the thermal phase of the early
universe may be the origin of the cosmological matter-antimatter asymmetry.
This mechanism of baryogenesis implies stringent constraints on light and heavy
Majorana neutrino masses. We derive an improved upper bound on the CP asymmetry
in heavy neutrino decays which, together with the kinetic equations, yields an
upper bound on all light neutrino masses of 0.1 eV. Lepton number changing
processes at temperatures above the temperature T_B of baryogenesis can erase
other, pre-existing contributions to the baryon asymmetry. We find that these
washout processes become very efficient if the effective neutrino mass
\tilde{m}_1 is larger than m_* \simeq 10^{-3} eV. All memory of the initial
conditions is then erased. Hence, for neutrino masses in the range from (\Delta
m^2_sol)^{1/2} \simeq 8*10^{-3} eV to (\Delta m^2_atm)^{1/2} \simeq 5*10^{-2}
eV, which is suggested by neutrino oscillations, leptogenesis emerges as the
unique source of the cosmological matter-antimatter asymmetry.Comment: 29 pages, 12 figures include
Cosmic Microwave Background, Matter-Antimatter Asymmetry and Neutrino Masses
We study the implications of thermal leptogenesis for neutrino parameters.
Assuming that decays of N_1, the lightest of the heavy Majorana neutrinos,
initiate baryogenesis, we show that the final baryon asymmetry is determined by
only four parameters: the CP asymmetry epsilon_1, the heavy neutrino mass M_1,
the effective light neutrino mass \tilde{m}_1, and the quadratic mean \bar{m}
of the light neutrino masses. Imposing the CMB measurement of the baryon
asymmetry as constraint on the neutrino parameters, we show, in a model
independent way, that quasi-degenerate neutrinos are incompatible with thermal
leptogenesis. For maximal CP asymmetry epsilon_1, and neutrino masses in the
range from (\Delta m^2_{sol})^{1/2} to (\Delta m^2_{atm})^{1/2}, the
baryogenesis temperature is T_B = O(10^{10}) GeV.Comment: 28 pages, 14 figures included; v2: erratum added, M_1 lower bound in
the strong wash-out regime (see Eq. (63)) relaxed by a factor 2/
Some Aspects of Thermal Leptogenesis
Properties of neutrinos may be the origin of the matter-antimatter asymmetry
of the universe. In the seesaw model for neutrino masses this leads to
important constraints on the properties of light and heavy neutrinos. In
particular, an upper bound on the light neutrino masses of 0.1 eV can be
derived. We review the present status of thermal leptogenesis with emphasis on
the theoretical uncertainties and discuss some implications for lepton and
quark mass hierarchies, CP violation and dark matter. We also comment on the
`leptogenesis conspiracy', the remarkable fact that neutrino masses may lie in
the range where leptogenesis works best.Comment: 23 pages, 5 figures, submitted to the Focus on Neutrino Physics issue
of the New Journal of Physics, edited by F. Halzen, M. Lindner and A. Suzuk
Density-correlator signatures of the vulcanization transition
Certain density correlators, measurable via various experimental techniques,
are studied in the context of the vulcanization transition. It is shown that
these correlators contain essential information about both the vulcanization
transition and the emergent amorphous solid state. Contact is made with various
physical ingredients that have featured in experimental studies of amorphous
colloidal and gel systems and in theoretical studies of the glassy state.Comment: 7 pages, 1 figur
Density-correlator signatures of the vulcanization transition
Certain density correlators, measurable via various experimental techniques,
are studied in the context of the vulcanization transition. It is shown that
these correlators contain essential information about both the vulcanization
transition and the emergent amorphous solid state. Contact is made with various
physical ingredients that have featured in experimental studies of amorphous
colloidal and gel systems and in theoretical studies of the glassy state.Comment: 7 pages, 1 figur
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