2,239 research outputs found
Legitimacy Conditions for a European Civil Code
legitimacy; multilevel governance; competition policy; subsidiarity; judicial review; European Court of Justice
Amplification of Cosmological Inhomogeneities by the QCD Transition
The cosmological QCD transition affects primordial density perturbations. If
the QCD transition is first order, the sound speed vanishes during the
transition and density perturbations fall freely. For scales below the Hubble
radius at the transition the primordial Harrison-Zel'dovich spectrum of density
fluctuations develops large peaks and dips. These peaks grow with wave number
for both the hadron-photon-lepton fluid and for cold dark matter. At the
horizon scale the enhancement is small. This by itself does not lead to the
formation of black holes at the QCD transition. The peaks in the
hadron-photon-lepton fluid are wiped out during neutrino decoupling. For cold
dark matter that is kinetically decoupled at the QCD transition (e.g., axions
or primordial black holes) these peaks lead to the formation of CDM clumps of
masses .Comment: 39 pages, 10 figures, RevTeX; (1) ETH Zuerich, (2) Univ. Frankfurt;
improved presentation of 'Introduction' and 'Collisional Damping at Neutrino
Decoupling', results unchanged; accepted for publication in Phys. Rev.
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