Primordial Black Holes and Cosmological Phase Transitions Report ...

Primordial Black Holes and
Cosmological Phase Transitions
Report of Progress of PhD Work
(Second year full time)
Laurindo Sobrinho, Pedro Augusto 1
Departamento de Matemática e Engenharias, Universidade da Madeira
October 2008
Abstract
The Universe is a well developed structure on the scale of galaxies and
smaller formations. This requires that at the beginning of the expansion of
the Universe there should have existed fluctuations which lead to the formation
of such structures. Inflation, a successful cosmological paradigm,
allows us to consider the quantum origin of the fluctuations. Within this
paradigm, we can explain not only all the inhomogeneities we see today
but also the formation of Primordial Black Holes (PBHs). However, PBH
formation requires the amplitude of the fluctuations to be above some
threshold δc. During the cosmological phase transitions, δc experiences a
reduction that favours PBH formation. We have considered this issue in
the case of the Quantum Chromodynamics (QCD) and the Electroweak
(EW) phase transitions. We have also given a similar treatment to the
cosmological electron–positron annihilation epoch. Our results allow the
determination of the fraction of the universe going into PBHs (β). We
have obtained, considering a running–tilt power–law spectrum, results in
the range β ≈ 0 to β ∼ 10 −4 .
1 PhD Supervisor