1,345 research outputs found
Semiclassical fermion pair creation in de Sitter spacetime
We present a method to semiclassically compute the pair creation rate of
bosons and fermions in de Sitter spacetime. The results in the bosonic case
agree with the ones in the literature. We find that for the constant electric
field the fermionic and bosonic pair creation rate are the same. This analogy
of bosons and fermions in the semiclassical limit is known from several flat
spacetime examples.Comment: 10 pages, no figure, proceeding of the 2nd Cesare Lattes Meetin
Schwinger effect and backreaction in de Sitter spacetime
We consider the particle-antiparticle pairs produced by both a strong
electric field and de Sitter curvature. We investigate in 1 + 1 D the
backreaction of the pairs on the electromagnetic field. To do so we describe
the canonical quantization of an electromagnetic field in de Sitter space and
add in the Einstein-Maxwell equation the fermionic current induced by the
pairs. After solving this equation, we find that the electric field gets either
damped or unaffected depending on the value of the pair mass and the gauge
coupling. No enhancement of the electromagnetic field to support a
magnetogenesis scenario is found. The physical picture is that the Schwinger
pairs locally created screen the production and amplification of the
electromagnetic field. However, if one considers light bosons created by the
Schwinger mechanism, we report a solution to the Einstein-Maxwell equation with
an enhancement of the electromagnetic field. This solution could be a new path
to primordial magnetogenesis.Comment: 9 pages, 4 figures, matches published versio
A model of interacting dark fluids tested with supernovae and Baryon Acoustic Oscillations data
We compare supernovae and Baryon Acoustic Oscillations data to the
predictions of a cosmological model of interacting dark matter and dark energy.
This theoretical model can be derived from the effective field theory of
Einstein-Cartan gravity with two scaling exponents and
, related to the interaction between dark matter and dark
energy. We perform a fit to the data to compare and contrast it with
the standard CDM model. We then explore the range of parameter of the
model which gives a better than the standard cosmological model. All
those results lead to tight constraints on the scaling exponents of the model.
Our conclusion is that this class of models, provides a decent alternative to
the CDM model.Comment: 7 pages, 2 figures, 1 table, matches published versio
Exploring the effects of primordial non-Gaussianity at galactic scales
While large scale primordial non-Gaussianity is strongly constrained by
present-day data, there are no such constraints at Mpc scales. Here we
investigate the effect of significant small-scale primordial non-Gaussianity on
structure formation and the galaxy formation process with collisionless
simulations: specifically, we explore four different types of
non-Gaussianities. Generically, we find a distinct and potentially detectable
feature in the matter power spectrum around the non-linear scale. We then show
in particular that a negatively-skewed distribution of the potential random
field, hence positively skewed in terms of overdensities, with at these scales, implies that typical galaxy-sized halos reach
half of their present-day mass at an earlier stage and have a quieter merging
history than in the Gaussian case. Their environment between 1 and 5 virial
radii at is less dense than in the Gaussian case. This quieter history
and less dense environment has potentially interesting consequences in terms of
the formation of bulges and bars. Moreover, we show that subhalos have a more
flattened distribution around their host than in the Gaussian case, albeit not
as flattened as the 11 most massive Milky Way satellites, and that the two most
massive subhalos tend to display an interesting anti-correlation of velocities
around their host, indicative of kinematic coherence. All these hints will need
to be statistically confirmed in larger-box simulations with scale-dependent
non-Gaussian initial conditions, followed by hydrodynamical zoom-in simulations
to explore the detailed consequences of small-scale non-Gaussianities on galaxy
formation.Comment: 23 pages, 8 figures, 3 tables, comments welcome
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