158 research outputs found
Gravitational radiation from a bulk flow model
We perform simulations in a simple model that aims to mimic the hydrodynamic
evolution of a relativistic fluid during a cosmological first-order phase
transitions. The observable we are concerned with is hereby the spectrum of
gravitational radiation produced by colliding fluid shells. We present simple
parameterizations of our results as functions of the wall velocity, the
duration of the phase transition and the latent heat. We also improve on
previous results in the envelope approximation and compare with hydrodynamic
simulations.Comment: 19 pages, 7 figures, matches published versio
Resummation of Goldstone Infrared Divergences: A Proof to All Orders
The perturbative effective potential calculated in Landau gauge suffers from
infrared problems due to Goldstone boson loops. These divergences are spurious
and can be removed by a resummation procedure that amounts to a shift of the
mass of soft Goldstones. We prove this to all loops using an effective theory
approach, providing a compact recipe for the shift of the Goldstone mass that
relies on the use of the method of regions to split soft and hard Goldstone
contributions.Comment: 30 pages, 3 figure
CP-violation for Electroweak Baryogenesis from Dynamical CKM Matrix
We show that the CKM matrix can be the source of CP violation for electroweak
baryogenesis if Yukawa couplings vary at the same time as the Higgs acquires
its vacuum expectation value. This offers new avenues for explaining the baryon
asymmetry of the universe. These ideas apply if the mechanism explaining the
flavour structure of the Standard Model is connected to electroweak symmetry
breaking. We compute the resulting baryon asymmetry for various low-scale
flavour models and different configurations of the Yukawa coupling variation
across the bubble wall, and show that it can naturally be of the right order.Comment: 43 pages, 17 figures; v2: replaced mismatched plot in Figure 8 and
corrected a typo in the caption; v3: JCAP published version, clarifications
added, results unchange
Cosmological perturbation theory at three-loop order
We analyze the dark matter power spectrum at three-loop order in standard
perturbation theory of large scale structure. We observe that at late times the
loop expansion does not converge even for large scales (small momenta) well
within the linear regime, but exhibits properties compatible with an asymptotic
series. We propose a technique to restore the convergence in the limit of small
momentum, and use it to obtain a perturbative expansion with improved
convergence for momenta in the range where baryonic acoustic oscillations are
present. Our results are compared with data from N-body simulations at
different redshifts, and we find good agreement within this range.Comment: 29 pages, 8 figures, 1 table; v2 Typos corrected, references added.
Matches published versio
From Boltzmann equations to steady wall velocities
By means of a relativistic microscopic approach we calculate the expansion
velocity of bubbles generated during a first-order electroweak phase
transition. In particular, we use the gradient expansion of the Kadanoff-Baym
equations to set up the fluid system. This turns out to be equivalent to the
one found in the semi-classical approach in the non-relativistic limit.
Finally, by including hydrodynamic deflagration effects and solving the Higgs
equations of motion in the fluid, we determine velocity and thickness of the
bubble walls. Our findings are compared with phenomenological models of wall
velocities. As illustrative examples, we apply these results to three theories
providing first-order phase transitions with a particle content in the thermal
plasma that resembles the Standard Model.Comment: 40 pages, 8 figures; v2: added references, version published in JCA
Hybrid Inflation Exit through Tunneling
For hybrid inflationary potentials, we derive the tunneling rate from field
configurations along the flat direction towards the waterfall regime. This
process competes with the classically rolling evolution of the scalar fields
and needs to be strongly subdominant for phenomenologically viable models.
Tunneling may exclude models with a mass scale below 10^12 GeV, but can be
suppressed by small values of the coupling constants. We find that tunneling is
negligible for those models, which do not require fine tuning in order to
cancel radiative corrections, in particular for GUT-scale SUSY inflation. In
contrast, electroweak scale hybrid inflation is not viable, unless the
inflaton-waterfall field coupling is smaller than approximately 10^-11.Comment: 17 pages, 2 figure
Gauge-Independent Scales Related to the Standard Model Vacuum Instability
The measured (central) values of the Higgs and top quark masses indicate that
the Standard Model (SM) effective potential develops an instability at high
field values. The scale of this instability, determined as the Higgs field
value at which the potential drops below the electroweak minimum, is about
GeV. However, such a scale is unphysical as it is not gauge-invariant
and suffers from a gauge-fixing uncertainty of up to two orders of magnitude.
Subjecting our system, the SM, to several probes of the instability (adding
higher order operators to the potential; letting the vacuum decay through
critical bubbles; heating up the system to very high temperature; inflating it)
and asking in each case physical questions, we are able to provide several
gauge-invariant scales related with the Higgs potential instability.Comment: 44 pages, 9 figure
On the Soft Limit of the Large Scale Structure Power Spectrum: UV Dependence
We derive a non-perturbative equation for the large scale structure power
spectrum of long-wavelength modes. Thereby, we use an operator product
expansion together with relations between the three-point function and power
spectrum in the soft limit. The resulting equation encodes the coupling to
ultraviolet (UV) modes in two time-dependent coefficients, which may be
obtained from response functions to (anisotropic) parameters, such as spatial
curvature, in a modified cosmology. We argue that both depend weakly on
fluctuations deep in the UV. As a byproduct, this implies that the renormalized
leading order coefficient(s) in the effective field theory (EFT) of large scale
structures receive most of their contribution from modes close to the
non-linear scale. Consequently, the UV dependence found in explicit
computations within standard perturbation theory stems mostly from
counter-term(s). We confront a simplified version of our non-perturbative
equation against existent numerical simulations, and find good agreement within
the expected uncertainties. Our approach can in principle be used to precisely
infer the relevance of the leading order EFT coefficient(s) using small volume
simulations in an `anisotropic separate universe' framework. Our results
suggest that the importance of these coefficient(s) is a effect,
and plausibly smaller.Comment: 25+5 pages, 10 figures, comments added, matches published versio
Quantum Corrections to the Reissner-Nordstr\"{o}m and Kerr-Newman Metrics
We use effective field theory techniques to examine the quantum corrections
to the gravitational metrics of charged particles, with and without spin. In
momentum space the masslessness of the photon implies the presence of
nonanalytic pieces etc. in the form factors of
the energy-momentum tensor. We show how the former reproduces the classical
non-linear terms of the Reissner-Nordstr\"{o}m and Kerr-Newman metrics while
the latter can be interpreted as quantum corrections to these metrics, of order
Comment: 16 page latex file with two figure
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