135 research outputs found
Standard Model CP-violation and Cold Electroweak Baryogenesis
Using large scale real-time lattice simulations, we calculate the baryon
asymmetry generated at a fast, cold electroweak symmetry breaking transition.
CP-violation is provided by the leading effective bosonic term resulting from
integrating out the fermions in the Minimal Standard Model at zero temperature,
and performing a covariant gradient expansion [1]. This is an extension of the
work presented in [2]. The numerical implementation is described in detail, and
we address issues specifically related to using this CP-violating term in the
context of Cold Electroweak Baryogenesis. The results support the conclusion of
[2], that Standard Model CP-violation may be able to reproduce the observed
baryon asymmetry in the Universe in the context of Cold Electroweak
Baryogenesis.Comment: 27 pages, 5 figures. Revision, clarification and focusing of
presentation, typos fixed, results unchange
Cold Electroweak Baryogenesis in the Two Higgs-Doublet Model
We perform the first investigation of cold electroweak baryogenesis in the
two Higgs-doublet model (2HDM). The electroweak symmetry breaking transition is
assumed to occur through a spinodal instability from a super-cooled initial
state. We consider the creation of net Chern-Simons number, which through the
axial anomaly is equivalent to baryon number. CP-violation is explicit in the
scalar potential, but only in combination with P-violation is it possible for
an asymmetry to be generated. This is introduced through the leading C- and
P-breaking, but CP-invariant, term expected to arise upon integrating out the
fermions in the theory. We perform real-time lattice simulations of the
transition, and find the coefficient of this term required for successful
bayogenesis.Comment: 20 pages, 18 figure
Thermal blocking of preheating
The parametric resonance responsible for preheating after inflation will end
when self-interactions of the resonating field and interactions of this field
with secondary degrees of freedom become important. In many cases, the effect
may be quantified in terms of an effective mass and the resulting shifting out
of the spectrum of the strongest resonance band. In certain curvaton models,
such thermal blocking can even occur before preheating has begun, delaying or
even preventing the decay of the curvaton. We investigate numerically to what
extent this thermal blocking is realised in a specific scenario, and whether
the effective mass is well approximated by the perturbative leading order
thermal mass. We find that the qualitative behaviour is well reproduced in this
approximation, and that the end of preheating can be confidently estimated.Comment: 13 pages, 4 figures. v2: references adde
A Simple Method for One-Loop Renormalization in Curved Space-Time
We present a simple method for deriving the renormalization counterterms from
the components of the energy-momentum tensor in curved space-time. This method
allows full control over the finite parts of the counterterms and provides
explicit expressions for each term separately. As an example, the method is
used for the self-interacting scalar field in a Friedmann-Robertson-Walker
metric in the adiabatic approximation, where we calculate the renormalized
equation of motion for the field and the renormalized components of the
energy-momentum tensor to fourth adiabatic order while including interactions
to one-loop order. Within this formalism the trace anomaly, including
contributions from interactions, is shown to have a simple derivation. We
compare our results to those obtained by two standard methods, finding
agreement with the Schwinger-DeWitt expansion but disagreement with adiabatic
subtractions for interacting theories.Comment: 25 pages, published versio
Simulations of Cold Electroweak Baryogenesis: Dependence on Higgs mass and strength of CP-violation
Cold electroweak baryogenesis was proposed as a scenario to bypass generic
problems of electroweak baryogenesis within the Standard Model. In this
scenario, baryogenesis takes place during an electroweak symmetry breaking
transition, which is also responsible for preheating after inflation. In the
simplest modelling of the scenario, only two parameters remain undetermined:
The Higgs mass and the strength of CP violation. Using full real-time lattice
simulations, we compute the dependence of the asymmetry on these parameters.Comment: 14 pages, 13 figure
Oscillons and quasi-breathers in D+1 dimensions
We study oscillons in D+1 space-time dimensions using a spherically symmetric
ansatz. From Gaussian initial conditions, these evolve by emitting radiation,
approaching ``quasi-breathers'', near-periodic solutions to the equations of
motion. Using a truncated mode expansion, we numerically determine these
quasi-breather solutions in 2<D<6 and the energy dependence on the oscillation
frequency. In particular, this energy has a minimum, which in turn depends on
the number of spatial dimensions. We study the time evolution and lifetimes of
the resulting quasi-breathers, and show how generic oscillons decay into these
before disappearing altogether. We comment on the apparent absence of oscillons
for D>5 and the possibility of stable solutions for D<2.Comment: 18 pages and 18 figure
Four results on phi^4 oscillons in D+1 dimensions
We present four results for oscillons in classical phi^4 theory in D+1
space-time dimensions, based on numerical simulations. These include the
oscillon lifetime and the dependence on D; evidence for the uniqueness of the
oscillon; evidence for the existence of oscillons beyond D=7; and a brief study
of the spectrum of the radiation emitted from the oscillons before, during and
after its ultimate demise.Comment: 12 pages, 16 figure
On the quantum stability of Q-balls
We consider the evolution and decay of Q-balls under the influence of quantum
fluctuations. We argue that the most important effect resulting from these
fluctuations is the modification of the effective potential in which the Q-ball
evolves. This is in addition to spontaneous decay into elementary particle
excitations and fission into smaller Q-balls previously considered in the
literature, which -- like most tunnelling processes -- are likely to be
strongly suppressed. We illustrate the effect of quantum fluctuations in a
particular model potential, for which we implement the inhomogeneous
Hartree approximation to quantum dynamics and solve for the evolution of
Q-balls in 3+1 dimensions. We find that the stability range as a function of
(field space) angular velocity is modified significantly compared to
the classical case, so that small- Q-balls are less stable than in the
classical limit, and large- Q-balls are more stable. This can be
understood qualitatively in a simple way.Comment: JHEP format, 17+1 pages, 9 figures; v2: improvements to several
figures, text rewritten to improve legibility, conclusions unchanged,
published in JHE
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