84 research outputs found
Generation of the Baryon Asymmetry of the Universe within the Left--Right Symmetric Model
Fermions scattering off first-order phase transition bubbles, in the
framework of models, may generate the
Baryon Asymmetry of the Universe (BAU), either at the -symmetry-breaking
scale, or at the weak scale. In the latter case, the baryon asymmetry of the
Universe is related to CP violation in the -- system.Comment: 17 pages, CERN--TH 6747/92, ULB--TH--07/92, UAB-FT-298/9
Sphalerons and the Electroweak Phase Transition in Models with Higher Scalar Representations
In this work we investigate the sphaleron solution in a
gauge theory, which also encompasses the Standard Model, with higher scalar
representation(s) (). We show that the field profiles
describing the sphaleron in higher scalar multiplet, have similar trends like
the doublet case with respect to the radial distance. We compute the sphaleron
energy and find that it scales linearly with the vacuum expectation value of
the scalar field and its slope depends on the representation. We also
investigate the effect of gauge field and find that it is small for the
physical value of the mixing angle, and resembles the case for the
doublet. For higher representations, we show that the criterion for strong
first order phase transition, , is relaxed with respect to
the doublet case, i.e. .Comment: 20 pages, 5 figures & 1 table, published versio
The Dark Side of the Electroweak Phase Transition
Recent data from cosmic ray experiments may be explained by a new GeV scale
of physics. In addition the fine-tuning of supersymmetric models may be
alleviated by new O(GeV) states into which the Higgs boson could decay. The
presence of these new, light states can affect early universe cosmology. We
explore the consequences of a light (~ GeV) scalar on the electroweak phase
transition. We find that trilinear interactions between the light state and the
Higgs can allow a first order electroweak phase transition and a Higgs mass
consistent with experimental bounds, which may allow electroweak baryogenesis
to explain the cosmological baryon asymmetry. We show, within the context of a
specific supersymmetric model, how the physics responsible for the first order
phase transition may also be responsible for the recent cosmic ray excesses of
PAMELA, FERMI etc. We consider the production of gravity waves from this
transition and the possible detectability at LISA and BBO
Condensed matter lessons about the origin of time
It is widely hoped that quantum gravity will shed light on the question of
the origin of time in physics. The currently dominant approaches to a candidate
quantum theory of gravity have naturally evolved from general relativity, on
the one hand, and from particle physics, on the other hand. A third important
branch of 20th century `fundamental' physics, condensed-matter physics, also
offers an interesting perspective on quantum gravity, and thereby on the
problem of time. The bottomline might sound disappointing: to understand the
origin of time, much more experimental input is needed than what is available
today. Moreover it is far from obvious that we will ever find out the true
origin of physical time, even if we become able to directly probe physics at
the Planck scale. But we might learn some interesting lessons about time and
the structure of our universe in the process. A first lesson is that there are
probably several characteristic scales associated with "quantum gravity"
effects, rather than the single Planck scale usually considered. These can
differ by several orders of magnitude, and thereby conspire to hide certain
effects expected from quantum gravity, rendering them undetectable even with
Planck-scale experiments. A more tentative conclusion is that the hierarchy
between general relativity, special relativity and Newtonian physics, usually
taken for granted, might have to be interpreted with caution.Comment: v1: 9 pages. Fourth juried prize in FQXi essay contest on "the Nature
of Time" (2008). v2: 2015 update, partially rewritten and extended for
Foundations of Physics. arXiv admin note: substantial text overlap with
arXiv:0810.061
Skyrmion Multi-Walls
Skyrmion walls are topologically-nontrivial solutions of the Skyrme system
which are periodic in two spatial directions. We report numerical
investigations which show that solutions representing parallel multi-walls
exist. The most stable configuration is that of the square -wall, which in
the limit becomes the cubically-symmetric Skyrme crystal. There is
also a solution resembling parallel hexagonal walls, but this is less stable.Comment: 7 pages, 1 figur
The Sphaleron Rate in SU(N) Gauge Theory
The sphaleron rate is defined as the diffusion constant for topological
number NCS = int g^2 F Fdual/32 pi^2. It establishes the rate of equilibration
of axial light quark number in QCD and is of interest both in electroweak
baryogenesis and possibly in heavy ion collisions. We calculate the
weak-coupling behavior of the SU(3) sphaleron rate, as well as making the most
sensible extrapolation towards intermediate coupling which we can. We also
study the behavior of the sphaleron rate at weak coupling at large Nc.Comment: 18 pages with 3 figure
Photometric redshifts for supernovae Ia in the Supernova Legacy Survey
We present a method using the SALT2 light curve fitter to determine the
redshift of Type Ia supernovae in the Supernova Legacy Survey (SNLS) based on
their photometry in g', r', i' and z'. On 289 supernovae of the first three
years of SNLS data, we obtain a precision on
average up to a redshift of 1.0, with a higher precision of 0.016 for z<0.45
and a lower one of 0.025 for z>0.45. The rate of events with (catastrophic errors) is 1.4%. Both the precision and the rate
of catastrophic errors are better than what can be currently obtained using
host galaxy photometric redshifts. Photometric redshifts of this precision may
be useful for future experiments which aim to discover up to millions of
supernovae Ia but without spectroscopy for most of them.Comment: 7 pages, 9 figures, published in Astronomy and Astrophysic
Baryon Washout, Electroweak Phase Transition, and Perturbation Theory
We analyze the conventional perturbative treatment of sphaleron-induced
baryon number washout relevant for electroweak baryogenesis and show that it is
not gauge-independent due to the failure of consistently implementing the
Nielsen identities order-by-order in perturbation theory. We provide a
gauge-independent criterion for baryon number preservation in place of the
conventional (gauge-dependent) criterion needed for successful electroweak
baryogenesis. We also review the arguments leading to the preservation
criterion and analyze several sources of theoretical uncertainties in obtaining
a numerical bound. In various beyond the standard model scenarios, a realistic
perturbative treatment will likely require knowledge of the complete two-loop
finite temperature effective potential and the one-loop sphaleron rate.Comment: 25 pages, 9 figures; v2 minor typos correcte
New AdS solitons and brane worlds with compact extra-dimensions
We construct new static, asymptotically AdS solutions where the conformal
infinity is the product of Minkowski spacetime and a sphere . Both
globally regular, soliton-type solutions and black hole solutions are
considered. The black holes can be viewed as natural AdS generalizations of the
Schwarzschild black branes in Kaluza-Klein theory. The solitons provide new
brane-world models with compact extra-dimensions. Different from the
Randall-Sundrum single-brane scenario, a Schwarzschild black hole on the Ricci
flat part of these branes does not lead to a naked singularity in the bulk.Comment: 28 pages, 4 figure
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