130 research outputs found
Gravitational waves from deflagration bubbles in first-order phase transitions
The walls of bubbles in a first-order phase transition can propagate either
as detonations, with a velocity larger than the speed of sound, or
deflagrations, which are subsonic. We calculate the gravitational radiation
that is produced by turbulence during a phase transition which develops via
deflagration bubbles. We take into account the fact that a deflagration wall is
preceded by a shock front which distributes the latent heat throughout space
and influences other bubbles. We show that turbulence can induce peak values of
as high as . We discuss the possibility of
detecting at LISA gravitational waves produced in the electroweak phase
transition with wall velocities , which favor electroweak
baryogenesis.Comment: 13 pages, 1 figure; calculations of section IV repeated using recent
results for the GW spectrum from turbulence, comments added in all sections,
references added, conclusions unchange
On the nucleation of hadronic domains in the quark-hadron transition
We present numerical results on bubble profiles, nucleation rates and time
evolution for a weakly first-order quark-hadron phase transition in different
expansion scenarios. We confirm the standard picture of a cosmological
first-order phase transition, in which the phase transition is entirely
dominated by nucleation. We also show that, even for expansion rates much lower
than those expected in heavy-ion collisions nucleation is very unlikely,
indicating that the main phase conversion mechanism is spinodal decomposition.Comment: 4 pages, 2 images. To be published in the proceedings of SEWM 200
Effective potential at finite temperature in a constant magnetic field I: Ring diagrams in a scalar theory
We study symmetry restoration at finite temperature in the theory of a
charged scalar field interacting with a constant, external magnetic field. We
compute the finite temperature effective potential including the contribution
from ring diagrams. We show that in the weak field case, the presence of the
field produces a stronger first order phase transition and that the temperature
for the onset of the transition is lower, as compared to the case without
magnetic field.Comment: Expanded comments, 4 figures added. Conclusions unchanged. Version to
match published pape
Effective potential at finite temperature in a constant hypermagnetic field: Ring diagrams in the Standard Model
We study the symmetry breaking phenomenon in the standard model during the
electroweak phase transition in the presence of a constant hypermagnetic field.
We compute the finite temperature effective potential up to the contribution of
ring diagrams in the weak field, high temperature limit and show that under
these conditions, the phase transition becomes stronger first order.Comment: 15 pages, 8 Postscript figure
Electroweak Baryogenesis and New TeV Fermions
New fermions, strongly coupled to the Standard Model Higgs boson provide a
well motivated extension of the Standard Model (SM). In this work we show that,
once new physics at heavier scales is added to stabilize the Higgs potential,
such an extension of the SM can strengthen the first order electroweak phase
transition and make the electroweak baryogenesis mechanism feasible. We propose
a SM extension with TeV Higgsinos, Winos and Binos that satisfy the following
properties: a) The electroweak phase transition is strong enough to avoid
sphaleron erasure in the broken phase for values of the Higgs mass mH < 300
GeV; b) It provides large CP-violating currents that lead to the observed
baryon asymmetry of the Universe for natural values of the CP-violating phase;
c) It also provides a natural Dark Matter candidate that can reproduce the
observed dark matter density; d) It is consistent with electroweak precision
measurements; e) It may arise from a softly broken supersymmetric theory with
an extra (asymptotically free) gauge sector; e) It may be tested by electron
electric dipole moment experiments in the near future.Comment: LateX, 40 pages, 12 embedded postscript figures. A discussion of the
stability of the Higgs potential and its connection to a possible ultraviolet
completion of the model has been adde
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Comparison of preserved bimatoprost 0.01% with preservative-free tafluprost: A randomised, investigator-masked, 3-month crossover, multicentre trial, SPORT II
IMPORTANCE: This study compares the efficacy and tolerability of a preservative-free prostaglandin analogue (tafluprost 15 mg/ml) to a prostaglandin analogue that uses 0.02% of benzalkonium chloride (bimatoprost 0.1 mg/ml). BACKGROUND: Different prostaglandin analogues have been commercially approved, with differences in tolerability. DESIGN: Prospective, randomised, investigator-masked, 3-month crossover, multicentre trial. PARTICIPANTS: Sixty-four patients with ocular hypertension or open-angle glaucoma were randomised to two groups, after a 4-week washout period from their current topical drop regimen. METHODS: Participants were randomised to tafluprost (Group 1; n = 33) or bimatoprost (Group 2; n = 31). At month 3, each group switched to the opposite treatment. IOP was evaluated at multiple timepoints. MAIN OUTCOME MEASURES: The primary outcome was difference in mean IOP between the two groups at the final visit. Secondary outcomes included change from baseline IOP at month 3 and month 6, difference in mean IOP at month 3 and difference in IOP at all timepoints. Safety outcomes included best-corrected visual acuity (BCVA), adverse events, ocular tolerability, optic nerve assessment and slit lamp biomicroscopy. RESULTS: Both medications significantly lowered IOP at month 6 compared to baseline: 5.4 mmHg (27%) for tafluprost and 6.8 mmHg (33%) for bimatoprost (p < 0.0001). No significant differences in any of the safety measures (including conjunctival hypearemia) were detected. CONCLUSIONS AND RELEVANCE: Bimatoprost produced a statistically significant greater IOP reduction compared to tafluprost with minimal to no difference in side effects. This should be borne in mind when weighing up the pros and cons of preserved versus preservative-free prostaglandin analogue therapy
Fermion scattering off electroweak phase transition kink walls with hypermagnetic fields
We study the scattering of fermions off a finite width kink wall during the
electroweak phase transition in the presence of a background hypermagnetic
field. We derive and solve the Dirac equation for such fermions and compute the
reflection and transmission coefficients for the case when the fermions move
from the symmetric to the broken symmetry phase. We show that the chiral nature
of the fermion coupling with the background field in the symmetric phase
generates an axial asymmetry in the scattering processes. We discuss possible
implications of such axial charge segregation for baryon number generation.Comment: 9 pages, 3 Postscript figures, uses RevTeX4. Expanded discussion,
published versio
Supercooling and phase coexistence in cosmological phase transitions
Cosmological phase transitions are predicted by Particle Physics models, and
have a variety of important cosmological consequences, which depend strongly on
the dynamics of the transition. In this work we investigate in detail the
general features of the development of a first-order phase transition. We find
thermodynamical constraints on some quantities that determine the dynamics,
namely, the latent heat, the radiation energy density and the false-vacuum
energy density. Using a simple model with a Higgs field, we study numerically
the amount and duration of supercooling and the subsequent reheating and phase
coexistence. We analyze the dependence of the dynamics on the different
parameters of the model, namely, the energy scale, the number of degrees of
freedom and the couplings of the scalar field with bosons and fermions. We also
inspect the implications for the cosmological outcomes of the phase transition.Comment: 25 pages, 10 figures. References added and minor corrections. Version
to appear in Phys. Rev.
Black hole mergers: the first light
The coalescence of supermassive black hole binaries occurs via the emission
of gravitational waves, that can impart a substantial recoil to the merged
black hole. We consider the energy dissipation, that results if the recoiling
black hole is surrounded by a thin circumbinary disc. Our results differ
significantly from those of previous investigations. We show analytically that
the dominant source of energy is often potential energy, released as gas in the
outer disc attempts to circularize at smaller radii. Thus, dimensional
estimates, that include only the kinetic energy gained by the disc gas,
underestimate the real energy loss. This underestimate can exceed an order of
magnitude, if the recoil is directed close to the disc plane. We use three
dimensional Smooth Particle Hydrodynamics (SPH) simulations and two dimensional
finite difference simulations to verify our analytic estimates. We also compute
the bolometric light curve, which is found to vary strongly depending upon the
kick angle. A prompt emission signature due to this mechanism may be observable
for low mass (10^6 Solar mass) black holes whose recoil velocities exceed about
1000 km/s. Emission at earlier times can mainly result from the response of the
disc to the loss of mass, as the black holes merge. We derive analytically the
condition for this to happen.Comment: 16 pages, accepted by MNRAS. Animations of the simulations are
available at http://jilawww.colorado.edu/~pja/recoil.htm
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