206 research outputs found
Topological Defects in Gauge Theories of Open p-branes
We study phase transitions induced by topological defects in Abelian gauge
theories of open p-branes in (d+1) space-time dimensions. Starting from a
massive antisymmetric tensor theory for open p-branes we show how the
condensation of topological defects can lead to a decoupled phase with a
massless tensor coupled to closed (p-1)-branes and a massive tensor coupled to
open (p+1)-branes. We also consider the case, relevant in string theory, in
which the boundaries of the p-branes are constrained to live on a Dirichlet
n-branes.Comment: 16 pages, harvmac te
Solar Neutrino Rates, Spectrum, and its Moments : an MSW Analysis in the Light of Super-Kamiokande Results
We re-examine MSW solutions of the solar neutrino problem in a two flavor
scenario taking (a) the results on total rates and the electron energy spectrum
from the 1117-day SuperKamiokande (SK) data and (b) those on total rates from
the Chlorine and Gallium experiments. We find that the SMA solution gives the
best fit to the total rates data from the different experiments. One new
feature of our analysis is the use of the moments of the SK electron spectrum
in a analysis. The best-fit to the moments is broadly in agreement
with that obtained from a direct fit to the spectrum data and prefers a comparable to the SMA fit to the rates but the required mixing angle is
larger. In the combined rate and spectrum analysis, apart from varying the
normalization of the B flux as a free parameter and determining its
best-fit value we also obtain the best-fit parameters when correlations between
the rates and the spectrum data are included and the normalization of the B
flux held fixed at its SSM value. We observe that the correlations between the
rates and spectrum data are important and the goodness of fit worsens when
these are included. In either case, the best-fit lies in the LMA region.Comment: 17 pages, 4 figure
Gravitational Wave Spectrum in Inflation with Nonclassical States
The initial quantum state during inflation may evolve to a highly squeezed
quantum state due to the amplification of the time-dependent parameter,
, which may be the modified dispersion relation in
trans-Planckian physics. This squeezed quantum state is a nonclassical state
that has no counterpart in the classical theory. We have considered the
nonclassical states such as squeezed, squeezed coherent, and squeezed thermal
states, and calculated the power spectrum of the gravitational wave
perturbation when the mode leaves the horizon.Comment: 21 page
Non-minimally Coupled Tachyonic Inflation in Warped String Background
We show that the non-minimal coupling of tachyon field to the scalar
curvature, as proposed by Piao et al, with the chosen coupling parameter does
not produce the effective potential where the tachyon field can roll down from
T=0 to large along the slope of the potential. We find a correct choice of
the parameters which ensures this requirement and support slow-roll inflation.
However, we find that the cosmological parameter found from the analysis of the
theory are not in the range obtained from observations. We then invoke warped
compactification and varying dilaton field over the compact manifold, as
proposed by Raeymaekers, to show that in such a setup the observed parameter
space can be ensured.Comment: minor typos corrected and references adde
Self Duality and Oblique Confinement in Planar Gauge Theories
We investigate the non-perturbative structure of two planar
lattice gauge models and discuss their relevance to two-dimensional condensed
matter systems and Josephson junction arrays. Both models involve two compact
U(1) gauge fields with Chern-Simons interactions, which break the symmetry down
to . By identifying the relevant topological excitations
(instantons) and their interactions we determine the phase structure of the
models. Our results match observed quantum phase transitions in Josephson
junction arrays and suggest also the possibility of {\it oblique confining
ground states} corresponding to quantum Hall regimes for either charges or
vortices.Comment: 32 pages, harvma
How does Inflation Depend Upon the Nature of Fluids Filling Up the Universe in Brane World Scenario
By constructing different parameters which are able to give us the
information about our universe during inflation,(specially at the start and the
end of the inflationary universe) a brief idea of brane world inflation is
given in this work. What will be the size of the universe at the end of
inflation,i.e.,how many times will it grow than today's size is been speculated
and analysed thereafter. Different kinds of fluids are taken to be the matter
inside the brane. It is observed that in the case of highly positive pressure
grower gas like polytropic,the size of the universe at the end of inflation is
comparitively smaller. Whereas for negative pressure creators (like chaplygin
gas) this size is much bigger. Except thse two cases, inflation has been
studied for barotropic fluid and linear redshift parametrization too. For them the size of the universe after
inflation is much more high. We also have seen that this size does not depend
upon the potential energy at the end of the inflation. On the contrary, there
is a high impact of the initial potential energy upon the size of inflation.Comment: 20 page
Realistic Equations of State for the Primeval Universe
Early universe equations of state including realistic interactions between
constituents are built up. Under certain reasonable assumptions, these
equations are able to generate an inflationary regime prior to the
nucleosynthesis period. The resulting accelerated expansion is intense enough
to solve the flatness and horizon problems. In the cases of curvature parameter
\kappa equal to 0 or +1, the model is able to avoid the initial singularity and
offers a natural explanation for why the universe is in expansion.Comment: 32 pages, 5 figures. Citations added in this version. Accepted EPJ
D-brane anti-D-brane effective action and brane interaction in open string channel
We construct the effective action of a -brane-anti--brane system by
making use of the non-abelian extension of tachyonic DBI action. We succeed the
construction by restricting the Chan-Paton factors of two non-BPS -branes
in the action to the Chan-Paton factors of a system. For the
special case that both branes are coincident, the action reduces to the one
proposed by A. Sen. \\The effective potential indicates that
when branes separation is larger than the string length scale, there are two
minima in the tachyon direction. As branes move toward each other under the
gravitational force, the tachyon tunneling from false to true vacuum may make a
bubble formation followed by a classical evolution of the bubble. On the other
hand, when branes separation is smaller than the string length scale, the
potential shows one maximum and one minimum. In this case, a homogeneous
tachyon rolling in real time makes an attractive potential for the branes
distance. This classical force is speculated to be the effective force between
the two branes.Comment: Latex, 14 pages, 1 figure, the version appears in JHE
Anisotropic cosmological models with a perfect fluid and a term
We consider a self-consistent system of Bianchi type-I (BI) gravitational
field and a binary mixture of perfect fluid and dark energy given by a
cosmological constant. The perfect fluid is chosen to be the one obeying either
the usual equation of state, i.e., p = \zeta \ve, with or
a van der Waals equation of state. Role of the term in the evolution
of the BI Universe has been studied.Comment: 8 pages, 8 Figure
Highlights from the International Chronic Thromboembolic Pulmonary Hypertension Congress 2021
Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism. It is caused by persistent obstruction of pulmonary arteries by chronic organised fibrotic clots, despite adequate anticoagulation. The pulmonary hypertension is also caused by concomitant microvasculopathy which may progress without timely treatment. Timely and accurate diagnosis requires the combination of imaging and haemodynamic assessment. Optimal therapy should be individualised to each case and determined by an experienced multidisciplinary CTEPH team with the ability to offer all current treatment modalities. This report summarises current knowledge and presents key messages from the International CTEPH Conference, Bad Nauheim, Germany, 2021. Sessions were dedicated to 1) disease definition; 2) pathophysiology, including the impact of the hypertrophied bronchial circulation, right ventricle (dys)function, genetics and inflammation; 3) diagnosis, early after acute pulmonary embolism, using computed tomography and perfusion techniques, and supporting the selection of appropriate therapies; 4) surgical treatment, pulmonary endarterectomy for proximal and distal disease, and peri-operative management; 5) percutaneous approach or balloon pulmonary angioplasty, techniques and complications; and 6) medical treatment, including anticoagulation and pulmonary hypertension drugs, and in combination with interventional treatments. Chronic thromboembolic pulmonary disease without pulmonary hypertension is also discussed in terms of its diagnostic and therapeutic aspects. Thrombosis and Hemostasi
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