94 research outputs found
Compactification of IIB Theory with Fluxes and Axion-Dilaton String Cosmology
Compactification of type IIB theory on torus, in the presence of fluxes, is
considered. The reduced effective action is expressed in manifestly S-duality
invariant form. Cosmological solutions of the model are discussed in several
cases in the Pre-Big Bang scenario.Comment: 22 page
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Projected changes in heatwaves and its impact on human discomfort over India due to global warming under the CORDEX-CORE framework
Due to climate change, rapid warming and its further intensification over different parts of the globe have been recently reported. This has a direct impact on human health, agriculture, water availability, power generation, various ecosystems, and socioeconomic conditions of the exposed population. The current study thus investigates the frequency and duration of heatwaves, human discomfort, and exposure of the human population to these extremes using the high-resolution regional climate model experiments under two Representative Concentration Pathways (RCP2.6, RCP8.5) over India. We find that more than 90% of India will be exposed to uncomfortable warm nights by the end of the 21st century with the highest rise over western India, Madhya Pradesh (MP), Uttar Pradesh (UP), Punjab, and the Haryana region. States like Odisha, Chhattisgarh, eastern parts of MP and UP, and some parts of J&K will be the worst hit by the intense and frequent heatwaves and human discomfort followed by the densely populated Indo-Gangetic plains under RCP8.5. Strict enforcement of the stringent policies on stabilization of population growth, improvement of local adaptive capacities, and economic status of the vulnerable population along with enforcing effective measures to curb greenhouse gas emissions are important to reduce human exposure to future heat stress. We demonstrate that a proper mitigation-based development (RCP2.6) instead of a business-as-usual scenario (RCP8.5) may help to reduce 50–200 heatwave days, 3–10 heatwave spells, and 10–35% warm nights over the Indian region. Consequently, this can avoid the exposure of 135–143 million population to severe discomfort due to extreme heat conditions by the end of the 21st century
On the Rotating Charged Black String Solution
A rotating charged black string solution in the low energy effective field
theory describing five dimensional heterotic string theory is constructed. The
solution is labelled by mass, electric charge, axion charge and angular
momentum per unit length. The extremal limit of this solution is also studied.Comment: 12 pages, IMSC-93/6,(Phyzzx macro), January 199
U-Duality and Symplectic Formulation of Dilaton-Axion Gravity
We study a bosonic four--dimensional effective action corresponding to the
heterotic string compactified on a 6--torus (dilaton--axion gravity with one
vector field) on a curved space--time manifold possessing a time--like Killing
vector field. Previously an existence of the global
symmetry (--duality) as well as the symmetric space property of the
corresponding --model have been established following Neugebauer and
Kramer approach. Here we present an explicit form of the generators
in terms of coset variables and construct a representation of the coset in
terms of the physical target space coordinates. Complex symmetric
matrix (``matrix dilaton --axion'') is introduced for which --duality
takes the matrix valued form. In terms of this matrix the theory is
further presented as a K\"ahler --model. This leads to a more concise
formulation which opens new ways to construct exact classical
solutions. New solution (corresponding to constant ) is obtained
which describes the system of point massless magnetic monopoles endowed with
axion charges equal to minus monopole charges. In such a system mutual magnetic
repulsion is exactly balanced by axion attraction so that the resulting space
time is locally flat but possesses multiple Taub--NUT singularities.Comment: LATEX, 20 pages, no figure
On Some New Black String Solutions in Three Dimensions
We derive several new solutions in three-dimensional stringy gravity. The
solutions are obtained with the help of string duality transformations. They
represent stationary configurations with horizons, and are surrounded by
(quasi) topologically massive Abelian gauge hair, in addition to the dilaton
and the Kalb-Ramond axion. Our analysis suggests that there exists a more
general family, where our solutions are special limits. Finally, we use the
generating technique recently proposed by Garfinkle to construct a traveling
wave on the extremal variant of one of our solutions.Comment: revtex, 38 pages including 3 figure
New Constraints (and Motivations) for Abelian Gauge Bosons in the MeV-TeV Mass Range
We survey the phenomenological constraints on abelian gauge bosons having
masses in the MeV to multi-GeV mass range (using precision electroweak
measurements, neutrino-electron and neutrino-nucleon scattering, electron and
muon anomalous magnetic moments, upsilon decay, beam dump experiments, atomic
parity violation, low-energy neutron scattering and primordial
nucleosynthesis). We compute their implications for the three parameters that
in general describe the low-energy properties of such bosons: their mass and
their two possible types of dimensionless couplings (direct couplings to
ordinary fermions and kinetic mixing with Standard Model hypercharge). We argue
that gauge bosons with very small couplings to ordinary fermions in this mass
range are natural in string compactifications and are likely to be generic in
theories for which the gravity scale is systematically smaller than the Planck
mass - such as in extra-dimensional models - because of the necessity to
suppress proton decay. Furthermore, because its couplings are weak, in the
low-energy theory relevant to experiments at and below TeV scales the charge
gauged by the new boson can appear to be broken, both by classical effects and
by anomalies. In particular, if the new gauge charge appears to be anomalous,
anomaly cancellation does not also require the introduction of new light
fermions in the low-energy theory. Furthermore, the charge can appear to be
conserved in the low-energy theory, despite the corresponding gauge boson
having a mass. Our results reduce to those of other authors in the special
cases where there is no kinetic mixing or there is no direct coupling to
ordinary fermions, such as for recently proposed dark-matter scenarios.Comment: 49 pages + appendix, 21 figures. This is the final version which
appears in JHE
Gauged WZW models and Non-abelian duality
We consider WZW models based on the non-semi-simple algebras that they were
recently constructed as contractions of corresponding algebras for semi-simple
groups. We give the explicit expression for the action of these models, as well
as for a generalization of them, and discuss their general properties.
Furthermore we consider gauged WZW models based on these non-semi-simple
algebras and we show that there are equivalent to non-abelian duality
transformations on WZW actions. We also show that a general non-abelian duality
transformation can be thought of as a limiting case of the non-abelian quotient
theory of the direct product of the original action and the WZW action for the
symmetry gauge group . In this action there is no Lagrange multiplier term
that constrains the gauge field strength to vanish. A particular result is that
the gauged WZW action for the coset is equivalent,
in the limit , to the dualized WZW action for with respect
to the subgroup .Comment: 35 pages, harvmac, THU-94/01 (a few minor changes in subsec. 4.1 are
made, a 3rd App. and a Note are added
Branes, U-folds and hyperelliptic fibrations
We construct a class of supersymmetric vacua of type IIB string theory
describing systems of three- and seven-branes non-perturbatively completed by
brane instantons. The vacua are specified by a set of holomorphic functions
defined over a complex plane up to non-trivial U-duality monodromies around the
brane locations. In the simplest setting, the solutions can be seen as a
generalization of F-theory elliptic fibrations, where the torus fiber is
replaced by a genus two Riemann surface with periods encoding the information
on the axio-dilaton, the warp factor and the NS-NS and R-R fluxes.Comment: 49 pages, including 22 pages of Appendix, 2 figures. Minor change
A ten-dimensional action for non-geometric fluxes
The NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change
of field variables inspired by Generalized Complex Geometry. We obtain a new
metric and dilaton, together with an antisymmetric bivector field which leads
to a ten-dimensional version of the non-geometric Q-flux. Given the involved
global aspects of non-geometric situations, we prescribe to use this new
Lagrangian, whose associated action is well-defined in some examples
investigated here. This allows us to perform a standard dimensional reduction
and to recover the usual contribution of the Q-flux to the four-dimensional
scalar potential. An extension of this work to include the R-flux is discussed.
The paper also contains a brief review on non-geometry.Comment: 47 pages; v2: minor modifications, references added, version to be
published in JHE
Precise measurement of the lifetime at Belle II
We measure the lifetime of the meson using a data sample of 207
fb collected by the Belle II experiment running at the SuperKEKB
asymmetric-energy collider. The lifetime is determined by fitting the
decay-time distribution of a sample of
decays. Our result is \tau^{}_{D^+_s} = (498.7\pm
1.7\,^{+1.1}_{-0.8}) fs, where the first uncertainty is statistical and the
second is systematic. This result is significantly more precise than previous
measurements.Comment: 7 pages, 4 figures, to be submitted to Physical Review Letter
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