30 research outputs found
Quantum Horizons of the Standard Model Landscape
The long-distance effective field theory of our Universe--the Standard Model
coupled to gravity--has a unique 4D vacuum, but we show that it also has a
landscape of lower-dimensional vacua, with the potential for moduli arising
from vacuum and Casimir energies. For minimal Majorana neutrino masses, we find
a near-continuous infinity of AdS3xS1 vacua, with circumference ~20 microns and
AdS3 length 4x10^25 m. By AdS/CFT, there is a CFT2 of central charge c~10^90
which contains the Standard Model (and beyond) coupled to quantum gravity in
this vacuum. Physics in these vacua is the same as in ours for energies between
10^-1 eV and 10^48 GeV, so this CFT2 also describes all the physics of our
vacuum in this energy range. We show that it is possible to realize
quantum-stabilized AdS vacua as near-horizon regions of new kinds of quantum
extremal black objects in the higher-dimensional space--near critical black
strings in 4D, near-critical black holes in 3D. The violation of the
null-energy condition by the Casimir energy is crucial for these horizons to
exist, as has already been realized for analogous non-extremal 3D black holes
by Emparan, Fabbri and Kaloper. The new extremal 3D black holes are
particularly interesting--they are (meta)stable with an entropy independent of
hbar and G_N, so a microscopic counting of the entropy may be possible in the
G_N->0 limit. Our results suggest that it should be possible to realize the
larger landscape of AdS vacua in string theory as near-horizon geometries of
new extremal black brane solutions.Comment: 44 pages, 9 figure
Lepton polarization asymmetry and forward backward asymmetry in exclusive B->K_1 tau^(+)tau^(-) decay in universal extra dimension scenario
Decay rate, forward-backward asymmetry and polarization asymmetries of final
state leptons in B-> K_{1}tau ^{+}tau ^{-}, where K_{1} is the axial vector
meson, are calculated in Standard Model and in the universal extra dimension
(UED) model. The sensitivity of the observables on the compactification radius
, the only unknown paramter in UED model, is studied. Finally, the helicity
fractions of the final state K_{1} are calculated and their dependence on the
compactification radius is discussed. This analysis of helicity fraction is
briefly extended to B->K^{*}l ^{+}l ^{-}(l =e,mu) and compared with the other
approaches exist in the literatureComment: 19 pages, 6 figure
The Superconductivity, Intragrain Penetration Depth and Meissner Effect of RuSr2(Gd,Ce)2Cu2O10+delta
The hole concentration (p)(delta), the transition temperature Tc, the
intragrain penetration depth lambda, and the Meissner effect were measured for
annealed RuSr2(Gd,Ce)2Cu2O10+delta samples. The intragrain superconducting
transition temperature Tc} varied from 17 to 40 K while the p changed by only
0.03 holes/CuO2. The intragrain superfluid-density 1/lambda^2 and the
diamagnetic drop of the field-cooled magnetization across Tc (the Meissner
effect), however, increased more than 10 times. All of these findings are in
disagreement with both the Tc vs. p and the Tc vs. 1/lambda^2 correlations
proposed for homogeneous cuprates, but are in line with a possible
phase-separation and the granularity associated with it.Comment: 7 pages, 6 figures, accepted for publication in Phys. Rev. B (May 2,
2002
A Brane World Perspective on the Cosmological Constant and the Hierarchy Problems
We elaborate on the recently proposed static brane world scenario, where the
effective 4-D cosmological constant is exponentially small when parallel
3-branes are far apart. We extend this result to a compactified model with two
positive tension branes. Besides an exponentially small effective 4-D
cosmological constant, this model incorporates a Randall-Sundrum-like solution
to the hierarchy problem. Furthermore, the exponential factors for the
hierarchy problem and the cosmological constant problem obey an inequality that
is satisfied in nature. This inequality implies that the cosmological constant
problem can be explained if the hierarchy problem is understood. The basic idea
generalizes to the multibrane world scenario. We discuss models with piecewise
adjustable bulk cosmological constants (to be determined by the 5-dimensional
Einstein equation), a key element of the scenario. We also discuss the global
structure of this scenario and clarify the physical properties of the particle
(Rindler) horizons that are present. Finally, we derive a 4-D effective theory
in which all observers on all branes not separated by particle horizons measure
the same Newton's constant and 4-D cosmological constant.Comment: revtex, 63 pages, 8 figures, one table, revised version, more
discussions on the global structure, references adde
Quantum Black Holes as Holograms in AdS Braneworlds
We propose a new approach for using the AdS/CFT correspondence to study
quantum black hole physics. The black holes on a brane in an AdS
braneworld that solve the classical bulk equations are interpreted as duals of
{\it quantum-corrected} -dimensional black holes, rather than classical
ones, of a conformal field theory coupled to gravity. We check this explicitly
in D=3 and D=4. In D=3 we reinterpret the existing exact solutions on a flat
membrane as states of the dual 2+1 CFT. We show that states with a sufficiently
large mass really are 2+1 black holes where the quantum corrections dress the
classical conical singularity with a horizon and censor it from the outside. On
a negatively curved membrane, we reinterpret the classical bulk solutions as
quantum-corrected BTZ black holes. In D=4 we argue that the bulk solution for
the brane black hole should include a radiation component in order to describe
a quantum-corrected black hole in the 3+1 dual. Hawking radiation of the
conformal field is then dual to classical gravitational bremsstrahlung in the
AdS bulk.Comment: 28 pages, JHEP latex, 1 .eps figure, v2: references and comments
added, v3: comments and acknowledgements added to match the published pape
The Dynamics of Brane-World Cosmological Models
Brane-world cosmology is motivated by recent developments in string/M-theory
and offers a new perspective on the hierarchy problem. In the brane-world
scenario, our Universe is a four-dimensional subspace or {\em brane} embedded
in a higher-dimensional {\em bulk} spacetime. Ordinary matter fields are
confined to the brane while the gravitational field can also propagate in the
bulk, leading to modifications of Einstein's theory of general relativity at
high energies. In particular, the Randall-Sundrum-type models are
self-consistent and simple and allow for an investigation of the essential
non-linear gravitational dynamics. The governing field equations induced on the
brane differ from the general relativistic equations in that there are nonlocal
effects from the free gravitational field in the bulk, transmitted via the
projection of the bulk Weyl tensor, and the local quadratic energy-momentum
corrections, which are significant in the high-energy regime close to the
initial singularity. In this review we discuss the asymptotic dynamical
evolution of spatially homogeneous brane-world cosmological models containing
both a perfect fluid and a scalar field close to the initial singularity. Using
dynamical systems techniques it is found that, for models with a physically
relevant equation of state, an isotropic singularity is a past-attractor in all
orthogonal spatially homogeneous models (including Bianchi type IX models). In
addition, we describe the dynamics in a class of inhomogeneous brane-world
models, and show that these models also have an isotropic initial singularity.
These results provide support for the conjecture that typically the initial
cosmological singularity is isotropic in brane-world cosmology.Comment: Einstein Centennial Review Article: to appear in CJ
Perspective Chapter: The Toxic Silver (Hg)
In the late 1950s, residents of a Japanese fishing village known as âMinamataâ began falling ill and dying at an alarming rate. The Japanese authorities stated that methyl-mercury-rich seafood and shellfish caused the sickness. Burning fossil fuels represent â52.7% of Hg emissions. The majorities of mercuryâs compounds are volatile and thus travel hundreds of miles with wind before being deposited on the earthâs surface. High acidity and dissolved organic carbon increase Hg-mobility in soil to enter the food chain. Additionally, Hg is taken up by areal plant parts via gas exchange. Mercury has no identified role in plants while exhibiting high affinity to form complexes with soft ligands such as sulfur and this consequently inactivates amino acids and sulfur-containing antioxidants. Long-term human exposure to Hg leads to neurotoxicity in children and adults, immunological, cardiac, and motor reproductive and genetic disorders. Accordingly, remediating contaminated soils has become an obligation. Mercury, like other potentially toxic elements, is not biodegradable, and therefore, its remediation should encompass either removal of Hg from soils or even its immobilization. This chapter discusses Hgâs chemical behavior, sources, health dangers, and soil remediation methods to lower Hg levels
Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt [ s ] = 13TeV
A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fbâ1 of protonâproton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at âs = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions
Search for high-mass new phenomena in the dilepton final state using protonâproton collisions at View the MathML sources=13TeV with the ATLAS detector
A search is conducted for both resonant and non-resonant high-mass new phenomena in dielectron and dimuon final states. The search uses View the MathML source3.2fbâ1 of protonâproton collision data, collected at View the MathML sources=13TeV by the ATLAS experiment at the LHC in 2015. The dilepton invariant mass is used as the discriminating variable. No significant deviation from the Standard Model prediction is observed; therefore limits are set on the signal model parameters of interest at 95% credibility level. Upper limits are set on the cross-section times branching ratio for resonances decaying to dileptons, and the limits are converted into lower limits on the resonance mass, ranging between 2.74 TeV and 3.36 TeV, depending on the model. Lower limits on the ââqqââqq contact interaction scale are set between 16.7 TeV and 25.2 TeV, also depending on the mode