40 research outputs found
Resummation of QCD Corrections to the eta_c Decay Rate
We examine the ratio of the decay rate of the eta_c into light hadrons to the
decay rate into photons and find that most of the large next-to-leading-order
(NLO) correction is associated with running of the strong coupling alpha_s. We
resum such contributions by analyzing final-state chains of vacuum-polarization
bubbles. We show that the nonperturbative parts of the bubble chains can be
absorbed into a color-octet matrix element, once one has used contour
deformations of the phase-space integrals to cancel certain contributions. We
argue that these contributions are incompatible with the uncertainty principle.
We also argue that perturbation theory is reliable only if one carries out the
phase-space integrations before the perturbation summation. Our results are in
good agreement with experiment and differ considerably from those that one
obtains by applying the scale-setting method of Brodsky, Lepage, and Mackenzie
to the NLO result.Comment: 41 pages, REVTEX, corrected minor typos in tex
Partition functions and double-trace deformations in AdS/CFT
We study the effect of a relevant double-trace deformation on the partition
function (and conformal anomaly) of a CFT at large N and its dual picture in
AdS. Three complementary previous results are brought into full agreement with
each other: bulk and boundary computations, as well as their formal identity.
We show the exact equality between the dimensionally regularized partition
functions or, equivalently, fluctuational determinants involved. A series of
results then follows: (i) equality between the renormalized partition functions
for all d; (ii) for all even d, correction to the conformal anomaly; (iii) for
even d, the mapping entails a mixing of UV and IR effects on the same side
(bulk) of the duality, with no precedent in the leading order computations; and
finally, (iv) a subtle relation between overall coefficients, volume
renormalization and IR-UV connection. All in all, we get a clean test of the
AdS/CFT correspondence beyond the classical SUGRA approximation in the bulk and
at subleading O(1) order in the large-N expansion on the boundary.Comment: 18 pages, uses JHEP3.cls. Published JHEP versio
Propagators and WKB-exactness in the plane wave limit of AdSxS
Green functions for the scalar, spinor and vector fields in a plane wave
geometry arising as a Penrose limit of are obtained. The
Schwinger-DeWitt technique directly gives the results in the plane wave
background, which turns out to be WKB-exact. Therefore the structural
similarity with flat space results is unveiled. In addition, based on the local
character of the Penrose limit, it is claimed that for getting the correct
propagators in the limit one can rely on the first terms of the direct geodesic
contribution in the Schwinger-DeWitt expansion of the original propagators .
This is explicitly shown for the Einstein Static Universe, which has the same
Penrose limit as with equal radii, and for a number of other
illustrative cases.Comment: 18 pages, late
Ghost D-branes
We define a ghost D-brane in superstring theories as an object that cancels
the effects of an ordinary D-brane. The supergroups U(N|M) and OSp(N|M) arise
as gauge symmetries in the supersymmetric world-volume theory of D-branes and
ghost D-branes. A system with a pair of D-brane and ghost D-brane located at
the same location is physically equivalent to the closed string vacuum. When
they are separated, the system becomes a new brane configuration. We generalize
the type I/heterotic duality by including n ghost D9-branes on the type I side
and by considering the heterotic string whose gauge group is OSp(32+2n|2n).
Motivated by the type IIB S-duality applied to D9- and ghost D9-branes, we also
find type II-like closed superstrings with U(n|n) gauge symmetry.Comment: 49 pages, 6 figures, harvmac. v2: references and acknowledgements
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North Tropical Atlantic influence on western Amazon fire season variability
The prevailing wet climate in the western Amazon is not favorable to the natural occurrence of fires. Nevertheless, the current process of clearing of humid forests for agriculture and cattle ranching has increased the vulnerability of the region to the spread of fires. Using meteorological stations precipitation and the Moderate Resolution Spectroradiometer (MODIS) Active-Fires (AF) during 2000-2009, we show that fire anomalies vary closely with July-August-September (JAS) precipitation variability as measured by the Standardized Precipitation Index (SPI). The precipitation variability is, in turn, greatly determined by sea surface temperature (SST) anomalies in the North Tropical Atlantic (NTA). We develop a linear regression model to relate local fire activity to an index of the NTA-SST. By using seasonal forecasts of SST from a coupled model, we are able to predict anomalous JAS fire activity as early as April. We applied the method to predict the severe 2010 JAS season, which indicated strongly positive seasonal fire anomalies within the 95% prediction confidence intervals in most western Amazon. The spatial distribution of predicted SPI was also in accordance with observed precipitation anomalies. This three months lead time precipitation and fire prediction product in the western Amazon could help local decision makers to establish an early warning systems or other appropriate course of action before the fire season begins
Radiative Scalar Meson Decays in the Light-Front Quark Model
We construct a relativistic wavefunction for scalar mesons within the
framework of light-front quark model(LFQM). This scalar wavefunction is used to
perform relativistic calculations of absolute widths for the radiative decay
processes, and
which incorporate the effects of glueball-
mixing. The mixed physical states are assumed to be ,and
for which the flavor-glue content is taken from the mixing
calculations of other works. Since experimental data for these processes are
poor, our results are compared with those of a recent non-relativistic model
calculation. We find that while the relativistic corrections introduced by the
LFQM reduce the magnitudes of the decay widths by 50-70%, the relative
strengths between different decay processes are fairly well preserved. We also
calculate decay widths for the processes and
(0^{++})\to\gamma\gamm involving the light scalars and
to test the simple model of these mesons. Our results of
model for these processes are not quite consistent with well-established data,
further supporting the idea that and are not conventional
states.Comment: 10 pages, 4 figure
Quantum gravity from the point of view of locally covariant quantum field theory
We construct perturbative quantum gravity in a generally covariant way. In particular our construction is background independent. It is based on the locally covariant approach to quantum field theory and the renormalized Batalin-Vilkovisky formalism. We do not touch the problem of nonrenormalizability and interpret the theory as an effective theory at large length scales
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Metallic mineral districts of Arizona - Map 18
Map detailing the distribution of metallic mineral districts in Arizona. 1:1,000,000. Color-coded by commodity and setting.Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact [email protected])
Recommended from our members
Metallic mineral districts of Arizona - Map 18
Map detailing the distribution of metallic mineral districts in Arizona. 1:1,000,000. Color-coded by commodity and setting.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact [email protected]