5,059 research outputs found
Unitarity constraints on charged pion photoproduction at large p_perp
Around , the coupling to the channel
leads to a good accounting of the charged pion exclusive photoproduction cross
section in the energy range 3 10 GeV, where experimental data
exist. Starting from a Regge Pole approach that successfully describes vector
meson production, the singular part of the corresponding box diagrams (where
the intermediate vector meson-baryon pair propagates on-shell) is evaluated
without any further assumptions (unitarity). Such a treatment provides an
explanation of the scaling of the cross section. Elastic rescattering
of the charged pion improves the basic Regge pole model at forward and backward
angles.Comment: 5 pages; 6 figure
Consistency relation for the Lorentz invariant single-field inflation
In this paper we compute the sizes of equilateral and orthogonal shape
bispectrum for the general Lorentz invariant single-field inflation. The
stability of field theory implies a non-negative square of sound speed which
leads to a consistency relation between the sizes of orthogonal and equilateral
shape bispectrum, namely . In
particular, for the single-field Dirac-Born-Infeld (DBI) inflation, the
consistency relation becomes . These consistency relations are also valid in the
mixed scenario where the quantum fluctuations of some other light scalar fields
contribute to a part of total curvature perturbation on the super-horizon scale
and may generate a local form bispectrum. A distinguishing prediction of the
mixed scenario is . Comparing
these consistency relations to WMAP 7yr data, there is still a big room for the
Lorentz invariant inflation, but DBI inflation has been disfavored at more than
68% CL.Comment: 4 pages, 2 figures; v2: title changed, some mistakes corrected; v3:
refs added, version accepted for publication in JCA
Operadic formulation of topological vertex algebras and Gerstenhaber or Batalin-Vilkovisky algebras
We give the operadic formulation of (weak, strong) topological vertex
algebras, which are variants of topological vertex operator algebras studied
recently by Lian and Zuckerman. As an application, we obtain a conceptual and
geometric construction of the Batalin-Vilkovisky algebraic structure (or the
Gerstenhaber algebra structure) on the cohomology of a topological vertex
algebra (or of a weak topological vertex algebra) by combining this operadic
formulation with a theorem of Getzler (or of Cohen) which formulates
Batalin-Vilkovisky algebras (or Gerstenhaber algebras) in terms of the homology
of the framed little disk operad (or of the little disk operad).Comment: 42 page
R^2 Corrections for 5D Black Holes and Rings
We study higher-order corrections to two BPS solutions of 5D supergravity,
namely the supersymmetric black ring and the spinning black hole. Due in part
to our current relatively limited understanding of F-type terms in 5D
supergravity, the nature of these corrections is less clear than that of their
4D cousins. Effects of certain terms found in Calabi-Yau compactification
of M-theory are specifically considered. For the case of the black ring, for
which the microscopic origin of the entropy is generally known, the
corresponding higher order macroscopic correction to the entropy is found to
match a microscopic correction, while for the spinning black hole the
corrections are partially matched to those of a 4D black hole.Comment: 9 page
Running anti-de Sitter radius from QCD-like strings
We consider renormalization effects for a bosonic QCD-like string, whose
partons have propagators instead of Gaussian. Classically this model
resembles (the bosonic part of) the projective light-cone (zero-radius) limit
of a string on an AdS background, where Schwinger parameters give rise to
the fifth dimension. Quantum effects generate dynamics for this dimension,
producing an AdS background with a running radius. The projective
light-cone is the high-energy limit: Holography is enforced dynamically.Comment: 12 page
Thermal Giant Graviton with Non-commutative Dipole Field
Using the type II near-extremal 3D-branes solution we apply the T-duality and
smeared twist to construct the supergravity backgrounds which dual to the 4D
finite temperature non-commutative dipole field theories. We first consider the
zero-temperature system in which, depending on the property of dipole vectors
it may be N=2, N=1 or N=0 theory. We investigate the rotating D3-brane
configurations moving on the spactimes and show that, for the cases of N=2 and
N =1 the rotating D3-brane could be blowed up to the stable spherical
configuration which is called as giant graviton and has a less energy than the
point-like graviton. The giant graviton configuration is stable only if its
angular momentum was less than a critical value of which is an increasing
function of the dipole strength. For the case of non-supersymmetric theory,
however, the spherical configuration has a larger energy than the point-like
graviton. We also find that the dipole field always render the dual giant
graviton to be more stable than the point-like graviton. The relation of dual
giant graviton energy with its angular momentum, which in the AdS/CFT
correspondence being the operator anomalous dimension is obtained. We
furthermore show that the temperature does not change the property of the giant
graviton, while it will render the dual giant graviton to be unstable.Comment: Latex 20 pages, add comments about BPS bound below (3.8
Examples of M5-Brane Elliptic Genera
We determine the modified elliptic genus of an M5-brane wrapped on various
one modulus Calabi-Yau spaces, using modular invariance together with some
known Gopakumar-Vafa invariants of small degrees. As a bonus, we find
nontrivial relations among Gopakumar-Vafa invariants of different degrees and
genera from modular invariance.Comment: 13 page
Economics of robots and automation in field crop production
This study reviewed research published after 1990 on the economics of agricultural mechatronic automation and robotics, and identified research gaps. A systematic search was conducted from the following databases: ScienceDirect, Business Source Complete, Wiley, Emerald, CAB Abstract, Greenfile, Food Science Source and AgEcon Search. This identified 4817 documents. The screening of abstracts narrowed the range to a dataset of 119 full text documents. After eligibility assessment, 18 studies were subjected to a qualitative analysis, with ten focused on automation of specific horticultural operations and eight related to autonomous agricultural equipment. All of the studies found some scenarios in which automation and robotic technologies were profitable. Most studies employed partial budgeting considering only costs and revenues directly changed by the introduction of automation or robotics and assuming everything else constant. None examined cropping system changes, or regional and national impacts on markets, trade and labour demand. The review identified a need for in-depth research on the economic implications of the technology. Most of the studies reviewed estimated economic implications assuming that technology design parameters were achieved and/or based on data from prototypes. Data are needed on the benefits and problems with using automation and robotics on farm. All of the studies reviewed were in the context of agriculture in developed countries, but many of the world’s most pressing agricultural problems are in the developing world. Economic and social research is needed to understand those developing country problems, and guide the engineers and scientists creating automation and robotic solutions
Heavy-to-light transition form factors and their relations in light-cone QCD sum rules
The improved light-cone QCD sum rules by using chiral current correlator is
systematically reviewed and applied to the calculation of all the
heavy-to-light form factors, including all the semileptonic and penguin ones.
By choosing suitable chiral currents, the light-cone sum rules for all the form
factors are greatly simplified and depend mainly on one leading twist
distribution amplitude of the light meson. As a result, relations between these
form factors arise naturally. At the considered accuracy these relations
reproduce the results obtained in the literature. Moreover, since the explicit
dependence on the leading twist distribution amplitudes is preserved, these
relations may be more useful to simulate the experimental data and extract the
information on the distribution amplitude.Comment: 1+16 pages, no figure
Comparison of SIVmac239(352–382) and SIVsmmPBj41(360–390) enterotoxic synthetic peptides
AbstractTo characterize the active domain of the simian immunodeficiency virus (SIV) surface unit (SU) enterotoxin, peptides corresponding to the V3 loop of SIVmac239 (SIVmac) and SIVsmmPBj41 (SIVpbj) were synthesized and examined for enterotoxic activity, α-helical structure, and interaction(s) with model membranes. SIVmac and SIVpbj induced a dose-dependent diarrhea in 6–8-day-old mouse pups similar to full-length SU. The peptides mobilized [Ca2+]i in HT-29 cells with distinct oscillations and elevated inositol triphosphate levels. Circular dichroism analyses showed the peptides were predominantly random coil in buffer, but increased in α-helical content when placed in a hydrophobic environment or with cholesterol-containing membrane vesicles that are rich in anionic phospholipids. None of the peptides underwent significant secondary structural changes in the presence of neutral vesicles indicating ionic interactions were important. These data show that the SIV SU enterotoxic domain localizes in part to the V3 loop region and interacts with anionic membrane domains on the host cell surface
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