19,556 research outputs found
Generalized -conformal change and special Finsler spaces
In this paper, we investigate the change of Finslr metrics which we refer to as a
generalized -conformal change. Under this change, we study some special
Finsler spaces, namely, quasi C-reducible, semi C-reducible, C-reducible,
-like, -like and -like Finsler spaces. We also obtain the
transformation of the T-tensor under this change and study some interesting
special cases. We then impose a certain condition on the generalized
-conformal change, which we call the b-condition, and investigate the
geometric consequences of such condition. Finally, we give the conditions under
which a generalized -conformal change is projective and generalize some
known results in the literature.Comment: References added, some modifications are performed, LateX file, 24
page
DIRBE Minus 2MASS: Confirming the CIRB in 40 New Regions at 2.2 and 3.5 Microns
With the release of the 2MASS All-Sky Point Source Catalog, stellar fluxes
from 2MASS are used to remove the contribution due to Galactic stars from the
intensity measured by DIRBE in 40 new regions in the North and South Galactic
polar caps. After subtracting the interplanetary and Galactic foregrounds, a
consistent residual intensity of 14.69 +/- 4.49 kJy/sr at 2.2 microns is found.
Allowing for a constant calibration factor between the DIRBE 3.5 microns and
the 2MASS 2.2 microns fluxes, a similar analysis leaves a residual intensity of
15.62 +/- 3.34 kJy/sr at 3.5 microns. The intercepts of the DIRBE minus 2MASS
correlation at 1.25 microns show more scatter and are a smaller fraction of the
foreground, leading to a still weak limit on the CIRB of 8.88 +/- 6.26 kJy/sr
(1 sigma).Comment: 25 pages LaTeX, 10 figures, 5 tables; Version accepted by the ApJ.
Includes minor changes to the text including further discussion of zodiacal
light issues and the allowance for variable stars in computing uncertainties
in the stellar contribution to the DIRBE intensitie
Explosive Dark Matter Annihilation
If the Dark Matter (DM) in the Universe has interactions with the
standard-model particle, the pair annihilation may give the imprints in the
cosmic ray. In this paper we study the pair annihilation processes of the DM,
which is neutral, however has the electroweak (EW) gauge non-singlet. In this
estimation the non-relativistic (NR) effective theory in the EW sector is a
suitable technique. We find that if the DM mass is larger than about 1 TeV, the
attractive Yukawa potentials induced by the EW gauge bosons have significant
effects on the DM annihilation processes, and the cross sections may be
enhanced by several orders of magnitude, due to the zero energy resonance under
the potentials. Especially, the annihilation to two 's might have a
comparable cross section to other tree-level processes, while the cross section
under the conventional calculation is suppressed by a loop factor. We also
discuss future sensitivities to the ray from the galactic center by
the GLAST satellite detector and the Air Cerenkov Telescope (ACT) arrays.Comment: 5 pages, 6 Postscript figures, revte
XatA, an AT-1 autotransporter important for the virulence of Xylella fastidiosa Temecula1.
Xylella fastidiosa Temecula1 is the causative agent of Pierce's disease of grapevine, which is spread by xylem-feeding insects. An important feature of the infection cycle is the ability of X. fastidiosa to colonize and interact with two distinct environments, the xylem of susceptible plants and the insect foregut. Here, we describe our characterization of XatA, the X. fastidiosa autotransporter protein encoded by PD0528. XatA, which is classified as an AT-1 (classical) autotransporter, has a C-terminal β-barrel domain and a passenger domain composed of six tandem repeats of approximately 50 amino acids. Localization studies indicate that XatA is present in both the outer membrane and membrane vesicles and its passenger domain can be found in the supernatant. Moreover, XatA is important for X. fastidiosa autoaggregation and biofilm formation based on mutational analysis and the discovery that Escherichia coli expressing XatA acquire these traits. The xatA mutant also shows a significant decrease in Pierce's disease symptoms when inoculated into grapevines. Finally, X. fastidiosa homologs to XatA, which can be divided into three distinct groups based on synteny, form a single, well-supported clade, suggesting that they arose from a common ancestor
Two-Dimensional Order and Disorder Thermofields
The main objective of this paper was to obtain the two-dimensional order and
disorder thermal operators using the Thermofield Bosonization formalism. We
show that the general property of the two-dimensional world according with the
bosonized Fermi field at zero temperature can be constructed as a product of an
order and a disorder variables which satisfy a dual field algebra holds at
finite temperature. The general correlation functions of the order and disorder
thermofields are obtained.Comment: 4 page
Properties of Accretion Shocks in Viscous Flows with Cooling Effects
Low angular momentum accretion flows can have standing and oscillating shock
waves. We study the region of the parameter space in which multiple sonic
points occur in viscous flows in presence of various cooling effects such as
bremsstrahlung and Comptonization. We also quantify the parameter space in
which shocks are steady or oscillating. We find that cooling induces effects
opposite to heating by viscosity even in modifying the topology of the
solutions, though one can never be exactly balanced by the other due to their
dissimilar dependence on dynamic and thermodynamic parameters. We show that
beyond a critical value of cooling, the flow ceases to contain a shock wave.Comment: 18 pages, 12 figures, Accepted for Publication in Int. J. Mod. Phys.
Boltzmann Suppression of Interacting Heavy Particles
Matsumoto and Yoshimura have recently argued that the number density of heavy
particles in a thermal bath is not necessarily Boltzmann-suppressed for T << M,
as power law corrections may emerge at higher orders in perturbation theory.
This fact might have important implications on the determination of WIMP relic
densities. On the other hand, the definition of number densities in a
interacting theory is not a straightforward procedure. It usually requires
renormalization of composite operators and operator mixing, which obscure the
physical interpretation of the computed thermal average. We propose a new
definition for the thermal average of a composite operator, which does not
require any new renormalization counterterm and is thus free from such
ambiguities. Applying this definition to the model of Matsumoto and Yoshimura
we find that it gives number densities which are Boltzmann-suppressed at any
order in perturbation theory. We discuss also heavy particles which are
unstable already at T=0, showing that power law corrections do in general
emerge in this case.Comment: 7 pages, 5 figures. New section added, with the discussion of the
case of an unstable heavy particle. Version to appear on Phys. Rev.
Can WIMP Dark Matter overcome the Nightmare Scenario?
Even if new physics beyond the Standard Model (SM) indeed exists, the energy
scale of new physics might be beyond the reach at the Large Hadron Collider
(LHC) and the LHC could find only the Higgs boson but nothing else. This is the
so-called "nightmare scenario". On the other hand, the existence of the dark
matter has been established from various observations. One of the promising
candidates for thermal relic dark matter is a stable and electric
charge-neutral Weakly Interacting Massive Particle (WIMP) with the mass below
the TeV scale. In the nightmare scenario, we introduce a WIMP dark matter
singlet under the SM gauge group, which only couples to the Higgs doublet at
the lowest order, and investigate a possibility that such WIMP dark matter can
be a clue to overcome the nightmare scenario via various phenomenological tests
such as the dark matter relic abundance, the direct detection experiments for
the dark matter particle, and the production of the dark matter particle at the
LHC.Comment: 14 pages, 10 figure
- …