1,673 research outputs found
A New Exponential Gravity
We propose a new exponential f(R) gravity model with f(R)=(R-\lambda
c)e^{\lambda(c/R)^n} and n>3, \lambda\geq 1, c>0 to explain late-time
acceleration of the universe. At the high curvature region, the model behaves
like the \LambdaCDM model. In the asymptotic future, it reaches a stable
de-Sitter spacetime. It is a cosmologically viable model and can evade the
local gravity constraints easily. This model share many features with other
f(R) dark energy models like Hu-Sawicki model and Exponential gravity model. In
it the dark energy equation of state is of an oscillating form and can cross
phantom divide line \omega_{de}=-1. In particular, in the parameter range 3<
n\leq 4, \lambda \sim 1, the model is most distinguishable from other models.
For instance, when n=4, \lambda=1, the dark energy equation of state will cross
-1 in the earlier future and has a stronger oscillating form than the other
models, the dark energy density in asymptotical future is smaller than the one
in the high curvature region. This new model can evade the local gravity tests
easily when n>3 and \lambda>1.Comment: 12 pages, 8 figure
Bagchi's Theorem for families of automorphic forms
We prove a version of Bagchi's Theorem and of Voronin's Universality Theorem
for family of primitive cusp forms of weight and prime level, and discuss
under which conditions the argument will apply to general reasonable family of
automorphic -functions.Comment: 15 page
Smooth free involution of and Smith conjecture for imbeddings of in
This paper establishes an equivalence between existence of free involutions
on and existence of involutions on with fixed point set an
imbedded , then a family of counterexamples of the Smith conjecture for
imbeddings of in are given by known result on . In
addition, this paper also shows that every smooth homotopy complex projective
3-space admits no orientation preserving smooth free involution, which answers
an open problem [Pe]. Moreover, the study of existence problem for smooth
orientation preserving involutions on is completed.Comment: 10 pages, final versio
Meta-transcriptomic discovery of a divergent circovirus and a chaphamaparvovirus in captive reptiles with proliferative respiratory syndrome
Viral pathogens are being increasingly described in association with mass morbidity and mortality events in reptiles. However, our knowledge of reptile viruses remains limited. Herein, we describe the meta-transcriptomic investigation of a mass morbidity and mortality event in a colony of central bearded dragons (Pogona vitticeps) in 2014. Severe, extensive proliferation of the respiratory epithelium was consistently found in affected dragons. Similar proliferative lung lesions were identified in bearded dragons from the same colony in 2020 in association with increased intermittent mortality. Total RNA sequencing identified two divergent DNA viruses: a reptile-infecting circovirus, denoted bearded dragon circovirus (BDCV), and the first exogeneous reptilian chaphamaparvovirus—bearded dragon chaphamaparvovirus (BDchPV). Phylogenetic analysis revealed that BDCV was most closely related to bat-associated circoviruses, exhibiting 70% amino acid sequence identity in the Replicase (Rep) protein. In contrast, in the nonstructural (NS) protein, the newly discovered BDchPV showed approximately 31%–35% identity to parvoviruses obtained from tilapia fish and crocodiles in China. Subsequent specific PCR assays revealed BDCV and BDchPV in both diseased and apparently normal captive reptiles, although only BDCV was found in those animals with proliferative pulmonary lesions and respiratory disease. This study expands our understanding of viral diversity in captive reptiles
An optimal series expansion of the multiparameter fractional Brownian motion
We derive a series expansion for the multiparameter fractional Brownian
motion. The derived expansion is proven to be rate optimal.Comment: 21 pages, no figures, final version, to appear in Journal of
Theoretical Probabilit
Doping dependent Irreversible Magnetic Properties of Ba(Fe1-xCox)2As2 Single Crystals
We discuss the irreversible magnetic properties of self-flux grown
Ba(Fe1-xCox)2As2 single crystals for a wide range of concentrations covering
the whole phase diagram from the underdoped to the overdoped regime, x=0.038,
0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized
by a magneto-optical method and show excellent spatial uniformity of the
superconducting state. The overall behavior closely follows classical Bean
model of the critical state. The field-dependent magnetization exhibits second
peak at a temperature and doping - dependent magnetic field, Hp. The evolution
of this fishtail feature with doping is discussed. Magnetic relaxation is
time-logarithmic and unusually fast. Similar to cuprates, there is an apparent
crossover from collective elastic to plastic flux creep above Hp. At high
fields, the field dependence of the relaxation rate becomes doping independent.
We discuss our results in the framework of the weak collective pinning and show
that vortex physics in iron-based pnictide crystals is much closer to high-Tc
cuprates than to conventional s-wave (including MgB2) superconductors.Comment: for the special issue of Physica C on iron-based pnictide
superconductor
Corrections to Hawking-like Radiation for a Friedmann-Robertson-Walker Universe
Recently, a Hamilton-Jacobi method beyond semiclassical approximation in
black hole physics was developed by \emph{Banerjee} and
\emph{Majhi}\cite{beyond0}. In this paper, we generalize their analysis of
black holes to the case of Friedmann-Robertson-Walker (FRW) universe. It is
shown that all the higher order quantum corrections in the single particle
action are proportional to the usual semiclassical contribution. The
corrections to the Hawking-like temperature and entropy of apparent horizon for
FRW universe are also obtained. In the corrected entropy, the area law involves
logarithmic area correction together with the standard inverse power of area
term.Comment: 10 pages, no figures, comments are welcome; v2: references added and
some typoes corrected, to appear in Euro.Phys.J.C; v3:a defect corrected. We
thank Dr.Elias Vagenas for pointing out a defect of our pape
Anomaly analysis of Hawking radiation from Kaluza-Klein black hole with squashed horizon
Considering gravitational and gauge anomalies at the horizon, a new method
that to derive Hawking radiations from black holes has been developed by
Wilczek et al. In this paper, we apply this method to non-rotating and rotating
Kaluza-Klein black holes with squashed horizon, respectively. For the rotating
case, we found that, after the dimensional reduction, an effective U(1) gauge
field is generated by an angular isometry. The results show that the gauge
current and energy-momentum tensor fluxes are exactly equivalent to Hawking
radiation from the event horizon.Comment: 15 pages, no figures, the improved version, accepted by Eur. Phys. J.
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