23,326 research outputs found
Evolution of induced axial magnetization in a two-component magnetized plasma
In this paper, the evolution of the induced axial magnetization due to the
propagation of an electromagnetic (em) wave along the static background
magnetic field in a two-component plasma has been investigated using the Block
equation. The evolution process induces a strong magnetic anisotropy in the
plasma medium, depending nonlinearly on the incident wave amplitude. This
induced magnetic anisotropy can modify the dispersion relation of the incident
em wave, which has been obtained in this paper. In the low frequency Alfven
wave limit, this dispersion relation shows that the resulting phase velocity of
the incident wave depends on the square of the incident wave amplitude and on
the static background magnetic field of plasma. The analytical results are in
well agreement with the numerically estimated values in solar corona and
sunspots.Comment: 7 pages, 1 figur
Investigation into the limits of perturbation theory at low Q^2 using HERA deep inelastic scattering data
A phenomenological study of the final combined HERA data on inclusive deep
inelastic scattering (DIS) has been performed. The data are presented and
investigated for a kinematic range extending from values of the four-momentum
transfer, , above 10 GeV down to the lowest values observable at
HERA of = 0.045 GeV and Bjorken , = 6
10. The data are well described by fits based on perturbative quantum
chromodynamics (QCD) using collinear factorisation and evolution of the parton
densities encompassed in the DGLAP formalism from the highest down to
of a few GeV. The Regge formalism can describe the data up to 0.65 GeV. The complete data set can be described by a new fit
using the ALLM parameterisation. The region between the Regge and the
perturbative QCD regimes is of particular interest.Comment: 38 pages, 13 figure
Leptogenesis bound on neutrino masses in left-right symmetric models with spontaneous D-parity violation
We study the baryogenesis via leptogenesis in a class of left-right symmetric
models, in which -parity is broken spontaneously. We first discuss the
consequence of the spontaneous -parity breaking on the neutrino masses. Than
we study the lepton asymmetry in various cases, from the decay of right handed
neutrino as well as the triplet Higgs, depending on their relative masses they
acquire from the symmetry breaking pattern. The leptogenesis bound on their
masses are discussed by taking into account the low energy neutrino oscillation
data. It is shown that a TeV scale leptogenesis is viable if there are
additional sources of CP violation like domain wall originating from the
spontaneous -parity violation.Comment: 32 pages (revtex), 12 eps figures, clarifications are added in
section VII, A new section VIII is added, useful references are added.
Journal version, To appear in Phys. Rev.
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Do arsenic levels in rice pose a health risk to the UK population?
Consumption of rice and rice products can be a significant exposure pathway to inorganic arsenic (iAs), which is a group 1 carcinogen to humans. The UK follows the current European Commission regulations so that iAs concentrations must be  0.1 mg kg-1 were selected for As speciation using HPLC-ICP-MS. Based on the average concentration of iAs of our samples, we calculated values for the Lifetime Cancer Risk (LCR), Target Hazard Quotient (THQ) and Margin of Exposure (MoE). We found a statistically significant difference between organically and non-organically grown rice. We also found that brown rice contained a significantly higher concentration of iAs compared to white or wild rice. Notably, 28 rice samples exceeded the iAs maximum limit stipulated by the EU (0.1 mg kg-1) with an average iAs concentration of 0.13 mg kg-1; therefore consumption of these rice types could be riskier for infants than adults. Based on the MoE, it was found that infants up to 1 year must be restricted to a maximum of 20 g per day for the 28 rice types to avoid carcinogenic risks. We believe that consumers could be better informed whether the marketed product is fit for infants and young children, via appropriate product labelling containing information about iAs concentration
On Dimer Models and Closed String Theories
We study some aspects of the recently discovered connection between dimer
models and D-brane gauge theories. We argue that dimer models are also
naturally related to closed string theories on non compact orbifolds of \BC^2
and \BC^3, via their twisted sector R charges, and show that perfect
matchings in dimer models correspond to twisted sector states in the closed
string theory. We also use this formalism to study the combinatorics of some
unstable orbifolds of \BC^2.Comment: 1 + 25 pages, LaTeX, 11 epsf figure
A framework to analyse the effect of hotel websites stimuli on emotions, attitude and intentions moderated by sensory curiosity; language of instruction; classification of hotel; and annual income of customer
The present study reviews the literature about the S–O–R framework and proposes an extending model regarding attitude and behavioral intentions as responses. Additionally, the model hypothesizes that sensory curiosity, language of instruction, classification of Hotel, and annual income of customer moderate the relationships between atmospheric cues and consumers’ emotional reactions. The proposed model should be tested using two samples. One sample should gather consumers who have experience of using and booking in hotel websites. Another sample, a group of control, should be composed of people with no experience in using the hotel website for booking
Asymptotic Analysis of the Boltzmann Equation for Dark Matter Relics
This paper presents an asymptotic analysis of the Boltzmann equations
(Riccati differential equations) that describe the physics of thermal
dark-matter-relic abundances. Two different asymptotic techniques are used,
boundary-layer theory, which makes use of asymptotic matching, and the delta
expansion, which is a powerful technique for solving nonlinear differential
equations. Two different Boltzmann equations are considered. The first is
derived from general relativistic considerations and the second arises in
dilatonic string cosmology. The global asymptotic analysis presented here is
used to find the long-time behavior of the solutions to these equations. In the
first case the nature of the so-called freeze-out region and the
post-freeze-out behavior is explored. In the second case the effect of the
dilaton on cold dark-matter abundances is calculated and it is shown that there
is a large-time power-law fall off of the dark-matter abundance. Corrections to
the power-law behavior are also calculated.Comment: 15 pages, no figure
Estimation of Primordial Spectrum with post-WMAP 3 year data
In this paper we implement an improved (error sensitive) Richardson-Lucy
deconvolution algorithm on the measured angular power spectrum from the WMAP 3
year data to determine the primordial power spectrum assuming different points
in the cosmological parameter space for a flat LCDM cosmological model. We also
present the preliminary results of the cosmological parameter estimation by
assuming a free form of the primordial spectrum, for a reasonably large volume
of the parameter space. The recovered spectrum for a considerably large number
of the points in the cosmological parameter space has a likelihood far better
than a `best fit' power law spectrum up to \Delta \chi^2_{eff} \approx -30. We
use Discrete Wavelet Transform (DWT) for smoothing the raw recovered spectrum
from the binned data. The results obtained here reconfirm and sharpen the
conclusion drawn from our previous analysis of the WMAP 1st year data. A sharp
cut off around the horizon scale and a bump after the horizon scale seem to be
a common feature for all of these reconstructed primordial spectra. We have
shown that although the WMAP 3 year data prefers a lower value of matter
density for a power law form of the primordial spectrum, for a free form of the
spectrum, we can get a very good likelihood to the data for higher values of
matter density. We have also shown that even a flat CDM model, allowing a free
form of the primordial spectrum, can give a very high likelihood fit to the
data. Theoretical interpretation of the results is open to the cosmology
community. However, this work provides strong evidence that the data retains
discriminatory power in the cosmological parameter space even when there is
full freedom in choosing the primordial spectrum.Comment: 13 pages, 4 figures, uses Revtex4, new analysis and results,
references added, matches version accepted to Phys. Rev.
Synthesis, photophysical and metal ion signalling behaviour of mono- and di-azacrown derivatives of 4-aminophthalimide
Synthesis, photophysical behaviour and metal ion signalling ability of 3-component systems, I and II, comprising a 4-aminophthalimido moiety as fluorophore, a dimethylene spacer and two different azacrown receptors, are reported. The fluorescence quantum yields and lifetimes of both the systems have been found to be significantly lower than that of the parent fluorophore indicating the occurrence of photoinduced electron transfer (PET) between the terminal moieties. PET is found to be more efficient in II, presumably due to the presence of more than one electron-donating centre in the receptor moiety. Fluorescence decay behaviour of the systems suggests a through-space nature of PET. The systems exhibit off-on fluorescence signalling in the aprotic media in the presence of several metal ions, some of which are well known for their fluorescence quenching abilities. Diazacrown derivative, II, appears to be a somewhat better signalling system than the monoazacrown derivative, I
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