23,087 research outputs found
Theory of non-stationary activated rate processes : nonexponential relaxation kinetics
We have explored a simple microscopic model to simulate a thermally activated
rate process where the associated bath which comprises a set of relaxing modes
is not in an equilibrium state. The model captures some of the essential
features of non-Markovian Langevin dynamics with a fluctuating barrier. Making
use of the Fokker-Planck description we calculate the barrier dynamics in the
steady state and non-stationary regimes. The Kramers-Grote-Hynes reactive
frequency has been computed in closed form in the steady state to illustrate
the strong dependence of the dynamic coupling of the system with the relaxing
modes. The influence of nonequilibrium excitation of the bath modes and its
relaxation on the kinetics of activation of the system mode is demonstrated. We
derive the dressed time-dependent Kramers rate in the nonstationary regime in
closed analytical form which exhibits strong non-exponential relaxation
kinetics of the reaction co-ordinate. The feature can be identified as a
typical non-Markovian dynamical effect.Comment: Plain Latex, no figure, 31 pages, to appear in J. Chem. Phy
Strange stars at finite temperature
We calculate strange star properties, using large N_c approximation with
built-in chiral symmetry restoration (CSM). We used a relativistic Hartree Fock
mean field approximation method, using a modified Richardson potential with two
scale parameters \Lambda and \Lambda^\prime, to find a new set of equation of
states for strange quark matter. We take the effect of temperature (T) on gluon
mass, in addition to the usual density dependence, and find that the transition
T from hadronic matter to strange matter is 80 MeV. Therefore formation of
strange stars may be the only signal for formation of QGP with asymptotic
freedom and CSM.Comment: To be published in the proceedings of The Third 21COE Symposium, held
at Department of Physics, Waseda University, Tokyo, Japan, September 1-3,
200
The Astronomy of the Kamilaroi People and their Neighbours
The Kamilaroi people and their neighbours, the Euahlayi, Ngemba, and
Murrawarri, are an Aboriginal cultural grouping located in the northwest and
north central of New South Wales. They have a rich history, but have been
missed in much of the literature concerned with sky knowledge in culture. This
study collected stories, some of which have not previously been reported in an
academic format, from Aboriginal people practicing their culture, augmented
with stories from the literature, and analysed the data to create a database of
sky knowledge that will be added to the larger body of Aboriginal cultural
knowledge in Australia. We found that there is a strong sky culture reflected
in the stories, and we also explored the stories for evidence of an
ethnoscientific approach to knowledge of the sky.Comment: 28 pages, 9 figure
Does monetary policy have differential state-level effects? an empirical evaluation
The paper examines whether monetary policy has similar effects across major states in the Indian polity. Impulse response functions from an estimated Structural Vector Auto Regression (SVAR) reveal two sets of states: a core of states that respond to monetary policy in a significant fashion vis-à-vis others whose response is less significant. The paper attempts to trace the reasons for the differential response of these two sets of states in terms of financial deepening and differential industry mix.monetary policy; regional effect; optimum currency area
Orientations of linear stone arrangements in New South Wales
We test the hypothesis that Aboriginal linear stone arrangements in New South
Wales (NSW) are oriented to cardinal directions. We accomplish this by
measuring the azimuths of stone arrangements described in site cards from the
NSW Aboriginal Heritage Information Management System. We then survey a subset
of these sites to test the accuracy of information recorded on the site cards.
We find a preference recorded in the site cards for cardinal orientations among
azimuths. The field surveys show that the site cards are reasonably accurate,
but the surveyors probably did not correct for magnetic declinations. Using
Monte Carlo statistics, we show that these preferred orientations did not occur
by chance and that Aboriginal people deliberately aligned these arrangements to
the approximate cardinal directions. We briefly explore possible reasons for
these preferred orientations and highlight the need for future work.Comment: Australian Archaeology, Volume 75 (December 2012), accepte
Anisotropic cosmological models with two fluids
In this paper, aniostropic dark energy cosmological models have been
constructed in a Bianchi-V space-time with the energy momentum tensor
consisting of two non-interacting fluids namely bulk viscous fluid and dark
energy fluid. Two different models are constructed based on the power law
cosmology and de Sitter universe. The constructed model also embedded with
different pressure gradients along different spatial directions. The variable
equation of state (EoS) parameter, skewness parameters for both the models are
obtained and analyzed. The physical properties of the models obtained with the
use of scale factors of power law and de Sitter law are also presented.Comment: 10 pages, 12 figure
The late time radio emission from SN 1993J at meter wavelengths
We present the investigations of SN 1993J using low frequency observations
with the Giant Meterwave Radio Telescope. We analyze the light curves of SN
1993J at 1420, 610, 325 and 243 MHz during years since explosion.The
supernova has become optically thin early on in the 1420 MHz and 610 MHz bands
while it has only recently entered the optically thin phase in the 325 MHz
band. The radio light curve in the 235 MHz band is more or less flat. This
indicates that the supernova is undergoing a transition from an optically thick
to optically thin limit in this frequency band. In addition, we analyze the SN
radio spectra at five epochs on day 3000, 3200, 3266, 3460 and 3730 since
explosion. Day 3200 spectrum shows a synchrotron cooling break. SN 1993J is the
only young supernova for which the magnetic field and the size of the radio
emitting region are determined through unrelated methods. Thus the mechanism
that controls the evolution of the radio spectra can be identified. We suggest
that at all epochs, the synchrotron self absorption mechanism is primarily
responsible for the turn-over in the spectra. Light curve models based on free
free absorption in homogeneous or inhomogeneous media at high frequencies
overpredict the flux densities at low frequencies. The discrepancy is
increasingly larger at lower and lower frequencies. We suggest that an extra
opacity, sensitively dependent on frequency, is likely to account for the
difference at lower frequencies. The evolution of the magnetic field
(determined from synchrotron self absorption turn-over) is roughly consistent
with . Radio spectral index in the optically thin part
evolves from at few tens of days to in about
10 years.Comment: 37 pages, 9 figures in LaTex; scheduled for ApJ 10 September 2004,
v612 issue; send comments to: [email protected]
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