44,352 research outputs found
Heavy Quarkonium Potential Model and the State of Charmonium
A theoretical explanation of the observed splittings among the P~states of
charmonium is given with the use of a nonsingular potential model for heavy
quarkonia. We also show that the recently observed mass difference between the
center of gravity of the states and the state of
does not provide a direct test of the color hyperfine interaction in heavy
quarkonia. Our theoretical value for the mass of the state is in
agreement with the experimental result, and its E1 transition width is
341.8~keV. The mass of the state is predicted to be 3622.3~MeV.Comment: 15 page REVTEX documen
Pulsar Scintillation and the Local Bubble
We present here the results from an extensive scintillation study of twenty
pulsars in the dispersion measure (DM) range 3 - 35 pc cm^-3 caried out using
the Ooty Radio Telescope (ORT) at 327 MHz, to investigate the distribution of
ionized material in the local interstellar medium. Observations were made
during the period January 1993 to August 1995, in which the dynamic
scintillation spectra of these pulsars were regularly monitored over 10 - 90
epochs spanning 100 days. Reliable and accurate estimates of strengths of
scattering have been deduced from the scintillation parameters averaged out for
their long-term fluctuations arising from refractive scintillation (RISS)
effects. Our analysis reveals several anomalies in the scattering strength,
which suggest tht the distribution of scattering material in the Solar
neighborhood is not uniform.
We have modelled these anomalous scattering effects in terms of
inhomogeneities in the distribution of electron dnsity fluctuations in the
local interstellar medium (LISM). Our model suggests the presence of a low
density bubble surrounded by a shell of much higher density fluctuations. We
are able to put constraints on geometrical and scattering properties of such a
structure, and find it to be morphologically similar to the Local Bubble known
from other studies.Comment: 35 pages, 12 figure
Long-Term Scintillation Studies of Pulsars: III. Testing Theoretical Models of Refractive Scintillation
Refractive interstellar scintillation (RISS) is thought to be the cause
behind a variety of phenomena seen at radio wavelengths in pulsars and compact
radio sources. Though there is substantial observational data to support
several consequences of it, the quantitative predictions from theories have not
been thoroughly tested. In this paper, data from our long-term scintillation
study of 18 pulsars are used to test the predictions. The fluctuations of
decorrelation bandwidth (), scintillation time scale () and flux
density (F) are examined for their cross-correlations and compared with the
predictions. The theory predicts a strong correlation between and
, and strong anti-correlations between and F, and and
F. For 5 pulsars, we see a reasonable agreement. There is considerable
difficulty in reconciling the results for the rest of the pulsars. Our analysis
shows the underlying noise sources can sometimes reduce the correlation, but
cannot cause an absence of correlation. It is also unlikely that the poor flux
correlations arise from a hitherto unrecognized intrinsic flux variations. For
PSR B0834+06, which shows anomalous behaviour of persistent drift slopes,
positive correlation is found between and the drift-corrected .
Many pulsars show an anti-correlation between and the drift slope, and
this is in accordance with the simple models of RISS. The detections of
correlated variations of observables and a reasonable agreement between the
predicted and measured correlations for some pulsars confirm RISS as the
primary cause of the observed fluctuations. However, the complexity seen with
the detailed results suggests the necessity of more comprehensive theoretical
treatments for describing refractive fluctuations and their correlations.Comment: 27 pages, 6 Figures, 6 Tables. Accepted for publication in The
Astrophysical Journa
Surface-slip equations for multicomponent nonequilibrium air flow
Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds number, high-altitude flight regime of a space vehicle. The equations are obtained from closed form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities were obtained in a form which can be employed in flowfield computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate, species-concentration boundary condition for a multicomponent mixture in absence of slip
A new microscopic nucleon-nucleon interaction derived from relativistic mean field theory
A new microscopic nucleon-nucleon (NN) interaction has been derived for the
first time from the popular relativistic mean field theory (RMFT) Lagrangian.
The NN interaction so obtained remarkably relate to the inbuilt fundamental
parameters of RMFT. Furthermore, by folding it with the RMFT-densities of
cluster and daughter nuclei to obtain the optical potential, it's application
is also examined to study the exotic cluster radioactive decays, and results
obtained found comparable with the successfully used M3Y phenomenological
effective NN interactions. The presently derived NN-interaction can also be
used to calculate a number of other nuclear observables.Comment: 4 Pages 2 Figure
Surface-slip equations for multicomponent, nonequilibrium air flow
Equations are presented for the surface slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds-number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in absence of slip
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