7,898 research outputs found
Spectral observations of X Persei: Connection between H-alpha and X-ray emission
We present spectroscopic observations of the Be/X-ray binary X Per obtained
during the period 1999 - 2018. Using new and published data, we found that
during "disc-rise" the expansion velocity of the circumstellar disc is 0.4 -
0.7 km/s. Our results suggest that the disc radius in recent decades show
evidence of resonant truncation of the disc by resonances 10:1, 3:1, and 2:1,
while the maximum disc size is larger than the Roche lobe of the primary and
smaller than the closest approach of the neutron star. We find correlation
between equivalent width of H-alpha emission line () and the X-ray
flux, which is visible when . The
correlation is probably due to wind Roche lobe overflow.Comment: Accepted for publication in Astronomy & Astrophysic
Relating B_s Mixing and B_s -> mu+mu- with New Physics
We perform a study of the Standard Model (SM) fit to the mixing quantities
, and in order to bound
contributions of New Physics to mixing. We then use this to explore the
branching fraction of in certain models of New Physics
(NP). In most cases, this constrains NP amplitudes for
to lie below the SM component.Comment: 27 pages, 5 figures; corrected misprints, updated numerical inputs
and new reference
Classification of Spherically Symmetric Static Spacetimes according to their Matter Collineations
The spherically symmetric static spacetimes are classified according to their
matter collineations. These are studied when the energy-momentum tensor is
degenerate and also when it is non-degenerate. We have found a case where the
energy-momentum tensor is degenerate but the group of matter collineations is
finite. For the non-degenerate case, we obtain either {\it four}, {\it five},
{\it six} or {\it ten} independent matter collineations in which four are
isometries and the rest are proper. We conclude that the matter collineations
coincide with the Ricci collineations but the constraint equations are
different which on solving can provide physically interesting cosmological
solutions.Comment: 15 pages, no figure, Late
Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover
Theoretical predictions for the BCS-BEC crossover of trapped Fermi atoms are
compared with recent experimental results for the density profiles of Li.
The calculations rest on a single theoretical approach that includes pairing
fluctuations beyond mean field. Excellent agreement with experimental results
is obtained. Theoretical predictions for the zero-temperature chemical
potential and gap at the unitarity limit are also found to compare extremely
well with Quantum Monte Carlo simulations and with recent experimental results.Comment: 4 pages, 3 eps figure
Teleparallel Killing Vectors of the Einstein Universe
In this short paper we establish the definition of the Lie derivative of a
second rank tensor in the context of teleparallel theory of gravity and also
extend it for a general tensor of rank . This definition is then used to
find Killing vectors of the Einstein universe. It turns out that Killing
vectors of the Einstein universe in the teleparallel theory are the same as in
General Relativity.Comment: 9 pages, accepted for publication in Mod. Phys. Lett.
Configuration interaction calculation of hyperfine and P,T-odd constants on ^{207}PbO excited states for the electron EDM experiments
We report first configuration interaction calculations of hyperfine constants
A_\parallel and the effective electric field W_d acting on the electric dipole
moment of the electron, in two excited electronic states of ^{207}PbO. The
obtained hyperfine constants, A_\parallel = -3826 MHz for the a(1) state and
A_\parallel = 4887 MHz for the B(1) state, are in very good agreement with the
experimental data, -4113 MHz and 5000 \pm 200 MHz, respectively. We find W_d =
-(6.1 ^{+1.8}_{-0.6}) 10^{24} Hz/(e cm) for a(1), and W_d = (8.0 \pm 1.6)
10^{24} Hz/(e cm) for B(1). The obtained values are analyzed and compared to
recent relativistic coupled cluster results and a semiempirical estimate of W_d
for the a(1) state.Comment: 6 pages, REVTeX4 style, submitted to Pthys.Rev.
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