10,176 research outputs found
Delayed Onset and Fast Rise of Prompt Optical-UV Emission from Gamma-Ray Bursts in Molecular Clouds
Observations imply that long \gamma-ray bursts (GRBs) are originated from
explosions of massive stars, therefore they may occur in the molecular clouds
where their progenitors were born. We show here that the prompt optical-UV
emission from GRBs may be delayed due to the dust extinction, which can well
explain the observed optical delayed onset and fast rise in GRB 080319B. The
density and the size of the molecular cloud around GRB 080319B are roughly
constrained to be \sim10^3cm^{-3} and \sim 8pc, respectively. We also
investigate the other GRBs with prompt optical-UV data, and find similar values
of the densities and sizes of the local molecular clouds. The future
observations of prompt optical-UV emission from GRBs in subsecond timescale,
e.g., by UFFO-Pathfinder and SVOM-GWAC, will provide more evidence and probes
of the local GRB environments.Comment: 15 pages, 5 figures, RAA 13 (2013) 57-70, typo correctio
The Necessary and Sufficient Conditions of Separability for Multipartite Pure States
In this paper we present the necessary and sufficient conditions of
separability for multipartite pure states. These conditions are very simple,
and they don't require Schmidt decomposition or tracing out operations. We also
give a necessary condition for a local unitary equivalence class for a
bipartite system in terms of the determinant of the matrix of amplitudes and
explore a variance as a measure of entanglement for multipartite pure states.Comment: Submitted to PRL in Sep. 2004, the paper No is LV9637. Submitted to
SIAM on computing, in Jan., 2005, the paper No. is SICOMP 44687. Under
reviewing no
Semileptonic decays of meson to S-wave charmonium states in the perturbative QCD approach
Inspired by the recent measurement of the ratio of branching fractions
to and final states at the LHCb
detector, we study the semileptonic decays of meson to the S-wave ground
and radially excited 2S and 3S charmonium states with the perturbative QCD
approach. After evaluating the form factors for the transitions , where and denote pseudoscalar and vector S-wave charmonia,
respectively, we calculate the branching ratios for all these semileptonic
decays. The theoretical uncertainty of hadronic input parameters are reduced by
utilizing the light-cone wave function for meson. It is found that the
predicted branching ratios range from up to and could be
measured by the future LHCb experiment. Our prediction for the ratio of
branching fractions is in good
agreement with the data. For decays, the relative
contributions of the longitudinal and transverse polarization are discussed in
different momentum transfer squared regions. These predictions will be tested
on the ongoing and forthcoming experiments.Comment: 12 pages, 3 figures, 5 table
Synthesis of titanium-containing ZSM-48
Titanium-containing ZSM-48 is synthesized with silicon to titanium ratios of 26 or larger; changes in unit cell volume and IR data show that titanium is incorporated into framework positions
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