140,467 research outputs found
Modular Properties of 3D Higher Spin Theory
In the three-dimensional sl(N) Chern-Simons higher-spin theory, we prove that
the conical surplus and the black hole solution are related by the
S-transformation of the modulus of the boundary torus. Then applying the
modular group on a given conical surplus solution, we generate a 'SL(2,Z)'
family of smooth constant solutions. We then show how these solutions are
mapped into one another by coordinate transformations that act non-trivially on
the homology of the boundary torus. After deriving a thermodynamics that
applies to all the solutions in the 'SL(2,Z)' family, we compute their
entropies and free energies, and determine how the latter transform under the
modular transformations. Summing over all the modular images of the conical
surplus, we write down a (tree-level) modular invariant partition function.Comment: 51 pages; v2: minor corrections and additions; v3: final version, to
appear in JHE
Hard X-ray emissions from Cassiopeia A observed by INTEGRAL
Cassiopeia A (Cas A) as the nearby young remnant of a core-collapse supernova
is the best candidate for astrophysical studies in supernova explosion and its
environment. We studied hard X-ray emissions from Cas A using the ten-year data
of INTEGRAL observations, and first detected non-thermal continuum emission
from the source up to 220 keV. The Ti line emissions at 68 and 78 keV
are confirmed by our observations with a mean flux of ph cm s, corresponding to a Ti yield in Cas A of
\ms. The continuum emission from 3 -- 500 keV can
be fitted with a thermal bremsstrahlung of keV plus a
power-law model of . The non-thermal emission from
Cas A is well fitted with a power-law model without a cutoff up to 220 keV.
This radiation characteristic is inconsistent with the diffusive shock
acceleration models with the remnant shock velocity of only 5000km s.
The central compact object in Cas A cannot contribute to the emission above 80
keV significantly. Some possible physical origins of the non-thermal emission
above 80 keV from the remnant shock are discussed. We deduce that the
asymmetrical supernova explosion scenario of Cas A is a promising scenario to
produce high energy synchrotron radiation photons, where a part of ejecta with
the velocity of and opening angle of can account for
the 100-keV emission, consistent with the "jet" observed in Cas A.Comment: 20 pages, 6 figures, 2 tables; accepted for the publication in Ap
Hunting for the X_b via Radiative Decays
In this paper, we study radiative decays of X_b, the counterpart of the
famous X(3872) in the bottomonium-sector as a candidate for meson-meson
molecule, into the \gamma \Upsilon(nS) (n=1, 2, 3). Since it is likely that the
X_b is below the B\bar B^* threshold and the mass difference between the
neutral and charged bottom meson is small compared to the binding energy of the
X_b, the isospin violating decay mode X_b\to \Upsilon (nS)\pi^+\pi^- would be
greatly suppressed. This will promote the importance of the radiative decays.
We use the effective Lagrangian based on the heavy quark symmetry to explore
the rescattering mechanism and calculate the partial widths. Our results show
that the partial widths into \gamma \Upsilon(nS) are about 1 keV, and thus the
branching fractions may be sizeable, considering the fact the total width may
also be smaller than a few MeV like the X(3872). These radiative decay modes
are of great importance in the experimental search for the X_b particularly at
hadron collider. An observation of the X_b will provide a deeper insight into
the exotic hadron spectroscopy and is helpful to unravel the nature of the
states connected by the heavy quark symmetry.Comment: 10 pages, 4 figure
Hard X-ray emission and Ti line features of Tycho Supernova Remnant
A deep hard X-ray survey of the INTEGRAL satellite first detected the
non-thermal emission up to 90 keV in the Tycho supernova (SN) remnant. Its 3 --
100 keV spectrum is fitted with a thermal bremsstrahlung of keV plus a power-law model of . Based on the
diffusive shock acceleration theory, this non-thermal emission, together with
radio measurements, implies that Tycho remnant may not accelerate protons up to
PeV but hundreds TeV. Only heavier nuclei may be accelerated to the cosmic
ray spectral "knee". In addition, we search for soft gamma-ray lines at 67.9
and 78.4 keV coming from the decay of radioactive Ti in Tycho remnant by
INTEGRAL. A bump feature in the 60-90 keV energy band, potentially associated
with the Ti line emission, is found with a marginal significance level
of 2.6 . The corresponding 3 upper limit on the
Ti line flux amounts to 1.5 10 ph cm s.
Implications on the progenitor of Tycho SN, considered to be the prototype of
type Ia SN, are discussed.Comment: 15 pages, 4 figures, accepted for publication in Ap
Quantum Ion-Acoustic Waves in Single-Walled Carbon Nanotubes Studied with a Quantum Hydrodynamic Model
The quantum ion-acoustic waves in single-wall carbon nanotubes are studied with the quantum hydrodynamic model, in which the electron and ion components of the nanotubes are regarded as a two-species quantum plasma system. An analytical expression of the dispersion relation is obtained for the linear disturbance. Numerical results show that the frequency of the ion-acoustic wave strongly depends on the nanotube’s radius in the long-wavelength cases
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