597 research outputs found
Level Set Dynamics and the Non-blowup of the 2D Quasi-geostrophic Equation
In this article we apply the technique proposed in Deng-Hou-Yu (Comm. PDE,
2005) to study the level set dynamics of the 2D quasi-geostrophic equation.
Under certain assumptions on the local geometric regularity of the level sets
of , we obtain global regularity results with improved growth estimate
on . We further perform numerical simulations to
study the local geometric properties of the level sets near the region of
maximum . The numerical results indicate that the
assumptions on the local geometric regularity of the level sets of in
our theorems are satisfied. Therefore these theorems provide a good explanation
of the double exponential growth of observed in this
and past numerical simulations.Comment: 25 pages, 10 figures. Corrected a few typo
Jet-cloud/star interaction as an interpretation of neutrino outburst from the blazar TXS 0506+056
Recently, a high-energy neutrino event IceCube-170922A in the spatial and
temporal coincidence with the flaring gamma-ray blazar TXS 0506+056 was
reported. A neutrino outburst between September 2014 and March 2015 was
discovered in the same direction by a further investigation of years of
IceCube data, while the blazar is in a quiescent state during the outburst with
a gamma-ray flux only about one-fifth of the neutrino flux. In this letter, we
propose the neutrino outburst originates from the interaction between a
relativistic jet and a dense gas cloud which may be formed via the tidally
disrupted envelope of a red giant being blown by the impact of the jet.
Gamma-ray photons and electron/positron pairs that are produced correspondingly
will induce electromagnetic cascades. Comptonization of the cascade emission
inside the cloud forms an X-ray photon field with Wien distribution. GeV flux
is suppressed due to the absorption by the Comptonized photon field and, as a
result, a hard spectrum above 10 GeV is formed. The gamma-ray spectrum
predicted in our model is consistent with the Fermi-LAT data of TXS 0506+056.Comment: 6 pages, 3 figure
1,3-Diprop-2-ynyl-1H-imidazol-3-ium bromide
In the title salt, C9H9N2
+·Br−, the ethynyl groups are nearly antiÂparallel to each other [the angle between the two ethynyl groups is179.7 (2)°]. No classical hydrogen bonds or π–π interÂactions are observed. The molÂecules are linked by C—H⋯Br hydrogen bonds. The bromide anions are involved in interÂactions with three H atoms
On the Origin of Galactic Diffuse TeV-PeV Emission: Insight from LHAASO and IceCube
The high-energy diffuse gamma-ray emission and neutrino emission are expected
from the Galactic plane, generated by hadronuclear interactions between cosmic
rays (CR) and interstellar medium (ISM). Therefore, measurements of these
diffuse emissions will provide important clues on the origin and nature of
Galactic CRs. Comparing the latest observations of LHAASO and IceCube on the
diffuse Galactic gamma-ray and neutrino emissions respectively, we suggest that
the diffuse gamma-ray emission at multi-TeV energies contains a considerable
contribution of a leptonic component. By modelling the gamma-ray halos powered
by middle-aged pulsars in our Galaxy with taking into account the magnetic
field configuration and the interstellar radiation field in the Galaxy, we
demonstrate that the collective contribution of pulsar halos can account for
the excess in the measured diffuse gamma-ray emission with respect to the
predicted flux from CR-ISM interactions. The resulting one-dimensional profile
along the Galactic longitude is also consistent with the observation.Comment: 24 pages, 11 figures; Comments are Welcom
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