682 research outputs found
Compton interaction of free electrons with intense low frequency radiation
Electron behavior in an intense low frequency radiation field, with induced Compton scattering as the primary mechanism of interaction, is investigated. Evolution of the electron energy spectrum is studied, and the equilibrium spectrum of relativistic electrons in a radiation field with high brightness temperature is found. The induced radiation pressure and heating rate of an electron gas are calculated. The direction of the induced pressure depends on the radiation spectrum. The form of spectrum, under the induced force can accelerate electrons to superrelativistic energies is found
Hard X-ray emitting black hole fed by accretion of low angular momentum matter
Observed spectra of Active Galactic Nuclei (AGN) and luminous X-ray binaries
in our Galaxy suggest that both hot (~10^9 K) and cold (~10^6 K) plasma
components exist close to the central accreting black hole. Hard X-ray
component of the spectra is usually explained by Compton upscattering of
optical/UV photons from optically thick cold plasma by hot electrons.
Observations also indicate that some of these objects are quite efficient in
converting gravitational energy of accretion matter into radiation. Existing
theoretical models have difficulties in explaining the two plasma components
and high intensity of hard X-rays. Most of the models assume that the hot
component emerges from the cold one due to some kind of instability, but no one
offers a satisfactory physical explanation for this. Here we propose a solution
to these difficulties that reverses what was imagined previously: in our model
the hot component forms first and afterward it cools down to form the cold
component. In our model, accretion flow has initially a small angular momentum,
and thus it has a quasi-spherical geometry at large radii. Close to the black
hole, the accreting matter is heated up in shocks that form due to the action
of the centrifugal force. The hot post-shock matter is very efficiently cooled
down by Comptonization of low energy photons and condensates into a thin and
cold accretion disk. The thin disk emits the low energy photons which cool the
hot component.Comment: 15 pages, 2 figures, submitted to ApJ Let
Quark model description of the tetraquark state X(3872) in a relativistic constituent quark model with infrared confinement
We explore the consequences of treating the X(3872) meson as a tetraquark
bound state. As dynamical framework we employ a relativistic constituent quark
model which includes infrared confinement in an effective way. We calculate the
decay widths of the observed channels X-> Jpsi+2\pi (3\pi) and X-> \bar
D0+D0+\pi0 via the intermediate off--shell states X-> Jpsi+\rho(\omega) and X->
\bar D + D*. For reasonable values of the size parameter of the X(3872) we find
consistency with the available experimental data. We also discuss the possible
impact of the X(3872) in a s-channel dominance description of the
Jpsi-dissociation cross section.Comment: 9 pages, 5 figures; discussion and references added, accepted in
Phys. Rev.
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