15,122 research outputs found
Light-cone path integral approach to the induced radiation in QED and QCD: basic concepts and recent applications
I discuss the basic ideas of the light-cone path integral approach to the
induced radiation in QED and QCD and recent applications to the induced parton
energy loss.Comment: 5 pages, 4 figures. Talk given at the International Workshop
Diffraction-2004, Cala Gonone, Sardinia, Italy, 18-23 Sept 2004; to appear in
the Proceedings. Minor correction
Parton energy loss in glasma
We study the synchrotron-like gluon emission in -collisions from fast
partons due to interaction with the coherent glasma color fields. Our results
show that for RHIC and LHC conditions the contribution of this mechanism to
parton energy loss is much smaller than the radiative energy loss in the plasma
phase.Comment: 14 pages, 3 figure
On the Dressing Method for the Generalised Zakharov--Shabat System
The dressing procedure for the Generalised Zakharov--Shabat system is well
known for systems, related to sl(N) algebras. We extend the method,
constructing explicitly the dressing factors for some systems, related to
orthogonal and symplectic Lie algebras. We consider 'dressed' fundamental
analytical solutions with simple poles at the prescribed eigenvalue points and
obtain the corresponding Lax potentials, representing the soliton solutions for
some important nonlinear evolution equations.Comment: 17 pages, LaTe
Effect of electric field of the electrosphere on photon emission from quark stars
We investigate the photon emission from the electrosphere of a quark star. It
is shown that at temperatures MeV the dominating mechanism is the
bremsstrahlung due to bending of electron trajectories in the mean Coulomb
field of the electrosphere. The radiated energy flux from this mechanism
exceeds considerably both the contribution from the bremsstrahlung due to
electron-electron interaction and the tunnel pair creation.Comment: 9 pages, 2 figure
Transition radiation in the quantum regime as a diffractive phenomenon
We demonstrate that the transition photon radiation and pair creation can be
interpreted as a diffractive phenomenon in terms of the light-cone wave
functions in a way similar to the Good-Walker approach [6] to the diffraction
dissociation. Our formulas for spectra agree with those obtained by Baier and
Katkov [5] within the quasiclassical operator method. However, there is some
disagreement with earlier results by Garibyan [4].Comment: 7 pages. The journal version published in Phys. Lett.
Nonlinear dynamics of soft fermion excitations in hot QCD plasma II: Soft-quark - hard-particle scattering and energy losses
In general line with our first work [Yu.A. Markov, M.A. Markova, Nucl. Phys.
A 770 (2006) 162] within the framework of semiclassical approximation a general
theory for the scattering processes of soft (anti)quark excitations off hard
thermal particles in hot QCD-medium is thoroughly considered. The dynamical
equations describing evolution for the usual classical color charge
and Grassmann color charges of hard
particle taking into account the soft fermion degree of freedom of the system
are suggested. On the basis of these equations and the Blaizot-Iancu equations
iterative procedure of calculation of effective currents and sources generating
the scattering processes under consideration is defined and their form up to
third order in powers of free soft quark field, soft gluon one, and initial
values of the color charges of hard particle is explicitly calculated. With use
of the generalized Tsytovich principle a connection between matrix elements of
the scattering processes and the effective currents and sources is established.
In the context of the effective theory suggested for soft and hard fermion
excitations new mechanisms of energy losses of high-energy parton propagating
through QCD-medium are considered.Comment: 85 pages, 15 figures, added new appendix A, section 10 is removed,
mistakes, and typing errors are corrected. Version to appear in Nucl. Phys.
Wave turbulence in Bose-Einstein condensates
The kinetics of nonequilibrium Bose-Einstein condensates are considered
within the framework of the Gross-Pitaevskii equation. A systematic derivation
is given for weak small-scale perturbations of a steady confined condensate
state. This approach combines a wavepacket WKB description with the weak
turbulence theory. The WKB theory derived in this paper describes the effect of
the condensate on the short-wave excitations which appears to be different from
a simple renormalization of the confining potential suggested in previous
literature.Comment: 33 pages 2 figure
Coexistence of Weak and Strong Wave Turbulence in a Swell Propagation
By performing two parallel numerical experiments -- solving the dynamical
Hamiltonian equations and solving the Hasselmann kinetic equation -- we
examined the applicability of the theory of weak turbulence to the description
of the time evolution of an ensemble of free surface waves (a swell) on deep
water. We observed qualitative coincidence of the results.
To achieve quantitative coincidence, we augmented the kinetic equation by an
empirical dissipation term modelling the strongly nonlinear process of
white-capping. Fitting the two experiments, we determined the dissipation
function due to wave breaking and found that it depends very sharply on the
parameter of nonlinearity (the surface steepness). The onset of white-capping
can be compared to a second-order phase transition. This result corroborates
with experimental observations by Banner, Babanin, Young.Comment: 5 pages, 5 figures, Submitted in Phys. Rev. Letter
Bright solitons in Bose-Fermi mixtures
We consider the formation of bright solitons in a mixture of Bose and Fermi
degenerate gases confined in a three-dimensional elongated harmonic trap. The
Bose and Fermi atoms are assumed to effectively attract each other whereas
bosonic atoms repel each other. Strong enough attraction between bosonic and
fermionic components can change the character of the interaction within the
bosonic cloud from repulsive to attractive making thus possible the generation
of bright solitons in the mixture. On the other hand, such structures might be
in danger due to the collapse phenomenon existing in attractive gases. We show,
however, that under some conditions (defined by the strength of the Bose-Fermi
components attraction) the structures which neither spread nor collapse can be
generated. For elongated enough traps the formation of solitons is possible
even at the ``natural'' value of the mutual Bose-Fermi (Rb -K in
our case) scattering length.Comment: 6 pages, 6 figures, 1 tabl
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