2,051 research outputs found
Fronts in passive scalar turbulence
The evolution of scalar fields transported by turbulent flow is characterized
by the presence of fronts, which rule the small-scale statistics of scalar
fluctuations. With the aid of numerical simulations, it is shown that: isotropy
is not recovered, in the classical sense, at small scales; scaling exponents
are universal with respect to the scalar injection mechanisms; high-order
exponents saturate to a constant value; non-mature fronts dominate the
statistics of intense fluctuations. Results on the statistics inside the
plateaux, where fluctuations are weak, are also presented. Finally, we analyze
the statistics of scalar dissipation and scalar fluxes.Comment: 18 pages, 27 figure
Numerical modeling of stimulation of induced magnetosphere during interaction of solar wind with the ionosphere of Venus
Electrodynamic processes in the ionopause are examined as well as the structure of the induced magnetosphere
BFKL Pomeron, Reggeized gluons and Bern-Dixon-Smirnov amplitudes
After a brief review of the BFKL approach to Regge processes in QCD and in
supersymmetric (SUSY) gauge theories we propose a strategy for calculating the
next-to-next-to-leading order corrections to the BFKL kernel. They can be
obtained in terms of various cross-sections for Reggeized gluon interactions.
The corresponding amplitudes can be calculated in the framework of the
effective action for high energy scattering. In the case of N=4 SUSY it is also
possible to use the Bern-Dixon-Smirnov (BDS) ansatz. For this purpose the
analytic properties of the BDS amplitudes at high energies are investigated, in
order to verify their self-consistency. It is found that, for the number of
external particles being larger than five, these amplitudes, beyond one loop,
are not in agreement with the BFKL approach which predicts the existence of
Regge cuts in some physical channels.Comment: 41 pages, expanded version with many clarifications and new
references, conclusions unchanged. Note adde
Duality symmetry of BFKL equation: reggeized gluons vs color dipoles
We show that the duality symmetry of the BFKL equation can be interpreted as
a symmetry under rotation of the BFKL Kernel in the transverse space from
s-channel (color dipole model) to t-channel (reggeized gluon formulation). We
argue that the duality symmetry holds also in the non-forward case due to a
very special structure of the non-forward BFKL Kernel, which can be written as
a sum of three forward BFKL Kernels. The duality symmetry is established by
identifying the dual coordinates with the transverse coordinates of a
non-diagonal dipole scattered off the target.Comment: 13 pages, 5 figure
QCD Saturation Equations including Dipole-Dipole Correlation
We derive two coupled non-linear evolution equations corresponding to the
truncation of the Balitsky infinite hierarchy of saturation equations after
inclusion of dipole-dipole correlations, i.e. one step beyond the
Balitsky-Kovchegov (BK) equation. We exhibit an exact solution for maximal
correlation which still satisfies the same asymptotic geometric scaling as BK
but with the S-matrix going to 1/2 (instead of 0) in the full saturation
region.Comment: 4 pages, no figure. Comment, references and acknowledgment adde
TMD parton densities in associated real and virtual photon and jet production at LHC
We study the associated production of real (isolated) or virtual photons
(with their subsequent leptonic decay) and hadronic jets in proton-proton
collisions at the LHC using the -factorization approach of QCD. The
consideration is based on the off-shell quark-gluon QCD Compton scattering
subprocesses. In the case of virtual photon production, the contributions from
Z boson exchange as well as gamma*-Z interference with the full spin
correlations are included. The transverse momentum dependent (TMD) quark and
gluon densities in a proton are determined from the Kimber-Martin-Ryskin
prescription or Catani-Ciafoloni-Fiorani-Marchesini (CCFM) equation. In the
latter, we restricted to the case where the gluon-to-quark splitting occurs at
the last evolution step and calculate the sea quark density as a convolution of
the CCFM-evolved gluon distribution and the TMD gluon-to-quark splitting
function. Our numerical predictions are compared with the recent experimental
data taken by the ATLAS Collaboration. We discuss the theoretical uncertainties
of our calculations and argue that further studies are capable of constraining
the TMD parton densities in a proton.Comment: 11 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1402.549
Effective action for the Regge processes in gravity
It is shown, that the effective action for the reggeized graviton
interactions can be formulated in terms of the reggeon fields and
and the metric tensor in such a way, that it is local in
the rapidity space and has the property of general covariance. The
corresponding effective currents and satisfy the
Hamilton-Jacobi equation for a massless particle moving in the gravitational
field. These currents are calculated explicitly for the shock wave-like fields
and a variation principle for them is formulated. As an application, we
reproduce the effective lagrangian for the multi-regge processes in gravity
together with the graviton Regge trajectory in the leading logarithmic
approximation with taking into account supersymmetric contributions.Comment: 39 page
Effective action for reggeized gluons, classical gluon field of relativistic color charge and color glass condensate approach
We discuss application of formalism of small- effective action for
reggeized gluons, \cite{Gribov,LipatovEff,BFKL}, for the calculation of
classical gluon field of relativistic color charge, similarly to that done in
CGC approach of \cite{Venug,Kovner}. The equations of motion with the reggeon
fields are solved in LO and NLO approximations and new solutions are found. The
results are compared to the calculations performed in the CGC framework and it
is demonstrated that the LO CGC results for the classical field are reproduced
in our calculations. Possible applications of the NLO solution in the effective
action and CGC frameworks are discussed as well.Comment: 15 page
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