1,424 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
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
The World as a Hologram
According to 't Hooft the combination of quantum mechanics and gravity
requires the three dimensional world to be an image of data that can be stored
on a two dimensional projection much like a holographic image. The two
dimensional description only requires one discrete degree of freedom per Planck
area and yet it is rich enough to describe all three dimensional phenomena.
After outlining 't Hooft's proposal I give a preliminary informal description
of how it may be implemented. One finds a basic requirement that particles must
grow in size as their momenta are increased far above the Planck scale. The
consequences for high energy particle collisions are described. The phenomena
of particle growth with momentum was previously discussed in the context of
string theory and was related to information spreading near black hole
horizons. The considerations of this paper indicate that the effect is much
more rapid at all but the earliest times. In fact the rate of spreading is
found to saturate the bound from causality. Finally we consider string theory
as a possible realization of 't Hooft's idea. The light front lattice string
model of Klebanov and Susskind is reviewed and its similarities with the
holographic theory are demonstrated. The agreement between the two requires
unproven but plausible assumptions about the nonperturbative behavior of string
theory. Very similar ideas to those in this paper have been long held by
Charles Thorn.Comment: SU-ITP-94-33, phyzzx, 33 pages and 5 figures (Some typos fixed and
one reference added.
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
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
Analytic properties of high energy production amplitudes in N=4 SUSY
We investigate analytic properties of the six point planar amplitude in N=4
SUSY at the multi-Regge kinematics for final state particles. For inelastic
processes the Steinmann relations play an important role because they give a
possibility to fix the phase structure of the Regge pole and Mandelstam cut
contributions. These contributions have the Moebius invariant form in the
transverse momentum subspace. The analyticity and factorization constraints
allow us to reproduce the two-loop correction to the 6-point BDS amplitude in
N=4 SUSY obtained earlier in the leading logarithmic approximation with the use
of the s-channel unitarity. The exponentiation hypothesis for the remainder
function in the multi-Regge kinematics is also investigated. The 6-point
amplitude in LLA can be completely reproduced from the BDS ansatz with the use
of the analyticity and Regge factorization.Comment: To appear in the proceedings of 16th International Seminar on High
Energy Physics, QUARKS-2010, Kolomna, Russia, 6-12 June, 2010. 15 page
Off-Shell Scattering Amplitudes for WW Scattering and the Role of the Photon Pole
We derive analytic expressions for high energy off-shell scattering
amplitudes of weak vector bosons. They are obtained from six fermion final
states in processes of the type . As an application we reconsider the
unitarity bounds on the Higgs mass. Particular attention is given to the role
of the photon exchange which has not been considered in earlier investigations;
we find that the photon weakens the bound of the Higgs mass.Comment: 16 pages, 8 figure
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
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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