687 research outputs found
Sudden interaction quench in the quantum sine-Gordon model
We study a sudden interaction quench in the weak-coupling regime of the
quantum sine-Gordon model. The real time dynamics of the bosonic mode
occupation numbers is calculated using the flow equation method. While we
cannot prove results for the asymptotic long time limit, we can establish the
existence of an extended regime in time where the mode occupation numbers relax
to twice their equilibrium values. This factor two indicates a non-equilibrium
distribution and is a universal feature of weak interaction quenches. The
weak-coupling quantum sine-Gordon model therefore turns out to be on the
borderline between thermalization and non-thermalization.Comment: 18 pages, 4 figures, published in New Journal of Physic
NLO jet production in k_T factorization
We discuss the inclusive production of jets in the central region of rapidity
in the context of k_T-factorization at next-to-leading order (NLO).
Calculations are performed in the Regge limit making use of the NLO BFKL
results. We introduce a jet cone definition and carry out a proper phase--space
separation into multi-Regge and quasi-multi-Regge kinematic regions. We discuss
two situations: scattering of highly virtual photons, which requires a
symmetric energy scale to separate impact factors from the gluon Green's
function, and hadron-hadron collisions, where a non-symmetric scale choice is
needed.Comment: 7 pages, 1 figure, prepared for the 12th International Conference on
Elastic and Diffractive Scattering, DESY, Hamburg, 21-25 May 200
Variational approach to the excitonic phase transition in graphene
We analyze the Coulomb interacting problem in undoped graphene layers by
using an excitonic variational ansatz. By minimizing the energy, we derive a
gap equation which reproduces and extends known results. We show that a full
treatment of the exchange term, which includes the renormalization of the Fermi
velocity, tends to suppress the phase transition by increasing the critical
coupling at which the excitonic instability takes place.Comment: 4 page
W-boson production with large transverse momentum at the LHC
We study W-boson production with large transverse momentum, Q_T, in pp
collisions at the LHC. We calculate the complete NLO corrections and the
soft-gluon NNLO corrections to the differential cross section. The NLO
corrections are large but they do not reduce the scale dependence relative to
LO, while the NNLO soft-gluon corrections, although small, significantly reduce
the scale dependence and thus provide a more stable result.Comment: 5 pages, 3 figures, presented at the XIV International Workshop on
Deep Inelastic Scattering (DIS 2006), Tsukuba, Japan, April 20-24, 200
Gluon Regge trajectory at two loops from Lipatov's high energy effective action
We present the derivation of the two-loop gluon Regge trajectory using
Lipatov's high energy effective action and a direct evaluation of Feynman
diagrams. Using a gauge invariant regularization of high energy divergences by
deforming the light-cone vectors of the effective action, we determine the
two-loop self-energy of the reggeized gluon, after computing the master
integrals involved using the Mellin-Barnes representations technique. The
self-energy is further matched to QCD through a recently proposed subtraction
prescription. The Regge trajectory of the gluon is then defined through
renormalization of the reggeized gluon propagator with respect to high energy
divergences. Our result is in agreement with previous computations in the
literature, providing a non-trivial test of the effective action and the
proposed subtraction and renormalization framework.Comment: 22 page
The quark induced Mueller-Tang jet impact factor at next-to-leading order
We present the NLO corrections for the quark induced forward production of a
jet with an associated rapidity gap. We make use of Lipatov's QCD high energy
effective action to calculate the real emission contributions to the so-called
Mueller-Tang impact factor. We combine them with the previously calculated
virtual corrections and verify ultraviolet and collinear finiteness of the
final result.Comment: 29 pages, many figure
Dijet Production at Large Rapidity Separation in N=4 SYM
Ratios of azimuthal angle correlations between two jets produced at large
rapidity separation are studied in the N=4 super Yang-Mills theory (MSYM). It
is shown that these observables, which directly prove the SL(2,C) symmetry
present in gauge theories in the Regge limit, exhibit an excellent perturbative
convergence. They are compared to those calculated in QCD for different
renormalization schemes concluding that the momentum-substraction (MOM) scheme
with the Brodsky-Lepage-Mackenzie (BLM) scale-fixing procedure captures the
bulk of the MSYM results.Comment: 13 pages, 7 figure
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