411 research outputs found
Numerical tools for the theoretical study of QCD at small x
In this contribution we present the status of two numerical tools designed to
study the small x limit of QCD. The first one is a Monte Carlo simulation of
the BFKL evolution equation. In design of this approach emphasis has been
placed on exploiting the linear behaviour that many variants of the BFKL
evolution possess. This allows us to design a procedure which can be used to
study theoretical and phenomenological aspects of different kernels. The second
one is a semi-analytic approach to study Lipatov's effective action which
describes Reggeon interactions. The study of the properties of this action is
very complicated and we propose using a computational tool to handle the large
amount of non--local vertices and the derivation of higher order corrections.Comment: 7 pages, 3 figures. International Workshop on Diffraction in
High-Energy Physics -DIFFRACTION 2006 - September 5-10 2006 Adamantas, Milos
island, Greec
W production at large transverse momentum at the Large Hadron Collider
We study the production of W bosons at large transverse momentum in pp
collisions at the Large Hadron Collider (LHC). We calculate the complete
next-to-leading order (NLO) corrections to the differential cross section. We
find that the NLO corrections provide a large increase to the cross section
but, surprisingly, do not reduce the scale dependence relative to leading order
(LO). We also calculate next-to-next-to-leading-order (NNLO) soft-gluon
corrections and find that, although they are small, they significantly reduce
the scale dependence thus providing a more stable theoretical prediction.Comment: 12 pages, 7 figure
A comparative study of small x Monte Carlos with and without QCD coherence effects
We compare two Monte Carlo implementations of resummation schemes for the
description of parton evolution at small values of Bjorken x. One of them is
based on the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution equation and
generates fully differential parton distributions in momentum space making use
of reggeized gluons. The other one is based on the
Catani-Ciafaloni-Fiorani-Marchesini (CCFM) partonic kernel where QCD coherence
effects are introduced. It has been argued that both approaches agree with each
other in the x -> 0 limit. We show that this is not the case for azimuthal
angle dependent quantities since at high energies the BFKL approach is
dominated by its zero conformal spin component while the CCFM gluon Green
function receives contributions from all conformal spins even at very small x.Comment: 19 pages, 19 figure
Diffractive photoproduction at large momentum transfer in coherent hadron - hadron interactions at CERN LHC
The vector meson production in coherent hadron-hadron interactions at LHC
energies is studied assuming that the color singlet -channel exchange
carries large momentum transfer. We consider the non-forward solution of the
BFKL equation at high energy and large momentum transfer and estimate the
rapidity distribution and total cross section for the process , where can be a proton or a nucleus. We predict large rates,
which implies that the experimental identification can be feasible at the LHC.Comment: 10 pages, 5 figures, 1 table. Version to be published in Physical
Review
New Generation of MOF-Monoliths Based on Metal Foams
Herein, it has been developed a method to prepare metallic foams starting from Zamak5 (ZnAlCu alloy) with different pore sizes. The Zamak5 metallic foam is designed to serve as a support and metallic precursor of ZIF-8. In this way, composite materials MOF-metal can be prepared, these composites have a large number of application in energy exchange processe such as: adsorption or chemical reactions. Additionally, this method of sythesizing MOFs is environmentally friendly thanks to absence of solvents. Hanerssing the low melting point of the linker, the linker is infiltrated into the foam where the foam and the linker react to form the ZIF-8. In this way we have managed to transform part of the foam into ZIF-8 crystals that remain adhered to the foam. The foams have been characterized and modeled studying the mechanical and electrical properties, finding that both can be predected by various models. Among these, Ashby and Mortensen models for mechanical properties and Ashby and Percolation model for electrical properties stand.The authors would like to acknowledge the financial support from “Ministerio de Ciencia e innovación” (PID2020-116998RB-I00) and Ministerio de Economía y Empresa (MAT2017-86992-R) and action Mobility of Alicante University
f-Sum Rule and Unconventional Spectral Weight Transfer in Graphene
We derive and analyze the f-sum rule for a two-dimensional (2D) system of
interacting electrons whose behavior is described by the Dirac equation. We
apply the sum rule to analyze the spectral weight transfer in graphene within
different approximations discussed in the literature. We find that the sum rule
is generically dominated by inter-band transitions while other excitations
produce sub-leading behavior. The f-sum rule provides strong constraints for
theories of interacting electrons in graphene.Comment: 10 pages, 3 figures; typos corrected, references adde
Nearly Space-Filling Fractal Networks of Carbon Nanopores
URL:http://link.aps.org/doi/10.1103/PhysRevLett.88.115502
DOI:10.1103/PhysRevLett.88.115502Small-angle x-ray scattering, nitrogen adsorption, and scanning tunneling microscopy show that a series of activated carbons host an extended fractal network of channels with dimension Dp = 2.8-3.0 (pore fractal), channel width 15-20Å (lower end of scaling), network diameter 3000-3400Å (upper end of scaling), and porosity of 0.3-0.6. We interpret the network as a stack of quasiplanar invasion percolation clusters, formed by oxidative removal of walls between closed voids of diameter of ∼10Å and held in registry by fibrils of the biological precursor, and point out unique applications.This work was supported by the Petroleum Research Fund, Grant No. 30602-AC9,5 (P. P.); the Department of Energy, Contracts No. W-7405-ENG-36 (P. P.) and No. DE-AC04-00A185000 (T. P. R.); and the Ceramic and Non-Metallic Materials Program at AFOSR (W. P. H.)
Quantum quench dynamics of the sine-Gordon model in some solvable limits
In connection with the the thermalization problem in isolated quantum
systems, we investigate the dynamics following a quantum quench of the
sine-Gordon model in the Luther-Emery and the semiclassical limits. We consider
the quench from the gapped to the gapless phase as well as reversed one. By
obtaining analytic expressions for the one and two-point correlation functions
of the order parameter operator at zero-temperature, the manifestations of
integrability in the absence of thermalization in the sine-Gordon model are
studied. It is thus shown that correlations in the long time regime after the
quench are well described by a generalized Gibbs ensemble. We also consider the
case where the system is initially in contact with a reservoir at finite
temperature. The possible relevance of our results to current and future
experiments with ultracold atomic systems is also critically considered.Comment: 21 pages, no figures. To appear in New J. Phys
One-dimensional fermionic systems after interaction quenches and their description by bosonic field theories
We show that the dynamics of quenches in one dimension far off equilibrium
can be described by power laws, but with exponents differing from the fully
renormalized ones at lowest energies. Instead they depend on the initial state
and its excitation energy. Furthermore, we found that for quenches to strong
interactions unexpected similarities between systems in one and in infinite
dimensions occur, indicating the dominance of local processes.Comment: This is a distinctly revised version which is focussed on the
description of the dynamics by bosonization technique
Gauge fields, ripples and wrinkles in graphene layers
We analyze elastic deformations of graphene sheets which lead to effective
gauge fields acting on the charge carriers. Corrugations in the substrate
induce stresses, which, in turn, can give rise to mechanical instabilities and
the formation of wrinkles. Similar effects may take place in suspended graphene
samples under tension.Comment: contribution to the special issue of Solid State Communications on
graphen
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