16,292 research outputs found
Production of q bar-q Pairs in Proton-Nucleus Collisions at High Energies
We calculate production of quark-antiquark pairs in high energy
proton-nucleus collisions both in the quasi-classical approximation of
McLerran-Venugopalan model and including quantum small- evolution. The
resulting production cross section is explicitly expressed in terms of
Glauber-Mueller multiple rescatterings in the classical case and in terms of
dipole-nucleus scattering amplitude in the quantum evolution case. We
generalize the result of one of us (K.T.) beyond the aligned jet
configurations. We expand on the earlier results of Blaizot, Gelis and
Venugopalan by deriving quark production cross section including quantum
evolution corrections in rapidity intervals both between the quarks and the
target and between the quarks and the projectile.Comment: 18 pages, 3 figures; typos corrected, discussion extende
Numerical Investigation of Graph Spectra and Information Interpretability of Eigenvalues
We undertake an extensive numerical investigation of the graph spectra of
thousands regular graphs, a set of random Erd\"os-R\'enyi graphs, the two most
popular types of complex networks and an evolving genetic network by using
novel conceptual and experimental tools. Our objective in so doing is to
contribute to an understanding of the meaning of the Eigenvalues of a graph
relative to its topological and information-theoretic properties. We introduce
a technique for identifying the most informative Eigenvalues of evolving
networks by comparing graph spectra behavior to their algorithmic complexity.
We suggest that extending techniques can be used to further investigate the
behavior of evolving biological networks. In the extended version of this paper
we apply these techniques to seven tissue specific regulatory networks as
static example and network of a na\"ive pluripotent immune cell in the process
of differentiating towards a Th17 cell as evolving example, finding the most
and least informative Eigenvalues at every stage.Comment: Forthcoming in 3rd International Work-Conference on Bioinformatics
and Biomedical Engineering (IWBBIO), Lecture Notes in Bioinformatics, 201
Can the envisaged reductions of fossil fuel CO2 emissions be detected by atmospheric observations?
The lower troposphere is an excellent receptacle, which integrates anthropogenic greenhouse gases emissions over large areas. Therefore, atmospheric concentration observations over populated regions would provide the ultimate proof if sustained emissions changes have occurred. The most important anthropogenic greenhouse gas, carbon dioxide (CO2), also shows large natural concentration variations, which need to be disentangled from anthropogenic signals to assess changes in associated emissions. This is in principle possible for the fossil fuel CO2 component (FFCO2) by high-precision radiocarbon (14C) analyses because FFCO2 is free of radiocarbon. Long-term observations of 14CO2 conducted at two sites in south-western Germany do not yet reveal any significant trends in the regional fossil fuel CO2 component. We rather observe strong inter-annual variations, which are largely imprinted by changes of atmospheric transport as supported by dedicated transport model simulations of fossil fuel CO2. In this paper, we show that, depending on the remoteness of the site, changes of about 7–26% in fossil fuel emissions in respective catchment areas could be detected with confidence by high-precision atmospheric 14CO2 measurements when comparing 5-year averages if these inter-annual variations were taken into account. This perspective constitutes the urgently needed tool for validation of fossil fuel CO2 emissions changes in the framework of the Kyoto protocol and successive climate initiatives
Study of non-collinear parton dynamics in the prompt photon photoproduction at HERA
We investigate the prompt photon photoproduction at HERA within the framework
of kt-factorization QCD approach. Our consideration is based on the off-shell
matrix elements for the underlying partonic subprocesses. The unintegrated
parton densities in a proton and in a photon are determined using the
Kimber-Martin-Ryskin (KMR) prescription. Additionally, we use the CCFM-evolved
unintegrated gluon as well as valence and sea quark distributions in a proton.
A conservative error analisys is performed. Both inclusive and associated with
the hadronic jet production rates are investigated. The theoretical results are
compared with the recent experimental data taken by the H1 and ZEUS
collaborations. We study also the specific kinematical properties of the
photon-jet system which are strongly sensitive to the transverse momentum of
incoming partons. Using the KMR scheme, the contribution from the quarks
emerging from the earlier steps of the parton evolution is estimated and found
to be of 15 - 20 approximately.Comment: 22 pages, 13 figures, 2 tabl
Elliptic Schlesinger system and Painlev{\'e} VI
We construct an elliptic generalization of the Schlesinger system (ESS) with
positions of marked points on an elliptic curve and its modular parameter as
independent variables (the parameters in the moduli space of the complex
structure). ESS is a non-autonomous Hamiltonian system with pair-wise commuting
Hamiltonians. The system is bihamiltonian with respect to the linear and the
quadratic Poisson brackets. The latter are the multi-color generalization of
the Sklyanin-Feigin-Odeskii classical algebras. We give the Lax form of the
ESS. The Lax matrix defines a connection of a flat bundle of degree one over
the elliptic curve with first order poles at the marked points.
The ESS is the monodromy independence condition on the complex structure for
the linear systems related to the flat bundle.
The case of four points for a special initial data is reduced to the
Painlev{\'e} VI equation in the form of the Zhukovsky-Volterra gyrostat,
proposed in our previous paper.Comment: 16 pages; Dedicated to the centenary of the publication of the
Painleve VI equation in the Comptes Rendus de l'Academie des Sciences de
Paris by Richard Fuchs in 190
Inclusive Gluon Production In High Energy Onium-Onium Scattering
We calculate the inclusive single-gluon production cross section in high
energy onium-onium scattering including pomeron loop effects. The resulting
inclusive cross section is given by the k_T-factorization formula with one of
the unintegrated gluon distribution functions depending on the total
onium-onium scattering cross section, which includes all pomeron loops and has
to be found independently. We discuss the limits of applicability of our result
and argue that they are given by the limits of applicability of pomeron loop
resummation approach. Since the obtained k_T-factorization formula is infrared
divergent we conclude that, in order to consistently calculate the
(infrared-finite) gluon production cross section in onium-onium scattering, one
has to include corrections going beyond the pomeron loop approximation.Comment: 20 pages, 6 figures; v2: version accepted to Phys. Rev. D, minor
corrections include
Signature for the Shape of the Universe
If the universe has a nontrivial shape (topology) the sky may show multiple
correlated images of cosmic objects. These correlations can be couched in terms
of distance correlations. We propose a statistical quantity which can be used
to reveal the topological signature of any Robertson-Walker (RW) spacetime with
nontrivial topology. We also show through computer-aided simulations how one
can extract the topological signatures of flat, elliptic, and hyperbolic RW
universes with nontrivial topology.Comment: 11 pages, 3 figures, LaTeX2e. This paper is a direct ancestor of
gr-qc/9911049, put in gr-qc archive to make it more accessibl
Solomonoff Induction Violates Nicod's Criterion
Nicod's criterion states that observing a black raven is evidence for the
hypothesis H that all ravens are black. We show that Solomonoff induction does
not satisfy Nicod's criterion: there are time steps in which observing black
ravens decreases the belief in H. Moreover, while observing any computable
infinite string compatible with H, the belief in H decreases infinitely often
when using the unnormalized Solomonoff prior, but only finitely often when
using the normalized Solomonoff prior. We argue that the fault is not with
Solomonoff induction; instead we should reject Nicod's criterion.Comment: ALT 201
Gapless layered three-dimensional fractional quantum Hall states
Using the parton construction, we build a three-dimensional (3D) multilayer
fractional quantum Hall state with average filling \nu = 1/3 per layer that is
qualitatively distinct from a stacking of weakly coupled Laughlin states. The
state supports gapped charge e/3 fermionic quasiparticles that can propagate
both within and between the layers, in contrast to the quasiparticles in a
multilayer Laughlin state which are confined within each layer. Moreover, the
state has gapless neutral collective modes, a manifestation of an emergent
"photon", which is minimally coupled to the fermionic quasiparticles. The
surface sheath of the multilayer state resembles a chiral analog of the
Halperin-Lee-Read state, which is protected against gap forming instabilities
by the topological character of the bulk 3D phase. We propose that this state
might be present in multilayer systems in the "intermediate tunneling regime",
where the interlayer tunneling strength is on the same order as the Coulomb
energy scale. We also find that the parton construction leads to a candidate
state for a bilayer \nu = 1/3 system in the intermediate tunneling regime. The
candidate state is distinct from both a bilayer of \nu=1/3 Laughlin states and
the single layer \nu = 2/3 state, but is nonetheless a fully gapped fractional
quantum Hall state with charge e/3 anyonic quasiparticles.Comment: 11 pages, 1 figur
Chemical composition of the decaying glasma
The the initial stage of a relativistic heavy ion collision can be described
by a classical color field configuration known as the Glasma. The production of
quark pairs from this background field is then computed nonperturbatively by
numerically solving the Dirac equation in the classical background. The result
seems to point towards an early chemical equilibration of the plasma.Comment: 8 pages, 5 figures, invited talk at Stangeness in Quark Matter 2006
(SQM06), UCLA, March 200
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