683 research outputs found
Testing for convergence in stock markets: A non-linear factor approach
This paper applies the Phillips and Sul (2007) method to test for convergence in stock returns to an extensive dataset including monthly stock price indices for five EU countries (Germany, France, the Netherlands, Ireland and the UK) as well as the US over the period 1973-2008. We carry out the analysis on both sectors and individual industries within sectors. As a first step, we use the Stock and Watson (1998) procedure to filter the data in order to extract the long-run component of the series; then, following Phillips and Sul (2007), we estimate the relative transition parameters. In the case of sectoral indices we find convergence in the middle of the sample period, followed by divergence, and detect four (two large and two small) clusters. The analysis at a disaggregate, industry level again points to convergence in the middle of the sample, and subsequent divergence, but a much larger number of clusters is now found. Splitting the cross-section into two subgroups including Euro area countries, the UK and the US respectively, provides evidence of a global
convergence/divergence process not obviously influenced by EU policies
BFKL predictions for inclusive three jet production at the LHC
We define new observables sensitive to BFKL dynamics in the context of
multijet production at the large hadron collider (LHC). We propose the study of
the inclusive production of three jets well separated in rapidity from each
other, with two of them being very forward. We show that the tagging of a third
jet in the central region of rapidity allows for a very strong test of the BFKL
formalism. In particular, we have studied two projections on azimuthal angles
for the differential cross section which allow for the definition of many
different observables whose behavior when varying the and rapidity of the
central jet is a distinct signal of BFKL dynamics. In order to reduce the
theoretical uncertainties and influence of higher order corrections, we propose
the study of ratios of correlation functions of products of cosines of
azimuthal angle differences among the tagged jets.Comment: 11 pages, 2 figure
Brodsky-Lepage-Mackenzie optimal renormalization scale setting for semihard processes
The Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach for the investigation of semihard processes is plagued by large next-to-leading corrections, both in the kernel of the universal BFKL Green's function and in the process-dependent impact factors, as well as by large uncertainties in the renormalization scale setting. All that calls for an optimization procedure of the perturbative series. In this respect, one of the most common methods is the Brodsky-Lepage-Mackenzie (BLM) one, which eliminates the renormalization scale ambiguity by absorbing the nonconformal β0 terms into the running coupling. In this paper, we apply the BLM scale setting procedure directly to the amplitudes (cross sections) of several semihard processes. We show that, due to the presence of β0 terms in the next-to-leading expressions for the impact factors, the optimal renormalization scale is not universal but depends both on the energy and on the type of process in questionD. I. thanks the Dipartimento di Fisica dell’Università della Calabria and the Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza for the warm hospitality and financial support. The work of D. I. was also supported in part by the Russian Foundation for Basic Research via Grant No. RFBR-13-02-00695-a. The work of B. M. was supported by the European Commission, European Social Fund and Calabria Region, who disclaim any liability for any use made of the information provided in this paper. B. M. thanks the Sobolev Institute of Mathematics of Novosibirsk for warm hospitality during the preparation of this wor
A study of the diffusion pattern in N=4 SYM at high energies
In the context of evolution nequations and scattering amplitudes in the high energy limit of the N=4 super Yang–Mills theory we investigate in some detail the BFKL gluon Green function at next-to-leading order. In particular, we study its collinear be havi or in term so fan expansion in different angular components. We also perform a Monte Carlo simulation of the different final states contributing to such a Green function and construct the diffusion pattern in to in frared and ultraviolet modes and multiplicity distributions, making emphasis in separating the gluon contributions from those of scalars and gluinos. We find that the combined role of the non-gluonic degree sof freedom is to improve the collinear behavior and reduce the diffusion in to ultraviolet regions while not having any effect ont heaver age multiplicities or diffusion in to the in frared. In terms of growth with energy,the non-zero conformal spin components are mainly driven by the gluon terms in the BFKLkernel. Forze rocon formal spin (Pomeron) the effect the scalar and gluino sectors is to dramatically push the Green function towards higher valuesF.C. thanks the Instituto de Física Teórica UAM/CSIC for the warm hospitality.Weack now ledge partial support from the European Comission under contract LHC PhenoNet (PITN-GA-2010-264564), the Comunidad de Madrid through HEPHACOSS2009/ESP-1473, and MICINN (FPA2010-17747) and Spanish MINECOs Centro de Excelencia Severo Ochoa Programme under grant SEV-2012-0249.TheworkofF.C.was supported by EuropeanCommission, European Social Fund and Calabria Region,that disclaim many lia-bility for the use that can be done of the information provided in this Letter.G.C. thanks the support from the Research Executive Agency(REA)of the European Union under the Grant Agree ment number PIEF-GA-2011-298582 and by MICINN (FPA2011-23778,FPA2007-60323 and CSD2007-00042CPAN
Corrections to the generalized vector dominance due to diffractive rho_3 production
The idea of the vector dominance is still in use in various analyses of
experimental data of photon-hadron reactions. It makes sense, therefore, to
recast results of microscopic calculations of such reactions in this language.
Here we present the diffractive DIS production as a specific
correction to the generalized vector dominance. We perform a coupled channel
analysis of spin-orbital excitations in diffractive photoproduction and
reiterate the point that rho_3 in diffractive DIS will be sensitive to a novel
aspect of diffraction.Comment: 12 pages, 2 figure
Interplay of the electronic and lattice degrees of freedom in A_{1-x}Fe_{2-y}Se_{2} superconductors under pressure
The local structure and electronic properties of RbFeSe
are investigated by means of site selective polarized x-ray absorption
spectroscopy at the iron and selenium K-edges as a function of pressure. A
combination of dispersive geometry and novel nanodiamond anvil pressure-cell
has permitted to reveal a step-like decrease in the Fe-Se bond distance at
GPa. The position of the Fe K-edge pre-peak, which is directly
related to the position of the chemical potential, remains nearly constant
until GPa, followed by an increase until GPa. Here, as in
the local structure, a step-like decrease of the chemical potential is seen.
Thus, the present results provide compelling evidence that the origin of the
reemerging superconductivity in FeSe in vicinity of a
quantum critical transition is caused mainly by the changes in the electronic
structure
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