387 research outputs found
Transversality of the logarithmic divergences in the Classical Finite Temperature SU(N) Self-Energy
We show that the logarithmic divergences that appear in the classical
approximation of the finite temperature SU(N) self-energy are transverse. We
use the Ward identities in linear gauges and the fact that the superficial
degree of divergence d of a classical diagram only depends on the number of
loops l via d=2-l. We comment on the relevance of this result to the
construction of a low-energy effective theory beyond HTLs.Comment: 5 pages, 1 figure, REVTE
Asymmetric Chern-Simons number diffusion from CP-violation
We study Chern-Simons number diffusion in a SU(2)-Higgs model with CP-odd dimension-eight operators. We find that the thermal average of the magnitude of the velocity of the Chern-Simons number depends on the direction of the velocity. This implies that the distribution function of the Chern-Simons number will develop an asymmetry. It is argued that this asymmetry manifests itself through a linear growth of the expectation value of the third power of the Chern-Simons number. This linear behavior of the third power of a coordinate of a periodic direction is verified by a numerical solution of a one-dimensional Langevin equation. Further, we make some general remarks on thermal averages and on the possibility of the generation of the baryon asymmetry in a non-equilibrium situation due to asymmetric diffusion of the Chern-Simons number
Ward Identities for the 2PI effective action in QED
We study the issue of symmetries and associated Ward-like identities in the
context of two-particle-irreducible (2PI) functional techniques for abelian
gauge theories. In the 2PI framework, the -point proper vertices of the
theory can be obtained in various different ways which, although equivalent in
the exact theory, differ in general at finite approximation order. We derive
generalized (2PI) Ward identities for these various -point functions and
show that such identities are exactly satisfied at any approximation order in
2PI QED. In particular, we show that 2PI-resummed vertex functions, i.e.
field-derivatives of the so-called 2PI-resummed effective action, exactly
satisfy standard Ward identities. We identify another set of -point
functions in the 2PI framework which exactly satisfy the standard Ward
identities at any approximation order. These are obtained as field-derivatives
of the two-point function \bcG^{-1}[\phi], which defines the extremum of the
2PI effective action. We point out that the latter is not constrained by the
underlying symmetry. As a consequence, the well-known fact that the
corresponding gauge-field polarization tensor is not transverse in momentum
space for generic approximations does not constitute a violation of (2PI) Ward
identities. More generally, our analysis demonstrates that approximation
schemes based on 2PI functional techniques respect all the Ward identities
associated with the underlying abelian gauge symmetry. Our results apply to
arbitrary linearly realized global symmetries as well.Comment: 33 pages, 2 figure
Non-equilibrium dynamics of a Bose-Einstein condensate in an optical lattice
The dynamical evolution of a Bose-Einstein condensate trapped in a
one-dimensional lattice potential is investigated theoretically in the
framework of the Bose-Hubbard model. The emphasis is set on the
far-from-equilibrium evolution in a case where the gas is strongly interacting.
This is realized by an appropriate choice of the parameters in the Hamiltonian,
and by starting with an initial state, where one lattice well contains a
Bose-Einstein condensate while all other wells are empty. Oscillations of the
condensate as well as non-condensate fractions of the gas between the different
sites of the lattice are found to be damped as a consequence of the collisional
interactions between the atoms. Functional integral techniques involving
self-consistently determined mean fields as well as two-point correlation
functions are used to derive the two-particle-irreducible (2PI) effective
action. The action is expanded in inverse powers of the number of field
components N, and the dynamic equations are derived from it to next-to-leading
order in this expansion. This approach reaches considerably beyond the
Hartree-Fock-Bogoliubov mean-field theory, and its results are compared to the
exact quantum dynamics obtained by A.M. Rey et al., Phys. Rev. A 69, 033610
(2004) for small atom numbers.Comment: 9 pages RevTeX, 3 figure
Renormalized Finite Temperature phi^4 theory from the 2PI Effective Action
We present an analytical and numerical study of scalar phi^4 theory at finite
temperature with a renormalized 2-loop truncation of the 2PI effective action.Comment: 4 pages. Presented at International Conference on Strong and
Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200
Non-perturbative construction of counterterms for 2PI-approximation
A concise method is presented for the non-perturbative computation of the
counterterms renormalising 2PI-actions. The procedure is presented for a real
scalar field up to lambda^2 order in the skeleton truncation of Gamma_2PI with
respect to the self-coupling, and in a constant symmetry breaking background.
The method is easily generalizable to field theories with arbitrary global
symmetry.Comment: 4 pages, poster presented at Strong and Electroweak Matter
(SEWM2008), Amsterdam,August 25-29 200
Update of Albacore tag release-recapture information in the North-Atlantic and Mediterranean for the period 1968-1999
This paper updates and completes the ICCAT database on albacore tag release–recapture from the North Atlantic including the Mediterranean Sea. In this revision French tag release–
recapture data from the sixties and seventies is included, as well as additional information
obtained from existing bibliography.Le présent document actualise et complète la base de données de l'ICCAT sur le marquage et la
recapture de germon de l'Atlantique nord, Méditerranée comprise. Cette révision comporte des
données françaises de marquage/recapture des années 1960 et 1970, ainsi que des informations
additionnelles extraites de la bibliographie disponible.En el presente documento se actualiza y completa la base ICCAT de datos de marcadorecaptura
de atún blanco del Atlántico Norte, incluyendo el Mediterráneo. En esta revisión se
incluyen los datos de marcado-recaptura franceses de los años los años sesenta y setenta, asĂ
como otras informaciones procedentes de revisiones bibliográficas
The District Energy-Efficient Retrofitting of Torrelago (Laguna de Duero – Spain)
The urban growth is estimated to reach up the 66 % by 2050 and consequently the need of resources within the cities will increase significantly. This, combined with the 40 % of energy consumption and 36 % of CO2 emissions of the building sector, makes necessary to accelerate the transition towards more sustainable cities. The CITyFiED project contributes to this transition, aiming to develop an innovative and holistic methodological approach for energy-efficient district renovation and deliver three large scale demonstration cases in the cities of Lund (Sweden), Laguna de Duero (Spain) and Soma (Turkey). CITyFiED methodology consists of several phases that ease the decision-making tasks towards the district renovation, considering the energy efficiency as the main pillar and local authorities as clients. For the case of Torrelago district (Spain) the intervention consists of a set of energy conservative measures including the facÄ…de retrofitting of 143.025 m2 of living space in 31 twelve-storey buildings; the renovation of the district heating network with a new biomass thermal plant; the integration of renewable energy sources, including a micro-cogeneration system, and the installation of individual smart meters. After the renovation action, one-year monitoring campaign is ongoing. The CITyFiED monitoring platform will collect information from the energy systems and deliver environmental, technical, economic and social key performance indicators by March 2019. At the end of the project the achievement of the predefined goals will be verified: Up to 36 % of energy saving and 3,429 tons-CO2/yr emissions saving covering the 59,4 % of the energy consumption with renewable sources.The research and results presented in this paper evolve from activities related to the CITyFiED project, which has received funding from the European Commission under the Grant Agreement no. 609129. This article is the result of cooperative research work of many experts from various countries and we would like to gratefully acknowledge the rest of the CITyFiED partners
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