Ref HAL: hal-00494258_v1
Ref Arxiv: 1004.3815
DOI: 10.1103/PhysRevC.81.065205
WoS: 000278606400001
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39 Citations
Résumé:

The optimized perturbation theory (OPT) method is applied to the SU(2) version of the Nambu-Jona-Lasinio (NJL) model both at zero and at finite temperature and/or density. At the first nontrivial order, the OPT exhibits a class of 1/N-c corrections which produce nonperturbative results that go beyond the standard large-N-c or mean-field approximation. The consistency of the OPT method with the Goldstone theorem at this order is established, and appropriate OPT values of the basic NJL (vacuum) parameters are obtained by matching the pion mass and decay constant consistently. Deviations from standard large-N-c relations induced by OPT at this order are derived, for example, for the Gell-Mann-Oakes-Renner relation. Next, the results for the critical quantities and the phase diagram of the model, as well as a number of other thermodynamical quantities of interest, are obtained with OPT and then contrasted with the corresponding results at large N-c.

Commentaires: 29 pages, 20 figures, revtex

Ref HAL: hal-00430392_v1
Ref Arxiv: 0902.0377
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Proceedings of ISMD08

Commentaires: Edited by: J. Bartels, K. Borras, G. Gustafson, H. Jung, K. Kutak, S. Levonian, and J. Mnich

Ref HAL: hal-00285067_v1
Ref Arxiv: 0804.2675
DOI: 10.1103/PhysRevB.77.205109
WoS: 000256971800026
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27 Citations
Résumé:

The Optimized Perturbation Theory (OPT) method, at finite temperature and finite chemical potential, is applied to the field theory model for polyacetylene. The critical dopant concentration in trans-polyacetylene is evaluated and compared with the available experimental data and with previous calculations. The results obtained within the OPT go beyond the standard mean field (or large-N) approximation (MFA) by explicitly including finite N effects. A critical analysis of the possible theoretical prescriptions to implement and interpret these corrections to the mean field results, given the available data, is given. For typical temperatures probed in the laboratory, our results show that the critical dopant concentration is only weakly affected by thermal effects.

Ref HAL: hal-00546813_v1
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We use the linear 5 expansion, or optimized perturbation theory, to evaluate the effective potential for the two dimensional Gross-Neveu model at finite temperature and density obtaining analytical equations for the critical temperature, chemical potential and fermionic mass which include finite N corrections. Our results seem to improve over the traditional large-N predictions.

Ref HAL: hal-00394236_v1
DOI: 10.1142/S0218301307008446
WoS: 000252267800014
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1 Citation
Résumé:

We study the phase diagram of the 3d massless Gross–Neveu model with different numbers of fermionic species, N. Using the Optimized Perturbation Theory technique, the free energy is evaluated at finite temperature and chemical potential. The analytical results allow us to calculate critical quantities for any value of N and, in the present work, we choose de values N = 1,3,4,10. In addition, we determine the evolution of the tricritical points, in the temperature versus chemical potential plane for these different values of N.

Ref HAL: hal-00285176_v1
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On donne une introduction théorique aux bases de la supersymétrie ensuite appliquées à la construction du modéle supersymétrique standard minimal. On discute ensuite quelques contraintes théoriques et expérimentales actuelles.

Commentaires: conférence plénière invitée

Ref HAL: in2p3-00252151_v1
Ref Arxiv: 0712.3151
DOI: 10.1103/PhysRevD.77.055014
WoS: 000254544200071
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6 Citations
Résumé:

We study the complementarity between the indirect detection of dark matter with gamma-rays in H.E.S.S. and the supersymmetry searches with ATLAS at the Large Hadron Collider in the Focus Point region within the mSUGRA framework. The sensitivity of the central telescope of the H.E.S.S. II experiment with an energy threshold of ~ 20 GeV is investigated. We show that the detection of gamma-ray fluxes of O(10^-12) cm-2s-1 with H.E.S.S. II covers a substantial part of the Focus Point region which may be more difficult for LHC experiments. Despite the presence of multi-TeV scalars, we show that LHC will be sensitive to a complementary part of this region through three body NLSP leptonic decays. This interesting complementarity between H.E.S.S. II and LHC searches is further highlighted in terms of the gluino mass and the two lightest neutralino mass difference.

Commentaires: 11 pages, 6 figures, accepted for publication in Phys. Rev. D on February 7, 2008 (slight modifications: references updated and text improved)