Accueil >
Production scientifique
|
|
Immirzi parameter and fermions with non-minimal coupling
Auteur(s): Alexandrov S.
(Article) Publié:
Classical And Quantum Gravity, vol. 25 p.145012 (2008)
Texte intégral en Openaccess :
Ref HAL: hal-00264039_v1
Ref Arxiv: 0802.1221
DOI: 10.1088/0264-9381/25/14/145012
WoS: 000257326100014
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
42 Citations
Résumé: We clarify the role played by the Immirzi parameter in classical gravity coupled to fermions. Considering the general non-minimal coupling, we show that, although the torsion depends explicitly on the Immirzi parameter, in a suitable parametrization the effective action obtained by integrating out the spin-connection is independent of it. Thus the Immirzi parameter is not detectable in classical theory even after coupling of fermions.
|
|
|
Spin foam model from canonical quantization
Auteur(s): Alexandrov S.
(Article) Publié:
Physical Review D, vol. 77 p.024009 (2007)
Texte intégral en Openaccess :
Ref HAL: in2p3-00152760_v1
Ref Arxiv: 0705.3892
DOI: 10.1103/PhysRevD.77.024009
WoS: 000252864000059
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
31 Citations
Résumé: We suggest a modification of the Barrett-Crane spin foam model of 4-dimensional Lorentzian general relativity motivated by the canonical quantization. The starting point is Lorentz covariant loop quantum gravity. Its kinematical Hilbert space is found as a space of the so-called projected spin networks. These spin networks are identified with the boundary states of a spin foam model and provide a generalization of the unique Barrette-Crane intertwiner. We propose a way to modify the Barrett-Crane quantization procedure to arrive at this generalization: the $B$ field (bi-vectors) should be promoted not to generators of the gauge algebra, but to their certain projection. The modification is also justified by the canonical analysis of Plebanski formulation. Finally, we compare our construction with other proposals to modify the Barret-Crane model.
Commentaires: 15 pages
|
|
|
Quantum covariant c-map
Auteur(s): Alexandrov S.
(Article) Publié:
Journal Of High Energy Physics, vol. 0705 p.094 (2007)
Texte intégral en Openaccess :
Ref HAL: in2p3-00134331_v1
Ref Arxiv: hep-th/0702203
DOI: 10.1088/1126-6708/2007/05/094
WoS: 000247030800094
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
24 Citations
Résumé: We generalize the results of hep-th/0701214 about the covariant c-map to include the perturbative quantum corrections. We also perform explicitly the superconformal quotient from the hyperkahler cone obtained by the quantum c-map to the quaternion-Kahler space, which is the moduli space of hypermultiplets. As a result, the perturbatively corrected metric on the moduli space is found in a simplified form comparing to the expression known in the literature.
Commentaires: 15 pages
|
|
|
Instantons from quaternionic geometry
Auteur(s): Alexandrov S.
Conférence invité: "Affine Hecke algebras, the Langlands program, conformal field theory and matrix models (Lumini, FR, 2006-07-03)
Ref HAL: hal-00285448_v1
Exporter : BibTex | endNote
Résumé: We determine the one-instanton corrections to the universal hypermultiplet moduli space coming both from Euclidean membranes and NS-fivebranes wrapping the cycles of a (rigid) Calabi-Yau threefold. These corrections are completely encoded by a single function characterizing a generic four-dimensional quaternion-Kahler metric without isometries. We give explicit solutions for this function describing all one-instanton corrections, including the fluctuations around the instanton to all orders in the string coupling constant. In the semi-classical limit these results are in perfect agreement with previous supergravity calculations.
|
|
|
Plebanski Theory and Covariant Canonical Formulation
Auteur(s): Alexandrov S., Buffenoir E., Roche P.
(Article) Publié:
Classical And Quantum Gravity, vol. 24 p.2809-2824 (2007)
Texte intégral en Openaccess :
Ref HAL: in2p3-00134335_v1
Ref Arxiv: gr-qc/0612071
DOI: 10.1088/0264-9381/24/11/003
WoS: 000246688400005
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
27 Citations
Résumé: We establish an equivalence between the Hamiltonian formulation of the Plebanski action for general relativity and the covariant canonical formulation of the Hilbert-Palatini action. This is done by comparing the symplectic structures of the two theories through the computation of Dirac brackets. We also construct a shifted connection with simplified Dirac brackets, playing an important role in the covariant loop quantization program, in the Plebanski framework. Implications for spin foam models are also discussed.
Commentaires: 18 pages
|
|
|
Membrane and fivebrane instantons from quaternionic geometry
Auteur(s): Alexandrov S., Saueressig F., Vandoren S.
(Article) Publié:
Journal Of High Energy Physics, vol. 0609 p.040 (2006)
Texte intégral en Openaccess :
Ref HAL: in2p3-00134337_v1
Ref Arxiv: hep-th/0606259
DOI: 10.1088/1126-6708/2006/09/040
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We determine the one-instanton corrections to the universal hypermultiplet moduli space coming both from Euclidean membranes and NS-fivebranes wrapping the cycles of a (rigid) Calabi-Yau threefold. These corrections are completely encoded by a single function characterizing a generic four-dimensional quaternion-Kahler metric without isometries. We give explicit solutions for this function describing all one-instanton corrections, including the fluctuations around the instanton to all orders in the string coupling constant. In the semi-classical limit these results are in perfect agreement with previous supergravity calculations.
Commentaires: 32 pages
|