Bernabeu, J., Espinoza, C., & Mavromatos, N. E. (2010). Cosmological constant and local gravity. Phys. Rev. D, 81(8), 084002–7pp.
Abstract: We discuss the linearization of Einstein equations in the presence of a cosmological constant, by expanding the solution for the metric around a flat Minkowski space-time. We demonstrate that one can find consistent solutions to the linearized set of equations for the metric perturbations, in the Lorentz gauge, which are not spherically symmetric, but they rather exhibit a cylindrical symmetry. We find that the components of the gravitational field satisfying the appropriate Poisson equations have the property of ensuring that a scalar potential can be constructed, in which both contributions, from ordinary matter and Lambda > 0, are attractive. In addition, there is a novel tensor potential, induced by the pressure density, in which the effect of the cosmological constant is repulsive. We also linearize the Schwarzschild-de Sitter exact solution of Einstein's equations ( due to a generalization of Birkhoff's theorem) in the domain between the two horizons. We manage to transform it first to a gauge in which the 3-space metric is conformally flat and, then, make an additional coordinate transformation leading to the Lorentz gauge conditions. We compare our non-spherically symmetric solution with the linearized Schwarzschild-de Sitter metric, when the latter is transformed to the Lorentz gauge, and we find agreement. The resulting metric, however, does not acquire a proper Newtonian form in terms of the unique scalar potential that solves the corresponding Poisson equation. Nevertheless, our solution is stable, in the sense that the physical energy density is positive.
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Doring, M., Oset, E., & Meissner, U. G. (2010). Evaluation of the polarization observables I-S and I-C in the reaction gamma p -> pi(0)eta p. Eur. Phys. J. A, 46(2), 315–323.
Abstract: We evaluate the polarization observables I-S and I-C for the reaction gamma p -> pi(0)eta p, using a chiral unitary framework developed earlier. The I-S and I-C observables have been recently measured for the first time by the CBELSA/TAPS Collaboration. The theoretical predictions of I-S and I-C, given for altogether 18 angle-dependent functions, are in good agreement with the measurements. Also, the asymmetry d Sigma/dcos theta evaluated here agrees with the data. We show the importance of the Delta(1700) D-33-resonance and its S-wave decay into eta Delta(1232). The result can be considered as a further confirmation of the dynamical nature of this resonance. At the highest energies, deviations of the predictions from the data start to become noticeable, which leaves room for additional processes and resonances such as a Delta(1940) D-33. We also point out how to further improve the calculation.
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Yamagata-Sekihara, J., & Oset, E. (2010). V P gamma radiative decay of resonances dynamically generated from the vector meson-vector meson interaction. Phys. Lett. B, 690(4), 376–381.
Abstract: We evaluate the radiative decay into a vector, a pseudoscalar and a photon of several resonances dynamically generated from the vector-vector interaction. The process proceeds via the decay of one of the vector components into a pseudoscalar and a photon, which have an invariant mass distribution very different from phase space as a consequence of the two vector structure of the resonances. Experimental work along these lines should provide useful information on the nature of these resonances.
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Lledo, M. A., & Sommovigo, L. (2010). Torsion formulation of gravity. Class. Quantum Gravity, 27(6), 065014–16pp.
Abstract: We explain precisely what it means to have a connection with torsion as a solution of the Einstein equations. While locally the theory remains the same, the new formulation allows for topologies that would have been excluded in the standard formulation of gravity. In this formulation it is possible to couple arbitrary torsion to gauge fields without breaking the gauge invariance.
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Mathieu, V., & Vento, V. (2010). Pseudoscalar glueball and eta-eta ' mixing. Phys. Rev. D, 81(3), 034004–12pp.
Abstract: We have performed a dynamical analysis of the mixing in the pseudoscalar channel with the goal of understanding the existence and behavior of the pseudoscalar glueball. Our philosophy has not been to predict precise values of the glueball mass but to exploit an adequate effective theory to the point of breaking and to analyze which kind of mechanisms restore compatibility with data. Our study has led to analytical solutions which allow a clear understanding of the phenomena. The outcome of our calculation leads to a large mass glueball M-Theta > 2000 MeV, to a large glue content of the eta ', and to mixing angles in agreement with previous numerical studies.
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