Naked Singularity in a Modified Gravity Theory

The cosmological constant induced by quantum fluctuation of the graviton on a given background is considered as a tool for building a spectrum of different geometries. In particular, we apply the method to the Schwarzschild background with positive and negative mass parameter. In this way, we put on the same level of comparison the related naked singularity (-M) and the positive mass wormhole. We discuss how to extract information in the context of a f(R) theory. We use the Wheeler-De Witt equation as a basic equation to perform such an analysis regarded as a Sturm-Liouville problem . The application of the same procedure used for the ordinary theory, namely f(R)=R, reveals that to this approximation level, it is not possible to classify the Schwarzschild and its naked partner into a geometry spectrum.Comment: 8 Pages. Contribution given to DICE 2008. To appear in the proceeding

Casimir energy and variational methods in AdS spacetime

Following the subtraction procedure for manifolds with boundaries, we calculate by variational methods, the Schwarzschild-Anti-de Sitter and the Anti-de Sitter space energy difference. By computing the one loop approximation for TT tensors we discover the existence of an unstable mode at zero temperature, which can be stabilized by the boundary reduction method. Implications on a foam-like space are discussed.Comment: Submitted to Classical and Quantum Gravit

Casimir energy and black hole pair creation in Schwarzschild-de Sitter spacetime

Following the subtraction procedure for manifolds with boundaries, we calculate by variational methods, the Schwarzschild-de Sitter and the de Sitter space energy difference. By computing the one loop approximation for TT tensors we discover the existence of an unstable mode even for the non-degenerate case. This result seems to be in agreement with the sub-maximal black hole pair creation of Bousso-Hawking. The instability can be eliminated by the boundary reduction method. Implications on a foam-like space are discussed.Comment: 19 pages,RevTeX with package epsf and four eps figures. Added other references. Accepted for publication in Classical and Quantum Gravit

Extracting the Cosmological Constant from the Wheeler DeWitt Equation in a Modified Gravity Theory

We discuss how to extract information about the cosmological constant from the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville problem. A generalization to a f(R)theory is taken under examination. The equation is approximated to one loop with the help of a variational approach with Gaussian trial wave functionals. We use a zeta function regularization to handle with divergences. A renormalization procedure is introduced to remove the infinities together with a renormalization group equation.Comment: Talk given at QFEXT 07, Workshop on Quantum Field Theory Under the Influence of External Conditions, Leipzig, 17-21 Sep 2007 and talk given at 9th International Conference on Path Integrals - New Trends and Perspectives, Dresden, 23-28 September 2007. 8 pages, accepted for publication in Journal of Physics

Area spectrum and quasinormal modes of black holes

We demonstrate that an equidistant area spectrum for the link variables in loop quantum gravity can reproduce both the thermodynamics and the quasinormal mode properties of black holes.Comment: 11 pages, no figures; references adde

a cephalometric intercentre comparison of patients with unilateral cleft lip and palate at 5 and 10 years of age

SUMMARY The aim of this study was to evaluate any differences between the craniofacial growth of unilateral cleft lip and palate (UCLP) patients who underwent surgery in the Milan CLP centre with those from the Oslo CLP centre at 5 and 10 years of age. The Milan sample comprised 88 UCLP patients (60 males, 28 females) at 5 years of age and 26 patients (17 males, 9 females) at 10 years of age all operated on by the same surgeon. The Oslo sample consisted of 48 UCLP patients (26 males, 22 females) aged 5 years and 29 patients (20 males, 9 females) aged 10 years treated by four different surgeons. Lateral cephalometric radiographs obtained for both samples were analysed and angular measurements and ratios were calculated both for the hard and soft tissues. Statistical analysis was undertaken with an unpaired t -test. At 5 years of age, there were neither sagittal nor vertical hard tissue differences between the two groups. With regard to the soft tissues, only the naso-labial angle showed a statistically signifi cant difference (Milan greater than Oslo by 5 degrees, P 2.6 degrees, P 2.9 degrees, P < 0.001, respectively. At 5 years of age, the Milan UCLP sample had the same maxillary protrusion as the Oslo group, while at 10 years of age, the Milan sample were slightly less protruded than the Oslo group

Evaluation of the Casimir Force for a Dielectric-diamagnetic Cylinder with Light Velocity Conservation Condition and the Analogue of Sellmeir's Dispersion Law

We study the Casimir pressure for a dielectric-diamagnetic cylinder subject to light velocity conservation and with a dispersion law analogous to Sellmeir's rule. Similarities to and differences from the spherical case are pointed out.Comment: 19 pages Latex, no figures; discussion expanded. To appear in Physica Script