Area Quantization in Quasi-Extreme Black Holes

We consider quasi-extreme Kerr and quasi-extreme Schwarzschild-de Sitter black holes. From the known analytical expressions obtained for their quasi-normal modes frequencies, we suggest an area quantization prescription for those objects.Comment: Final version to appear in Mod. Phys. Lett.

Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays

When studying B decays within the Standard Model, it is customary to use the unitarity of the CKM matrix in order to write the decay amplitudes in terms of only two of the three weak phases which appear in the various diagrams. Occasionally, it is mentioned that those two weak phases can be used in order to describe any decay amplitude, even beyond the Standard Model. Here we point out that, when describing a generic decay amplitude, the two weak phases can be chosen completely at will, and we study the behavior of the decay amplitudes under changes in the two weak phases chosen as a basis. Of course, physical observables cannot depend on such reparametrizations. This has an impact in discussions of the SM and in attempts to parametrize new physics effects in the decay amplitudes. We illustrate these issues by looking at B --> psi K_S and the isospin analysis in B --> pi pi.Comment: 16 pages, RevTe

The valuation relevance of credit ratings: Empirical evidence from financial institutions around the world

This study investigates whether the market valuation of the two summary accounting measures, book value of equity and net income, is higher (lower) for the financial institutions positively (negatively) rated by the Moddy’s and/or by the Standard and Poor’s, when compared to financial institutions that are not rated by these credit rating agencies. Findings suggest that positive ratings have an impact in valuation both in developed and emerging countries, and that in the case of emerging countries negative ratings do not impact market valuation significantly. Overall, the results are consistent with the idea that credit ratings are useful in reducing value uncertainty of the issuing firms and in mitigating information asymmetry in capital markets.info:eu-repo/semantics/publishedVersio

Large Neutrino Mixing with Universal Strength of Yukawa Couplings

We analyse, within the framework of universal strength for Yukawa couplings (USY), various structures for the Dirac and Majorana neutrino mass matrices giving rise, through the see-saw mechanism, to a degenerate mass spectrum. A specific USY ansatz is presented for the charged lepton and neutrino effective mass matrix, leading to quasi-degenerate neutrinos and a leptonic mixing matrix which provides a large angle solution for both the atmospheric and solar neutrino problems.Comment: 7 pages, ReVTeX, small comments adde

Large effects on \BsBs mixing by vector-like quarks

We calculate the contributions of the vector-like quark model to \BsBs mixing, taking into account the constraints from the decay $B\to X_s\gamma$. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However, \BsBs mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In sizable ranges of the model parameters, the mixing parameter $x_s$ is much different from the standard model prediction.Comment: 11 pages, 4 figures, To be published in Phys. Rev.

Hierarchy plus anarchy in quark masses and mixings

We introduce a new parameterisation of the effect of unknown corrections from new physics on quark and lepton mass matrices. This parameterisation is used in order to study how the hierarchies of quark masses and mixing angles are modified by random perturbations of the Yukawa matrices. We discuss several examples of flavour relations predicted by different textures, analysing how these relations are influenced by the random perturbations. We also comment on the unlikely possibility that unknown corrections contribute significantly to the hierarchy of masses and mixings.Comment: LaTeX, 18 pages, 16 PS figure

D0−Dˉ0D^0 - \bar D^0 Mixing in the Presence of Isosinglet Quarks

We analyse $\Delta C=2$ transitions in the framework of a minimal extension of the Standard Model where either a $Q=2/3$ or a $Q=-1/3$ isosinglet quark is added to the standard quark spectrum. In the case of a $Q=2/3$ isosinglet quark, it is shown that there is a significant region of parameter space where $D^0 - \bar D^0$ mixing is sufficiently enhanced to be observed at the next round of experiments. On the contrary, in the case of a $Q=-1/3$ isosinglet quark, it is pointed out that obtaining a substancial enhancement of $D^0 - \bar D^0$ mixing, while complying with the experimental constraints on rare kaon decays, requires a contrived choice of parameters.Comment: 10 pages plus four figures. The figures are not included but are available upon reques

High overtones of Dirac perturbations of a Schwarzschild black hole

Using the Frobenius method, we find high overtones of the Dirac quasinormal spectrum for the Schwarzschild black hole. At high overtones, the spacing for imaginary part of $\omega_{n}$ is equidistant and equals to $\Im{\omega_{n+1}}-\Im{\omega_{n}} =i/8M$, ($M$ is the black hole mass), which is twice less than that for fields of integer spin. At high overtones, the real part of $\omega_{n}$ goes to zero. This supports the suggestion that the expected correspondence between quasinormal modes and Barbero-Immirzi parameter in Loop Quantum Gravity is just a numerical coincidence.Comment: 5 pages, Latex, 3 figures, Physical Review D.,at pres