ΣΣ → YN transitions in the decay of 6 ΛΛ He

Universidad de Sevilla. Máster Universitario en Física Nuclea

Valuation of Defaultable Bonds and Debt Restructuring

In this paper we develop a contingent valuation model for zero-coupon bonds with default. In order to emphasize the role of maturity time and place of the lender’s claim in the hierarchy of debt of a firm, we consider a firm that issues two bonds with different maturities and different seniorage. The model allows us to analyze the implications of both debt renegotiation and capital structure of a firm on the prices of bonds. We obtain that renegotiation brings about a significant change in the bond prices and that the effect is dispersed through different channels: increasing the value of the firm, reallocating payments, and avoiding costly liquidation. Moreover, the presence of two creditors leads to qualitatively different implications for pricing, while emphasizing the importance of bond covenants and renegotiation of the entire debt.Debt valuation, Defaultable bonds, Strategic contingent claim analysis, Modigliani-Miller theorem

Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts

We study the range of consistency of a model based on a nonlinear scalar field Dirac-Born-Infeld action for the unification of dark matter and dark energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59 high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this analysis, we also include the CMB7-year data and the baryonic acoustic peak BAO. Besides, it is calculated the parameter of the equation of state $w$, the deceleration parameter $q_0$ and the redshift of the transition to the decelerate-accelerated phase $z_t$.Comment: 6 pages, to appear in Proceedings of Spanish Relativity Meeting 2011 (ERE 2011) held in Madrid, Spai

The infinite cyclohedron and its automorphism group

Cyclohedra are a well-known infinite familiy of finite-dimensional polytopes that can be constructed from centrally symmetric triangulations of even-sided polygons. In this article we introduce an infinite-dimensional analogue and prove that the group of symmetries of our construction is a semidirect product of a degree 2 central extension of Thompson's infinite finitely presented simple group T with the cyclic group of order 2. These results are inspired by a similar recent analysis by the first author of the automorphism group of an infinite-dimensional associahedron.Comment: 18 pages, 8 figure

Observational constraints on the unified dark matter and dark energy model based on the quark bag model

In this work we investigate if a small fraction of quarks and gluons, which escaped hadronization and survived as a uniformly spread perfect fluid, can play the role of both dark matter and dark energy. This fluid, as developed in \citep{Brilenkov}, is characterized by two main parameters: $\beta$, related to the amount of quarks and gluons which act as dark matter; and $\gamma$, acting as the cosmological constant. We explore the feasibility of this model at cosmological scales using data from type Ia Supernovae (SNeIa), Long Gamma-Ray Bursts (LGRB) and direct observational Hubble data. We find that: (i) in general, $\beta$ cannot be constrained by SNeIa data nor by LGRB or H(z) data; (ii) $\gamma$ can be constrained quite well by all three data sets, contributing with $\approx78\%$ to the energy-matter content; (iii) when a strong prior on (only) baryonic matter is assumed, the two parameters of the model are constrained successfully.Comment: 10 pages, 6 figures, 3 table