B -> X_u l nu decay distributions to order alpha_s

An analytic result for the O(alpha_s corrections to the triple differential B -> X_u l nu decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O(alpha_s) corrections to the hadronic invariant mass spectrum is presented. The effects of Fermi motion, which are important for the description of decay spectra close to infrared sensitive regions, are included. The behaviour of perturbation theory in the region of time-like momenta is also investigatedComment: 24 pages, 11 figures, 1 typo in eq.(5.4) corrected; version published in JHEP06(1999)01

Radiative ϕ\phi−-meson decays and η\eta-η′\eta^\prime mixing: a QCD sum rule analysis

The radiative transitions $\phi \to \eta \gamma$ and $\phi \to \eta^\prime \gamma$ are analysed using QCD sum-rules. The results we obtain for ${\cal B}(\phi \to \eta \gamma)=(1.15 \pm 0.2) 10^{-2}$ and ${\cal B}(\phi \to \eta^\prime \gamma)=(1.18 \pm 0.4) 10^{-4}$ are in very good agreement with existing experimental data. The related issue of $\eta-\eta^\prime$ mixing is discussed and we give predictions for the $\eta$ and $\eta^\prime$ decay constants in the framework of a mixing scheme in the quark-flavour basis.Comment: Latex, 15 pages, 3figures. Some typos correcte

Multistability of a Josephson parametric amplifier coupled to a mechanical resonator

We study the dynamics of Josephson Parametric Amplifier (JPA) coupled to a mechanical oscillator, as realised with a dc Superconducting Quantum Interference Device (SQUID) with an embedded movable arm. We analyse this system in the regime when the frequency of the mechanical oscillator is comparable in magnitude with the plasma oscillation of the SQUID. When the nano-mechanical resonator is driven, it strongly affects the dynamics of the JPA. We show that this coupling can considerably modify the dynamics of JPA and induce its multistability rather than common bistability. This analysis is relevant if one considers a JPA for detection of mechanical motion.Comment: 8 pages, 5 figures, accepted for publication in Phys. Rev.

Shot noise in charge and magnetization currents of a quantum ring

The shot noise in a quantum ring, connected to leads, is studied in the presence of electron interactions in the sequential tunneling regime. Two qualitatively different noise correlations with distinctly different behaviors are identified and studied in a large range of parameters. Noise in the total current is due to the discreteness of the electron charge and can become super-Poissonian as result of electron interaction. The noise in the magnetization current is comparatively insensitive to the interaction but can be greatly enhanced if population inversion of the angular states is assumed. The characteristic time scales are studied by a Monte-Carlo simulation.Comment: 5 pages, 5 color figure

Measuring von Neumann entanglement entropies without wave functions

We present a method to measure the von Neumann entanglement entropy of ground states of quantum many-body systems which does not require access to the system wave function. The technique is based on a direct thermodynamic study of entanglement Hamiltonians, whose functional form is available from field theoretical insights. The method is applicable to classical simulations such as quantum Monte Carlo methods, and to experiments that allow for thermodynamic measurements such as the density of states, accessible via quantum quenches. We benchmark our technique on critical quantum spin chains, and apply it to several two-dimensional quantum magnets, where we are able to unambiguously determine the onset of area law in the entanglement entropy, the number of Goldstone bosons, and to check a recent conjecture on geometric entanglement contribution at critical points described by strongly coupled field theories

The Relationship Between Banking Market Competition and Risk-taking: Do Size and Capitalization Matter?

This paper aims to study the effect of banking competition on Latin American banks' risk-taking and whether capitalization and size changes this relationship. We conclude that: (1) competition affects risk in a non-linear manner: high/low (average) competition are related to more (less) stability; (2) bank's size explains the advantage from competition, while capitalization is only positive for larger banks in this case; (3) capital ratio explains the advantage from lower competition. These results are of uttermost importance for bank regulation, especially due to the recent turmoil in worldwide financial markets.

Profit, Cost and Scale Efficiency for Latin American Banks: Concentration-Performance Relationship

Using a sample of 495 Latin American banks over the period 2001-2008, this paper investigates how bank concentration influences cost and profit efficiency. We calculate scale efficiency to assess whether these banks are close to their optimal size. We find that banks are more inefficient in profits than in costs; concentration impairs cost efficiency; larger banks have higher performance, but this advantage decreases in concentrated markets; private and foreign banks are the most efficient; most banks are operating under increasing returns of scale, which contributes to the discussion on Basel III.