La fisica della musica

La musica è composta da sequenze di suoni le cui frequenze hanno rapporti semplici e ben definiti. Storicamente, nella musica occidentale è stata selezionata una sequenza particolare di frequenze che definiscono le note della scala musicale temperat

Approximate Treatment of Lepton Distortion in Charged-Current Neutrino Scattering from Nuclei

The partial-wave expansion used to treat the distortion of scattered electrons by the nuclear Coulomb field is simpler and considerably less time-consuming when applied to the production of muons and electrons by low and intermediate-energy neutrinos. For angle-integrated cross sections, however, a modification of the "effective-momentum-transfer" approximation seems to work so well that for muons the full distorted-wave treatment is usually unnecessary, even at kinetic energies as low as an MeV and in nuclei as heavy as lead. The method does not work as well for electron production at low energies, but there a Fermi function usually proves adequate. Scattering of electron-neutrinos from muon decay on iodine and of atmospheric neutrinos on iron are discussed in light of these results.Comment: 11 pages, LaTeX, submitted to Phys. Rev.

Functional approach to the electromagnetic response function: the Longitudinal Channel

In this paper we address the (charge) longitudinal electromagnetic response for a homogeneous system of nucleons interacting via meson exchanges in the functional framework. This approach warrants consistency if the calculation is carried on order-by-order in the mesonic loop expansion with RPA-dressed mesonic propagators. At the 1-loop order and considering pion, rho and omega exchanges we obtain a quenching of the response, in line with the experimental results.Comment: RevTeX, 18 figures available upon request - to be published in Physical Review

Inclusion of virtual nuclear excitations in the formulation of the (e,e'N)

A wave-function framework for the theory of the (e,e'N) reaction is presented in order to justify the use of coupled channel equations in the usual Feynman matrix element. The overall wave function containing the electron and nucleon coordinates is expanded in a basis set of eigenstates of the nuclear Hamiltonian, which contain both bound states as well as continuum states.. The latter have an ingoing nucleon with a variable momentum Q incident on the daughter nucleus as a target, with as many outgoing channels as desirable. The Dirac Eqs. for the electron part of the wave function acquire inhomogeneous terms, and require the use of distorted electron Green's functions for their solutions. The condition that the asymptotic wave function contain only the appropriate momentum Q_k for the outgoing nucleon, which corresponds to the electron momentum k through energy conservation, is achieved through the use of the steepest descent saddle point method, commonly used in three-body calculations.Comment: 30 page

Isoscalar dipole coherence at low energies and forbidden E1 strength

In 16O and 40Ca an isoscalar, low-energy dipole transition (IS-LED) exhausting approximately 4% of the isoscalar dipole (ISD) energy-weighted sum rule is experimentally known, but conspicuously absent from recent theoretical investigations of ISD strength. The IS-LED mode coincides with the so-called isospin-forbidden E1 transition. We report that for N=Z nuclei up to 100Sn the fully self-consistent Random-Phase-Approximation with finite-range forces, phenomenological and realistic, yields a collective IS-LED mode, typically overestimating its excitation energy, but correctly describing its IS strength and electroexcitation form factor. The presence of E1 strength is solely due to the Coulomb interaction between the protons and the resulting isospin-symmetry breaking. The smallness of its value is related to the form of the transition density, due to translational invariance. The calculated values of E1 and ISD strength carried by the IS-LED depend on the effective interaction used. Attention is drawn to the possibility that in N-not-equal-Z nuclei this distinct mode of IS surface vibration can develop as such or mix strongly with skin modes and thus influence the pygmy dipole strength as well as the ISD strength function. In general, theoretical models currently in use may be unfit to predict its precise position and strength, if at all its existence.Comment: 9 pages, 6 figures, EPJA submitte

La fisica della musica

La musica è composta da sequenze di suoni le cui frequenze hanno rapporti semplici e ben definiti. Storicamente, nella musica occidentale è stata selezionata una sequenza particolare di frequenze che definiscono le note della scala musicale temperat

Holter monitoring in AL amyloidosis: prognostic implications.

The heart is involved in more than one third of patients with primary (AL) amyloidosis at diagnosis and it is by far the most common cause of death. Rhythm and conduction abnormalities generally represent the terminal event. The aims of this study were to determine the spectrum of Holter abnormalities found in AL amyloidosis and to assess their prognostic significance, particularly in relation to sudden death. Fifty-one patients with AL amyloidosis were included, and all of them had a complete history, physical examination, two-dimensional echocardiography, and 24-hour Holter monitoring. Fifty-five percent of these patients had echographic signs of heart involvement and 23\% had heart failure. Complex ventricular arrhythmias were found in 57\% of patients, couplets in 29\%, and nonsustained ventricular tachycardia in 18\%. Overall median survival was 23.4 months. Congestive heart failure, echocardiographic abnormalities, and Holter abnormalities adversely affected survival. The multivariate analysis demonstrated that interventricular septum thickness and couplets were independent predictors of survival. The presence of couplets correlated with sudden death. Holter monitoring may contribute to assessing the prognosis of patients with AL amyloidosis