Temperature dependence of the superconducting energy gap from conductance curves

Summary An analytic relationship between the values of the applied voltages which produce a maximum in the differential conductance and the energy gap is derived for BCS isotropic superconductors. The different methods of deduction of the temperature dependence of the gap in high-T _c superconductors are analysed.     

Band effects on conduction electron density of states for the anderson model

Summary The effects of the shape of free conduction density of states on the physical quantities for the periodic Anderson model have been investigated.     

Identification by NMR spectroscopy of some isomeric 1,2,4-triazolo[4,3-a] and [1,5-a]pyrimidines

The title compounds have been prepared with four known procedures. The mixtures of isomers obtained have been separated by countercurrent distribution and the single isomers identified by NMR spectroscopy.     

Coexistence of ferromagnetism and singlet superconductivity via kinetic exchange

We propose a novel mechanism for the coexistence of metallic ferromagnetism and singlet superconductivity assuming that the magnetic instability is due to kinetic exchange. Within this scenario, the unpaired electrons which contribute to the magnetization have a positive feedback on the gain of the kinetic energy in the coexisting phase by undressing the effective mass of the carriers involved in the pairing. The evolution of the magnetization and pairing amplitude and the phase diagram are first analyzed for a generic kinetic exchange model and then are determined within a specific case with spin dependent bond-charge occupation.     

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

An approach to the calculation of Franck–Condon factors in curvilinear coordinates is outlined. The approach is based on curvilinear normal coordinates, which allows for an easy extension of Duschinsky’s transformation to the case of curvilinear coordinates, and on the power series expansion of the kinetic energy operator. Its usefulness in the case of molecules undergoing large displacements of their equilibrium nuclear configurations upon excitation is then demonstrated by an application to the vibrational structure of the photoelectron spectrum of ammonia, using an anharmonic potential only for the symmetric stretching and bending coordinates of the radical cation.     

Superconducting order in low-dimensional boson-fermion model: absence of finite-temperature transition

We present the application of the McBryan and Spencer method to a model describing a mixture of hard-core bosons and fermions interacting each others via a hybridization coupling. We prove upper bounds for some correlation functions at finite temperature and then rule out the possibility of long-range order of superconducting type in one and two dimensions. Received 21 August 2002 Published online 19 November 2002     

An algorithm for finding Bell-type inequalities

This paper deals with the calculation of all the necessary and sufficient conditions for the classical characterization of the probabilities of some events. It shows how a scarcely known method devised by Boole is particularly useful to the solution of this problem. Based on this method, a general and simple algorithm is found that enables the deduction of the inequalities that, like Bell inequalities, express the conditions for classical characterization. The results of the application of the algorithm to some open problems are reported.This work follows the graduation thesis work of the author under the supervision of Professor Enrico G. BNeltrametti at the University of Genoa, Italy.     

A note on the Picard number of singular Fano 3-folds

Using a construction due to C. Casagrande and further developed by the author (Int. Math. Res. Notices, 2012), we prove that the Picard number of a non-smooth Fano 3-fold with isolated factorial canonical singularities is at most 6.     

Thermodynamical properties of the Anderson model in the atomic limit

The theoretical trend of the specific heat, the static magnetic susceptibility and the valence of the localized electrons in the atomic limit of the Anderson model has been investigated. The effect of the various parameters of the Hamiltonian on these quantities has been analyzed with a special emphasis on its relationship with the intermediate valence states of the localized electrons. A good qualitative agreement with some experimental results has been obtained.     

Superconducting properties of the anderson model with correlated electron off-site attraction

Summary Using the Green's function method, the superconducting gap equation in the Anderson model with nearest-enighbour attraction between correlated electrons is obtained. Thes- andp-wave solutions of this equation have been analysed for different choices of the parameters of the model. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.