Search results for "paul"

2017

It has been shown in previous papers that classes of (minimal asymmetric) informationally-complete positive operator valued measures (IC-POVMs) in dimension d can be built using the multiparticle Pauli group acting on appropriate fiducial states. The latter states may also be derived starting from the Poincare upper half-plane model H . To do this, one translates the congruence (or non-congruence) subgroups of index d of the modular group into groups of permutation gates, some of the eigenstates of which are the sought fiducials. The structure of some IC-POVMs is found to be intimately related to the Kochen-Specker theorem.

Magnetic properties of quantum dots and rings

2001

Exact many-body methods as well as current-spin-density functional theory are used to study the magnetism and electron localization in two-dimensional quantum dots and quasi-one-dimensional quantum rings. Predictions of broken-symmetry solutions within the density functional model are confirmed by exact configuration interaction (CI) calculations: In a quantum ring the electrons localize to form an antiferromagnetic chain which can be described with a simple model Hamiltonian. In a quantum dot the magnetic field localizes the electrons as predicted with the density functional approach.

Dirac and Pauli form factors from lattice QCD

2011

We present a comprehensive analysis of the electromagnetic form factors of the nucleon from a lattice simulation with two flavors of dynamical O(a)-improved Wilson fermions. A key feature of our calculation is that we make use of an extensive ensemble of lattice gauge field configurations with four different lattice spacings, multiple volumes, and pion masses down to m_\pi ~ 180 MeV. We find that by employing Kelly-inspired parametrizations for the Q^2-dependence of the form factors, we are able to obtain stable fits over our complete ensemble. Dirac and Pauli radii and the anomalous magnetic moments of the nucleon are extracted and results at light quark masses provide evidence for chiral …

Nucleon structure from Lattice QCD using a nearly physical pion mass

2014

We report the first Lattice QCD calculation using the almost physical pion mass mpi=149 MeV that agrees with experiment for four fundamental isovector observables characterizing the gross structure of the nucleon: the Dirac and Pauli radii, the magnetic moment, and the quark momentum fraction. The key to this success is the combination of using a nearly physical pion mass and excluding the contributions of excited states. An analogous calculation of the nucleon axial charge governing beta decay has inconsistencies indicating a source of bias at low pion masses not present for the other observables and yields a result that disagrees with experiment.

On the Pauli-Villars regularisation scheme in the NJL model

1993

Abstract We consider the Nambu-Jona-Lasinio model with a Pauli-Villars cutoff. We point out that previous attempts to use this regularisation have not been consistent and it is shown that if used correctly this approach yields very reasonable values for the cutoff parameter and quark condensate when we demand that ƒπ is fixed to its experimental value. Finally it is argued that because of its covariance and smooth nature this regularisation scheme has significant advantages over other regulators on the market.

Quark exchange in deep inelastic scattering

1995

We use a model for baryons that links the constituent structure to the deep inelastic (current) properties. The approach consists in a laboratory partonic description (based on a model of hadron structure), to which a low momentum scaleQ 0 is adscribed, which is evolved to high momenta by means of the renormalization group. A generalization of the model by means of the hadronic quark cluster decomposition, provides a description of the structure functions of nuclei and is the starting point to study the effects that the antisymmetrization at the quark level has on the structure function of a model deuteron. The analysis contains conventional and high momentum partonic components. We next st…

Microscopic description of the nucleon- Delta interaction in the quark cluster model.

1995

By using a nonrelativistic quark cluster model to describe baryonic systems, we generate a nucleon-{Delta} potential from the elementary interaction between constituents. The basic quark-quark potential used provides, when applied to the nucleon-nucleon system, an adequate description of the scattering phase shifts, the deuteron properties and the nonstrange baryonic spectroscopy. Special attention is paid to the short-range behavior of the interaction and its connection to the quark Pauli principle. This establishes a conceptual difference with meson-exchange models where the interaction, due to the lack of data, is not even well defined.

About two equivalent descriptions of quark antisymmetrization

1992

We analyze the wave function for a two-hadron system when the quark symmetrization principle is incorporated. Two alternative mathematical descriptions are considered. The representation method of Hund constructs a system of generators of thesinglet⊗singlet type. The method of Young-Froebenius incorporates hidden-color components in order to describe the representation basis. By taking a naive model we show that the two descriptions, are equivalent and thus no physical meaning should be attached to their mathematical differences. The results of our analysis are then applied to the more realisticN-N (deuteron) system. We end by discussing the structure of the Pauli correlations which we comp…

Un 'halcón' paradigmático

2007

Assessing the economic profitability of Paulownia as a biomass crop in Southern Mediterranean area

2022

The increase of renewable energy production worldwide, occurred in the last years, is also attributable to some agroforestry species cultivated according to the short rotation coppice technique. Although these species are able of enhancing abandoned or marginal land leading to numerous environmental benefits, an increasing number of farmers are introducing them in place of agricultural crops. Therefore, since for a farmer economic sustainability is one of the main factors to introduce a biomass crop, the study aimed at evaluating the profitability of Paulownia, a species that has been spreading in recent years. In particular, an economic analysis has been carried out in a Southern Italian f…