Search results for "ansat"

Combinatorics of generalized Bethe equations

2012

A generalization of the Bethe ansatz equations is studied, where a scalar two-particle S-matrix has several zeroes and poles in the complex plane, as opposed to the ordinary single pole/zero case. For the repulsive case (no complex roots), the main result is the enumeration of all distinct solutions to the Bethe equations in terms of the Fuss-Catalan numbers. Two new combinatorial interpretations of the Fuss-Catalan and related numbers are obtained. On the one hand, they count regular orbits of the permutation group in certain factor modules over \({\mathbb{Z}^M}\), and on the other hand, they count integer points in certain M-dimensional polytopes.

A Culturally Sensitive Approach to Promoting Initial Literacy Development in Africa : Ongoing and Planned Research and Development at the University …

2017

A four-year research and development program at CAPOLSA (the Centre for the Promotion of Literacy in Sub-Saharan Africa) was inspired by widespread dissatisfaction with poor literacy outcomes of mass basic schooling in Zambia and sought to test the generalizability of a scientifically grounded, computer-mediated instructional resource developed in Finland, for effective intervention in an African society where different linguistic and educational conditions obtain. Specific challenges and opportunities posed by the local sociocultural context included the prevalence of multilingualism, the relatively transparent orthographies of local languages, and poor infrastructure of the public school …

Social networks : promoting Mexican popular cultures and building a participatory culture

2012

For over 30 years, the General Direction of Popular Cultures has been in charge of promoting, preserving, and disseminating the cultural diversity of Mexico, regarding indigenous and popular cultural practices. With the increasing popularization of Social Networks, it has become almost indispensable to join Social Networks in order to exist digitally, weather you are an individual, an institution or government. Taking this fact in consideration, in 2011 the Direction of Popular Cultures joined the most utilized social Networks in México: Twitter, Facebook and YouTube, as a way to keep users updated about the activities and general information generated by the Direction. Departing form the p…

Theory of CaL2,3-edge XAS using a novel multichannel multiple-scattering method

2003

A new method for calculating X-ray absorption spectroscopy (XAS) at the L2,3 edges of Ca and transition metals is presented. It is based on the multichannel multiple-scattering theory by Natoli et al. [Phys. Rev. B, (1990), 42, 1944-1968] combined with the eigen-channel R-matrix formalism. Atomic multiplet-like effects, owing to the Coulomb interaction of photoelectrons and the 2p hole, are taken into account through a configuration interaction ansatz for the final-state wavefunction. The various multiplet states lead to a set of channels for the photoelectron wavefunction, which is calculated in multiple-scattering theory. The method is applied to Ca, an important element for biological ap…

De la mundialización a la globofobia

2007

Quantum and Classical Statistical Mechanics of the Integrable Models in 1 + 1 Dimensions

1990

In a short but remarkable paper Yang and Yang [1] showed that the free energy of a model system consisting of N bosons on a line with repulsive δ-function interactions was given by a set of coupled integral equations. The Yangs’ chosen model is in fact the repulsive version of the quantum Nonlinear Schrodinger (NLS) model. We have shown that with appropriate extensions and different dispersion relations and phase shifts similar formulae apply to ‘all’ of the integrable models quantum or classical. These models include the sine-Gordon (s-G) and sinh-Gordon (sinh-G) models, the two NLS models (attractive and repulsive), the Landau-Lifshitz (L-L’) model which includes all four previous models,…

Duality violations in τ hadronic spectral moments

2010

Evidence is presented for the necessity of including duality violations in a consistent description of spectral function moments employed in the precision determination of $\alpha_s$ from $\tau$ decay. A physically motivated ansatz for duality violations in the spectral functions enables us to perform fits to spectral moments employing both pinched and unpinched weights. We describe our analysis strategy and provide some preliminary findings. Final numerical results await completion of an ongoing re-determination of the ALEPH covariance matrices incorporating correlations due to the unfolding procedure which are absent from the currently posted versions. To what extent this issue affects ex…

A New Three-Dimensional Track Fit with Multiple Scattering

2017

Modern semiconductor detectors allow for charged particle tracking with ever increasing position resolution. Due to the reduction of the spatial hit uncertainties, multiple Coulomb scattering in the detector layers becomes the dominant source for tracking uncertainties. In this case long distance effects can be ignored for the momentum measurement, and the track fit can consequently be formulated as a sum of independent fits to hit triplets. In this paper we present an analytical solution for a three-dimensional triplet(s) fit in a homogeneous magnetic field based on a multiple scattering model. Track fitting of hit triplets is performed using a linearization ansatz. The momentum resolution…

Laser spectroscopy with an electrostatic ConeTrap

2017

A compact electrostatic trap has been designed and installed as part of the recent upgrades to the IGISOL IV facility. The ConeTrap provides an in vacuo optical pumping site for low energy (800 eV) ionic ensembles available for interaction periods of 10-100 ms. At present, 6.7(3) % of injected mass A=98 ions can be trapped, stored for 5 ms, extracted and transported to a laser-ion interaction region. This fraction represents those ions for which no perturbation to total energy or energy spread is observed. Proposed enhancements to the trap are designed to improve the trapping efficiency by up to a factor of 5. Differential pumping and reduction in background pressure below the present 10−6 …

Comment on ‘‘Multinucleon mechanisms in (γ,N) and (γ,NN) reactions’’

1996

Recently, calculations of (\ensuremath{\gamma},NN) cross sections in the \ensuremath{\Delta}(1232) region have been reported by J. Ryckebusch et al. [Phys. Rev. C 49, 2704 (1994)]. However, these calculations use an unjustified ansatz for the \ensuremath{\Delta} propagation, which leads to an underestimation of the (\ensuremath{\gamma},NN) cross section in the resonance region for quasifree kinematics. \textcopyright{} 1996 The American Physical Society.