Search results for " Mathematical"

Biproportional methods of structural change analysis: A typological survey

2004

International audience; Analysts often are interested in learning how much an exchange system has changed over time or how two different exchange systems differ. Identifying structural difference in exchange matrices can be performed using either 'directed' or 'undirected' methods. Directed methods are based on the computation and comparison of column- or row-normalizations of the matrices. The choice of row or column for the normalization implies a specific direction of the exchanges, so that the column-wise normalized results should not be compared to the row-wise normalized results. In this category fall the simple comparison of coefficient matrices and the causative method. Undirected m…

On Fibrations Between Internal Groupoids and Their Normalizations

2018

We characterize fibrations and $$*$$ -fibrations in the 2-category of internal groupoids in terms of the comparison functor from certain pullbacks to the corresponding strong homotopy pullbacks. As an application, we deduce the internal version of the Brown exact sequence for $$*$$ -fibrations from the internal version of the Gabriel–Zisman exact sequence. We also analyse fibrations and $$*$$ -fibrations in the category of arrows and study when the normalization functor preserves and reflects them. This analysis allows us to give a characterization of protomodular categories using strong homotopy kernels and a generalization of the Snake Lemma.

Neutron-proton pairing correlations in a single l-shell model

2017

The long standing problem of neutron-proton pairing correlations is revisited by employing the Hartree-Fock-Bogoliubov formalism with neutron-proton mixing in both the particle-hole and particle-hole channels. We compare numerical calculations performed within this method with an exact pairing model based on the $SO(8)$ algebra. The neutron-proton mixing is included in our calculations by performing rotations in the isospin space using the isocranking technique.

Fermi-Dirac correlations in Lambda pairs in hadronic Z decays

2000

Two-particle correlations of Lambda Lambda and pairs have been studied in multihadronic Z decays recorded with the ALEPH detector at LEP in the years from 1992 to 1995. The correlations were measured as a function of the four-momentum difference Q of the pair. A depletion of events is observed in the region Q 2 GeV the fraction of pairs with spin one is consistent with the value of 0.75 expected for a statistical spin mixture, whilst for Q pairs, where no Fermi-Dirac correlations are expected, the spin one fraction is measured to be consistent with 0.75 over the entire analysed Q range. (C) 2000 Elsevier Science B.V. All rights reserved.

Novel mechanism for primordial perturbations in minimal extensions of the Standard Model

2020

Abstract We demonstrate that light spectator fields in their equilibrium can source sizeable CMB anisotropies through modulated reheating even in the absence of direct couplings to the inflaton. The effect arises when the phase space of the inflaton decay is modulated by the spectator which generates masses for the decay products. We call the mechanism indirect modulation and using the stochastic eigenvalue expansion show that it can source perturbations even four orders of magnitude larger than the observed amplitude. Importantly, the indirect mechanism is present in the Standard Model extended with right- handed neutrinos. For a minimally coupled Higgs boson this leads to a novel lower bo…

Grafiska integrēšana un diferencēšana. Neperiodiskas līknes nolīdzinājuma atrašana

1931

Saturs: Funkcionāls sakars, tā attēlošana 3 Empirisks un racionāls nolīdzinājums 3 Pieskares konstrukcijas 6 Grafiska integrēšana 7 Grafiska diferencēšana 9 Līkņu veidi un nolīdzinājumi 10 Līkņu nolīdzinājumi pārveidotā koordinātu sistēmā 11 Deformācija 13 Līkņu pazīmes 13 Atsevišķi nolīdzinājumu veidi 17 Nolīdzinājuma atrašana, ja dots līknes zars 20 Piemēri 21 Nolīdzinājuma atrašana, kad doti līknes visi zari un īpaši punkti 25

VAMPIRE: Vessel assessment and measurement platform for images of the REtina

2011

We present VAMPIRE, a software application for efficient, semi-automatic quantification of retinal vessel properties with large collections of fundus camera images. VAMPIRE is also an international collaborative project of four image processing groups and five clinical centres. The system provides automatic detection of retinal landmarks (optic disc, vasculature), and quantifies key parameters used frequently in investigative studies: vessel width, vessel branching coefficients, and tortuosity. The ultimate vision is to make VAMPIRE available as a public tool, to support quantification and analysis of large collections of fundus camera images.

Order of products of elements in finite groups

2018

If G is a finite group, p is a prime, and x∈G, it is an interesting problem to place x in a convenient small (normal) subgroup of G, assuming some knowledge of the order of the products xy, for certain p‐elements y of G.

Analītiskā ģeometrija plaknē

1947

Combined Analysis of Neutrino and Antineutrino Oscillations at T2K.

2017

T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482 ×10^(20) protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 μ-like events, and 7.471 × 10^(20) protons on target in antineutrino mode, which yielded 4 e-like and 66 μ-like events. Reactor measurements of sin(2)2θ(13) have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase δCP spans the range (−3.13, −0.39) for normal mass ordering. The CP conservation hypothesis …