156,354 research outputs found
A data-based parametrization of parton distribution functions
Get PDFSince the first determination of a structure function many decades ago, all methodologies used to determine structure functions or parton distribution functions (PDFs) have employed a common prefactor as part of the parametrization. The NNPDF collaboration pioneered the use of neural networks to overcome the inherent bias of constraining the space of solution with a fixed functional form while still keeping the same common prefactor as a preprocessing. Over the years various, increasingly sophisticated, techniques have been introduced to counter the effect of the prefactor on the PDF determination. In this paper we present a methodology to perform a data-based scaling of the Bjorken x input parameter which facilitates the removal the prefactor, thereby significantly simplifying the methodology, without a loss of efficiency and finding good agreement with previous results.Since the first determination of a structure function many decades ago, all methodologies used to determine structure functions or parton distribution functions (PDFs) have employed a common prefactor as part of the parametrization. The NNPDF collaboration pioneered the use of neural networks to overcome the inherent bias of constraining the space of solution with a fixed functional form while still keeping the same common prefactor as a preprocessing. Over the years various, increasingly sophisticated, techniques have been introduced to counter the effect of the prefactor on the PDF determination. In this paper we present a methodology to remove the prefactor entirely, thereby significantly simplifying the methodology, without a loss of efficiency and finding good agreement with previous results
Effects of Two-Photon Transition on Femtosecond Pulse Propagation in Multiple Quantum Well Waveguides
No full textStudies of Two-Photon Transition Nonlinearities Near Half the Band Gap in Semiconductor Based on AlGaAs for Nonlinear Switching
No full textMeasurements of Two-Photon Absorption Coefficient and Induced Nonlinear Refractive-Index in GaAs/AlGaAs Multiquantum Well Waveguide
No full textEffects of Dispersive Two-Photon Transitions on Femtosecond Pulse Propagation in Semiconductor Waveguides
No full textAnisotropic Two-Photon Absorption Coefficient and Induced Nonlinear Refractive-Index in GaAs/AlGaAs Multiple Quantum Well Waveguide
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Quadratic Spatial Solitons
Get PDFQuadratic spatial solitons, beams that propagate unchanged in shape and magnitude, are supported by second order optical nonlinearities and can occur in all wave mixing processes under appropriate conditions. They are multi-component, consisting of all the frequency components that are coupled by a second order nonlinear interaction near a phase-matching condition. They have been observed in a number of bulk crystalline media, in LiNbO3 slab waveguides and in arrays of parallel, weakly coupled, LiNbO3 channel waveguides. The properties of the solitons and their excitation will be reviewed. To cite this article: G.I. Stegeman, C. R. Physique 8 (2007). © 2006 Académie des sciences
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