Search results for "REPRESENTATION"

RPA in wavefunction representation

1992

The RPA is formulated in subspaces of coordinate-like and momentum-like I ph operators. This allows to embed a large class of approximative schemes into a generalized RPA treatment. We give a detailed formulation in terms of wavefunctions in coordinate space which is ideally suited to practical programming. In particular, we work out the reduction to spherical tensors in the case of spherical symmetry which is most often the starting point in finite Fermion systems.

Multimode equivalent network representation for planar junctions involving elliptical waveguides

1996

A model study of Hartree-Fock and Linear Response in coordinate space

1979

A fast procedure for spherical Hartree-Fock is obtained by coordinate space representation and a modification of gradient iteration. Along similar lines, the corresponding Linear Response equations are derived and solved, in order to achieve a fully consistent treatment. The Linear Response equations are applied to a change in particle numbers, i.e. to the description of isotopic differences. In a model study we look for their physical and numerical properties, i.e. linearity of the response, numerical stability and consistency requirements for the Hartree-Fock basis.

A new representation of the Adler function for lattice QCD

2013

We address several aspects of lattice QCD calculations of the hadronic vacuum polarization and the associated Adler function. We implement a representation derived previously which allows one to access these phenomenologically important functions for a continuous set of virtualities, irrespective of the flavor structure of the current. Secondly we present a theoretical analysis of the finite-size effects on our particular representation of the Adler function, based on the operator product expansion at large momenta and on the spectral representation of the Euclidean correlator at small momenta. Finally, an analysis of the flavor structure of the electromagnetic current correlator is perform…

An A4 model for lepton masses and mixings

2009

We study an extension of the standard model based on the flavor symmetry A(4) only. Neutrino Majorana mass terms arise from a dimension five operator and charged lepton masses from renormalizable Yukawa couplings. We introduce three Higgs doublets that belong to one triplet irreducible representation of A(4). We study the most general A(4)-invariant scalar potential and the phenomenological consequences of the model. We find that the reactor angle could be as large as sin(2)theta(13max)similar to 0.03, while the atmospheric mixing angle theta(23) is close to maximal, sin(2)theta(23)=1/2.

A SEARCH FOR PAIR-PRODUCED CHARGED HIGGS BOSONS IN Z0 DECAYS

1990

The utilitarian representation of sport in Rumania, a brake in the development of leisure practice. Since the countries of central Europe entered the liberal sphere influence, the consumptions of possessions and services develop there. We observe a movement of tutellaire and ideological emancipation of the sports organizations, but the practice of popular physical activities delays developing. If, on the ground, we notice the appearance of an structured professionally offer, contrary to all expectations, it does not pull a real increase of consumption. This situation which rises in inferred paradox a cultural interrogation on the previous history of these brakes. Historically, the sport dur…

On the singular behaviour of scattering amplitudes in quantum field theory

2014

We analyse the singular behaviour of one-loop integrals and scattering amplitudes in the framework of the loop--tree duality approach. We show that there is a partial cancellation of singularities at the loop integrand level among the different components of the corresponding dual representation that can be interpreted in terms of causality. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences.

NONCOMMUTATIVE GEOMETRY AND GRADED ALGEBRAS IN ELECTROWEAK INTERACTIONS

1992

The Standard Model of Electroweak Interactions can be described by a generalized Yang-Mills field incorporating both the usual gauge bosons and the Higgs fields. The graded derivative by means of which the Yang-Mills field strength is constructed involves both a differential acting on space-time and a differential acting on an associative graded algebra of matrices. The square of the curvature for the corresponding covariant derivative yields the bosonic Lagrangian of the Standard Model. We show how to recover the whole fermionic part of the Standard Model in this framework. Quarks and leptons fit naturally into the smallest typical and nontypical irreducible representations of the graded …

Weakly interacting dark matter particle of a minimal technicolor theory

2007

We consider the possibility that a massive fourth family neutrino, predicted by a recently proposed minimal technicolor theory, could be the source of the dark matter in the Universe. The model has two techniflavors in the adjoint representation of a SU(2) techicolor gauge group and its consistency requires the existence of a fourth family of leptons. By a suitable hypercharge assignment the techniquarks together with the new leptons look like a conventional fourth standard model family. We show that the new (Majorana) neutrino N can be the dark matter particle if m{sub N}{approx}100-500 GeV and the expansion rate of the Universe at early times is dominated by an energy component scaling as…

Large-N Weinberg-Tomozawa interaction and spin-flavor symmetry

2006

The construction of an extended version of the Weinberg-Tomozawa Lagrangian, in which baryons and mesons form spin-flavor multiplets, is reviewed and some of its properties discussed, for an arbitrary number of colors and flavors. The coefficient tables of spin-flavor irreducible representations related by crossing between the $s$-, $t$- and $u$-channels are explicitly constructed.