Search results for "basis"
showing 10 items of 760 documents
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 CRITICAL VIEW ON THE PERTURBATIVE RG METHOD
2012
The perturbative renormalization group (RG) treatment of the Ginzburg–Landau model is reconsidered based on the Feynman diagram technique. We derive RG flow equations, exactly calculating all vertices appearing in the perturbative RG transformation of the φ4 model up to the ε3 order of the ε-expansion. The Fourier-transformed two-point correlation function G(k) has been considered. Although the ε-expansion of X(k) = 1/G(k) is well defined on the critical surface, we have revealed an inconsistency with the exact rescaling of X(k), represented as an expansion in powers of k at k →0. This new result can serve as a basis to challenge the correctness of the ε-expansion-based perturbative RG met…
η–η′ mixing in the flavor basis and large N
2010
Abstract The mass matrix for η – η ′ is derived in the flavor basis at O ( p 4 ) of the chiral Lagrangian using the large N approximation. Under certain assumptions, the mixing angle ϕ = 41.4 ° and the decay constants ratio f K / f π = 1.15 are calculated in agreement with the data. It appears that the FKS scheme arises as a special limit of the chiral Lagrangian. Their mass matrix is obtained without the hypothesis on the mixing pattern of the decay constants.
A two-center-oscillator-basis as an alternative set for heavy ion processes
1977
The two-center-oscillator-basis, which is constructed from harmonic oscillator wave functions developing about two different centers, suffers from numerical problems at small center separations due to the overcompleteness of the set. In order to overcome these problems we admix higher oscillator wave functions before the orthogonalization, or antisymmetrization resp. This yields a numerically stable basis set at each center separation. The results obtained for the potential energy surface are comparable with the results of more elaborate models.
Emergent Soft Monopole Modes in Weakly-Bound Deformed Nuclei
2014
Based on the Hartree-Fock-Bogoliubov solutions in large deformed coordinate spaces, the finite amplitude method for quasiparticle random phase approximation (FAM-QRPA) has been implemented, providing a suitable approach to probe collective excitations of weakly-bound nuclei embedded in the continuum. The monopole excitation modes in Magnesium isotopes up to the neutron drip line have been studied with the FAM-QRPA framework on both the coordinate-space and harmonic oscillator basis methods. Enhanced soft monopole strengths and collectivity as a result of weak-binding effects have been unambiguously demonstrated.
Field transformations and simple models illustrating the impossibility of measuring off-shell effects
1999
In the context of simple models illustrating field transformations in Lagrangian field theories we discuss the impossibility of measuring off-shell effects in nucleon-nucleon bremsstrahlung, Compton scattering, and related processes. To that end we introduce a simple phenomenological Lagrangian describing nucleon-nucleon bremsstrahlung and perform an appropriate change of variables leading to different off-shell behavior in the nucleon-nucleon amplitude as well as the photon-nucleon vertex. As a result we obtain a class of equivalent Lagrangians, generating identical S-matrix elements, of which the original Lagrangian is but one representative. We make use of this property in order to show …
Calculation of beta-decay properties of neutron-rich nickel isotopes
1989
Gamow-Tellerβ-decay properties of neutron-rich Ni isotopes have been calculated in the RPA with Nilsson model wave functions. On the basis of the results for the known isotopes67–69Ni, half-lives and neutron-emission probabilities for70–82Ni are predicted and compared to earlier model estimates. Possible implications onr-process nucleosynthesis are discussed.
Invariant approach to flavor-dependent CP-violating phases in the MSSM
2004
We use a new weak basis invariant approach to classify all the observable phases in any extension of the Standard Model (SM). We apply this formalism to determine the invariant CP phases in a simplified version of the Minimal Supersymmetric SM with only three non-trivial flavour structures. We propose four experimental measures to fix completely all the observable phases in the model. After these phases have been determined from experiment, we are able to make predictions on any other CP-violating observable in the theory, much in the same way as in the Standard Model all CP-violation observables are proportional to the Jarlskog invariant.
CP-violation with bosons
1993
We formulate the conditions under which a purely bosonic theory (without fermions) containing neutral spin-0 particles and vector (gauge) bosons violates the CP-symmetry through the presence of CP-even and CP-odd operators in the Lagrangian. This is done without reference to explicitly CP-violating scalar sector of extended standard models (SM) with two or more Higgs doublets. The Lagrangian expressed in the mass basis of the spin-0 fields can, however, in certain cirumstances be identified with a part of the CP-violating SM with two Higgs doublets. It is instructive to consider the manifestation of CP-violation in the mass basis since this leads directly to suggestions of genuine CP-signal…
Error estimates for pi-pi scattering threshold parameters in Chiral Perturbation Theory to two loops
2000
Using the analysis of ChPT to two loops, we perform an error analysis of the threshold and low energy parameters, based on the uncertainties for the one loop low energy parameters and the resonance saturation mechanism. Different sets of one loop low energy constants have been considered.Thus, the predictive power of the effective field theory is quantified on the basis of the present experimental uncertainties.