Search results for " Operator"

A general approach for the calculation of the energy levels and the inelastic neutron scattering cross-section of highly nuclear magnetic clusters

1997

Abstract We develop here a general approach to calculate in an efficient way the spin levels as well as the spin eigenfunctions and the INS intensities of clusters formed by large numbers of exchange-coupled magnetic metal ions. The approach is based on the successive use of the irreducible tensor operator techniques and takes into account all kinds of magnetic exchange interactions between the metal ions. The potentialities of this approach are illustrated from an example comprising nine exchange-coupled Ni (II) ions.

Irreversibility of the transport equations

1974

Solution of self-consistent equations for the N3LO nuclear energy density functional in spherical symmetry. The program hosphe (v1.02)

2010

Abstract We present solution of self-consistent equations for the N 3 LO nuclear energy density functional. We derive general expressions for the mean fields expressed as differential operators depending on densities and for the densities expressed in terms of derivatives of wave functions. These expressions are then specified to the case of spherical symmetry. We also present the computer program hosphe (v1.02), which solves the self-consistent equations by using the expansion of single-particle wave functions on the spherical harmonic oscillator basis. Program summary Program title: HOSPHE (v1.02) Catalogue identifier: AEGK_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGK_…

Essential Spectra Under Perturbations

2018

The spectrum of a bounded linear operator on a Banach space X can be sectioned into subsets in many different ways, depending on the purpose of the inquiry.

Ground-state properties of generalized Heisenberg chains with composite spin.

1988

We consider in detail the ground-state properties of recently introduced generalized Heisenberg models which can have several spin operators at each site and which interpolate smoothly between Heisenberg chains of different spin lengths. We show that the mappings to field-theoretical models used to describe the critical properties of the Heisenberg model remain valid in the composite-spin model. In models which interpolate between the spin-(1/2 and the spin-1 behavior, these mappings predict an extended singlet phase around the isotropic antiferromagnetic point whenever the models move away from the spin-(1/2 point. Numerical calculations on finite chains seem to confirm the existence of th…

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.

Angular distributions in quasi-fission reactions: Evidence for incomplete relaxation of the tilting mode

1985

Angular distributions of fission-like fragments have been measured for50Ti+208Pb and56Fe+208Pb collisions. Z-dependent asymmetries around Θincm= 90° preclude their interpretation in terms of compound nucleus fission with the transition state theory. Fits of the data with a simple ansatz for statistical angular momentum fluctuations (tilting) give evidence for an incomplete relaxation of the tilting mode in quasi fission reactions.

Erratum to: “A quark model analysis of orbital angular momentum” [Phys. Lett. B 460 (1999) 8–16]

2000

Additivity of effective quadrupole moments and angular momentum alignments in the A~130 nuclei

2007

The additivity principle of the extreme shell model stipulates that an average value of a one-body operator be equal to the sum of the core contribution and effective contributions of valence (particle or hole) nucleons. For quadrupole moment and angular momentum operators, we test this principle for highly and superdeformed rotational bands in the A~130 nuclei. Calculations are done in the self-consistent cranked non-relativistic Hartree-Fock and relativistic Hartree mean-field approaches. Results indicate that the additivity principle is a valid concept that justifies the use of an extreme single-particle model in an unpaired regime typical of high angular momenta.

Locality properties of Neuberger's lattice Dirac operator

1998

The gauge covariant lattice Dirac operator D which has recently been proposed by Neuberger satisfies the Ginsparg-Wilson relation and thus preserves chiral symmetry. The operator also avoids a doubling of fermion species, but its locality properties are not obvious. We now prove that D is local (with exponentially decaying tails) if the gauge field is sufficiently smooth at the scale of the cutoff. Further analytic and numerical studies moreover suggest that the locality of the operator is in fact guaranteed under far more general conditions.