263,442 research outputs found
Density Functional Theory of Magnetic Systems Revisited
The Hohenberg-Kohn theorem of density functional theory (DFT) for the case of
electrons interacting with an external magnetic field (that couples to spin
only) is examined in more detail than previously. A unexpected generalization
is obtained: in certain cases (which include half metallic ferromagnets and
magnetic insulators) the ground state, and hence the spin density matrix, is
invariant for some non-zero range of a shift in uniform magnetic field. In such
cases the ground state energy is not a functional of the spin density matrix
alone. The energy gap in an insulator or a half metal is shown to be a ground
state property of the N-electron system in magnetic DFT.Comment: Four pages, one figure. Submitted for publication, April 13, 2000
Revised, Sept 27, 200
Four-Quark Condensates in Nucleon QCD Sum Rules
The in-medium behavior of the nucleon spectral density including
self-energies is revisited within the framework of QCD sum rules. Special
emphasis is given to the density dependence of four-quark condensates. A
complete catalog of four-quark condensates is presented and relations among
them are derived. Generic differences of such four-quark condensates occurring
in QCD sum rules for light baryons and light vector mesons are discussed.Comment: Version accepted for publication: corrected typos, minor changes
based on referee comments included, reference adde
Spectral averaging techniques for Jacobi matrices
Spectral averaging techniques for one-dimensional discrete Schroedinger
operators are revisited and extended. In particular, simultaneous averaging
over several parameters is discussed. Special focus is put on proving lower
bounds on the density of the averaged spectral measures. These Wegner type
estimates are used to analyze stability properties for the spectral types of
Jacobi matrices under local perturbations
Phase-space density in heavy-ion collisions revisited
We derive the phase space density of bosons from a general boson
interferometry formula.
We find that the phase space density is connected with the two-particles and
the single particle density distribution functions. If the boson density is
large, the two particles density distribution function can not be expressed as
a product of two single particle density distributions. However, if the boson
density is so small that two particles density distribution function can be
expressed as a product of two single particle density distributions, then
Bertsch's formula is recovered. For a Gaussian model, the effects of
multi-particles Bose-Einstein correlations on the mean phase space density are
studied.Comment: 18 Pages, Four eps files, EPJC in Pres
T>0 ensemble state density functional theory revisited
A logical foundation of equilibrium state density functional theory in a
Kohn-Sham type formulation is presented on the basis of Mermin's treatment of
the grand canonical state. it is simpler and more satisfactory compared to the
usual derivation of ground state theory, and free of remaining open points of
the latter. It may in particular be relevant with respect to cases of
spontaneous symmetry breaking like non-collinear magnetism and orbital order.Comment: 7 pages, no figure
The density functional theory of classical fluids revisited
We reconsider the density functional theory of nonuniform classical fluids
from the point of view of convex analysis. From the observation that the
logarithm of the grand-partition function is a convex
functional of the external potential it is shown that the Kohn-Sham free
energy is a convex functional of the density . and constitute a pair of Legendre transforms and each
of these functionals can therefore be obtained as the solution of a variational
principle. The convexity ensures the unicity of the solution in both cases. The
variational principle which gives as the maximum of a
functional of is precisely that considered in the density functional
theory while the dual principle, which gives as the maximum of
a functional of seems to be a new result.Comment: 10 page
- …