35 research outputs found
Landau Ghosts and Anti-Ghosts in Condensed Matter and High Density Hadronic Matter
It is observed that the ``ghost'' (originally discovered by Landau in quantum
electro-dynamics) and its counterparts in other theories are indeed ubiquitous
as they occur in a one-loop approximation to any conventional (unbroken) gauge
theory. The mechanism is first exposed in its generality via the Dyson equation
and a simple but explicit example in condensed matter is provided through the
static Clausius-Mossotti and its dynamic counterpart the Lorenz-Lorentz
equation. The physical phase transition phenomenon associated with it is found
to be super-radiance. We verify quantitatively that water (and many other polar
liquids) are indeed super-radiant at room temperature. In quantum
chromo-dynamics on the other hand, we encounter, thanks to asymptotic freedom,
an ``anti-ghost'' which is closely associated with color confinement. Thus, in
QCD, free quarks and glue exist in a super-radiant phase and hadronic matter in
the normal one.Comment: LaTeX 12 Pages and 2 *.eps Figure
Nanoscale Smoothing and the Analysis of Interfacial Charge and Dipolar Densities
The interface properties of interest in multilayers include interfacial
charge densities, dipole densities, band offsets, and screening-lengths, among
others. Most such properties are inaccesible to direct measurements, but are
key to understanding the physics of the multilayers. They are contained within
first-principles electronic structure computations but are buried within the
vast amount of quantitative information those computations generate. Thus far,
they have been extracted from the numerical data by heuristic nanosmoothing
procedures which do not necessarily provide results independent of the
smoothing process. In the present paper we develop the theory of nanosmoothing,
establishing procedures for both unpolarized and polarized systems which yield
interfacial charge and dipole densities and band offsets invariant to the
details of the smoothing procedures when the criteria we have established are
met. We show also that dipolar charge densities, i. e. the densities of charge
transferred across the interface, and screening lengths are not invariant. We
illustrate our procedure with a toy model in which real, transversely averaged
charge densities are replaced by sums of Gaussians.Comment: 30 pages, 15 figures, 4 table