47 research outputs found
Generic scaling relation in the scalar model
The results of analysis of the one--loop spectrum of anomalous dimensions of
composite operators in the scalar model are presented. We give the
rigorous constructive proof of the hypothesis on the hierarchical structure of
the spectrum of anomalous dimensions -- the naive sum of any two anomalous
dimensions generates a limit point in the spectrum. Arguments in favor of the
nonperturbative character of this result and the possible ways of a
generalization to other field theories are briefly discussed.Comment: 15 pages, Latex, 50 K
Theoretical high- d-wave superconducting gap in an inhomogeneous medium
We perform theoretical calculations to obtain a distribution of local d-wave
superconducting gaps for a high temperature superconducting
(HTSC) series in a disordered superconductor with an average doping level
. To reproduce the inhomogeneous medium a nonmagnetic random potential
, within a Bogoliubov-de Gennes (BdG) formalism, is considered. First
the phase diagram for the LSCO HTSC series, with V^{imp}=0,
is obtained. Then, we perform calculations considering a fixed value of the
disorder strength and obtain a distribution of local superconducting
gaps , and local density of charge carriers . It is
shown that the underdoped compounds are more inhomogeneous than the overdoped
ones, which is in accordance with experimental findings. Also, the spatial
variation of indicates that as increases, the system
becomes more homogeneous.Comment: 6 pages and 6 fig
Using the local density approximation and the LYP, BLYP, and B3LYP functionals within Reference--State One--Particle Density--Matrix Theory
For closed-shell systems, the local density approximation (LDA) and the LYP,
BLYP, and B3LYP functionals are shown to be compatible with reference-state
one-particle density-matrix theory, where this recently introduced formalism is
based on Brueckner-orbital theory and an energy functional that includes exact
exchange and a non-universal correlation-energy functional. The method is
demonstrated to reduce to a density functional theory when the
exchange-correlation energy-functional has a simplified form, i.e., its
integrand contains only the coordinates of two electron, say r1 and r2, and it
has a Dirac delta function -- delta(r1 - r2) -- as a factor. Since Brueckner
and Hartree--Fock orbitals are often very similar, any local exchange
functional that works well with Hartree--Fock theory is a reasonable
approximation with reference-state one-particle density-matrix theory. The LDA
approximation is also a reasonable approximation. However, the Colle--Salvetti
correlation-energy functional, and the LYP variant, are not ideal for the
method, since these are universal functionals. Nevertheless, they appear to
provide reasonable approximations. The B3LYP functional is derived using a
linear combination of two functionals: One is the BLYP functional; the other
uses exact exchange and a correlation-energy functional from the LDA.Comment: 26 Pages, 0 figures, RevTeX 4, Submitted to Mol. Phy
New continuous wave infrared ArâXe laser at intermediate gas pressures pumped by a transverse radio frequency discharge
An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 ÎŒm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz
A novel bidirectional pendulum tuned mass damper using variable homogeneous friction to achieve amplitudeâindependent control
Passive tuned mass dampers (TMDs) are widely used in controlling structural vibrations. Although their principle is well established, the search for improved arrangements is still under way. This effort has recently produced an innovative paradigm of bidirectional pendulum TMD (BTMD) that, moving along a specially designed threeâdimensional (3D) surface, can simultaneously control two inâplane orthogonal structural modes. In existing versions of BTMDs, energy dissipation is provided either by ordinary horizontal viscous dampers or by an original arrangement of vertical friction dampers. In this paper, a new paradigm is proposed, in which energy dissipation comes from the tangential friction arising along the pendulum surface out of an optimal spatially variable friction coefficient pattern. Within this paradigm, if the friction coefficient is taken proportional to the modulus of the pendulum surface gradient, the dissipation model results nonlinear homogeneous in the smalldisplacement domain, and the performance of the absorber, herein called the homogeneous tangential friction BTMD (HTâBTMD), results independent from the excitation level. The present work introduces this concept, derives the analytical model of the HTâBTMD, establishes a method for its optimal design, and numerically verifies its seismic effectiveness in comparison with viscously damped devices. The validity and feasibility of the concept are demonstrated through experimental tests on a smallâscale lab prototype, which also show the efficacy of a stepwise approximation of the homogeneous friction pattern. The new device proves a competing alternative to existing BTMDs, and homogeneous tangential friction proves a promising new paradigm to provide pendular systems with amplitudeâindependent structural damping