115,710 research outputs found
Physics of the Pseudogap State: Spin-Charge Locking
The properties of the pseudogap phase above Tc of the high-Tc cuprate
superconductors are described by showing that the Anderson-Nambu SU(2) spinors
of an RVB spin gap 'lock' to those of the electron charge system because of the
resulting improvement of kinetic energy. This enormously extends the range of
the vortex liquid state in these materials. As a result it is not clear that
the spinons are ever truly deconfined. A heuristic description of the
electrodynamics of this pseudogap-vortex liquid state is proposed.Comment: Submitted to Phys Rev Letter
Dynamic testing of complex structures
Response of structure is determined under impulses large enough to create severe strains. Electrodynamic shaker can provide impulses to nearly any point on structure and can deliver repeated pulses of varying force and duration
Electronic structure of strongly correlated d-wave superconductors
We study the electronic structure of a strongly correlated d-wave
superconducting state. Combining a renormalized mean field theory with direct
calculation of matrix elements, we obtain explicit analytical results for the
nodal Fermi velocity, v_F, the Fermi wave vector, k_F, and the momentum
distribution, n_k, as a function of hole doping in a Gutzwiller projected
d-wave superconductor. We calculate the energy dispersion, E_k, and spectral
weight of the Gutzwiller-Bogoliubov quasiparticles, and find that the spectral
weight associated with the quasiparticle excitation at the antinodal point
shows a non monotonic behavior as a function of doping. Results are compared to
angle resolved photoemission spectroscopy (ARPES) of the high temperature
superconductors.Comment: final version, comparison to experiments added, 4+ pages, 4 figure
Numerical design of streamlined tunnel walls for a two-dimensional transonic test
An analytical procedure is discussed for designing wall shapes for streamlined, nonporous, two-dimensional, transonic wind tunnels. It is based upon currently available 2-D inviscid transonic and boundary layer analysis computer programs. Predicted wall shapes are compared with experimental data obtained from the NASA Langley 6 by 19 inch Transonic Tunnel where the slotted walls were replaced by flexible nonporous walls. Comparisons are presented for the empty tunnel operating at a Mach number of 0.9 and for a supercritical test of an NACA 0012 airfoil at zero lift. Satisfactory agreement is obtained between the analytically and experimentally determined wall shapes
Parametric analysis of diffuser requirements for high expansion ratio space engine
A supersonic diffuser ejector design computer program was developed. Using empirically modified one dimensional flow methods the diffuser ejector geometry is specified by the code. The design code results for calculations up to the end of the diffuser second throat were verified. Diffuser requirements for sea level testing of high expansion ratio space engines were defined. The feasibility of an ejector system using two commonly available turbojet engines feeding two variable area ratio ejectors was demonstrated
One-Particle Excitation of the Two-Dimensional Hubbard Model
The real part of the self-energy of interacting two-dimensional electrons has
been calculated in the t-matrix approximation. It is shown that the forward
scattering results in an anomalous term leading to the vanishing
renormalization factor of the one-particle Green function, which is a
non-perturbative effect of the interaction U. The present result is a
microscopic demonstration of the claim by Anderson based on the conventional
many-body theory. The effect of the damping of the interacting electrons, which
has been ignored in reaching above conclusion, has been briefly discussed.Comment: 7 pages, LaTeX, 1 figure, uses jpsj.sty, to be published in J. Phys.
Soc. Jpn. 66 No. 3 (1997
Calculation of flow about posts and powerhead model
A three dimensional analysis of the non-uniform flow around the liquid oxygen (LOX) posts in the Space Shuttle Main Engine (SSME) powerhead was performed to determine possible factors contributing to the failure of the posts. Also performed was three dimensional numerical fluid flow analysis of the high pressure fuel turbopump (HPFTP) exhaust system, consisting of the turnaround duct (TAD), two-duct hot gas manifold (HGM), and the Version B transfer ducts. The analysis was conducted in the following manner: (1) modeling the flow around a single and small clusters (2 to 10) of posts; (2) modeling the velocity field in the cross plane; and (3) modeling the entire flow region with a three dimensional network type model. Shear stress functions which will permit viscous analysis without requiring excessive numbers of computational grid points were developed. These wall functions, laminar and turbulent, have been compared to standard Blasius solutions and are directly applicable to the cylinder in cross flow class of problems to which the LOX post problem belongs
Vortices and turbulence in trapped atomic condensates
After over a decade of experiments generating and studying the physics of
quantized vortices in atomic gas Bose-Einstein condensates, research is
beginning to focus on the roles of vortices in quantum turbulence, as well as
other measures of quantum turbulence in atomic condensates. Such research
directions have the potential to uncover new insights into quantum turbulence,
vortices and superfluidity, and also explore the similarities and differences
between quantum and classical turbulence in entirely new settings. Here we
present a critical assessment of theoretical and experimental studies in this
emerging field of quantum turbulence in atomic condensates
The origin of phase in the interference of Bose-Einstein condensates
We consider the interference of two overlapping ideal Bose-Einstein
condensates. The usual description of this phenomenon involves the introduction
of a so-called condensate wave functions having a definite phase. We
investigate the origin of this phase and the theoretical basis of treating
interference. It is possible to construct a phase state, for which the particle
number is uncertain, but phase is known. However, how one would prepare such a
state before an experiment is not obvious. We show that a phase can also arise
from experiments using condensates in Fock states, that is, having known
particle numbers. Analysis of measurements in such states also gives us a
prescription for preparing phase states. The connection of this procedure to
questions of ``spontaneously broken gauge symmetry'' and to ``hidden
variables'' is mentioned.Comment: 22 pages 4 figure
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