4,796 research outputs found
Stripe formation in high-Tc superconductors
The non-uniform ground state of the two-dimensional three-band Hubbard model
for the oxide high-Tc superconductors is investigated using a variational Monte
Carlo method. We examine the effect produced by holes doped into the
antiferromagnetic (AF) background in the underdoped region. It is shown that
the AF state with spin modulations and stripes is stabilized du to holes
travelling in the CuO plane. The structures of the modulated AF spins are
dependent upon the parameters used in the model. The effect of the boundary
conditions is reduced for larger systems. We show that there is a region where
incommensurability is proportional to the hole density. Our results give a
consistent description of stripes observed by the neutron- scattering
experiments based on the three-band model for CuO plane.Comment: 8 pages, 9 figure
PMDM1: POWER AND SAMPLE SIZE CALCULATIONS FOR A CLINICAL TRIAL CONSIDERING COST-EFFECTIVENESS AND STATISTICAL ERRORS
Locally Optimal Control of Quantum Systems with Strong Feedback
For quantum systems with high purity, we find all observables that, when
continuously monitored, maximize the instantaneous reduction in the von Neumann
entropy. This allows us to obtain all locally optimal feedback protocols with
strong feedback, and explicit expressions for the best such protocols for
systems of size N <= 4. We also show that for a qutrit the locally optimal
protocol is the optimal protocol for a given range of control times, and derive
an upper bound on all optimal protocols with strong feedback.Comment: 4 pages, Revtex4. v2: published version (some errors corrected
Effects of energy dependence in the quasiparticle density of states on far-infrared absorption in the pseudogap state
We derive a relationship between the optical conductivity scattering rate
1/\tau(\omega) and the electron-boson spectral function \alpha^2F(\Omega) valid
for the case when the electronic density of states, N(\epsilon), cannot be
taken as constant in the vicinity of the Fermi level. This relationship turned
out to be useful for analyzing the experimental data in the pseudogap state of
cuprate superconductors.Comment: 8 pages, RevTeX4, 1 EPS figure; final version published in PR
Ultra-High-Speed Photography and Optical Flash Measurement of Nylon Sphere Impact Phenomena
AbstractAn optical spike is sometimes observed prior to the main flash in high-velocity impact experiments. The spikes are particularly noticeable in the case of Nylon66 projectiles. In this study, we conducted experiments in which Nylon66 spheres impacted the flat surfaces of Nylon66 blocks perpendicularly at 7km s-1. We observed the impact phenomena by using an ultra-high-speed camera and high-temporal-resolution photometers to identify the cause of the spikes. High-speed photographs show that the entire projectile was shining while it was penetrating a target. Glaring light from the shock front propagating in the projectile is assumed to become diffused within the translucent projectile and then radiated from its surface. The blackbody radiation from the shock front at 3600K, which is calculated based on a one-dimensional shock model, accounts for the radiative intensities measured by the photometers. A sub-spike was observed just after the main spike in all the experiments conducted, the cause of which was not ascertained
- …