23,521 research outputs found
Zero-field and Larmor spinor precessions in a neutron polarimeter experiment
We present a neutron polarimetric experiment where two kinds of spinor
precessions are observed: one is induced by different total energy of neutrons
(zero-field precession) and the other is induced by a stationary guide field
(Larmor precession). A characteristic of the former is the dependence of the
energy-difference, which is in practice tuned by the frequency of the
interacting oscillating magnetic field. In contrast the latter completely
depends on the strength of the guide field, namely Larmor frequency. Our
neutron-polarimetric experiment exhibits individual tuning as well as specific
properties of each spinor precession, which assures the use of both spin
precessions for multi-entangled spinor manipulation.Comment: 12 pages, 4 figure
Synchronizations in small-world networks of spiking neurons: Diffusive versus sigmoid couplings
By using a semi-analytical dynamical mean-field approximation previously
proposed by the author [H. Hasegawa, Phys. Rev. E, {\bf 70}, 066107 (2004)], we
have studied the synchronization of stochastic, small-world (SW) networks of
FitzHugh-Nagumo neurons with diffusive couplings. The difference and similarity
between results for {\it diffusive} and {\it sigmoid} couplings have been
discussed. It has been shown that with introducing the weak heterogeneity to
regular networks, the synchronization may be slightly increased for diffusive
couplings, while it is decreased for sigmoid couplings. This increase in the
synchronization for diffusive couplings is shown to be due to their local,
negative feedback contributions, but not due to the shorten average distance in
SW networks. Synchronization of SW networks depends not only on their structure
but also on the type of couplings.Comment: 17 pages, 8 figures, accepted in Phys. Rev. E with some change
Mechanism of Ambipolar Field-Effect Carrier Injections in One-Dimensional Mott Insulators
To clarify the mechanism of recently reported, ambipolar carrier injections
into quasi-one-dimensional Mott insulators on which field-effect transistors
are fabricated, we employ the one-dimensional Hubbard model attached to a
tight-binding model for source and drain electrodes. To take account of the
formation of Schottky barriers, we add scalar and vector potentials, which
satisfy the Poisson equation with boundary values depending on the drain
voltage, the gate bias, and the work-function difference. The current-voltage
characteristics are obtained by solving the time-dependent Schr\"odinger
equation in the unrestricted Hartree-Fock approximation. Its validity is
discussed with the help of the Lanczos method applied to small systems. We find
generally ambipolar carrier injections in Mott insulators even if the work
function of the crystal is quite different from that of the electrodes. They
result from balancing the correlation effect with the barrier effect. For the
gate-bias polarity with higher Schottky barriers, the correlation effect is
weakened accordingly, owing to collective transport in the one-dimensional
correlated electron systems.Comment: 21 pages, 10 figures, to appear in J. Phys. Soc. Jp
High Dynamic-Range and Very Low Noise K-Band p-HEMT LNA MMIC for LMDS and Satellite Communication
An excellent noise figure and high linearity, K-band p-HEMT LNA MMIC, that incorporates single-bias configuration and negative feedback circuit, has be en developed for LMDS (Local Multi-point Distribution Service) and satellite communication. The third order intercept point (IP3) of this MMIC is 20 dBm, while output power at 1-dB gain compression is 8.5 dBm. The IP3 and noise figure is 19.5 +/- 1 dBm and 1.8 +/- 0.2 dB, respectively, at frequencies between 24 and 32 GHz. The die size of the MMIC is 1.9 mm. This MMIC shows a potential reliable application in high-speed wireless access system
Ion Charge States in the Fast Solar Wind: New Data Analysis and Theoretical Refinements
We present a further investigation into the increased ionization observed in
element charge states in the fast solar wind compared to its coronal hole
source regions. Once ions begin to be perpendicularly heated by ion cyclotron
waves and execute large gyro-orbits, density gradients in the flow can excite
lower hybrid waves that then damp by heating electrons in the parallel
direction. We give further analysis of charge state data from polar coronal
holes at solar minimum and maximum, and also from equatorial coronal holes. We
also consider further the damping of lower hybrid waves by ions and the effect
of non-Maxwellian electron distribution functions on the degree of increased
ionization, both of which appear to be negligible for the solar wind case
considered here. We also suggest that the density gradients required to heat
electrons sufficiently to further ionize the solar wind can plausibly result
from the turbulent cascade of MHD waves.Comment: 27 pages, accepted by Ap
Noncyclic Pancharatnam phase for mixed state SU(2) evolution in neutron polarimetry
We have measured the Pancharatnam relative phase for spin-1/2 states. In a
neutron polarimetry experiment the minima and maxima of intensity modulations,
giving the Pancharatnam phase, were determined. We have also considered general
SU(2) evolution for mixed states. The results are in good agreement with
theory.Comment: 5 pages, 4 figures, to be published in Phys.Lett.
Superconductivity of Quasi-One-Dimensional Electrons in Strong Magnetic Field
The superconductivity of quasi-one-dimensional electrons in the magnetic
field is studied. The system is described as the one-dimensional electrons with
no frustration due to the magnetic field. The interaction is assumed to be
attractive between electrons in the nearest chains, which corresponds to the
lines of nodes of the energy gap in the absence of the magnetic field. The
effective interaction depends on the magnetic field and the transverse
momentum. As the magnetic field becomes strong, the transition temperature of
the spin-triplet superconductivity oscillates, while that of the spin-singlet
increases monotonically.Comment: 15 pages, RevTeX, 3 PostScript figures in uuencoded compressed tar
file are appende
- …