14,764 research outputs found
Quantum capacitor with discrete charge-anticharge: spectrum and forces
The quantum capacitor with discrete charge is modeled by a Hamiltonian
containing an inductive intrinsic term (tunnel effect between plates). The
spectrum is obtained using a double Hilbert space. Fluctuations in the
charge-anticharge pairs (zero total charge) give rise to an elementary
attraction which is compared to the Casimir force. In this case, the
field-fluctuations force could be also interpreted as charge-fluctuations
force
Mesoscopic circuits with charge discreteness:quantum transmission lines
We propose a quantum Hamiltonian for a transmission line with charge
discreteness. The periodic line is composed of an inductance and a capacitance
per cell. In every cell the charge operator satisfies a nonlinear equation of
motion because of the discreteness of the charge. In the basis of one-energy
per site, the spectrum can be calculated explicitly. We consider briefly the
incorporation of electrical resistance in the line.Comment: 11 pages. 0 figures. Will be published in Phys.Rev.
The distribution of oxygen at the Ni81Fe19/Ta interface
The knowledge of how oxygen atoms are distributed at a magnetic-metal /
oxide, or magnetic-metal / non-magnetic-metal interface, can be an useful tool
to optimize device production. Multilayered Ni81Fe19 / Ta samples consisting of
15 bilayers of 2.5 nm each, grown onto glass substrates by magnetron sputtering
from Ni81Fe19 and Ta targets, have been investigated. X-ray absorption near
edge structure, extended X-Ray absorption fine structure, small angle X-ray
diffraction, and simulations, were used to characterize the samples. Oxygen
atoms incorporated onto Ni81Fe19 films during O2 exposition are mainly bonded
to Fe atoms. This partial oxidation of the Ni81Fe19 surface works as a barrier
to arriving Ta atoms, preventing intermixing at the Ni81Fe19 / Ta interface.
The reduction of the Ni81Fe19 surface by the formation of TaO x is observed.Comment: 14 pages, 9 figures, accepted for publication in Advances in
Materials Science and Engineerin
Ultracold mixtures of metastable He and Rb: scattering lengths from ab initio calculations and thermalization measurements
We have investigated the ultracold interspecies scattering properties of
metastable triplet He and Rb. We performed state-of-the-art ab initio
calculations of the relevant interaction potential, and measured the
interspecies elastic cross section for an ultracold mixture of metastable
triplet He and Rb in a quadrupole magnetic trap at a temperature of
0.5 mK. Our combined theoretical and experimental study gives an interspecies
scattering length , which prior to this work was
unknown. More general, our work shows the possibility of obtaining accurate
scattering lengths using ab initio calculations for a system containing a
heavy, many-electron atom, such as Rb.Comment: 11 pages, 11 figures, accepted for publication in Phys. Rev.
Comparing the Host Galaxies of Type Ia, Type II and Type Ibc Supernovae
We compare the host galaxies of 902 supernovae, including SNe Ia, SNe II and
SNe Ibc, which are selected by cross-matching the Asiago Supernova Catalog with
the SDSS Data Release 7. We further selected 213 galaxies by requiring the
light fraction of spectral observations 15%, which could represent well the
global properties of the galaxies. Among them, 135 galaxies appear on the
Baldwin-Phillips-Terlevich diagram, which allows us to compare the hosts in
terms of star-forming, AGNs (including composites, LINERs and Seyfert 2s) and
"Absorp" (their related emission-lines are weak or non-existence) galaxies. The
diagrams related to parameters D(4000), H, stellar masses, SFRs
and specific SFRs for the SNe hosts show that almost all SNe II and most of SNe
Ibc occur in SF galaxies, which have a wide range of stellar mass and low
D(4000). The SNe Ia hosts as SF galaxies follow similar trends. A
significant fraction of SNe Ia occurs in AGNs and Absorp galaxies, which are
massive and have high D(4000). The stellar population analysis from
spectral synthesis fitting shows that the hosts of SNe II have a younger
stellar population than hosts of SNe Ia. These results are compared with those
of the 689 comparison galaxies where the SDSS fiber captures less than 15% of
the total light. These comparison galaxies appear biased towards higher
12+log(O/H) (0.1dex) at a given stellar mass. Therefore, we believe the
aperture effect should be kept in mind when the properties of the hosts for
different types of SNe are discussed.Comment: 15 pages, 9 figure
The Dynamics of Charges Induced by a Charged Particle Traversing a Dielectric Slab
We studied the dynamics of surfacea and wake charges induced by a charged
particle traversing a dielectric slab. It is shown that after the crossing of
the slab first boundary, the induced on the slab surface charge (image charge)
is transformed into the wake charge, which overflows to the second boundary
when the particle crosses it. It is also shown, that the polarization of the
slab is of an oscillatory nature, and the net induced charge in a slab remains
zero at all stages of the motion.Comment: 12 pages, 1 figur
Phase-coherence time saturation in mesoscopic systems: wave function collapse
A finite phase-coherence time emerges from iterative
measurement onto a quantum system. For a rapid sequence, the phase-coherence
time is found explicitly. For the stationary charge conduction problem, it is
bounded. At all order, in the time-interval of measurements, we propose a
general expression for .Comment: 8 pages, 0 figures, Late
Spin-Electron-Phonon Excitation in Re-based Half-Metallic Double Perovskites
A remarkable hardening (~ 30 cm-1) of the normal mode of vibration associated
with the symmetric stretching of the oxygen octahedra for the Ba2FeReO6 and
Sr2CrReO6 double perovskites is observed below the corresponding magnetic
ordering temperatures. The very large magnitude of this effect and its absence
for the anti-symmetric stretching mode provide evidence against a conventional
spin-phonon coupling mechanism. Our observations are consistent with a
collective excitation formed by the combination of the vibrational mode with
oscillations of local Fe or Cr 3d and Re 5d occupations and spin magnitudes.Comment: 12 pages, 4 figure
Decoherence from internal degrees of freedom for cluster of mesoparticles : a hierarchy of master equations
A mesoscopic evolution equation for an ensemble of mesoparticles follows
after the elimination of internal degrees of freedom. If the system is composed
of a hierarchy of scales, the reduction procedure could be worked repeatedly
and the characterization of this iterating method is carried out. Namely, a
prescription describing a discrete hierarchy of master equations for the
density operator is obtained. Decoherence follows from the irreversible
coupling of the systems, defined by mesoscopic variables, to internal degrees
of freedom. We discuss briefly the existence of systems with the same dynamics
laws at different scales. We made an explicit calculation for an ensemble of
particles with internal harmonic interaction in an external anharmonic field.
New conditions related to the semiclassical limit for mesoscopic systems
(Wigner-function) are conjectured.Comment: 19 pages, 0 figures, late
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