2,766 research outputs found
The Isospin Asymmetry in Anomalous Fluid Dynamics
The dynamics of fluids in which the constituent particles carry nonabelian
charges can be described succinctly in terms of group-valued variables via a
generalization of the co-adjoint orbit action for particles. This formalism,
which is particularly suitable for incorporating anomalies, has previously been
used for the chiral magnetic and chiral vorticity effects. Here we consider the
similar effect for the isospin which corresponds to an angular asymmetry for
neutral pions.Comment: 12 page
Lateral Chirality-sorting Optical Spin Forces in Evanescent Fields
The transverse component of the spin angular momentum of evanescent waves
gives rise to lateral optical forces on chiral particles, which have the
unusual property of acting in a direction in which there is neither a field
gradient nor wave propagation. As their direction and strength depends on the
chiral polarizability of the particle, they act as chirality-sorting and may
offer a mechanism for passive chirality spectroscopy. The absolute strength of
the forces also substantially exceeds that of other recently predicted sideways
optical forces, such that they may more readily offer an experimental
confirmation of the phenomenon.Comment: 7 pages, 2 Figure
Reply to "Comment on 'Precision measurement of the Casimir-Lifshitz force in a fluid'"
We have reviewed the Comment of Geyer et al. [arXiv:0708.1548] concerning our
recent work [Phys. Rev. A 75, 060102 (R) (2007)], and while we disagree with
their criticisms, we acknowledge them for giving us the opportunity to add
interesting addition material and a more detailed description of our
experiment. We describe further our calculation and explain why a more
sophisticated model is not warranted. We also present detailed experiments on
the effects of electrostatic forces in our measurements and show that the
contribution due to work function differences is small and that the residual
electrostatic force is dominated by trapped charges and external fields.
Finally, we estimate the effect of double layer interactions. These additional
calculations and measurements support our original conclusion that the
experimental results are consistent with the Lifshitz theory
Nonlinear feedback oscillations in resonant tunneling through double barriers
We analyze the dynamical evolution of the resonant tunneling of an ensemble
of electrons through a double barrier in the presence of the self-consistent
potential created by the charge accumulation in the well.
The intrinsic nonlinearity of the transmission process is shown to lead to
oscillations of the stored charge and of the transmitted and reflected fluxes.
The dependence on the electrostatic feedback induced by the self-consistent
potential and on the energy width of the incident distribution is discussed.Comment: 10 pages, TeX, 5 Postscript figure
Stellar Mass to Halo Mass Scaling Relation for X-ray Selected Low Mass Galaxy Clusters and Groups out to Redshift
We present the stellar mass-halo mass scaling relation for 46 X-ray selected
low-mass clusters or groups detected in the XMM-BCS survey with masses
at
redshift . The cluster binding masses are inferred
from the measured X-ray luminosities \Lx, while the stellar masses
of the galaxy populations are estimated using near-infrared imaging from the
SSDF survey and optical imaging from the BCS survey. With the measured \Lx\ and
stellar mass , we determine the best fit stellar mass-halo mass
relation, accounting for selection effects, measurement uncertainties and the
intrinsic scatter in the scaling relation. The resulting mass trend is
, the intrinsic (log-normal) scatter is
, and there is no
significant redshift trend , although
the uncertainties are still large. We also examine within a fixed
projected radius of ~Mpc, showing that it provides a cluster binding mass
proxy with intrinsic scatter of (1 in ). We
compare our scaling relation from the XMM-BCS
clusters with samples of massive, SZE-selected clusters
() and low mass NIR-selected clusters
() at redshift .
After correcting for the known mass measurement systematics in the compared
samples, we find that the scaling relation is in good agreement with the high
redshift samples, suggesting that for both groups and clusters the stellar
content of the galaxy populations within depends strongly on mass but
only weakly on redshift out to .Comment: 15 pages, 10 figures. Accepted for publication in MNRA
Layered superconductors as negative-refractive-index metamaterials
We analyze the use of layered superconductors as anisotropic metamaterials.
Layered superconductors can have a negative refraction index in a wide
frequency range for arbitrary incident angles. Indeed, low-Tc (s-wave)
superconductors allow to produce artificial heterostructures with low losses
for T<<Tc. However, the real part of their in-plane effective permittivity is
very large. Moreover, even at low temperatures, layered high-Tc superconductors
have a large in-plane normal conductivity, producing large losses (due to
d-wave symmetry). Therefore, it is difficult to enhance the evanescent modes in
either low-Tc or high-Tc superconductors.Comment: 4 pages, 2 figure
Precision measurement of the Casimir-Lifshitz force in a fluid
The Casimir force, which results from the confinement of the quantum
mechanical zero-point fluctuations of the electromagnetic fields, has received
significant attention in recent years for its effect on micro- and nano-scale
mechanical systems. With few exceptions, experimental observations have been
limited to conductive bodies interacting separated by vacuum or air. However,
interesting phenomena including repulsive forces are expected to exist in
certain circumstances between metals and dielectrics when the intervening
medium is not vacuum. In order to better understand the effect of the Casimir
force in such situations and to test the robustness of the generalized
Casimir-Lifshitz theory, we have performed the first precision measurements of
the Casimir force between two metals immersed in a fluid. For this situation,
the measured force is attractive and is approximately 80% smaller than the
force predicted by Casimir for ideal metals in vacuum. We present experimental
results and find them to be consistent with Lifshitz's theory.Comment: 6 pages, 3 figures. (version before final publication
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On the Temperature Dependence of Point-Defect-Mediated Luminescence in Silicon
We present a model of the temperature dependence of point-defect-mediated luminescence in silicon derived from basic kinetics and semiconductor physics and based on the kinetics of bound exciton formation. The model provides a good fit to data for W line electroluminescence and G line photoluminescence in silicon. Strategies are discussed for extending luminescence to room temperature.Engineering and Applied Science
Asymmetric double barrier resonant tunneling structures with improved characteristics
We present a self-consistent calculation, based on the global coherent
tunnelling model, and show that structural asymmetry of double barrier resonant
tunnelling structures significantly modifies the current-voltage
characteristics compared to the symmetric structures. In particular, a suitably
designed asymmetric structure can produce much larger peak current and absolute
value of the negative differential conductivity than its commonly used
symmetric counterpart.Comment: 1 paper, 3 figure
Nonlinear Micromechanical Casimir Oscillator
The Casimir force between uncharged metallic surfaces originates from quantum
mechanical zero point fluctuations of the electromagnetic field. We demonstrate
that this quantum electrodynamical effect has a profound influence on the
oscillatory behavior of microstructures when surfaces are in close proximity
(<= 100 nm). Frequency shifts, hysteretic behavior and bistability caused by
the Casimir force are observed in the frequency response of a periodically
driven micromachined torsional oscillator.Comment: 4 pages, 4 figures; added and rearranged references; added comments
on sensitivit
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