3,234 research outputs found
Probing vacuum birefringence by phase-contrast Fourier imaging under fields of high-intensity lasers
In vacuum high-intensity lasers can cause photon-photon interaction via the
process of virtual vacuum polarization which may be measured by the phase
velocity shift of photons across intense fields. In the optical frequency
domain, the photon-photon interaction is polarization-mediated described by the
Euler-Heisenberg effective action. This theory predicts the vacuum
birefringence or polarization dependence of the phase velocity shift arising
from nonlinear properties in quantum electrodynamics (QED). We suggest a method
to measure the vacuum birefringence under intense optical laser fields based on
the absolute phase velocity shift by phase-contrast Fourier imaging. The method
may serve for observing effects even beyond the QED vacuum polarization.Comment: 14 pages, 9 figures. Accepted by Applied Physics
Search for sub-eV scalar and pseudoscalar resonances via four-wave mixing with a laser collider
The quasi-parallel photon-photon scattering by combining two-color laser
fields is an approach to produce resonant states of low-mass fields in
laboratory. In this system resonances can be probed via the four-wave mixing
process in the vacuum. A search for scalar and pseudoscalar fields was
performed by combining 9.3 J/0.9 ps Ti-Sapphire laser and 100 J/9 ns
Nd:YAG laser. No significant signal of four-wave mixing was observed. We
provide the upper limits on the coupling-mass relation for scalar and
pseudoscalar fields, respectively, at a 95\% confidence level in the mass
region below 0.15~eV.Comment: Accepted by Prog. Theor. Exp. Phy
Adaptive Evolution of the Myo6 Gene in Old World Fruit Bats (Family: Pteropodidae)
PMCID: PMC3631194This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Brownian molecular motors driven by rotation-translation coupling
We investigated three models of Brownian motors which convert rotational
diffusion into directed translational motion by switching on and off a
potential. In the first model a spatially asymmetric potential generates
directed translational motion by rectifying rotational diffusion. It behaves
much like a conventional flashing ratchet. The second model utilizes both
rotational diffusion and drift to generate translational motion without spatial
asymmetry in the potential. This second model can be driven by a combination of
a Brownian motor mechanism (diffusion driven) or by powerstroke (drift driven)
depending on the chosen parameters. In the third model, elements of both the
Brownian motor and powerstroke mechanisms are combined by switching between
three distinct states. Relevance of the model to biological motor proteins is
discussed.Comment: 11 pages, 8 figure
Axionlike-particle generation by laser-plasma interaction
Axion, a hypothetical particle that is crucial to quantum chromodynamics and
dark matter theory, has not yet been found in any experiment. With the
improvement of laser technique, much stronger quasi-static electric and
magnetic fields can be created in laboratory using laser-plasma interaction. In
this article, we discuss the feasibility of axion or axionlike-particle's
exploring experiments using planar and cylindrically symmetric laser-plasma
fields as backgrounds while probing with an ultrafast superstrong optical laser
or x-ray free-electron laser with high photon number. Compared to classical
magnet design, the axion source in laser-plasma interaction trades the
accumulating length for the source's interacting strength. Besides, a
structured field in the plasma creates a tunable transverse profile of the
interaction and improves the signal-noise ratio via the mechanisms such as
phase-matching. The mass of axion discussed in this article ranges from 1
\textmu eV to 1 eV. Some simple schemes and estimations of axion production and
probe's polarization rotation are given, which reveals the possibility of
future laser-plasma axion source in laboratory.Comment: 24 pages, 5 figure
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