57,195 research outputs found
Weak Sequential Completeness of Uniform Algebras
We prove that a uniform algebra is weakly sequentially complete if and only
if it is finite-dimensional
Swarm optimization for adaptive phase measurements with low visibility
Adaptive feedback normally provides the greatest accuracy for optical phase
measurements. New advances in nitrogen vacancy centre technology have enabled
magnetometry via individual spin measurements, which are similar to optical
phase measurements but with low visibility. The adaptive measurements that
previously worked well with high-visibility optical interferometry break down
and give poor results for nitrogen vacancy centre measurements. We use advanced
search techniques based on swarm optimisation to design better adaptive
measurements that can provide improved measurement accuracy with low-visibility
interferometry, with applications in nitrogen vacancy centre magnetometry.Comment: 8 pages, 7 figures, comments welcom
Positive effective Q12 electrostrictive coefficient in perovskites
It is demonstrated that for classical perovskites such as BaTiO3, SrTiO3 and
PbTiO3 electrostrictive strain induced by an electric field may not obey
traditionally considered "extension along the field, contraction perpendicular
to it" behavior if a sample is cut obliquely to the cubic crystallographic
directions
Archimedes' law and its corrections for an active particle in a granular sea
We study the origin of buoyancy forces acting on a larger particle moving in
a granular medium subject to horizontal shaking and its corrections before
fluidization. In the fluid limit Archimedes' law is verified; before the limit
memory effects counteract buoyancy, as also found experimentally. The origin of
the friction is an excluded volume effect between active particles, which we
study more exactly for a random walker in a random environment. The same
excluded volume effect is also responsible for the mutual attraction between
bodies moving in the granular medium. Our theoretical modeling proceeds via an
asymmetric exclusion process, i.e., via a dissipative lattice gas dynamics
simulating the position degrees of freedom of a low density granular sea.Comment: 22 pages,5 figure
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