4,635 research outputs found
Casimir Force between two Half Spaces of Vortex Matter in Anisotropic Superconductors
We present a new approach to calculate the attractive long-range
vortex-vortex interaction of the van der Waals type present in anisotropic and
layered superconductors. The mapping of the statistical mechanics of
two-dimensional charged bosons allows us to define a Casimir problem: Two half
spaces of vortex matter separated by a gap of width R are mapped to two
dielectric half planes of charged bosons interacting via a massive gauge field.
We determine the attractive Casimir force between the two half planes and show
that it agrees with the pairwise summation of the van der Waals force between
vortices.Comment: Submitted to Physica C (4 pages, 2 figures
Fixed point actions and on-shell tree-level Symanzik improvement
In this paper it is argued that the properties of the fixed point action of a
renormalization group transformation can be used to implement the on-shell
tree-level Symanzik improvement of lattice actions to any given order in the
expansion in the lattice spacing, in a way which does not involve any
perturbative calculations. In particular, a well-known technique for the lowest
order improvement of SU(N) lattice gauge theories is revisited from the point
of view of fixed point actions, which allows to shed light on some subtle
points.Comment: 14 pages, LaTeX, 1 TeX figur
Hydraulic fluid interaction servovalves Monthly technical report, 1 Feb. - 1 Mar. 1966
Hydraulic fluid interaction servovalves - valve design, torque motor specification, environment tests, and vortex valve test
Comparison and verification of enthalpy schemes for polythermal glaciers and ice sheets with a one-dimensional model
The enthalpy method for the thermodynamics of polythermal glaciers and ice
sheets is tested and verified by a one-dimensional problem (parallel-sided
slab). The enthalpy method alone does not include explicitly the transition
conditions at the cold-temperate transition surface (CTS) that separates the
upper cold from the lower temperate layer. However, these conditions are
important for correctly determining the position of the CTS. For the numerical
solution of the polythermal slab problem, we consider a two-layer
front-tracking scheme as well as three different one-layer schemes
(conventional one-layer scheme, one-layer melting CTS scheme, one-layer
freezing CTS scheme). Computed steady-state temperature and water-content
profiles are verified with exact solutions, and transient solutions computed by
the one-layer schemes are compared with those of the two-layer scheme,
considered to be a reliable reference. While the conventional one-layer scheme
(that does not include the transition conditions at the CTS) can produce
correct solutions for melting conditions at the CTS, it is more reliable to
enforce the transition conditions explicitly. For freezing conditions, it is
imperative to enforce them because the conventional one-layer scheme cannot
handle the associated discontinuities. The suggested numerical schemes are
suitable for implementation in three-dimensional glacier and ice-sheet models.Comment: 16 pages, 8 figure
Density functional theory of vortex lattice melting in layered superconductors: a mean-field--substrate approach
We study the melting of the pancake vortex lattice in a layered
superconductor in the limit of vanishing Josephson coupling. Our approach
combines the methodology of a recently proposed mean-field substrate model for
such systems with the classical density functional theory of freezing. We
derive a free-energy functional in terms of a scalar order-parameter profile
and use it to derive a simple formula describing the temperature dependence of
the melting field. Our theoretical predictions are in good agreement with
simulation data. The theoretical framework proposed is thermodynamically
consistent and thus capable of describing the negative magnetization jump
obtained in experiments. Such consistency is demonstrated by showing the
equivalence of our expression for the density discontinuity at the transition
with the corresponding Clausius-Clapeyron relation.Comment: 11 pages, 4 figure
Dynamical resurrection of the visibility in a Mach-Zehnder interferometer
We study a single-electron pulse injected into the chiral edge-state of a
quantum Hall device and subject to a capacitive Coulomb interaction. We find
that the scattered multi-particle state remains unentangled and hence can be
created itself by a suitable classical voltage-pulse . The application of
the inverse pulse corrects for the shake-up due to the interaction and
resurrects the original injected wave packet. We suggest an experiment with an
asymmetric Mach-Zehnder interferometer where the application of such pulses
manifests itself in an improved visibility.Comment: 4 pages, 1 figur
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