2,185 research outputs found
Ubiquity of optical activity in planar metamaterial scatterers
Recently it was discovered that periodic lattices of metamaterial scatterers
show optical activity, even if the scatterers or lattice show no 2D or 3D
chirality, if the illumination breaks symmetry. In this Letter we demonstrate
that such `pseudo-chirality' is intrinsic to any single planar metamaterial
scatterer and in fact has a well-defined value at a universal bound. We argue
that in any circuit model, a nonzero electric and magnetic polarizability
derived from a single resonance automatically imply strong bianisotropy, i.e.,
magneto-electric cross polarizability at the universal bound set by energy
conservation. We confirm our claim by extracting polarizability tensors and
cross sections for handed excitation from transmission measurements on
near-infrared split ring arrays, and electrodynamic simulations for diverse
metamaterial scatterers.Comment: 5 pages, 4 figure
Description of Fischer Clusters Formation in Supercooled Liquids Within Framework of Continual Theory of Defects
Liquid is represented as complicated system of disclinations according to
defect description of liquids and glasses. The expressions for the linear
disclination field of an arbitrary form and energy of inter-disclination
interaction are derived in the framework of gauge theory of defects. It allows
us to describe liquid as a disordered system of topological moments and reduce
this model to the Edwards--Anderson model with large-range interaction. Within
the framework of this approach vitrifying is represented as a "hierarchical"
phase transition. The suggested model allows us to explain the process of the
Fischer clusters formation and the slow dynamics in supercooled liquids close
to the liquid--glass transition point
Numerical solution of the viscous flow past a cylinder with a non-global yet spectrally convergent meshless collocation method
Proceeding of: 11th International Conference on Spectral and High-Order Methods (ICOSAHOM'16), June 27-July 1, 2016, Rio de Janeiro, Brazil.The flow of a viscous fluid past a cylinder is a classical problem in fluid-structure interaction and a benchmark for numerical methods in computational fluid dynamics. We solve it with the recently introduced radial basis function-based partition of unity method (RBF-PUM), which is a spectrally convergent collocation meshless scheme well suited to this kind of problem. The resulting discrete system of nonlinear equations is tackled with a trust-region algorithm, whose performance is much enhanced by the analytic Jacobian which is provided alongside. Preliminary results up to Re = 60 with just 1292 nodes are shown.F. Bernal acknowledges support from FCT grant SFRH/BPD/79986/2011 and INESC-ID. A. Heryudono is partially supported by NSF Grant DMS 1552238Publicad
Two-neutron halo nuclei in one dimension: dineutron correlation and breakup reaction
We propose a simple schematic model for two-neutron halo nuclei. In this
model, the two valence neutrons move in a one-dimensional mean field,
interacting with each other via a density-dependent contact interaction. We
first investigate the ground state properties, and demonstrate that the
dineutron correlation can be realized with this simple model due to the
admixture of even- and odd-parity single-particle states. We then solve the
time-dependent two-particle Schr\"odinger equation under the influence of a
time-dependent one-body external field, in order to discuss the effect of
dineutron correlation on nuclear breakup processes. The time evolution of
two-particle density shows that the dineutron correlation enhances the total
breakup probability, especially for the two-neutron breakup process, in which
both the valence neutrons are promoted to continuum scattering states. We find
that the interaction between the two particles definitely favours a spatial
correlation of the two outgoing particles, which are mainly emitted in the same
direction.Comment: 17 pages, 11 figure
Space-time extensions II
The global extendibility of smooth causal geodesically incomplete spacetimes
is investigated. Denote by one of the incomplete non-extendible causal
geodesics of a causal geodesically incomplete spacetime . First, it
is shown that it is always possible to select a synchronised family of causal
geodesics and an open neighbourhood of a final segment
of in such that is comprised by members of ,
and suitable local coordinates can be defined everywhere on
provided that does not terminate either on a tidal force tensor
singularity or on a topological singularity. It is also shown that if, in
addition, the spacetime, , is globally hyperbolic, and the
components of the curvature tensor, and its covariant derivatives up to order
are bounded on , and also the line integrals of the
components of the -order covariant derivatives are finite along the
members of ---where all the components are meant to be registered with
respect to a synchronised frame field on ---then there exists a
extension so that for each , which
is inextendible in , the image, , is
extendible in . Finally, it is also proved that
whenever does terminate on a topological singularity
cannot be generic.Comment: 42 pages, no figures, small changes to match the published versio
Columnar and lamellar phases in attractive colloidal systems
In colloidal suspensions, the competition between attractive and repulsive
interactions gives rise to a rich and complex phenomenology. Here, we study the
equilibrium phase diagram of a model system using a DLVO interaction potential
by means of molecular dynamics simulations and a thermodynamical approach. As a
result, we find tubular and lamellar phases at low volume fraction. Such
phases, extremely relevant for designing new materials, may be not easily
observed in the experiments because of the long relaxation times and the
presence of defects.Comment: 5 pages, 5 figure
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