2,117 research outputs found
Dual-carrier Floquet circulator with time-modulated optical resonators
Spatio-temporal modulation has shown great promise as a strong time-reversal
symmetry breaking mechanism that enables integrated nonreciprocal devices and
topological materials at optical frequencies. However, optical modulation has
its own constraints in terms of modulation index and frequency, which limit the
bandwidth and miniaturization of circulators and isolators, not unlike the
magneto-optical schemes that it promises to replace. Here we propose and
numerically demonstrate a Floquet circulator that leverages the untapped
degrees of freedom unique to time-modulated resonators. Excited by
sideband-selective waveguides, the system supports broadband nonreciprocal
transmission without relying on the mirror or rotational symmetries required in
conventional circulators. Cascading two resonators, we create a linear
three-port circulator that exhibits complete and frequency-independent forward
transmission between two of the ports. This approach enables wavelength-scale
circulators that can rely on a variety of modulation mechanisms
Quantum Dynamics in a Time-dependent Hard-Wall Spherical Trap
Exact solution of the Schr\"{o}dinger equation is given for a particle inside
a hard sphere whose wall is moving with a constant velocity. Numerical
computations are presented for both contracting and expanding spheres. The
propagator is constructed and compared with the propagator of a particle in an
infinite square well with one wall in uniform motion.Comment: 6 pages, 4 figures, Accepted by Europhys. Let
Quantum effective force in an expanding infinite square-well potential and Bohmian perspective
The Schr\"{o}dinger equation is solved for the case of a particle confined to
a small region of a box with infinite walls. If walls of the well are moved,
then, due to an effective quantum nonlocal interaction with the boundary, even
though the particle is nowhere near the walls, it will be affected. It is shown
that this force apart from a minus sign is equal to the expectation value of
the gradient of the quantum potential for vanishing at the walls boundary
condition. Variation of this force with time is studied. A selection of Bohmian
trajectories of the confined particle is also computed.Comment: 7 figures, Accepted by Physica Script
Multi-task Image Classification via Collaborative, Hierarchical Spike-and-Slab Priors
Promising results have been achieved in image classification problems by
exploiting the discriminative power of sparse representations for
classification (SRC). Recently, it has been shown that the use of
\emph{class-specific} spike-and-slab priors in conjunction with the
class-specific dictionaries from SRC is particularly effective in low training
scenarios. As a logical extension, we build on this framework for multitask
scenarios, wherein multiple representations of the same physical phenomena are
available. We experimentally demonstrate the benefits of mining joint
information from different camera views for multi-view face recognition.Comment: Accepted to International Conference in Image Processing (ICIP) 201
Robustness of Equations Under Operational Extensions
Sound behavioral equations on open terms may become unsound after
conservative extensions of the underlying operational semantics. Providing
criteria under which such equations are preserved is extremely useful; in
particular, it can avoid the need to repeat proofs when extending the specified
language.
This paper investigates preservation of sound equations for several notions
of bisimilarity on open terms: closed-instance (ci-)bisimilarity and
formal-hypothesis (fh-)bisimilarity, both due to Robert de Simone, and
hypothesis-preserving (hp-)bisimilarity, due to Arend Rensink. For both
fh-bisimilarity and hp-bisimilarity, we prove that arbitrary sound equations on
open terms are preserved by all disjoint extensions which do not add labels. We
also define slight variations of fh- and hp-bisimilarity such that all sound
equations are preserved by arbitrary disjoint extensions. Finally, we give two
sets of syntactic criteria (on equations, resp. operational extensions) and
prove each of them to be sufficient for preserving ci-bisimilarity.Comment: In Proceedings EXPRESS'10, arXiv:1011.601
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