1,174 research outputs found
Cross-Lingual Adaptation using Structural Correspondence Learning
Cross-lingual adaptation, a special case of domain adaptation, refers to the
transfer of classification knowledge between two languages. In this article we
describe an extension of Structural Correspondence Learning (SCL), a recently
proposed algorithm for domain adaptation, for cross-lingual adaptation. The
proposed method uses unlabeled documents from both languages, along with a word
translation oracle, to induce cross-lingual feature correspondences. From these
correspondences a cross-lingual representation is created that enables the
transfer of classification knowledge from the source to the target language.
The main advantages of this approach over other approaches are its resource
efficiency and task specificity.
We conduct experiments in the area of cross-language topic and sentiment
classification involving English as source language and German, French, and
Japanese as target languages. The results show a significant improvement of the
proposed method over a machine translation baseline, reducing the relative
error due to cross-lingual adaptation by an average of 30% (topic
classification) and 59% (sentiment classification). We further report on
empirical analyses that reveal insights into the use of unlabeled data, the
sensitivity with respect to important hyperparameters, and the nature of the
induced cross-lingual correspondences
Spatiotemporal Oscillation Patterns in the Collective Relaxation Dynamics of Interacting Particles in Periodic Potentials
We demonstrate the emergence of self-organized structures in the course of
the relaxation of an initially excited, dissipative and finite chain of
interacting particles in a periodic potential towards its many particle
equilibrium configuration. Specifically we observe a transition from an in
phase correlated motion via phase randomized oscillations towards oscillations
with a phase difference between adjacent particles thereby yielding the
growth of long time transient spatiotemporal oscillation patterns. Parameter
modifications allow for designing these patterns, including steady states and
even states that combine in phase and correlated out of phase oscillations
along the chain. The complex relaxation dynamics is based on finite size
effects together with an evolution running from the nonlinear to the linear
regime thereby providing a highly unbalanced population of the center of mass
and relative motion
Disorder-induced regular dynamics in oscillating lattices
We explore the impact of weak disorder on the dynamics of classical particles
in a periodically oscillating lattice. It is demonstrated that the disorder
induces a hopping process from diffusive to regular motion i.e. we observe the
counterintuitive phenomenon that disorder leads to regular behaviour. If the
disorder is localized in a finite-sized part of the lattice, the described
hopping causes initially diffusive particles to even accumulate in regular
structures of the corresponding phase space. A hallmark of this accumulation is
the emergence of pronounced peaks in the velocity distribution of particles
which should be detectable in state of the art experiments e.g. with cold atoms
in optical lattices
Site-selective particle deposition in periodically driven quantum lattices
We demonstrate that a site-dependent driving of a periodic potential allows
for the controlled manipulation of a quantum particle on length scales of the
lattice spacing. Specifically we observe for distinct driving frequencies a
near depletion of certain sites which is explained by a resonant mixing of the
involved Floquet-Bloch modes occurring at these frequencies. Our results could
be exploited as a scheme for a site-selective loading of e.g. ultracold atoms
into an optical lattices
Quench Dynamics of Two Coupled Ionic Zig-Zag Chains
We explore the non-equilibrium dynamics of two coupled zig-zag chains of
trapped ions in a double well potential. Following a quench of the potential
barrier between both wells, the induced coupling between both chains due to the
long-range interaction of the ions leads to their complete melting. The
resulting dynamics is however not exclusively irregular but leads to phases of
motion during which various ordered structures appear with ions arranged in
arcs, lines and crosses. We quantify the emerging order by introducing a
suitable measure and complement our analysis of the ion dynamics using a normal
mode analysis showing a decisive population transfer between only a few
distinguished modes
Simultaneous control of multi-species particle transport and segregation in driven lattices
We provide a generic scheme to separate the particles of a mixture by their
physical properties like mass, friction or size. The scheme employs a
periodically shaken two dimensional dissipative lattice and hinges on a
simultaneous transport of particles in species-specific directions. This
selective transport is achieved by controlling the late-time nonlinear particle
dynamics, via the attractors embedded in the phase space and their
bifurcations. To illustrate the spectrum of possible applications of the
scheme, we exemplarily demonstrate the separation of polydisperse colloids and
mixtures of cold thermal alkali atoms in optical lattices
Patterned Deposition of Particles in Spatio-temporally Driven Lattices
We present and analyze mechanisms for the patterned deposition of particles
in a spatio-temporally driven lattice. The working principle is based on the
breaking of the spatio-temporal translation symmetry, which is responsible for
the equivalence of all lattice sites, by applying modulated phase shifts to the
lattice sites. The patterned trapping of the particles occurs in confined
chaotic seas, created via the ramping of the height of the lattice potential.
Complex density profiles on the length scale of the complete lattice can be
obtained by a quasi-continuous, spatial deformation of the chaotic sea in a
frequency modulated lattice.Comment: 5 pages, 4 figure
Symmetries and transport in site-dependently driven quantum lattices
We explore the quantum dynamics of particles in a spatiotemporally driven
lattice. A powerful numerical scheme is developed, which provides us with the
Floquet modes and thus enables a stroboscopic propagation of arbitrary initial
states. A detailed symmetry analysis represents the cornerstone for an
intricate manipulation of the Floquet spectrum. Specifically, we show how exact
crossings can be converted into avoided ones, while the width of these
resulting avoided crossings can be engineered by adjusting parameters of the
local driving. Asymptotic currents are shown to be controllable over a certain
parameter range
Dimensional coupling induced current reversal in two-dimensional driven lattices
We show that the direction of directed particle transport in a two
dimensional ac-driven lattice can be dynamically reversed by changing the
structure of the lattice in the direction perpendicular to the applied driving
force. These structural changes introduce dimensional coupling effects, the
strength of which governs the timescale of the current reversals. The
underlying mechanism is based on the fact that dimensional coupling allows the
particles to explore regions of phase space which are inaccessible otherwise.
The experimental realization for cold atoms in ac-driven optical lattices is
discussed
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