1,305 research outputs found
Prediction of quantum stripe ordering in optical lattices
We predict the robust existence of a novel quantum orbital stripe order in
the -band Bose-Hubbard model of two-dimensional triangular optical lattices
with cold bosonic atoms. An orbital angular momentum moment is formed on each
site exhibiting a stripe order both in the superfluid and Mott-insulating
phases. The stripe order spontaneously breaks time-reversal, lattice
translation and rotation symmetries. In addition, it induces staggered
plaquette bond currents in the superfluid phase. Possible signatures of this
stripe order in the time of flight experiment are discussed.Comment: 4 pages, three figures, accepted by Phys. Rev. Let
Lattice four-dimensional N=4 SYM is practical
We show that nonperturbative lattice studies of four-dimensional N=4
Super-Yang-Mills are within reach. We use Ginsparg-Wilson fermions to avoid
gluino masses and an exact implementation of the (chiral) -symmetry, which
greatly limits the number of counterterms that must be fine-tuned. Only bosonic
operators require fine tuning, so all tunings can be done ``offline'' by a
Ferrenberg-Swendsen type reweighting. We show what measurables can be used to
perform the tuning.Comment: 4 page
Human-scale economics: Economic growth and poverty reduction in Northeastern Thailand
Ministry of Education, Singapore under its Academic Research Funding Tier
Incompressible Quantum Liquids and New Conservation Laws
In this letter we investigate a class of Hamiltonians which, in addition to
the usual center-of-mass (CM) momentum conservation, also have center-of-mass
position conservation. We find that regardless of the particle statistics, the
energy spectrum is at least q-fold degenerate when the filling factor is ,
where and are coprime integers. Interestingly the simplest Hamiltonian
respecting this type of symmetry encapsulates two prominent examples of novel
states of matter, namely the fractional quantum Hall liquid and the quantum
dimer liquid. We discuss the relevance of this class of Hamiltonian to the
search for featureless Mott insulators.Comment: updated version, to be published by PR
Quantum transport and two-parameter scaling at the surface of a weak topological insulator
Weak topological insulators have an even number of Dirac cones in their
surface spectrum and are thought to be unstable to disorder, which leads to an
insulating surface. Here we argue that the presence of disorder alone will not
localize the surface states, rather; the presence of a time-reversal symmetric
mass term is required for localization. Through numerical simulations, we show
that in the absence of the mass term the surface always flow to a stable
metallic phase and the conductivity obeys a one-parameter scaling relation,
just as in the case of a strong topological insulator surface. With the
inclusion of the mass, the transport properties of the surface of a weak
topological insulator follow a two-parameter scaling form.Comment: 4 pages + Appendices, v2 added conductance distributio
Optimization of neural network architecture using genetic programming improves detection and modeling of gene-gene interactions in studies of human diseases
BACKGROUND: Appropriate definition of neural network architecture prior to data analysis is crucial for successful data mining. This can be challenging when the underlying model of the data is unknown. The goal of this study was to determine whether optimizing neural network architecture using genetic programming as a machine learning strategy would improve the ability of neural networks to model and detect nonlinear interactions among genes in studies of common human diseases. RESULTS: Using simulated data, we show that a genetic programming optimized neural network approach is able to model gene-gene interactions as well as a traditional back propagation neural network. Furthermore, the genetic programming optimized neural network is better than the traditional back propagation neural network approach in terms of predictive ability and power to detect gene-gene interactions when non-functional polymorphisms are present. CONCLUSION: This study suggests that a machine learning strategy for optimizing neural network architecture may be preferable to traditional trial-and-error approaches for the identification and characterization of gene-gene interactions in common, complex human diseases
Nonlinear Radiation Pressure and Stochasticity in Ultraintense Laser Fields
The radiation force on a single electron in an ultraintense plane wave () is calculated and shown to be proportional to in the
high- limit for arbitrary waveform and polarization. The cyclotron motion of
an electron in a constant magnetic field and an ultraintense plane wave is
numerically found to be quasiperiodic even in the high- limit if the
magnetic field is not too strong, as suggested by previous analytical work. A
strong magnetic field causes highly chaotic electron motion and the boundary of
the highly chaotic region of parameter space is determined numerically.
Applications to experiments and astrophysics are briefly discussed.Comment: 5 pages, 4 figures; uses RevTex, epsf macros. Corrected, expanded
versio
- …