1,117 research outputs found
Design and Experiments with a Low-Cost Single-Motor Modular Aquatic Robot
We present a novel design for a low-cost robotic boat powered by a single
actuator, useful for both modular and swarming applications. The boat uses the
conservation of angular momentum and passive flippers to convert the motion of
a single motor into an adjustable paddling motion for propulsion and steering.
We develop design criteria for modularity and swarming and present a prototype
implementing these criteria. We identify significant mechanical sensitivities
with the presented design, theorize about the cause of the sensitivities, and
present an improved design for future work.Comment: Accepted to the International Conference on Ubiquitous Robots (UR
2020). 8 page
The Conformal Mode in 2D Simplicial Gravity
We verify that summing 2D DT geometries correctly reproduces the Polyakov
action for the conformal mode, including all ghost contributions, at large
volumes. The Gaussian action is reproduced even for c=10, well into the
branched polymer phase, which confirms the expectation that the DT measure is
indeed correct in this regime as well.Comment: 13 pages, 8 figure
Nonlinear MHD waves in a Prominence Foot
We study nonlinear waves in a prominence foot using 2.5D MHD model motivated
by recent high-resolution observations with Hinode/SOT in Ca~II emission of a
prominence on October 10, 2012 showing highly dynamic small-scale motions in
the prominence material. Observations of H intensities and of Doppler
shifts show similar propagating fluctuations. However the optically thick
nature of the emission lines inhibits unique quantitative interpretation in
terms of density. Nevertheless, we find evidence of nonlinear wave activity in
the prominence foot by examining the relative magnitude of the fluctuation
intensity (). The waves are evident as significant
density fluctuations that vary with height, and apparently travel upward from
the chromosphere into the prominence material with quasi-periodic fluctuations
with typical period in the range of 5-11 minutes, and wavelengths 2000
km. Recent Doppler shift observations show the transverse displacement of the
propagating waves. The magnetic field was measured with THEMIS instrument and
was found to be 5-14 G. For the typical prominence density the corresponding
fast magnetosonic speed is 20 km s, in qualitative agreement with
the propagation speed of the detected waves. The 2.5D MHD numerical model is
constrained with the typical parameters of the prominence waves seen in
observations. Our numerical results reproduce the nonlinear fast magnetosonic
waves and provide strong support for the presence of these waves in the
prominence foot. We also explore gravitational MHD oscillations of the heavy
prominence foot material supported by dipped magnetic field structure
Coulomb Gas Representation of the SU(2) WZW Correlators at Higher Genera
We express the correlation functions of the SU(2) WZW conformal field theory
on Riemann surfaces of genus >1 by finite dimensional integrals.Comment: 9 pages, late
Measure in the 2D Regge quantum gravity
We propose a version of the 2D Regge calculus, in which the areas of all
triangles are equal to each other. In this discretization Lund - Regge measure
over link lengths is simplified considerably. Contrary to the usual Regge
models with Lund - Regge measure, where this measure is nonlocal and rather
complicated, the models based on our approach can be investigated using the
numerical simulations in a rather simple way.Comment: Derivation of the basic result is reconsidered. Accepted for
publication in Phys. Lett.
Singular vectors by Fusions in affine su(2)
Explicit expressions for the singular vectors in the highest weight
representations of are obtained using the fusion formalism of
conformal field theory.Comment: 7 page
Matrix models as conformal field theories: genus expansion
We obtain the topological expansion of the hermitian matrix model using its
representation as a CFT on a hyperelliptic Riemann surface. To each branch
point of the Riemann surface we associate an operator which represents a twist
field dressed by the modes of the twisted boson. The partition function of the
matrix model is computed as a correlation function of such dressed twist
fields. The perturbative construction of the dressing operators yields a set of
Feynman rules for evaluating the free energy and the loop observables at any
genus.Comment: 17 pages, 4 figure
Nanotube-based scanning rotational microscope
A scheme of the scanning rotational microscope is designed. This scheme is
based on using carbon nanotubes simultaneously as a probe tip and as a bolt/nut
pair which converts translational displacements of two piezo actuators into
pure rotation of the probe tip. First-principles calculations of the
interaction energy between movable and rotational parts of the microscope
confirms the capability for its operation. The scanning rotational microscope
with a chemically functionalized nanotube-based tip can be used to study how
the interaction between individual molecules or a molecule and a surface
depends on their relative orientation.Comment: 4 pages, 3 figure
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