2,604 research outputs found
Roll tracking effects of G-vector tilt and various types of motion washout
In a dogfight scenario, the task was to follow the target's roll angle while suppressing gust disturbances. All subjects adopted the same behavioral strategies in following the target while suppressing the gusts, and the MFP-fitted math model response was generally within one data symbol width. The results include the following: (1) comparisons of full roll motion (both with and without the spurious gravity tilt cue) with the static case. These motion cues help suppress disturbances with little net effect on the visual performance. Tilt cues were clearly used by the pilots but gave only small improvement in tracking errors. (2) The optimum washout (in terms of performance close to real world, similar behavioral parameters, significant motion attenuation (60 percent), and acceptable motion fidelity) was the combined attenuation and first-order washout. (3) Various trends in parameters across the motion conditions were apparent, and are discussed with respect to a comprehensive model for predicting adaptation to various roll motion cues
Coherent states for polynomial su(1,1) algebra and a conditionally solvable system
In a previous paper [{\it J. Phys. A: Math. Theor.} {\bf 40} (2007) 11105],
we constructed a class of coherent states for a polynomially deformed
algebra. In this paper, we first prepare the discrete representations of the
nonlinearly deformed algebra. Then we extend the previous procedure
to construct a discrete class of coherent states for a polynomial su(1,1)
algebra which contains the Barut-Girardello set and the Perelomov set of the
SU(1,1) coherent states as special cases. We also construct coherent states for
the cubic algebra related to the conditionally solvable radial oscillator
problem.Comment: 2 figure
Extreme tunability of interactions in a Li Bose-Einstein condensate
We use a Feshbach resonance to tune the scattering length a of a
Bose-Einstein condensate of 7Li in the |F = 1, m_F = 1> state. Using the
spatial extent of the trapped condensate we extract a over a range spanning 7
decades from small attractive interactions to extremely strong repulsive
interactions. The shallow zero-crossing in the wing of the Feshbach resonance
enables the determination of a as small as 0.01 Bohr radii. In this regime,
evidence of the weak anisotropic magnetic dipole interaction is obtained by
comparison with different trap geometries
Construction of classical superintegrable systems with higher order integrals of motion from ladder operators
We construct integrals of motion for multidimensional classical systems from
ladder operators of one-dimensional systems. This method can be used to obtain
new systems with higher order integrals. We show how these integrals generate a
polynomial Poisson algebra. We consider a one-dimensional system with third
order ladders operators and found a family of superintegrable systems with
higher order integrals of motion. We obtain also the polynomial algebra
generated by these integrals. We calculate numerically the trajectories and
show that all bounded trajectories are closed.Comment: 10 pages, 4 figures, to appear in j.math.phys
Intertwining relations of non-stationary Schr\"odinger operators
General first- and higher-order intertwining relations between non-stationary
one-dimensional Schr\"odinger operators are introduced. For the first-order
case it is shown that the intertwining relations imply some hidden symmetry
which in turn results in a -separation of variables. The Fokker-Planck and
diffusion equation are briefly considered. Second-order intertwining operators
are also discussed within a general approach. However, due to its complicated
structure only particular solutions are given in some detail.Comment: 18 pages, LaTeX20
Topological methods for searching barriers and reaction paths
We present a family of algorithms for the fast determination of reaction
paths and barriers in phase space and the computation of the corresponding
rates. The method requires the reaction times be large compared to the
microscopic time, irrespective of the origin - energetic, entropic, cooperative
- of the timescale separation. It lends itself to temperature cycling as in
simulated annealing and to activation-relaxation routines. The dynamics is
ultimately based on supersymmetry methods used years ago to derive Morse
theory. Thus, the formalism automatically incorporates all relevant topological
information.Comment: 4 pages, 4 figures, RevTex
Improved approximate inspirals of test-bodies into Kerr black holes
We present an improved version of the approximate scheme for generating
inspirals of test-bodies into a Kerr black hole recently developed by
Glampedakis, Hughes and Kennefick. Their original "hybrid" scheme was based on
combining exact relativistic expressions for the evolution of the orbital
elements (the semi-latus rectum p and eccentricity e) with approximate,
weak-field, formula for the energy and angular momentum fluxes, amended by the
assumption of constant inclination angle, iota, during the inspiral. Despite
the fact that the resulting inspirals were overall well-behaved, certain
pathologies remained for orbits in the strong field regime and for orbits which
are nearly circular and/or nearly polar. In this paper we eliminate these
problems by incorporating an array of improvements in the approximate fluxes.
Firstly, we add certain corrections which ensure the correct behaviour of the
fluxes in the limit of vanishing eccentricity and/or 90 degrees inclination.
Secondly, we use higher order post-Newtonian formulae, adapted for generic
orbits. Thirdly, we drop the assumption of constant inclination. Instead, we
first evolve the Carter constant by means of an approximate post-Newtonian
expression and subsequently extract the evolution of iota. Finally, we improve
the evolution of circular orbits by using fits to the angular momentum and
inclination evolution determined by Teukolsky based calculations. As an
application of the improved scheme we provide a sample of generic Kerr
inspirals and for the specific case of nearly circular orbits we locate the
critical radius where orbits begin to decircularise under radiation reaction.
These easy-to-generate inspirals should become a useful tool for exploring LISA
data analysis issues and may ultimately play a role in source detection.Comment: 25 pages, 14 figures, some typos corrected, short section on
conservative corrections added, minor changes for consistency with published
versio
Motion of a spin 1/2 particle in shape invariant scalar and magnetic fields
We study the motion of a spin 1/2 particle in a scalar as well as a magnetic
field within the framework of supersymmetric quantum mechanics(SUSYQM). We also
introduce the concept of shape invariant scalar and magnetic fields and it is
shown that the problem admits exact analytical solutions when such fields are
considered.Comment: 14 page
Supersymmetry of a Nonstationary Pauli Equation
The supersymmetry of the electron in both the nonstationary magnetic and
electric fields in a two-dimensional case is studied. The supercharges which
are the integrals of motion and their algebra are established. Using the
obtained algebra the solutions of nonstationary Pauli equation are generated.Comment: 12 pages, Late
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