1,454,929 research outputs found
Generalized Force Model of Traffic Dynamics
Floating car data of car-following behavior in cities were compared to
existing microsimulation models, after their parameters had been calibrated to
the experimental data. With these parameter values, additional simulations have
been carried out, e.g. of a moving car which approaches a stopped car. It
turned out that, in order to manage such kinds of situations without producing
accidents, improved traffic models are needed. Good results have been obtained
with the proposed generalized force model.Comment: For related work see
http://www.theo2.physik.uni-stuttgart.de/helbing.htm
Oscillating cosmological force modifies Newtonian dynamics
In the Newtonian limit of general relativity force acting on a test mass in a
central gravitational field is conventionally defined by the attractive
Newtonian gravity (inverse square) term plus a small repulsive cosmological
force, which is proportional to the slow acceleration of the universe
expansion. In this paper we consider the cosmological force correction due to
fast quantum oscillations of the universe scale factor, which were suggested
recently by Wang et al. (Phys. Rev. D 95, 103504 (2017)) as a potential
solution of the cosmological constant problem. These fast fluctuations of the
cosmological scale factor induce strong changes to the current sign and
magnitude of the average cosmological force, thus making it one of the
potential probable causes of the modification of Newtonian dynamics in
galaxy-scale systems. The modified cosmological force may be responsible for
the recently discovered "cosmic clock" behaviour of disk galaxies in the low
redshift universe.Comment: 17 pages, 3 figure
Force in Kappa-Deformed Relativistic Dynamics
We consider the physical implications of various choices of the
three-momentum basis in the kappa-deformed Poincare algebra. In particular, we
find that the energy dependence of the velocity of a kappa-particle leads to
unexpected features in kappa-deformed kinematics. We also discuss the notion of
kappa-deformed dynamics, and as a tool example we investigate the motion of a
kappa-deformed particle under the action of a constant force.Comment: LaTeX, 9 page
The Stochastic Dynamics of an Array of Atomic Force Microscopes in a Viscous Fluid
We consider the stochastic dynamics of an array of two closely spaced atomic
force microscope cantilevers in a viscous fluid for use as a possible
biomolecule sensor. The cantilevers are not driven externally, as is common in
applications of atomic force microscopy, and we explore the stochastic
cantilever dynamics due to the constant buffeting of fluid particles by
Brownian motion. The stochastic dynamics of two adjacent cantilevers are
correlated due to long range effects of the viscous fluid. Using a recently
proposed thermodynamic approach the hydrodynamic correlations are quantified
for precise experimental conditions through deterministic numerical
simulations. Results are presented for an array of two readily available atomic
force microscope cantilevers. It is shown that the force on a cantilever due to
the fluid correlations with an adjacent cantilever is more than 3 times smaller
than the Brownian force on an individual cantilever. Our results indicate that
measurements of the correlations in the displacement of an array of atomic
force microscopes can detect piconewton forces with microsecond time
resolution.Comment: 7 page article with 11 images submitted to the International Journal
of Nonlinear Mechanic
Relativistic Newtonian Dynamics for Objects and Particles
Relativistic Newtonian Dynamics (RND) was introduced in a series of recent
papers by the author, in partial cooperation with J. M. Steiner. RND was
capable of describing non-classical behavior of motion under a central
attracting force. RND incorporates the influence of potential energy on
spacetime in Newtonian dynamics, treating gravity as a force in flat spacetime.
It was shown that this dynamics predicts accurately gravitational time
dilation, the anomalous precession of Mercury and the periastron advance of any
binary.
In this paper the model is further refined and extended to describe also the
motion of both objects with non-zero mass and massless particles, under a
conservative attracting force. It is shown that for any conservative force a
properly defined energy is conserved on the trajectories and if this force is
central, the angular momentum is also preserved. An RND equation of motion is
derived for motion under a conservative force. As an application, it is shown
that RND predicts accurately also the Shapiro time delay - the fourth test of
GR.Comment: 5 pages , 1 figur
Relativistic Dynamics of Point Magnetic Moment
The covariant motion of a classical point particle with magnetic moment in
the presence of (external) electromagnetic fields is revisited. We are
interested in understanding Lorentz force extension involving point particle
magnetic moment (Stern-Gerlach force) and how the spin precession dynamics is
modified for consistency. We introduce spin as a classical particle property
inherent to Poincare\'e symmetry of space-time. We propose a covariant
formulation of the magnetic force based on a \lq magnetic\rq\ 4-potential and
show how the point particle magnetic moment relates to the Amperian (current
loop) and Gilbertian (magnetic monopole) description. We show that covariant
spin precession lacks a unique form and discuss connection to anomaly. We
consider variational action principle and find that a consistent extension of
Lorentz force to include magnetic spin force is not straightforward. We look at
non-covariant particle dynamics, and present a short introduction to dynamics
of (neutral) particles hit by a laser pulse of arbitrary shape.Comment: 11 page
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