43,994 research outputs found
Local Physical Coodinates from Symplectic Projector Method
The basic arguments underlying the symplectic projector method are presented.
By this method, local free coordinates on the constrait surface can be obtained
for a broader class of constrained systems. Some interesting examples are
analyzed.Comment: 8 page
Entropic Law of Force, Emergent Gravity and the Uncertainty Principle
The entropic formulation of the inertia and the gravity relies on quantum,
geometrical and informational arguments. The fact that the results are
completly classical is missleading. In this paper we argue that the entropic
formulation provides new insights into the quantum nature of the inertia and
the gravity. We use the entropic postulate to determine the quantum uncertainty
in the law of inertia and in the law of gravity in the Newtonian Mechanics, the
Special Relativity and in the General Relativity. These results are obtained by
considering the most general quantum property of the matter represented by the
Uncertainty Principle and by postulating an expression for the uncertainty of
the entropy such that: i) it is the simplest quantum generalization of the
postulate of the variation of the entropy and ii) it reduces to the variation
of the entropy in the absence of the uncertainty.Comment: 10 pages. Important discussion of the special relativistic case and
the newtonian limit of the general relativistic case added. The paper has
been reformatted. The authorship listing corrected. (It has been published by
mistake out of order in the first version. We have been adhering to the
Hardy-Littlewood Rule over the years.) Typos corrected. Four references adde
DSMC evaluation of the Navier-Stokes shear viscosity of a granular fluid
A method based on the simple shear flow modified by the introduction of a
deterministic non-conservative force and a stochastic process is proposed to
measure the Navier-Stokes shear viscosity in a granular fluid described by the
Enskog equation. The method is implemented in DSMC simulations for a wide range
of values of dissipation and density. It is observed that, after a certain
transient period, the system reaches a hydrodynamic stage which tends to the
Navier-Stokes regime for long times. The results are compared with theoretical
predictions obtained from the Chapman-Enskog method in the leading Sonine
approximation, showing quite a good agreement, even for strong dissipation.Comment: 6 pages, 4 figures; to appear in Rarefied Gas Dynamics: 24th
International Symposium (AIP Conference Proceedings
Spin-1/2 geometric phase driven by decohering quantum fields
We calculate the geometric phase of a spin-1/2 system driven by a one and two
mode quantum field subject to decoherence. Using the quantum jump approach, we
show that the corrections to the phase in the no-jump trajectory are different
when considering an adiabatic and non-adiabatic evolution. We discuss the
implications of our results from both the fundamental as well as quantum
computational perspective.Comment: 4 page
Plane waves in noncommutative fluids
We study the dynamics of the noncommutative fuid in the Snyder space
perturbatively at the first order in powers of the noncommutative parameter.
The linearized noncommutative fluid dynamics is described by a system of
coupled linear partial differential equations in which the variables are the
fluid density and the fluid potentials. We show that these equations admit a
set of solutions that are monocromatic plane waves for the fluid density and
two of the potentials and a linear function for the third potential. The
energy-momentum tensor of the plane waves is calculated.Comment: 11 pages. Version published as a Lette
- …