12,606 research outputs found
Group-theoretical structure of quantum measurements and equivalence principle
The transverse group associated to some continuous quantum measuring
processes is analyzed in the presence of nonvanishing gravitational fields.
This is done considering, as an exmaple, the case of a particle whose
coordinates are being monitored. Employing the so called restricted path
integral formalism, it will be shown that the measuring process could always
contain information concerning the gravitational field. In other words, it
seems that with the presence of a measuring process the equivalence principle
may, in some cases, break down. The relation between the breakdown of the
equivalence principle, at quantum level, and the fact that the gravitational
field could act always as a decoherence environment, is also considered. The
phenomena of quantum beats of quantum optics will allow us to consider the
possibility that the experimental corroboration of the equivalence principle at
quantum level could be taken as an indirect evidence in favor of the
quantization of the gravitational field, i.e., the quantum properties of this
field avoid the violation of the equivalence principle.Comment: 13 pages, accepted in Modern Physics Letters
Protective circuit of the spark gap type
Spark gap type protective circuit for fast sensing and removal of overvoltage condition
Trisphere spark gap actuates overvoltage relay
Trisphere spark gap and high voltage relay provides a positive, fast response, high current capacity device that will sense an overvoltage condition and remove power from the circuit before insulation breakdown. When an overvoltage occurs, the spark gap breaks down and conducts an actuating current to the relay which removes power from the circuit
Aharonov-Bohm Effect and Coordinate Transformations
Resorting to a Gedankenexperiment which is very similar to the famous
Aharonov-Bohm proposal it will be shown that, in the case of a Minkowskian
spacetime, we may use a nonrelativistic quantum particle and a noninertial
coordinate system and obtain geometric information of regions that are, to this
particle, forbidden. This shows that the outcome of a nonrelativistic quantum
process is determined not only by the features of geometry at those points at
which the process takes place, but also by geometric parameters of regions in
which the quantum system can not enter. From this fact we could claim that
geometry at the quantum level plays a non-local role. Indeed, the measurement
outputs of some nonrelativistic quantum experiments are determined not only by
the geometry of the region in which the experiment takes place, but also by the
geometric properties of spacetime volumes which are, in some way, forbidden in
the experiment.Comment: 11 pages, 1 figure, accepted in Mod. Phys. Letts.
Networked PID control design : a pseudo-probabilistic robust approach
Networked Control Systems (NCS) are feedback/feed-forward control systems where control components (sensors, actuators and controllers) are distributed across a common communication network. In NCS, there exist network-induced random delays in each channel. This paper proposes a method to compensate the effects of these delays for the design and tuning of PID controllers. The control design is formulated as a constrained optimization problem and the controller stability and robustness criteria are incorporated as design constraints. The design is based on a polytopic description of the system using a Poisson pdf distribution of the delay. Simulation results are presented to demonstrate the performance of the proposed method
Quantum nondemolition measurements of a particle in electric and gravitational fields
In this work we obtain a nondemolition variable for the case in which a
charged particle moves in the electric and gravitational fields of a spherical
body. Afterwards we consider the continuous monitoring of this nondemolition
parameter, and calculate along the ideas of the so called restricted path
integral formalism, the corresponding propagator. Using these results the
probabilities associated with the possible measurement outputs are evaluated.
The limit of our results, as the resolution of the measuring device goes to
zero, is analyzed, and the dependence of the corresponding propagator upon the
strength of the electric and gravitational fields are commented. The role that
mass plays in the corresponding results, and its possible connection with the
equivalence principle at quantum level, are studied.Comment: Accepted in International Journal of Modern Physics D, 14 page
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