1,890 research outputs found
Gravity in the Randall-Sundrum Brane World
We discuss the weak gravitational field created by isolated matter sources in
the Randall-Sundrum brane-world. In the case of two branes of opposite tension,
linearized Brans-Dicke (BD) gravity is recovered on either wall, with different
BD parameters. On the wall with positive tension the BD parameter is larger
than 3000 provided that the separation between walls is larger than 4 times the
AdS radius. For the wall of negative tension, the BD parameter is always
negative but greater than -3/2. In either case, shadow matter from the other
wall gravitates upon us. For equal Newtonian mass, light deflection from shadow
matter is 25 % weaker than from ordinary matter. Hence, the effective mass of a
clustered object containing shadow dark matter would be underestimated if
naively measured through its lensing effect. For the case of a single wall of
positive tension, Einstein gravity is recovered on the wall to leading order,
and if the source is stationary the field stays localized near the wall. We
calculate the leading Kaluza-Klein corrections to the linearized gravitational
field of a non-relativistic spherical object and find that the metric is
different from the Schwarzschild solution at large distances. We believe that
our linearized solution corresponds to the field far from the horizon after
gravitational collapse of matter on the brane.Comment: 8 pages, 1 figure. Replaced with revised version to be published in
Phys. Rev. Lett. Some comments adde
Canards from Chua's circuit
The aim of this work is to extend Beno\^it's theorem for the generic
existence of "canards" solutions in singularly perturbed dynamical systems of
dimension three with one fast variable to those of dimension four. Then, it is
established that this result can be found according to the Flow Curvature
Method. Applications to Chua's cubic model of dimension three and four enable
to state the existence of "canards" solutions in such systems.Comment: arXiv admin note: text overlap with arXiv:1408.489
Simultaneous occurrence of sliding and crossing limit cycles in piecewise linear planar vector fields
In the present study we consider planar piecewise linear vector fields with
two zones separated by the straight line . Our goal is to study the
existence of simultaneous crossing and sliding limit cycles for such a class of
vector fields. First, we provide a canonical form for these systems assuming
that each linear system has center, a real one for and a virtual one for
, and such that the real center is a global center. Then, working with a
first order piecewise linear perturbation we obtain piecewise linear
differential systems with three crossing limit cycles. Second, we see that a
sliding cycle can be detected after a second order piecewise linear
perturbation. Finally, imposing the existence of a sliding limit cycle we prove
that only one adittional crossing limit cycle can appear. Furthermore, we also
characterize the stability of the higher amplitude limit cycle and of the
infinity. The main techniques used in our proofs are the Melnikov method, the
Extended Chebyshev systems with positive accuracy, and the Bendixson
transformation.Comment: 24 pages, 7 figure
Reviews
Índex de l'Obra ressenyada: Alexandre JAUME I ROSSELLO, Complete works of Alexandre Jaume Rosselló. Palma: Lleonard Muntaner, 201
Melnikov analysis in nonsmooth differential systems with nonlinear switching manifold
We study the family of piecewise linear differential systems in the plane
with two pieces separated by a cubic curve. Our main result is that 7 is a
lower bound for the Hilbert number of this family. In order to get our main
result, we develop the Melnikov functions for a class of nonsmooth differential
systems, which generalizes, up to order 2, some previous results in the
literature. Whereas the first order Melnikov function for the nonsmooth case
remains the same as for the smooth one (i.e. the first order averaged function)
the second order Melnikov function for the nonsmooth case is different from the
smooth one (i.e. the second order averaged function). We show that, in this
case, a new term depending on the jump of discontinuity and on the geometry of
the switching manifold is added to the second order averaged function
Millennia of legal content criteria of lies and truths: wisdom or common-sense folly?
Long before experimental psychology, religious writers, orators, and playwrights described examples of lie detection based on the verbal content of statements. Legal scholars collected evidence from individual cases and systematized them as “rules of evidence”. Some of these resemble content cues used in contemporary research, while others point to working hypotheses worth exploring. To examine their potential validity, we re-analyzed data from a quasi-experimental study of 95 perjury cases. The outcomes support the fruitfulness of this approach. Travelling back in time searching for testable ideas about content cues to truth and deception may be worthwhile
El Derecho penal frente al terrorismo : cuestiones y perspectivas
Lliçó inaugural del curs 2005-2006
Address: The New York City Experience: Lessons For A National Future
In this address, former Mayor of New York Ed Koch discussed the successful efforts of his administration to create New York’s Campaign Finance Reform Act, a voluntary program imposing lower spending limits and detailed public disclosure requirements on candidates for the five New York City offices who chose to seek public financing. Speaking from the unique position as the first candidate to ever be fined under the Act, Mr. Koch illustrated the importance of the nonpartisan board created under the Act. He then recounted briefly the history of the program and discussed some of the specifics of the original Campaign Finance Reform Act and subsequent amendments. Mr. Koch then turned to the issue of soft money and federal reform, discussing the House’s Shays-Meehan bill and the Senate’s McCain-Feingold bill and articulating a belief that current regulations of soft money contribution limits could work, if amended to provide adjustments for inflation. Next, Mr. Koch advocated for public financing in elections and equal limits on corporate and labor union contributions. Finally, Mr. Koch listed specific reforms generally, and to New York City’s program specifically that he believed were necessary even if by amendment, such as eliminating the use of private wealth, application of contribution limits and disclosure requirements to all candidates (instead of just those seeking public financing) and restrictions on the campaign season’s time period. This transcript was taken at From the Ground Up: Local Lessons for National Reform, a national conference on campaign finance reform held on November 9, 1998, sponsored by the New York City Campaign Finance Board and the Association of the Bar of the City of New York
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