48,167 research outputs found
Study of a model for the distribution of wealth
An equation for the evolution of the distribution of wealth in a population
of economic agents making binary transactions with a constant total amount of
"money" has recently been proposed by one of us (RLR). This equation takes the
form of an iterated nonlinear map of the distribution of wealth. The
equilibrium distribution is known and takes a rather simple form. If this
distribution is such that, at some time, the higher momenta of the distribution
exist, one can find exactly their law of evolution. A seemingly simple
extension of the laws of exchange yields also explicit iteration formulae for
the higher momenta, but with a major difference with the original iteration
because high order momenta grow indefinitely. This provides a quantitative
model where the spreading of wealth, namely the difference between the rich and
the poor, tends to increase with time.Comment: 12 pages, 2 figure
f(R) brane cosmology
Despite the nice features of the Dvali, Gabadadze and Porrati (DGP) model to
explain the late-time acceleration of the universe, it suffers from some
theoretical problems like the ghost issue. We present a way to self-accelerate
the normal DGP branch, which is known to be free of the ghost problem, by means
of an f(R) term on the brane action. We obtain the de Sitter self-accelerating
solutions of the model and study their stability under homogeneous
perturbations.Comment: 4 pages, 2 figures. Contribution to the proceedings of Spanish
Relativity Meeting 2009, Bilbao, Spain, 7-11 September 200
One-dimensional relativistic dissipative system with constant force and its quantization
For a relativistic particle under a constant force and a linear velocity
dissipation force, a constant of motion is found. Problems are shown for
getting the Hamiltoninan of this system. Thus, the quantization of this system
is carried out through the constant of motion and using the quantization of the
velocity variable. The dissipative relativistic quantum bouncer is outlined
within this quantization approach.Comment: 11 pages, no figure
Detecting synchronization in spatially extended discrete systems by complexity measurements
The synchronization of two stochastically coupled one-dimensional cellular
automata (CA) is analyzed. It is shown that the transition to synchronization
is characterized by a dramatic increase of the statistical complexity of the
patterns generated by the difference automaton. This singular behavior is
verified to be present in several CA rules displaying complex behavior.Comment: 4 pages, 2 figures; you can also visit
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Genetic study in patients operated dentally and anesthetized with articaine-epinephrine
Aims: In this study we wanted to figure out if there was a correlation between OPRM1 N40D, TRPV1 I316M, TRPV1 I585V, NOS3 −786T>C and IL6 −174C>G polymorphisms and the response to locally applied articaine-epinephrine anesthetic.
Methods: In this observational study, 114 oral cell samples of patients anesthetized with articaine-epinephrine (54 from men 60 from women), were collected from dental centers in Madrid (Spain). High molecular weight DNA was obtained from oral mucosa cells. The analysis of OPRM1 N40D (rs1799971), TRPV1 I316M (rs222747), TRPV1 I585V (rs8065080) and IL6 −174C>G polymorphism was performed through real-time PCR allelic discrimination using TaqMan probes. Polymorphism NOS3 −786T> C (rs2070744) was analyzed using RFLP-PCR.
Results: The studied polymorphisms are involved neither in the response to the anesthetic, nor in the intensity of perceived dental pain. However, in a subset of female patients we found that TRPV1 I316M was associated with a delayed onset of anesthesia.
Conclusions: There is no association among these polymorphisms and the time elapsed between the application of the anesthetic and the onset of its effect
Valadier-like formulas for the supremum function II: The compactly indexed case
We generalize and improve the original characterization given by Valadier
[20, Theorem 1] of the subdifferential of the pointwise supremum of convex
functions, involving the subdifferentials of the data functions at nearby
points. We remove the continuity assumption made in that work and obtain a
general formula for such a subdifferential. In particular, when the supremum is
continuous at some point of its domain, but not necessarily at the reference
point, we get a simpler version which gives rise to Valadier formula. Our
starting result is the characterization given in [10, Theorem 4], which uses
the epsilon-subdiferential at the reference point.Comment: 23 page
Lattice calculations on the spectrum of Dirac and Dirac-K\"ahler operators
We present a matrix technique to obtain the spectrum and the analytical index
of some elliptic operators defined on compact Riemannian manifolds. The method
uses matrix representations of the derivative which yield exact values for the
derivative of a trigonometric polynomial. These matrices can be used to find
the exact spectrum of an elliptic operator in particular cases and in general,
to give insight into the properties of the solution of the spectral problem. As
examples, the analytical index and the eigenvalues of the Dirac operator on the
torus and on the sphere are obtained and as an application of this technique,
the spectrum of the Dirac-Kahler operator on the sphere is explored.Comment: 11 page
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