25,518 research outputs found
Directed Random Markets: Connectivity determines Money
Boltzmann-Gibbs distribution arises as the statistical equilibrium
probability distribution of money among the agents of a closed economic system
where random and undirected exchanges are allowed. When considering a model
with uniform savings in the exchanges, the final distribution is close to the
gamma family. In this work, we implement these exchange rules on networks and
we find that these stationary probability distributions are robust and they are
not affected by the topology of the underlying network. We introduce a new
family of interactions: random but directed ones. In this case, it is found the
topology to be determinant and the mean money per economic agent is related to
the degree of the node representing the agent in the network. The relation
between the mean money per economic agent and its degree is shown to be linear.Comment: 14 pages, 6 figure
Beware of the Small-World neuroscientist!
The SW has undeniably been one of the most popular network descriptors in the
neuroscience literature. Two main reasons for its lasting popularity are its
apparent ease of computation and the intuitions it is thought to provide on how
networked systems operate. Over the last few years, some pitfalls of the SW
construct and, more generally, of network summary measures, have widely been
acknowledged
Electronic heat current rectification in hybrid superconducting devices
In this work, we review and expand recent theoretical proposals for the
realization of electronic thermal diodes based on tunnel-junctions of normal
metal and superconducting thin films. Starting from the basic rectifying
properties of a single hybrid tunnel junction, we will show how the
rectification efficiency can be largely increased by combining multiple
junctions in an asymmetric chain of tunnel-coupled islands. We propose three
different designs, analyzing their performance and their potential advantages.
Besides being relevant from a fundamental physics point of view, this kind of
devices might find important technological application as fundamental building
blocks in solid-state thermal nanocircuits and in general-purpose cryogenic
electronic applications requiring energy management.Comment: 9 pages, 5 color figure
Efficient time series detection of the strong stochasticity threshold in Fermi-Pasta-Ulam oscillator lattices
In this work we study the possibility of detecting the so-called strong
stochasticity threshold, i.e. the transition between weak and strong chaos as
the energy density of the system is increased, in anharmonic oscillator chains
by means of the 0-1 test for chaos. We compare the result of the aforementioned
methodology with the scaling behavior of the largest Lyapunov exponent computed
by means of tangent space dynamics, that has so far been the most reliable
method available to detect the strong stochasticity threshold. We find that
indeed the 0-1 test can perform the detection in the range of energy density
values studied. Furthermore, we determined that conventional nonlinear time
series analysis methods fail to properly compute the largest Lyapounov exponent
even for very large data sets, whereas the computational effort of the 0-1 test
remains the same in the whole range of values of the energy density considered
with moderate size time series. Therefore, our results show that, for a
qualitative probing of phase space, the 0-1 test can be an effective tool if
its limitations are properly taken into account.Comment: 5 pages, 2 figures; accepted for publication in Physical Review
Electric charge in the field of a magnetic event in three-dimensional spacetime
We analyze the motion of an electric charge in the field of a magnetically
charged event in three-dimensional spacetime. We start by exhibiting a first
integral of the equations of motion in terms of the three conserved components
of the spacetime angular momentum, and then proceed numerically. After crossing
the light cone of the event, an electric charge initially at rest starts
rotating and slowing down. There are two lengths appearing in the problem: (i)
the characteristic length , where and are the
electric charge and mass of the particle, and is the magnetic charge of the
event; and (ii) the spacetime impact parameter . For , after a time of order , the particle makes sharply a quarter of a
turn and comes to rest at the same spatial position at which the event happened
in the past. This jump is the main signature of the presence of the magnetic
event as felt by an electric charge. A derivation of the expression for the
angular momentum that uses Noether's theorem in the magnetic representation is
given in the Appendix.Comment: Version to appear in Phys. Rev.
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