10,311 research outputs found
The effect of temperature on generic stable periodic structures in the parameter space of dissipative relativistic standard map
In this work, we have characterized changes in the dynamics of a
two-dimensional relativistic standard map in the presence of dissipation and
specially when it is submitted to thermal effects modeled by a Gaussian noise
reservoir. By the addition of thermal noise in the dissipative relativistic
standard map (DRSM) it is possible to suppress typical stable periodic
structures (SPSs) embedded in the chaotic domains of parameter space for large
enough temperature strengths. Smaller SPSs are first affected by thermal
effects, starting from their borders, as a function of temperature. To estimate
the necessary temperature strength capable to destroy those SPSs we use the
largest Lyapunov exponent to obtain the critical temperature () diagrams.
For critical temperatures the chaotic behavior takes place with the suppression
of periodic motion, although, the temperature strengths considered in this work
are not so large to convert the deterministic features of the underlying system
into a stochastic ones.Comment: 8 pages and 7 figures, accepted to publication in EPJ
On the coupling of vector fields to the Gauss-Bonnet invariant
Inflationary models including vector fields have attracted a great deal of
attention over the past decade. Such an interest owes to the fact that they
might contribute to, or even be fully responsible for, the curvature
perturbation imprinted in the CMB. However, the necessary breaking of the
vector field's conformal invariance during inflation is not without problems.
In recent years it has been realized that a number of instabilities endangering
the consistency of the theory arise when the conformal invariance is broken by
means of a non-minimal coupling to gravity. In this paper we consider a massive
vector field non-minimally coupled to gravity through the Gauss-Bonnet
invariant, and investigate whether the vector can obtain a nearly
scale-invariant perturbation spectrum while evading the emergence of
perturbative instabilities. We find that the strength of the coupling must be
extremely small if the vector field is to have a chance to contribute to the
total curvature perturbation.Comment: 8 pages, 1 figur
The role of industry, occupation, and location specific knowledge in the survival of new firms
How do regions acquire the knowledge they need to diversify their economic
activities? How does the migration of workers among firms and industries
contribute to the diffusion of that knowledge? Here we measure the industry,
occupation, and location-specific knowledge carried by workers from one
establishment to the next using a dataset summarizing the individual work
history for an entire country. We study pioneer firms--firms operating in an
industry that was not present in a region--because the success of pioneers is
the basic unit of regional economic diversification. We find that the growth
and survival of pioneers increase significantly when their first hires are
workers with experience in a related industry, and with work experience in the
same location, but not with past experience in a related occupation. We compare
these results with new firms that are not pioneers and find that
industry-specific knowledge is significantly more important for pioneer than
non-pioneer firms. To address endogeneity we use Bartik instruments, which
leverage national fluctuations in the demand for an activity as shocks for
local labor supply. The instrumental variable estimates support the finding
that industry-related knowledge is a predictor of the survival and growth of
pioneer firms. These findings expand our understanding of the micro-mechanisms
underlying regional economic diversification events
Distributed Consensus to Enable Merging and Spacing of UAS in an Urban Environment
This paper presents a novel approach to enable multiple Unmanned Aerial Systems approaching a common intersection to independently schedule their arrival time while maintaining a safe separation. Aircraft merging at a common intersection are grouped into a network and each aircraft broadcasts its arrival time interval to the network. A distributed consensus algorithm elects a leader among the aircraft approaching the intersection and helps synchronize the information received by each aircraft. The consensus algorithm ensures that each aircraft computes a schedule with the same input information. The elected leader also dictates when a schedule must be computed, which may be triggered when a new aircraft joins the network. Preliminary results illustrating the collaborative behavior of the vehicles are presented
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