780,188 research outputs found
Implicit Methods for Equation-Free Analysis: Convergence Results and Analysis of Emergent Waves in Microscopic Traffic Models
We introduce a general formulation for an implicit equation-free method in
the setting of slow-fast systems. First, we give a rigorous convergence result
for equation-free analysis showing that the implicitly defined coarse-level
time stepper converges to the true dynamics on the slow manifold within an
error that is exponentially small with respect to the small parameter measuring
time scale separation. Second, we apply this result to the idealized traffic
modeling problem of phantom jams generated by cars with uniform behavior on a
circular road. The traffic jams are waves that travel slowly against the
direction of traffic. Equation-free analysis enables us to investigate the
behavior of the microscopic traffic model on a macroscopic level. The standard
deviation of cars' headways is chosen as the macroscopic measure of the
underlying dynamics such that traveling wave solutions correspond to equilibria
on the macroscopic level in the equation-free setup. The collapse of the
traffic jam to the free flow then corresponds to a saddle-node bifurcation of
this macroscopic equilibrium. We continue this bifurcation in two parameters
using equation-free analysis.Comment: 35 page
Free Random Levy Variables and Financial Probabilities
We suggest that Free Random Variables, represented here by large random
matrices with spectral Levy disorder, may be relevant for several problems
related to the modeling of financial systems. In particular, we consider a
financial covariance matrix composed of asymmetric and free random Levy
matrices. We derive an algebraic equation for the resolvent and solve it to
extract the spectral density. The free eigenvalue spectrum is in remarkable
agreement with the one obtained from the covariance matrix of the SP500
financial market.Comment: 8 pages with 2 EPS figures; talk given by M.A. Nowak at NATO Advanced
Research Workshop ``Applications of Physics to Economic Modeling'', Prague,
8-10 February, 200
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