197 research outputs found
A Short Introduction to Model Selection, Kolmogorov Complexity and Minimum Description Length (MDL)
The concept of overfitting in model selection is explained and demonstrated
with an example. After providing some background information on information
theory and Kolmogorov complexity, we provide a short explanation of Minimum
Description Length and error minimization. We conclude with a discussion of the
typical features of overfitting in model selection.Comment: 20 pages, Chapter 1 of The Paradox of Overfitting, Master's thesis,
Rijksuniversiteit Groningen, 200
Convergence of Income Growth Rates in Evolutionary Agent-Based Economics
We consider a heterogeneous agent-based economic model where economic agents
have strictly bounded rationality and where income allocation strategies evolve
through selective imitation. Income is calculated by a Cobb-Douglas type
production function, and selection of strategies for imitation depends on the
income growth rate they generate. We show that under these conditions, when an
agent adopts a new strategy, the effect on its income growth rate is
immediately visible to other agents, which allows a group of imitating agents
to quickly adapt their strategies when needed.Comment: 5 pages, 2 figure
Convergence of infinite element methods for scalar waveguide problems
We consider the numerical solution of scalar wave equations in domains which
are the union of a bounded domain and a finite number of infinite cylindrical
waveguides. The aim of this paper is to provide a new convergence analysis of
both the Perfectly Matched Layer (PML) method and the Hardy space infinite
element method in a unified framework. We treat both diffraction and resonance
problems. The theoretical error bounds are compared with errors in numerical
experiments
Transparent boundary conditions based on the Pole Condition for time-dependent, two-dimensional problems
The pole condition approach for deriving transparent boundary conditions is
extended to the time-dependent, two-dimensional case. Non-physical modes of the
solution are identified by the position of poles of the solution's spatial
Laplace transform in the complex plane. By requiring the Laplace transform to
be analytic on some problem dependent complex half-plane, these modes can be
suppressed. The resulting algorithm computes a finite number of coefficients of
a series expansion of the Laplace transform, thereby providing an approximation
to the exact boundary condition. The resulting error decays super-algebraically
with the number of coefficients, so relatively few additional degrees of
freedom are sufficient to reduce the error to the level of the discretization
error in the interior of the computational domain. The approach shows good
results for the Schr\"odinger and the drift-diffusion equation but, in contrast
to the one-dimensional case, exhibits instabilities for the wave and
Klein-Gordon equation. Numerical examples are shown that demonstrate the good
performance in the former and the instabilities in the latter case
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