6,854 research outputs found
Wegner-Houghton equation in low dimensions
We consider scalar field theories in dimensions lower than four in the
context of the Wegner-Houghton renormalization group equations (WHRG). The
renormalized trajectory makes a non-perturbative interpolation between the
ultraviolet and the infrared scaling regimes. Strong indication is found that
in two dimensions and below the models with polynomial interaction are always
non-perturbative in the infrared scaling regime. Finally we check that these
results do not depend on the regularization and we develop a lattice version of
the WHRG in two dimensions.Comment: 44 pages, 9 figures; some sections revised, refs. added; final
version to appear in Phys. Rev.
U(1) Noncommutative Gauge Fields and Magnetogenesis
The connection between the Lorentz invariance violation in the lagrangean
context and the quantum theory of noncommutative fields is established for the
U(1) gauge field. The modified Maxwell equations coincide with other
derivations obtained using different procedures. These modified equations are
interpreted as describing macroscopic ones in a polarized and magnetized
medium. A tiny magnetic field (seed) emerges as particular static solution that
gradually increases once the modified Maxwell equations are solved as a
self-consistent equations system.Comment: 4 page
Invariants of Combinatorial Line Arrangements and Rybnikov's Example
Following the general strategy proposed by G.Rybnikov, we present a proof of
his well-known result, that is, the existence of two arrangements of lines
having the same combinatorial type, but non-isomorphic fundamental groups. To
do so, the Alexander Invariant and certain invariants of combinatorial line
arrangements are presented and developed for combinatorics with only double and
triple points. This is part of a more general project to better understand the
relationship between topology and combinatorics of line arrangements.Comment: 27 pages, 2 eps figure
Regularity of solutions to a fractional elliptic problem with mixed Dirichlet-Neumann boundary data
In this work we study regularity properties of solutions to fractional
elliptic problems with mixed Dirichlet-Neumann boundary data when dealing with
the Spectral Fractional Laplacian
Antiferromagnetic O(N) models in four dimensions
We study the antiferromagnetic O(N) model in the F_4 lattice. Monte Carlo
simulations are applied for investigating the behavior of the transition for
N=2,3. The numerical results show a first order nature but with a large
correlation length. The limit is also considered with analytical
methods.Comment: 14 pages, 3 postscript figure
Mining structured Petri nets for the visualization of process behavior
Visualization is essential for understanding the models obtained by process mining. Clear and efficient visual representations make the embedded information more accessible and analyzable. This work presents a novel approach for generating process models with structural properties that induce visually friendly layouts. Rather than generating a single model that captures all behaviors, a set of Petri net models is delivered, each one covering a subset of traces of the log. The models are mined by extracting slices of labelled transition systems with specific properties from the complete state space produced by the process logs. In most cases, few Petri nets are sufficient to cover a significant part of the behavior produced by the log.Peer ReviewedPostprint (author's final draft
Computer simulation of fatigue under diametrical compression
We study the fatigue fracture of disordered materials by means of computer
simulations of a discrete element model. We extend a two-dimensional fracture
model to capture the microscopic mechanisms relevant for fatigue, and we
simulate the diametric compression of a disc shape specimen under a constant
external force. The model allows to follow the development of the fracture
process on the macro- and micro-level varying the relative influence of the
mechanisms of damage accumulation over the load history and healing of
microcracks. As a specific example we consider recent experimental results on
the fatigue fracture of asphalt. Our numerical simulations show that for
intermediate applied loads the lifetime of the specimen presents a power law
behavior. Under the effect of healing, more prominent for small loads compared
to the tensile strength of the material, the lifetime of the sample increases
and a fatigue limit emerges below which no macroscopic failure occurs. The
numerical results are in a good qualitative agreement with the experimental
findings.Comment: 7 pages, 8 figures, RevTex forma
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