19,519 research outputs found
Discovering Regression Rules with Ant Colony Optimization
The majority of Ant Colony Optimization (ACO) algorithms for data mining have dealt with classification or clustering problems. Regression remains an unexplored research area to the best of our knowledge. This paper proposes a new ACO algorithm that generates regression rules for data mining applications. The new algorithm combines components from an existing deterministic (greedy) separate and conquer algorithm—employing the same quality metrics and continuous attribute processing techniques—allowing a comparison of the two. The new algorithm has been shown to decrease the relative root mean square error when compared to the greedy algorithm. Additionally a different approach to handling continuous attributes was investigated showing further improvements were possible
Compatible orders and fermion-induced emergent symmetry in Dirac systems
We study the quantum multicritical point in a (2+1)-dimensional Dirac system
between the semimetallic phase and two ordered phases that are characterized by
anticommuting mass terms with and symmetry, respectively.
Using expansion around the upper critical space-time dimension of
four, we demonstrate the existence of a stable renormalization-group fixed
point, enabling a direct and continuous transition between the two ordered
phases directly at the multicritical point. This point is found to be
characterized by an emergent symmetry for arbitrary values of
and and fermion flavor numbers , as long as the corresponding
representation of the Clifford algebra exists. Small -breaking
perturbations near the chiral fixed point are therefore irrelevant. This
result can be traced back to the presence of gapless Dirac degrees of freedom
at criticality, and it is in clear contrast to the purely bosonic fixed
point, which is stable only when . As a by-product, we obtain
predictions for the critical behavior of the chiral universality classes
for arbitrary and fermion flavor number . Implications for critical
Weyl and Dirac systems in 3+1 dimensions are also briefly discussed.Comment: 5+2 pages, 1 figure, 1 tabl
Mean-field scaling function of the universality class of absorbing phase transitions with a conserved field
We consider two mean-field like models which belong to the universality class
of absorbing phase transitions with a conserved field. In both cases we derive
analytically the order parameter as function of the control parameter and of an
external field conjugated to the order parameter. This allows us to calculate
the universal scaling function of the mean-field behavior. The obtained
universal function is in perfect agreement with recently obtained numerical
data of the corresponding five and six dimensional models, showing that four is
the upper critical dimension of this particular universality class.Comment: 8 pages, 2 figures, accepted for publication in J. Phys.
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