18,123 research outputs found
Symmetry Detection of Rational Space Curves from their Curvature and Torsion
We present a novel, deterministic, and efficient method to detect whether a
given rational space curve is symmetric. By using well-known differential
invariants of space curves, namely the curvature and torsion, the method is
significantly faster, simpler, and more general than an earlier method
addressing a similar problem. To support this claim, we present an analysis of
the arithmetic complexity of the algorithm and timings from an implementation
in Sage.Comment: 25 page
Involutions of polynomially parametrized surfaces
We provide an algorithm for detecting the involutions leaving a surface
defined by a polynomial parametrization invariant. As a consequence, the
symmetry axes, symmetry planes and symmetry center of the surface, if any, can
be determined directly from the parametrization, without computing or making
use of the implicit representation. The algorithm is based on the fact, proven
in the paper, that any involution of the surface comes from an involution of
the parameter space (the real plane, in our case); therefore, by determining
the latter, the former can be found. The algorithm has been implemented in the
computer algebra system Maple 17. Evidence of its efficiency for moderate
degrees, examples and a complexity analysis are also given
Detecting Similarity of Rational Plane Curves
A novel and deterministic algorithm is presented to detect whether two given
rational plane curves are related by means of a similarity, which is a central
question in Pattern Recognition. As a by-product it finds all such
similarities, and the particular case of equal curves yields all symmetries. A
complete theoretical description of the method is provided, and the method has
been implemented and tested in the Sage system for curves of moderate degrees.Comment: 22 page
Dark matter and U(1)' symmetry for the right-handed neutrinos
We consider a U(1)' gauge symmetry acting on three generations of
right-handed neutrinos. The U(1)' symmetry is broken at the TeV scale and its
remnant discrete symmetry makes one of the right-handed neutrinos stable. As a
natural consequence of the anomaly cancellation, the neutrino mass matrix
consists of a combination of Type I (TeV scale) seesaw and radiative
correction. The stable right-handed neutrino communicates with the Standard
Model via s-channel exchange of the Higgs field and the U(1)' gauge boson, so
that the observed relic density for dark matter is obtained in a wide range of
the parameter space. The experimental signatures in collider and other
experiments are briefly discussed.Comment: 16 pages, 4 figure
Lie symmetries of birational maps preserving genus 0 fibrations
Preprint.We prove that any planar birational integrable map, which preserves
a fibration given by genus curves has a Lie symmetry and some
associated invariant measures. The obtained results allow to study
in a systematic way the global dynamics of these maps. Using this
approach, the dynamics of several maps is described. In particular
we are able to give, for particular examples, the explicit
expression of the rotation number function, and the set of periods
of the considered maps.Preprin
Stationary Rotating Strings as Relativistic Particle Mechanics
Stationary rotating strings can be viewed as geodesic motions in appropriate
metrics on a two-dimensional space. We obtain all solutions describing
stationary rotating strings in flat spacetime as an application. These rotating
strings have infinite length with various wiggly shapes. Averaged value of the
string energy, the angular momentum and the linear momentum along the string
are discussed.Comment: 20pages, 7 figure
- …