113,244 research outputs found
BFACF-style algorithms for polygons in the body-centered and face-centered cubic lattices
In this paper the elementary moves of the BFACF-algorithm for lattice
polygons are generalised to elementary moves of BFACF-style algorithms for
lattice polygons in the body-centred (BCC) and face-centred (FCC) cubic
lattices. We prove that the ergodicity classes of these new elementary moves
coincide with the knot types of unrooted polygons in the BCC and FCC lattices
and so expand a similar result for the cubic lattice. Implementations of these
algorithms for knotted polygons using the GAS algorithm produce estimates of
the minimal length of knotted polygons in the BCC and FCC lattices
Polygonal valuations
AbstractWe develop a valuation theory for generalized polygons similar to the existing theory for dense near polygons. This valuation theory has applications for the study and classification of generalized polygons that have full subpolygons as subgeometries
Osculating and neighbour-avoiding polygons on the square lattice
We study two simple modifications of self-avoiding polygons. Osculating
polygons are a super-set in which we allow the perimeter of the polygon to
touch at a vertex. Neighbour-avoiding polygons are only allowed to have nearest
neighbour vertices provided these are joined by the associated edge and thus
form a sub-set of self-avoiding polygons. We use the finite lattice method to
count the number of osculating polygons and neighbour-avoiding polygons on the
square lattice. We also calculate their radius of gyration and the first
area-weighted moment. Analysis of the series confirms exact predictions for the
critical exponents and the universality of various amplitude combinations. For
both cases we have found exact solutions for the number of convex and
almost-convex polygons.Comment: 14 pages, 5 figure
An Optimal Algorithm for the Separating Common Tangents of two Polygons
We describe an algorithm for computing the separating common tangents of two
simple polygons using linear time and only constant workspace. A tangent of a
polygon is a line touching the polygon such that all of the polygon lies to the
same side of the line. A separating common tangent of two polygons is a tangent
of both polygons where the polygons are lying on different sides of the
tangent. Each polygon is given as a read-only array of its corners. If a
separating common tangent does not exist, the algorithm reports that.
Otherwise, two corners defining a separating common tangent are returned. The
algorithm is simple and implies an optimal algorithm for deciding if the convex
hulls of two polygons are disjoint or not. This was not known to be possible in
linear time and constant workspace prior to this paper.
An outer common tangent is a tangent of both polygons where the polygons are
on the same side of the tangent. In the case where the convex hulls of the
polygons are disjoint, we give an algorithm for computing the outer common
tangents in linear time using constant workspace.Comment: 12 pages, 6 figures. A preliminary version of this paper appeared at
SoCG 201
Asymptotic Behavior of Inflated Lattice Polygons
We study the inflated phase of two dimensional lattice polygons with fixed
perimeter and variable area, associating a weight to a
polygon with area and bends. For convex and column-convex polygons, we
show that , where , and . The
constant is found to be the same for both types of polygons. We argue
that self-avoiding polygons should exhibit the same asymptotic behavior. For
self-avoiding polygons, our predictions are in good agreement with exact
enumeration data for J=0 and Monte Carlo simulations for . We also
study polygons where self-intersections are allowed, verifying numerically that
the asymptotic behavior described above continues to hold.Comment: 7 page
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