2,966 research outputs found
Some families of increasing planar maps
Stack-triangulations appear as natural objects when one wants to define some
increasing families of triangulations by successive additions of faces. We
investigate the asymptotic behavior of rooted stack-triangulations with
faces under two different distributions. We show that the uniform distribution
on this set of maps converges, for a topology of local convergence, to a
distribution on the set of infinite maps. In the other hand, we show that
rescaled by , they converge for the Gromov-Hausdorff topology on
metric spaces to the continuum random tree introduced by Aldous. Under a
distribution induced by a natural random construction, the distance between
random points rescaled by converge to 1 in probability.
We obtain similar asymptotic results for a family of increasing
quadrangulations
Representations of stack triangulations in the plane
Stack triangulations appear as natural objects when defining an increasing
family of triangulations by successive additions of vertices. We consider two
different probability distributions for such objects. We represent, or "draw"
these random stack triangulations in the plane and study the asymptotic
properties of these drawings, viewed as random compact metric spaces. We also
look at the occupation measure of the vertices, and show that for these two
distributions it converges to some random limit measure.Comment: 29 pages, 13 figure
Planar maps, circle patterns and 2d gravity
Via circle pattern techniques, random planar triangulations (with angle
variables) are mapped onto Delaunay triangulations in the complex plane. The
uniform measure on triangulations is mapped onto a conformally invariant
spatial point process. We show that this measure can be expressed as: (1) a sum
over 3-spanning-trees partitions of the edges of the Delaunay triangulations;
(2) the volume form of a K\"ahler metric over the space of Delaunay
triangulations, whose prepotential has a simple formulation in term of ideal
tessellations of the 3d hyperbolic space; (3) a discretized version (involving
finite difference complex derivative operators) of Polyakov's conformal
Fadeev-Popov determinant in 2d gravity; (4) a combination of Chern classes,
thus also establishing a link with topological 2d gravity.Comment: Misprints corrected and a couple of footnotes added. 42 pages, 17
figure
The Ising model on the random planar causal triangulation: bounds on the critical line and magnetization properties
We investigate a Gibbs (annealed) probability measure defined on Ising spin
configurations on causal triangulations of the plane. We study the region where
such measure can be defined and provide bounds on the boundary of this region
(critical line). We prove that for any finite random triangulation the
magnetization of the central spin is sensitive of the boundary conditions.
Furthermore, we show that in the infinite volume limit, the magnetization of
the central spin vanishes for values of the temperature high enough.Comment: 28 pages, 2 figures, 1 section adde
On the spectral dimension of causal triangulations
We introduce an ensemble of infinite causal triangulations, called the
uniform infinite causal triangulation, and show that it is equivalent to an
ensemble of infinite trees, the uniform infinite planar tree. It is proved that
in both cases the Hausdorff dimension almost surely equals 2. The infinite
causal triangulations are shown to be almost surely recurrent or, equivalently,
their spectral dimension is almost surely less than or equal to 2. We also
establish that for certain reduced versions of the infinite causal
triangulations the spectral dimension equals 2 both for the ensemble average
and almost surely. The triangulation ensemble we consider is equivalent to the
causal dynamical triangulation model of two-dimensional quantum gravity and
therefore our results apply to that model.Comment: 22 pages, 6 figures; typos fixed, one extra figure, references
update
Random non-crossing plane configurations: A conditioned Galton-Watson tree approach
We study various models of random non-crossing configurations consisting of
diagonals of convex polygons, and focus in particular on uniform dissections
and non-crossing trees. For both these models, we prove convergence in
distribution towards Aldous' Brownian triangulation of the disk. In the case of
dissections, we also refine the study of the maximal vertex degree and validate
a conjecture of Bernasconi, Panagiotou and Steger. Our main tool is the use of
an underlying Galton-Watson tree structure.Comment: 24 pages, 9 figure
The skeleton of the UIPT, seen from infinity
We prove that geodesic rays in the Uniform Infinite Planar Triangulation
(UIPT) coalesce in a strong sense using the skeleton decomposition of random
triangulations discovered by Krikun. This implies the existence of a unique
horofunction measuring distances from infinity in the UIPT. We then use this
horofunction to define the skeleton "seen from infinity" of the UIPT and relate
it to a simple Galton--Watson tree conditioned to survive, giving a new and
particularly simple construction of the UIPT. Scaling limits of perimeters and
volumes of horohulls within this new decomposition are also derived, as well as
a new proof of the -point function formula for random triangulations in the
scaling limit due to Ambj{\o}rn and Watabiki.Comment: 34 pages, 14 figure
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