238 research outputs found
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
Quivers, Tilings, Branes and Rhombi
We describe a simple algorithm that computes the recently discovered brane
tilings for a given generic toric singular Calabi-Yau threefold. This therefore
gives AdS/CFT dual quiver gauge theories for D3-branes probing the given
non-compact manifold. The algorithm solves a longstanding problem by computing
superpotentials for these theories directly from the toric diagram of the
singularity. We study the parameter space of a-maximization; this study is made
possible by identifying the R-charges of bifundamental fields as angles in the
brane tiling. We also study Seiberg duality from a new perspective.Comment: 36 pages, 40 figures, JHEP
TESELA: a new Virtual Observatory tool to determine blank fields for astronomical observations
The observation of blank fields, regions of the sky devoid of stars down to a
given threshold magnitude, constitutes one of the typical important calibration
procedures required for the proper reduction of astronomical data obtained in
imaging mode. This work describes a method, based on the use of the Delaunay
triangulation on the surface of a sphere, that allows the easy generation of
blank fields catalogues. In addition to that, a new tool named TESELA,
accessible through the WEB, has been created to facilitate the user to
retrieve, and visualise using the VO-tool Aladin, the blank fields available
near a given position in the sky.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society. 11 pages, 10 figures. Related Web tool accessible at
http://sdc.cab.inta-csic.es/tesel
Two triangulations methods based on edge refinement
In this paper two curvature adaptive methods of surface triangulation
are presented. Both methods are based on edge refinement to obtain a
triangulation compatible with the curvature requirements. The first
method applies an incremental and constrained Delaunay triangulation
and uses curvature bounds to determine if an edge of the triangulation
is admissible. The second method uses this function also in the edge
refinement process, i.e. in the computation of the location of a
refining point, and in the re-triangulation needed after the insertion
of this refining point. Results are presented, comparing both
approachesPostprint (published version
The local maxima of maximal injectivity radius among hyperbolic surfaces
The function on the Teichmueller space of complete, orientable, finite-area
hyperbolic surfaces of a fixed topological type that assigns to a hyperbolic
surface its maximal injectivity radius has no local maxima that are not global
maxima.Comment: Dramatically shortened (now 12 pp.), and introductory material
simplified, following a referee's suggestion
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