22,910 research outputs found
The Apparent Fractal Conjecture
This short communication advances the hypothesis that the observed fractal
structure of large-scale distribution of galaxies is due to a geometrical
effect, which arises when observational quantities relevant for the
characterization of a cosmological fractal structure are calculated along the
past light cone. If this hypothesis proves, even partially, correct, most, if
not all, objections raised against fractals in cosmology may be solved. For
instance, under this view the standard cosmology has zero average density, as
predicted by an infinite fractal structure, with, at the same time, the
cosmological principle remaining valid. The theoretical results which suggest
this conjecture are reviewed, as well as possible ways of checking its
validity.Comment: 6 pages, LaTeX. Text unchanged. Two references corrected. Contributed
paper presented at the "South Africa Relativistic Cosmology Conference in
Honour of George F. R. Ellis 60th Birthday"; University of Cape Town,
February 1-5, 199
Single hole and vortex excitations in the doped Rokhsar-Kivelson quantum dimer model on the triangular lattice
We consider the doped Rokhsar-Kivelson quantum dimer model on the triangular
lattice with one mobile hole (monomer) at the Rokhsar-Kivelson point. The
motion of the hole is described by two branches of excitations: the hole may
either move with or without a trapped Z2 vortex (vison). We perform a study of
the hole dispersion in the limit where the hole hopping amplitude is much
smaller than the interdimer interaction. In this limit, the hole without vison
moves freely and has a tight-binding spectrum. On the other hand, the hole with
a trapped vison is strongly constrained due to interference effects and can
only move via higher-order virtual processes.Comment: 4 pages, 4 figures; minor changes, replaced by published versio
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