2,104 research outputs found
Higher Spins and Matter Interacting in Dimension Three
The spectrum of Prokushkin--Vasiliev Theory is puzzling in light of the
Gaberdiel--Gopakumar conjecture because it generically contains an additional
sector besides higher-spin gauge and scalar fields. We find the unique
truncation of the theory avoiding this problem to order 2 in perturbations
around AdS. The second-order backreaction on the physical gauge sector
induced by the scalars is computed explicitly. The cubic action for the
physical fields is determined completely. We comment on a different higher-spin
theory without such additional fields at .Comment: 55 pages + appendices, LaTex. Final version to appear in JHE
A Random Multifractal Tilling
We develop a multifractal random tilling that fills the square. The
multifractal is formed by an arrangement of rectangular blocks of different
sizes, areas and number of neighbors. The overall feature of the tilling is an
heterogeneous and anisotropic random self-affine object. The multifractal is
constructed by an algorithm that makes successive sections of the square. At
each -step there is a random choice of a parameter related to the
section ratio. For the case of random choice between and we
find analytically the full spectrum of fractal dimensions
Anisotropy and percolation threshold in a multifractal support
Recently a multifractal object, , was proposed to study percolation
properties in a multifractal support. The area and the number of neighbors of
the blocks of show a non-trivial behavior. The value of the
probability of occupation at the percolation threshold, , is a function
of , a parameter of which is related to its anisotropy. We
investigate the relation between and the average number of neighbors of
the blocks as well as the anisotropy of
Magnetic particles confined in a modulated channel: structural transitions tunable by tilting a magnetic field
The ground state of colloidal magnetic particles in a modulated channel are
investigated as function of the tilt angle of an applied magnetic field. The
particles are confined by a parabolic potential in the transversal direction
while in the axial direction a periodic substrate potential is present. By
using Monte Carlo (MC) simulations, we construct a phase diagram for the
different crystal structures as a function of the magnetic field orientation,
strength of the modulated potential and the commensurability factor of the
system. Interestingly, we found first and second order phase transitions
between different crystal structures, which can be manipulated by the
orientation of the external magnetic field. A re-entrant behavior is found
between two- and four-chain configurations, with continuous second order
transitions. Novel configurations are found consisting of frozen in solitons.
By changing the orientation and/or strength of the magnetic field and/or the
strength and the spatial frequency of the periodic substrate potential, the
system transits through different phases.Comment: Submitted to Phys. Rev. E (10 pages, 12 figures
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