3 research outputs found
Dynamically Triangulated Ising Spins in Flat Space
A model describing Ising spins with short range interactions moving randomly
in a plane is considered. In the presence of a hard core repulsion, which
prevents the Ising spins from overlapping, the model is analogous to a
dynamically triangulated Ising model with spins constrained to move on a flat
surface. It is found that as a function of coupling strength and hard core
repulsion the model exhibits multicritical behavior, with first and second
order transition lines terminating at a tricritical point. The thermal and
magnetic exponents computed at the tricritical point are consistent with the
exact two-matrix model solution of the random Ising model, introduced
previously to describe the effects of fluctuating geometries.Comment: (10 pages + 4 figures), CERN-Th-7577/9
Disorder Induced Phase Transition in a Random Quantum Antiferromagnet
A two-dimensional Heisenberg model with random antiferromagnetic
nearest-neighbor exchange is studied using quantum Monte Carlo techniques. As
the strength of the randomness is increased, the system undergoes a transition
from an antiferromagnetically ordered ground state to a gapless disordered
state. The finite-size scaling of the staggered structure factor and
susceptibility is consistent with a dynamic exponent .Comment: Revtex 3.0, 10 pages + 5 postscript figures available upon request,
UCSBTH-94-1