We study the equilibrium properties of the nearest-neighbor Ising
antiferromagnet on a triangular lattice in the presence of a staggered field
conjugate to one of the degenerate ground states. Using a mapping of the ground
states of the model without the staggered field to dimer coverings on the dual
lattice, we classify the ground states into sectors specified by the number of
``strings''. We show that the effect of the staggered field is to generate
long-range interactions between strings. In the limiting case of the
antiferromagnetic coupling constant J becoming infinitely large, we prove the
existence of a phase transition in this system and obtain a finite lower bound
for the transition temperature. For finite J, we study the equilibrium
properties of the system using Monte Carlo simulations with three different
dynamics. We find that in all the three cases, equilibration times for low
field values increase rapidly with system size at low temperatures. Due to this
difficulty in equilibrating sufficiently large systems at low temperatures, our
finite-size scaling analysis of the numerical results does not permit a
definite conclusion about the existence of a phase transition for finite values
of J. A surprising feature in the system is the fact that unlike usual glassy
systems, a zero-temperature quench almost always leads to the ground state,
while a slow cooling does not.Comment: 12 pages, 18 figures: To appear in Phys. Rev.
