Monte Carlo simulations of two-dimensional charged bosons

Quantum Monte Carlo methods are used to calculate various ground state properties of charged bosons in two dimensions, throughout the whole density range where the fluid phase is stable. Wigner crystallization is predicted at $r_s\simeq 60$. Results for the ground state energy and the momentum distribution are summarized in analytic interpolation formulas embodying known asymptotic behaviors. Near freezing, the condensate fraction is less than 1%. The static structure factor $S(k)$ and susceptibility $\chi(k)$ are obtained from the density-density correlation function in imaginary time, $F({\bf k},\tau)$. An estimate of the energy of elementary excitations, given in terms of an upper bound involving $S(k)$ and $\chi(k)$, is compared with the result obtained via analytic continuation from $F({\bf k},\tau)$.