Evaluation of Dynamical Spectra for Zero-temperature Quantum Monte Carlo Simulations: Hubbard Lat- Tices and Continuous Systems

Dynamical spectra for Hubbard lattices and simple atoms are obtained using ground state projection (zero-temperature) quantum Monte Carlo and the maximum entropy method. For Hubbard lattices we show that results are equivalent to those obtained from maximum entropy deconvolutions of low-temperature grand canonical quantum Monte Carlo data. These calculations are resolution limited and fail to produce the discrete structure of the bound excited states of hydrogen, although integrated moments of the spectrum are accurate. However, low-energy structures from ab initio calculations can be incorporated into the maximum entropy default model to improve the accuracy of this method. 1. Quantum Monte Carlo, the maximum entropy method, and dy-namical spectral Quantum Monte Carlo (QMC) algorithms have been developed for a variety of systems and models, including the electron gas model, atoms and molecules, the Heisenberg spin model, Anderson impurity models, and Hubbard lattice models. To within statistical precision QMC calculations directly provide equal-time and static (! = 0) quantities, such as energy, compressibility, equal-time correlations, and static susceptibilities. Dynamical quantities (! 6 = 0) are not calculated directly in QMC, but it has always been considered desirable to obtain spectral features in order to interpret electrical resistivity measurements, neutron scattering, photoemission, and other dynamical probes. Substantial progress has been made in developing an algorithm for obtaining dynamical