Ryota Suzuki

Pvclust: an R package for assessing the uncertainty in hierarchical clustering

SUMMARY Pvclust is an add-on package for a statistical software R to assess the uncertainty in hierarchical cluster analysis. Pvclust can be used easily for general statistical problems, such as DNA microarray analysis, to perform the bootstrap analysis of clustering, which has been popular in phylogenetic analysis. Pvclust calculates probability values (p-values) for each cluster using bootstrap resampling techniques. Two types of p-values are available: approximately unbiased (AU) p-value and bootstrap probability (BP) value. Multiscale bootstrap resampling is used for the calculation of AU p-value, which has superiority in bias over BP value calculated by the ordinary bootstrap resampling. In addition the computation time can be enormously decreased with parallel computing option.

Supersolid states in a hard-core Bose-Hubbard model on a layered triangular lattice

We study the ground-state properties in a hard-core Bose–Hubbard model on a layered triangular lattice. With the combined use of the cluster mean-field theory and the density matrix renormalization group method, we discuss the effect of interlayer coupling on supersolid states realized in a single-layered model. By examining the distributions for the particle density and superfluid order parameter, a rich phase diagram of the system is obtained. We find that supersolid states are widely stabilized at commensurate filling, in contrast to those in the case of the single-layered model. The nature of supersolid states is also addressed.

Cluster mean-field approach with density matrix renormalization group: Application to the hard-core bosonic Hubbard model on a triangular lattice

We introduce a new numerical method for the solution of self-consistent equations in the cluster mean-field theory. The method uses the density matrix renorm alization group method to solve the associated cluster problem. We obtain an accurate critical value of the supersolid-superfluid transitions in the hard-core bosonic Hubbard model on a triangular lattice, which is comparable with the recent quantum Monte Carlo results. This algorithm is applicable to more general classes of models with a larger number of degrees of freedom.