Self-localized modes in a quantum vibronic system, with long range interaction of Kac-Baker type and interacting nonlinearly with an acoustical phonon bath, is studied. One works in the coherent state approximation. Following a procedure of Sarker and Krumhansl the problem is reduced to a nearest neighbours one. In the continuum limit the localized state satisfy a mKdV equation. An approximate ...

The extended Hubbard Hamiltonian on a bcc lattice is studied at half-filling and for a finite hopping between next-nearest-neighbours, in mean-field approximation. An ionic insulating broken-symmetry phase is predicted for any hydrogenoid bcc solid in the density range 1.0 < r s < 2.6. The occurrence of an ionic phase would explain the failure to achieve hydrogen metallization at high pressures...

This paper presents a working combination of input selection strategy and a fast approximator for time series prediction. The input selection is performed using Tabu Search with the Delta Test. The approximation methodology is called Optimally-Pruned k -Nearest Neighbors (OP-KNN), which has been recently developed for fast and accurate regression and classification tasks. In this paper we demon...

We give a new “nested adds” circuit for implementing Shor’s algorithm in linear width and quadratic depth on a nearest-neighbor machine. Our circuit combines Draper’s transform adder with approximation ideas of Zalka. The transform adder requires small controlled rotations. We also give another version, with slightly larger depth, using only reversible classical gates. We do not know which vers...

H = S v i S v i + 1 ) y y corresponds to what is called the XY chain. The hexagonal compound PrCl3 provides a good approximation to the 1-D XY chain. The structure of PrCl3 is illustrated in Figure 1. Nearest neighbor Pr ions form chains along the hexagonal axis. Each Pr ion has nine close Cl neighbors which form three equilateral triangles; one triangle lies in the plane perpendicular to the h...

The coupling between two magnetic centers in a band is discussed within the framework of the functional-integral scheme. The model used is the single-orbital Hubbard model with Coulomb repulsion only on the two magnetic sites. In lowest approximation, antiferromagnetic Ising coupling is obtained when the moments are nearest neighbors. When the moments are far apart, Ruderman-Kittel-Kasuya-Yosid...

We study a two-sublattice Ising metamagnet with nearest and next-nearestneighbor interactions, in both uniform and random fields. Using a mean-field approximation, we show that the qualitative features of the phase diagrams are significantly dependent on the distribution of the random fields. In particular, for a Gaussian distribution of random fields, the behavior of the model is qualitatively...

We present a Monte Carlo algorithm for learning to act in partially observable Markov decision processes (POMDPs) with real-valued state and action spaces. Our approach uses importance sampling for representing beliefs, and Monte Carlo approximation for belief propagation. A reinforcement learning algorithm, value iteration, is employed to learn value functions over belief states. Finally, a sa...

We consider the d-dimensional Ising model with a nearest neighbor ferromagnetic interaction J(d) = l/4d. We show that as d -» oo the -f phase (and the phase) approaches a product measure with density given by the mean field approximation. In particular the spontaneous magnetization converges to its mean field value. A similar result holds for the unique Gibbs measure of the system subject to an...