Kensuke Tamura

The differences in performance among binary-integer encodings in an Ising machine, which can solve combinatorial optimization problems, are investigated. Many combinatorial optimization problems can be mapped to find the lowest-energy (ground) state of an Ising model or its equivalent model, the Quadratic Unconstrained Binary Optimization (QUBO). Since the Ising model and QUBO consist of binary variables, they often express integers as binary when using Ising machines. A typical example is the c

We present rigorous results for the $\mathrm{SU}(n)$ Fermi-Hubbard model on the railroad-trestle lattice. We first study the model with a flat band at the bottom of the single-particle spectrum and prove that the ground states exhibit $\mathrm{SU}(n)$ ferromagnetism when the total fermion number is the same as the number of unit cells. We then perturb the model by adding extra hopping terms and make the flat band dispersive. Under the same filling condition, it is proved that the ground states o

We introduce a class of spinless fermion models that exhibit quantum many-body scars (QMBS) originating from kinetic constraints in the form of density-assisted hopping. The models can be defined on any lattice in any dimension and allow for spatially varying interactions. We construct a tower of exact eigenstates with finite energy density, and we demonstrate that these QMBS are responsible for the nonthermal nature of the system by studying the entanglement entropy and correlation functions. T

Several lines of evidence suggest that the aggregation and deposition of amyloid-β peptide (Aβ) initiate the pathology of Alzheimer's disease (AD). Recently, a genome-wide association study demonstrated that a single-nucleotide polymorphism proximal to the EPHA4 gene, which encodes a receptor tyrosine kinase, is associated with AD risk. However, the molecular mechanism of EphA4 in the pathogenesis of AD, particularly in Aβ production, remains unknown. Here, we performed several pharmacological a

We are developing low noise analog ASICs for hard X-ray and gamma-ray astronomy. They are based on a sub-micron CMOS process. Our design includes a finely-adjustable high-resistance circuit, which, for example, enables us to realize a pole-zero-cancellation in the analog chain. A two-dimensional ASIC with a fast read-out scheme and a one-dimensional ASIC with an improved analog design are developed and verified. With the latter ASIC connected with a CdTe detector, we have obtained a radioactive

In this paper, the optimal repairing model is presented to design the reparing rules for road pavement that can minimize the expected life cycle costs under uncertainty. Taking the idivisability of repairing rules into account, the Monte Calro simulation methodology is presented to find out the optimal rules in an efficient manner. The applicability of the model is investigated by case studies.

We are developing analog ASICs for Cadmium Telluride (CdTe) pixel and line sensors for high energy astrophysics and other applications. In the ASIC development, we are cooperating with other application users to build up a library of "tried-and-true" circuit modules tuned for several processes ("Open IP project"). As an initial trial, a 2-dimensional ASIC with a pixel size of 260 /spl mu/m /spl times/ 260 /spl mu/m and a 1-dimensional ASIC with an improved analog circuit, both based on 0.35-/spl

Abstract We develop a general theory of flat-band ferromagnetism in the SU( N ) Fermi–Hubbard model, which describes the behavior of N -component fermions with SU( N ) symmetric interactions. We focus on the case where the single-particle spectrum has a flat band at the bottom and establish a necessary and sufficient condition for the SU( N ) Hubbard model to exhibit ferromagnetism when the number of particles is the same as the degeneracy. We show that the occurrence of ferromagnetism is equiva

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

We present rigorous results for the SU($n$) Fermi-Hubbard model on the railroad-trestle lattice. We first study the model with a flat band at the bottom of the single-particle spectrum and prove that the ground states exhibit SU($n$) ferromagnetism when the total fermion number is the same as the number of unit cells. We then perturb the model by adding extra hopping terms and make the flat band dispersive. Under the same filling condition, it is proved that the ground states of the perturbed mo

We develop a general theory of flat-band ferromagnetism in the SU($N$) Fermi-Hubbard model, which describes the behavior of $N$-component fermions with SU($N$) symmetric interactions. We focus on the case where the single-particle spectrum has a flat band and establish a necessary and sufficient condition for the SU($N$) Hubbard model to exhibit ferromagnetism when the number of particles is the same as the degeneracy. We show that the occurrence of ferromagnetism is equivalent to the irreducibi

In this paper, a system methodology is presented to manage road pavement under budget constraints considering uncertainty around pavement deterioration. In doing so, the optimal repairing rules for individual road segments are formulated to minimize life cycle costs comprising user and repairing costs. And, the cost-benefit rules to find out the repairing orders, which can reduce the life cycle costs as much as possible, are presented. The applicability of the methodology presented in the paper