Universal Jump in the Helicity Modulus of the Two-Dimensional Quantum XY Model

The helicity modulus of the S=1/2 XY model is precisely estimated through a world line quantum Monte Carlo method enhanced by a cluster update algorithm. The obtained estimates for various system sizes and temperatures are well fitted by a scaling form with L replaced by \log(L/L_0), which is inferred from the solution of the Kosterlitz renormalization group equation. The validity of the Kosterlitz-Thouless theory for this model is confirmed.Comment: 4 pages, 3 figure

Variations on the Supersymmetric Q6 Model of Flavor

We observe that a recently proposed supersymmetric model with Q6 flavor symmetry admits a new CP violating ground state. A new sum rule for the quark mixing parameters emerges, which is found to be consistent with data. Simple extensions of the model to the neutrino sector suggest an inverted hierarchical mass spectrum with nearly maximal CP violation (|delta_{MNS}| simeq pi/2). Besides reducing the number of parameters in the fermion sector, these models also provide solutions to the SUSY flavor problem and the SUSY CP problem. We construct a renormalizable scalar potential that leads to the spontaneous breaking of CP symmetry and the family symmetry.Comment: 22 pages, 7 figure

SU(N) Heisenberg model with multi-column representations

The $\mathrm{SU}(N)$ symmetric antiferromagnetic Heisenberg model with multi-column representations on the two-dimensional square lattice is investigated by quantum Monte Carlo simulations. For the representation of Young diagram with two columns, we confirm that a valence-bond solid order appears as soon as the N\'eel order disappears at $N = 10$ indicating no intermediate phase. In the case of the representation with three columns, there is no evidence for both of the N\'eel and the valence-bond solid ordering for $N\ge 15$. This is actually consistent with the large-$N$ theory, which predicts that the VBS state immediately follows the N\'eel state, because the expected spontaneous order is too weak to be detected.Comment: 5 pages, 5 figure

Entropy Governed by the Absorbing State of Directed Percolation

We investigate the informational aspect of (1+1)-dimensional directed percolation, a canonical model of a nonequilibrium continuous transition to a phase dominated by a single special state called the "absorbing" state. Using a tensor network scheme, we numerically calculate the time evolution of state probability distribution of directed percolation. We find a universal relaxation of Renyi entropy at the absorbing phase transition point as well as a new singularity in the active phase, slightly but distinctly away from the absorbing transition point. At the new singular point, the second-order Renyi entropy has a clear cusp. There we also detect a singular behavior of "entanglement entropy," defined by regarding the probability distribution as a wave function. The entanglement entropy vanishes below the singular point and stays finite above. We confirm that the absorbing state, though its occurrence is exponentially rare in the active phase, is responsible for these phenomena. This interpretation provides us with a unified understanding of time evolution of the Renyi entropy at the critical point as well as in the active phase.Comment: 8(=4+4)pages, 13(=5+6) figure

COMPUTATION OF AN UNSTEADY ORIFICE FLOW IN A CIRCULAR PIPE FROM WALL PRESSURE MEASUREMENTS BASED ON MEASUREMENT-INTEGRATED SIMULATION USING A TURBULENT MODEL

ABSTRACT Visualizing the state of real turbulent flow is important in many applications such as safe operation and fault diagnosis in plant or pipeline. Two approaches to this purpose exist: experimental measurement and numerical simulation. In experimental measurement, reliability of the result at measured point is easy to evaluate. However, information of the whole flow field is difficult to obtain. On the other hand, numerical simulation easily obtains any information of the flow field. However, the reliability of the result strongly depends on the numerical model and boundary condition and/or the initial condition. In general, the more precise results are needed, the heavier computation load we spend. None of these approaches is superior, and combination methods of them are subjected to extensive research. Above all, we particularly paid attention to measurement-integrated (MI) simulation proposed by Hayase et al. MI simulation can expect to reduce computational load. We have applied MI simulation to unsteady oscillatory airflows passing through an orifice. In our previous study, a standard k-ε model was used for MI simulation. Estimation error remained due to inadequate consideration of the feedback law. In our latest study, the feedback law was decided considering an effect of computation grid on CFD of contracted flow. As a result, wall pressures near the orifice plate and axial velocities on vena contracta estimated with MI simulation showed good agreement with that of measurement. In the present paper, we deal with visualization of unsteady oscillatory airflows passing through an orifice from wall pressure measurement based on MI simulation using a turbulent model. The former studies have used measured inlet flow rate which is unknown in many actual case. Compared with the flow rate measurement, wall pressure measurement is simple. Therefore, we consider MI simulation using only wall pressure are of practical use. The developed MI simulation was performed with unsteady flow rate with the frequency up to 10 Hz. Computation results obtained with the developed MI simulation using coarse computation grid is compared with experimental results. It is confirmed that flow field obtained with the developed MI simulation is close to that of experiment. INTRODUCTION Visualizing the state of real turbulent flow is important in many applications such as safe operation and fault diagnosis in plant or pipeline. The methods used to visualize the flow conditions can be classified into two approaches. One is experimental measurement, and the other is numerical simulation by solving several equations. Experimental measurement methods include the use of velocity and pressure sensors and visualization techniques such as particle image velocimetry and particle tracking velocimetry. Flow conditions can be accurately obtained at measured points by using sensors. However, sensors are not suitable for obtaining velocity profiles or pressure distributions. By contrast, visualization techniques are able to obtain these distributions. However, the available flow field is limited because particle behavior is tracked using a laser and a camera. In contrast, simulation can easily obtain a flow field. However, a long computation time is needed to obtain good results, especially under turbulent conditions. None of these approaches is superior, and combination methods of them are subjected to extensive research. We have focused on measurement-integrated (MI) simulation, which was first proposed by Hayase et al [1]. MI simulation is a kind of observer that employs a CFD scheme as the mathematical model for the relevant system. The block diagram i

Two Degree of Freedom Adaptive Control for Hysteresis Compensation of Pneumatic Continuum Bending Actuator

Soft robotics, with their inherent flexibility and infinite degrees of freedom (DoF), offer promising advancements in human-machine interfaces. Particularly, pneumatic artificial muscles (PAMs) and pneumatic bending actuators have been fundamental in driving this evolution, capitalizing on their mimetic nature to natural muscle movements. However, with the versatility of these actuators comes the intricate challenge of hysteresis - a nonlinear phenomenon that hampers precise positioning, especially pronounced in pneumatic actuators due to gas compressibility. In this study, we introduce a novel 2-DoF adaptive control for precise bending tracking using a pneumatic continuum actuator. Notably, our control method integrates adaptability into both the feedback and the feedforward element, enhancing trajectory tracking in the presence of profound nonlinear effects. Comparative analysis with existing approaches underscores the superior tracking accuracy of our proposed strategy. This work discusses a new way of simple yet effective control designs for soft actuators with hysteresis properties.Comment: Submitted to IEEE Conference on Robotics and Automation (ICRA 2024), Under Revie

Trajectory Tracking Control of Dual-PAM Soft Actuator with Hysteresis Compensator

Soft robotics is a swiftly evolving field. Pneumatic actuators are suitable for driving soft robots because of their superior performance. However, their control is challenging due to the hysteresis characteristics. In response to this challenge, we propose an adaptive control method to compensate for the hysteresis of soft actuators. Employing a novel dual pneumatic artificial muscle (PAM) bending actuator, the innovative control approach abates hysteresis effects by dynamically modulating gains within a traditional PID controller corresponding to the predicted variation of the reference trajectory. Through experimental evaluation, we found that the proposed control method outperforms its conventional counterparts regarding tracking accuracy and response speed. Our work reveals a new direction for advancing model-free control in soft actuators.Comment: This paper has been published in the IEEE Robotics and Automation Letters ,DOI 10.1109/LRA.2023.3334098, copyright has been transfferd to the IEEE. Final version is available at IEEE Xplor

Thermal phase transitions to valence-bond-solid phase in the two-dimensional generalized SU(N) Heisenberg models

International Conference on Strongly Correlated Electron Systems 2014 (SCES2014) 7–14 July 2014, Grenoble, France.We study thermal transitions of the generalized SU(N) Heisenberg models with four-body interactions on a square lattice and with six-body interactions on a honeycomb lattice. In both models for the N=3 and 4 cases, a singlet-dimer state is stabilized at a very low temperature, where a rotational symmetry of lattice is broken spontaneously. We discuss the universality class of thermal transition to the singlet dimer phases, performing quantum Monte Carlo calculations. From the finite-size scaling analysis, we find that the criticality for the square lattice case is well explained by the 2D weak Ising universality, while the 2D three-state Potts universality is observed in the honeycomb lattice case

How to evaluate science problem solving in a computerized learning environment? Construction of an analyzing scheme

Περιέχει το πλήρες κείμενοThis paper describes the construction of a ‘computerized science problem solving’ scheme, which enables analysis and evaluation of the effectiveness of science problem-solving by junior high-school students working in a computerized learning environment. The scheme was based on observations of 187 students as they solved qualitative science problems taken from a specific computerized learning environment. Students were also interviewed before and after the problem solving. The scheme is presented on two levels. The large-scale comprises 11 main categories, each sub-divided into sub-categories to yield the detailed-level. The sub-categories were based on a repertoire of activities found in the observation protocols, and were approved by external judgement and a validation process. The detailed-level scheme enables evaluation and statistical analysis of the participants' problem-solving effectiveness, providing substantial evidence for the construct validity of the scheme, and demonstrating its potential as a valid analyzing and evaluative tool for computerized science problem solving