arXiv subjects

Kazuya Murakami

Publications and source records attributed to Kazuya Murakami.

4 recordsLinked to original sources

arXiv2026

Non-Abelian $A_4$ vortices in $SO(3)$ gauge theory and non-invertible symmetries

We construct finite-tension non-Abelian vortex solutions in a renormalizable $(3+1)$-dimensional $SO(3)$ gauge theory Higgsed to the tetrahedral group $A_4$ by a Higgs field in the spin-3 representation. Since the vacuum manifold is $SO(3)/A_4$, the vortices are characterized by the non-Abelian fundamental group $π_1(SO(3)/A_4)\simeq \widetilde{A}_4$, the binary tetrahedral group. We obtain explicit axisymmetric vortex solutions carrying holonomies corresponding to the order-two and order-three conjugacy classes of $A_4$, determine their tensions numerically, and show that they exhibit type-I, type-II, and Bogomol'nyi--Prasad--Sommerfield-like behavior depending on the Higgs and gauge boson mass ratios. The vortices are classified by conjugacy classes of $\widetilde{A}_4$, while their infrared descriptions are labeled by conjugacy classes of $A_4$. We further demonstrate that the smooth finite-tension vortices reduce in the infrared to Gukov--Witten surface operators of the $A_4$ discrete gauge theory, thereby establishing a finite-energy ultraviolet completion of non-invertible defects in a renormalizable gauge-Higgs theory.

hep-th↗

arXiv2026

Instant and Reversible Adhesive-free Bonding Between Silicones and Glossy Papers for Soft Robotics

Integrating silicone with non-extensible materials is a common strategy used in the fabrication of fluidically-driven soft actuators, yet conventional approaches often rely on irreversible adhesives or embedding processes that are labor-intensive and difficult to modify. This work presents silicone-glossy paper bonding (SGB), a rapid, adhesive-free, and solvent-reversible bonding approach that forms robust silicone-paper interfaces simply through contact. The SGB interface withstands high mechanical loads (shear strength > 61 kPa) and can be fully detached and reassembled via ethanol immersion without loss of performance, enabling component reuse and rapid redesign. Characterization studies indicate that surface functional groups primarily govern adhesion on the glossy paper and the modulus of the silicone, while durability and environmental response clarify the conditions for reversible debonding. The results further suggest a synergistic interaction of hydrogen bonding and oligomer diffusion, yielding strong yet reconfigurable adhesion. Soft actuators fabricated using SGB design exhibit equal or greater performance compared to conventional embedded-layer design and enable programmable actuation modes, including contraction, bending, and twisting. By simplifying fabrication while supporting reuse and rapid iteration, SGB offers a scalable and sustainable platform for rapid prototyping in soft robotics.

cs.RO↗

arXiv2024

Plant Robots: Harnessing Growth Actuation of Plants for Locomotion and Object Manipulation

Plants display physical displacements during their growth due to photosynthesis, which converts light into chemical energy. This can be interpreted as plants acting as actuators with a built-in power source. This paper presents a method to create plant robots that move and perform tasks by harnessing the actuation output of plants: displacement and force generated from the growing process. As the target plant, radish sprouts are employed, and their displacement and force are characterized, followed by the calculation of power and energy densities. Based on the characterization, two different plant robots are designed and fabricated: a rotational robot and a gripper. The former demonstrates ground locomotion, achieving a travel distance of 14.6 mm with an average speed of 0.8 mm/h. The latter demonstrates the picking and placing of an object with a 0.1-g mass by the light-controlled open-close motion of plant fingers. A good agreement between the experimental and model values is observed in the specific data of the mobile robot, suggesting that obtaining the actuation characteristics of plants can enable the design and prediction of behavior in plant robots. These results pave the way for the realization of novel types of environmentally friendly and sustainable robots.

cs.RO↗

arXiv2021

Predicting Complex Non-spherical Instability Shapes of Inertial Cavitation Bubbles in Viscoelastic Soft Matter

Inertial cavitation in soft matter is an important phenomenon featured in a wide array of biological and engineering processes. Recent advances in experimental, theoretical, and numerical techniques have provided access into a world full of nonlinear physics, yet most of our quantitative understanding to date has been centered on a spherically symmetric description of the cavitation process. However, cavitation bubble growth and collapse rarely occur in a perfectly symmetrical fashion, particularly in soft materials. Predicting the onset of dynamically arising, non-spherical instabilities has remained a significant, unresolved challenge in part due to the additional constitutive complexities introduced by the surrounding nonlinear viscoelastic solid. Here, we provide a new theoretical model capable of accurately predicting the onset of non-spherical instability shapes of a bubble in a soft material by explicitly accounting for all pertinent nonlinear interactions between the fluid-like cavitation bubble and the solid-like surroundings. Comparison against high-resolution experimental images from laser-induced cavitation events in a polyacrylamide (PA) hydrogel show excellent agreement. Interestingly, and consistent with experimental findings, our model predicts the emergence of various dynamic instability shapes for hoop stretch ratios greater than one in contrast to most quasi-static investigations. Our new theoretical framework not only provides unprecedented insight into the cavitation dynamics in a soft solid, but it also provides a quantitative means of interpreting bubble dynamics relevant to a wide array of engineering and medical applications as well as natural phenomena.

cond-mat.soft↗