Roles of energy dissipation in a liquid-solid transition of out-of-equilibrium systems

Self-organization of active matter as well as driven granular matter in non-equilibrium dynamical states has attracted considerable attention not only from the fundamental and application viewpoints but also as a model to understand the occurrence of such phenomena in nature. These systems share common features originating from their intrinsically out-of-equilibrium nature. It remains elusive how energy dissipation affects the state selection in such non-equilibrium states. As a simple model system, we consider a non-equilibrium stationary state maintained by continuous energy input, relevant to industrial processing of granular materials by vibration and/or flow. More specifically, we experimentally study roles of dissipation in self-organization of a driven granular particle monolayer. We find that the introduction of strong inelasticity entirely changes the nature of the liquid-solid transition from two-step (nearly) continuous transitions (liquid-hexatic-solid) to a strongly discontinuous first-order-like one (liquid-solid), where the two phases with different effective temperatures can coexist, unlike thermal systems, under a balance between energy input and dissipation. Our finding indicates a pivotal role of energy dissipation and suggests a novel principle in the self-organization of systems far from equilibrium. A similar principle may apply to active matter, which is another important class of out-of-equilibrium systems. On noting that interaction forces in active matter, and particularly in living systems, are often non-conservative and dissipative, our finding may also shed new light on the state selection in these systems.Comment: 17 pages, 11 figure

22-knots with the same knot group but different knot quandles

We give a first example of 2-knots with the same knot group but different knot quandles by analyzing the knot quandles of twist spins. As a byproduct of the analysis, we also give a classification of all twist spins with finite knot quandles.Comment: 11 page

Microscopic mechanism of ultrashort-pulse laser ablation of metals: a molecular dynamics study incorporating electronic entropy effects

The microscopic mechanism of metal ablation induced by ultrashort laser pulse irradiation is investigated. A two-temperature model scheme combined with molecular dynamics (TTM-MD) is developed to incorporate electronic entropy effects into the simulation of metal ablation while satisfying the energy conservation law. Simulation with the TTM-MD scheme reveals that ultrashort laser pulse irradiation near the ablation threshold causes high-energy ion emission and sub-nanometer depth ablation, as observed experimentally, due to the electronic entropy effect. It is also shown that the electronic entropy effect is also significant in spallation.Comment: 13 pages, 18 figure

Integrable discretizations of the SIR model

Structure-preserving discretizations of the SIR model are presented by focusing on the hodograph transformation and the conditions for integrability for their discrete SIR models are given. For those integrable discrete SIR models, we derive their exact solutions as well as conserved quantities. If we choose the parameter appropriately for one of our proposed discrete SIR models, it conserves the conserved quantities of the SIR model. We also investigate an ultradiscretizable discrete SIR model.Comment: 31 pages, 8 figure

Global warming trend without the contributions from decadal variability of the Arctic Oscillation

AbstractClimate change associated with recent global warming is most prominent in the Arctic and subarctic. The Arctic Oscillation (AO) is a dominant atmospheric phenomenon in the Northern Hemisphere. Decadal variability of surface air temperature (SAT) associated with the AO index shows high correlation with recent global warming trend. In this study, the SAT variability in the Northern Hemisphere is separated in contributions from decadal variability by the AO and remaining components.The results indicate that the decadal variability of the AO index shows high correlation with the SAT variation until 1990. The AO index and SAT variabilities show a negative trend during 1949–1969, while the trend is positive during 1969–1989. In addition, the spatial distribution pattern of the SAT linear trend during each period shows the same pattern as AO. However, while the AO index indicates a negative trend, the SAT trend is continuously positive also after 1990. This warming pattern appearing after 1990 is caused by the Arctic amplification.Although the AO has a large amplitude on local scale, the AO is almost dynamically orthogonal to the hemispheric warming component. However, the AO can be related to the decadal variability of the Arctic and subarctic temperature change through the feedbacks by climate sub-systems

The total absolute curvature of closed curves with singularities

In this paper, we give a generalization of Fenchel's theorem for closed curves as frontals in Euclidean space $\mathbb{R}^n$. We prove that, for a non-co-orientable closed frontal in $\mathbb{R}^n$, its total absolute curvature is greater than or equal to $\pi$. It is equal to $\pi$ if and only if the curve is a planar locally $L$-convex closed frontal whose rotation index is $1/2$ or $-1/2$. Furthermore, if the equality holds and if every singular point is a cusp, then the number $N$ of cusps is an odd integer greater than or equal to $3$, and $N=3$ holds if and only if the curve is simple.Comment: 13 pages, 25 figure

Measurement of the residual stress in CrN coatings deposited on an Al alloy substrate

Chromium nitride (CrN) coatings were deposited on Al alloy substrates using the arc ion plating method with different bias voltages and different thicknesses. The residual stresses of these samples were measured via x-ray diffraction using the sin2 ψ method because the CrN crystals in the coatings were nonoriented. The stress gradient across the CrN coating was calculated from the curved 2θ-sin2 ψ diagram. In the case of CrN coatings deposited at low bias voltage, the compressive residual stress that formed at the substrate interface was larger than the stress at the surface of the CrN coating. Conversely, in the case of CrN coatings deposited at high bias voltage, the compressive residual stress on the surface of the CrN coating was larger than the stress on the interface with the substrate. In CrN coatings deposited at high bias voltage, very large compressive residual stress on the CrN coating surface decreased with increasing coating thickness