Publications

A01-003 SANO

Paper | Original Paper

2018

*Taro P. Shimizu and Kazumasa A. Takeuchi,
Measuring Lyapunov exponents of large chaotic systems with global coupling by time series analysis,
Chaos 28, 121103/1-6 (2018).

[Summary] Despite the prominent importance of the Lyapunov exponents for characterizing chaos, it still remains a challenge to measure them for large experimental systems, mainly because of the lack of recurrences in time series analysis. Here we develop a method to overcome this difficulty, valid for highly symmetric systems such as systems with global coupling for which the dimensionality of recurrence analysis can be reduced drastically. We test our method numerically with two globally coupled systems, namely, logistic maps and limit-cycle oscillators with global coupling. The evaluated exponent values are successfully compared with the true ones obtained by the standard numerical method. We also describe a few techniques to improve the accuracy of the proposed method.

Zeying Che, Jan de Gier, Iori Hiki, *Tomohiro Sasamoto,
Exact confirmation of 1D nonlinear fluctuating hydrodynamics for a two-species exclusion process,
Physical Review Letters 120, 240601 (2018).

[Summary] We consider current statistics for a two species exclusion process of particles hopping in opposite directions on a one-dimensional lattice. We derive an exact formula for the Green’s function as well as for a joint current distribution of the model, and study its long time behavior. For a step type initial condition, we show that the limiting distribution is a product of the Gaussian and the GUE Tracy-Widom distribution. This is the first analytic confirmation for a multi-component system of a prediction from the recently proposed non-linear fluctuating hydrodynamics for one dimensional systems.

*Takahisa Fukadai and Tomohiro Sasamoto,
Transient Dynamics of Double Quantum Dots Coupled to Two Reservoirs,
Journal of the Physical Society of Japan 87, 054006/1-22 (2018).

[Summary] We study the time-dependent properties of double quantum dots coupled to two reservoirs using the nonequilibrium Green function method. For an arbitrary time-dependent bias, we derive an expression for the time-dependent electron density of a dot and several cur- rents, including the current between the dots in the wide-band-limit approximation. For the special case of a constant bias, we calculate the electron density and the currents numerically. As a result, we find that these quantities oscillate and that the number of crests in a single period of the current from a dot changes with the bias voltage. We also obtain an analytical expression for the relaxation time, which expresses how fast the system converges to its steady state. From the expression, we find that the relaxation time becomes constant when the coupling strength between the dots is sufficiently large in comparison with the difference of coupling strength between the dots and the reservoirs.

Yasufumi Ito and *Kazumasa A. Takeuchi,
When fast and slow interfaces grow together: connection to the half-space problem of the Kardar-Parisi-Zhang class,
Physical Review E 97, 040103(R)/1-6 (2018).

[Summary] We study height fluctuations of interfaces in the $(1+1)$-dimensional Kardar-Parisi-Zhang (KPZ) class, growing at different speeds in the left half and the right half of space. Carrying out simulations of the discrete polynuclear growth model with two different growth rates, combined with the standard setting for the droplet, flat, and stationary geometries, we find that the fluctuation properties at and near the boundary are described by the KPZ half-space problem developed in the theoretical literature. In particular, in the droplet case, the distribution at the boundary is given by the largest-eigenvalue distribution of random matrices in the Gaussian symplectic ensemble, often called the GSE Tracy-Widom distribution. We also characterize crossover from the full-space statistics to the half-space one, which arises when the difference between the two growth speeds is small.

*Takaki Yamamoto and Masaki Sano,
Theoretical model of chirality-induced helical self-propulsion,
Physical Review E 97, 012607/1-11 (2018).

[Summary] We recently reported the experimental realization of a chiral artificial microswimmer exhibiting helical selfpropulsion[T. Yamamoto and M. Sano, Soft Matter 13, 3328 (2017)]. In the experiment, cholesteric liquidcrystal (CLC) droplets dispersed in surfactant solutions swam spontaneously, driven by the Marangoni flow, inhelical paths whose handedness is determined by the chirality of the component molecules of CLC. To studythe mechanism of the emergence of the helical self-propelled motion, we propose a phenomenological modelof the self-propelled helical motion of the CLC droplets. Our model is constructed by symmetry argument inchiral systems, and it describes the dynamics of CLC droplets with coupled time-evolution equations in termsof a velocity, an angular velocity, and a tensor variable representing the symmetry of the helical director field ofthe droplet. We found that helical motions as well as other chiral motions appear in our model. By investigatingbifurcation behaviors between each chiral motion, we found that the chiral coupling terms between the velocityand the angular velocity, the structural anisotropy of the CLC droplet, and the nonlinearity of model equationsplay a crucial role in the emergence of the helical motion of the CLC droplet.

Daiki Nishiguchi, Junichiro Iwasawa, Hong-Ren Jiang and Masaki Sano,
Flagellar dynamics of chains of active Janus particles fueled by an AC electric field,
New Journal of Physics 20, 015002/1-14 (2018).

[Summary] We study the active dynamics of self-propelled asymmetrical colloidal particles(Janus particles) fueledby an AC electric field. Both the speed and direction of the self-propulsion, and the strength of theattractive interaction between particles can be controlled by tuning the frequency of the appliedelectric field and the ion concentration of the solution. The strong attractive force at high ionconcentration gives rise to chain formation of the Janus particles, which can be explained by thequadrupolar charge distribution on the particles. Chain formation is observed irrespective of thedirection of the self-propulsion of the particles. When both the position and the orientation ofthe heads of the chains are fixed, they exhibit beating behavior reminiscent of eukaryotic flagella. Thebeating frequency of the chains of Janus particles depends on the applied voltage and thus on the selfpropulsiveforce. The scaling relation between the beating frequency and the self-propulsive forcedeviates from theoretical predictions made previously on active filaments. However, this discrepancyis resolved by assuming that the attractive interaction between the particles is mediated by thequadrupolar distribution of the induced charges, which gives indirect but convincing evidence on themechanisms of the Janus particles. This signifies that the dependence between the propulsionmechanism and the interaction mechanism, which had been dismissed previously, can modify thedispersion relations of beating behaviors. In addition, hydrodynamic interaction within the chain, andits effect on propulsion speed, are discussed. These provide new insights into active filaments, such asoptimal flagellar design for biological functions.

2017

*Yohsuke T. Fukai and Kazumasa A. Takeuchi,
Kardar-Parisi-Zhang Interfaces with Inward Growth,
Physical Review Letters 119, 030602/1-5 (2017).

[Summary] We study the (1+1)-dimensional Kardar-Parisi-Zhang (KPZ) interfaces growing inward from ring-shaped initial conditions, experimentally and numerically, using growth of a turbulent state in liquid-crystal electroconvection and an off-lattice Eden model, respectively. To realize the ring initial condition experimentally, we introduce a holography-based technique that allows us to design the initial condition arbitrarily. Then, we find that fluctuation properties of ingrowing circular interfaces are distinct from those for the curved or circular KPZ subclass and, instead, are characterized by the flat subclass. More precisely, we find an asymptotic approach to the Tracy-Widom distribution for the Gaussian orthogonal ensemble and the Airy1 spatial correlation, as long as time is much shorter than the characteristic time determined by the initial curvature. Near this characteristic time, deviation from the flat KPZ subclass is found, which can be explained in terms of the correlation length and the circumference. Our results indicate that the sign of the initial curvature has a crucial role in determining the universal distribution and correlation functions of the KPZ class.

Kazumasa A. Takeuchi,
1/fα power spectrum in the Kardar-Parisi-Zhang universality class,
Journal of Physics A: Mathematical and Theoretical 50, 264006/1-17 (2017).

[Summary] The power spectrum of interface fluctuations in the (1+1)-dimensional Kardar-Parisi-Zhang (KPZ) universality class is studied both experimentally and numerically. A 1/f-type spectrum is found and characterized through a set of 'critical exponents' for the power spectrum. The recently formulated aging Wiener-Khinchin theorem accounts for the observed exponents. Interestingly, the 1/f-type spectrum in the KPZ class turns out to contain information on a universal distribution function characterizing the asymptotic state of the KPZ interfaces, namely the Baik-Rains universal variance. It is indeed observed in the presented data, both experimental and numerical, and in both circular and flat interfaces in the long time limit.

*Kyogo Kawaguchi, Ryoichiro Kageyama and *Masaki Sano,
Topological defects control collective dynamics in neural progenitor cell cultures,
Nature 545, 327-332 (2017).

[Summary] Cultured stem cells have become a standard platform not only for regenerative medicine and developmental biology but also for biophysical studies. Yet, the characterization of cultured stem cells at the level of morphology and of the macroscopic patterns resulting from cell-to-cell interactions remains largely qualitative. Here we report on the collective dynamics of cultured murine neural progenitor cells (NPCs), which are multipotent stem cells that give rise to cells in the central nervous system1. At low densities, NPCs moved randomly in an amoeba-like fashion. However, NPCs at high density elongated and aligned their shapes with one another, gliding at relatively high velocities. Although the direction of motion of individual cells reversed stochastically along the axes of alignment, the cells were capable of forming an aligned pattern up to length scales similar to that of the migratory stream observed in the adult brain2. The two-dimensional order of alignment within the culture showed a liquid-crystalline pattern containing interspersed topological defects with winding numbers of +1/2 and −1/2 (half-integer due to the nematic feature that arises from the head–tail symmetry of cell-to-cell interaction). We identified rapid cell accumulation at +1/2 defects and the formation of three-dimensional mounds. Imaging at the single-cell level around the defects allowed us to quantify the velocity field and the evolving cell density; cells not only concentrate at +1/2 defects, but also escape from −1/2 defects. We propose a generic mechanism for the instability in cell density around the defects that arises from the interplay between the anisotropic friction and the active force field.

Takaki Yamamoto and Masaki Sano,
Chirality-induced helical self-propulsion of cholesteric liquid crystal droplets,
Soft Matter 13, 3328-3333 (2017).

[Summary] We report the first experimental realization of a chiral artificial microswimmer exhibiting helical motion without any external fields. We discovered that a cholesteric liquid crystal (CLC) droplet with a helical director field swims in a helical path driven by the Marangoni flow in an aqueous surfactant solution. We also showed that the handedness of the helical path is reversed when that of the CLC droplet is reversed by replacing the chiral dopant with the enantiomer. In contrast, nematic liquid crystal (NLC) droplets exhibited ballistic motions. These results suggest that the helical motion of the CLC droplets is driven by chiral couplings between the Marangoni flow and rotational motion via the helical director field of CLC droplets.

Tomoyuki Mano, *Jean-Baptiste Delfau, Junichiro Iwasawa, and Masaki Sano,
Optimal run-and-tumble based transportation of a Janus particle with active steering,
Proceedings of the National Academy of Sciences 114, E2580–E2589 (2017).

[Summary] Commanding the swimming of micrometric objects subjected to thermal agitation is always challenging both for artificial and living systems. Now, artificial swimmers can be designed whose self-propelling force can be tuned at will. However, orienting such small particles to an arbitrary direction requires counterbalancing the random rotational diffusion. Here, we introduce a simple concept to reorient artificial swimmers, granting them a motion similar to the run-and-tumbling behavior of Escherichia coli. We demonstrate it using Janus particles with asymmetric surface coating and moving under an AC electric field. Moreover, we determine the optimal strategy and compare it with biological swimmers. Our results encourage further investigation into dynamical behavior of colloidal particles, as well as application to microscopic devices.

*Jacopo De Nardis, Pierre Le Doussal, and Kazumasa A. Takeuchi,
Memory and Universality in Interface Growth,
Physical Review Letters 118, 125701/1-5 (2017).

[Summary] Recently, very robust universal properties have been shown to arise in one-dimensional growth processes with local stochastic rules, leading to the Kardar-Parisi-Zhang (KPZ) universality class. Yet it has remained essentially unknown how fluctuations in these systems correlate at different times. Here, we derive quantitative predictions for the universal form of the two-time aging dynamics of growing interfaces and we show from first principles the breaking of ergodicity that the KPZ time evolution exhibits. We provide corroborating experimental observations on a turbulent liquid crystal system, as well as a numerical simulation of the Eden model, and we demonstrate the universality of our predictions. These results may give insight into memory effects in a broader class of far-from-equilibrium systems.

*Daiki Nishiguchi, Ken H. Nagai, Hugues Chate, and Masaki Sano,
Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria,
Physical Review E 95, 020601(R) /1-6 (2017).

[Summary] We study the collective dynamics of elongated swimmers in a very thin fluid layer by devising long, filamentous, non-tumbling bacteria. The strong confinement induces weak nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. This homogeneous but fluctuating phase, observed on the largest experimentally-accessible scale of millimeters,  exhibits the properties predicted by standard models for flocking such as the Vicsek-style model of polar particles  with nematic alignment: true long-range nematic order and non-trivial giant number fluctuations.

2016

Gioia Carinci, Cristiana Giardina, Frank Redig, Tomohiro Sasamoto,
A generalized asymmetric exclusion process with Uq(sl2) stochastic duality,
Probability Theory and Related Fields 166(3), 887-933 (2016).

[Summary] In the studies of one-dimensional asymmetric simple exclusion process(ASEP), the existence of self-duality is very useful but it has not been well understood what type of stochastic models with current have self-duality. In this paper we present a general scheme to construct stochastic processes with self-duality related to quantum group symmetries. As an example we constructed a model with multi-particle occupancy at a site related to higher spin representation of the quantum algebra Uq(sl2).

*Kazumasa A. Takeuchi and Takuma Akimoto,
Characteristic Sign Renewals of Kardar-Parisi-Zhang Fluctuations,
Journal of Statistical Physics 164, 1167-1182 (2016).

[Summary] Tracking the sign of fluctuations governed by the (1+1)-dimensional Kardar-Parisi-Zhang (KPZ) universality class, we show, both experimentally and numerically, that its evolution has an unexpected link to a simple stochastic model called the renewal process, studied in the context of aging and ergodicity breaking. Although KPZ and the renewal process are fundamentally different in many aspects, we find remarkable agreement in some of the time correlation properties, such as the recurrence time distributions and the persistence probability, while the two systems can be different in other properties. Moreover, we find inequivalence between long-time and ensemble averages in the fraction of time occupied by a specific sign of the KPZ-class fluctuations. The distribution of its long-time average converges to nontrivial broad functions, which are found to differ significantly from that of the renewal process, but instead be characteristic of KPZ. Thus, we obtain a new type of ergodicity breaking for such systems with many-body interactions. Our analysis also detects qualitative differences in time-correlation properties of circular and flat KPZ-class interfaces, which were suggested from previous experiments and simulations but still remain theoretically unexplained.

*Xiong Ding, Hugues Chate, Predrag Cvitanovic, Evangelos Siminos, and Kazumasa A. Takeuchi,
Estimating the Dimension of an Inertial Manifold from Unstable Periodic Orbits,
Physical Review Letters 117, 024101/1-5 (2016).

[Summary] We provide numerical evidence that a finite-dimensional inertial manifold on which the dynamics of a chaotic dissipative dynamical system lives can be constructed solely from the knowledge of a set of unstable periodic orbits. In particular, we determine the dimension of the inertial manifold for the Kuramoto-Sivashinsky system and find it to be equal to the “physical dimension” computed previously via the hyperbolicity properties of covariant Lyapunov vectors.

*J.-B. Delfau, John J. Molina and M. Sano,
Collective behavior of strongly confined suspensions of squirmers,
Europhysics Letters 114, 24001/1-5 (2016).

[Summary] We run numerical simulations of strongly confined suspensions of model spherical swimmers called “squirmers”. Because of the confinement, the Stokeslet dipoles generated by the particles are quickly screened and the far-field flow is dominated by the source dipole for all the different kinds of squirmers. However, we show that the collective behavior of the suspension still depends on the self-propelling mechanism of the swimmers as polar states can only be observed for neutral squirmers. We demonstrate that the near-field hydrodynamic interactions play a crucial role in the alignment of the orientation vectors of spherical particles. Moreover, we point out thatthe enstrophy and the fluid fluctuations of an active suspension also depend on the nature of the squirmers.

*Takao Ohta, Mitsusuke Tarama and Masaki Sano,
Simple model of cell crawling,
Physica D 318, 3-11 (2016).

[Summary] Based on symmetry consideration of migration and shape deformations, we formulate phenomenologically the dynamics of cell crawling in two dimensions. Forces are introduced to change the cell shape. The shape deformations induce migration of the cell on a substrate. For time-independent forces we show that not only a stationary motion but also a limit cycle oscillation of the migration velocity and the shape occurs as a result of nonlinear coupling between different deformation modes. Time-dependent forces are generated in a stochastic manner by utilizing the so-called coherence resonance of an excitable system. The present coarse-grained model has a flexibility that it can be applied, e.g., both to keratocyte cells and to View the MathML source cells, which exhibit quite different dynamics from each other. The key factors for the motile behavior inherent in each cell type are identified in our model.

*John J. Molina, Kotaro Otomura, Hayato Shiba, Hideki Kobayashi, Masaki Sano, and Ryoichi Yamamoto,
Rheological evaluation of colloidal dispersions using the smoothed profile method: formulation and applications,
Journal of Fluid Mechanics 792, 590-619 (2016).

[Summary] The smoothed profile method is extended to study the rheological behaviour of colloidal dispersions under shear flow by using the Lees–Edwards boundary conditions. We start with a reformulation of the smoothed profile method, a direct numerical simulation method for colloidal dispersions, so that it can be used with the Lees–Edwards boundary condition, under steady or oscillatory-shear flow. By this reformulation, all the resultant physical quantities, including local and total shear stresses, become available through direct calculation. Three simple rheological simulations are then performed for (1) a spherical particle, (2) a rigid bead chain and (3) a collision of two spherical particles under shear flow. Quantitative validity of these simulations is examined by comparing the viscosity with that obtained from theory and Stokesian dynamics calculations. Finally, we consider the shear-thinning behaviour of concentrated colloidal dispersions.

*Masaki Sano and Keiichi Tamai,
A Universal Transition to Turbulence in Channel Flow,
Nature Physics 12, 249-253 (2016).

[Summary] Transition from laminar to turbulent flow drastically changes the mixing, transport, and drag properties of fluids, yet when and how turbulence emerges is elusive even for simple flow within pipes and rectangular channels1,2. Unlike the onset of temporal disorder, which is identified as the universal route to chaos in confined flows3,4, characterization of the onset of spatio-temporal disorder has been an outstanding challenge because turbulent domains irregularly decay or spread as they propagate downstream. Here, through extensive experimental investigation of channel flow, we identify a distinctive transition with critical behavior. Turbulent domains continuously injected from an inlet ultimately decayed, or in contrast, spread depending on flow rates. Near a transition point, critical behavior was observed. We investigate both spatial and temporal dynamics of turbulent clusters, measuring four critical exponents, a universal scaling function and a scaling relation, all in agreement with the (2+1) dimensional directed percolation universality class.

2015

Alexei Borodin, Ivan Corwin, Leonid Petrov, Tomohiro Sasamoto,
Spectral theory for interacting particle systems solvable by coordinate Bethe ansatz,
Communications in Mathematical Physics 339(3), 1167-1245 (2015).

[Summary] In recent studies of KPZ systems, stochastic particle systems called the q-TASEP and the q-boson zero range process have been playing important roles. In this paper we have introduced a generalized process related to the orthogonal weight of the q-Hahn polynomials. We have given a formula for the moments of the currents.

*Daiki Nishiguchi and Masaki Sano,
Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field,
Physical Review E 92, 052309/1-11 (2015).

[Summary] To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters.

*Shoichi Toyabe, Masaki Sano,
Nonequilibrium Fluctuations in Biological Strands, Machines, and Cells,
Journal of the Physical Society of Japan 84, 102001/1-17 (2015).

[Summary] Can physics provide a quantitative methodology and unified view to elucidate rich and diverse biological phenomena? Nonequilibrium fluctuations are key quantities. These fluctuations have universal symmetries, convey essential information about systems’ behaviors, and are experimentally accessible in most systems. We review experimental developments to extract information from the nonequilibrium fluctuations of biological systems. In particular, we focus on the three major hierarchies in small scales: strands, molecular machines, and cells.

Tomohiro Sasamoto, Herbert Spohn,
Point-interacting Brownian motions in the KPZ universality class,
Electronic Journal of Probability 20, 1-28 (2015).

[Summary] We constructed an interacting Brownian motion model in the KPZ class. In particular the model has self-duality by which we could show that the current distribution tends to the Tracy-Widom distribution. This could be used as model for colloidal particle system which shows KPZ behaviors.

*Timothy Halpin-Healy, Kazumasa A. Takeuchi,
A KPZ Cocktail: Shaken, not stirred… -Toasting 30 years of kinetically roughened surfaces,
Journal of Statistical Physics 160, 794-814 (2015).

[Summary] The stochastic partial differential equation proposed nearly three decades ago by Kardar, Parisi and Zhang (KPZ) continues to inspire, intrigue and confound its many admirers. Here, we i) pay debts to heroic predecessors, ii) highlight additional, experimentally relevant aspects of the recently solved 1+1 KPZ problem, iii) use an expanding substrates formalism to gain access to the 3d radial KPZ equation and, lastly, iv) examining extremal paths on disordered hierarchical lattices, set our gaze upon the fate of $d = \infty$ KPZ. Clearly, there remains ample unexplored territory within the realm of KPZ and, for the hearty, much work to be done, especially in higher dimensions, where numerical and renormalization group methods are providing a deeper understanding of this iconic equation.

*Hiroyuki Ebata and Masaki Sano,
Swimming droplets driven by a surface wave,
Scientific Reports 5, 8546/1-7 (2015).

[Summary] Self-propelling motion is ubiquitous for soft active objects such as crawling cells, ac-tive filaments, and liquid droplets moving on surfaces. Deformation and energy dissi-pation are required for self-propulsion of both living and non-living matter. From the perspective of physics, searching for universal laws of self-propelled motions in a dis-sipative environment is worthwhile, regardless of the objects’ details. In this article, we propose a simple experimental system that demonstrates spontaneous migration of a droplet under uniform mechanical agitation. As we vary control parameters, sponta-neous symmetry breaking occurs sequentially, and cascades of bifurcations of the mo-tion arise. Equations describing deformable particles and hydrodynamic simulations successfully describe all of the observed motions. This system should enable us to im-prove our understanding of spontaneous motions of self-propelled objects.

*Takaki Yamamoto, Masafumi Kuroda, and Masaki Sano,
Three-dimensional analysis of thermo-mechanically rotating cholesteric liquid crystal droplets under a temperature gradient,
EPL 109, 46001/1-6 (2015).

[Summary] We studied the rotational motion of cholesteric liquid crystal droplets under a temperaturegradient (the Lehmann effect). We found that different surface treatments, planar andhomeotropic anchoring, provided three types of droplets with different textures and geometries.The rotational velocity of these droplets depends differently on their size. Determining the threedimensionalstructures of these droplets by the fluorescence confocal polarizing microscopy, wepropose a phenomenological equation to explain the rotational behavior of these droplets. Thisresult shows that the description by the Ericksen-Leslie theory should be valid in the bulk of thedroplet, but we need to take into account the surface torque induced by temperature gradient tofully understand the Lehmann effect.

Alexei Borodin, Ivan Corwin, Leonid Petrov, and Tomohiro Sasamoto,
Spectral theory for the q-boson particle system,
Compositio Mathematica 151, 1-67 (2015).

[Summary] We develop spectral theory for the generator of the q-Boson particle system. Our cen- tral result is a Plancherel type isomorphism theorem for this system. This theorem has various implications. It proves the completeness of the Bethe ansatz for the q-Boson generator and con- sequently enables us to solve the Kolmogorov forward and backward equations for general initial data. Owing to a Markov duality with q-TASEP, this leads to moment formulas which characterize the fixed time distribution of q-TASEP started from general initial conditions. The theorem also implies the biorthogonality of the left and right eigenfunctions.We consider limits of our q-Boson results to a discrete delta Bose gas considered previously by van Diejen, as well as to another discrete delta Bose gas that describes the evolution of moments of the semi-discrete stochastic heat equation (or equivalently, the O’Connell-Yor semi-discrete directed polymer partition function). A further limit takes us to the delta Bose gas which arises in studying moments of the stochastic heat equation / Kardar-Parisi-Zhang equation.

2014

Tomohiro Sasamoto, and Lauren Williams,
Combinatorics of the asymmetric exclusion process on a semi-infinite lattice,
Journal of Combinatorics 5(4), 419-434 (2014).

[Summary] We develop spectral theory for the generator of the q-Boson particle system. Our cen- tral result is a Plancherel type isomorphism theorem for this system. This theorem has various implications. It proves the completeness of the Bethe ansatz for the q-Boson generator and con- sequently enables us to solve the Kolmogorov forward and backward equations for general initial data. Owing to a Markov duality with q-TASEP, this leads to moment formulas which characterize the fixed time distribution of q-TASEP started from general initial conditions. The theorem also implies the biorthogonality of the left and right eigenfunctions.We consider limits of our q-Boson results to a discrete delta Bose gas considered previously by van Diejen, as well as to another discrete delta Bose gas that describes the evolution of moments of the semi-discrete stochastic heat equation (or equivalently, the O’Connell-Yor semi-discrete directed polymer partition function). A further limit takes us to the delta Bose gas which arises in studying moments of the stochastic heat equation / Kardar-Parisi-Zhang equation.

Ismael S. S. Carrasco, Kazumasa A. Takeuchi, Silvio da Costa Ferreira Junior, and *Tiago José Oliveira,
Interface fluctuations for deposition on enlarging flat substrates,
New Journal of Physics 16, 123057/1-20 (2014).

[Summary] We investigate solid-on-solid models that belong to the Kardar-Parisi-Zhang (KPZ) universality class on substrates that expand laterally at a constant rate. Despite the null global curvature, we show that all investigated models have asymptotic height distributions and spatial covariances in agreement with those expected for the KPZ subclass for curved surfaces. In 1+1 dimensions, the height distribution and covariance are given by the GUE Tracy-Widom distribution and the Airy2 process instead of the GOE and Airy1 foreseen for flat interfaces. These results imply that when the KPZ class splits into curved and flat subclasses, as conventionally considered, the expanding substrate may play a role equivalent to, or perhaps more important than, the global curvature. Moreover, the translational invariance of the interfaces evolving on growing domains allowed us to accurately determine, in 2+1 dimensions, the analog of the GUE Tracy-Widom distribution for height distribution and that of the Airy2 process for spatial covariance. Temporal covariance is also calculated and shown to be universal in each dimension and in each of the two subclasses. A logarithmic correction associated with the duplication of columns is observed and theoretically elucidated. Finally, crossover between regimes with fixed-size and enlarging substrates is also investigated.

Alexei Borodin, *Ivan Corwin, Tomohiro Sasamoto,
From duality to determinants for q-TASEP and ASEP,
Annals of Probability 42, 2314-2382 (2014).

[Summary] We prove duality relations for two interacting particle systems: the q-deformed totally asymmetric simple exclusion process (q-TASEP) and the asymmetric simple exclusion process (ASEP). Expectations of the duality functionals correspond to certain joint moments of particle locations or integrated currents, respectively. Duality implies that they solve systems of ODEs. These systems are integrable and for particular step and half- stationary initial data we use a nested contour integral ansatz to provide ex- plicit formulas for the systems’ solutions, and hence also the moments.

*Kazumasa A. Takeuchi,
Experimental approaches to universal out-of-equilibrium scaling laws: turbulent liquid crystal and other developments,
Journal of Statistical Mechanics: Theory and Experiment P01006/1-28 (2014).

[Summary] This is a brief survey of recent experimental studies on out-of-equilibrium scaling laws, focusing on two prominent situations where nontrivial universality classes have been identified theoretically: absorbing-state phase transitions and growing interfaces. First the paper summarizes the main results obtained for electrically driven turbulent liquid crystals, which exhibited the scaling laws for the directed percolation class at the transition between two turbulent regimes, and those for the Kardar-Parisi-Zhang class in the supercritical phase where one turbulent regime invades the other. Other experimental investigations on these universality classes and related situations are then overviewed and discussed. Some remarks on analyses of these scaling laws are also given from the practical viewpoint.

*Hirokazu Tanimoto and Masaki Sano,
A simple force-motion relation for migrating cells revealed by multipole analysis of traction stress,
Biophysical Journal 106, 16-25 (2014).

[Summary] For biophysical understanding of cell motility, the relationship between mechanical force and cell migration must be uncovered, but it remains elusive. Since cells migrate at small scale in dissipative circumstances, the inertia force is negligible and all forces should cancel out. This implies that one must quantify the spatial pattern of the force instead of just the summation to elucidate the force-motion relation. Here, we introduced multipole analysis to quantify the traction stress dynamics of migrating cells. We measured the traction stress of Dictyostelium discoideum cells and investigated the lowest two moments, the force dipole and quadrupole moments, which reflect rotational and front-rear asymmetries of the stress field. We derived a simple force-motion relation in which cells migrate along the force dipole axis with a direction determined by the force quadrupole. Furthermore, as a complementary approach, we also investigated fine structures in the stress field that show front-rear asymmetric kinetics consistent with the multipole analysis. The tight force-motion relation enables us to predict cell migration only from the traction stress patterns.

2013

*Hiroyuki Ebata and Masaki Sano,
Bifurcation from stable holes to replicating holes in vibrated dense suspensions,
Physical Review E 88, 053007/1-8 (2013).

[Summary] In vertically vibrated starch suspensions, we observe bifurcations from stable holes to replicating holes. Abovea certain acceleration, finite-amplitude deformations of the vibrated surface continue to grow until void penetratesfluid layers, and a hole forms. We studied experimentally and theoretically the parameter dependence of the holesand their stabilities. In suspensions of small dispersed particles, the circular shapes of the holes are stable. However,we find that larger particles or lower surface tension of water destabilize the circular shapes; this indicates theimportance of capillary forces acting on the dispersed particles. Around the critical acceleration for bifurcation,holes show intermittent large deformations as a precursor to hole replication. We applied a phenomenologicalmodel for deformable domains, which is used in reaction-diffusion systems. The model can explain the basicdynamics of the holes, such as intermittent behavior, probability distribution functions of deformation, and timeintervals of replication. Results from the phenomenological model match the linear growth rate below criticalitythat was estimated from experimental data.

*Patrik L. Ferrari, Tomohiro Sasamoto, Herbert Spohn,
Coupled Kardar-Parisi-Zhang Equations in One Dimension,
Journal of Statistical Physics 153, 377-399 (2013).

[Summary] Over the past years our understanding of the scaling properties of the solutions to the one-dimensional KPZ equation has advanced considerably, both theoretically and experimentally. In our contribution we export these insights to the case of coupled KPZ equations in one dimension. We establish equivalence with nonlinear fluctuating hydrodynamics for multi-component driven stochastic lattice gases. To check the predictions of the theory, we perform Monte Carlo simulations of the two-component AHR model. Its steady state is computed using the matrix product ansatz. Thereby all coefficients appearing in the coupled KPZ equations are deduced from the microscopic model. Time correlations in the steady state are simulated and we confirm not only the scaling exponent, but also the scaling function and the non-universal coefficients.

Takashi Imamura, *Tomohiro Sasamoto, Herbert Spohn,
On the equal time two-point distribution of the one-dimensional KPZ equation by replica,
Journal of Physics A: Mathematical and Theoretical 46, 355002/1-9 (2013).

[Summary] In a recent contribution, Dotsenko establishes a Fredholm determinant formula for the two-point distribution of the Kardar–Parisi–Zhang equation in the long time limit and starting from narrow wedge initial conditions. We establish that his expression is identical to the Fredholm determinant resulting from the Airy2 process.



Paper | Review

2018

*Kazumasa A. Takeuchi,
An appetizer to modern developments on the Kardar-Parisi-Zhang universality class,
Physica A 504, 77-105 (2018).

[Summary] The Kardar-Parisi-Zhang (KPZ) universality class describes a broad range of non-equilibrium fluctuations, including those of growing interfaces, directed polymers and particle transport, to name but a few. Since the year 2000, our understanding of the one-dimensional KPZ class has been completely renewed by mathematical physics approaches based on exact solutions. Mathematical physics has played a central role since then, leading to a myriad of new developments, but their implications are clearly not limited to mathematics -- as a matter of fact, it can also be studied experimentally. The aim of these lecture notes is to provide an introduction to the field that is accessible to non-specialists, reviewing basic properties of the KPZ class and highlighting main physical outcomes of mathematical developments since the year 2000. It is written in a brief and self-contained manner, with emphasis put on physical intuitions and implications, while only a small (and mostly not the latest) fraction of mathematical developments could be covered. Liquid-crystal experiments by the author and coworkers are also reviewed.



Paper | Proceedings

2018

Takashi Imamura, *Tomohiro Sasamoto,
On the q-TASEP with a random initial condition,
Theoretical and Mathematical Physics, in press.

[Summary] When studying fluctuations of models in the 1D KPZ class including the ASEP and the q-TASEP, a standard approach has been to first write down a formula for q-deformed moments and constitute their generating function. This works well for the step initial condition, but not for a random initial condition (including the stationary case) because in this case only the first few moments are finite and the rest diverge. In a previous work , we presented a method to overcome the difficulty by using the Ramanujan’s summation formula and the Cauchy determinant for the theta functions. In this note, we give an alternative approach for the q-TASEP without using them.

2014

*Kazumasa A. Takeuchi,
Experimental realization of Tracy-Widom distributions and beyond: KPZ interfaces in turbulent liquid crystal,
MSRI Publications 65, 495-507 (2014).

[Summary] Analytical studies have shown the Tracy-Widom distributions and the Airy processes in the asymptotics of a few growth models in the Kardar-Parisi-Zhang (KPZ) universality class. Here the author shows evidence that these mathematical objects arise even in a real experiment: more specifically, in growing interfaces of turbulent liquid crystal. The present article is devoted to overviewing the current status of this experimental approach to the KPZ class, which directly concerns random matrix theory and related fields of mathematical physics. In particular, the author summarizes those statistical properties which were derived rigorously for simple solvable models and realized here experimentally, and those which were evidenced in the experiment and remain to be explained by further mathematical or theoretical studies.



International Conferences

2018

Invited

*Kazumasa A. Takeuchi,
Exploring Geometry Dependence of Universal Laws for Growing Interfaces,
IBS CSLM-UNIST Soft Matter Conference (Apr. 6-7, 2018), Ulsan, Korea.

*Masaki Sano,
When Can Active Matter Become Intelligent?,
Mini-symposium “Non-equilibrium dynamics and Information Processing” (Feb. 7-9, 2018), Okinawa, Japan.

*Masaki Sano, Masahito Uwamichi, and Kyogo Kawaguchi,
Topological Defects Control Collective Dynamics in Active Matter,
Fundamental Problems in ACTIVE MATTER (Jan. 26 – Feb. 2, 2018), Aspen Center for Physics, USA.

Oral (contributed)

Tomohiro Sasamoto,
Large deviation of a tagged particle in 1D symmetric exclusion process,
Non-Equilibrium Systems and Special Functions (Jan. 8-Feb. 2, 2018), Creswick, Australia.

Matteo Mucciconi,
Stationary KPZ fluctuations for the stochastic higher spin six vertex model,
Non-Equilibrium Systems and Special Functions (Jan. 8-Feb. 2, 2018), Creswick, Australia.

Iori Hiki,
The current fluctuations and spatial correlation in the LeRoux lattice gas with periodic initial conditions,
Non-Equilibrium Systems and Special Functions (Jan. 8-Feb. 2, 2018), Creswick, Australia.

Invited

Flat Growth vs Circular Growth -implications for interfaces and beyond-,
The Berkeley Statistical Mechanics Meeting 2018 (Jan. 12-14, 2018), Berkeley, USA.


2017

Invited

*Kazumasa A. Takeuchi,
Structure controls fluctuations, but how? -in the case of growing interface fluctuations-,
International Symposium on Fluctuation and Structure out of Equilibrium 2017 (Nov. 20-23, 2017), Sendai, Japan.

Oral (contributed)

Iori Hiki,
Current Fluctuation and Spatial Correlation in Multicomponent Systems,
International Symposium on Fluctuation and Structure out of Equilibrium 2017 (Nov. 20-23, 2017), Sendai, Japan.

Invited

*Masaki Sano and Keiichi Tamai,
Transition to Turbulence and Nonequilibrium Phase Transition,
ENS-UT Workshop (Nov. 15-16, 2017), Tokyo, Japan.

Tomohiro Sasamoto,
Exact large deviation of a tracer position in 1D symmetric exclusion process,
16th International symposium “Stochastic Analysis on Large Scale Interacting Systems (Nov. 20-23, 2017), Tokyo, Japan.

*Kazumasa A. Takeuchi,
Experimental observations of statistical laws for growing interfaces & some connections to crystal facet fluctuations,
New developments in step dynamics on crystal surfaces: from nanoscale to mesoscale (Oct. 27-28, 2017), Osaka, Japan.

*Masaki Sano, Keiichi Tamai, Takahiro Tsukahara,
Transition to Turbulence in Channel and Annular Flow,
Workshop: Transition to Turbulence, Niels Bohr Institute (Oct. 23-25, 2017), Copenhagen, Denmark.

Poster

Iori Hiki,
Current fluctuations in multicomponent systems with periodic initial conditions,
Quantum Thermodynamics :Thermalization and Fluctuations (Sep. 27-30, 2017), Kyoto, Japan.

Invited

*Kazumasa A. Takeuchi,
The Tracy-Widom distribution: a possible “central limit theorem” for certain correlated random problems,
JAGFoS2017 (Sep. 21-24, 2017), Bad Neuenahr, Germany.

Hirokazu Tanimoto, Kyogo Kawaguchi, Masahito Uwamichi, *Masaki Sano,
Cell Mechanics: from single cell to multi-cellular dynamics,
Annual Meeting of The Biophysical Society of Japan (Sep. 19-21, 2017), Kumamoto, Japan.

Tomohiro Sasamoto,
Exact large deviation of a tracer position in 1D symmetric exclusion process,
3rd Workshop on Statistical Physics (Aug. 28-Sep. 1, 2017), Bogota, Colombia.

*Masaki Sano and Kyogo Kawaguchi,
Topological Defects Control Collective Dynamics in Active Matter,
STOCHASTIC THERMODYNAMICS, ACTIVE MATTER AND DRIVEN SYSTEMS, ICTS Workshop (Aug. 7-11, 2017), Bangalore, India.

Tomohiro Sasamoto,
Fluctuations and integrability of the 1D KPZ equation and discrete models,
International Workshop on Classical and Quantum Integrable Systems (Jul. 24-28, 2017), Dubna, Russia.

Kazumasa A. Takeuchi,
1D KPZ interfaces: theory and experiment,
Fundamental Problems in Statistical Physics XIV (Jul. 16-29, 2017), Bruneck, Italy.

*Masaki Sano,
Thermal and Electric Effects in Active Colloid: Thermophoresis, Self-Propulsion, Self-Assembly,
Gordon Research Conference on Plasmonically-Powered Processes (Jun. 25-30, 2017), Hong Kong, China.

*Masaki Sano and Kyogo Kawaguchi,
Orientational Order and Topological Defects in Active Matter,
9th IUPAP International Conference on Biological Physics (Jun. 7-9, 2017), Rio de Janeiro, Brazil.

*Masaki Sano and Kyogo Kawaguchi,
Rosette and Comet: Possible Roles of Topological Defects in Biological Active Matter,
International Workshop on Physical Approaches to Biological Active Matter (Jun. 1-3, 2017), Porto De Galinhas, Brazil.

*Kazumasa A. Takeuchi,
Examples of absorbing-state transitions and universal hysteresis,
International workshop on Glasses and Related Nonequilibrium Systems (Mar. 21-23, 2017), Osaka, Japan.

Oral (contributed)

*Kazumasa A. Takeuchi,
Exploring Geometry Dependence of Kardar-Parisi-Zhang Interfaces,
Physical and mathematical approaches to interacting particle systems -In honor of 70th birthday of Herbert Spohn- (Jan. 11-12, 2017), Tokyo, Japan.

Invited

*Kazumasa A. Takeuchi,
Integrability and universality behind a random growth experiment,
Frontiers in Mathematical Physics (Jan. 6-9, 2017), Tokyo, Japan.


2016

Invited

Tomohiro Sasamoto,
Large deviation of a tagged particle in 1D symmetric exclusion process,
Dynamics Days Asia Pacific 9 (Dec. 14-17, 2016), Hong Kong, China.

Oral (contributed)

Masaki Sano,
On the Role of Topological Defects in Active Matter,
International Symposium on Universal Biology 2016 (Nov. 28-29, 2016), Tokyo, Japan.

Invited

Masaki Sano,
On the Role of Topological Defects in Active Soft Matter,
ENS-UT Joint workshop (Nov. 15-17, 2016), Paris, France.

*Kazumasa A. Takeuchi,
Geometry-dependent interface fluctuations and their implications for chaos instability,
Interdisciplinary Applications of Nonlinear Science (Nov. 3-6, 2016), Kagoshima, Japan.

*Masaki Sano, Kyogo Kawaguchi,
On the Role of Topological Defects in Active Matter,
Interdisciplinary Applications of Nonlinear Science (Nov. 3-6, 2016), Kagoshima, Japan.

Tomohiro Sasamoto,
An analysis of q-TASEP with a random initial condition,
15th Stochastic Analysis on Large Scale Interacting Systems (Nov. 2-4, 2016), Tokyo, Japan.

*Kazumasa A. Takeuchi,
ASEP as a surface growth model: universal fluctuation and its experimental test,
Conference on Driven Stochastic Transport in Low-Dimensional Systems (Sep. 27-29, 2016), Tehran, Iran.

*Masaki Sano, Kyogo Kawaguchi,
Dynamical Order and Topological Defects in Active Matter: from Molecule to Cell Sheet,
16th KIAS Conference on Protein Structure and Function (Sep. 22-24, 2016), Seoul, Korea.

*Masaki Sano, Keiichi Tamai,
Universal Transition to Turbulence in Shear Flow of Simple and Complex Fluids,
StatPhys Taiwan 2016 (Sep. 6-8, 2016), Taipei, Taiwan.

*Masaki Sano, Keiichi Tamai,
Universal critical behavior of the transition to turbulence in channel flow,
International Congress of Theoretical and Applied Mechanics 2016 (Aug. 21-26, 2016), Montreal, Canada.

Oral (contributed)

*Yosuke Fukai and Kazumasa A. Takeuchi,
Kardar-Parisi-Zhang interfaces with curved initial conditions — what exists “between” the universality subclasses?,
International Workshop on Stochastic Thermodynamics and Active Matters (Aug. 15-16, 2016), Beijing, China.

Invited

*Kazumasa A. Takeuchi,
Growth with noise: experiments and theory,
Nonequilibrium Statistical Physics & Active Matter Systems — School and Workshop (Aug. 8-20, 2016), Beijing, China.

Oral (contributed)

*Masaki Sano, Keiichi Tamai,
Criticalities at the Transition to Turbulence in Shear Flow,
STATPHYS26 (Jul. 18-22, 2016), Lyon, France.

*Kazumasa A. Takeuchi and Takuma Akimoto,
Anomalous time correlation of KPZ and weak ergodicity breaking,
STATPHYS26 (Jul. 18-22, 2016), Lyon, France.

Poster

*Yosuke Fukai and Kazumasa A. Takeuchi,
Between universality subclasses: numerical and experimental results for KPZ interfaces with curved initial conditions,
STATPHYS26 (July 18-22, 2016), Lyon, France.

Oral (contributed)

*Kazumasa A. Takeuchi,
Slow relaxation and aging of universal KPZ fluctuations: how different are circular and flat interfaces?,
Stat’Phys 26 – Statistical Physics Conference Satellite, Non-equilibrium dynamics in classical and quantum systems: From quenches to slow relaxations (Jul. 13-15, 2016), Pont-a-Mousson, France.

*Yosuke Fukai and Kazumasa A. Takeuchi,
Crossover between Kardar-Parisi-Zhang Subclasses in Interfaces with Curved Initial Conditions,
Stat’Phys 26 – Statistical Physics Conference Satellite, Non-equilibrium dynamics in classical and quantum systems: From quenches to slow relaxations (Jul. 13-15, 2016), Pont-a-Mousson, France.

Invited

Tomohiro Sasamoto,
Large deviation of a tagged particle for stationary 1D symmetric simple exclusion process,
Non-equilibrium dynamics in classical and quantum systems: from quenches to slow relaxations (Jul. 13-15, 2016), Pont-a-Mousson, France.

Masaki Sano,
Research Overview on Soft Active Matter,
Big Waves of Theoretical Science in ​Okinawa (Jul. 8-11, 2016), Okinawa, Japan.

*Masaki Sano, Keiichi Tamai,
Does the Transition to Turbulence in Shear Flow belong to the Directed Percolation Universality Class?,
7th KIAS Conference on Statistical Mechanics (Jul. 4-7, 2016), Seoul, Korea.

Keynote/Plenary

Masaki Sano,
Thermophoresis, Self-Propulsion, and Collective Behavior of Janus Particles,
12th International Meeting on Thermodiffusion (May 30- Jun. 3, 2016), Madrid, Spain.

Invited

Masaki Sano,
Interaction and Possible Long Range Order in Active Matter Experiments II,
IASBS-ICTP School on Active Matter and Chemotaxis (May 14-25, 2016), Zanjan, Iran.

Masaki Sano,
Interaction and Possible Long Range Order in Active Matter Experiments I,
IASBS-ICTP School on Active Matter and Chemotaxis (May 14-25, 2016), Zanjan, Iran.

Masaki Sano,
Instabilities Leading to Chaos and Turbulence,
International Workshop New Frontiers in Nonlinear Sciences (Mar. 6-8, 2016), Niseko, Japan.

Masaki Sano,
Large Scale Collective Behavior in Nematic State of Active Biological Systems,
LMU-UT Joint Workshop (Feb. 29- Mar. 1, 2016), Tokyo, Japan.

*Kazumasa A. Takeuchi,
Time correlation properties of KPZ fluctuations: from experimental perspectives,
New approaches to non-equilibrium and random systems: KPZ integrability, universality, applications and experiments (Jan.11- Mar.11, 2016), Santa Barbara, USA.

Keynote/Plenary

*Masaki Sano and Keiichi Tamai,
A Universal Transition to Turbulence in Channel Flow,
Extreme events and criticality in fluid mechanics: computations and analysis (Jan. 25-29, 2016), Toronto, Canada.


2015

Invited

*Tomohiro Sasamoto,
Construction of asymmetric interacting particle systems with self-duality,
Master lectures in the current topics in mathematical physics and probability (Dec. 27-30, 2015), Sanya, China.

*Tomohiro Sasamoto,
Stochastic dualities for asymmetric interacting particle systems,
Spectra of Random Operators and Related Topics (Dec. 10-12, 2015), Hiyoshi, Japan.

*Tomohiro Sasamoto,
Application of duality to stochastic non-equilibrium models,
Non-equilibrium Statistical Physics (Oct. 26- Nov. 20), Bangalore, India.

Tomohiro Sasamoto,
The 1D KPZ equation: exact solutions and universality,
Analytical Results in Statistical Physics (Nov. 5-6, 2015), Paris, France.

*Kazumasa A. Takeuchi,
Random-matrix distributions under microscope: evidence for universal interfacial fluctuations,
RMT2015: Random matrix theory from fundamental mathematics to biological applications (Nov. 2-6, 2015), Okinawa, Japan.

*Tomohiro Sasamoto,
A determinantal structure for a finite temperature polymer model,
RMT2015: Random matrix theory from fundamental mathematics to biological applications (Nov. 2-6, 2015), OIST, Japan.

*Tomohiro Sasamoto,
Dualities for asymmetric interacting particle systems,
Stochastic Analysis on Large Scale Interacting Systems 2015 (Oct. 26-29, 2015), Kyoto, Japan.

*Masaki Sano,
Interaction and Collective Dynamics of Self-Propelled Particles,
Nonequilibrium Collective Dynamics: Bridging the Gap between Hard and Soft Materials (NECD15) (Oct. 5-8, 2015), Potsdam, Germany.

Poster

*Yosuke Fukai and Kazumasa A. Takeuchi,
Curved KPZ interface in liquid crystal electroconvection and numerical model,
iCeMS International Symposium Hierarchical Dynamics in Soft Materials and Biological Matter (Sep. 23-26, 2015), Kyoto, Japan.

Invited

*Kazumasa A. Takeuchi,
Universal Fluctuations of Growing Interfaces,
iCeMS International Symposium Hierarchical Dynamics in Soft Materials and Biological Matter (Sep. 23-26, 2015), Kyoto, Japan.

*Masaki Sano, Kyogo Kawaguchi, and Hirokazu Tanimoto ,
Uncovering cell mechanics: from single cell to multi-cellular dynamics,
iCeMS International Symposium Hierarchical Dynamics in Soft Materials and Biological Matter (Sep. 23-26, 2015), Kyoto, Japan.

Poster

*Kazumasa A. Takeuchi and Takuma Akimoto,
Weak ergodicity breaking in KPZ-class growing interfaces,
International Symposium on Fluctuation and Structure out of Equilibrium 2015 (SFS2015) (Aug. 20-23, 2015), Kyoto, Japan.

*Yosuke Fukai and Kazumasa A. Takeuchi,
Kardar-Parisi-Zhang interfaces with finite curvature,
International Symposium on Fluctuation and Structure out of Equilibrium 2015 (SFS2015) (Aug. 20-23, 2015), Kyoto, Japan.

*Masahiro Takahashi, Michikazu Kobayashi, Kazumasa A. Takeuchi,
Universality Class of Quantum Turbulence Transitions in Superfluids,
International Symposium on Fluctuation and Structure out of Equilibrium 2015 (SFS2015) (Aug. 20-23, 2015), Kyoto, Japan.

Invited

*Masaki Sano,
Universal Transition Route to Turbulence in Simple and Complex Fluids,
International Symposium on Fluctuation and Structure out of Equilibrium 2015 (SFS2015) (Aug. 20-23, 2015), Kyoto, Japan.

*Kazumasa A. Takeuchi,
Universal transitions to turbulence: from simple fluid to liquid crystal, and quantum fluid,
Yukawa International Seminar 2015 (YKIS2015): New Frontiers in Non-equilibrium Statistical Physics 2015 (Aug. 17-19, 2015), Kyoto, Japan.

Poster

*Masahiro Takahashi, Michikazu Kobayashi, Kazumasa A. Takeuchi,
Critical exponents of laminar-turbulent transition in superfluids with quantized vortices,
Yukawa International Seminar 2015 (YKIS2015): New Frontiers in Non-equilibrium Statistical Physics 2015 (Aug. 17-19, 2015), Kyoto, Japan.

Invited

*Tomohiro Sasamoto,
The 1D KPZ equation and its universality,
Yukawa International Seminar 2015 (YKIS2015): New Frontiers in Non-equilibrium Statistical Physics 2015 (Aug. 17-19, 2015), Kyoto, Japan.

Poster

*Masahiro Takahashi, Michikazu Kobayashi, Kazumasa A. Takeuchi,
Directed Percolation Universality in Superfluids with Turbulent Vortices,
2015 International Symposium on Quantum Fluids and Solids (QFS2015) (Aug. 9-15, 2015), Niagara Falls, America.

*Yosuke Fukai and Kazumasa A. Takeuchi,
Experimental and Numerical Approaches to Universality in Growing Scale-invariant Interfaces,
Summer school: Stochastic processes and random matrices (Jul. 6-31, 2015), Les Houches, France.

Invited

*Tomohiro Sasamoto,
A determinantal structure for the O’Connell-Yor polymer mode,
Random Polymers and Algebraic Combinatorics (May 25-29, 2015), Oxford, UK.

*Masaki Sano,
Different phases and patterns in biological active nematic systems,
Conference on Physics of Active Matter (May 12-16, 2015), Suzhou, China.

*Tomohiro Sasamoto,
A determinantal structure for finite temperature directed polymer,
113th Statistical Mechanics Conference (May 10-12, 2015), Rutgers, USA.

*Masaki Sano,
Active colloids: hydrodynamic and electrostatic interactions,
Spring School on Active Matter (May 9-10, 2015), Beijing, China.

*Tomohiro Sasamoto,
A determinantal structure for the O’Connell-Yor polymer model,
Workshop on stochastic processes in random media (May 4-15, 2015), Singapore.

*Masaki Sano,
Universal Transition Routes to Turbulence in Simple and Complex Fluids,
Physics of Structural and Dynamical Hierarchy in Soft Matter (Mar. 16-18, 2015), Tokyo, Japan.

*Masaki Sano,
Collective Motion in Active Suspension: From Molecule to Colloid,
首都大学東京 公開シンポジウム「ソフトマターを基盤とするバイオ系の構築」 (Mar. 9, 2015), Tokyo, Japan.

*Masaki Sano,
Experimental Demonstration of Information-to-Energy Conversion in Small Fluctuating Systems,
APS March Meeting 2015 (Mar. 2-6, 2015), San Antonio, USA.

*Kazumasa A. Takeuchi,
Universal fluctuations of growing interfaces and characterization via sign renewals,
Focus Meeting of the Kyoto Winter School for Statistical Mechanics (Feb. 16-17, 2015), Kyoto, Japan.

*Masaki Sano,
Introductory talk: diversity and universality in active matter,
Kyoto Winter School for Statistical Mechanics, Frontiers in Statistical Mechanics: From Nonequilibrium Fluctuations to Active Matter (Feb. 4-17, 2015), Kyoto, Japan.

*Masaki Sano,
Collective Motion of Self-Propelled Objects: From Molecules to Colloids,
International Conference on Mathematical Modeling and Applications 2014 ‘Crowd Dynamics’ (Jan. 10-12, 2015), Tokyo, Japan.

*Masaki Sano,
Cell Mechanics: from single cell to multi-cellular dynamics,
iTHES Colloquium (Jan. 8, 2015), Wako, Japan.


2014

Invited

*Masaki Sano,
Universal Transition Routes to Turbulence in Simple and Complex Fluids,
Vires Acquirit Eundo: The University of Tokyo x OIST Joint Symposium (Dec. 12-13, 2014), Okinawa, Japan.

Hirokazu Tanimoto, Kyogo Kawaguchi, *Masaki Sano,
Cell Mechanics: from single cell to multi-cellular dynamics,
ENS-UT Joint Workshop in Physics, 2014 (Dec. 8-9, 2014), Paris, France.

*Masaki Sano,
移流のあるマクロ系における非平衡相転移現象-流体における層流・乱流転移と液晶における乱流・乱流転移-,
東北大学物性コロキュウム (Dec. 1, 2014), Sendai, Japan.

*Masaki Sano, Hong-Ren Jiang, and Daiki Nishiguchi,
Collective Dynamics of Active Particles Driven by a Surface Slip Flow,
7th International Workshop on Advanced Materials Science and Nanotechnology, IWAMSN 2014 (Nov. 2-6, 2014), Ha Long, Vietnam.

*Masaki Sano,
Phase transitions in nonequilibrium systems,
Cooperation in Physics Workshop: Todai-LMU (Oct. 27-29, 2014), Munich, Germany.

*Kazumasa A. Takeuchi,
Weak ergodicity breaking in KPZ-class interfaces,
Fluctuation and Correlation in Stochastic Systems (Oct. 15, 2014), Tokyo, Japan.

*Masaki Sano,
From Non-Equilibrium Physics to Active Matter,
The 20th International Conference on DNA Computing and Molecular Programming (Sep. 22-26, 2014), Kyoto, Japan.

Oral (contributed)

*Kazumasa A. Takeuchi,
KPZ-class interfaces in turbulent liquid crystal: beyond a “mere” confirmation,
Interface fluctuations and KPZ universality class – unifying mathematical, theoretical, and experimental approaches (Aug. 20-23, 2014), Kyoto, Japan.

*Tomohiro Sasamoto,
A few caveats and exact solutions for the 1D KPZ equation,
Interface fluctuations and KPZ universality class – unifying mathematical, theoretical, and experimental approaches (Aug. 20-23, 2014), Kyoto, Japan.

Invited

*Kazumasa A. Takeuchi,
Experimental evidence of KPZ growing interfaces and beyond,
School on Non-linear Dynamics, Dynamical Transitions and Instabilities in Classical and Quantum Systems (Jul. 14 – Aug. 1, 2014), Trieste, Italy.

Tomohiro Sasamoto,
The one-dimensional KPZ equation and its universality,
37th Conference on Stochastic Processes and Their Applications (Jul. 28- Aug. 1, 2014), Buenos Aires, Argentina.

*Kazumasa A. Takeuchi,
Covariant Lyapunov vectors capture the collective dynamics of large chaotic systems,
Dynamics Days Asia Pacific 08 (Jul. 21-24, 2014), Chennai, India.

*Tomohiro Sasamoto,
Fluctuations for 1D KPZ equation and Related Models,
School on Non-linear Dynamics, Dynamical Transitions and Instabilities in Classical and Quantum Systems (Jul. 14- Aug. 1, 2014), Trieste, Italy.

*Masaki Sano,
A simple force-motion relation for crawling cells,
Breaking Barrier from Physics to Biology (II) (Jun. 14-16, 2014), Xi’an, China.

Oral (contributed)

*Kazumasa A. Takeuchi,
Turbulent liquid crystals unveil universal fluctuation properties of growing interfaces,
Advances in Nonequilibrium Statistical Mechanics, large deviations and long-range correlations, extreme value statistics, anomalous transport and long-range interactions (May 5- Jul. 4, 2014), Florence, Italy.

Invited

*Tomohiro Sasamoto,
The one-dimensional KPZ equation: recent progress and beyond,
Nonequilibrium Problems in Physics and Mathematics (Jun. 2-6, 2014), Ascona, Switzerland.

*Kazumasa A. Takeuchi,
Exploring universal scaling laws far from equilibrium with turbulent liquid crystal,
APS March Meeting (Mar. 3-7, 2014), Denver, USA.

*Masaki Sano,
From Brownian to Driven and Active Dynamics of Colloids: Energetics and Fluctuations,
IAS Program on Frontiers of Soft Matter Physics: from Nonequilibrium Dynamics to Active Matter (Jan. 2-29, 2014), Hong Kong, China.


2013

Invited

*Tomohiro Sasamoto,
Replica and dualities for KPZ systems,
Spectra of Random Operators and Related Topics (Dec. 5-7, 2013), Kyoto, Japan.

*Kazumasa A. Takeuchi,
Experimental evidence for universal fluctuation properties of growing interfaces,
12th Workshop on Stochastic Analysis on Large Scale Interacting Systems (Nov. 21-23, 2013), Tokyo, Japan.

*Tomohiro Sasamoto,
Fluctuations for one-dimensional Brownian motions with oblique reflection,
12th Workshop on Stochastic Analysis on Large Scale Interacting Systems (Nov. 21-23, 2013), Tokyo, Japan.

*Tomohiro Sasamoto,
The KPZ scaling functions in systems with a few conserved quantities,
East Asia Joint Seminar on Statistical Physics 2013 (Nov. 21-24, 2013), Kyoto, Japan.

*Kazumasa A. Takeuchi,
Critical phenomena out of equilibrium probed by liquid-crystal turbulence,
East Asia Joint Seminars on Statistical Physics 2013 (Oct. 21-24, 2013), Kyoto, Japan.

*Masaki Sano,
Thermal Non-equilibrium Transport in Colloids and Liquid Crystals,
Lorentz Center Workshop: Hot Nanostructures (Oct. 21-25, 2013), Leiden, Netherland.

*Kazumasa A. Takeuchi,
Powerful and geometry-dependent universality in growing interfaces,
Small Systems far from Equilibrium: Order, Correlations, and Fluctuations (Oct, 14-18, 2013), Dresden, Germany.

*Masaki Sano,
Self-Organizing Dynamics of Active Colloids,
Diffusion Fundamentals V: Basic Principles of Diffusion Theory, Experiment, and Application (Aug. 26-28, 2013), Leipzig, Germany.

*Masaki Sano,
Collective Dynamics of Active Colloids,
Gordon Research Conference (Bio-Soft Matter: Dynamical and Structural Complexity) (Aug. 18-23, 2013), Colby-Sawyer, NH, USA.

*Masaki Sano,
Research on Non-equilibrium Systems Aims at Protolife,
International Workshop “From Soft Matter to Protocell” (Sep. 18-20, 2013), Sendai, Japan.

Poster

*Kazumasa A. Takeuchi,
Emergence of random-matrix statistics as universal properties of growing interfaces,
satellite meeting of STATPHYS25 & YITP workshop, Mathematical Statistical Physics (July. 29- Aug. 03, 2013), Kyoto, Japan.

Invited

*Kazumasa A. Takeuchi,
Exploring universal out-of-equilibrium scaling laws with turbulent liquid crystal,
XXV IUPAP International Conference on Statistical Physics, STATPHYS25 (Jul. 22-26, 2013), Seoul, Korea.

Oral (contributed)

*Tomohiro Sasamoto,
Exact stationary two-point function for the 1D KPZ equation,
XXV IUPAP International Conference on Statistical Physics, STATPHYS25 (July, 22-26, 2013), Seoul, Korea.

Invited

*Masaki Sano and Hirokazu Tanimoto,
Detecting Symmetry Breaking in Traction Force Dynamics of Migrating Amoeboid Cells,
Patterns and waves in populations of cells and active particles (Jul. 19-20, 2013), Seoul, Korea.

Grant-in-Aid for Scientific Research (KAKENHI) on Innovative Areas, MEXT, Japan
Synergy of Fluctuation and Structure : Quest for Universal Laws in Non-Equilibrium Systems