## Research projects in the Lab

### Quest for out-of-equilibrium laws of physics through liquid crystal experiments

#### Direct observation of 3D dynamics of topological defect lines

We observed topological defects of liquid crystal by confocal microscopy and captured their characteristic topological events, in particular, reconnections.

(to appear)

#### Ising dynamic scaling laws in liquid crystal

We inspected universal dynamic scaling laws of Model A, which rule ordering processes of, e.g., Ising ferromagnets, by liquid crystal. (to appear)

#### KPZ universal fluctuations in growing turbulent interfaces

Growing interfaces turned out to be ruled by universal laws linked to various areas of physics and mathematics.

#### Universal critical phenomenon discovered in topological-defect turbulence

All up once you have entered... The directed percolation universality class, theoretically expected in such a situation, was experimentally found for the first time.

### Physics of active matter

#### Route to turbulence of bacterial suspension

We developed a method to solve a model equation for bacterial suspension with arbitrary boundaries. This allowed us to unveil a characteristic route to turbulence. (to appear)

#### Emergence of bacterial glass

We discovered that proliferating bacterial populations spontaneously undergo a transition from an active fluid phase to an active glass. (to appear)

#### Bacterial colony growth and topological defects

We discovered an overlooked role of topological defects in the three-dimensional growth of bacterial colonies. (to appear)

#### Emergent order in bacterial collective motion

How and when can any order emerge in usually turbulent dense bacterial collective motion? Our experimental findings led to a general framework.

#### Collective motion of self-propelled colloidal particles

By using active colloids fuelled by an electric field, we explore universal non-equilibrium laws in self-propelled particle systems.

### Physical experiments on microbial systems

#### Extensive microperfusion system (EMPS) for bacterial population experiments

With this new microfluidic device, we can culture and observe bacteria for long time under a uniform condition. Several projects on bacterial populations are ongoing with this device.

#### Scale invariance in cell size fluctuations

With EMPS, we experimentally found universal scaling laws in cell size fluctuations.

(to appear)

### Out-of-equilibrium phenomena in macroscopic soft matter systems

#### Jamming of a spongy granular system

We propose a new model system of largely deformable grains, where we discovered a novel fluid-amorphous transition. (to appear)

### Statistical characterization of large chaotic systems

#### Time-series analysis for measuring instability of large chaotic systems

We develop a new method of time-series analysis for measuring instability of large chaotic systems, applicable when the system is highly symmetric.

(to appear)

#### New developments on instability analysis

Using Lyapunov vectors that became numerically accessible recently, we characterized collective instability and effective dimensions of large chaotic systems.