Fluctuations in Chemical Gelation

We study a chemical gelation model in two dimensions which includes both monomer aggregations and bond fluctuations. Our numerical simulation shows that a sol-gel transition occurs when an initial monomer concentration is above a critical concentration. Fractal aggregates grow until the sol-gel transition occurs. After the gelation, however, bond fluctuations break the fractal structure and a novel inhomogeneous gel fibre network appears instead. A pore size distribution of the inhomogeneous structure shows the existence of hierarchical structures in the gel phase. It is also found that slow dynamics appear near the critical concentration.Comment: 6 pages, 10figure

Interaction of a Relativistic Magnetized Collisionless Shock with a Dense Clump

The interactions between a relativistic magnetized collisionless shock and dense clumps have been expected to play a crucial role on the magnetic field amplification and cosmic-ray acceleration. We investigate this process by two-dimensional Particle-In-Cell (PIC) simulations for the first time, where the clump size is much larger than the gyroradius of downstream particles. We also perform relativistic magnetohydrodynamic (MHD) simulations for the same condition to see the kinetic effects. We find that particles escape from the shocked clump along magnetic field lines in the PIC simulations, so that the vorticity is lower than that in the MHD simulations. Moreover, in both the PIC and MHD simulations, the shocked clump quickly decelerates because of the Lorentz contraction. Owing to the escape and the deceleration, the shocked clump cannot amplify the downstream magnetic field in relativistic collisionless shocks. This large-scale PIC simulation opens a new window to understand large-scale behaviors in collisionless plasma systems

Blockade of phonon hopping in trapped ions in the presence of multiple local phonons

Driving an ion at a motional sideband transition induces the Jaynes--Cummings (JC) interaction. This JC interaction creates an anharmonic ladder of JC eigenstates, resulting in the suppression of phonon hopping due to energy conservation. Here, we realize phonon blockade in the presence of multiple local phonons in a trapped-ion chain. Our work establishes a key technological component for quantum simulation with multiple bosonic particles, which can simulate classically intractable problems.Comment: 6 pages, 4 figure