Flow field of a unitary Fermi gas for the scissors mode

The scissors mode plays a crucial role in the study of the unitary Fermi gas. In this paper, we simulate the scissors mode by solving the hydrodynamic equations with appropriate initial conditions, and then extract the flow field of the gas. The flow fields in different regimes are found to be essentially different. The characteristic differences in the flow patterns between the superfluid and the normal viscous fluid are presented. Irrotational flow signals superfluidity, while rotational one indicates normal hydrodynamical behavior. These different characteristics can be visualized by the velocity portraits of the flow, which provide an intuitive way to discriminate the states of the Fermi gas.

Hydrodynamic Limit for a Type of Exclusion Process with Slow Bonds in Dimension d ≥ 2

Let Λ be a connected closed region with smooth boundary contained in the d-dimensional continuous torus Td. In the discrete torus N-1TdN, we consider a nearest-neighbor symmetric exclusion process where occupancies of neighboring sites are exchanged at rates depending on Λ in the following way: if both sites are in Λ or Λc, the exchange rate is 1; if one site is in Λ and the other site is in Λc, and the direction of the bond connecting the sites is ej, then the exchange rate is defined as N-1 times the absolute value of the inner product between ej and the normal exterior vector to ∂Λ. We show that this exclusion-type process has a nontrivial hydrodynamical behavior under diffusive scaling and, in the continuum limit, particles are not blocked or reflected by ∂Λ. Thus, the model represents a system of particles under hard-core interaction in the presence of a permeable membrane which slows down the passage of particles between two complementary regions.

Hydrodynamic Limit for a Type of Exclusion Process with Slow Bonds in Dimension d ≥ 2

Let Λ be a connected closed region with smooth boundary contained in the d-dimensional continuous torus T d . In the discrete torus N -1 T d N , we consider a nearest-neighbor symmetric exclusion process where occupancies of neighboring sites are exchanged at rates depending on Λ in the following way: if both sites are in Λ or Λc, the exchange rate is 1; if one site is in Λ and the other site is in Λc, and the direction of the bond connecting the sites is e j , then the exchange rate is defined as N -1 times the absolute value of the inner product between e j and the normal exterior vector to ∂Λ. We show that this exclusion-type process has a nontrivial hydrodynamical behavior under diffusive scaling and, in the continuum limit, particles are not blocked or reflected by ∂Λ. Thus, the model represents a system of particles under hard-core interaction in the presence of a permeable membrane which slows down the passage of particles between two complementary regions.

Conformational symmetry and vibrational dynamics of polymers

Polymers are an important class of materials, and their conformation dictates their dynamical, thermodynamical, and hydrodynamical behavior. Several spectroscopic and other techniques have been employed to characterize their conformation. However, little use has been made of group-theoretical techniques except in the classification of symmetry species. In the present review, an attempt has been made to correlate normal modes and their dispersion profiles with the conformation of the polymeric systems. This has been attempted in the case of 2-, 3-, 4-fold and α-helical polymers.

Study on the hydrodynamical behavior of thin foils irradiated by near-field ISI smoothed beams

The evolution of thin foils accelerated over distances much greater than their in-flight thickness has been studied for a classical, low power density regime (5 × 1012 and 2 × 1013 W/cm2 at λ = 1.054 μm, 0.15 THz bandwidth). Two illumination modes have been used, one of these being based on a near-field, multi-lens array ISI smoothing, the other on focusing by F/1 aspherical lenses. The results seem to be encouraging with regard to the possibility of getting smooth, spatially uniform acceleration over distances of the order of 100 × IFFT (In-Flight-Foil Thickness). The experiments with nonsmoothed beams have shown a sort of refractive interchange stabilization for the initial on-target imprinting of the illumination non-uniformities.