Induced interaction in a spin-polarized Fermi gas

We study the effect of the induced interaction on the superfluidtransition temperature of a spin-polarized Fermi gas. In the BCS limit, the polarization is very small in the superfluid state, and the effect of the induced interaction is almost the same as in the spin-balanced case. The temperature Tt and the polarization Pt of the tricritical point are both reduced from mean-field results by a factor about 2.22. This reduction is also significant beyond the BCS limit. In the unitary limit, we find (Pt,Tt/TF)=(0.42,0.16), in comparison with mean-field and experimental results.Comment: 6 pages, 2 figure

On the Computation Power of Name Parameterization in Higher-order Processes

Parameterization extends higher-order processes with the capability of abstraction (akin to that in lambda-calculus), and is known to be able to enhance the expressiveness. This paper focuses on the parameterization of names, i.e. a construct that maps a name to a process, in the higher-order setting. We provide two results concerning its computation capacity. First, name parameterization brings up a complete model, in the sense that it can express an elementary interactive model with built-in recursive functions. Second, we compare name parameterization with the well-known pi-calculus, and provide two encodings between them.Comment: In Proceedings ICE 2015, arXiv:1508.0459

Collinear antiferromagnetic state in a two-dimensional Hubbard model at half filling

In a half-filled Hubbard model on a square lattice, the next-nearest-neighbor hopping causes spin frustration, and the collinear antiferromagnetic (CAF) state appears as the ground state with suitable parameters. We find that there is a metal-insulator transition in the CAF state at a critical on-site repulsion. When the repulsion is small, the CAF state is metallic, and a van Hove singularity can be close to the Fermi surface, resulting in either a kink or a discontinuity in the magnetic moment. When the on-site repulsion is large, the CAF state is a Mott insulator. A first-order transition from the CAF phase to the antiferromagnetic phase and a second-order phase transition from the CAF phase to the paramagnetic phase are obtained in the phase diagram at zero temperature.Comment: 5 pages, 5 figures, two column

The induced interaction in a Fermi gas with a BEC-BCS crossover

We study the effect of the induced interaction on the superfluid transition temperature of a Fermi gas with a BEC-BCS crossover. The Gorkov-Melik-Barkhudarov theory about the induced interaction is extended from the BCS side to the entire crossover, and the pairing fluctuation is treated in the approach by Nozi\`{e}res and Schmitt-Rink. At unitarity, the induced interaction reduces the transition temperature by about twenty percent. In the BCS limit, the transition temperature is reduced by a factor about 2.22, as found by Gorkov and Melik-Barkhudarov. Our result shows that the effect of the induced interaction is important both on the BCS side and in the unitary region.Comment: 11 pages, 3 figures, to be published in PR

Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover

The Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover is derived by the path-integral method. In addition to the standard Ginzburg-Landau equation, a second equation describing the total atom density is obtained. These two coupled equations are necessary to describe both homogeneous and inhomogeneous systems. The Ginzburg-Landau theory is valid near the transition temperature $T_c$ on both sides of the crossover. In the weakly-interacting BEC region, it is also accurate at zero temperature where the Ginzburg-Landau equation can be mapped onto the Gross-Pitaevskii (GP) equation. The applicability of GP equation at finite temperature is discussed. On the BEC side, the fluctuation of the order parameter is studied and the renormalization to the molecule coupling constant is obtained.Comment: 16 pages, 2 figures, to be published in PR

Joint Domain Based Massive Access for Small Packets Traffic of Uplink Wireless Channel

The fifth generation (5G) communication scenarios such as the cellular network and the emerging machine type communications will produce massive small packets. To support massive connectivity and avoid signaling overhead caused by the transmission of those small packets, this paper proposes a novel method to improve the transmission efficiency for massive connections of wireless uplink channel. The proposed method combines compressive sensing (CS) with power domain NOMA jointly, especially neither the scheduling nor the centralized power allocation is necessary in the method. Both the analysis and simulation show that the method can support up to two or three times overloading.Comment: 6 pages, 5 figures.submitted to globecom 201