Fractional Quantum Hall Effect of Hard-Core Bosons in Topological Flat Bands

Recent proposals of topological flat band (TFB) models have provided a new route to realize the fractional quantum Hall effect (FQHE) without Landau levels. We study hard-core bosons with short-range interactions in two representative TFB models, one of which is the well known Haldane model (but with different parameters). We demonstrate that FQHE states emerge with signatures of even number of quasi-degenerate ground states on a torus and a robust spectrum gap separating these states from higher energy spectrum. We also establish quantum phase diagrams for the filling factor 1/2 and illustrate quantum phase transitions to other competing symmetry-breaking phases.Comment: 4 pages, 6 figure

Experimental Investigation and Gaussian Process Emulation of Steel Skeleton Reinforced Concrete Behaviors in Split Hopkinson Pressure Bar Tests

This paper conducts split Hopkinson pressure bar (SHPB) experiments to investigate the dynamic compressive properties of steel skeleton reinforced concrete (SSRC) materials. The SSRC specimens with the different volume fraction of steel range from 0 to 2.94% are investigated by conducting quasi-static and SHPB compression tests, respectively. In SHPB tests, the strain rate achieves from 30 s-1 to 100 s-1. The concrete matrix for all SSRC specimens is mixed to obtain a compressive strength of 45 MPa. The influences of different steel skeleton arrangements on the compressive strength, energy absorption, dynamic strain-stress relations, and failure modes are discussed and compared. The most important indicator, dynamic increase factor (DIF) relations of SSRC for compressive strength and Young’s modulus are modelled probabilistically using Gaussian process (GP) emulation under the Bayesian framework. The corresponding performances are validated by individual prediction errors (IPE) diagnostics. The experimental results demonstrate that by adding certain types of steel skeleton into plain concrete, which gives a general better bonding property to concrete materials and increases the capacities of dynamic compressive strength, dynamic resistance and energy absorption

Defending against Sybil Devices in Crowdsourced Mapping Services

Real-time crowdsourced maps such as Waze provide timely updates on traffic, congestion, accidents and points of interest. In this paper, we demonstrate how lack of strong location authentication allows creation of software-based {\em Sybil devices} that expose crowdsourced map systems to a variety of security and privacy attacks. Our experiments show that a single Sybil device with limited resources can cause havoc on Waze, reporting false congestion and accidents and automatically rerouting user traffic. More importantly, we describe techniques to generate Sybil devices at scale, creating armies of virtual vehicles capable of remotely tracking precise movements for large user populations while avoiding detection. We propose a new approach to defend against Sybil devices based on {\em co-location edges}, authenticated records that attest to the one-time physical co-location of a pair of devices. Over time, co-location edges combine to form large {\em proximity graphs} that attest to physical interactions between devices, allowing scalable detection of virtual vehicles. We demonstrate the efficacy of this approach using large-scale simulations, and discuss how they can be used to dramatically reduce the impact of attacks against crowdsourced mapping services.Comment: Measure and integratio

Centrality, system size and energy dependences of charged-particle pseudo-rapidity distribution

Utilizing the three-fireball picture within the quark combination model, we study systematically the charged particle pseudorapidity distributions in both Au+Au and Cu+Cu collision systems as a function of collision centrality and energy, $\sqrt{s_{NN}}=$ 19.6, 62.4, 130 and 200 GeV, in full pseudorapidity range. We find that: (i)the contribution from leading particles to $dN_{ch}/d\eta$ distributions increases with the decrease of the collision centrality and energy respectively; (ii)the number of the leading particles is almost independent of the collision energy, but it does depend on the nucleon participants $N_{part}$; (iii)if Cu+Cu and Au+Au collisions at the same collision energy are selected to have the same $N_{part}$, the resulting of charged particle $dN/d\eta$ distributions are nearly identical, both in the mid-rapidity particle density and the width of the distribution. This is true for both 62.4 GeV and 200 GeV data. (iv)the limiting fragmentation phenomenon is reproduced. (iiv) we predict the total multiplicity and pseudorapidity distribution for the charged particles in Pb+Pb collisions at $\sqrt{s_{NN}}= 5.5$ TeV. Finally, we give a qualitative analysis of the $N_{ch}/$ and $dN_{ch}/d\eta/|_{\eta\approx0}$ as function of $\sqrt{s_{NN}}$ and $N_{part}$ from RHIC to LHC.Comment: 12 pages, 8 figure

Centrality dependence of pTp_{T} spectra for identified hadrons in Au+Au and Cu+Cu collisions at sNN=200\sqrt{s_{NN}}= 200 GeV

The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}= 200$ GeV is systematically studied in a quark combination model. The $\mathrm{{p}_{T}}$ spectra of $\pi^{\pm}$, $K^{\pm}$, $p(\bar{p})$ and $\Lambda(\bar{\Lambda})$ in different centrality bins and the nuclear modification factors ($R_{CP}$) for these hadrons are calculated. The centrality dependence of the average collective transverse velocity $$ for the hot and dense quark matter is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu collision system. The centrality dependence of $\mathrm{{p}_{T}}$ spectra and the $R_{CP}$ for $\pi^{0}$, $K_{s}^{0}$ and $\Lambda$ in Cu+Cu collisions at $\sqrt{s_{NN}}= 200$ GeV are well described. The results show that $<\beta (r)>$ is only a function of the number of participants $N_{part}$ and it is independent of the collision system.Comment: 7 pages, 6 figure

In-Plane Magnetic Anisotropy In RF Sputtered Fe-N Thin Films

We have fabricated Fe(N) thin films with varied N2 partial pressure and studied the microstructure, morphology, magnetic properties and resistivity by using X-ray diffraction, atomic force microscopy, transmission electron microscopy, vibrating-sample magnetometer and angle-resolved M-H hysteresis Loop tracer and standard four-point probe method. In the presence of low N2 partial pressure, Fe(N) films showed a basic bcc a-Fe structure with a preferred (110) texture. A variation of in-plane magnetic anisotropy of the Fe(N) films was observed with the changing of N component. The evolution of in-plane anisotropy in the films was attributed to the directional order mechanism. Nitrogen atoms play an important role in refining the a-Fe grains and inducing uniaxial anisotropy.Comment: 11 pages, 6 figure

Boundary K-matrices and the Lax pair for 1D open XYZ spin-chain

We analysis the symmetries of the reflection equation for open $XYZ$ model and find their solutions $K^{\pm}$ case by case. In the general open boundary conditions, the Lax pair for open one-dimensional $XYZ$ spin-chain is given.Comment: LaTeX, 17 pages, errors in references correcte