Higher moment singularities explored by the net proton non-statistical fluctuations

We use the non-statistical fluctuation instead of the full one to explore the higher moment singularities of net proton event distributions in the relativistic Au+Au collisions at $\sqrt{s_{NN}}$ from 11.5 to 200 GeV calculated by the parton and hadron cascade model PACIAE. The PACIAE results of mean ($M$), variance ($\sigma^2$), skewness ($S$), and kurtosis ($\kappa$) are consistent with the corresponding STAR data. Non-statistical moments are calculated as the difference between the moments derived from real events and the ones from mixed events, which are constructed by combining particles randomly selected from different real events. An evidence of singularity at $\sqrt{s_{NN}}\sim$ 60 GeV is first seen in the energy dependent non-statistical $S$ and $S\sigma$.Comment: 5 pages,5 figure

Topological Gauge Structure and Phase Diagram for Weakly Doped Antiferromagnets

We show that the topological gauge structure in the phase string theory of the {\rm t-J} model gives rise to a global phase diagram of antiferromagnetic (AF) and superconducting (SC) phases in a weakly doped regime. Dual confinement and deconfinement of holons and spinons play essential roles here, with a quantum critical point at a doping concentration $x_c\simeq 0.043$. The complex experimental phase diagram at low doping is well described within such a framework.Comment: 4 pages, 2 figures, modified version, to appear in Phys. Rev. Let

Interatomic potentials for the vibrational properties of III-V semiconductor nanostructures

We derive interatomic potentials for zinc blende InAs, InP, GaAs and GaP semiconductors with possible applications in the realm of nanostructures. The potentials include bond stretching interaction between the nearest and next-nearest neighbors, a three body term and a long-range Coulomb interaction. The optimized potential parameters are obtained by (i) fitting to bulk phonon dispersions and elastic properties and (ii) constraining the parameter space to deliver well behaved potentials for the structural relaxation and vibrational properties of nanostructure clusters. The targets are thereby calculated by density functional theory for clusters of up to 633 atoms. We illustrate the new capability by the calculation Kleinman and Gr\"uneisen parameters and of the vibrational properties of nanostructures with 3 to 5.5 nm diameter.Comment: 22 pages, 5 figures; Phys. Rev. B 201

Micro mechanics of isotropic normal compression

Discrete element modelling has been used to investigate the micro mechanics of isotropic normal compression. One-dimensional (1D) normal compression has previously been modelled in three dimensions using an oedometer and a large number of particles and without the use of agglomerates, and it was shown that the compression index was solely related to the strengths of the particles as a function of size. The same procedure is used here to model isotropic normal compression. The fracture of a particle is governed by the octahedral shear stress within the particle (due to the multiple contacts) and a Weibull distribution of strengths. The octahedral shear stresses, due to local anisotropic stresses within a sample with isotropic boundary stresses, are shown to give rise to a normal compression line (NCL) and the evolution of a distribution of particle sizes. The compression line is parallel to the 1D NCL in log e–log p space, in agreement with traditional critical state soil mechanics and confirming that the compression index is solely a function of the size effect on average particle strength, which determines the hardening law for the material. The paper shows, for the first time, how local octahedral shear stresses induced in the particles within the sample generate an isotropic normal (clastic) compression line

CCD Positions of Saturn and its Major Satellites from 2002-2006

International audienceThis paper presents 2154 precise positions of Saturn and its major satellites from 359 CCD exposures taken with the 1 m telescope at the Yunnan Observatory during the years 2002-2006. It also describes the improved image-processing techniques for the pixel positional measurement of Saturn's rings and its major satellites, especially for Mimas and Enceladus. The four bright satellites S3-S6 (i.e., Tethys, Dione, Rhea, and Titan) of Saturn are used to calibrate the CCD field of view by comparing their pixel positions with their theoretical ones from the theory TASS1.7. The observational positions of these major satellites, when measured with respect to Rhea, usually have a good agreement with their theoretical ones except for Mimas, which has the biggest systematic difference of about -0.3 arcsec in R.A. in its 2002 observational data sets. However, these differences of Mimas become much smaller when the recent Jet Propulsion Laboratory ephemeris is replaced. The rms errors in each coordinate are about 40 mas for Saturn and its bright satellites S2-S6, and 90 mas for Mimas. These positional observations are comparable to the best ground-based CCD observations

Mutual-Chern-Simons effective theory of doped antiferromagnets

A mutual-Chern-Simons Lagrangian is derived as a minimal field theory description of the phase-string model for doped antiferromagnets. Such an effective Lagrangian is shown to retain the full symmetries of parity, time-reversal, and global SU(2) spin rotation, in contrast to conventional Chern-Simons theories where first two symmetries are usually broken. Two ordered phases, i.e., antiferromagnetic and superconducting states, are found at low temperatures as characterized by dual Meissner effects and dual flux quantization conditions due to the mutual-Chern-Simons gauge structure. A dual confinement in charge/spin degrees of freedom occurs such that no true spin-charge separation is present in these ordered phases, but the spin-charge separation/deconfinement serves as a driving force in the unconventional phase transitions of these ordered states to disordered states.Comment: 16 pages, 2 figures; published versio