An improved algorithm based on finite difference schemes for fractional boundary value problems with non-smooth solution

In this paper, an efficient algorithm is presented by the extrapolation technique to improve the accuracy of finite difference schemes for solving the fractional boundary value problems with non-smooth solution. Two popular finite difference schemes, the weighted shifted Gr\"{u}nwald difference (WSGD) scheme and the fractional centered difference (FCD) scheme, are revisited and the error estimate of the schemes is provided in maximum norm. Based on the analysis of leading singularity of exact solution for the underlying problem, it is demonstrated that, with the use of the proposed algorithm, the improved WSGD and FCD schemes can recover the second-order accuracy for non-smooth solution. Several numerical examples are given to validate our theoretical prediction. It is shown that both accuracy and convergence rate of numerical solutions can be significantly improved by using the proposed algorithm.Comment: the Riesz fractional derivatives, extrapolation technique, error estimate in maximum norm, weak singularity, convergence rat

Quantum Critical Point in Strongly Correlated 87^{87}Rb Atoms in Optical Lattice

In this paper, the Bosonic projected variational method is proposed to study the strongly correlated $^{87}{\rm Rb}$ atoms in optical lattice. A global phase diagram is obtained by this method. There exist two characteristic lattice depths $V$ for $^{87}{\rm Rb}$ atoms in optical lattice : one is $V=9.5E_r$ to label the maximum height of the 'zero-momentum' peak of condensation, the other is the quantum critical point for the superfluid-insulator (SI) transition at $V=12.3E_r$. As a result of strongly correlated effect for lattice Bosons, the suppressed superfluid state is predicted near the SI transition with the suppressed superfluid density and the very slowly velocity of the sound-like excitons

Giant radio galaxies as probes of the ambient WHIM in the era of the SKA

The missing baryons are usually thought to reside in galaxy filaments as warm-hot intergalactic medium (WHIM). From previous studies, giant radio galaxies are usually associated with galaxy groups, which normally trace the WHIM. We propose observations with the powerful SKA1 to make a census of giant radio galaxies in the southern hemisphere, which will probe the ambient WHIM. The radio galaxies discovered will also be investigated to search for dying radio sources. With the highly improved sensitivity and resolution of SKA1, more than 6,000 giant radio sources will be discovered within 250 hours.Comment: 8 pages, 3 figures; to appear as part of 'Cosmic Magnetism' in Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14

Star formation properties of galaxy cluster A1767

Abell 1767 is a dynamically relaxed, cD cluster of galaxies with a redshift of 0.0703. Among 250 spectroscopically confirmed member galaxies within a projected radius of 2.5r_{200}, 243 galaxies (~ 97%) are spectroscopically covered by the Sloan Digital Sky Survey (SDSS). Based on this homogeneous spectral sample, the stellar evolutionary synthesis code, STARLIGHT, is applied to investigate the stellar populations and star formation histories (SFHs) of cluster galaxies. The star formation properties of galaxies, such as mean stellar ages, metallicities, stellar masses, and star formation rates (SFRs), are presented as the functions of local galaxy density. Strong environmental effect is found in the manner that massive galaxies in the high-density core region of cluster tend to have higher metallicities, longer mean stellar ages, and lower specific star formation rates (SSFRs), and their recent star formation activities have been remarkably suppressed. In addition, the correlations of the metallicity and SSFR with stellar mass are confirmed.Comment: 11 pages, 8 figures, accepted by RA

Ghd8 controls rice photoperiod sensitivity by forming a complex that interacts with Ghd7.

BackgroundFlowering time is one of the most important agronomic characteristics that ultimately determine yield potential and eco-geographical adaptation in crops. Ghd8 and Ghd7, two major flowering genes, have similar functions and large pleiotropic effects in controlling the heading date, plant height and grain yield of rice. However, these gene interactions at the genetic and molecular levels have not been determined to date.ResultsIn this study, we investigated the genetic interaction between Ghd8 and Ghd7 by using a set of near-isogenic lines and a panel of natural germplasm accessions in rice. We found that Ghd8 affected multiple agronomic traits in a functional Ghd7-dependent manner. Both functional Ghd8 and Ghd7 are pivotal for rice photoperiod sensitivity controlled by Hd1 and Hd3a. GHD8 could form a heterotrimeric complex with HD1 and OsHAP5b to activate the transcription of Ghd7 by binding directly to the promoter region of Ghd7, which contains the CCAAT-box motif.ConclusionsThe results of this study help to elucidate the genetic and molecular bases of Ghd8 and Ghd7 interactions, indicating that Ghd8 acts upstream of Ghd7 to activate its transcription, which inhibits Hd3a expression and thus affects flowering time and rice adaptation

A lightweight forum-based distributed requirement elicitation process for open source community

Nowadays, lots of open source communities adopt forum to acquire scattered stakeholders' requirements. But the requirements collection process always suffers from the unformatted description and unfocused discussions. In this paper, we establish a framework ReqForum to define the metamodel of the requirement elicitation forum. Based on it, we propose a lightweight forum-based requirements elicitation process which includes six steps: template-based requirements creation, opinions collection, requirements collection, requirements management, capability identification and the incentive mechanism. According to the proposed process, the prototype SKLSEForum is established by composing the Discuz and its existed pulg-ins. The implementation indicates that the process is feasible and the cost is economic

Correlation Effects in Quadrupole Insulators: a Quantum Monte Carlo Study

The quadrupole insulator, a high-order topological insulator, with on-site Hubbard interaction is numerically studied by large-scale projector quantum Monte Carlo (PQMC) simulations. The Green's function formalism is successfully used to characterize topological properties in interacting quadrupole insulators for the first time. We find that the topological quadrupole insulator is stable against weak interactions and turns into a trivial antiferromagnetic (AFM) insulator by a continuous topological phase transition (TPT) for strong interactions. The critical exponents related to the TPT are estimated to be $\nu=0.67(4)$, $\beta=0.40(2)$, which are distinct from those of the known AFM transitions and suggest a new universality class.Comment: 5+3 pages, 6+2 figure

Time Dependence of Holographic Complexity in Gauss-Bonnet Gravity

We study the effect of the Gauss-Bonnet term on the complexity growth rate of dual field theory using the "Complexity--Volume" (CV) and CV2.0 conjectures. We investigate the late time value and full time evolution of the complexity growth rate of the Gauss-Bonnet black holes with horizons with zero curvature ($k=0$), positive curvature ($k=1$) and negative curvature ($k=-1$) respectively. For the $k=0$ and $k=1$ cases we find that the Gauss-Bonnet term suppresses the growth rate as expected, while in the $k=-1$ case the effect of the Gauss-Bonnet term may be opposite to what is expected. The reason for it is briefly discussed, and the comparison of our results to the result obtained by using the "Complexity--Action" (CA) conjecture is also presented. We also briefly investigate two proposals applying some generalized volume functionals dual to the complexity in higher curvature gravity theories, and find their behaviors are different for $k=0$ at late times.Comment: 18 pages, 20 figures, 1 table, A new section (section V) and some reference added in the third versio

Complexity Growth for AdS Black Holes

Recently a Complexity-Action (CA) duality conjecture has been proposed, which relates the quantum complexity of a holographic boundary state to the action of a Wheeler-DeWitt (WDW) patch in the anti-de Sitter (AdS) bulk. In this paper we further investigate the duality conjecture for stationary AdS black holes and derive some exact results for the growth rate of action within the Wheeler-DeWitt (WDW) patch at late time approximation, which is supposed to be dual to the growth rate of quantum complexity of holographic state. Based on the results from the general $D$-dimensional Reissner-Nordstr\"{o}m (RN)-AdS black hole, rotating/charged Ba\~{n}ados-Teitelboim-Zanelli (BTZ) black hole, Kerr-AdS black hole and charged Gauss-Bonnet-AdS black hole, we present a universal formula for the action growth expressed in terms of some thermodynamical quantities associated with the outer and inner horizons of the AdS black holes. And we leave the conjecture unchanged that the stationary AdS black hole in Einstein gravity is the fastest computer in nature.Comment: v1, 10 pages, 2 figures, two columns; v2, 20 pages, 2 figures, JHEP style, references added; v3, 23 pages, 2 figures, discussions extended and references added, to be published in JHEP with title "Action Growth for AdS Black Holes

Mechanical feedback from black hole accretion as an energy source of core-collapse supernova explosions

According to the traditional scenario for core-collapse supernovae, the core of the collapsing star forms a neutron star and its gravitational energy release sends out a shockwave into the stellar envelope. However, in a significant number of numerical simulations, the shock stalls and the star cannot be exploded successfully, especially for a massive, compact star. We consider an alternative scenario that with mass fallback, the collapsing star forms a black hole in the center, surrounded by a dense, hot accretion disk, which blows out an intense outflow (wind). The kinetic energy of the wind may result in a successful stellar explosion. With an improved version of the formulism in Kohri et al. (2005) who studied neutron star accretion of minor fallback, we study this disk wind-driven explosion by calculating the accretion history for a suite of pre-SN stellar models with different initial surface rotational velocities, masses and metallicities, and by comparing the disk wind energy with the binding energy of the infalling stellar envelope. We show that the most promising models to be exploded successfully by this new channel are those relatively compact pre-SN stars with relatively low metallicities and not too low specific angular momenta. The total energies of the explosions are $\sim 10^{51-52}$ergs, and a more massive progenitor may produce a more energetic explosion.Comment: 11 pages, 8 figures, 3 tables, the Astrophysical Journal accepte