Hybrid mesons from anisotropic lattice QCD with the clover and improved gauge actions

We study hybrid mesons from the clover and improved gauge actions at $\beta=2.6$ on the anisotropic $12^3\times36$ lattice using our PC cluster. We estimate the mass of $1^{-+}$ light quark hybrid as well as the mass of the charmonium hybrid. The improvement of both quark and gluonic actions, first applied to the hybrid mesons, is shown to be more efficient in reducing the lattice spacing and finite volume errors.Comment: Lattice2002 (spectrum

Exotic mesons from quantum chromodynamics with improved gluon and quark actions on the anisotropic lattice

Hybrid (exotic) mesons, which are important predictions of quantum chromodynamics (QCD), are states of quarks and anti-quarks bound by excited gluons. First principle lattice study of such states would help us understand the role of ``dynamical'' color in low energy QCD and provide valuable information for experimental search for these new particles. In this paper, we apply both improved gluon and quark actions to the hybrid mesons, which might be much more efficient than the previous works in reducing lattice spacing error and finite volume effect. Quenched simulations were done at $\beta=2.6$ and on a $\xi=3$ anisotropic $12^3\times36$ lattice using our PC cluster. We obtain $2013 \pm 26 \pm 71$ MeV for the mass of the $1^{-+}$ hybrid meson ${\bar q}qg$ in the light quark sector, and $4369 \pm 37 \pm 99$Mev in the charm quark sector; the mass splitting between the $1^{-+}$ hybrid meson ${\bar c}c g$ in the charm quark sector and the spin averaged S-wave charmonium mass is estimated to be $1302 \pm 37 \pm 99$ MeV. As a byproduct, we obtain $1438 \pm 32 \pm 57$ MeV for the mass of a P-wave $1^{++}$ ${\bar u}u$ or ${\bar d}d$ meson and $1499 \pm 28 \pm 65$ MeV for the mass of a P-wave $1^{++}$ ${\bar s}s$ meson, which are comparable to their experimental value 1426 MeV for the $f_1(1420)$ meson. The first error is statistical, and the second one is systematical. The mixing of the hybrid meson with a four quark state is also discussed.Comment: 12 pages, 3 figures. Published versio

Infection Spreading and Source Identification: A Hide and Seek Game

The goal of an infection source node (e.g., a rumor or computer virus source) in a network is to spread its infection to as many nodes as possible, while remaining hidden from the network administrator. On the other hand, the network administrator aims to identify the source node based on knowledge of which nodes have been infected. We model the infection spreading and source identification problem as a strategic game, where the infection source and the network administrator are the two players. As the Jordan center estimator is a minimax source estimator that has been shown to be robust in recent works, we assume that the network administrator utilizes a source estimation strategy that can probe any nodes within a given radius of the Jordan center. Given any estimation strategy, we design a best-response infection strategy for the source. Given any infection strategy, we design a best-response estimation strategy for the network administrator. We derive conditions under which a Nash equilibrium of the strategic game exists. Simulations in both synthetic and real-world networks demonstrate that our proposed infection strategy infects more nodes while maintaining the same safety margin between the true source node and the Jordan center source estimator

Identifying Infection Sources and Regions in Large Networks

Identifying the infection sources in a network, including the index cases that introduce a contagious disease into a population network, the servers that inject a computer virus into a computer network, or the individuals who started a rumor in a social network, plays a critical role in limiting the damage caused by the infection through timely quarantine of the sources. We consider the problem of estimating the infection sources and the infection regions (subsets of nodes infected by each source) in a network, based only on knowledge of which nodes are infected and their connections, and when the number of sources is unknown a priori. We derive estimators for the infection sources and their infection regions based on approximations of the infection sequences count. We prove that if there are at most two infection sources in a geometric tree, our estimator identifies the true source or sources with probability going to one as the number of infected nodes increases. When there are more than two infection sources, and when the maximum possible number of infection sources is known, we propose an algorithm with quadratic complexity to estimate the actual number and identities of the infection sources. Simulations on various kinds of networks, including tree networks, small-world networks and real world power grid networks, and tests on two real data sets are provided to verify the performance of our estimators

One-Pot Synthesis of Chiral Organometallic Complexes

Currently, organometallic complexes involving ligand oxazolines are typically obtained in two sequential steps, where the free ligand is given firstly from a functionalized nitrile by condensation reaction with an amino alcohol in the presence of a Lewis or Bronsted acid catalyst, followed by a further coordination with metal salts to obtain the corresponding oxazolinyl metal complexes. Usually, the yield of the two-step procedure is relatively low; considering that metal oxazoline complexes often contain Lewis acidic metals, it is possible that the two steps may be telescoped. A series of novel chiral organometallic complexes (1–23) were assembled in a single step from nitriles, chiral D/L amino alcohols, and a stoichiometric amount of metal salts (MCl2·nH2O/M(OAc)2·nH2O), with moderate to high yields (20–95%). All the crystalline compounds were fully characterized by NMR, IR, MS, and X-ray analyses

Reforming Curriculum in A Centralized System: An Examination of the Relationships between Teacher Implementation of Student-Centered Pedagogy and High Stakes Teacher Evaluation Policies in China

Past research has shown poor implementation levels of a classroom-level curriculum strategy that forms the centerpiece of China's new national education reform policies, namely, Student-Centered Pedagogy (SCP). This dissertation set out to investigate the influences of selected school and teacher background characteristics, classroom-level SCP implementation variables, and a high stakes teacher evaluation policy variable, on SCP implementation levels reported by high school teachers in a selected school district in China. The overall aim of the research was to study relationships among a number of factors hypothesized to affect teachers' SCP implementation levels, guided by a theoretically-grounded, conceptual framework. The study particularly examined the potential adverse influence of an output-driven teacher evaluation policy on SCP implementation levels. The teacher evaluation policy is tied to secondary school students' performance on the high stakes, national college entrance examination in China, the Gaokao. Eight contextual and reform-related factors derived from a review of literature were tied together in the conceptual framework suggesting direct, mediating and moderating influences on SCP implementation. Based on the framework, paths by which the variables could affect SCP implementation levels directly or indirectly, were tested in stages. Data were collected and analyzed using survey research methodology. The first part of the analyses involved the design and validation of a bilingual teacher survey (English and Chinese), tapping the key variables. The second part of the analyses involved a series of hierarchical regression models to test hypothesized pathways and relationships among the measured variables. The theoretical premise of the study was that the large size and highly centralized structure of the Chinese educational system led it to adopt an output-control mechanism in the form of the high-stakes teacher evaluation policy tied to student performance on Gaokao. The adoption of such an output-control mechanism resulted in a mismatch between the philosophy underlying the newer SCP reforms and the pre-existing teacher evaluation policy, which in turn led to poor implementation levels of SCP in classrooms by teachers. Previously, researchers in China have overlooked the importance of policy incompatibility issues in examining effects of reforms at the classroom level. The study found that, consistent with the literature, teacher beliefs in SCP and teacher self-efficacy in practicing SCP had consistently positive, statistically significant influences on SCP implementation (for Beliefs in SCP, t(224)=3.745, p=.000, standardized β=. 22; for Self Efficacy, t(224)=3.387, p=.001, standardized β=.23). Also consistent with expectations, the influence of the survey measure tapping perceived control by the output-driven teacher evaluation policy on SCP implementation, was negative and statistically significant ( t(224)= -1.982, p=.049; standardized β=-.12). Perceived support for SCP implementation, including resources, professional development programs, support from principals and colleagues was a statistically significant predictor in initial models, but the factor was found to lose statistical significance when combined with the variable tapping perceived control by the output-driven teacher evaluation policy. With all the specified independent and mediating variables in the regression model, the cumulative variance explained on SCP Implementation levels was 20% ( = .199). The overall model was statistically significant (F[7,224)=7.935, p=.000). Together, these results confirmed the main hypotheses of the study

Lifshitz holographic superconductor in Horava-Lifshitz gravity

We study the holographic phase transition of superconductor dual to a Lifshitz black brane probed by an anisotropic scalar field in the probe limit in Ho\u{r}ava-Lifshitz gravity. With the use of numerical and analytical method, we investigate how the critical temperature of the condensation is affected by the Lifshitz exponent $z$, $\alpha-$correction term in the action as well as the dimensions of the gravity. We also numerically explore the condensation of the dual operator and optical conductivity of the holographic system. Various interesting properties of the holographic condensation affected by the parameters of model are discussed