11,176 research outputs found
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
on the anisotropic lattice using our PC cluster. We
estimate the mass of 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
and on a anisotropic lattice using our PC cluster. We
obtain MeV for the mass of the hybrid meson
in the light quark sector, and Mev in the
charm quark sector; the mass splitting between the hybrid meson in the charm quark sector and the spin averaged S-wave charmonium mass
is estimated to be MeV. As a byproduct, we obtain MeV for the mass of a P-wave or
meson and MeV for the mass of a P-wave meson, which are comparable to their experimental value 1426 MeV for the
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
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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 , 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
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