Estimating the mass of the hidden charm 1+(1+)1^+(1^{+}) tetraquark state via QCD sum rules

By using QCD sum rules, the mass of the hidden charm tetraquark $[cu][\bar{c}\bar{d}]$ state with $I^{G} (J^{P}) = 1^+ (1^{+})$ (HCTV) is estimated, which presumably will turn out to be the newly observed charmonium-like resonance $Z_c^+(3900)$. In the calculation, contributions up to dimension eight in the operator product expansion(OPE) are taken into account. We find $m_{1^+}^c = (3912^{+306}_{-153}) \, \text{MeV}$, which is consistent, within the errors, with the experimental observation of $Z_c^+(3900)$. Extending to the b-quark sector, $m_{1^+}^b = (10561^{+395}_{-163}) \,\text{MeV}$ is obtained. The calculational result strongly supports the tetraquark picture for the "exotic" states of $Z_c^+(3900)$ and $Z_b^+(10610)$.Comment: 13 pages,3 figures, 1 table, version to appear in EPJ

Mass Spectra of 0+−0^{+-}, 1−+1^{-+}, and 2+−2^{+-} Exotic Glueballs

With appropriate interpolating currents the mass spectra of $0^{+-}$, $1^{-+}$, and $2^{+-}$ oddballs are studied in the framework of QCD sum rules (QCDSR). We find there exits one stable $0^{+-}$ oddball with mass of $4.57 \pm 0.13 \, \text{GeV}$, and one stable $2^{+-}$ oddball with mass of $6.06 \pm 0.13 \, \text{GeV}$, whereas, no stable $1^{-+}$ oddball shows up. The possible production and decay modes of these glueballs with unconventional quantum numbers are analyzed, which are hopefully measurable in either BELLEII, PANDA, Super-B or LHCb experiments.Comment: 10 pages, 12 figures, 4 tables, to appear in NPB. arXiv admin note: substantial text overlap with arXiv:1408.399

Interpretation of Zc(4025)Z_c(4025) as the Hidden Charm Tetraquark States via QCD Sum Rules

By using QCD Sum Rules, we found that the charged hidden charm tetraquark $[c u][\bar{c} \bar{d}]$ states with $J^P = 1^-$ and $2^+$, which are possible quantum numbers of the newly observed charmonium-like resonance $Z_c(4025)$, have masses of $m_{1^-}^c = (4.54 \pm 0.20) \, \text{GeV}$ and $m_{2^+}^c = (4.04 \pm 0.19) \, \text{GeV}$. The contributions up to dimension eight in the Operator Product Expansion (OPE) were taken into account in the calculation. The tetraquark mass of $J^{P} = 2^{+}$ state was consistent with the experimental data of $Z_c(4025)$, suggesting the $Z_c(4025)$ state possessing the quantum number of $J^P = 2^+$. Extending to the b-quark sector, the corresponding tetraquark masses $m_{1^-}^b = (10.97 \pm 0.25) \, \text{GeV}$ and $m_{2^+}^b = (10.35 \pm 0.25) \, \text{GeV}$ were obtained, which are testable in future B-factories.Comment: 15 pages, 6 figures, to appear in European Physical Journal

Singular Value Computation and Subspace Clustering

In this dissertation we discuss two problems. In the first part, we consider the problem of computing a few extreme eigenvalues of a symmetric definite generalized eigenvalue problem or a few extreme singular values of a large and sparse matrix. The standard method of choice of computing a few extreme eigenvalues of a large symmetric matrix is the Lanczos or the implicitly restarted Lanczos method. These methods usually employ a shift-and-invert transformation to accelerate the speed of convergence, which is not practical for truly large problems. With this in mind, Golub and Ye proposes an inverse-free preconditioned Krylov subspace method, which uses preconditioning instead of shift-and-invert to accelerate the convergence. To compute several eigenvalues, Wielandt is used in a straightforward manner. However, the Wielandt deflation alters the structure of the problem and may cause some difficulties in certain applications such as the singular value computations. So we first propose to consider a deflation by restriction method for the inverse-free Krylov subspace method. We generalize the original convergence theory for the inverse-free preconditioned Krylov subspace method to justify this deflation scheme. We next extend the inverse-free Krylov subspace method with deflation by restriction to the singular value problem. We consider preconditioning based on robust incomplete factorization to accelerate the convergence. Numerical examples are provided to demonstrate efficiency and robustness of the new algorithm. In the second part of this thesis, we consider the so-called subspace clustering problem, which aims for extracting a multi-subspace structure from a collection of points lying in a high-dimensional space. Recently, methods based on self expressiveness property (SEP) such as Sparse Subspace Clustering and Low Rank Representations have been shown to enjoy superior performances than other methods. However, methods with SEP may result in representations that are not amenable to clustering through graph partitioning. We propose a method where the points are expressed in terms of an orthonormal basis. The orthonormal basis is optimally chosen in the sense that the representation of all points is sparsest. Numerical results are given to illustrate the effectiveness and efficiency of this method

Performance, preference, promotion: political mobility of Chinese regional leaders

As a study exclusively on the political elites, the dissertation studies the Chinese regional leaders and their political career mobility controlled by the central government from 1949 to 2010. The Chinese Communist Party controls its regional leaders by controlling their career movement (political mobility). This study explains why some regional leaders were promoted while some others were demoted or dismissed while most of them shared similar personal background and career experience. By providing empirical evidence with quantitative analysis, this study shows that in post-Deng Chinese politics (1997-2010) there are certain patterns and manipulated by the CCP center in demoting and dismissing its regional leaders in order to improve the party’s overall ruling legitimacy. Many China watchers have ignored the fact that socioeconomic development among different Chinese regions is highly uneven yet has the government found any efficient solution. The conflicts of interests between a regional government and the central government of China may have caused different economic outcomes. Meanwhile, the political importance of a region in China can be evaluated through the center’s fiscal indicators. Last but not least, sustainable economic growth and regional governments’ financial conditions are among the decisive factors that determine regional leaders’ political mobility in the future under the party-state political system

Transmission Dynamics of Avian Influenza Among Poultry With and Without Vaccination

The continuing avian influenza (AI) out break that began in late 2003 and early 2004 has been disastrous for the poultry industry worldwide. It has resulted in severe socio-economic damage, and it has raised serious concerns for general public health. In this research, we use mathematics to analyze transmission dynamics of AI among poultry. We use a status-based approach to construct systems of differential equations to describe virus transmission dynamics. We develop theoretical means to eradicate the spread of the disease, and we calculate the size of healthy and infected populations during an AI outbreak, and the final population size when the disease is eliminated. We study the dynamics when vaccination is absent, and when vaccination is used. For the latter case, we investigate different scenarios, including when the circulating virus consists of only one strain, and when multiple strains are present. Finally, we assume there exists a mutation which can create a non-existing strain from an existing strain and we analyze such dynamics using numerical simulation. The measures and information provided by this research can be used as references to develop disease control strategies