Lagrangian approach to local symmetries and self-dual model in gauge invariant formulation

Taking the St\"uckelberg Lagrangian associated with the abelian self-dual model of P.K. Townsend et al as a starting point, we embed this mixed first- and second-class system into a pure first-class system by following systematically the generalized Hamiltonian approach of Batalin, Fradkin and Tyutin. The resulting Lagrangian possesses an extended gauge invariance and provides a non-trivial example for a general Lagrangian approach to unravelling the full set of local symmetries of a Lagrangian.Comment: LaTeX, 15 page

BRST cohomology and vacuum structure of two-dimensional chromodynamics

Using a formulation of QCD_2 as a perturbed conformally invariant theory involving fermions, ghosts, as well as positive and negative level Wess-Zumino-Witten fields, we show that the BRST conditions become restrictions on the conformally invariant sector, as described by a G/G topological theory. By solving the corresponding cohomology problem we are led to a finite set of vacua. For G=SU(2) these vacua are two-fold degenerate

The Text Classification Research of Chinese Technology Text

随着人们对科学技术和社会发展的日益重视，学术领域呈现多元化、信息化、现代化的趋势。在这种情况下，研究者们比以往任何时候都迫切地需要高效、全面、方便的学术信息。因此，中文科技论文文本分类研究具有较高的理论研究价值和应用前景。本文针对中文科技论文文本特殊的文体格式和语言风格进行了系统地研究。全文主要从预处理、特征提取和分类算法三大部分展开，重点研究了基于自然语言处理的特征提取和基于层次分类模型的分类算法。预处理方面，本文分为两个步骤：科技论文文本数据预处理和中文分词处理。特征提取方面，分为文本特征表示和文本特征优化，而重点放在文本特征表示这一部分。在自然语言处理方面，主要建立了基于自然语言处理的特...With increasingly recognition of technology and society development, science domain is oriented to pluralistic and modern trend. In this case, the researcher need the high-effect, complete and convenient science information more urgently than ever. In the conformance of age request, Chinese technology text classification research takes on the high theoretical value and applied foreground. Thi...学位：工学硕士院系专业：信息科学与技术学院自动化系_系统工程学号：20033101

Gauge Identities and the Dirac Conjecture

The gauge symmetries of a general dynamical system can be systematically obtained following either a Hamiltonean or a Lagrangean approach. In the former case, these symmetries are generated, according to Dirac's conjecture, by the first class constraints. In the latter approach such local symmetries are reflected in the existence of so called gauge identities. The connection between the two becomes apparent, if one works with a first order Lagrangean formulation. Our analysis applies to purely first class systems. We show that Dirac's conjecture applies to first class constraints which are generated in a particular iterative way, regardless of the possible existence of bifurcations or multiple zeroes of these constraints. We illustrate these statements in terms of several examples.Comment: 21 page

Massive two-dimensional quantum chromodynamics

Quantum Chromodynamics in the decoupled formulation. We find that some general features of the massless theory, concerning the constraints and the right- and left-moving character of the corresponding BRST currents, survive in the massive case. The implications for the integrability properties previously valid in the massless case, and the structure of the Hilbert space are discussed