N=(0, 2) Deformation of (2, 2) Sigma Models: Geometric Structure, Holomorphic Anomaly and Exact Beta Functions

We study N=(0,2) deformed (2,2) two-dimensional sigma models. Such heterotic models were discovered previously on the world sheet of non-Abelian strings supported by certain four-dimensional N=1 theories. We study geometric aspects and holomorphic properties of these models, and derive a number of exact expressions for the beta functions in terms of the anomalous dimensions analogous to the NSVZ beta function in four-dimensional Yang-Mills. Instanton calculus provides a straightforward method for the derivation. The anomalous dimensions are calculated up to two loops implying that one of the beta functions is explicitly known up to three loops. The fixed point in the ratio of the couplings found previously at one loop is not shifted at two loops. We also consider the N=(0,2) supercurrent supermultiplet (the so-called hypercurrent) and its anomalies, as well as the "Konishi anomaly." This gives us another method for finding exact $\beta$ functions. We prove that despite the chiral nature of the models under consideration quantum loops preserve isometries of the target space.Comment: 38 pages, 6 figures, minor changes in the text and references, the journal versio

Evaluating Value at Risk Models at Canadian Commercial Banks

This research paper analyzes the internal Value-at-Risk (VAR) models of the “Big Five” Canadian commercial banks by empirically investigating the banks‟ actual non-anonymous daily VAR and profit-and-loss (P&L) data. These data points were extracted from graphs included in the banks‟ own annual report, Out of the 4340 trading days analyzed in this study, there are 47 exceptions (days when the actual loss exceeds the disclosed VAR); whereas, the expected figure is 43 exceptions at a 99% confidence interval. During a financial crisis, as is the case for the study‟s time line, this internal VAR model demonstrates an inconsistent result among our sample banks. For example, the number of exceptions was found to be significantly variable between banks, with two banks, BMO and RBC, experiencing 26 and 16 exceptions respectively, while BNS and TD only have one day with a loss exceeding the VAR. We doubt whether the internal model precisely evaluate VAR, so we conduct alternative method such as Historical simulation model and GARCH(1,1) model to calculate the banks‟ VAR, we conclude Historical simulation model is best among those models based on the test results

Evaluating Government Portal Websites in China

Government portal websites are the core components of e-Government because it is a platform integrating different government resources. This article was devoted to study the government portal websites in China in order to disclose the development status of e-Government in China. In order to do this, two questions are answered: from which aspects should government portal websites be evaluated; how to develop the indexes for different aspects of government portal website evaluation. In our solution, we aligned the evaluation of government portal website with new public administration principles so that government can provide better services to the users because new focuses of public administration bring new strategies for e-Government. The proposed framework emphasizes content, function, and construction of government portals. The validation analysis showed that the proposed evaluation framework is well fitted. 30 major cities’ government portal websites in China are evaluated. The results suggested China has implemented advanced e-Government services such as e-democracy but the performance of those services is not appreciated by the user very well