Classical and Quantum Gravity in 1+1 Dimensions, Part I: A Unifying Approach

We provide a concise approach to generalized dilaton theories with and without torsion and coupling to Yang-Mills fields. Transformations on the space of fields are used to trivialize the field equations locally. In this way their solution becomes accessible within a few lines of calculation only. In this first of a series of papers we set the stage for a thorough global investigation of classical and quantum aspects of more or less all available 2D gravity-Yang-Mills models.Comment: 24 pages, no figures, some sign errors in Eqs. 52--59 have been corrected (according to the Erratum

Efficiency Analysis of German Electricity Distribution Utilities : Non-Parametric and Parametric Tests

This paper applies parametric and non-parametric and parametric tests to assess the efficiency of electricity distribution companies in Germany. We address traditional issues in electricity sector benchmarking, such as the role of scale effects and optimal utility size, as well as new evidence specific to the situation in Germany This paper applies parametric and non-parametric and parametric tests to asses the efficiency of electricity distribution companies in Germany. We use labor, capital, and peak load capacity as inputs, and units sold and the number of customers as output. The data covers 307 (out of 553) German electricity distribution utilities. We apply a data envelopment analysis (DEA) with constant returns to scale (CRS) as the main productivity analysis technique, whereas stochastic frontier analysis (SFA) with distance function is our verification method. The results suggest that returns to scale play a minor role; only very small utilities have a significant cost advantage. Low customer density is found to affect the efficiency score significantly in the lower third of all observations. Surprisingly, East German utilities feature a higher average efficiency than their West German counterparts. The correlation tests imply a high coherence of the results. --Efficiency analysis,econometric methods,electricity distribution,benchmarking,Germany

Nonperturbative path integral of 2d dilaton gravity and two-loop effects from scalar matter

Performing an nonperturbative path integral for the geometric part of a large class of 2d theories without kinetic term for the dilaton field, the quantum effects from scalar matter fields are treated as a perturbation. When integrated out to two-loops they yield a correction to the Polyakov term which is still exact in the geometric part. Interestingly enough the effective action only experiences a renormalization of the dilaton potential.Comment: 15 page

CVaR minimization by the SRA algorithm

Using the risk measure CV aR in �nancial analysis has become more and more popular recently. In this paper we apply CV aR for portfolio optimization. The problem is formulated as a two-stage stochastic programming model, and the SRA algorithm, a recently developed heuristic algorithm, is applied for minimizing CV aR

Modelling generalized firms' restructuring using inverse DEA

The key consideration for firms’ restructuring is improving their operational efficiencies. Market conditions often offer opportunities or generate threats that can be handled by restructuring scenarios through consolidation, to create synergy, or through split, to create reverse synergy. A generalized restructuring refers to a move in a business market where a homogeneous set of firms, a set of pre-restructuring decision making units (DMUs), proceed with a restructuring to produce a new set of post-restructuring entities in the same market to realize efficiency targets. This paper aims to develop a novel inverse Data Envelopment Analysis based methodology, called GInvDEA (Generalized Inverse DEA), for modeling the generalized restructuring. Moreover, the paper suggests a linear programming model that allows determining the lowest performance levels, measured by efficiency that can be achieved through a given generalized restructuring. An application in banking operations illustrates the theory developed in the paper

Long Run Properties of Technical Efficiency in the U.S. Airline Industry

This paper takes an innovative approach to test the relationship between technical efficiency and the market structure hypothesis which states that competitive pressure enhances relative efficiency. DEA and FDH time series of technical efficiency scores, for a panel of 11 US airlines observed quarterly during 1970-1990, are examined for cointegration and convergence. For almost all firm pairs (>90% for both efficiency measures), the null hypothesis of cointegration cannot be rejected; meanwhile, the null of no cointegration is rejected for approximately one-third of the firm pairs. Furthermore, convergence tests document less dispersion in firm performance over time. These results indicate that the scores move together and, in fact, the firms are becoming more alike one another in terms of efficiency. ZUSAMMENFASSUNG - (Langfristige Eigenschaften der technischen Effizienz in der US-Luftfahrtindustrie) In diesem Beitrag wird ein innovativer Ansatz entwickelt, um die Beziehung zwischen technischer Effizienz und der Marktstrukturhypothese zu überprüfen, die besagt, daß Wettbewerbsdruck die relative Effizienz erhöht. Die DEA- und FDH-Zeitreihen der technischen Effizienz für ein Panel-Datensatz von 11 US-Fluggesellschaften, die während der Periode 1970 bis 1990 beobachtet wurden, werden im Hinblick auf Kointegration und Konvergenz analysiert. Für nahezu alle Unternehmenspaare (mehr als 90% bei beiden Effizienzmaßen) kann die Nullhypothese der Kointegration nicht zurückgewiesen werden, wo hingegen die Nullhypothese, daß keine Kointegration vorliegt, für etwa ein Drittel der Unternehmenspaare zurückgewiesen wird. Außerdem zeigt der Konvergenztest, daß die Streuung des Unternehmenserfolgs im Zeitablauf abnimmt. Die Ergebnisse deuten darauf hin, daß die Effizienzwerte sich auf einander zu bewegen und daß in der Tat, die Unternehmen im Hinblick auf Effizienz sich immer ähnlicher werden.