Harmonic Manifolds and Tubes

The authors showed in a preceding paper that in a connected locally harmonic manifold, the volume of a tube of small radius about a regularly parameterized simple arc depends only on the length of the arc and the radius. In this paper, we show that this property characterizes harmonic manifolds even if it is assumed only for tubes about geodesic segments. As a consequence, we obtain similar characterizations of harmonic manifolds in terms of the total mean curvature and the total scalar curvature of tubular hypersurfaces about curves. We find simple formulae expressing the volume, total mean curvature, and total scalar curvature of tubular hypersurfaces about a curve in a harmonic manifold as a function of the volume density function.Comment: 14 pages, grant numbers are update

A földrajzi közelség szerepe az innovációs együttműködésekben – illúzió vagy valós tényező?

Az innovációs együttműködés létrejöttében régóta sokat vizsgált szerepet játszik a földrajzi közelség. Az utóbbi évtizedben azonban az empirikus vizsgálatokban megjelentek a közelség más dimenziói is, mint például a társadalmi, kognitív, szervezeti vagy intézményi közelség. Valóban van a térbeliségnek abban szerepe, hogy létrejöjjön két szereplő között a kapcsolat? Vagy a kis földrajzi távolság (közelség) csupán egy lehetséges jellemző, ami mögött társadalmi kapcsolatok, tudásbeli azonosság vagy intézményi rokonság húzódik meg, és utóbbiak segítik elő a partnerség kialakulását? Vajon az együttműködés vizsgálatával kaphatunk magyarázatot a rendkívül gyenge és izolált hazai innovációs kapcsolatrendszerre?* Journal of Economic Literature (JEL) kód: JEL: D85, L14, R11, O31

A Structural Empirical Analysis of Retail Banking Competition: the Case of Hungary

In this paper we analyze the degree of competition in the Hungarian household credit and deposit markets. We estimate discrete-choice, multinomial logit deposit service and loan demand functions for each bank and calculate the corresponding price elasticities. Two models of the banking industry are considered: a static, differentiated product Nash-Bertrand oligopoly (as non-collusive benchmark) and a cartel. With estimated marginal costs and observed interest rates we calculate the price-cost margins and compare these to the theoretically implied ones. We find that in our sample period the competition in the Hungarian banking sector is low, i.e. price-cost margins are high.Demand, discrete choice, product differentiation, banking, market power.

Mean-field analysis of load balancing principles in large scale systems

Load balancing plays a crucial role in many large scale systems. Several different load balancing principles have been proposed in the literature, such as Join-Shortest-Queue (JSQ) and its variations, or Join-Below-Threshold. We provide a high level mathematical framework to examine heterogeneous server clusters in the mean-field limit as the system load and the number of servers scale proportionally. We aim to identify both the transient mean-field limit and the stationary mean-field limit for various choices of load balancing principles, compute relevant performance measures such as the distribution and mean of the system time of jobs, and conduct a comparison from a performance point of view

Real-time Queue Length Estimation Applying Shockwave Theory at Urban Signalized Intersections

Signal control is a basic need for urban traffic control; however, it is a very rough intervention in the free flow of traffic, which often results in queues in front of signal heads. The general goal is to reduce the delays caused, and to plan efficient traffic management on the network. For this, the exact knowledge of queue lengths on links is one of crucial importance. This article presents a link-based methodology for real-time queue length estimation in urban signalized road networks. The model uses a Kalman Filter-based recursive method and estimates the length of the queue in every cycle. The input of the filter, i.e. the dynamics of queue length is described by the traffic shockwave theory and the store and forward model. The method requires one loop-detector per link placed at the appropriate position, for which the article also provides suggestions

Harmonic Manifolds and the Volume of Tubes about Curves

H. Hotelling proved that in the n-dimensional Euclidean or spherical space, the volume of a tube of small radius about a curve depends only on the length of the curve and the radius. A. Gray and L. Vanhecke extended Hotelling's theorem to rank one symmetric spaces computing the volumes of the tubes explicitly in these spaces. In the present paper, we generalize these results by showing that every harmonic manifold has the above tube property. We compute the volume of tubes in the Damek-Ricci spaces. We show that if a Riemannian manifold has the tube property, then it is a 2-stein D'Atri space. We also prove that a symmetric space has the tube property if and only if it is harmonic. Our results answer some questions posed by L. Vanhecke, T. J. Willmore, and G. Thorbergsson.Comment: 17 pages, no figures. This version is different from the journal versio