Using a result of Harer, we prove certain upper bounds for the homotopical/cohomological dimension of the moduli spaces of Riemann surfaces of compact type, of Riemann surfaces with rational tails and of Riemann surfaces with at most k rational components. These bounds would follow from conjectures of Looijenga and Roth-

We provide a large deviation result for a random sum ∑Nx n=0Xn, where Nx is a renewal counting process and Xn n≥0 are i.i.d. random variables, independent of Nx , with a common distribution that belongs to a class of square root insensitive distributions. Asymptotically, the tails of these distributions are heavier than e− √ x and have zero relative decrease in intervals of length √ x, hence sq...

An EGARCH model in which the conditional distribution is heavytailed and skewed is proposed. The properties of the model, including unconditional moments, autocorrelations and the asymptotic distribution of the maximum likelihood estimator, are obtained. Evidence for skewness in conditional t-distribution is found for a range of returns series and the model is shown to give a better fit than th...

The h-index (Hirsch, 2005) is robust, remaining relatively unaffected by errors in the long tails of the citations-rank distribution, such as typographic errors that short-change frequently-cited papers and create bogus additional records. This robustness, and the ease with which h-indices can be verified, support the use of a Hirsch-type index over alternatives such as the journal impact facto...

How can a service firm right-size marketing expenses and yet strive to maximize revenue? This paper represents the first attempt to model these efficiency and effectiveness issues using a 49-unit Asia–Pacific hotel chain as illustration. We employ a triangular DEA model with total expenses (controlling for number of rooms) as the raw input, marketing expenses as intermediate output/input and re...

Using techniques developed in Kp1], we prove that the integrated density of states of A! = ?r 1 %! r has Lifshitz behavior in the neighborhood of the internal spectral gaps if and only if the integrated density of states of some periodic operator is non degenerated on the same edge of the spectral gaps. From this result we obtain the initial estimates necessary for deducing local-ization near n...

‎By observing the equivalence of assertions on determining the jump of a‎ ‎function by its differentiated or integrated Fourier series‎, ‎we generalize a‎ ‎previous result of Kvernadze‎, ‎Hagstrom and Shapiro to the whole class of‎ ‎functions of harmonic bounded variation‎. ‎This is achieved without the finiteness assumption on‎ ‎the number of discontinuities‎. ‎Two results on determination of ...

In a graph with a small world topology nodes are highly clustered yet the path length be tween them is small Such a topology can make search problems very di cult since local deci sions quickly propagate globally We show that graphs associated with many di erent search problems have a small world topology and that the cost of solving such search problems can have a heavy tailed distribution The...