From Derrida's random energy model to branching random walks: from 1 to 3

We study the extremes of a class of Gaussian fields with in-built hierarchical structure. The number of scales in the underlying trees depends on a parameter alpha in [0,1]: choosing alpha=0 yields the random energy model by Derrida (REM), whereas alpha=1 corresponds to the branching random walk (BRW). When the parameter alpha increases, the level of the maximum of the field decreases smoothly from the REM- to the BRW-value. However, as long as alpha<1 strictly, the limiting extremal process is always Poissonian.Comment: 12 pages, 1 figur

In silico identification and characterisation of 17 polymorphic anonymous non-coding sequence markers (ANMs) for red grouse (Lagopus lagopus scotica)

Peer reviewedPostprin

Computational Aspects of Maximum Likelihood Estimation of Autoregressive Fractionally Integrated Moving Average Models

We discuss computational aspects of likelihood-based estimation of univariate ARFIMA (p,d,q) models. We show how efficient computation and simulation is feasible, even for large samples. We also discuss the implementation of analytical bias corrections.Long memory, Bias, Modified profile likelihood, Restricted maximum likelihood estimator, Time-series regression model likelihood

Sectoral Agglomeration Economies in a Panel of European Regions

We estimate agglomeration economies, defined as the effect of density on labour productivity in European regions. The analysis of Ciccone (2002) is extended in two main ways. First, we use dynamic panel estimation techniques (system GMM), thus offering an alternative methodological treatment of the inherent endogeneity problem. Second, the sector dimension in the data allows for disaggregated estimation. Our results confirm the presence of significant agglomeration effects at the aggregate level, with an estimated long-run elasticity of 13 percent. Repeated crosssection regressions suggest that the strength of agglomeration effects has increased over time. At the sector level, the dominant pattern is of cross-sector "urbanisation" economies and own-sector congestion diseconomies. A notable exception is financial services, for which we find strong positive productivity effects from own-sector density.employment density; productivity; european regions; dynamic panel GMM

Intercommection Incentives of a Large Network Facing Multiple Rivals

This paper extends Cremer, Rey and Tirole’s analysis of whether a firm with the most installed-base customers, in a market exhibiting network externalities, gains by degrading interconnection with rivals that compete with it for new customers. We allow any number of rivals and consider both tipping equilibria and interior equlibria. Degrading interconnection can yield tipping away from the largest network even if its installed-base share exceeds one half. For all parameter values (including those that admit interior equilibria), a share above one half is necessary but not sufficient to ensure degradation is profitable. Greater scope for market expansion—a lower marginal cost or smaller installed-base relative to potential additional demand—makes profitable degradation less likely.Interconnection, Network Externalities, Exclusion