How Different is Wireless Access? Implications for Internet Mergers

Network hierarchies in the Internet are often not fixed: two providers can be simultaneously input supplier and retailer in a routing process, while being horizontally competing in another. We introduce a stylised network model capturing these aspects of the Internet to study the impact of differentiation introduced by wireless access on prices and profits. We then study the incentives for, and welfare impact of, a merger between the wireless provider and a local bottleneck fixed access one. These effects crucially depend on the degree of differentiation between the wireless and fixed Internet access modalities. Pricing, at each router, follows the motorway toll metaphor

On the Evolution of Regional Asymmetries

The paper models the evolution of regional asymmetries, and the associated intra-distribution mobility, as the outcome of adoption decisions taken by firms at different locations. The following equilibria are characterised: Persistent asymmetry where nobody adopts, Leapfrogging where low-quality firms adopt, Forging ahead where high-quality firms adopt, and Catching up where everybody adopts. The paper studies the impact of economic integration on these equilibria and the evolution of technological asymmetries as well as intra-distribution mobility. In equilibrium, the regional intra-distribution Mobility is described by fluctuations between periods of Leapfrogging, Forging ahead and Catching up

Separability conditions from entropic uncertainty relations

We derive a collection of separability conditions for bipartite systems of dimensions d X d which is based on the entropic version of the uncertainty relations. A detailed analysis of the two-qubit case is given by comparing the new separability conditions with existing criteria.Comment: 10 pages, 2 figure (Typos removed. To appear in Phys. Rev. A

Limits to clock synchronization induced by completely dephasing communication channels

Clock synchronization procedures are analyzed in the presence of imperfect communications. In this context we show that there are physical limitations which prevent one from synchronizing distant clocks when the intervening medium is completely dephasing, as in the case of a rapidly varying dispersive medium.Comment: 6 Pages. Revised version as published in PR

A Protocol For Cooling and Controlling Composite Systems by Local Interactions

We discuss an explicit protocol which allows one to externally cool and control a composite system by operating on a small subset of it. The scheme permits to transfer arbitrary and unknown quantum states from a memory on the network ("upload access") as well as the inverse ("download access"). In particular it yields a method for cooling the system.Comment: 8 pages, 5 figures: in "Quantum Information and Many Body Quantum Systems", proceedings, M. Ericsson and S. Montangero (eds.), Pisa, Edizioni della Normale, p. 17 (2008

The role of entanglement in dynamical evolution

Entanglement or entanglement generating interactions permit to achieve the maximum allowed speed in the dynamical evolution of a composite system, when the energy resources are distributed among subsystems. The cases of pre-existing entanglement and of entanglement-building interactions are separately addressed. The role of classical correlations is also discussed.Comment: 5 pages, 1 figure. Revised versio

Antitrust Analysis for the Internet Upstream Market: a BGP Approach

In this paper we study concentration in the European Internet upstream access market. Measurement of market concentration depends on correctly defining the market, but this is not always possible as Antitrust authorities often lack reliable pricing and traffic data. We present an alternative approach based on the inference of the Internet Operators interconnection policies using micro-data sourced from their Border Gateway Protocol tables. Firstly we propose a price-independent algorithm for defining both the vertical and geographical relevant market boundaries, then we calculate market concentration indexes using two novel metrics. These assess, for each undertaking, both its role in terms of essential network facility and of wholesale market dominance. The results, applied to four leading Internet Exchange Points in London, Amsterdam, Frankfurt and Milan, show that some vertical segments of these markets are extremely competitive, while others are highly concentrated, putting them within the special attention category of the Merger Guidelines

Thermodynamics of discrete quantum processes

We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency.Comment: 14pages, 9 figure