Polynomial cases of the tarification problem

We consider the problem of determining a set of optimal tariffs for an agent in a network, who owns a subset of the arcs of the network, and who wishes to maximize his revenues on this subset from a set of clients that make use of the network.The general variant of this problem is NP-hard, already with a single client. This paper introduces several new polynomially solvable special cases. An important case is the following.For multiple clients, if the number of tariff arcs is bounded from above, we can solve the problem by a polynomial number of linear programs (each of which is of polynomial size). Furthermore, we show that the parametric tarification problem and the single arc fixed charge tarification problem can be solved in polynomial time.Economics ;

Pricing Network Edges to Cross a River.

We consider a Stackelberg pricing problem in directed networks:Tariffs (prices) have to be defined by an operator, the leader, for a subset of the arcs. Clients, the followers, choose paths to route their demand through the network selfishly and independently of each other, on the basis of minimal total cost. The problem is to find tariffs such as to maximize the operator''s revenue. We consider the case where each client takes at most one tariff arc to route the demand.The problem, which we refer to as the river tarification problem, is a special case of problems studied previously in the literature.We prove that the problem is strongly NP-hard.Moreover, we show that the polynomially solvable case of uniform tarification yields an m--approximation algorithm, and this is tight. We suggest a new type of analysis that allows to improve the result to \bigO{\log m}, whenever the input data is polynomially bounded. We furthermore derive an \bigO{m^{1-\varepsilon}}--inapproximability result for problems where the operator must serve all clients, and we discuss some polynomial special cases. Finally, a computational study with instances from France Telecom suggests that uniform pricing performs better in practice than theory would suggest.operations research and management science;

Tariff optimization in Networks

We consider the problem of determining a set of optimal tariffs for an agent in the network, who owns a subset of all the arcs, and who receives revenue by setting the tariffs on the arc he owns. Multiple rational clients are active in the network, who route their demands on the cheapest paths from source to destination. The cost of a path is determined by fixed costs and tariffs on the arcs of the path.We introduce a remodeling of the network, using shortest paths. We develop three algorithms, a path oriented mixed integer program and a known arc oriented mixed integer program. Combined with reduction methods this remodeling enables us to solve the problem to optimality, for quite large instances. We provide computational results for the methods developped and compare them with the results of the arc oriented mixed integer programming formulation of the problem, applied to the original network.Economics ;

Working Papers, Open Access and Cyber-Infrastructure in Classical Studies

Princeton–Stanford Working Papers in Classics is a web-based series of work-in-progress scripts by members of two leading departments of classics. It introduces the humanities to a new form of scholarly communication and represents a major advance in the free availability of classical-studies scholarship in cyberspace. This article both reviews the initial performance of this open-access experiment and the benefits and challenges of working papers more generally for classical studies. After two years of operation Princeton–Stanford Working Papers in Classics has proven to be a clear success. This series has built up a large international readership and a sizeable body of preprints and performs important scholarly and community-outreach functions. As this performance is largely due to its congruency with the working arrangements of ancient historians and classicists and the global demand for open-access scholarship, the series confirms the viability of this means of scholarly communication and the likelihood of its expansion in our discipline. But modifications are required to increase the benefits this series brings and the amount of scholarship it makes freely available online. Finally departments wishing to replicate its success will have to consider other important developments, such as the increasing availability of postprints, the linking of research funding to open access, and the emergence of new cyber-infrastructure

Search for a Standard Model Higgs boson in the mass range 200-600 GeV in the H→ZZ→ℓ+ℓ−qq¯ decay channel with the ATLAS detector

A search for a heavy Standard Model Higgs boson decaying via H→ZZ→ℓ+ℓ−qq¯, where ℓ=e or μ, is presented. The search uses a data set of pp collisions at √s =7 TeV, corresponding to an integrated luminosity of 4.7 fb−1 collected in 2011 by the ATLAS detector at the CERN LHC. No significant excess of events above the estimated background is found. Upper limits at 95% confidence level on the production cross section of a Higgs boson with a mass in the range between 200 and 600 GeV are derived. A Standard Model Higgs boson with a mass in the range 300 GeV≤mH ≤ 322 GeV or 353 GeV ≤mH ≤ 410 GeV is excluded at 95% CL. The corresponding expected exclusion range is 351 GeV ≤mH ≤ 404 GeV at 95% CL

Search for diphoton events with large missing transverse momentum in 1 fb−1 of 7 TeV proton-proton collision data with the ATLAS detector

A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb−1 of proton-proton collision data at √s = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics. The limits depend on each model parameter space and vary as follows: σ<(22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, σ<(27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8), and σ<(15-27) fb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 805 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass. Lower limits of 145 TeV and 1.23 TeV are set on the SPS8 breaking scale Λ and on the UED compactification scale 1/R, respectively. These limits provide the most stringent tests of these models to date