ProtoDUNEs

These proceedings review the two DUNE prototype detectors, namely Single- and Dual-Phase ProtoDUNEs. The detectors, both employing liquid argon Time Projection Chambers (LAr TPCs), are currently being built at CERN as part of the ProtoDUNE experimental programme. Such R&D programme aims at validating the prototypes design and technology, which will eventually be applied to the DUNE Far Detector at the Sanford Underground Research Facility (SURF).Comment: Talk presented at NuPhys2016 (London, 12-14 December 2016). 8 pages, LaTeX, 3 figure

Thermal CFTs in momentum space

We study some aspects of conformal field theories at finite temperature in momentum space. We provide a formula for the Fourier transform of a thermal conformal block and study its analytic properties. In particular we show that the Fourier transform vanishes when the conformal dimension and spin are those of a "double twist" operator $\Delta = 2\Delta_\phi + \ell + 2n$. By analytically continuing to Lorentzian signature we show that the spectral density at high spatial momenta has support on the spectrum condition $|\omega| > |k|$. This leads to a series of sum rules. Finally, we explicitly match the thermal block expansion with the momentum space Green's function at finite temperature in several examples.Comment: Added 1 note and 1 referenc

Differential operators for superconformal correlation functions

We present a systematic method to expand in components four dimensional superconformal multiplets. The results cover all possible $\mathcal{N} = 1$ multiplets and some cases of interest for $\mathcal{N} = 2$. As an application of the formalism we prove that certain $\mathcal{N} = 2$ spinning chiral operators (also known as "exotic" chiral primaries) do not admit a consistent three-point function with the stress tensor and therefore cannot be present in any local SCFT. This extends a previous proof in the literature which only applies to certain classes of theories. To each superdescendant we associate a superconformally covariant differential operator, which can then be applied to any correlator in superspace. In the case of three-point functions, we introduce a convenient representation of the differential operators that considerably simplifies their action. As a consequence it is possible to efficiently obtain the linear relations between the OPE coefficients of the operators in the same superconformal multiplet and in turn streamline the computation of superconformal blocks. We also introduce a Mathematica package to work with four dimensional superspace.Comment: Fixed typos in Table 2 and Figure

Congestion, Private Peering and Capacity Investment on the Internet.

This paper presents a model of private bilateral and multilateral peering arrangements between Internet backbone providers when the network is congested. We study how different forms of interconnection and the competitive conditions of the market affect backbones' investments in network and peering point capacities. We show that network and peering point capacities are equilibrium complements; increasing competition reduces capacity investments (under-investment), thus worsening the quality of service both with multilateral and bilateral peering; under bilateral peering the inefficiency is less severe. Because of under-investment, welfare may be lower when the market is more competitive. We also show that asymmetries between backbones, which can take the form of uneven content distribution or product differentiation, may reduce under-investment and improve the quality of service. The introduction of an "inverse capacity interconnection fee" where providers pay each other a fee which is negatively correlated with their installed capacity may play the role of a coordinating mechanism towards a Pareto superior outcome.Internet, peering, congestion, QoS, capacity investment, interconnection

Dual licensing in open source software markets

Dual licensing has proved to be a sustainable business model for various commercial software vendors employing open source strategies. In this paper we study the main characteristics of dual licensing and under which conditions it represents a profitable commercial strategy. We show that dual licensing is a form of versioning, whereby the software vendor uses the open source licensing terms in order to induce commercial customers to select the proprietary version of the software. Furthermore, we show that the software vendor prefers dual licensing to a fully proprietary strategy when the customers are very sensitive to the reciprocal terms of the open source license

Plastic Clashes: Competition among Closed and Open Systems in the Credit Card Industry.

This paper analyses market competition between two different types of credit card platforms: not-for-profit associations and proprietary systems. The main focus is on the role of the interchange fee set by not-for-profit platforms. We show that when the interchange fee is set so as to maximise the sum of issuers' and acquirers' profits, the equilibrium values of platforms' profits, of the sum of the fees charged by each platform and their market shares are independent of the competitive conditions within the not-for-profit platform and are affected by the strength of inter-platform competition. We also show that the imposition of a ban on the setting of the interchange fee has ambiguous effects on the profit of the proprietary system.two-sided markets, network externalities, credit cards, interchange fee

On the role of public policies supporting Free/Open Source Software: an European perspective

Available in the .pd

Open Source vs Closed Source Software: Public Policies in the Software Market

This paper analyses the impact of public policies supporting open source software (OSS). Users can be divided between those who know about the existence of OSS, the "informed" adopters, and the "uninformed" ones; the presence of uniformed users yields to market failures that justify government intervention. We study three policies: i) mandatory adoption, when government forces public agencies, schools and universities to adopt OSS, ii) information campaign, when the government informs the uninformed users about the existence and the characteristics of OSS and, iii) subsidisation, when consumers are payed a subsidy when adopting OSS. We show that the second policy enhances welfare, the third is always welfare decreasing while mandatory adoption can be either good or bad for society depending on the number of informed and uninformed adopters. We extend the model to the presence of network effects and we show that strong externalities require "drastic" policies.software market, open source software, mandatory adoption, information campaign, subsidisation, network externalities

One-Way Compatibility, Two-Way Compatibility and Entry in Network Industries

We study the strategic choice of compatibility between two initially incompatible software packages in a two-stage game by an incumbent and an entrant firm. Consumers enjoy network externality in consumption and maximise expected surplus over the two periods. Compatibility may be achieved by means of a converter. We derive a number of results under diÆerent assumptions about the nature of the converter (one-way vs two-way) and the existence of property rights. In the case of a two-way converter, which can only be supplied by the incumbent, incompatibility will result in equilibrium and depending on the strength of network externalities the incumbent may deter entry. When both firms can build a one-way converter and there are no property rights on the necessary technical specifications, the only fulfilled expectations subgame perfect equilibrium involves full compatibility. Finally, when each firm has property rights on its technical specifications, full incompatibility and preemption are again observed at the equilibrium. Entry deterrence will then occur for su±ciently strong network eÆects. The analysis generalises to any market where network externalities are present.

One-Way Compatibility, Two-Way Compatibility and Entry in Network Industries

We study the strategic choice of compatibility between two initially incompatible network goods in a two-stage game played by an incumbent and an entrant firm. Compatibility may be achieved by means of a converter. We derive a number of results under different assumptions about the nature of the converter (one-way \emph{vs} two-way) and the existence of property rights. In the case of a two-way converter, which can only be supplied by the incumbent, incompatibility will result in equilibrium. When both firms can build a one-way converter and there are no property rights on the necessary technical specifications, the unique equilibrium involves full compatibility. Finally, when each firm has property rights on its technical specifications, full incompatibility and preemption are again observed at the equilibrium. With incompatibility, entry deterrence occurs for sufficiently strong network effects. The welfare analysis shows that the equilibrium compatibility regime is socially inefficient for most levels of the network effects.Network externalities, one-way compatibility, two-way compatibility, entry