Stationary Lifshitz black holes of R^2-corrected gravity theory

In this short note, I present a generalization of a set of static D-dimensional (D >= 3) Lifshitz black holes, which are solutions of the gravitational model obtained by amending the cosmological Einstein theory with the addition of only the curvature-scalar-squared term and that are described by two parameters, to a more general class of exact, analytic solutions that involves an additional parameter which now renders them stationary. In the special D=3 and the dynamical exponent z=1 case, the parameters can be adjusted so that the solution becomes identical to the celebrated BTZ black hole metric.Comment: 7 pages, no figures; ver. 2: added 5 new references (accepted by PRD as a Brief Report

Local cosmic strings in Brans-Dicke theory with a cosmological constant

It is known that Vilenkin's phenomenological equation of state for static straight cosmic strings is inconsistent with Brans-Dicke theory. We will prove that, in the presence of a cosmological constant, this equation of state is consistent with Brans-Dicke theory. The general solution of the full nonlinear field equations, representing the interior of a cosmic string with a cosmological constant is also presented.Comment: 5 pages, Revte

Spain’s referendum on the European Constitutional Treaty: a quantitative analysis within the conceptual framework of first and second order elections

In contrast to the attention devoted to the rejection of the EU Constitutional Treaty at French and Dutch referenda; the Spanish referendum, where this Treaty was ratified, remained under-researched by political scientists. This paper analyses the voting behaviour at the Spanish referendum on the EU Constitutional Treaty with the use of quantitative methods and the concept of first and second-order elections. This paper finds that the Spanish referendum was a second-order referendum, because the effects of domestic political issues in Spain had a greater impact on the electoral behaviour of Spanish voters than had genuinely European issues. This finding raises doubts over the suitability of using direct democracy in the EU in order to raise the legitimacy and democratic accountability of the European project

Opportunism in Multiuser Relay Channels: Scheduling, Routing and Spectrum Reuse

In order to understand the key merits of multiuser diversity techniques in relay-assisted cellular multihop networks, this paper analyzes the spectral efficiency of opportunistic (i.e., channel-aware) scheduling algorithms over a fading multiuser relay channel with $K$ users in the asymptotic regime of large (but finite) number of users. Using tools from extreme-value theory, we characterize the limiting distribution of spectral efficiency focusing on Type I convergence and utilize it in investigating the large system behavior of the multiuser relay channel as a function of the number of users and physical channel signal-to-noise ratios (SNRs). Our analysis results in very accurate formulas in the large (but finite) $K$ regime, provides insights on the potential performance enhancements from multihop routing and spectrum reuse policies in the presence of multiuser diversity gains from opportunistic scheduling and helps to identify the regimes and conditions in which relay-assisted multiuser communication provides a clear advantage over direct multiuser communication.Comment: 5 page

A Model of Dynamic Liquidity Contracts

The main goal of this paper is to analyze the nature of long-term liquidity contracts that arise between lenders and borrowers in the absence of perfect enforceability and when both parties are financially constrained. We study an infinite horizon dynamic contracting model between a borrower and a lender with the following features: The borrower, is credit-constrained, faces a stochastic project arrival process every period, can choose to renege each period, and can save through the lender. Projects are indivisible. The lender is resource- constrained, and can commit to the terms of the contract as long as it is ex-ante individually rational to do so. We show that: (i) Enforcement problems and endogenous resource constraints can severely curtail the possibility of financing projects, (ii) the economy exhibits investment cycles, (iii) credit is rationed if either the lender has too little capital or the borrower has too little financial collateral. This paper’s technical contribution is to show the existence and characterization of financial contracts that are solutions to a non- convex dynamic programming problem.Credit Rationing, Investment Cycles, Limited Enforceability, Liquidity Provision, Resource Constraints