Optimal power control in Cognitive MIMO systems with limited feedback

In this paper, the problem of optimal power allocation in Cognitive Radio (CR) Multiple Input Multiple Output (MIMO) systems is treated. The focus is on providing limited feedback solutions aiming at maximizing the secondary system rate subject to a constraint on the average interference caused to primary communication. The limited feedback solutions are obtained by reducing the information available at secondary transmitter (STx) for the link between STx and the secondary receiver (SRx) as well as by limiting the level of available information at STx that corresponds to the link between the STx and the primary receiver PRx. Monte Carlo simulation results are given that allow to quanitfy the performance achieved by the proposed algorithms

Hidden supersymmetry of domain walls and cosmologies

We show that all domain-wall solutions of gravity coupled to scalar fields for which the worldvolume geometry is Minkowski or anti-de Sitter admit Killing spinors, and satisfy corresponding first-order equations involving a superpotential determined by the solution. By analytic continuation, all flat or closed FLRW cosmologies are shown to satisfy similar first-order equations arising from the existence of ``pseudo-Killing'' spinors.Comment: 4 pages, v2:minor improvements, refs added, version to appear in PR

The Doha Talks and the Bargaining Surplus in Agriculture

The Doha Round has been slow to achieve a reduction in the level of agricultural protection. This remains the case notwithstanding the substantial economic benefits that would arise from a more liberal agricultural trading regime. We provide one explanation for this slowness using a simple bargaining model. We demonstrate that the bargaining countries received a substantial fiscal gain from reducing government expenditures in the run-up to the Uruguay Round. This fiscal pressure was sufficient to block rent seekers who wanted farm payments to continue. Since the Uruguay Round these fiscal constraints have been reduced and the same pressure to reach a bargain and control rent-seeking behaviour is not present in the Doha Round.Doha Round, rent seeking, bargaining, International Relations/Trade,

Theorizing Precommitment in European Integration: Mending the Constraints of Ulysses

The paper engages with the debate on Europe’s prospects by using Elster’s constraint theory to develop a model of precommitment in a context of diffuse reciprocity as a condition for interactive Europeanization. The current crisis constitutes a juncture in EU development, calling for a reassessment of the established views on Europe’s experiment. Europeanization emerges as a critical field for testing integration. The paper suggests a framework for the analysis of Europeanization which rests on two approaches: (a) the evolution of mixed and diffuse reciprocity (‘beyond tit-for-tat’) and (b) the development of precommitment and selfimposed constraints (‘Ulysses and the sirens’). It is argued that, given enormous challenges for the consolidation of precommitmnent due to a combination of economic strains and political gaps in steering, further evolution of advanced forms of reciprocity in Europe would require new goals, enhanced normative and value contents and increased political and normative scope for the constraints of Ulysses. This reassessment may bring European political traditions such as republicanism back in to the search for appropriate political, analytic, and normative prisms

Hamilton-Jacobi method for Domain Walls and Cosmologies

We use Hamiltonian methods to study curved domain walls and cosmologies. This leads naturally to first order equations for all domain walls and cosmologies foliated by slices of maximal symmetry. For Minkowski and AdS-sliced domain walls (flat and closed FLRW cosmologies) we recover a recent result concerning their (pseudo)supersymmetry. We show how domain-wall stability is consistent with the instability of adS vacua that violate the Breitenlohner-Freedman bound. We also explore the relationship to Hamilton-Jacobi theory and compute the wave-function of a 3-dimensional closed universe evolving towards de Sitter spacetime.Comment: 18 pages; v2: typos corrected, one ref added, version to appear in PR