Managing financial risks in Papua New Guinea : an optimal external debt portfolio

This report shows that Papua New Guinea's assets and liabilities may be poorly balanced for debt servicing. Thus, it could benefit substantially from active risk management, especially through better selection of the financial instruments in its debt portfolio. The authors present a model and estimate of an optiomal debt portfolio that allows for the use of commodity-linked bonds and conventional debt denominated in different currencies. They judge the hedging effectiveness of this portfolio by how much the variance of expected real import is reduced. The results indicate that commodity-linked bonds could play an important role in the country's risk management strategy. They also show that the country's external debt structure is not well balanced to hedge the foreign exchange risk from the existing composition of non-U.S. dollar-denominated liabilities. The debt portfolio contains an excess of Japanese yen - and Deutschemark - denominated liabilities, while liabilities denominated in British pounds are substantially underrepresented.Economic Theory&Research,Environmental Economics&Policies,Public Sector Economics&Finance,Settlement of Investment Disputes,Strategic Debt Management

Scheduling for Optimal Rate Allocation in Ad Hoc Networks With Heterogeneous Delay Constraints

This paper studies the problem of scheduling in single-hop wireless networks with real-time traffic, where every packet arrival has an associated deadline and a minimum fraction of packets must be transmitted before the end of the deadline. Using optimization and stochastic network theory we propose a framework to model the quality of service (QoS) requirements under delay constraints. The model allows for fairly general arrival models with heterogeneous constraints. The framework results in an optimal scheduling algorithm which fairly allocates data rates to all flows while meeting long-term delay demands. We also prove that under a simplified scenario our solution translates into a greedy strategy that makes optimal decisions with low complexity

Spin-1/2 J1-J2 Heisenberg antiferromagnet on a square lattice: a plaquette renormalized tensor network study

We apply the plaquette renormalization scheme of tensor network states [Phys. Rev. E, 83, 056703 (2011)] to study the spin-1/2 frustrated Heisenberg J1-J2 model on a L*L square lattice with L = 8, 16 and 32. By treating tensor elements as variational parameters, we obtain the ground states for different J2/J1 values, and investigate the staggered magnetic order parameters, the nearest-neighbor spin-spin correlations and the plaquette order parameters. In addition to the well-known N\'eel-order and collinear-order at low and high J2/J1, we observe a plaquette order at intermediate J2/J1. A continuous transition between the N\'eel order and the plaquette order near J2 = 0.40J1 is observed. The collinear order emerges at J2 = 0.62J1 through a first-order phase transition.Comment: 6 pages, 5 figures total; added one figure; Revised argument in section 3, results unchanged; added note and reference wherei