Supersymmetric Models for Fermions on a Lattice

We investigate the large-N behaviour of simple examples of supersymmetric interactions for fermions on a lattice. Witten's supersymmetric quantum mechanics and the BCS model appear just as two different aspects of one and the same model. For the BCS model, supersymmetry is only respected in a coherent superposition of Bogoliubov states. In this coherent superposition mesoscopic observables show better stability properties than in a Bogoliubov state.Comment: 17 pages, LATeX, no figure

Central limit theorems for the large-spin asymptotics of quantum spins

We use a generalized form of Dyson's spin wave formalism to prove several central limit theorems for the large-spin asymptotics of quantum spins in a coherent state.Comment: 28 pages, uses package amsref

Does aid mitigate external shocks?

This paper investigates the role of aid in mitigating the adverse effects of commodity export price shocks on growth in commodity-dependent countries. Using a large cross-country dataset, we find that negative shocks matter for short-term growth, while the ex ante risk of shocks does not seem to matter. We also find that both the level of aid and the flexibility of the exchange rate substantially lower the adverse growth effect of shocks. While the mitigating effect of aid is significant in both countries with pegs and countries with floats, the effect seems to be smaller for the latter, suggesting that aid and exchange rate flexibility are partly substitutes. We investigate whether aid has historically been targeted at shock-prone countries, but find no evidence that this is the case. This suggests that donors could increase aid effectiveness by redirecting aid towards countries with a high incidence of commodity export price shocks.commodity prices; aid; growth; external shocks

The Effect of Monetary Policy on Exchange Rates during Currency Crises; The Role of Debt, Institutions and Financial Openness

This paper examines the effect of monetary policy on the exchange rate during currency crises. Using data for a number of crisis episodes between 1986 and 2004, we find strong evidence that raising the interest rate: (i) has larger adverse balance sheet effects and is therefore less effective in countries with high domestic corporate short-term debt; (ii) is more credible and therefore more effective in countries with high-quality institutions; iii) is more credible and therefore more effective in countries with high external debt; and (iv) is less effective in countries with high capital account openness. We predict that monetary policy would have had the conventional supportive effect on the exchange rate during five of the crisis episodes in our sample, while it would have had the perverse effect during seven other episodes. For four episodes, we predict a statistically insignificant effect. Our results support the idea that the effect of monetary policy depends on its impact on fundamentals, as well as its credibility, as suggested in the recent theoretical literature. They also provide an explanation for the mixed findings in the empirical literature.Institutions;Capital Account Openness;Currency Crises;External Debt;Monetary Policy;Short-Term Debt

Human Rights Violations After 9/11 and the Role of Constitutional Constraints

human rights, terrorism, 9/11, checks and balances, constitutions, constitutional courts

Does Aid Mitigate External Shocks?

This paper investigates the role of aid in mitigating the adverse effects of commodity export price shocks on growth in commodity-dependent countries. Using a large cross-country dataset, we find that negative shocks matter for short-term growth, while the ex ante risk of shocks does not seem to matter. We also find that both the level of aid and the flexibility of the exchange rate substantially lower the adverse growth effect of shocks. While the mitigating effect of aid is significant in both countries with pegs and countries with floats, the effect seems to be smaller for the latter, suggesting that aid and exchange rate flexibility are partly substitutes. We investigate whether aid has historically been targeted at shock-prone countries, but find no evidence that this is the case. This suggests that donors could increase aid effectiveness by redirecting aid towards countries with a high incidence of commodity export price shocks.aid, commodities, export, price shocks

Structural policies for shock-prone developing countries

Developing countries frequently face large adverse shocks to their economies. We study two distinct types of such shocks: large declines in the price of a country’s commodity exports and severe natural disasters. Unsurprisingly, adverse shocks reduce the short-term growth of constant-price GDP and we analyse which structural policies help to minimize these losses. Structural policies are incentives and regulations that are maintained for long periods, contrasting with policy responses to shocks, the analysis of which has dominated the literature. We show that some previously neglected structural policies have large effects that are specific to particular types of shock. In particular, regulations which reduce the speed of firm exit substantially increase the short-term growth loss from adverse non-agricultural export price shocks and so are particularly ill-suited to mineral exporting economies. Natural disasters appear to be better accommodated by labour market policies, perhaps because such shocks directly dislocate the population.commodity price shocks; natural disasters; growth, policies

Structural Policies for Shock-Prone Developing Countries

Many developing countries periodically face large adverse shocks to their economies. We study two distinct types of such shocks - large declines in the price of a country’s commodity exports and severe natural disasters - , both of which have occurred frequently in the recent past. Unsurprisingly, adverse shocks reduce the short-term growth of constant-price GDP and we analyze which structural policies help to minimize these losses. Structural policies are incentives and regulations that are maintained for long periods, contrasting with policy responses to shocks, the analysis of which has dominated the literature. We show that some previously neglected structural policies have large effects that are specific to particular types of shock. In particular, regulations which reduce the speed of firm exit substantially increase the short-term growth loss from adverse non-agricultural export price shocks and so are particularly ill-suited to mineral exporting economies. Natural disasters appear to be better accommodated by labour market policies, perhaps because such shocks directly dislocate the population.commodity price shocks; natural disasters; growth, policies