Approximating RR Lyrae light curves using cubic polynomials

In this paper, we use cubic polynomials to approximate RR Lyrae light curves and apply the method to HST data of RR Lyraes in the halo of M31. We compare our method to the standard method of Fourier decomposition and find that the method of cubic polynomials eliminates virtually all ringing effects and does so with significantly fewer parameters than the Fourier technique. Further, for RRc stars the parameters in the fit are all physical. Our study also reveals a number of additional periodicites in this data not found previously: we find 23 RRc stars, 29 RRab stars and 3 multiperiodic stars.Comment: 6 pages, MNRAS accepte

The Detailed Forms of the LMC Cepheid PL and PLC Relations

Possible deviations from linearity of the LMC Cepheid PL and PLC relations are investigated. Two datasets are studied, respectively from the OGLE and MACHO projects. A nonparametric test, based on linear regression residuals, suggests that neither PL relation is linear. If colour dependence is allowed for then the MACHO PL relation is found to deviate more significantly from the linear, while the OGLE PL relation is consistent with linearity. These finding are confirmed by fitting "Generalised Additive Models" (nonparametric regression functions) to the two datasets. Colour dependence is shown to be nonlinear in both datasets, distinctly so in the case of the MACHO Cepheids. It is also shown that there is interaction between the period and colour functions in the MACHO data.Comment: 20 pages, 20 figures, MNRAS accepte

Period-colour and amplitude-colour relations in classical Cepheid variables IV: The multi-phase relations

The superb phase resolution and quality of the OGLE data on LMC and SMC Cepheids, together with existing data on Galactic Cepheids, are combined to study the period-colour (PC) and amplitude-colour (AC) relations as a function of pulsation phase. Our results confirm earlier work that the LMC PC relation (at mean light) is more consistent with two lines of differing slopes, separated at a period of 10 days. However, our multi-phase PC relations reveal much new structure which can potentially increase our understanding of Cepheid variables. These multi-phase PC relations provide insight into why the Galactic PC relation is linear but the LMC PC relation is non-linear. This is because the LMC PC relation is shallower for short (log P < 1) and steeper for long (log P > 1) period Cepheids than the corresponding Galactic PC relation. Both of the short and long period Cepheids in all three galaxies exhibit the steepest and shallowest slopes at phases around 0.75-0.85, respectively. A consequence is that the PC relation at phase ~0.8 is highly non-linear. Further, the Galactic and LMC Cepheids with log P > 1 display a flat slope in the PC plane at phases close to the maximum light. When the LMC period-luminosity (PL) relation is studied as a function of phase, we confirm that it changes with the PC relation. The LMC PL relation in V- and I-band near the phase of 0.8 provides compelling evidence that this relation is also consistent with two lines of differing slopes joined at a period close to 10 days.Comment: 12 pages, 1 table and 13 figures, MNRAS accepte

Period-color and amplitude-color relations in classical Cepheid variables V: The Small Magellanic Cloud Cepheid models

Period-colour (PC) and amplitude-colour (AC) relations at maximum, mean and minimum light are constructed from a large grid of full amplitude hydrodynamic models of Cepheids with a composition appropriate for the SMC (Small Magellanic Cloud). We compare these theoretical relations with those from observations. The theoretical relations are in general good agreement with their observational counterparts though there exist some discrepancy for short period (log [P] < 1) Cepheids. We outline a physical mechanism which can, in principle, be one factor to explain the observed PC/AC relations for the long and short period Cepheids in the Galaxy, LMC and SMC. Our explanation relies on the hydrogen ionization front-photosphere interaction and the way this interaction changes with pulsation period, pulsation phase and metallicity. Since the PC relation is connected with the period-luminosity (PL) relation, it is postulated that such a mechanism can also explain the observed properties of the PL relation in these three galaxies.Comment: 10 pages, 6 figures and 6 tables, MNRAS accepte

Attacking Poverty: What is the Value Added of a Human Rights Approach?

Food Security and Poverty, International Development, Political Economy,

Welfare economics, political economy, and policy reform in Ghana

Welfare economics develops the logic of how the gains of the gainers and the losses of the losers should be weighed against each other, in a specific ethical framework. Political economy develops the logic of how they will be weighed against each other, in the context of sociopolitical institutions. The author applies the disciplines of both welfare economics and political economy in this evaluation of policy reform in Ghana. When considerations from both disciplines are aligned, he explains, policy reform not only should be enacted but is also likely to be enacted. Often, though, there is no such alignment, so reforms that might improve social welfare do not succeed. Analysts, says the author, should consider past reforms from both perspectives, and should learn from history, in evaluating proposed reform -- so they can assess both the desirability and the feasibility of reform. Policy makers, on the other hand, should work toward organizing and mobilizing the gainers from reform that would advance social welfare, so that resistance to such reform by the losers can be overcome. In an example from history, the author explains that Britain's debate over the Corn Laws -- basically a device for protecting domestic production of grain from cheap imports -- dominated for more than a decade in the nineteenth century. It eventually split the Tory party. Britain's transformation from an agrarian nation to a manufacturing one spelled the decline of the power of the landed aristocracy and the ascendance of manufacturing. In the end, the Corn Laws were repealed because of the growing power of the urban masses and their employers, and the debate soon turned to protection against imports from fast-industrializing France and Germany. Such episodes from history help us understand the protection of rice in Japan today, for example, and the focus of this paper -- the past decade of reform in Ghana, and the decade that awaits. The author argues that the political economy of policy reform in Ghana is likely to prove tougher in the second decade than in the first, for three reasons: 1) the economic situation in the second decade isno longer one of absolute disaster, with only one way to go; 2) in the second decade, policy reform will have to coincide with the transition from military to constitutional rule; and 3) the nature of the reforms to be undertaken in the second decade is different from that of those undertaken in the first.Economic Theory&Research,Environmental Economics&Policies,Achieving Shared Growth,Inequality,Economic Policy, Institutions and Governance

Why Might History Matter for Development Policy?

International Development, Political Economy,

Heterogeneity, distribution, and cooperation in common property resource management

The report considers the role of group heterogeneity in the success or failure of common property resource management. The author argues that cooperative agreements are less likely to come about when agents are highly heterogeneous along relevant dimensions - and existing agreements are more likely to break down as a group becomes more heterogeneous. The author crystallizes his argument in simple numerical examples and illustrates by reference to case studies on common property resource management, in particular, cases involving fisheries and irrigation systems. More work is needed to substantiate the author's argument, but his analysis so far supports the argument that equity and efficiency complement rather than oppose each other.Agricultural Research,Agricultural Knowledge&Information Systems,Poverty Assessment,Common Property Resource Development,Environmental Economics&Policies

Intergenerationalities: Some Educational Questions on Quality, Quantity and Opportunity

This paper raises a number of issues in thinking about and addressing the intergenerational transmission of disadvantage. Starting with choice subject to constraints by parents as determining outcomes for children, the paper identifies sequences of interventions to relieve “binding constraints” in the expansion of education. But the fact that parents choose for children is shown to raise a number of questions on normative aspects of inequality measurement. The main conclusions are as follows: (i) A key analytical task is to identify whether education is supply constrained or demand constrained; (ii) The cost-benefit analysis of identifying the “most binding constraint” requires the estimation of an education quality production function; (iii) The recent focus on “quality as opposed to quantity” in education is not self-evidently pro-poor; (iv) The intergenerational links inherent in education between parental choice and children’s outcomes, raise serious conceptual and empirical questions on attempts to separate out inequality of opportunity from inequality of outcomes.Intergenerationalities, Health Economics and Policy, International Development, Political Economy, Public Economics,

INTERNATIONAL FINANCIAL INSTITUTIONS AND INTERNATIONAL PUBLIC GOODS: OPERATIONAL IMPLICATIONS FOR THE WORLD BANK

The global International Financial Institutions (IFIs) increasingly justify their operations in terms of the provision of International Public Goods (IPGs). This is partly because there appears to be support among the rich countries of the North for expenditures on these IPGs, in contrast to the "aid fatigue" that afflicts the channelling of country specific assistance. But do the IFIs necessarily have to be involved in the provision of IPGs? If they do, what are the terms and conditions of that engagement? How does current practice compare to the ideal? And what reforms are needed to move us closer to the ideal? These are the questions that this paper attempts to ask, in the framework of the theory of International Public Goods, and in light of the practice of International Financial Institutions, the World Bank in particular. For the World Bank, a series of specific operational and resource reallocation implications are drawn from the reasoning.