Gravitational Collapse and Cosmological Constant

We consider here the effects of a non-vanishing cosmological term on the final fate of a spherical inhomogeneous collapsing dust cloud. It is shown that depending on the nature of the initial data from which the collapse evolves, and for a positive value of the cosmological constant, we can have a globally regular evolution where a bounce develops within the cloud. We characterize precisely the initial data causing such a bounce in terms of the initial density and velocity profiles for the collapsing cloud. In the cases otherwise, the result of collapse is either formation of a black hole or a naked singularity resulting as the end state of collapse. We also show here that a positive cosmological term can cover a part of the singularity spectrum which is visible in the corresponding dust collapse models for the same initial data.Comment: 18 pages, no figure

Appearance of the central singularity in spherical collapse

We analyze here the structure of non-radial nonspacelike geodesics terminating in the past at a naked singularity formed as the end state of inhomogeneous dust collapse. The spectrum of outgoing nonspacelike null geodesics is examined analytically. The local and global visibility of the singularity is also examined by integrating numerically the null geodesics equations. The possible implications of existence of such families towards the appearance of the star in late stages of gravitational collapse are considered. It is seen that the outgoing non-radial geodesics give an appearance to the naked central singularity as that of an expanding ball whose radius reaches a maximum before the star goes within its apparent horizon. The radiated energy (along the null geodesics) is shown to decay very sharply in the neighbourhood of the singularity. Thus the total energy escaping via non-radial null geodesics from the naked central singularity vanishes in the scenario considered here.Comment: 25 pages, 6 figure

Livestock, vulnerability, and poverty dynamics in India

The focus of this study is to identify the livelihood activities that produce the major share of household income as well as to identify the livelihood pathways and strategies, and the role of livestock in these activities and strategies over a six year period. The paper is organized as follows. Section one is Introduction; Section 2 describes the methodology and data. Section 3 examines the extent of movements into and out of poverty amongst the sample households. Sections 4 and 5 describe the extent of destitution, vulnerability, viability and sustainability in connection with livelihood pathways. Section 6 examines the factors associated with economic/poverty status. Section 7 summarises the role of livestock in these livelihood connections. Finally, the paper draws some policy conclusions and recommendations and discusses the future direction of research

The structure of non-spacelike geodesics in dust collapse

We study here the behaviour of non-spacelike geodesics in dust collapse models in order to understand the casual structure of the spacetime. The geodesic families coming out, when the singularity is naked, corresponding to different initial data are worked out and analyzed. We also bring out the similarity of the limiting behaviour for different types of geodesics in the limit of approach to the singularity.Comment: 23 pages, 6 figures, to appear in PR

Livestock and poverty reduction in India: findings from the ODI Livelihood Options Project

This paper is based on data collected under the Livelihood Options Project, a three year DFID funded policy study located in the Indian States of Andhra Pradesh (AP) and Madhya Pradesh (MP). The purpose of this project is to identify factors promoting or impeding diversification out of low productivity livelihoods, and identify the policy changes necessary to support upward trajectories and prevent downward ones. It explores the role of livestock in rural livelihoods and its potential to assist people in escaping poverty using a combination of quantitative and qualitative methods. Main topics of discussion include economic importance of livestock; macro level trends in AP and MP; and variations in income and livestock keeping. Three study findings are presented. These are Broad patters-lists livestock and farmer category, and livestock types by caste categories; Who keeps what and why? This finding discusses overviews of Andhra Pradesh and Madhya Pradesh and discusses goats as an increasingly popular accumulative option. The last Study finding - Does livestock provide a useful coping mechanism to vulnerable households and individuals - outlines migration and livestock case studies, and village accounts of livestock keeping patterns. The paper ends with conclusion and policy implications

Drought and vulnerability of livestock in India

This study examines the dynamics of livestock keeping in recent years when occurrence of droughts was severe; the function of livestock in reducing the vulnerability to shocks and stresses to which the poor are exposed; and the relationship between migration and aspects of livestock keeping in the context of drought and vulnerability. The discussion paper is organized as follows: Following the executive summary, Section 2 introduces the paper giving its background. Section 3 describes the methodology. Section 4 presents an overview of livestock keeping and poverty. Section 5 describes the dynamics of livestock keeping in two subsections. Section 6 analyzes livestock sales due to major expenses in three years. The relationship between migration income and livestock keeping is examined in Section 7. The paper concludes with Section 8, where implications are discussed. Questionnaire for 2005 panel re-survey and qualitative assessment of the impact of commercial poultry farms on backyard poultry production and additional tabulation are included in the appendices. The report is primarily based on the 2005 re-survey data supplemented by data collected from 2001-02 survey as well as qualitative method

On the global visibility of singularity in quasi-spherical collapse

We analyze here the issue of local versus the global visibility of a singularity that forms in gravitational collapse of a dust cloud, which has important implications for the weak and strong versions of the cosmic censorship hypothesis. We find conditions as to when a singularity will be only locally naked, rather than being globally visible, thus preseving the weak censorship hypothesis. The conditions for formation of a black hole or naked singularity in the Szekeres quasi-spherical collapse models are worked out. The causal behaviour of the singularity curve is studied by examining the outgoing radial null geodesics, and the final outcome of collapse is related to the nature of the regular initial data specified on an initial hypersurface from which the collapse evolves. An interesting feature that emerges is the singularity in Szekeres spacetimes can be ``directionally naked''.Comment: Latex file, 32 pages, 12 postscript figures. To appear in the Journal of General Relativity and Gravitatio

Quantum Radiation from Black Holes and Naked Singularities in Spherical Dust Collapse

A sufficiently massive collapsing star will end its life as a spacetime singularity. The nature of the Hawking radiation emitted during collapse depends critically on whether the star's boundary conditions are such as would lead to the eventual formation of a black hole or, alternatively, to the formation of a naked singularity. This latter possibility is not excluded by the singularity theorems. We discuss the nature of the Hawking radiation emitted in each case. We justify the use of Bogoliubov transforms in the presence of a Cauchy horizon and show that if spacetime is assumed to terminate at the Cauchy horizon, the resulting spectrum is thermal, but with a temperature different from the Hawking temperature.Comment: PHYZZX macros, 27 pages, 3 figure

Risk attitudes and informal employment in a developing economy

© 2012 Bennett et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License(http://creativecommons.org/licenses/by/2.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.We model an urban labour market in a developing economy, incorporating workers’ risk attitudes. Trade-offs between risk aversion and ability determine worker allocation across formal and informal wage employment, and voluntary and involuntary self employment. Greater risk of informal wage non-payment can raise or lower informal wage employment, depending on the source of risk. Informal wage employment can be reduced by increasing detection efforts or by strengthening contract enforcement for informal wage payment. As the average ability of workers rises, informal wage employment first rises, then falls. Greater demand for formal production may lead to more involuntary self employment

Moving in and out of vulnerability : interrogating migration as an adaptation strategy along a rural-urban continuum in India

Drawing on life history interviews, the paper explores the role of migration and commuting in addressing livelihood vulnerability along a rural–urban continuum in Karnataka, India. Using life histories as a methodological tool can complement econometric approaches, allowing for in‐depth and temporally sensitive inquiry into the drivers and consequences of migration. The study locates present‐day vulnerability in Kolar and Gulbarga as points on a regionally differentiated development pathway. Both Kolar and Gulbarga are sites of prominent out-migration due to their geographical contexts. Findings show drivers of migration are based on livelihood expectations, and perceived lack of opportunities in rural areas.UK Department for International Development (DFID