A comparison of policies to reduce the methane emission intensity of smallholder dairy production in India

Within the dairy sector, the effects of climate change are particularly diverse as cows are affected by, and a significant contributor to climate change. With a burgeoning body of work indicating the importance of livestock’s contribution to climate change (via Greenhouse Gas (GHG) emissions), the dairy sector will increasingly be targeted for emission reduction. Yet, gaps in knowledge remain as to the effectiveness of interventions in achieving emission reductions. The investigation examines two high-profile Indian policies to evaluate their effectiveness in reducing the methane emission intensity of milk production in Odisha, India. Selected policies included the installation of smallscale anaerobic digesters and the control of Foot and Mouth Disease (FMD). The interventions were evaluated at the cow level informed by data collected from 115 smallholder dairy producers in Puri (n =31) and Khurda (n =84) districts in Odisha, India. The installation of an anaerobic digester was found to increase methane emission intensity by 4.41–5.01%. Control of FMD reduced methane emission intensity by 3.68–12.95% depending on the infection scenario considered. The findings highlight the importance of contextually relevant and multi-sectoral approaches to mitigation as the increase in methane emission intensity following anaerobic digester installation represents movement of emissions from the energy sector into the dairy sector where mitigation is inherently more complex. Thus, the long-term usefulness of anaerobic digester installation as a mitigation strategy is limited

The Measure of Cosmological Parameters

New, large, ground and space telescopes are contributing to an exciting and rapid period of growth in observational cosmology. The subject is now far from its earlier days of being data-starved and unconstrained, and new data are fueling a healthy interplay between observations and experiment and theory. I briefly review here the status of measurements of a number of quantities of interest in cosmology: the Hubble constant, the total mass-energy density, the matter density, the cosmological constant or dark energy component, and the total optical background light.Comment: 12 pages, 4 figures, to be published in "2001: A Spacetime Odyssey: Proceedings of the Inaugural Conference of the Michigan Center for Theoretical Physics", Michael J. Duff & James T. Liu, eds., (World Scientific, Singapore), in pres

Towards a Singularity-Proof Scheme in Numerical Relativity

Progress in numerical relativity has been hindered for 30 years because of the difficulties of avoiding spacetime singularities in numerical evolution. We propose a scheme which excises a region inside an apparent horizon containing the singularity. Two major ingredients of the scheme are the use of a horizon-locking coordinate and a finite differencing which respects the causal structure of the spacetime. Encouraging results of the scheme in the spherical collapse case are given.Comment: 9 page

Self-Renormalization of the Classical Quasilocal Energy

Pointlike objects cause many of the divergences that afflict physical theories. For instance, the gravitational binding energy of a point particle in Newtonian mechanics is infinite. In general relativity, the analog of a point particle is a black hole and the notion of binding energy must be replaced by quasilocal energy. The quasilocal energy (QLE) derived by York, and elaborated by Brown and York, is finite outside the horizon but it was not considered how to evaluate it inside the horizon. We present a prescription for finding the QLE inside a horizon, and show that it is finite at the singularity for a variety of types of black hole. The energy is typically concentrated just inside the horizon, not at the central singularity.Comment: 7 pages, 4 figure

Local and global properties of conformally flat initial data for black hole collisions

We study physical properties of conformal initial value data for single and binary black hole configurations obtained using conformal-imaging and conformal-puncture methods. We investigate how the total mass M_tot of a dataset with two black holes depends on the configuration of linear or angular momentum and separation of the holes. The asymptotic behavior of M_tot with increasing separation allows us to make conclusions about an unphysical ``junk'' gravitation field introduced in the solutions by the conformal approaches. We also calculate the spatial distribution of scalar invariants of the Riemann tensor which determine the gravitational tidal forces. For single black hole configurations, these are compared to known analytical solutions. Spatial distribution of the invariants allows us to make certain conclusions about the local distribution of the additional field in the numerical datasets

Stuffed Black Holes

Initial data corresponding to spacetimes containing black holes are considered in the time symmetric case. The solutions are obtained by matching across the apparent horizon different, conformally flat, spatial metrics. The exterior metric is the vacuum solution obtained by the well known conformal imaging method. The interior metric for every black hole is regular everywhere and corresponds to a positive energy density. The resulting matched solutions cover then the whole initial (Cauchy) hypersurface, without any singularity, and can be useful for numerical applications. The simpler cases of one black hole (Schwarzschild data) or two identical black holes (Misner data) are explicitly solved. A procedure for extending this construction to the multiple black hole case is also given, and it is shown to work for all time symmetric vacuum solutions obtained by the conformal imaging method. The numerical evolution of one such 'stuffed' black hole is compared with that of a pure vacuum or 'plain' black hole in the spherically symmetric case.Comment: 12 pages, Latex, 4 postscript figures, corrected some typos, new section about physical interpretatio

Modifying the Einstein Equations off the Constraint Hypersuface

A new technique is presented for modifying the Einstein evolution equations off the constraint hypersurface. With this approach the evolution equations for the constraints can be specified freely. The equations of motion for the gravitational field variables are modified by the addition of terms that are linear and nonlocal in the constraints. These terms are obtained from solutions of the linearized Einstein constraints.Comment: 4 pages, 1 figure, uses REVTe