16 research outputs found
Brane- gravity and dark matter
The collision-free Boltzmann equation is used in the context of brane-
gravity to derive the virial theorem. It is shown that the virial mass is
proportional to certain geometrical terms appearing in the Einstein field
equations and contributes to gravitational energy and that such a geometric
mass can be attributed to the virial mass discrepancy in a cluster of galaxies.
In addition, the galaxy rotation curves are studied by utilizing the concept of
conformal symmetry and notion of conformal Killing symmetry. The field
equations may then be obtained in an exact parametric form in terms of the
parameter representing the conformal factor. This provides the possibility of
studying the behavior of the angular velocity of a test particle moving in a
stable circular orbit. The tangential velocity can be derived as a function of
the conformal factor and integration constants, resulting in a constant value
at large radial distances. Relevant phenomenon such as the deflection of light
passing through a region where the rotation curves are flat and the radar echo
delay are also studied.Comment: 12 pages, 2 figures, to appear in PR
Spacetime in String Theory
We give a brief overview of the nature of spacetime emerging from string
theory. This is radically different from the familiar spacetime of Einstein's
relativity. At a perturbative level, the spacetime metric appears as ``coupling
constants" in a two dimensional quantum field theory. Nonperturbatively (with
certain boundary conditions), spacetime is not fundamental but must be
reconstructed from a holographic, dual theory.Comment: 20 pages; references adde
Quadratic Curvature Gravity with Second Order Trace and Massive Gravity Models in Three Dimensions
The quadratic curvature lagrangians having metric field equations with second
order trace are constructed relative to an orthonormal coframe. In
dimensions, pure quadratic curvature lagrangian having second order trace
constructed contains three free parameters in the most general case. The fourth
order field equations of some of these models, in arbitrary dimensions, are
cast in a particular form using the Schouten tensor. As a consequence, the
field equations for the New massive gravity theory are related to those of the
Topologically massive gravity. In particular, the conditions under which the
latter is "square root" of the former are presented.Comment: 24 pages, to appear in GR
Lectures on Cosmic Inflation and its Potential Stringy Realizations
These notes present a brief introduction to Hot Big Bang cosmology and Cosmic
Inflation, together with a selection of some recent attempts to embed inflation
into string theory. They provide a partial description of lectures presented in
courses at Dubrovnik in August 2006, at CERN in January 2007 and at Cargese in
August 2007. They are aimed at graduate students with a working knowledge of
quantum field theory, but who are unfamiliar with the details of cosmology or
of string theory.Comment: 68 pages, lectures given at Dubrovnik, Aug 2006; CERN, January 2007;
and Cargese, Aug 200
Does Fair Trade Deliver on Its Core Value Proposition? Effects on Income, Educational Attainment, and Health in Three Countries
Does Fair Trade Deliver on Its Core Value Proposition? Effects on Income, Educational Attainment, and Health in Three Countries
Alternative trade organizations (ATOs) based on philosophies of social justice and/or environmental well-being are establishing new channels of trade and marketing. Partisans promote ATOs as systems to transfer benefits from consumers in the wealthy northern hemisphere to producers in the poor southern hemisphere. The central public policy question is whether the well-being of poor agricultural producers in the southern hemisphere is actually being improved by fair-trade practices, or are consumers who buy products on this premise deceived? The research reported here partially answers the question whether participation in a fair-trade coffee marketing channel delivers benefits to smallscale producers in Latin America. The authors employ a survey methodology to compare TransFair USA (TF) cooperative participants and nonparticipating farmers in three countries on socioeconomic indicators of well-being. According to the analysis, the economic effects of fair-trade participation are unassailable; the effects on educational and health outcomes are uneven. However, TF cooperative participation positively affects educational attainment and the likelihood that a child is currently studying. The authors find positive health-related consequences of TF cooperative participation