2,494,782 research outputs found
Poverty lines across the world
National poverty lines vary greatly across the world, from under 40 (at 2005 purchasing power parity). What accounts for these huge differences, and can they be understood within a common global definition of poverty? For all except the poorest countries, the absolute, nutrition-based, poverty lines found in practice tend to behave more like relative lines, in that they are higher for richer countries. Prevailing methods of setting absolute lines allow ample scope for such relativity, even when nutritional norms are common across countries. Both macro data on poverty lines across the world and micro data on subjective perceptions of poverty are consistent with a weak form of relativity that combines absolute consumption needs with social-inclusion needs that are positive for the poorest but rise with a country’s mean consumption. The strong form of relativism favored by some developed countries -- whereby the line is set at a fixed proportion of the mean -- emerges as the limiting case for very rich countries.Rural Poverty Reduction,Regional Economic Development,Achieving Shared Growth,Poverty Lines
Exploring the action landscape with trial world-lines
The Hamilton action principle, also known as the principle of least action,
and Lagrange equations are an integral part of advanced undergraduate
mechanics. At present, substantial efforts are ongoing to suitably incorporate
the action principle in introductory physics courses. Although the Hamilton
principle is oft stated as "the action for any nearby trial world-line is
greater than the action for the classical world-line", the landscape of action
in the space of world-lines is rarely explored. Here, for three common problems
in introductory physics - a free particle, a uniformly accelerating particle,
and a simple harmonic oscillator - we present families of trial world-lines,
characterized by a few parameters, that evolve continuously from their
respective classical world-lines. With explicit analytical expressions
available for the action, they permit a graphical visualization of the action
landscape in the space of nearby world-lines. Although these trial world-lines
form only a subset of the space of all nearby world-lines, they provide a
pedagogical tool that complements the traditional Lagrange equation approach
and is well-suited for advanced undergraduate students.Comment: 9 pages, 6 figures, significant structural revisio
The Real Meaning of Complex Minkowski-Space World-Lines
In connection with the study of shear-free null geodesics in Minkowski space,
we investigate the real geometric effects in real Minkowski space that are
induced by and associated with complex world-lines in complex Minkowski space.
It was already known, in a formal manner, that complex analytic curves in
complex Minkowski space induce shear-free null geodesic congruences. Here we
look at the direct geometric connections of the complex line and the real
structures. Among other items, we show, in particular, how a complex world-line
projects into the real Minkowski space in the form of a real shear-free null
geodesic congruence.Comment: 16 page
Quantum logic as superbraids of entangled qubit world lines
Presented is a topological representation of quantum logic that views
entangled qubit spacetime histories (or qubit world lines) as a generalized
braid, referred to as a superbraid. The crossing of world lines is purely
quantum in nature, most conveniently expressed analytically with
ladder-operator-based quantum gates. At a crossing, independent world lines can
become entangled. Complicated superbraids are systematically reduced by
recursively applying novel quantum skein relations. If the superbraid is closed
(e.g. representing quantum circuits with closed-loop feedback, quantum lattice
gas algorithms, loop or vacuum diagrams in quantum field theory), then one can
decompose the resulting superlink into an entangled superposition of classical
links. In turn, for each member link, one can compute a link invariant, e.g.
the Jones polynomial. Thus, a superlink possesses a unique link invariant
expressed as an entangled superposition of classical link invariants.Comment: 4 page
Motion of a Vector Particle in a Curved Spacetime. II First Order Correction to a Geodesic in a Schwarzschild Background
The influence of spin on a photon's motion in a Schwarzschild and FRW
spacetimes is studied. The first order correction to the geodesic motion is
found. It is shown that unlike the world-lines of spinless particles, the
photons world-lines do not lie in a plane.Comment: 14 pages, LaTeX2e, second paper in the series (the first one:
gr-qc/0110067), replaced with typos and style corrected version, accepted in
MPL
Lorentz contraction and accelerated systems
The paper discusses the problem of the Lorentz contraction in accelerated
systems, in the context of the special theory of relativity. Equal proper
accelerations along different world lines are considered, showing the
differences arising when the world lines correspond to physically connected or
disconnected objects. In all cases the special theory of relativity proves to
be completely self-consistentComment: 7 pages, LaTeX, to be published in European Journal of Physic
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