1,760 research outputs found
The Topology of Branching Universes
The purpose of this paper is to survey the possible topologies of branching
space-times, and, in particular, to refute the popular notion in the literature
that a branching space-time requires a non-Hausdorff topology
Scanning Tunneling Microscope-Induced Luminescence Spectroscopy on Semiconductor Heterostructures
Scanning tunneling microscope (STM)-induced luminescence is explored as a technique for the characterization of semiconductor quantum wells and quantum wire heterostructures. By injecting minority carriers into the cleaved cross section of these structures, luminescence excitation on a nanometer scale is demonstrated. Using spectrally resolved STM-induced luminescence for the tip placed at various positions across the cleaved heterostructure, it is possible to obtain local spectroscopic information on closely spaced quantum structures
Political institutions and debt crises
This paper shows that political institutions matter in explaining defaults on external and domestic debt obligations. We explore a large number of political and macroeconomic variables using a non-parametric technique to predict safety from default. The advantage of this technique is that it is able to identify patterns in the data that are not captured in standard probit analysis. We find that political factors matter, and do so in different ways for democratic and non-democratic regimes, and for domestic and external debt. In democracies, a parliamentary system or sufficient checks and balances almost guarantee the absence of default on external debt when economic fundamentals or liquidity are sufficiently strong. In dictatorships, high stability and tenure play a similar role for default on domestic debt
Cohomological tautness for Riemannian foliations
In this paper we present some new results on the tautness of Riemannian
foliations in their historical context. The first part of the paper gives a
short history of the problem. For a closed manifold, the tautness of a
Riemannian foliation can be characterized cohomologically. We extend this
cohomological characterization to a class of foliations which includes the
foliated strata of any singular Riemannian foliation of a closed manifold
Late time behaviour of the maximal slicing of the Schwarzschild black hole
A time-symmetric Cauchy slice of the extended Schwarzschild spacetime can be
evolved into a foliation of the -region of the spacetime by maximal
surfaces with the requirement that time runs equally fast at both spatial ends
of the manifold. This paper studies the behaviour of these slices in the limit
as proper time-at-infinity becomes arbitrarily large and gives an analytic
expression for the collapse of the lapse.Comment: 18 pages, Latex, no figure
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