6,490 research outputs found
ON THE RELATIONSHIPS BETWEEN SPATIAL CLUSTERING, INEQUALITY, AND ECONOMIC GROWTH IN THE UNITED STATES : 1969-2000
The literature on economic development has been divided as to the nature of the relationship between inequality and growth. Recent exploratory work in the field has provided evidence that the dynamic and spatial relationships between the two may be far more complicated than previously thought. This paper provides an spatial econometric specification for the analysis of economic growth, that allows for simultaneity as it relates to inequality. Furthermore, attention is given to the possible impacts of local clustering on the performance of individual economies in a global setting. The new methodology is applied to the US states from 1969–2000, where the counties are used for the local inequality and clustering estimates.ECONOMIC GROWTH, INEQUALITY, SIMULTANEITY, SPATIAL CLUSTERING
Spatial Clustering, Inequality and Income Convergence
This paper examines the relationship between spatial clustering and inequality at the county scale with overall state per capita income in the U.S. over the period 1969-2000. For each of the 48 coterminous states we examine measures of inequality and spatial clustering and explore how a state's overall income level may be influenced by, or influence, these measures. Our exploratory analysis utilizes the open- source package Space-Time Analysis of Regional Systems (STARS) to illustrate some new techniques for analyzing regional income dynamics. The results provide insight into the possible relationships between inequality, clustering and relative income levels, and generates a number of interesting avenues for future research.spatial clustering; spatial dependence; inequality; convergence; geocomputation
Closed Spaces in Cosmology
This paper deals with two aspects of relativistic cosmologies with closed
(compact and boundless) spatial sections. These spacetimes are based on the
theory of General Relativity, and admit a foliation into space sections S(t),
which are spacelike hypersurfaces satisfying the postulate of the closure of
space: each S(t) is a 3-dimensional, closed Riemannian manifold. The discussed
topics are: (1) A comparison, previously obtained, between Thurston's
geometries and Bianchi-Kantowski-Sachs metrics for such 3-manifolds is here
clarified and developed. (2) Some implications of global inhomogeneity for
locally homogeneous 3-spaces of constant curvature are analyzed from an
observational viewpoint.Comment: 20 pages, 6 figures, revised version of published paper. In version
2: several misprints corrected, 'redshifting' in figures improved. Version 3:
a few style corrections; couple of paragraphs in subsection 2.4 rewritten.
Version 4: figures 5 and 6 corrrecte
Mott Insulators of Ultracold Fermionic Alkaline Earth Atoms: Underconstrained Magnetism and Chiral Spin Liquid
We study Mott insulators of fermionic alkaline earth atoms, described by
Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to
SU(2) magnetism, more than two spins are required to form a singlet. On the
square lattice, the classical ground state is highly degenerate and magnetic
order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground
state with topological order and Abelian fractional statistics. We discuss its
experimental detection. Chiral spin liquids with non-Abelian anyons may also be
realizable with alkaline earth atoms.Comment: 4 pages, 2 figures, 1 table. Minor changes from v2. Final published
versio
Beyond the Spin Model Approximation for Ramsey Spectroscopy
Ramsey spectroscopy has become a powerful technique for probing
non-equilibrium dynamics of internal (pseudospin) degrees of freedom of
interacting systems. In many theoretical treatments, the key to understanding
the dynamics has been to assume the external (motional) degrees of freedom are
decoupled from the pseudospin degrees of freedom. Determining the validity of
this approximation -- known as the spin model approximation -- is complicated,
and has not been addressed in detail. Here we shed light in this direction by
calculating Ramsey dynamics exactly for two interacting spin-1/2 particles in a
harmonic trap. We focus on -wave-interacting fermions in quasi-one and
two-dimensional geometries. We find that in 1D the spin model assumption works
well over a wide range of experimentally-relevant conditions, but can fail at
time scales longer than those set by the mean interaction energy. Surprisingly,
in 2D a modified version of the spin model is exact to first order in the
interaction strength. This analysis is important for a correct interpretation
of Ramsey spectroscopy and has broad applications ranging from precision
measurements to quantum information and to fundamental probes of many-body
systems
Hanbury Brown-Twiss Interferometry for Fractional and Integer Mott Phases
Hanbury-Brown-Twiss interferometry (HBTI) is used to study integer and
fractionally filled Mott Insulator (MI) phases in period-2 optical
superlattices. In contrast to the quasimomentum distribution, this second order
interferometry pattern exhibits high contrast fringes in the it insulating
phases. Our detailed study of HBTI suggests that this interference pattern
signals the various superfluid-insulator transitions and therefore can be used
as a practical method to determine the phase diagram of the system. We find
that in the presence of a confining potential the insulating phases become
robust as they exist for a finite range of atom numbers. Furthermore, we show
that in the trapped case the HBTI interferogram signals the formation of the MI
domains and probes the shell structure of the system.Comment: 13 pages, 15 figure
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