12,109 research outputs found
The abortion-crime link: evidence from England and Wales
We use panel data from 1983 to 1997 for the 42 police force areas in England and Wales to test the hypothesis that legalizing abortion contributes to lower crime rates. We provide an advance on previous work by focusing on the impact of possible endogeneity of effective abortion rates with respect to crime. Our use of U.K. data allows us to exploit regional differences in the provision of free abortions to identify abortion rates. When we use a similar model and estimation methodology, we are able to replicate the negative association between abortion rates and reported crime found by Donohue and Levitt for the U.S. However, when we allow for the potential endogeneity of effective abortion rates with respect to crime, we find no clear connection between the two.
Factorization of correlations in two-dimensional percolation on the plane and torus
Recently, Delfino and Viti have examined the factorization of the three-point
density correlation function P_3 at the percolation point in terms of the
two-point density correlation functions P_2. According to conformal invariance,
this factorization is exact on the infinite plane, such that the ratio R(z_1,
z_2, z_3) = P_3(z_1, z_2, z_3) [P_2(z_1, z_2) P_2(z_1, z_3) P_2(z_2,
z_3)]^{1/2} is not only universal but also a constant, independent of the z_i,
and in fact an operator product expansion (OPE) coefficient. Delfino and Viti
analytically calculate its value (1.022013...) for percolation, in agreement
with the numerical value 1.022 found previously in a study of R on the
conformally equivalent cylinder. In this paper we confirm the factorization on
the plane numerically using periodic lattices (tori) of very large size, which
locally approximate a plane. We also investigate the general behavior of R on
the torus, and find a minimum value of R approx. 1.0132 when the three points
are maximally separated. In addition, we present a simplified expression for R
on the plane as a function of the SLE parameter kappa.Comment: Small corrections (final version). In press, J. Phys.
The Top Triangle Moose
We introduce a deconstructed model that incorporates both Higgsless and
top-color mechanisms. The model alleviates the typical tension in Higgsless
models between obtaining the correct top quark mass and keeping delta-rho
small. It does so by singling out the top quark mass generation as arising from
a Yukawa coupling to an effective top-Higgs which develops a small vacuum
expectation value, while electroweak symmetry breaking results largely from a
Higgsless mechanism. As a result, the heavy partners of the SM fermions can be
light enough to be seen at the LHC.Comment: To appear in proceedings of SCGT09, Nagoya, Japan. 5 page
Deconstructed Higgsless Models at LHC: The Top Triangle Moose
We describe a deconstructed Higgsless model in which electroweak symmetry
breaking results largely from a Higgsless mechanism while the top quark mass is
generated by a topcolor mechanism. The top quark mass arises from a Yukawa
coupling to an effective top-Higgs which develops a small vacuum expectation
value. Both the heavy partners of the electoweak gauge bosons and those for the
SM fermions can be light enough to be visible at LHC.Comment: 5 pages, 3 figures; from the Proceedings of the 2010 Rencontres de
Bloi
Influence of chopped laser light onto the electronic transport through atomic-sized contacts
This article reports on the influence of laser irradiation onto the
electrical conductance of gold nanocontacts established with the mechanically
controllable breakjunction technique (MCB). We concentrate here on the study of
reversible conductance changes which can be as high as 200%. We investigate the
dependence on the initial conductance of the contacts, the wavelength, the
intensity and position of the laser spot with respect to the sample. Under most
conditions an enhancement of the conductance is observed. We discuss several
physical mechanisms which might contribute to the observed effect including
thermal expansion, rectification and photon-assisted transport. We conclude
that thermal expansion is not the dominating one.Comment: 20 pages with 7 figures; conference contribution on the 9th near
field optics conference 2006 in Lausanne, Switzerland; accepted by the
Journal of Microscop
Low-Energy Effective Theory, Unitarity, and Non-Decoupling Behavior in a Model with Heavy Higgs-Triplet Fields
We discuss the properties of a model incorporating both a scalar electroweak
Higgs doublet and an electroweak Higgs triplet. We construct the low-energy
effective theory for the light Higgs-doublet in the limit of small (but
nonzero) deviations in the rho parameter from one, a limit in which the triplet
states become heavy. For small deviations in the rho parameter from one,
perturbative unitarity of WW scattering breaks down at a scale inversely
proportional to the renormalized vacuum expectation value of the triplet field
(or, equivalently, inversely proportional to the square-root of the deviation
of the rho parameter from one). This result imposes an upper limit on the
mass-scale of the heavy triplet bosons in a perturbative theory; we show that
this upper bound is consistent with dimensional analysis in the low-energy
effective theory. Recent articles have shown that the triplet bosons do not
decouple, in the sense that deviations in the rho parameter from one do not
necessarily vanish at one-loop in the limit of large triplet mass. We clarify
that, despite the non-decoupling behavior of the Higgs-triplet, this model does
not violate the decoupling theorem since it incorporates a large dimensionful
coupling. Nonetheless, we show that if the triplet-Higgs boson masses are of
order the GUT scale, perturbative consistency of the theory requires the
(properly renormalized) Higgs-triplet vacuum expectation value to be so small
as to be irrelevant for electroweak phenomenology.Comment: Revtex, 11 pages, 7 eps figures included; references updated and
three footnotes adde
Probing the Atmospheres of Planets Orbiting Microlensed Stars via Polarization Variability
We present a new method to identify and probe planetary companions of stars
in the Galactic Bulge and Magellanic Clouds using gravitational microlensing.
While spectroscopic studies of these planets is well beyond current
observational techniques, monitoring polarization fluctuations during high
magnification events induced by binary microlensing events will probe the
composition of the planetary atmospheres, an observation which otherwise is
currently unattainable even for nearby planetary systems.Comment: 7 pages, 2 figures. To appear in Astrophysical Journal Letter
Photoluminescence Detected Doublet Structure in the Integer and Fractional Quantum Hall Regime
We present here the results of polarized magneto-photoluminescence
measurements on a high mobility single-heterojunction. The presence of a
doublet structure over a large magnetic field range (2>nu>1/6) is interpreted
as possible evidence for the existence of a magneto-roton minima of the charged
density waves. This is understood as an indication of strong electronic
correlation even in the case of the IQHE limit.Comment: submitted to Solid State Communication
The mission oriented terminal area simulation facility
The Mission Oriented Terminal Area Simulation (MOTAS) was developed to provide an ATC environment in which flight management and flight operations research studies can be conducted with a high degree of realism. This facility provides a flexible and comprehensive simulation of the airborne, ground-based and communication aspects of the airport terminal area environment. Major elements of the simulation are: an airport terminal area environment model, two air traffic controller stations, several aircraft models and simulator cockpits, four pseudo pilot stations, and a realistic air-ground communications network. MOTAS has been used for one study with the DC-9 simulator and a series of data link studies are planned in the near future
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