356 research outputs found
Sen's Apples: Commitment, Agent Relativity and Social Norms
This paper examines Amartya Sen's notion of 'commitment' in light of Geoffrey Brennan's recent discussion thereof. Its aim is to elucidate one type of commitment which consists in following social norms. To this end, I discuss Sen's 'apples' example from his 'Rational fools' essay (section 2). In section 3, I draw some implications of commitments in Sen's work for the concept of 'agent relativity'. Section 4 discusses the distinctiveness of Sen's conception of human beings in their supposed ability to be able to bind themselves to following social norms at the expense of their own benefit.Commitment, Sen, Social Norm, Rational Choice Theory, Rationality, Sympathy, Altruism, Rule Following, Consequentialism
The capacity to choose: reformulating the concept of choice in economic theory
Despite being conceived as a âtheory of rational choiceâ, orthodox economics fails to ascribe to human beings the ability to choose in a meaningful sense, something philosophical approaches to economics have long noted and tried to remedy. Tony Lawsonâs critical realism is one attempt at a remedy. If, following Lawson, one conceives of choice as a âcapacityâ of human beings, critical realist analysis suggests a distinction between humansâ possession and their exercise of this capacity. If one can sustain this distinction, one should be able to distinguish cases in which agents actually exercise their capacity to choose from those in which they do not. Investigation of this distinction does not, however, lead to the desired distinction between such cases. Consequently, a reformulation of the notion of choice is required. An implication for economic theory â namely, the possibility of conceptualizing âexploitationâ â is discussed
Aristotle on justice in exchange: commensurability by fiat
This essay offers an interpretation of Aristotle\u27s remarks on the commensurability of goods in Book V of the Nicomachean Ethics. It explores the term âby hypothesisâ (áŒÎŸ áœÏοΞÎÏΔÏÏ) which Aristotle uses to describe the institution of currency through which commensurability is established. The term implies that Aristotle conceives the origins of currency to lie in a conscious act of stipulation rather than through a spontaneous process in which currency is established via the unintended consequences of individual action. In conclusion, contemporary theories of money are considered and it is asked with which Aristotleâs conception of money aligns most closely
Radio Galaxy Clustering at z~0.3
Radio galaxies are uniquely useful as probes of large-scale structure as
their uniform identification with giant elliptical galaxies out to high
redshift means that the evolution of their bias factor can be predicted. As the
initial stage in a project to study large-scale structure with radio galaxies
we have performed a small redshift survey, selecting 29 radio galaxies in the
range 0.19<z<0.45 from a contiguous 40 square degree area of sky. We detect
significant clustering within this sample. The amplitude of the two-point
correlation function we measure is consistent with no evolution from the local
(z<0.1) value. This is as expected in a model in which radio galaxy hosts form
at high redshift and thereafter obey a continuity equation, although the
signal:noise of the detection is too low to rule out other models. Larger
surveys out to z~1 should reveal the structures of superclusters at
intermediate redshifts and strongly constrain models for the evolution of
large-scale structure.Comment: 7 pages, 3 figures, accepted by ApJ Letter
The distribution and spread of the invasive alien common myna, Acridotheres tristis L. (Aves: Sturnidae), in southern Africa
The common myna is an Asian starling that has become established in many parts of the world outside of its native range due to accidental or deliberate introductions by humans. The South African population of this species originated from captive birds that escaped in Durban in 1902. A century later, the common myna has become abundant throughout much of South Africa and is considered to pose a serious threat to indigenous biodiversity. Preliminary observations suggest that the common myna's distribution is closely tied to that of humans, but empirical evidence for this hypothesis is lacking. We have investigated the relationships between common myna distribution, human population size and land-transformation values at a quarter-degree resolution in South Africa. Common mynas were found more frequently than expected by chance in areas with greater human population numbers and land-transformation values. We also investigated the spatial relationship between the bird's range and the locations of South Africa's protected areas at the quarter-degree scale. These results indicate that, although there is some overlap, the common myna distribution is not closely tied to the spatial arrangement of protected areas. We discuss the original introduction, establishment and rate of spread of the common myna in South Africa and neighbouring countries and contrast the current distribution with that presented in The Atlas of Southern African Birds. We also discuss the factors that affect the common myna's success and the consequences that invasion by this species is likely to have, specifically in protected areas
MAX 4 and MAX 5 CMB anisotropy measurement constraints on open and flat-Lambda CDM cosmogonies
We account for experimental and observational uncertainties in likelihood
analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4
and MAX 5 experiments. These analyses use CMB anisotropy spectra predicted in
open and spatially-flat Lambda cold dark matter cosmogonies. Amongst the models
considered, the combined MAX data set is most consistent with the CMB
anisotropy shape in Omega_0 ~ 0.1-0.2 open models and less so with that in old
(t_0 >~ 15 - 16 Gyr, i.e., low h), high baryon density (Omega_B >~ 0.0175/h^2),
low density (Omega_0 ~ 0.2 - 0.4), flat-Lambda models. The MAX data alone do
not rule out any of the models we consider at the 2-sigma level.
Model normalizations deduced from the combined MAX data are consistent with
those drawn from the UCSB South Pole 1994 data, except for the flat bandpower
model where MAX favours a higher normalization. The combined MAX data
normalization for open models with Omega_0 ~ 0.1-0.2 is higher than the upper
2-sigma value of the DMR normalization. The combined MAX data normalization for
old (low h), high baryon density, low-density flat-Lambda models is below the
lower 2-sigma value of the DMR normalization. Open models with Omega_0 ~
0.4-0.5 are not far from the shape most favoured by the MAX data, and for these
models the MAX and DMR normalizations overlap. The MAX and DMR normalizations
also overlap for Omega_0 = 1 and some higher h, lower Omega_B, low-density
flat-Lambda models.Comment: Latex, 37 pages, uses aasms4 styl
The Large-scale and Small-scale Clustering of Lyman-Break Galaxies at 3.5 < z< 5.5 from the GOODS survey
We report on the angular correlation function of Lyman-break galaxies (LBGs)
at z~4 and 5 from deep samples obtained from the Great Observatories Deep
Origins Survey (GOODS). Similar to LBGs at z~3, the shape of w(theta) of the
GOODS LBGs is well approximated by a power-law with slope beta~0.6 at angular
separation theta > 10 arcsec. The clustering strength of z~4, 5 LBGs also
depends on the rest-frame UV luminosity, with brighter galaxies more strongly
clustered than fainter ones, implying a general correlation between halos' mass
and LBGs' star-formation rate. At smaller separations, w(theta) of deep samples
significantly exceeds the extrapolation of the large-scale power-law fit,
implying enhanced spatial clustering at scales r < 1 Mpc. We also find that
bright LBGs statistically have more faint companions on scales theta < 20
arcsec than fainter ones, showing that the enhanced small-scale clustering is
very likely due to sub-structure, namely the fact that massive halos can host
multiple galaxies. A simple model for the halo occupation distribution and the
CDM halo mass function reproduce well the observed w(theta). The scaling
relationship of the clustering strength with volume density and with redshift
is quantitatively consistent with that of CDM halos. A comparison of the
clustering strength of three samples of equal luminosity limit at z ~ 3, 4 and
5 shows that the LBGs at z~5 are hosted in halos about one order of magnitude
less massive than those in the lower redshift bins, suggesting that
star-formation was more efficient at higher-redshift.Comment: replaced with the version accepted for publication in ApJ. 46 pages,
10 figures; minor changes to text, one subsection adde
A galaxy-halo model of large-scale structure
We present a new, galaxy-halo model of large-scale structure, in which the
galaxies entering a given sample are the fundamental objects. Haloes attach to
galaxies, in contrast to the standard halo model, in which galaxies attach to
haloes. The galaxy-halo model pertains mainly to the relationships between the
power spectra of galaxies and mass, and their cross-power spectrum. With
surprisingly little input, an intuition-aiding approximation to the
galaxy-matter cross-correlation coefficient R(k) emerges, in terms of the halo
mass dispersion. This approximation seems valid to mildly non-linear scales (k
< ~3 h/Mpc), allowing measurement of the bias and the matter power spectrum
from measurements of the galaxy and galaxy-matter power spectra (or correlation
functions). This is especially relevant given the recent advances in precision
in measurements of the galaxy-matter correlation function from weak
gravitational lensing. The galaxy-halo model also addresses the issue of
interpreting the galaxy-matter correlation function as an average halo density
profile, and provides a simple description of galaxy bias as a function of
scale.Comment: 13 pages, 9 figures, submitted to MNRAS. Minor changes, suggested by
refere
Massive Ellipticals at High Redshift: NICMOS Imaging of Z~1 Radio Galaxies
We present deep, continuum images of eleven high-redshift (0.811 < z < 1.875)
3CR radio galaxies observed with NICMOS. Our images probe the rest-frame
optical light where stars are expected to dominate the galaxy luminosity. The
rest-frame UV light of eight of these galaxies demonstrates the well-known
``alignment effect''. Most of the radio galaxies have rounder, more symmetric
morphologies at rest-frame optical wavelengths. Here we show the most direct
evidence that in most cases the stellar hosts are normal elliptical galaxies
with de Vaucouleurs law light profiles. For a few galaxies very faint traces of
the UV-bright aligned component are also visible in the infrared images. We
derive both the effective radius and surface-brightness for nine of eleven
sample galaxies by fitting surface-brightness models to them. We find their
sizes are similar to those of local FRII radio source hosts and are in general
larger than other local galaxies. The derived host galaxy luminosities are very
high and lie at the bright end of luminosity functions constructed at similar
redshifts. The galaxies in our sample are also brighter than the rest-frame
size--surface-brightness locus defined by the low-redshift sources. Passive
evolution roughly aligns the z ~ 1 galaxies with the low-redshift samples. The
optical host is sometimes centered on a local minimum in the rest-frame UV
emission, suggesting the presence of substantial dust obscuration. We also see
good evidence of nuclear point sources in three galaxies. Overall, our results
are consistent with the hypothesis that these galaxies have already formed the
bulk of their stars at redshifts greater than z >~ 2, and that the AGN
phenomenon takes place within otherwise normal, perhaps passively evolving,
galaxies. (abridged)Comment: 28 pages, 14 figures, accepted to ApJ. Uses AASTEX and emulateapj
Straightening the Density-Displacement Relation with a Logarithmic Transform
We investigate the use of a logarithmic density variable in estimating the
Lagrangian displacement field, motivated by the success of a logarithmic
transformation in restoring information to the matter power spectrum. The
logarithmic relation is an extension of the linear relation, motivated by the
continuity equation, in which the density field is assumed to be proportional
to the divergence of the displacement field; we compare the linear and
logarithmic relations by measuring both of these fields directly in a
cosmological N-body simulation. The relative success of the logarithmic and
linear relations depends on the scale at which the density field is smoothed.
Thus we explore several ways of measuring the density field, including
Cloud-In-Cell smoothing, adaptive smoothing, and the (scale-independent)
Delaunay tessellation, and we use both a Fourier space and a geometrical
tessellation approach to measuring the divergence. We find that the relation
between the divergence of the displacement field and the density is
significantly tighter with a logarithmic density variable, especially at low
redshifts and for very small (~2 Mpc/h) smoothing scales. We find that the
grid-based methods are more reliable than the tessellation-based method of
calculating both the density and the divergence fields, though in both cases
the logarithmic relation works better in the appropriate regime, which
corresponds to nonlinear scales for the grid-based methods and low densities
for the tessellation-based method.Comment: 6 pages, 3 figures, accepted to Ap
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