3,082 research outputs found
An observational study of race and gender homophily in nursery children
Homophily (the preference for similar others) is a commonplace feature of social life. In this observational study, we recorded association patterns (based on spatial proximity or verbal or physical interaction) among children aged 3-4 years old during unstructured playtime in a university nursery. A basic social network analysis and a quadratic assignment procedure revealed gender and race to be significant predictive factors of social interaction, with girls seemingly displaying more racial homophily than boys. Age, parent occupation and number of siblings did not predict interaction patterns
Toward an understanding of short distance repulsions among baryons in QCD -- NBS wave functions and operator product expansion --
We report on our recent attempts to determine the short distance behaviors of
general 2-baryon and 3-baryon forces, which are defined from the
Nambu-Bethe-Salpeter(NBS) wave function, by using the operator product
expansion and a renormalization group analysis in QCD. We have found that the
repulsion at short distance increases as the number of valence quarks increases
or when the number of different flavors involved decreases. This global
tendency suggests a Pauli suppression principle among quark fields at work.Comment: 14 pages, add two exmples in sect.3.4, a version accepted for
Progress of Theoretical Physic
Push it to the limit: Local Group constraints on high-redshift stellar mass functions for Mstar > 10^5 Msun
We constrain the evolution of the galaxy stellar mass function from 2 < z < 5
for galaxies with stellar masses as low as 10^5 Msun by combining star
formation histories of Milky Way satellite galaxies derived from deep Hubble
Space Telescope observations with merger trees from the ELVIS suite of N-body
simulations. This approach extends our understanding more than two orders of
magnitude lower in stellar mass than is currently possible by direct imaging.
We find the faint end slopes of the mass functions to be alpha=
-1.42(+0.07/-0.05) at z = 2 and alpha = -1.57^(+0.06/-0.06) at z = 5, and show
the slope only weakly evolves from z = 5 to z = 0. Our findings are in stark
contrast to a number of direct detection studies that suggest slopes as steep
as alpha = -1.9 at these epochs. Such a steep slope would result in an order of
magnitude too many luminous Milky Way satellites in a mass regime that is
observationally complete (Mstar > 2*10^5 Msun at z = 0). The most recent
studies from ZFOURGE and CANDELS also suggest flatter faint end slopes that are
consistent with our results, but with a lower degree of precision. This work
illustrates the strong connections between low and high-z observations when
viewed through the lens of LCDM numerical simulations
The Lattice Parameter in Domain Wall QCD
We evaluate the ratio of the scale parameter in domain wall QCD to
the one in the continuum theory at one loop level incorporating the effect of
massless quarks. We show that the Pauli-Villars regulator is required to
subtract the unphysical massive fermion modes which emerge in the fermion loop
contributions to the gluon self energy. Detailed results are presented as a
function of the domain wall height .Comment: 16 pages, 1 figure as eps-file, some references adde
The Local Group: The Ultimate Deep Field
Near-field cosmology -- using detailed observations of the Local Group and
its environs to study wide-ranging questions in galaxy formation and dark
matter physics -- has become a mature and rich field over the past decade.
There are lingering concerns, however, that the relatively small size of the
present-day Local Group ( Mpc diameter) imposes insurmountable
sample-variance uncertainties, limiting its broader utility. We consider the
region spanned by the Local Group's progenitors at earlier times and show that
it reaches co-moving Mpc in linear size (a volume of ) at . This size at early cosmic epochs is large enough
to be representative in terms of the matter density and counts of dark matter
halos with . The Local
Group's stellar fossil record traces the cosmic evolution of galaxies with
(reaching
at ) over a region that is comparable to or larger than
the Hubble Ultra-Deep Field (HUDF) for the entire history of the Universe. It
is highly complementary to the HUDF, as it probes much fainter galaxies but
does not contain the intrinsically rarer, brighter sources that are detectable
in the HUDF. Archaeological studies in the Local Group also provide the ability
to trace the evolution of individual galaxies across time as opposed to
evaluating statistical connections between temporally distinct populations. In
the JWST era, resolved stellar populations will probe regions larger than the
HUDF and any deep JWST fields, further enhancing the value of near-field
cosmology.Comment: 6 pages, 5 figures; MNRAS Letters, in pres
Perturbative calculation of improvement coefficients to O(g^2a) for bilinear quark operators in lattice QCD
We calculate the O(g^2 a) mixing coefficients of bilinear quark operators in
lattice QCD using a standard perturbative evaluation of on-shell Green's
functions. Our results for the plaquette gluon action are in agreement with
those previously obtained with the Schr\"odinger functional method. The
coefficients are also calculated for a class of improved gluon actions having
six-link terms.Comment: 14 pages, REVTe
International comparison of health care carbon footprints
Climate change confronts the health care sector with a dual challenge. Accumulating climate impacts are putting an increased burden on the service provision of already stressed health care systems in many regions of the world. At the same time, the Paris agreement requires rapid emission reductions in all sectors of the global economy to stay well below the 2 °C target. This study shows that in OECD countries, China, and India, health care on average accounts for 5% of the national CO2 footprint making the sector comparable in importance to the food sector. Some countries have seen reduced CO2 emissions related to health care despite growing expenditures since 2000, mirroring their economy wide emission trends. The average per capita health carbon footprint across the country sample in 2014 was 0.6 tCO2, varying between 1.51 tCO2/cap in the US and 0.06 tCO2/cap in India. A statistical analysis shows that the carbon intensity of the domestic energy system, the energy intensity of the domestic economy, and health care expenditure together explain half of the variance in per capita health carbon footprints. Our results indicate that important leverage points exist inside and outside the health sector. We discuss our findings in the context of the existing literature on the potentials and challenges of reducing GHG emissions in the health and energy sector.Austrian Climate Research ProgramPeer Reviewe
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