49,855 research outputs found
Holographic renormalisation group flows and renormalisation from a Wilsonian perspective
From the Wilsonian point of view, renormalisable theories are understood as
submanifolds in theory space emanating from a particular fixed point under
renormalisation group evolution. We show how this picture precisely applies to
their gravity duals. We investigate the Hamilton-Jacobi equation satisfied by
the Wilson action and find the corresponding fixed points and their
eigendeformations, which have a diagonal evolution close to the fixed points.
The relevant eigendeformations are used to construct renormalised theories. We
explore the relation of this formalism with holographic renormalisation. We
also discuss different renormalisation schemes and show that the solutions to
the gravity equations of motion can be used as renormalised couplings that
parametrise the renormalised theories. This provides a transparent connection
between holographic renormalisation group flows in the Wilsonian and
non-Wilsonian approaches. The general results are illustrated by explicit
calculations in an interacting scalar theory in AdS space.Comment: 63 pages. Minor changes and references added. Matches JHEP versio
Do Tougher Licensing Provisions Limit Occupational Entry? The Case of Dentistry
The effect of licensing as a mechanism to control entry into occupations has been a neglected area of both regulation and labor market research. This study examines the role of occupational licensing for entry into dentistry, an occupation with standards that vary by state. Our research first closely replicates Freeman's previous work on labor market cobwebs by employing national data to examine purely market phenomena in the determination of training for the dental profession. We subsequently approximate the government barrier to practice in the profession by adding a weighted average state examination pass rate to the previous model. Next, we employ pooled cross-section time series analysis to explore market determinants of professional entry with state level data. Finally, these results are supplemented by measures of statutory and pass rate entry restrictiveness. Our most consistent evidence suggests that a higher state licensing failure rate deters entry into dental practice.
Epigenetic modification of the oxytocin receptor gene is associated with emotion processing in the infant brain
The neural capacity to discriminate between emotions emerges early in development, though little is known about specific factors that contribute to variability in this vital skill during infancy. In adults, DNA methylation of the oxytocin receptor gene (OXTRm) is an epigenetic modification that is variable, predictive of gene expression, and has been linked to autism spectrum disorder and the neural response to social cues. It is unknown whether OXTRm is variable in infants, and whether it is predictive of early social function. Implementing a developmental neuroimaging epigenetics approach in a large sample of infants (N = 98), we examined whether OXTRm is associated with neural responses to emotional expressions. OXTRm was assessed at 5 months of age. At 7 months of age, infants viewed happy, angry, and fearful faces while functional near-infrared spectroscopy was recorded. We observed that OXTRm shows considerable variability among infants. Critically, infants with higher OXTRm show enhanced responses to anger and fear and attenuated responses to happiness in right inferior frontal cortex, a region implicated in emotion processing through action-perception coupling. Findings support models emphasizing oxytocin's role in modulating neural response to emotion and identify OXTRm as an epigenetic mark contributing to early brain function
Optimization of the derivative expansion in the nonperturbative renormalization group
We study the optimization of nonperturbative renormalization group equations
truncated both in fields and derivatives. On the example of the Ising model in
three dimensions, we show that the Principle of Minimal Sensitivity can be
unambiguously implemented at order of the derivative expansion.
This approach allows us to select optimized cut-off functions and to improve
the accuracy of the critical exponents and . The convergence of the
field expansion is also analyzed. We show in particular that its optimization
does not coincide with optimization of the accuracy of the critical exponents.Comment: 13 pages, 9 PS figures, published versio
Adaptive Optics Observations of the Galactic Center Young Stars
Adaptive Optics observations have dramatically improved the quality and
versatility of high angular resolution measurements of the center of our
Galaxy. In this paper, we quantify the quality of our Adaptive Optics
observations and report on the astrometric precision for the young stellar
population that appears to reside in a stellar disk structure in the central
parsec. We show that with our improved astrometry and a 16 year baseline,
including 10 years of speckle and 6 years of laser guide star AO imaging, we
reliably detect accelerations in the plane of the sky as small as 70
microarcsec/yr/yr (~2.5 km/s/yr) and out to a projected radius from the
supermassive black hole of 1.5" (~0.06 pc). With an increase in sensitivity to
accelerations by a factor of ~6 over our previous efforts, we are able to
directly probe the kinematic structure of the young stellar disk, which appears
to have an inner radius of 0.8". We find that candidate disk members are on
eccentric orbits, with a mean eccentricity of = 0.30 +/- 0.07. Such
eccentricities cannot be explained by the relaxation of a circular disk with a
normal initial mass function, which suggests the existence of a top-heavy IMF
or formation in an initially eccentric disk.Comment: 7 pages, 4 figures, SPIE Astronomical Telescopes and Instrumentation
201
The Effect of Negative-Energy Shells on the Schwarzschild Black Hole
We construct Penrose diagrams for Schwarzschild spacetimes joined by massless
shells of matter, in the process correcting minor flaws in the similar diagrams
drawn by Dray and 't Hooft, and confirming their result that such shells
generate a horizon shift. We then consider shells with negative energy density,
showing that the horizon shift in this case allows for travel between the
heretofore causally separated exterior regions of the Schwarzschild geometry.
These drawing techniques are then used to investigate the properties of
successive shells, joining multiple Schwarzschild regions. Again, the presence
of negative-energy shells leads to a causal connection between the exterior
regions, even in (some) cases with two successive shells of equal but opposite
total energy.Comment: 12 pages, 10 figure
Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6–0.4 (W31C), W49N, and W51
We report the detection of the ground state N, J = 1, 3/2 → 1, 1/2 doublet of the methylidyne radical CH at ~532 GHz and ~536 GHz with
the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6–0.4 (W31C), W49N, and W51. While the molecular
cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption
against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles,
with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH,
CN, and HCO^+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO^+ deviate from the mean trends,
giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better
tracers, with [CCH]/[H_2] ~3.2 ± 1.1 × 10^(−8). The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter
along the lines of sight has gas densities n_H = n(H) + 2n(H_2) ranging between 100 and 1000 cm^(−3)
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