5,524 research outputs found
An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra
Interferometric radius measurements provide a direct probe of the fundamental
parameters of M dwarfs, but is within reach for only a limited sample of
nearby, bright stars. We use interferometrically-measured radii, bolometric
luminosities, and effective temperatures to develop new empirical calibrations
based on low-resolution, near-infrared spectra. We use H-band Mg and Al
features to derive calibrations for effective temperature, radius and log
luminosity; the standard deviations in the residuals of our best fits are,
respectively, 73K, 0.027Rsun, and 0.049 dex (11% error on luminosity). These
relationships are valid for mid K to mid M dwarf stars, roughly corresponding
to temperatures between 3100 and 4800K. We apply our calibrations to M dwarfs
targeted by the MEarth transiting planet survey and to the cool Kepler Objects
of Interest (KOIs). We independently validate our calibrations by demonstrating
a clear relationship between our inferred parameters and the absolute K
magnitudes of the MEarth stars, and we identify objects with magnitudes too
bright for their estimated luminosities as candidate multiple systems. We also
use our inferred luminosities to address the applicability of near-infrared
metallicity calibrations to mid and late M dwarfs. The temperatures we infer
for the KOIs agree remarkably well with those from the literature; however, our
stellar radii are systematically larger than those presented in previous works
that derive radii from model isochrones. This results in a mean planet radius
that is 15% larger than one would infer using the stellar properties from
recent catalogs. Our results confirm those of previous in-depth studies of
Kepler-42, Kepler-45, and Kepler-186.Comment: Accepted to ApJ. Tables 4 and 5, and machine readable versions of
Tables 5 and 7 are available in the ApJ journal articl
Gauge/Gravity Duality and Some Applications
We discuss the AdS/CFT correspondence in which space-time emerges from an
interacting theory of D-branes and open strings. These ideas have a historical
continuity with QCD which is an interacting theory of quarks and gluons. In
particular we review the classic case of D3 branes and the non-conformal D1
brane system. We outline by some illustrative examples the calculations that
are enabled in a strongly coupled gauge theory by correspondence with dynamical
horizons in semi-classical gravity in one higher dimension. We also discuss
implications of the gauge-fluid/gravity correspondence for the information
paradox of black hole physics.Comment: 19 pages, 2 figures, Contribution to "Conference in Honor of Murray
Gell-Mann's 80th Birthday
The disability system and programs to promote employment for people with disabilities
This paper examines employment-focused interventions within the US disability system. Our review illustrates the challenges of developing and implementing these types of initiatives, despite substantial policy interest. Our findings indicate that none of the demonstrations we reviewed have the potential to lead to substantial caseload reductions that could reverse program growth. However, they can inform future designs, particularly the importance of customizing supports to very well-defined target populations
Generalized entropy and Noether charge
We find an expression for the generalized gravitational entropy of Hawking in
terms of Noether charge. As an example, the entropy of the Taub-Bolt spacetime
is calculated.Comment: 6 pages, revtex, reference correcte
Evidence of complex involvement of serotonergic genes with restrictive and binge purge subtypes of anorexia nervosa
Peer reviewedPreprin
Classical paths in systems of fermions
We implement in systems of fermions the formalism of pseudoclassical paths
that we recently developed for systems of bosons and show that quantum states
of fermionic fields can be described, in the Heisenberg picture, as linear
combinations of randomly distributed paths that do not interfere between
themselves and obey classical Dirac equations. Every physical observable is
assigned a time-dependent value on each path in a way that respects the
anticommutative algebra between quantum operators and we observe that these
values on paths do not necessarily satisfy the usual algebraic relations
between classical observables. We use these pseudoclassical paths to define the
dynamics of quantum fluctuations in systems of fermions and show that, as we
found for systems of bosons, the dynamics of fluctuations of a wide class of
observables that we call "collective" observables can be approximately
described in terms of classical stochastic concepts. Finally, we apply this
formalism to describe the dynamics of local fluctuations of globally conserved
fermion numbers.Comment: to appear in Pys. Rev.
The Effect of Density on Growth, Yield, and Reproduction of the Sea Scallop, Placopecten magellanicus: Final Report
Results from this project indicate that density in combination with settlement at depth in potentially marginal habitat contribute to reductions in growth, yield, and reproductive effort. In general, Study Area was not a contributing factor to the reductions in the three areas of scallop biological processes we measured. Scallops that settle in dense aggregations at varying depths may respond differentially to environmental conditions, food availability, habitat, and removals. (...)
Results from this study will enhance our knowledge of the scallop population with respect to conditions that diverge from expected biological processes. Results will also allow for better management and assessment of the resource when these situations occur in the future, as well as inform managers and stakeholders regarding expectations for scallops in dense aggregations
Environment as a Witness: Selective Proliferation of Information and Emergence of Objectivity in a Quantum Universe
We study the role of the information deposited in the environment of an open
quantum system in course of the decoherence process. Redundant spreading of
information -- the fact that some observables of the system can be
independently ``read-off'' from many distinct fragments of the environment --
is investigated as the key to effective objectivity, the essential ingredient
of ``classical reality''. This focus on the environment as a communication
channel through which observers learn about physical systems underscores
importance of quantum Darwinism -- selective proliferation of information about
``the fittest states'' chosen by the dynamics of decoherence at the expense of
their superpositions -- as redundancy imposes the existence of preferred
observables. We demonstrate that the only observables that can leave multiple
imprints in the environment are the familiar pointer observables singled out by
environment-induced superselection (einselection) for their predictability.
Many independent observers monitoring the environment will therefore agree on
properties of the system as they can only learn about preferred observables. In
this operational sense, the selective spreading of information leads to
appearance of an objective ``classical reality'' from within quantum substrate.Comment: New figures, to appear in PR
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