508 research outputs found
The pre-inflationary vacuum in the cosmic microwave background
We consider the effects on the primordial power spectrum of a period of
radiation-dominated expansion prior to the inflationary era. If inflation lasts
a total of only 60 e-folds or so, the boundary condition for quantum modes
cannot be taken in the short-wavelength limit as in the standard perturbation
calculation. Instead, the boundary condition is set by the vacuum state of the
prior radiation-dominated epoch, which only corresponds to the inflationary
vacuum state in the ultraviolet limit. This altered vacuum state results in a
modulation of the inflationary power spectrum. We calculate the modification to
a best-fit model from the WMAP3 data set, and find that power is suppressed at
large scales. The modified power spectrum is favored only very weakly by the
data.Comment: 4 pages, 2 figures, references added. Version submitted to PRL. (v3:
9 pages, 4 figures, detailed justification of Eq. 11 of v2. Version accepted
for publication by PRD.
Photometric Decomposition of Barred Galaxies
We present a non-parametric method for decomposition of the light of disk
galaxies into disk, bulge and bar components. We have developed and tested the
method on a sample of 68 disk galaxies for which we have acquired I-band
photometry. The separation of disk and bar light relies on the single
assumption that the bar is a straight feature with a different ellipticity and
position angle from that of the projected disk. We here present the basic
method, but recognise that it can be significantly refined. We identify bars in
only 47% of the more nearly face-on galaxies in our sample. The fraction of
light in the bar has a broad range from 1.3% to 40% of the total galaxy light.
If low-luminosity galaxies have more dominant halos, and if halos contribute to
bar stability, the luminosity functions of barred and unbarred galaxies should
differ markedly; while our sample is small, we find only a slight difference of
low significance.Comment: Accepted to appear in AJ, 36 pages, 9 figures, full on-line figures
available at http://www.physics.rutgers.edu/~sellwood/Reese.htm
Intensive Statin Therapy Is Associated With a Decrease in Adverse Events and Death Following Carotid Revascularization
Tensors, non-Gaussianities, and the future of potential reconstruction
We present projections for reconstruction of the inflationary potential
expected from ESA's upcoming Planck Surveyor CMB mission. We focus on the
effects that tensor perturbations and the presence of non-Gaussianities have on
reconstruction efforts in the context of non-canonical inflation models. We
consider potential constraints for different combinations of
detection/null-detection of tensors and non-Gaussianities. We perform Markov
Chain Monte Carlo and flow analyses on a simulated Planck-precision data set to
obtain constraints. We find that a failure to detect non-Gaussianities
precludes a successful inversion of the primordial power spectrum, greatly
affecting uncertainties, even in the presence of a tensor detection. In the
absence of a tensor detection, while unable to determine the energy scale of
inflation, an observable level of non-Gaussianities provides correlations
between the errors of the potential parameters, suggesting that constraints
might be improved for suitable combinations of parameters. Constraints are
optimized for a positive detection of both tensors and non-Gaussianities.Comment: 12 pages, 5 figures, LaTeX; V2: version submitted to JCA
National trends in utilization, mortality, and survival after repair of type B aortic dissection in the Medicare population
ObjectiveThe application of thoracic endovascular aortic repair (TEVAR) has changed treatment paradigms for thoracic aortic disease. We sought to better define specific treatment patterns and outcomes for type B aortic dissection treated with TEVAR or open surgical repair (OSR).MethodsMedicare patients undergoing type B thoracic aortic dissection repair (2000-2010) were identified by use of a validated International Classification of Diseases, Ninth Revision diagnostic and procedural code–based algorithm. Trends in utilization were analyzed by procedure type (OSR vs TEVAR), and patterns in patient characteristics and outcomes were examined.ResultsTotal thoracic aortic dissection repairs increased by 21% between 2000 and 2010 (2.5 to 3 per 100,000 Medicare patients; P = .001). A concomitant increase in TEVAR was seen during the same interval (0.03 to 0.8 per 100,000; P < .001). By 2010, TEVAR represented 27% of all repairs. TEVAR patients had higher rates of comorbid congestive heart failure (12% vs 9%; P < .001), chronic obstructive pulmonary disease (17% vs 10%; P < .001), diabetes (8% vs 5%; P < .001), and chronic renal failure (8% vs 3%; P < .001) compared with OSR patients. For all repairs, patient comorbidity burden increased over time (mean Charlson comorbidity score of 0.79 in 2000, 1.10 in 2010; P = .04). During this same interval, in-hospital mortality rates declined from 47% to 23% (P < .001), a trend seen in both TEVAR and OSR patients. Whereas in-hospital mortality rates and 3-year survival were similar between patients selected for TEVAR and OSR, there was a trend toward women having slightly lower 3-year survival after TEVAR (60% women vs 63% men; P = .07).ConclusionsSurgical treatment of type B aortic dissection has increased over time, reflecting an increase in the utilization of TEVAR. Overall, type B dissection repairs are currently performed at lower mortality risk in patients with more comorbidities
Even More Rapidly Rotating Pre-main-sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations
Using K2, we recently discovered a new type of periodic photometric variability while analyzing the light curves of members of Upper Sco. The 23 exemplars of this new variability type are all mid-M dwarfs, with short rotation periods. Their phased light curves have one or more broad flux dips or multiple arcuate structures which are not explicable by photospheric spots or eclipses by solid bodies. Now, using Transiting Exoplanet Survey Satellite data, we have searched for this type of variability in the other major sections of Sco-Cen, Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC). We identify 28 stars with the same light curve morphologies. We find no obvious difference between the Upper Sco and the UCL/LCC representatives of this class in terms of their light curve morphologies, periods, or variability amplitudes. The physical mechanism behind this variability is unknown, but as a possible clue we show that the rapidly rotating mid-M dwarfs in UCL/LCC have slightly different colors from the slowly rotating M dwarfs—they either have a blue excess (hot spots?) or a red excess (warm dust?). One of the newly identified stars (TIC242407571) has a very striking light curve morphology. At about every 0.05 in phase are features that resemble icicles. The icicles arise because there is a second periodic system whose main feature is a broad flux dip. Using a toy model, we show that the observed light curve morphology results only if the ratio of the two periods and the flux-dip width are carefully arranged
Even More Rapidly Rotating Pre-main-sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations
Using K2, we recently discovered a new type of periodic photometric variability while analyzing the light curves of members of Upper Sco. The 23 exemplars of this new variability type are all mid-M dwarfs, with short rotation periods. Their phased light curves have one or more broad flux dips or multiple arcuate structures which are not explicable by photospheric spots or eclipses by solid bodies. Now, using Transiting Exoplanet Survey Satellite data, we have searched for this type of variability in the other major sections of Sco-Cen, Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC). We identify 28 stars with the same light curve morphologies. We find no obvious difference between the Upper Sco and the UCL/LCC representatives of this class in terms of their light curve morphologies, periods, or variability amplitudes. The physical mechanism behind this variability is unknown, but as a possible clue we show that the rapidly rotating mid-M dwarfs in UCL/LCC have slightly different colors from the slowly rotating M dwarfs—they either have a blue excess (hot spots?) or a red excess (warm dust?). One of the newly identified stars (TIC242407571) has a very striking light curve morphology. At about every 0.05 in phase are features that resemble icicles. The icicles arise because there is a second periodic system whose main feature is a broad flux dip. Using a toy model, we show that the observed light curve morphology results only if the ratio of the two periods and the flux-dip width are carefully arranged
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