Shifting the Universe: Early Dark Energy and Standard Rulers

The presence of dark energy at high redshift influences both the cosmic sound horizon and the distance to last scattering of the cosmic microwave background. We demonstrate that through the degeneracy in their ratio, early dark energy can lie hidden in the CMB temperature and polarization spectra, leading to an unrecognized shift in the sound horizon. If the sound horizon is then used as a standard ruler, as in baryon acoustic oscillations, then the derived cosmological parameters can be nontrivially biased. Fitting for the absolute ruler scale (just as supernovae must be fit for the absolute candle magnitude) removes the bias but decreases the leverage of the BAO technique by a factor 2.Comment: 6 pages, 3 figure

Utilizing H.M.S. Richards\u27 Sermons and Writings in the Development of Sermons that Focus on the Unique Aspects of Seventh-day Adventist Preaching as Implemented at the Kress Memorial Church in Winter Park, Florida

Problem H. M. S. Richards maintains that Seventh-day Adventist preaching should be distinct from the preaching of others. What guidelines does Richards provide for determining what should be included in Adventist preaching, and how can those guidelines be integrated into the preaching at the Kress Memorial Seventh-day Adventist Church? Method The books, articles, and sermons of H. M. S. Richards were researched for guidance on what Seventh-day Adventist preaching should include. On the basis of the principles developed from Richards, twelve sermons preached prior to the research were evaluated. Twelve new sermons following Richards’ principles were then written and preached at the Kress Memorial Church. The sermons were evaluated by two retired pastors and one evangelist from the Florida Conference of Seventh-day Adventists. Results The research from the study of Richards’ books, articles, and sermons shows the importance of preaching the distinct doctrines of Seventh-day Adventism while maintaining a clear connection to Christ. The evaluations of the twelve sermons preached before the research revealed a lack of focus on doctrines that are important to the Seventh-day Adventist Church. The twelve sermons prepared as a part of this project showed more intentionality in emphasizing Seventh-day Adventist doctrines and their connection to Christ. The study shows that one can be faithful to biblical teaching and its emphasis on Christ and at the same time communicate Seventh-day Adventist doctrines. Conclusion The research of H. M. S. Richards’ sermons and writings leads to the conclusion that the Seventh-day Adventist message and mission demands intentionality in preaching. It is not only legitimate, but necessary to preach sermons that reinforce both the understanding of Scripture and the purpose for the existence of Adventism. Such preaching must maintain Christ as the source of salvation. For the spiritual health of the church such sermons should be scheduled into the preaching calendar

Racial profiling in Las Vegas: A reexamination of police stop data in Las Vegas

Racial profiling remains the subject of controversy when discussing police and minority relationships. Recently, scholars have studied this controversial issue in an attempt to determine the characteristics and extent of the problem. Although researchers have suggested possible reasons for racial disparities in traffic stop data, more information is needed to develop a more in-depth understanding of these disparities. The study presented here analyzes traffic stop data from Las Vegas during the 2002 calendar year. The study analyzes key driver characteristics and whether these characteristics influence the officer\u27s search or arrest of the driver. The study uses univariate, bivariate, and multivariate analyses. The study finds limited support for the differential enforcement theory, although variables not available to the analyses may mitigate this result. Policy implications of the research findings are discussed

Theory Challenges of the Accelerating Universe

The accelerating expansion of the universe presents an exciting, fundamental challenge to the standard models of particle physics and cosmology. I highlight some of the outstanding challenges in both developing theoretical models and interpreting without bias the observational results from precision cosmology experiments in the next decade that will return data to help reveal the nature of the new physics. Examples given focus on distinguishing a new component of energy from a new law of gravity, and the effect of early dark energy on baryon acoustic oscillations.Comment: 10 pages, 4 figures; minor changes to match J. Phys. A versio

Dark Energy in the Dark Ages

Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or ``reasonable'' canonical scalar fields. Such dark energy can be constrained tightly through investigation of the growth of structure, with limits of \la2% of total energy density at z\gg1 for many models. Intermediate dark energy can have effects distinct from its energy density; the dark ages acceleration can be constrained to last less than 5% of a Hubble e-fold time, exacerbating the coincidence problem. Both the total linear growth, or equivalently \sigma_8, and the shape and evolution of the nonlinear mass power spectrum for z<2 (using the Linder-White nonlinear mapping prescription) provide important windows. Probes of growth, such as weak gravitational lensing, can interact with supernovae and CMB distance measurements to scan dark energy behavior over the entire range z=0-1100.Comment: 6 pages, 5 figures; figure added, minor edits to match Astropart.Phys. versio

Halo Mass Functions in Early Dark Energy Cosmologies

We examine the linear density contrast at collapse time, $\delta_c$ for large-scale structure in dynamical dark energy cosmologies, including models with early dark energy. Contrary to previous results, we find that as long as dark energy is homogeneous on small scales, $\delta_c$ is insensitive to dark energy properties for parameter values fitting current data, including the case of early dark energy. This is significant since using the correct $\delta_c$ is crucial for accurate Press-Schechter prediction of the halo mass function. Previous results have found an apparent failing of the extended Press-Schechter approach (Sheth-Tormen) for early dark energy. Our calculations demonstrate that with the correct $\delta_c$ the accuracy of this approach is restored. We discuss the significance of this result for the halo mass function and examine what dark energy physics would be needed to cause significant change in $\delta_c$, and the observational signatures this would leave.Comment: 5 pages, 2 figures. Accepted for MNRAS Letter

Discrete Torsion and Shift Orbifolds

In this paper we make two observations related to discrete torsion. First, we observe that an old obscure degree of freedom (momentum/translation shifts) in (symmetric) string orbifolds is related to discrete torsion. We point out how our previous derivation of discrete torsion from orbifold group actions on B fields includes these momentum lattice shift phases, and discuss how they are realized in terms of orbifold group actions on D-branes. Second, we describe the M theory dual of IIA discrete torsion, a duality relation to our knowledge not previously understood. We show that IIA discrete torsion is encoded in analogues of the shift orbifolds above for the M theory C field.Comment: 28 pages, LaTeX, 3 figures; v2: references adde

Can Early Dark Energy be Detected in Non-Linear Structure?

We present the first study of early dark energy cosmologies using N-body simulations to investigate the formation of non-linear structure. In contrast to expectations from semi-analytic approaches, we find that early dark energy does not imprint a unique signature on the statistics of non-linear structures. Investigating the non-linear power spectra and halo mass functions, we show that universal mass functions hold for early dark energy, making its presence difficult to distinguish from $\Lambda$CDM. Since early dark energy biases the baryon acoustic oscillation scale, the lack of discriminating power is problematic.Comment: 11 pages, 19 figures. Minor changes to match version accepted to MNRA

Overestimation of thermal emittance in solenoid scans due to coupled transverse motion

The solenoid scan is a widely used method for the in-situ measurement of the thermal emittance in a photocathode gun. The popularity of this method is due to its simplicity and convenience since all rf photocathode guns are equipped with an emittance compensation solenoid. This paper shows that the solenoid scan measurement overestimates the thermal emittance in the ordinary measurement configuration due to a weak quadrupole field (present in either the rf gun or gun solenoid) followed by a rotation in the solenoid. This coupled transverse dynamics aberration introduces a correlation between the beam's horizontal and vertical motion leading to an increase in the measured 2D transverse emittance, thus the overestimation of the thermal emittance. This effect was systematically studied using both analytic expressions and numerical simulations. These studies were experimentally verified using an L-band 1.6-cell rf photocathode gun with a cesium telluride cathode, which shows a thermal emittance overestimation of 35% with a rms laser spot size of 2.7 mm. The paper concludes by showing that the accuracy of the solenoid scan can be improved by using a quadrupole magnet corrector, consisting of a pair of normal and skew quadrupole magnets.Comment: 12 pages, 13 figure

On the Performance of Digital Back Propagation in Spatial Multiplexing Systems

Nonlinear performance in spatial multiplexing systems is strongly determined by the interplay between differential mode delay, linear mode coupling, and Kerr nonlinearity. In this article we review and extend the analysis of different solution methods for the linear coupling operator in the coupled nonlinear Schrödinger equation for spatial multiplexed propagation. Numerical solution methods are compared for different operational regimes as determined by differential mode delay and linear mode coupling. Finally, we review and extend the study of digital methods to mitigate the Kerr nonlinearity for arbitrary levels of random linear mode coupling. For the first time, it is shown that in spatial multiplexing systems transmission performance can be improved by reducing the number of back propagated channels for non-negligible levels of differential mode delay