Modified Friedman scenario from the Wheeler-DeWitt equation

We consider the possible modification of the Friedman equation due to operator ordering parameter entering the Wheeler-DeWitt equation.Comment: 2 pages, 1 figur

A Dichotomy in Satellite Quenching Around L* Galaxies

We examine the star formation properties of bright (~0.1 L*) satellites around isolated ~L* hosts in the local Universe using spectroscopically confirmed systems in the Sloan Digital Sky Survey DR7. Our selection method is carefully designed with the aid of N-body simulations to avoid groups and clusters. We find that satellites are significantly more likely to be quenched than a stellar mass-matched sample of isolated galaxies. Remarkably, this quenching occurs only for satellites of hosts that are themselves quenched: while star formation is unaffected in the satellites of star-forming hosts, satellites around quiescent hosts are more than twice as likely to be quenched than stellar-mass matched field samples. One implication of this is that whatever shuts down star formation in isolated, passive L* galaxies also plays at least an indirect role in quenching star formation in their bright satellites. The previously-reported tendency for "galactic conformity" in color/morphology may be a by-product of this host-specific quenching dichotomy. The S\'ersic indices of quenched satellites are statistically identical to those of field galaxies with the same specific star formation rates, suggesting that environmental and secular quenching give rise to the same morphological structure. By studying the distribution of pairwise velocities between the hosts and satellites, we find dynamical evidence that passive host galaxies reside in dark matter halos that are ~45% more massive than those of star-forming host galaxies of the same stellar mass. We emphasize that even around passive hosts, the mere fact that galaxies become satellites does not typically result in star formation quenching: we find that only ~30% of ~0.1 L* galaxies that fall in from the field are quenched around passive hosts, compared with ~0% around star forming hosts.Comment: 14 pages, 9 figure

On the Rates of Type Ia Supernovae in Dwarf and Giant Hosts with ROTSE-IIIb

We present a sample of 23 spectroscopically confirmed Type Ia supernovae that were discovered in the background of galaxy clusters targeted by ROTSE-IIIb and use up to 18 of these to determine the local (z = 0.05) volumetric rate. Since our survey is flux limited and thus biased against fainter objects, the pseudo-absolute magnitude distribution (pAMD) of SNeIa in a given volume is an important concern, especially the relative frequency of high to low-luminosity SNeIa. We find that the pAMD derived from the volume limited Lick Observatory Supernova Search (LOSS) sample is incompatible with the distribution of SNeIa in a volume limited (z<0.12) sub sample of the SDSS-II. The LOSS sample requires far more low-luminosity SNeIa than the SDSS-II can accommodate. Even though LOSS and SDSS-II have sampled different SNeIa populations, their volumetric rates are surprisingly similar. Using the same model pAMD adopted in the SDSS-II SNeIa rate calculation and excluding two high-luminosity SNeIa from our sample, we derive a rate that is marginally higher than previous low-redshift determinations. With our full sample and the LOSS pAMD our rate is more than double the canonical value. We also find that 5 of our 18 SNeIa are hosted by very low-luminosity (M_B > -16) galaxies, whereas only 1 out 79 nearby SDSS-II SNeIa have such faint hosts. It is possible that previous works have under-counted either low luminosity SNeIa, SNeIa in low luminosity hosts, or peculiar SNeIa (sometimes explicitly), and the total SNeIa rate may be higher than the canonical value.Comment: 18 pages; accepted for publication in The Astronomical Journa

The economic performance of cities: a Markov-switching approach

This paper examines the determinants of employment growth in metro areas. To obtain growth rates, we use a Markov-switching model that separates a city’s growth path into two distinct phases (high and low), each with its own growth rate. The simple average growth rate over some period is, therefore, the weighted average of the high-phase and low-phase growth rates, with the weight being the frequency of the two phases. We estimate the effects of a variety of factors separately for the high-phase and low-phase growth rates, along with the frequency of the low phase. We find that growth in the high phase is related to human capital, industry mix, and average firm size. In contrast, we find that growth in the low phase is mostly related to industry mix, specifically, the relative importance of manufacturing. Finally, the frequency of the low phase appears to be related to the level of non-education human capital, but to none of the other variables. Overall, our results strongly reject the notion that city-level characteristics influence employment growth equally across the phases of the business cycle.Business cycles ; Cities and towns

Finite-time quantum-to-classical transition for a Schroedinger-cat state

The transition from quantum to classical, in the case of a quantum harmonic oscillator, is typically identified with the transition from a quantum superposition of macroscopically distinguishable states, such as the Schr\"odinger cat state, into the corresponding statistical mixture. This transition is commonly characterized by the asymptotic loss of the interference term in the Wigner representation of the cat state. In this paper we show that the quantum to classical transition has different dynamical features depending on the measure for nonclassicality used. Measures based on an operatorial definition have well defined physical meaning and allow a deeper understanding of the quantum to classical transition. Our analysis shows that, for most nonclassicality measures, the Schr\"odinger cat dies after a finite time. Moreover, our results challenge the prevailing idea that more macroscopic states are more susceptible to decoherence in the sense that the transition from quantum to classical occurs faster. Since nonclassicality is prerequisite for entanglement generation our results also bridge the gap between decoherence, which appears to be only asymptotic, and entanglement, which may show a sudden death. In fact, whereas the loss of coherences still remains asymptotic, we have shown that the transition from quantum to classical can indeed occur at a finite time.Comment: 9+epsilon pages, 4 figures, published version. Originally submitted as "Sudden death of the Schroedinger cat", a bit too cool for APS policy :-

Effectiveness of Gluten-Free and Casein-Free Diets for Individuals with Autism Spectrum Disorders: An Evidence-Based Research Synthesis

In order to better assist practitioners and better serve persons with autism spectrum disorders (ASD) and their families, it is vital for professionals to systematically evaluate the existing body of literature and synthesize its scientific evidence, so that the efficacy of research can be translated to evidence-based practices (EBPs) (Wheeler, 2007; Zhang & Wheeler, 2011). This research synthesis evaluated adherence to EBP standards and analyzed the effectiveness of gluten-free and casein-free (GFCF) diets for individuals with ASD. Four hundred and seventy articles were screened among peer-reviewed journals in English language published through 2010 using the Academic Search Complete search database. Twenty-three studies were selected, and the researchers used a systematic analysis model developed by Mayton, Wheeler, Menendez, and Zhang (2010) to investigate the degree of adherence to specific evidence-based practice standards. In addition, the study utilized quality indicators proposed by (a) Horner et al. (2005) for single-subject design studies and (b) Gersten et al. (2005) for group experimental design, to evaluate the efficacy of GFCF diet interventions. Results of this synthesis indicated that the efficacy of GFCF diet interventions for individuals with ASD is inconclusive, and the field needs better controlled studies to provide the scientific evidence base for the intervention

Effectiveness of gluten-free and casein-free diets for individuals with autism spectrum disorders: An evidence-based research synthesis.

In order to better assist practitioners and better serve persons with autism spectrum disorders (ASD) and their families, it is vital for professionals to systematically evaluate the existing body of literature and synthesize its scientific evidence, so that the efficacy of research can be translated to evidence-based practices (EBPs) (Wheeler, 2007; Zhang & Wheeler, 2011). This research synthesis evaluated adherence to EBP standards and analyzed the effectiveness of gluten-free and casein-free (GFCF) diets for individuals with ASD. Four hundred and seventy articles were screened among peer-reviewed journals in English language published through 2010 using the Academic Search Complete search database. Twenty-three studies were selected, and the researchers used a systematic analysis model developed by Mayton, Wheeler, Menendez, and Zhang (2010) to investigate the degree of adherence to specific evidence-based practice standards. In addition, the study utilized quality indicators proposed by (a)Horner et al (2005) for single-subject design studies and (b) Gersten et al. (2005) for group experimental design, to evaluate the efficacy of GFCF diet interventions. Results of this synthesis indicated that the efficacy of GFCF diet interventions for individuals with ASD is inconclusive, and the field needs better controlled studies to provide the scientific evidence base for the intervention