Absence of a VVDZ Discontinuity in AdS_AdS

We clarify the role of gauge invariance for the theory of an AdS4 brane embedded in AdS5. The presence of a nonvanishing mass parameter even for the lightest KK mode of the graviton indicates that all of the spin-2 modes propagate five polarization states. Despite this fact, it was shown earlier that the classical theory has a smooth limit as the mass parameter is taken to zero. We argue that locality in the fifth dimension ensures that this property survives at the quantum level.Comment: 4 pages, Revtex; discussion of why VVDZ is not a problem even at the quantum level is change

SNOWPACK CONTROLS ON HYDROLOGIC RESPONSE TO EXTREME RAIN-ON-SNOW EVENTS IN THE NORTHERN SIERRA NEVADA

Continuous, near-real time predictions of winter flooding are critical to balancing the protection of life and property with providing water resources for consumptive use in California’s northern Sierra Nevada. Rain-on-snow (ROS) events are a major cause of floods in the region and are expected to increase as a result of climate change. During ROS, the amount of terrestrial water input (TWI) draining from the snowpack is the major driver of floods and depends on the snowpack's capacity to refreeze liquid water, its transmissivity, and the magnitude of snow melt during the event. The outcome is an interplay between (1) the amount and intensity of precipitation, (2) the antecedent conditions of the snowpack and (3) the potential for incoming energy to melt snow and drain additional water. An incomplete understanding and insufficient measurement of these interacting processes limits the skill of flood prediction in mountain regions. In this study, antecedent snowpack conditions, specifically cold content, density, liquid water content and SWE, are examined to understand how these factors modulate TWI during ROS. Data from three SNOTEL stations, common in the Western U.S., across a 500 m elevation gradient on the eastern side of California’s Sierra Nevada mountains are used as input to a physically-based model that simulates liquid water drainage explicitly (SNOWPACK). Hourly forcing parameters were developed to calibrate and validate the SNOWPACK model to the SNOTEL stations spanning water years 1981-2019 and 149 ROS events. During the 149 historical events, the snowpack mitigated TWI for 80% of events, 13% had no mitigation, and 7% had conditions for active melt. Mean TWI increased 32% from the lowest elevation (58 mm of water) to the highest elevation (85 mm of water). As expected, the amount of TWI depends on total rainfall, however, that events with TWI/rain ratios>1.0 produce the largest event streamflows. When antecedent conditions were varied in reasonable ways, total TWI response varies 46% on average across eight extreme events. A key result is that snowpack cold content explains the majority of TWI variability. Riper snowpacks generated the highest TWI values for most events, with a 1 MJ decrease in cold content corresponding to 0.74 more TWI. Our results highlight the importance of cold content in TWI response across realistic antecedent conditions. Cold content is rarely measured and effectively not included in operational flood forecast models. As ROS becomes increasingly frequent in a warming climate, enhanced observations of cold content and modeling could have important implications for improved flood forecasting

Moving to Opportunity and Tranquility: Neighborhood Effects on Adult Economic Self-Sufficiency and Health From a Randomized Housing Voucher Experiment

neighborhood effects, housing vouchers

Dark-Disk Universe

We point out that current constraints on dark matter imply only that the majority of dark matter is cold and collisionless. A subdominant fraction of dark matter could have much stronger interactions. In particular, it could interact in a manner that dissipates energy, thereby cooling into a rotationally supported disk, much as baryons do. We call this proposed new dark matter component double-disk dark matter (DDDM). We argue that DDDM could constitute a fraction of all matter roughly as large as the fraction in baryons, and that it could be detected through its gravitational effects on the motion of stars in galaxies, for example. Furthermore, if DDDM can annihilate to gamma rays, it would give rise to an indirect detection signal distributed across the sky that differs dramatically from that predicted for ordinary dark matter. DDDM and more general partially interacting dark matter scenarios provide a large unexplored space of testable new physics ideas.Physic

Double-Disk Dark Matter

Based on observational tests of large scale structure and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component’s interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy (depending on precise alignment) can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.Physic

Antimicrobial resistance in commensal faecal Escherichia coli of hospitalised horses

The objective of this study was to examine the impact of hospitalisation and antimicrobial drug administration on the prevalence of resistance in commensal faecal E. coli of horses. Faecal samples were collected from ten hospitalised horses treated with antimicrobials, ten hospitalised horses not treated with antimicrobials and nine non-hospitalised horses over a consecutive five day period and susceptibility testing was performed on isolated E. coli. Results revealed that hospitalisation alone was associated with increased prevalence of antimicrobial resistance and multidrug resistance in commensal E. coli of horses. Due to the risk of transfer of resistance between commensal and pathogenic bacteria, veterinarians need to be aware of possible resistance in commensal bacteria when treating hospitalised horses