Some Calculable Contributions to Entanglement Entropy

Entanglement entropy appears as a central property of quantum systems in broad areas of physics. However, its precise value is often sensitive to unknown microphysics, rendering it incalculable. By considering parametric dependence on correlation length, we extract finite, calculable contributions to the entanglement entropy for a scalar field between the interior and exterior of a spatial domain of arbitrary shape. The leading term is proportional to the area of the dividing boundary; we also extract finite subleading contributions for a field defined in the bulk interior of a waveguide in 3+1 dimensions, including terms proportional to the waveguide's cross-sectional geometry; its area, perimeter length, and integrated curvature. We also consider related quantities at criticality and suggest a class of systems for which these contributions might be measurable.Comment: 4+ pages, 1 figure. v2: Some clarifications and more references; updated to resemble version published in PR

Axion Cosmology and the Energy Scale of Inflation

We survey observational constraints on the parameter space of inflation and axions and map out two allowed windows: the classic window and the inflationary anthropic window. The cosmology of the latter is particularly interesting; inflationary axion cosmology predicts the existence of isocurvature fluctuations in the CMB, with an amplitude that grows with both the energy scale of inflation and the fraction of dark matter in axions. Statistical arguments favor a substantial value for the latter, and so current bounds on isocurvature fluctuations imply tight constraints on inflation. For example, an axion Peccei-Quinn scale of 10^16 GeV excludes any inflation model with energy scale > 3.8*10^14 GeV (r > 2*10^(-9)) at 95% confidence, and so implies negligible gravitational waves from inflation, but suggests appreciable isocurvature fluctuations.Comment: 10 PRD pages, 4 figs, V3: updated to match published versio

Attractive Casimir Forces in a Closed Geometry

We study the Casimir force acting on a conducting piston with arbitrary cross section. We find the exact solution for a rectangular cross section and the first three terms in the asymptotic expansion for small height to width ratio when the cross section is arbitrary. Though weakened by the presence of the walls, the Casimir force turns out to be always attractive. Claims of repulsive Casimir forces for related configurations, like the cube, are invalidated by cutoff dependence.Comment: An updated version to coincide with the one published December 2005 in PRL. 4 pages, 2 figure

Warm tachyonic inflation in warped background

We analyze warm tachyonic inflation, proposed in the literature, but from the viewpoint of four dimensional effective action for tachyon field on a non-BPS D3-brane. We find that consistency with observational data on density perturbation and validity of effective action requires warped compactification. The number of background branes which source the flux is found to be of the order of 10 in contrast to the order of $10^{14}$ in the standard cold inflationary scenario.Comment: 9 pages, RevTe

Effects of paddock management on vegetation, nutrient accumulation, and internal parasites in laying hens

Management of paddocks for free-range layers requires an effort from farmers to minimize the adverse effects of these systems on animal health (e.g., parasites) and environment (e.g., nutrient accumulation and leaching). In this study, we report results from 2 on-farm experiments conducted to investigate (1) the effects of rotational versus continuous use of the paddocks and (2) the effects of wood chips in the area close to the pop holes (openings to the paddock) with regard to turf quality, nutrient load in the soil, and parasite infections. Rotational use of the hen paddocks led to a lower proportion of bare soil close to the house, but not in more distant regions. Covering the area in front of the house with wood chips did not reduce bare areas. Nitrogen and phosphorous contents in soil were similar in permanently and rotationally used paddocks; they were usually higher close to the house than in distant regions. Neither nutrient accumulated over the observation period. There was no significant effect of the 2 management regimens on worm burdens (Ascaridia galli, Heterakis gallinarum, Capillaria spp.) at the end of the laying period. Fecal egg counts were significantly reduced on rotationally used paddocks and (in 3 of 4 cases) on paddocks with wood chips in the area close to the pop holes compared with unmanaged paddocks. Based on the positive effects on turf quality, manageability, and helminth egg excretion, we recommend rotational paddock management and a permanently used, small all-weather run covered with wood chips or gravel for free-range layer flock

Absolute and convective instabilities of parallel propagating circularly polarized Alfven waves: Beat instability

Ruderman and Simpson [Phys. Plasmas 11, 4178 (2004)] studied the absolute and convective decay instabilities of parallel propagating circularly polarized Alfven waves in plasmas where the sound speed c(S) is smaller than the Alfven speed upsilon(A). We extend their analysis for the beat instability which occurs in plasmas with c(S)>upsilon(A). We assume that the dimensionless amplitude of the circularly polarized Alfven wave (pump wave), a, is small. Applying Briggs' method we study the problem analytically using expansions in power series with respect to a. It is shown that the pump wave is absolutely unstable in a reference frame moving with the velocity U with respect to the rest plasma if U-lU-r, the instability is convective. The signaling problem is studied in a reference frame where the pump wave is convectively unstable. It is shown that the spatially amplifying waves exist only when the signaling frequency is in two narrow symmetric frequency bands with the widths of the order of a(3). These results enable us to extend for the case when c(S)>upsilon(A) the conclusions, previously made for the case when c(S)<upsilon(A), that circularly polarized Alfven waves propagating in the solar wind are convectively unstable in a reference frame of any spacecraft moving with the velocity not exceeding a few tens of km/s in the solar reference frame. The characteristic scale of spatial amplification for these waves exceeds 1 a.u

Magnetic field generation in Higgs inflation model

We study the generation of magnetic field in Higgs-inflation models where the Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple the Higgs field to the Electromagnetic fields via a non- renormalizable dimension six operator suppressed by the Planck scale in the Jordan frame. We show that during Higgs inflation magnetic fields with present value $10^{-6}$ Gauss and comoving coherence length of $100 kpc$ can be generated in the Einstein frame. The problem of large back-reaction which is generic in the usual inflation models of magneto-genesis is avoided as the back-reaction is suppressed by the large Higgs-curvature coupling.Comment: 10 pages, RevTeX

Probing Dark Matter Substructure with Pulsar Timing

We demonstrate that pulsar timing measurements may potentially be able to detect the presence of dark matter substructure within our own galaxy. As dark matter substructure transits near the line-of-sight between a pulsar and an observer, the change in the gravitational field will result in a delay of the light-travel-time of photons. We calculate the effect of this delay due to transiting dark matter substructure and find that the effect on pulsar timing ought to be observable over decadal timescales for a wide range of substructure masses and density profiles. We find that transiting dark matter substructure with masses above 0.01 solar masses ought to be detectable at present by these means. With improved measurements, this method may be able to distinguish between baryonic, thermal non-baryonic, and non-thermal non-baryonic types of dark matter. Additionally, information about structure formation on small scales and the density profiles of galactic dark matter substructure can be extracted via this method.Comment: 8 pages, 4 figures, replaced to match published versio

Ultrahigh Vacuum Packaging and Surface Cleaning for Quantum Devices

We describe design, implementation and performance of an ultra-high vacuum (UHV) package for superconducting qubit chips or other surface sensitive quantum devices. The UHV loading procedure allows for annealing, ultra-violet light irradiation, ion milling and surface passivation of quantum devices before sealing them into a measurement package. The package retains vacuum during the transfer to cryogenic temperatures by active pumping with a titanium getter layer. We characterize the treatment capabilities of the system and present measurements of flux tunable qubits with an average T$_1=84~\mu$s and T$^{echo}_2=134~\mu$s after vacuum-loading these samples into a bottom loading dilution refrigerator in the UHV-package.Comment: 5 pages, 6 figure