Confinement by Monopoles in the Positive Plaquette Model of SU(2) Lattice Gauge Theory

Confinement via 't Hooft-Mandelstam monopoles is studied for the positive plaquette model in SU(2) lattice gauge theory. Positive plaquette model configurations are projected into the maximum abelian gauge and the magnetic current extracted. The resulting magnetic current is used to compute monopole contributions to Wilson loops and extract a monopole contribution to the string tension. As was previously found for the Wilson action, the monopole contribution to the string tension agrees with the string tension calculated directly from the SU(2) links. The fact that the positive plaquette model suppresses Z2 monopoles and vortices is discussed.Comment: 8 pages, one Postscript figure, Latex, uses psfig files: posplaq.tex,posplaq.aux,pp_1_3.ps packaged with uufile

Numerical Investigation of Second Mode Attenuation over Carbon/Carbon Surfaces on a Sharp Slender Cone

We have carried out axisymmetric numerical simulations of a spatially developing hypersonic boundary layer over a sharp 7$^{\circ{}}$-half-angle cone at $M_\infty=7.5$ inspired by the experimental investigations by Wagner (2015). Simulations are first performed with impermeable (or solid) walls with a one-time broadband pulse excitation applied upstream to determine the most convectively-amplified frequencies resulting in the range 260kHz -- 400kHz, consistent with experimental observations of second-mode instability waves. Subsequently, we introduce harmonic disturbances via continuous periodic suction and blowing at 270kHz and 350kHz. For each of these forcing frequencies complex impedance boundary conditions (IBC), modeling the acoustic response of two different carbon/carbon (C/C) ultrasonically absorptive porous surfaces, are applied at the wall. The IBCs are derived as an output of a pore-scale aeroacoustic analysis -- the inverse Helmholtz Solver (iHS) -- which is able to return the broadband real and imaginary components of the surface-averaged impedance. The introduction of the IBCs in all cases leads to a significant attenuation of the harmonically-forced second-mode wave. In particular, we observe a higher attenuation rate of the introduced waves with frequency of 350kHz in comparison with 270kHz, and, along with the iHS impedance results, we establish that the C/C surfaces absorb acoustic energy more effectively at higher frequencies.Comment: AIAA-SciTech 201

Drift and Diffusion of Spins Generated by the Spin Hall Effect

Electrically generated spin accumulation due to the spin Hall effect is imaged in n-GaAs channels using Kerr rotation microscopy, focusing on its spatial distribution and time-averaged behavior in a magnetic field. Spatially-resolved imaging reveals that spin accumulation observed in transverse arms develops due to longitudinal drift of spin polarization produced at the sample boundaries. One- and two-dimensional drift-diffusion modeling is used to explain these features, providing a more complete understanding of observations of spin accumulation and the spin Hall effect.Comment: 9 pages, 3 figure

Short distance potential and the thick center vortex model

The short distance potentials between heavy SU(3) and SU(4) sources are calculated by increasing the role of vortex fluxes piercing Wilson loops with contributions close to the trivial center element and by fluctuating the vortex core size in the model of thick center vortices. By this method, a Coulombic potential consistent with Casimir scaling is obtained. In addition, all other features of the potential including a linear intermediate potential in agreement with Casimir scaling and a large distance potential proportional to the $N$-ality of the representation are restored. Therefore, the model of thick center vortices may be used as a phenomenological model, which is able to describe the potential for all regimes.Comment: 9 pages and 6 figure

The Development of Art Learning Model at School (a Review of Music Education Learning in Indonesia)

At the present time, art education is often ignored. Focus on teaching and learning at school seems to accentuate other subjects, such as: science, economics, and technology. This trend is becoming more concerning for the arts is a field of study, which draws attention to the development of perceptual sensitivity, creativity, as well as social responsibility. However, if art education, in this case is music education, is taught theoretically based on other cultural materials, then the consequences will be worse for students. This study is aimed to draw outlines of music education which hopefully can answer the three aspects of music which are previously described. The outlines are arranged based on recent discoveries in audio perceptions

Defense Industrial Base Mergers and Acquisitions in the Post-Cold War Era

The United States Department of Defense (DoD) relies on prime contractors for weapon system development, acquisition, and sustainability, but the increased consolidation of the Defense Industrial Base (DIB) through mergers and acquisitions (M&A) has raised concerns over reduced competition. This research consists of two studies. The first reviews existing literature to identify factors behind the DIB\u27s increased M&A activity since the 1990s, such as DoD budget cuts and market structure. The second study examines the relationship between a prime contractor\u27s financial health and M&A spending, finding a significant relationship between efficiency and M&A spending. Policymakers can use this information to make informed policies and regulations, ensuring a competitive defense industry, global military superiority, and strengthened national defense

Factors Affecting Waterfowl Brood Use of Stock Ponds in South Dakota

A July waterfowl brood survey was conducted from 1973 to 1976 on stock ponds located within four physiographic strata in South Dakota. Information was collected on weather, stock pond characteristics, land use and the condition of other wetlands located within the quarter section (64.8 ha) study plots. Multiple regression and multiple discriminant analyses were sued to determine the importance of these variables in influencing brood use of stock ponds. Vegetation type, distribution of emergent vegetation and pond size were important in determining if broods of any particular species utilized a pond or not. Shoreline distance was particularly important in explaining variation in brood densities. Highest brood densities occurred on stock ponds of 0.40 to 1.00 ha surface-water area. Blue-winged teal (Anas discors) broods were positively associated with alfalfa and negatively associated with total stream area on the study plot. Mallard (Anas platyrhynchos) broods were negatively associated with pasture and hayland. Pintail (Anas acuta) and gadwall (Anas strepera) broods exhibited a positive association with stock ponds that had a dispersed pattern of vegetation and were located in areas of high surrounding wetland densities. Older broods of all four species combined (subclass IIc and class III) were positively associated with stock ponds having a stable water level and emergent vegetation

Upper Bound on the Dark Matter Total Annihilation Cross Section

We consider dark matter annihilation into Standard Model particles and show that the least detectable final states, namely neutrinos, define an upper bound on the total cross section. Calculating the cosmic diffuse neutrino signal, and comparing it to the measured terrestrial atmospheric neutrino background, we derive a strong and general bound. This can be evaded if the annihilation products are dominantly new and truly invisible particles. Our bound is much stronger than the unitarity bound at the most interesting masses, shows that dark matter halos cannot be significantly modified by annihilations, and can be improved by a factor of 10--100 with existing neutrino experiments.Comment: 4 pages, 3 figures; version accepted for publication in PR