1,162 research outputs found
Higgs-inspired corrections to the RG flow in the finite-temperature 3D Georgi-Glashow model and its SU(N)-generalization
The Berezinsky-Kosterlitz-Thouless (BKT) RG flow in the ensemble of monopoles
existing in the finite-temperature (2+1)D Georgi-Glashow model is explored in
the regime when the Higgs field is not infinitely heavy, but its mass is rather
of the same order of magnitude as the mass of the W-boson. The corrections to
the standard RG flow are derived to the leading order in the inverse mass of
the Higgs boson. According to the obtained RG equations, the scaling of the
free-energy density in the critical region and the value of the critical
temperature of the phase transition are found to be unaffected by the
finiteness of the Higgs-boson mass. The evolution of the Higgs mass itself is
also investigated and shown to be rather weak, that enables one to treat this
parameter as a constant. The same analysis is further performed in the
SU(N)-case at N>2, where the RG invariance is demonstrated to hold only
approximately, in a certain sense. Modulo this approximation, the critical
behaviour of the SU(N)-model turns out to be identical to that of the
SU(2)-one.Comment: 12 pages, LaTeX2e, no figure
A Catalog of Absorption Lines in Eight HST/STIS E230M 1.0 < z < 1.7 Quasar Spectra
We have produced a catalog of line identifications and equivalent width
measurements for all absorption features in eight ultraviolet echelle quasar
spectra. These spectra were selected as having the highest signal-to-noise
among the HST/STIS spectra obtained with the E230M grating. We identify 56
metal-line systems toward the eight quasars, and present plots of detected
transitions, aligned in velocity-space. We found that about 1/4 - 1/3 of the
features in the Lya forest region, redward of the incidence of the Lyb forest,
are metal lines. High ionization transitions are common. We see both O VI and C
IV in 88 - 90% of the metal-line systems for which the spectra cover the
expected wavelength. Si III is seen in 58%, while low ionization absorption in
C II, Si II, and/or Al II is detected in 50% of the systems for which they are
covered. This catalog will facilitate future studies of the Lya forest and of
metal-line systems of various types.Comment: 13 pages, 2 figures, submitted to Monthly Notices of the Royal
Astronomical Society, a complete version with the appendix and all figures is
available at http://www.astro.psu.edu/users/misawa/pub/Paper/qalcat.pdf.g
Spin and orbital moments of ultra-thin Fe films on various semiconductor surfaces
The magnetic moments of ultrathin Fe films on three different III-V semiconductor substrates, namely GaAs, InAs and In0.2Ga0.8As have been measured with X-ray magnetic circular dichroism at room temperature to assess their relative merits as combinations suitable for next-generation spintronic devices. The results revealed rather similar spin moments and orbital moments for the three systems, suggesting the relationship between film and semiconductor lattice parameters to be less critical to magnetic moments than magnetic anisotropy
The Deuterium Abundance in the z=0.7 absorber towards QSO PG1718+4807
We report a further analysis of the ratio of deuterium to hydrogen (D/H)
using HST spectra of the z=0.701 Lyman limit system towards the QSO PG1718+481.
Initial analyses of this absorber found it gave a high D/H value, 1.8 - 3.1
\times 10^{-4} (Webb et al. 1998), inconsistent with several higher redshift
measurements. It is thus important to critically examine this measurement. By
analysing the velocity widths of the DI, HI and metal lines present in this
system, Kirkman et al. (2001) report that the additional absorption in the blue
wing of the lya line can not be DI, with a confidence level of 98%. Here we
present a more detailed analysis, taking into account possible wavelength
shifts between the three sets of HST spectra used in the analysis. We find that
the constraints on this system are not as strong as those claimed by Kirkman et
al. The discrepancy between the parameters of the blue wing absorption and the
parameters expected for DI is marginally worse than 1 sigma.
Tytler et al.(1999) commented on the first analysis of Webb et
al.(1997,1998), reporting the presence of a contaminating lower redshift Lyman
limit system, with log[N(HI)] = 16.7 at z=0.602, which biases the N(HI)
estimate for the main system. Here we show that this absorber actually has
log[N(HI)] < 14.6 and does not impact on the estimate of N(HI) in the system of
interest at z = 0.701.
The purpose of the present paper is to highlight important aspects of the
analysis which were not explored in previous studies, and hence help refine the
methods used in future analyses of D/H in quasar spectra.Comment: 11 pages, 9 figures. Accepted by MNRA
The 4U 0115+63: Another energetic gamma ray binary pulsar
Following the discovery of Her X-1 as a source of pulsed 1000 Gev X-rays, a search for emission from an X-ray binary containing a pulsar with similar values of period, period derivative and luminosity was successful. The sporadic X-ray binary 4U 0115-63 has been observed, with probability 2.5 x 10 to the minus 6 power ergs/s to emit 1000 GeV gamma-rays with a time averaged energy flux of 6 to 10 to the 35th power
Greater Omentectomy Improves Insulin Sensitivity in Nonobese Dogs
Visceral adiposity is strongly associated with insulin resistance; however, little evidence directly demonstrates that visceral fat per se impairs insulin action. Here, we examine the effects of the surgical removal of the greater omentum and its occupying visceral fat, an omentectomy (OM), on insulin sensitivity (SI) and β-cell function in nonobese dogs. Thirteen male mongrel dogs were used in this research study; animals were randomly assigned to surgical treatment with either OM (n = 7), or sham-surgery (SHAM) (n = 6). OM failed to generate measurable changes in body weight (+2%; P = 0.1), or subcutaneous adiposity (+3%; P = 0.83) as assessed by magnetic resonance imaging (MRI). The removal of the greater omentum did not significantly reduce total visceral adipose volume (−7.3 ± 6.4%; P = 0.29); although primary analysis showed a trend for OM to increase SI when compared to sham operated animals (P = 0.078), further statistical analysis revealed that this minor reduction in visceral fat alleviated insulin resistance by augmenting SI of the periphery (+67.7 ± 35.2%; P = 0.03), as determined by the euglycemic-hyperinsulinemic clamp. Insulin secretory response during the hyperglycemic step clamp was not directly influenced by omental fat removal (presurgery 6.82 ± 1.4 vs. postsurgery: 6.7 ± 1.2 pmol/l/mg/dl, P = 0.9). These findings provide new evidence for the deleterious role of visceral fat in insulin resistance, and suggest that a greater OM procedure may effectively improve insulin sensitivity
Temporal variation of cephalopods in the diet of Cape fur seals in Namibia
Cape fur seal (Arctocephalus pusillus pusillus) scats were sampled over a period of eight years (1994-2001) at Atlas and Wolf Bay seal colonies in order to assess the cephalopod component of the diet of these seals and cephalopod diversity off the coast of Namibia. The temporal variation within the cephalopod component was investigated. A low diversity of cephalopods, only six species, are preyed upon, with Todarodes angolensis being the most important component both in numbers and wet weight in all years. Its lowered weight contribution during winter coincided with a greater diversity of other cephalopod species in the diet, which showed higher proportional weight contribution relative to Todarodes angolensis. Scat sampling was found to be an unreliable method of providing estimates of total prey weight consumption by seals, but was considered an acceptable method for proportional comparisons, especially given the ease of scat collection over extended periods
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