Nucleation of vacuum phase transitions by topological defects

The Euclidean action is calculated in the thin-wall approximation for a first-order vacuum phase transition in which the bubble appears symmetrically around either a global monopole or a gauge cosmic string. The bubble is assumed to be much larger than the core size of the monopole or string. In both cases the value of the Euclidean action is shown to be reduced below the $O(4)$ symmetric action value, indicating that the topological defects act as effective nucleation sites for vacuum decay.Comment: 10 pages, LaTe

Liquid-gas and other unusual thermal phase transitions in some large-N magnets

Much insight into the low temperature properties of quantum magnets has been gained by generalizing them to symmetry groups of order N, and then studying the large N limit. In this paper we consider an unusual aspect of their finite temperature behavior--their exhibiting a phase transition between a perfectly paramagetic state and a paramagnetic state with a finite correlation length at N = \infty. We analyze this phenomenon in some detail in the large ``spin'' (classical) limit of the SU(N) ferromagnet which is also a lattice discretization of the CP^{N-1} model. We show that at N = \infty the order of the transition is governed by lattice connectivity. At finite values of N, the transition goes away in one or less dimension but survives on many lattices in two dimensions and higher, for sufficiently large N. The latter conclusion contradicts a recent conjecture of Sokal and Starinets, yet is consistent with the known finite temperature behavior of the SU(2) case. We also report closely related first order paramagnet-ferromagnet transitions at large N and shed light on a violation of Elitzur's theorem at infinite N via the large q limit of the q-state Potts model, reformulated as an Ising gauge theory.Comment: 27 pages, 7 figures. Added clarifications requested by a refere

N-utilization by cattle fed rations consisting mainly of biuret and low quality hay and factors affecting N-utilization by cattle fed urea-corn silage rations

Two successive 7-day total-collection digestion and nitrogen (N) metabolism trials were conducted with beef steers to compare biuret with urea and to determine if other ration constituents influence utilization of N furnished by biuret. Twelve medium grade Hereford steers averaging 221 kg in body weight were allotted to one of the following treatments: 1) urea control; 2) biuret control; 3) biuret-molasses; and 4) biuret-corn. All animals received a basal ration of poor-quality fescue hay and were allowed 42 days to adapt to the NPN source before the start of the first trial. A comparison of the data from the two trials indicated nutrient digestibility (dry matter, crude protein and gross energy) was not affected by NPN source. However, the addition of readily-fermentable energy (molasses, cornmeal) increased digestibility of all nutrients. Dry matter and gross energy digestibility of rations containing biuret and additional energy were significantly (P \u3c .10) higher than of the urea and biuret control rations. Nitrogen digestibility was non-signif-icantly higher in rations containing additional energy than in both control rations. The percent absorbed N retained by animals consuming all types of biuret rations was lower than that by animals consuming the urea ration. The difference was from 6 to 8 percentage units, but was not significant (P \u3c .10). Net protein utilization and percent intake N retained, which take into account digestibility, followed essentially the same pattern as percent absorbed N retained. They did, however, reflect the advantage of additional energy on digestibility. Another experiment was conducted to determine the pattern of peripheral blood ammonia and urea as a function of time after feeding. Six animals, used previously in metabolism trials, and six unadapted to NPN, were allotted to one of the following treatments; 1) urea-adapted; 2) biuret-adapted; 3) urea-unadapted; or 4) biuret-unadapted. Rations consisted of long timothy hay, blackstrap molasses and either urea or biuret. NPN comprised approximately 1.5 percent of the ration. Jugular blood samples were taken at intervals of 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours and 6 hours after feeding. An incomplete Latin Square design was used for sampling. Adapted animals consuming urea had the highest blood ammonia levels. Blood from animals of other treatments all contained approximately the same level of ammonia within all treatments, peak ammonia-N levels appeared at one hour after feeding. Plasma urea levels were fairly constant for all animals, averaging approximately 12-14 mg per ICQ ml plasma. There was, however, a gradual increase in plasma urea from 2 to 6 hours Data from six total-collection digestion and N-metabolism trials with steers were compiled to examine some factors affecting ration digestibility and N-utilization of urea-corn silage based rations. F-max tests indicated homogeneity of variances among the trials. Multiple regression equations were developed to determine the effect of various ration constituents and intake parameters on nutrient digestibility and efficiency of N-metabolism. Calorie to protein ratio, grams N intake, percent digestible NFE and ration dry matter content together accounted for 51, 46 and 74 percent of the total variability in the apparent digestibility of dry matter, crude protein and crude fiber, respectively. Increasing calorie to protein ratio resulted in a decrease of apparent digestibilities of dry matter and nitrogen, and an increase in diges-tibility of crude fiber. Nitrogen intake was associated negatively with digestibility. Increasing ration dry matter content increased dry matter and crude fiber digestibility and decreased that of crude protein. When percent absorbed N retained, percent intake N retained and net protein utilization were the dependent variables, their regression on the four independent variables: 1) percentage of ration N supplied by urea; 2) energy supplied by concentrates; 3) N intake; and 4) fiber intake accounted for 34, 18 and 20 percent respectively, of the total variability in the three dependent variables. Percentage of N supplied by urea and N intake had no significant effect on any measure of N-metabolism. When energy supplied by concentrates increased from 3.8 to 11.3 mcal/day, retention of absorbed N, retention of intake N and net protein utilization increased 15.7 (significant, P \u3c .001), 5.7 and 7.5 (significant, P \u3c .05) percentage units, respectively. In-creased fiber intake was associated with significantly (P \u3c .05) decreased retention of intake N and net protein utilization. There was little effect of fiber intake on retention of absorbed N

True selective grazing exhibited by beef cattle as determined after adjusting for esophageal fistula effects

During the spring, summer, and fall of 1965, 1966, and 1967 grazing trials with beef cattle were conducted to study the effects of selective grazing on chemical composition and dry matter digestibility of pasture forage samples. Samples collected from esophageal-fistulated animals were adjusted for losses of leached-out nutrients, mainly nitrogen-free extract and ether extract (NFE + EE), and for artificial increases (due to the loss of other nutrients) in the percentage of acid-detergent fiber (ADF). Two types of pasture species combinations, tall fescue-lespedeza and orchardgrass-Ladino clover, were used in this study. The chemical composition and dry matter digestibility of forage samples selected by grazing animals were compared to the composition and digestibility of forage samples hand-clipped from the same pastures, which represented the average of the available forage. The differences between these two types of pasture samples were attributed to selectivity. The results of this study indicate that grazing animals select forage higher in crude protein and lower in ADF and NFE than the average of the available forage. The differences were significant (P \u3c.05) for all components from tall fescue and lespedeza pastures but differences for ADF from orchardgrass and Ladino clover pastures were significant only at the 90 percent level of probability. The greatest degree of selectivity was observed in June and July and the lowest was observed in August and September for tall fescue and lespedeza pastures. Similar patterns were observed for the orchardgrass and Ladino clover pastures except that the lowest degree of selection occurred in September. Also, the grazing animals exhibited greater selection while grazing fescue and lespedeza pastures

Coupling supergravity to non-supersymmetric matter

By introducing a nonlinearly transforming goldstino field non-super\-sym\-metric matter can be coupled to supergravity. This implies the possibility of coupling a standard model with one Higgs to supergravity.Comment: 11 pages, LATEX, references adde

Chiral Symmetry restoration in the massive Thirring model at finite T and μ\mu: Dimensional reduction and the Coulomb gas

We show that in certain limits the (1+1)-dimensional massive Thirring model at finite temperature $T$ is equivalent to a one-dimensional Coulomb gas of charged particles at the same $T$. This equivalence is then used to explore the phase structure of the massive Thirring model. For strong coupling and $T>>m$ (the fermion mass) the system is shown to behave as a free gas of "molecules" (charge pairs in the Coulomb gas terminology) made of pairs of chiral condensates. This binding of chiral condensates is responsible for the restoration of chiral symmetry as $T\to\infty$. In addition, when a fermion chemical potential $\mu\neq 0$ is included, the analogy with a Coulomb gas still holds with $\mu$ playing the role of a purely imaginary external electric field. For small $T$ and $\mu$ we find a typical massive Fermi gas behaviour for the fermion density, whereas for large $\mu$ it shows chiral restoration by means of a vanishing effective fermion mass. Some similarities with the chiral properties of low-energy QCD at finite $T$ and baryon chemical potential are discussed.Comment: 28 pages, 6 figures, better resolution figures are available upon reques

Feature Based Approaches for Homography Estimation

Image stitching is a method of producing a wider field of view by combining several overlapping images. With four main stages in the image stitching process, the algorithms used at each stage can have a dramatic impact on the success of stitching an image. For each stage, there are a wide range of algorithms to choose from and it can be a challenge to identify a stitching pipeline that will produce the best results. In this paper, we study the approaches involved in each of the four stages of image stitching. A real-world dataset is utilised to evaluate each algorithm, where images are transformed to different perspectives. The similarities of these images are compared to a warped perspective image obtained using the homographies provided by the dataset. The pipelines tested were limited to producing accurate results up to and including a 50° perspective change. Pipelines utilising BRISK’s feature detector, FREAK, and Brute Force produced significant results. However, pipelines incorporating ORB, FAST, or BRIEF produce poor results when compared to other feature detection and feature description algorithms. Generally, the ratio test hindered the matched pairs process, although there were exceptions. Finally, the inlier/outlier detection algorithms, USAC and RANSAC, had similar performances with no definitive data to suggest that, in general, one outperforms the other

Book for the Children of Maine, For the Use of Families and Schools

https://digitalcommons.usm.maine.edu/oml_collections/1013/thumbnail.jp