Baryon Number Violating Transitions in String Backgrounds

We construct field configurations that interpolate between string background states of differing baryon number. Using these configurations we estimate the effect of the background fields on the energy barrier separating different vacua. In the background of a superconducting GUT string the energy barrier is increased, while in an electroweak string background or the electroweak layer of a non-superconducting string the energy barrier is reduced. The energy barrier depends sensitively on both the background gauge and scalar fields.Comment: 27 pages. Texing problems fixe

Measuring, Modeling, and Evaluating the Spatial Properties of Northeast Oregon Forests Using Unmanned Aerial Systems

There is an ever expanding range of applications for the aerial images that unmanned aerial systems can uniquely provide. One such application is the use of high-resolution imagery for stand-level forest inventory. Inventory techniques utilizing unmanned aerial systems could be attractive where conditions demand high-resolution data, or where other aerial imagery sources are cost prohibitive. Here the effectiveness of unmanned aerial systems in this application was tested. Over the summer of 2015, a remote-controlled hexacopter equipped with a micro four thirds camera was flown over multiple 1600 meter-squared forested plots in Eastern Oregon. Additional ground-level validation measurements were collected including stem location, crown radius, and tree height. Agisoft Photoscan was used to construct 3-D point-clouds which then allowed the production of digital surface models of the stands. The first section of this project assesses the accuracy of stem locations derived from segmented imagery. The next section evaluates the accuracy of estimates for tree height, crown radius, and diameter at breast height. In the final section, various spatial metrics such as stand contagion and species mingling were compared with more commonly used metrics to see if significant correlations emerged. The utilized methods did not yield sufficiently accurate estimates for stem location or the various forest biometrics. Yet this work revealed stand density to be a significant influence on model accuracy. Finally, stand density and species diversity were found to be well correlated with the nearest neighbor and species mingling indexes, respectively, potentially supporting a complementary relationship indicating the clustering of various factors within the stand

Stability of an electroweak string with a fermion condensate

A solution of the standard electroweak theory with a single lepton family is constructed, consisting of a cosmic string and a fermion condensate within its core. The stability of this system to small perturbations is examined, and it is found that stability is not enhanced relative to the bare electroweak string. The presence of quark zero modes is shown to violate the existence criteria for embedded defects.Comment: 13 pages, preprint DAMTP 94-9, SWAT/2

Perturbative expansion of N<8 Supergravity

We characterise the one-loop amplitudes for N=6 and N=4 supergravity in four dimensions. For N=6 we find that the one-loop n-point amplitudes can be expanded in terms of scalar box and triangle functions only. This simplification is consistent with a loop momentum power count of n-3, which we would interpret as being n+4 for gravity with a further -7 from the N=6 superalgebra. For N=4 we find that the amplitude is consistent with a loop momentum power count of n, which we would interpret as being n+4 for gravity with a further -4 from the N=4 superalgebra. Specifically the N=4 amplitudes contain non-cut-constructible rational terms.Comment: 13 pages. v2 adds analytic expression for rational parts of 5-pt 1-loop N=4 SUGRA amplitude; v3 normalisations clarifie

Obtaining One-loop Gravity Amplitudes Using Spurious Singularities

The decomposition of a one-loop scattering amplitude into elementary functions with rational coefficients introduces spurious singularities which afflict individual coefficients but cancel in the complete amplitude. These cancellations create a web of interactions between the various terms. We explore the extent to which entire one-loop amplitudes can be determined from these relationships starting with a relatively small input of initial information, typically the coefficients of the scalar integral functions as these are readily determined. In the context of one-loop gravity amplitudes, of which relatively little is known, we find that some amplitudes with a small number of legs can be completely determined from their box coefficients. For increasing numbers of legs, ambiguities appear which can be determined from the physical singularity structure of the amplitude. We illustrate this with the four-point and N=1,4 five-point (super)gravity one-loop amplitudes.Comment: Minor corrections. Appendix adde

The n-point MHV one-loop Amplitude in N=4 Supergravity

We present an explicit formula for the n-point MHV one-loop amplitude in a N=4 supergravity theory. This formula is derived from the soft and collinear factorisations of the amplitude.Comment: 8 pages; v2 References added. Minor changes to tex

Investigation of the tendencies in class-room practices in high school mathematics (As determined by a study of college board examinations and tests given in high school),

Thesis (M.A.)--Boston University, 1932. This item was digitized by the Internet Archive