T-Parity Violation by Anomalies

Little Higgs theories often rely on an internal parity ("T-parity'') to suppress non-standard electroweak effects or to provide a dark matter candidate. We show that such a symmetry is generally broken by anomalies, as described by the Wess-Zumino-Witten term. We study a simple SU(3) x SU(3)/SU(3) Little Higgs scheme where we obtain a minimal form for the topological interactions of a single Higgs field. The results apply to more general models, including [SU(3) x SU(3)/SU(3)]^4, SU(5)/SO(5), and SU(6)/Sp(6).Comment: 17 page

Z -> b\bar{b} Versus Dynamical Electroweak Symmetry Breaking involving the Top Quark

In models of dynamical electroweak symmetry breaking which sensitively involve the third generation, such as top quark condensation, the effects of the new dynamics can show up experimentally in Z->b\bar{b}. We compare the sensitivity of Z->b\bar{b} and top quark production at the Tevatron to models of the new physics. Z->b\bar{b} is a relatively more sensitive probe to new strongly coupled U(1) gauge bosons, while it is generally less sensitive a probe to new physics involving color octet gauge bosons as is top quark production itself. Nonetheless, to accomodate a significant excess in Z->b\bar{b} requires choosing model parameters that may be ruled out within run I(b) at the Tevatron.Comment: LaTex file, 19 pages + 2 Figs., Fermilab-Pub-94/231-

Student Mastery of Engineering with Design Review

Traditional structural engineering pedagogy has consisted of students preparing for class by reading a textbook, followed by a professor giving a lecture, followed by students doing individual homework. Students received feedback in terms of a grade from the professor, and, ideally, the student filed the graded work and possibly reviewed it again before an exam. Following the exam, the professor moved to the next topic and essentially ended any further contact time with the material, resulting in students quickly dumping a good percentage of what was learned. To make matters worse, most faculty would agree that undergraduate students often skip the reading prior to class, and studies have shown that almost half of all students do not pay attention to material presented during a lecture. Thus, it is critical for engineering educators to improve the stagnant method of traditional teaching and learning. Small mistakes in the engineering profession can lead to death or millions of dollars in repair. For the fall 2018 semester, in the Design of Steel and Wood Structures at the United States Military Academy at West Point, Civil Engineering students participated in a cooperative learning technique aimed at improving student learning. These same students tried a different version of this technique in Structural Analysis the prior semester.[1] Prior to submitting individual homework to the instructor for grade, students paired up with a peer within their class hour and checked each other’s work using an instructor provided “Design Review Sheet.” When a student found a mistake, or disagreed with the methodology used by their Design Review partner, the student annotated this on their sheet. The expectation was that when disagreements were discovered between students, they would discuss with each other where the error or misunderstanding existed and subsequently corrected the error prior to submission for grade. This not only required students to explain the work they completed, but it also provided additional contact time with the material. With respect to Engineering Teaching and Learning, Design Review provides the essential cooperative learning characteristic of positive interdependence because individual student learning increases as review partners improved in their Design Review. As a student incentive to complete a thorough review, the quality of review counted for 10% of each assignment. Efforts this iteration were in response to some of the student suggestions following a previous iteration.[1] This iteration, in lieu of students turning in their work in pairs to receive one grade, each student would turn in their individual work and Design Review sheet. This was done to hold all students accountable for the work they completed. In addition, the instructor provided Design Review sheet was modified for clarity and the requirement to write a memorandum summarizing the results of each Design Review was eliminated. This cooperative learning technique was used on six of seven homework assignments during the term and on seven of nine homework assignments in their pre-requisite course. Student feedback was collected from both Likert Scale questions and open-ended questions. This paper will make the case that this pedagogy benefits Engineering Teaching and Learning by: (1) getting engineering students in the practice of what engineers in practice already do (check each other’s work), (2) increasing student learning of course learning objectives through repetition and through observing how others solve problems and present their work, and (3) improving the ability of future engineers to communicate their work clearly and effectively.Cockrell School of Engineerin

Nickel layers on indium arsenide

We report here on the preparation and characterization of InAs substrates for in situ deposition of ferromagnetic contacts, a necessary precursor for semiconductor devices based on spin injection. InAs has been grown on InAs(111)A and (100) substrates by molecular-beam epitaxy and then metalized in situ in order to better understand the mechanisms that inhibit spin injection into a semiconductor. Initial x-ray characterization of the samples indicate the presence of nickel arsenides and indium–nickel compounds forming during deposition at temperatures above room temperature. Several temperature ranges have been investigated in order to determine the effect on nickel-arsenide formation. The presence of such compounds at the interface could greatly reduce the spin-injection efficiency and help elucidate previous unsuccessful attempts at measuring spin injection into InAs

Chiral Hierarchies, Compositeness and the Renormalization Group

A wide class of models involve the fine--tuning of significant hierarchies between a strong--coupling ``compositeness'' scale, and a low energy dynamical symmetry breaking scale. We examine the issue of whether such hierarchies are generally endangered by Coleman--Weinberg instabilities. A careful study using perturbative two--loop renormalization group methods finds that consistent large hierarchies are not generally disallowed.Comment: 22 pp + 5 figs (uuencoded and submitted separately), SSCL-Preprint-490; FERMI-PUB-93/035-

Adhesive for aluminum withstands cryogenic temperatures

Polyurethane adhesive mixed to various proportions with milled glass fibers match the thermal characteristics of 2014-T6 aluminum at cryogenic temperatures

Dynamics of Domain Walls for Split and Runaway Potentials

We demonstrate that the evolution of wall-like inhomogeneities in run-away potentials, characteristic of dynamical supersymmetry breaking and moduli stabilisation, is very similar to the evolution of domain wall networks associated with double well potentials. Instabilities that would lead to a rapid decay of domain walls can be significantly ameliorated by compensation effects between a non-degeneracy of the vacua and a biased initial distribution, which can be naturally expected in a wide class or particle physics models that lead to out-of-equilibrium phase transitions. Within this framework, it is possible to obtain domain walls that live long enough to be relevant for the cosmic power spectrum and galaxy clustering, while being compatible with the observed cosmic microwave background anisotropies.Comment: 30 pages, 9 figure

Scanning apertureless microscopy below the diffraction limit: Comparisons between theory and experiment

The exact nature of the signal in scanning apertureless microscopy techniques is the subject of much debate. We have sought to resolve this controversy by carrying out simulations and experiments on the same structures. Simulations of a model of tip–sample coupling are shown to exhibit features that are in agreement with experimental observations at dimensions below the diffraction limit. The simulation of the optical imaging process is carried out using atomic force microscope data as a topographical template and a tip–sample dipole coupling model as the source of optical signal. The simulations show a number of key fingerprints including a dependence on the polarization of the external laser source, the size of the tip, and index of refraction of the sample being imaged. The experimental results are found to be in agreement with many of the features of the simulations. We conclude that the results of the dipole coupling theory agree qualitatively with experimental data and that apertureless microscopy measures optical properties, not just topography

Search for Narrow-Width ttbar Resonances in ppbar Collisions at center of mass energy = 1.8 TeV

We present a preliminary result on a search for narrow-width resonances that decay into ttbar pairs using 130 pb^{-1} of lepton plus jets data in ppbar collisions at center of mass energy = 1.8 TeV. No significant deviation from Standard Model prediction is observed. 95% C.L. upper limits on the production cross section of the narrow-width resonance times its branching fraction to ttbar are presented for different resonance masses, M_X. We also exclude the existence of a leptophobic topcolor particle, X, with M_X < 560 GeV/c^2 for a width \Gamma_X = 0.012 M_X.Comment: 3 pages, 1 figure; Submitted for proceedings of 5th International Conference on Quark Confinement and Hadron spectrum, held in Italy, from 11-14 Sep., 200