The Strength of Non-Perturbative Effects in Matrix Models and String Effective Lagrangians

We present a summary of the results of an explicit calculation of the strength of non-perturbative interactions in matrix models and string effective Lagrangians. These interactions are induced by single eigenvalue instantons in the $d=1$ bosonic matrix model. A well defined approximation scheme is used to obtain induced operators whose exact form we exhibit. We briefly discuss the possibility that similar instantons in a supersymmetric version of the theory may break supersymmetry dynamically.Comment: Latex document, 17 pages, preprint CERN-TH.7356/94, UPR-620

Supersymmetric Field Theory from Supermatrix Models

We show that the continuum limit of one-dimensional N=2 supersymmetric matrix models can be described by a two-dimensional interacting field theory of a massless boson and two chiral fermions. We interpret this field theory as a two-dimensional N=1 supersymmetric theory of two chiral superfields, in which one of the chiral superfields has a non-trivial vacuum expectation value.Comment: Latex document, 11 pages, preprint CERN-TH.7353/94, UPR-621

A BPS Interpretation of Shape Invariance

We show that shape invariance appears when a quantum mechanical model is invariant under a centrally extended superalgebra endowed with an additional symmetry generator, which we dub the shift operator. The familiar mathematical and physical results of shape invariance then arise from the BPS structure associated with this shift operator. The shift operator also ensures that there is a one-to-one correspondence between the energy levels of such a model and the energies of the BPS-saturating states. These findings thus provide a more comprehensive algebraic setting for understanding shape invariance.Comment: 15 pages, 2 figures, LaTe

Evaluating Podcast Compositions: Assessing Credibility, Challenges, and Innovation

With digital technology becoming a common feature in the classroom and research, podcasts become a valuable reference for both. Whether used as primary source material, illustrating faculty development, or functioning as a multi-media resource in the classroom, assessment tools are needed to evaluate podcasts. Current evaluation tools tend to focus on the production; therefore, an analytical framework focusing the quality of information presented via podcasts for use in research or as a teaching tool in the classroom is warranted. The guideline discussed in this project is based on five factors, each of which has a number of indicators to help gauge its quality and worth. The proposed rubric is a helpful tool that aids in the building of digital ethos for potential audiences outside the academy enabling action based learning and or community impact.

Interactions between fibroblast growth factors and Notch regulate neuronal differentiation

The differentiation of precursor cells into neurons has been shown to be influenced by both the Notch signaling pathway and growth factor stimulation. In this study, the regulation of neuronal differentiation by these mechanisms was examined in the embryonic day 10 neuroepithelial precursor (NEP) population. By downregulating Notch1 expression and by the addition of a Delta1 fusion protein (Delta Fc), it was shown that signaling via the Notch pathway inhibited neuron differentiation in the NEP cells, in vitro. The expression of two of the Notch receptor homologs, Notch1 and Notch3, and the ligand Delta1 in these NEP cells was found to be influenced by a number of different growth factors, indicating a potential interaction between growth factors and Notch signaling. Interestingly, none of the growth factors examined promoted neuron differentiation; however, the fibroblast growth factors (FGFs) 1 and 2 potently inhibited differentiation. FGF1 and FGF2 upregulated the expression of Notch and decreased expression of Delta1 in the NEP cells. In addition, the inhibitory response of the cells to the FGFs could be overcome by downregulating Notch1 expression and by disrupting Notch cleavage and signaling by the ablation of the Presenilin1 gene. These results indicate that FGF1 and FGF2 act via the Notch pathway, either directly or indirectly, to inhibit differentiation. Thus, signaling through the Notch receptor may be a common regulator of neuronal differentiation within the developing forebrain

Mechanical failure characterization of optical components caused by laser induced damage initiated at contaminants

The goal of this research is to quantify by numerical techniques the effects of surface and subsurface absorbing defects on damage initiation and growth in high power laser optical components. The defects include laser absorbing spots (e.g., surface particulate contamination) and surface damage regions (e.g., micro-cracks and voids) which are present due to environmental exposure and fabrication processes. This report focuses on three sources of contamination that can cause damage to optical components: (1) Front surface particle contamination, (2) Back surface particle contamination, and (3) Subsurface particle contamination. The DYNA2D (non-linear structural mechanics) code was used to model the growth of damage in the glass substrate. The damage in the nominally transparent glass substrate as a result of front surface particle contamination was found to be dependent on the magnitude of the resultant pressure pulse applied to the particle and the initial area of contact between the particle and glass substrate. The pressures generated from a back surface particle being blown off the surface provided sufficient loading to severely damage (crack) the glass substrate. A subsurface Ceria dioxide particle showed a strong surface interaction that influenced the formation and direction of the damage (cracking) that ultimately resulted in the blow-out of the damaged material leaving a relatively clean crater in the glass. Crater shape and size was determined. Since fused silica is the most transparent, and therefore laser damage resistant, of the optical materials, it is used for the most at-risk optical elements. The present studies are for a fused silica substrate. Some oxides such as Ceria are transparent in the infrared and visible, but absorbing in the UV part of the spectrum. Because ICF lasers like NIF use frequency tripling, effects of such oxides must be included

Codes and Supersymmetry in One Dimension

Adinkras are diagrams that describe many useful supermultiplets in D=1 dimensions. We show that the topology of the Adinkra is uniquely determined by a doubly even code. Conversely, every doubly even code produces a possible topology of an Adinkra. A computation of doubly even codes results in an enumeration of these Adinkra topologies up to N=28, and for minimal supermultiplets, up to N=32.Comment: 48 pages, a new version that combines arXiv:0811.3410 and parts of arXiv:0806.0050, for submission for publicatio

Effective Symmetries of the Minimal Supermultiplet of N = 8 Extended Worldline Supersymmetry

A minimal representation of the N = 8 extended worldline supersymmetry, known as the `ultra-multiplet', is closely related to a family of supermultiplets with the same, E(8) chromotopology. We catalogue their effective symmetries and find a Spin(4) x Z(2) subgroup common to them all, which explains the particular basis used in the original construction. We specify a constrained superfield representation of the supermultiplets in the ultra-multiplet family, and show that such a superfield representation in fact exists for all adinkraic supermultiplets. We also exhibit the correspondences between these supermultiplets, their Adinkras and the E(8) root lattice bases. Finally, we construct quadratic Lagrangians that provide the standard kinetic terms and afford a mixing of an even number of such supermultiplets controlled by a coupling to an external 2-form of fluxes.Comment: 13 Figure