Conformal Field Theories, Representations and Lattice Constructions

An account is given of the structure and representations of chiral bosonic meromorphic conformal field theories (CFT's), and, in particular, the conditions under which such a CFT may be extended by a representation to form a new theory. This general approach is illustrated by considering the untwisted and $Z_2$-twisted theories, $H(\Lambda)$ and $\tilde H(\Lambda)$ respectively, which may be constructed from a suitable even Euclidean lattice $\Lambda$. Similarly, one may construct lattices $\Lambda_C$ and $\tilde\Lambda_C$ by analogous constructions from a doubly-even binary code $C$. In the case when $C$ is self-dual, the corresponding lattices are also. Similarly, $H(\Lambda)$ and $\tilde H(\Lambda)$ are self-dual if and only if $\Lambda$ is. We show that $H(\Lambda_C)$ has a natural ``triality'' structure, which induces an isomorphism $H(\tilde\Lambda_C)\equiv\tilde H(\Lambda_C)$ and also a triality structure on $\tilde H(\tilde\Lambda_C)$. For $C$ the Golay code, $\tilde\Lambda_C$ is the Leech lattice, and the triality on $\tilde H(\tilde\Lambda_C)$ is the symmetry which extends the natural action of (an extension of) Conway's group on this theory to the Monster, so setting triality and Frenkel, Lepowsky and Meurman's construction of the natural Monster module in a more general context. The results also serve to shed some light on the classification of self-dual CFT's. We find that of the 48 theories $H(\Lambda)$ and $\tilde H(\Lambda)$ with central charge 24 that there are 39 distinct ones, and further that all 9 coincidences are accounted for by the isomorphism detailed above, induced by the existence of a doubly-even self-dual binary code.Comment: 65 page

On the Relationship between the Uniqueness of the Moonshine Module and Monstrous Moonshine

We consider the relationship between the conjectured uniqueness of the Moonshine Module, ${\cal V}^\natural$, and Monstrous Moonshine, the genus zero property of the modular invariance group for each Monster group Thompson series. We first discuss a family of possible $Z_n$ meromorphic orbifold constructions of ${\cal V}^\natural$ based on automorphisms of the Leech lattice compactified bosonic string. We reproduce the Thompson series for all 51 non-Fricke classes of the Monster group $M$ together with a new relationship between the centralisers of these classes and 51 corresponding Conway group centralisers (generalising a well-known relationship for 5 such classes). Assuming that ${\cal V}^\natural$ is unique, we then consider meromorphic orbifoldings of ${\cal V}^\natural$ and show that Monstrous Moonshine holds if and only if the only meromorphic orbifoldings of ${\cal V}^\natural$ give ${\cal V}^\natural$ itself or the Leech theory. This constraint on the meromorphic orbifoldings of ${\cal V}^\natural$ therefore relates Monstrous Moonshine to the uniqueness of ${\cal V}^\natural$ in a new way.Comment: 53 pages, PlainTex, DIAS-STP-93-0

Brownian motion exhibiting absolute negative mobility

We consider a single Brownian particle in a spatially symmetric, periodic system far from thermal equilibrium. This setup can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility).Comment: 4 pages, 3 figures, to be published in PR

Global cost and weight evaluation of fuselage keel design concepts

The Boeing program entitled Advanced Technology Composite Aircraft Structure (ATCAS) is focused on the application of affordable composite technology to pressurized fuselage structure of future aircraft. As part of this effort, a design study was conducted on the keel section of the aft fuselage. A design build team (DBT) approach was used to identify and evaluate several design concepts which incorporated different material systems, fabrication processes, structural configurations, and subassembly details. The design concepts were developed in sufficient detail to accurately assess their potential for cost and weight savings as compared with a metal baseline representing current wide body technology. The cost and weight results, along with an appraisal of performance and producibility risks, are used to identify a globally optimized keel design; one which offers the most promising cost and weight advantages over metal construction. Lastly, an assessment is given of the potential for further cost and weight reductions of the selected keel design during local optimization

G(2) quivers

We present, in explicit matrix representation and a modernity befitting the community, the classification of the finite discrete subgroups of G2 and compute the McKay quivers arising therefrom. Of physical interest are the classes of Script N = 1 gauge theories descending from M-theory and of mathematical interest are possible steps toward a systematic study of crepant resolutions to smooth G2 manifolds as well as generalised McKay Correspondences. This writing is a companion monograph to hep-th/9811183 and hep-th/9905212, wherein the analogues for Calabi-Yau three- and four-folds were considered

Global Cost and Weight Evaluation of Fuselage Side Panel Design Concepts

This report documents preliminary design trades conducted under NASA contracts NAS1 18889 (Advanced Technology Composite Aircraft Structures, ATCAS) and NAS1-19349 (Task 3, Pathfinder Shell Design) for a subsonic wide body commercial aircraft fuselage side panel section utilizing composite materials. Included in this effort were (1) development of two complete design concepts, (2) generation of cost and weight estimates, (3) identification of technical issues and potential design enhancements, and (4) selection of a single design to be further developed. The first design concept featured an open-section stringer stiffened skin configuration while the second was based on honeycomb core sandwich construction. The trade study cost and weight results were generated from comprehensive assessment of each structural component comprising the fuselage side panel section from detail fabrication through airplane final assembly. Results were obtained in three phases: (1) for the baseline designs, (2) after global optimization of the designs, and (3) the results anticipated after detailed design optimization. A critical assessment of both designs was performed to determine the risk associated with each concept, that is the relative probability of achieving the cost and weight projections. Seven critical technical issues were identified as the first step towards side panel detailed design optimization

Characterising online museum users: a study of the National Museums Liverpool museum website

Museums are increasing access to their collections and providing richer user experiences via web-based interfaces. However, they are seeing high numbers of users looking at only one or two pages within 10 s and then leaving. To reduce this rate, a better understanding of the type of user who visits a museum website is required. Existing models for museum website users tend to focus on groups that are readily accessible for study or provide little detail in their definitions of the groups. This paper presents the results of a large-scale user survey for the National Museums Liverpool museum website in which data on a wide range of user characteristics were collected regarding their current visit to provide a better understanding of their motivations, tasks, engagement and domain knowledge. Results show that the frequently understudied general public and non-professional users make up the majority (approximately 77%) of the respondents

SHIP-Deficient Dendritic Cells, Unlike Wild Type Dendritic Cells, Suppress T Cell Proliferation via a Nitric Oxide-Independent Mechanism

Dendritic cells (DCs) not only play a crucial role in activating immune cells but also suppressing them. We recently investigated SHIP's role in murine DCs in terms of immune cell activation and found that TLR agonist-stimulated SHIP-/- GM-CSF-derived DCs (GM-DCs) were far less capable than wild type (WT, SHIP+/+) GM-DCs at activating T cell proliferation. This was most likely because SHIP-/- GM-DCs could not up-regulate MHCII and/or co-stimulatory receptors following TLR stimulation. However, the role of SHIP in DC-induced T cell suppression was not investigated.In this study we examined SHIP's role in DC-induced T cell suppression by co-culturing WT and SHIP-/- murine DCs, derived under different conditions or isolated from spleens, with αCD3+ αCD28 activated WT T cells and determined the relative suppressive abilities of the different DC subsets. We found that, in contrast to SHIP+/+ and -/- splenic or Flt3L-derived DCs, which do not suppress T cell proliferation in vitro, both SHIP+/+ and -/- GM-DCs were capable of potently suppressing T cell proliferation. However, WT GM-DC suppression appeared to be mediated, at least in part, by nitric oxide (NO) production while SHIP-/- GM-DCs expressed high levels of arginase 1 and did not produce NO. Following exhaustive studies to ascertain the mechanism of SHIP-/- DC-mediated suppression, we could conclude that cell-cell contact was required and the mechanism may be related to their relative immaturity, compared to SHIP+/+ GM-DCs.These findings suggest that although both SHIP+/+ and -/- GM-DCs suppress T cell proliferation, the mechanism(s) employed are different. WT GM-DCs suppress, at least in part, via IFNγ-induced NO production while SHIP-/- GM-DCs do not produce NO and suppression can only be alleviated when contact is prevented