The uses of Connes and Kreimer's algebraic formulation of renormalization theory

We show how, modulo the distinction between the antipode and the "twisted" or "renormalized" antipode, Connes and Kreimer's algebraic paradigm trivializes the proofs of equivalence of the (corrected) Dyson-Salam, Bogoliubov-Parasiuk-Hepp and Zimmermann procedures for renormalizing Feynman amplitudes. We discuss the outlook for a parallel simplification of computations in quantum field theory, stemming from the same algebraic approach.Comment: 15 pages, Latex. Minor changes, typos fixed, 2 references adde

A study of the Mg II 2796.34 A emission line in late--type normal, and RS CVn stars

We carry out an analysis of the Mg II 2796.34 A emission line in RS CVn stars and make a comparison with the normal stars studied in a previous paper (Paper I). The sample of RS CVn stars consists of 34 objects with known HIPPARCOS parallaxes and observed at high resolution with IUE. We confirm that RS CVn stars tend to possess wider Mg II lines than normal stars having the same absolute visual magnitude. However, we could not find any correlation between the logarithmic line width log Wo and the absolute visual magnitude Mv (the Wilson--Bappu relationship) for these active stars, contrary to the case of normal stars addressed in Paper I. On the contrary, we find that a strong correlation exists in the (Mv, log L) plane (L is the absolute flux in the line). In this plane, normal and RS CVn stars are distributed along two nearly parallel straight lines with RS CVn stars being systematically brighter by about 1 dex. Such a diagram provides an interesting tool to discriminate active from normal stars. We finally analyse the distribution of RS CVn and of normal stars in the (log L, log Wo) plane, and find a strong linear correlation for normal stars, which can be used for distance determinations.Comment: 10 pages, 7 figures, latex, to be published in A&

IIB solutions with N>28 Killing spinors are maximally supersymmetric

We show that all IIB supergravity backgrounds which admit more than 28 Killing spinors are maximally supersymmetric. In particular, we find that for all N>28 backgrounds the supercovariant curvature vanishes, and that the quotients of maximally supersymmetric backgrounds either preserve all 32 or N<29 supersymmetries.Comment: 27 page

Parallelisable Heterotic Backgrounds

We classify the simply-connected supersymmetric parallelisable backgrounds of heterotic supergravity. They are all given by parallelised Lie groups admitting a bi-invariant lorentzian metric. We find examples preserving 4, 8, 10, 12, 14 and 16 of the 16 supersymmetries.Comment: 17 pages, AMSLaTe

Archeological Testing of the Pavo Real Site (41BX52), San Antonio, Bexar County, Texas

The Center for Archaeological Research (CAR) at the University of Texas at San Antonio performed archeological testing at the Pavo Real site (41BX52) between November 2006 and June 2007 for HNTB. The purpose of archeological testing was to determine the depth of construction fill and the presence, location and, if possible, condition, of any remnant archeological deposits. Proposed improvements along Loop 1604 include bridge bents that will be constructed east of Leon Creek and west of the IH-10/Loop 1604 interchange overpass. Impacts associated with proposed improvements will occur within the boundaries and in the immediate vicinity of 41BX52. Archeological testing consisted of coring, backhoe trenching and block excavations. Coring and backhoe trenching within the northern and southern medians indicated the presence of thick fill material of unknown depths in the western portion of the site and a decrease in fill and soils on the eastern segment. Suite II soils, that were assumed to be associated with the first occupation of the site, were identified during backhoe trenching, initiating block excavations. Block excavations were conducted within the area to be directly impacted by a bridge bent and basin in aims of dating Suite II soils. The excavation of two 2-x-2-meter (m) blocks and two additional 1-x-1-m units produced Early Archaic diagnostics. Paleoindian period materials were not encountered during archeological investigations of the site. Two samples collected from Block 2 excavations yielded single grain OSL ages of 18,300±920 years BP and 18,200±1,030 years BP. Statistical analysis concluded that lithic debitage recovered from the Suite II deposits were significantly smaller than Suites III and IV specimens, supporting the conclusion that cultural material from Suite III could have worked their way down into the deposit accounting for the specimens present in Suite II. Moreover, OSL results suggested that Suite II deposits may have undergone post-depositional disturbance. Archeological testing of the site was conducted under Texas Antiquities permit No. 4092. The initial coring and trenching of the site was conducted under a TxDOT General Services Contract with Raymond P. Mauldin serving as the principal investigator. The subsequent testing was performed under a contract with HNTB with Steve Tomka serving as the principal investigator. Antonia L. Figueroa served as the project archeologist. Charles D. Frederick served as the project geoarcheologist. All artifacts and records collected during this project are curated at the Center for Archaeological Research according to Texas Historical Commission guidelines