Extension Bundles and the Standard Model

We construct a new class of stable vector bundles suitable for heterotic string compactifications. Using these we describe a novel way to derive the fermionic matter content of the Standard Model from the heterotic string. For this we compactify on an elliptically fibered Calabi-Yau threefold X with two sections, the B-fibration, a variant of the ordinary Weierstrass fibration, which allows X to carry a free involution. We construct rank five vector bundles, invariant under this involution, such that turning on a Wilson line we obtain the Standard Model gauge group and find various three generation models. This rank five bundle is derived from a stable rank four bundle that arises as an extension of bundles pulled-back from the base and twisted by suitable line bundles. We also give an account of various previous results and put the present construction into perspective.Comment: 31 pages, harvmac, references adde

SU(5) Heterotic Standard Model Bundles

We construct a class of stable SU(5) bundles on an elliptically fibered Calabi-Yau threefold with two sections, a variant of the ordinary Weierstrass fibration, which admits a free involution. The bundles are invariant under the involution, solve the topological constraint imposed by the heterotic anomaly equation and give three generations of Standard Model fermions after symmetry breaking by Wilson lines of the intermediate SU(5) GUT-group to the Standard Model gauge group. Among the solutions we find some which can be perturbed to solutions of the Strominger system. Thus these solutions provide a step toward the construction of phenomenologically realistic heterotic flux compactifications via non-Kahler deformations of Calabi-Yau geometries with bundles. This particular class of solutions involves a rank two hidden sector bundle and does not require background fivebranes for anomaly cancellation.Comment: 17 page

Bootstrapping Mixed Correlators in Three-Dimensional Cubic Theories

Three-dimensional theories with cubic symmetry are studied using the machinery of the numerical conformal bootstrap. Crossing symmetry and unitarity are imposed on a set of mixed correlators, and various aspects of the parameter space are probed for consistency. An isolated allowed region in parameter space is found under certain assumptions involving pushing operator dimensions above marginality, indicating the existence of a conformal field theory in this region. The obtained results have possible applications for ferromagnetic phase transitions as well as structural phase transitions in crystals. They are in tension with previous $\varepsilon$ expansion results, as noticed already in earlier work.Comment: 14 pages, 7 figures. v2: minor emendations. v3: References added, typos fixed, some additions/clarifications. v4: Another reference added, more typos fixed, some more additions/clarifications; v5: Fixed typos in eqs. (2.16), (2.20), (2.23

A statistical analysis of the late-type stellar content in the Andromeda halo

We present a statistical characterization of the carbon-star to M-giant (C/M) ratio in the halo of M31. Based on application of pseudo-filter band passes to our Keck/DEIMOS spectra we measure the 81-77-color index of 1288 stars in the giant stellar stream and in halo fields out to large distances. From this well-established narrow-band system, supplemented by V-I colors, we find only a low number (five in total) of C-star candidates. The resulting low C/M ratio of 10% is consistent with the values in the M31 disk and inner halo from the literature. Although our analysis is challenged by small number statistics and our sample selection, there is an indication that the oxygen-rich M-giants occur in similar number throughout the entire halo. We also find no difference in the C-star population of the halo fields compared to the giant stream. The very low C/M ratio is at odds with the observed low metallicities and the presence of intermediate-age stars at large radii. Our observed absence of a substantial carbon star population in the these regions indicates that the (outer) M31 halo cannot be dominated by the debris of disk-like or SMC-type galaxies, but rather resemble the dwarf elliptical NGC 147.Comment: 11 pages, 10 figures, accepted for publication in the A

Towards Automatic Capturing of Manual Data Processing Provenance

Often data processing is not implemented by a work ow system or an integration application but is performed manually by humans along the lines of a more or less specified procedure. Collecting provenance information during manual data processing can not be automated. Further, manual collection of provenance information is error prone and time consuming. Therefore, we propose to infer provenance information based on the read and write access of users. The derived provenance information is complete, but has a low precision. Therefore, we propose further to introducing organizational guidelines in order to improve the precision of the inferred provenance information

The application of regional-scale geochemical data in defining the extent of aeolian sediments : the Late Pleistocene loess and coversand deposits of East Anglia, UK

The ‘European Coversand Sheet’ is a discontinuous ‘sheet’ of aeolian (windblown) loess and coversand that extends through eastern and southern England, across the English Channel into northern France, Belgium and the Netherlands (Kasse, 1997; Antoine et al., 2003). Whilst some of the earlier aeolian sediments date from the Middle Pleistocene, most correspond to the Late Pleistocene Weichselian / Devensian and earliest Holocene stages. East Anglia contains considerable accumulations of aeolian sediment. Although several valuable studies have attempted to determine the spatial extent of aeolian material (e.g. Catt, 1977, 1985), defining their margins has proved largely difficult because aeolian material is highly susceptible to reworking and removal by various natural and anthropogenic agents. Within this study, we use regional‐scale geochemical data from soils to reconstruct the extent of aeolian sediments in East Anglia. A specific geochemical signature, defined by elevated concentrations of Hafnium (Hf) and Zirconium (Zr), is strongly characteristic of soils developed on aeolian deposits within the United States, China, Europe and New Zealand (Taylor et al., 1983). The data suggests that the approach is sufficiently sensitive to identify a residual aeolian component within soils even where deposits may be thin and unmappable by conventional methods, or if the material has been largely eroded