119349007
Gauge five-brane moduli in four-dimensional heterotic models
We present a Kaehler potential for four-dimensional heterotic M-theory which includes moduli describing a gauge five-brane living on one of the orbifold fixed planes. This result can also be thought of as describing compactifications of either of the weakly coupled heterotic strings in the presence of a gauge five-brane. This is the first example of a Kaehler potential in these theories which includes moduli describing background gauge field configurations. Our results are valid when the solitons width is much smaller than the size scale of the Calabi-Yau threefold and can be used to provide a more complete description of some moving brane scenarios. We point out that, in general, it is not consistent to truncate away the gauge five-brane moduli in a simple manner.
59154275
Two hundred heterotic standard models on smooth Calabi-Yau threefolds
We construct heterotic standard models by compactifying on smooth Calabi-Yau three-folds in the presence of purely Abelian internal gauge fields. A systematic search over complete intersection Calabi-Yau manifolds with less than six Kahler parameters leads to over 200 such models which we present. Each of these models has precisely the matter spectrum of the MSSM, at least one pair of Higgs doublets, the standard model gauge group and no exotics. For about 100 of these models there are, naively, four additional U(1) symmetries, however these are Green-Schwarz anomalous and, hence, massive. In the remaining cases, three U(1) symmetries are anomalous while the fourth, massless one can be spontaneously broken by singlet vacuum expectation values. The presence of additional global U(1) symmetries, together with the possibility of switching on singlet vacuum expectation values, leads to a rich phenomenology which is illustrated for a particular example. Our database of standard models, which can be further enlarged by simply extending the computer-based search, allows for a detailed and systematic phenomenological analysis of string standard models, covering issues such as the structure of Yukawa couplings, R-parity violation, proton stability and neutrino masses.
119732431
All complete intersection Calabi-Yau four-folds
A bstractWe present an exhaustive, constructive, classification of the Calabi-Yau four-folds which can be described as complete intersections in products of projective spaces. A comprehensive list of 921,497 configuration matrices which represent all topologically distinct types of complete intersection Calabi-Yau four-folds is provided and can be downloaded here. The manifolds have non-negative Euler characteristics in the range 0 ≤ χ ≤ 2610. This data set will be of use in a wide range of physical and mathematical applications. Nearly all of these four-folds are elliptically fibered and are thus of interest for F-theory model building.
53536848
Topological invariants and fibration structure of complete intersection Calabi-Yau four-folds
A bstractWe investigate the mathematical properties of the class of Calabi-Yau four-folds recently found in ref. [1]. This class consists of 921,497 configuration matrices which correspond to manifolds that are described as complete intersections in products of projective spaces. For each manifold in the list, we compute the full Hodge diamond as well as additional topological invariants such as Chern classes and intersection numbers. Using this data, we conclude that there are at least 36,779 topologically distinct manifolds in our list. We also study the fibration structure of these manifolds and find that 99.95 percent can be described as elliptic fibrations. In total, we find 50,114,908 elliptic fibrations, demonstrating the multitude of ways in which many manifolds are fibered. A sub-class of 26,088,498 fibrations satisfy necessary conditions for admitting sections. The complete data set can be downloaded here.
119425527
Moving five-branes in low-energy heterotic M theory
We construct cosmological solutions of four-dimensional effective heterotic M-theory with a moving five-brane and evolving dilaton and T modulus. It is shown that the five-brane generates a transition between two asymptotic rolling-radii solutions. Moreover, the five-brane motion always drives the solutions towards strong coupling asymptotically. We present an explicit example of a negative-time branch solution which ends in a brane collision accompanied by a small-instanton transition. The five-dimensional origin of some of our solutions is also discussed.
55683300
Heterotic standard models from smooth Calabi-Yau three-folds
Lara B. Anderson1, James Gray2, Andre Lukas∗3, Eran Palti4 1Center for the Fundamental Laws of Nature, Jefferson Laboratory Harvard University, 17 Oxford Street, Cambridge, MA 02138, U.S.A. 2Arnold-Sommerfeld-Center for Theoretical Physics, Department fur Physik Ludwig-Maximilians-Universitat Munchen, Theresienstrase 37, 80333 Munchen, Germany. 3Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, U.K. 4Centre de Physique Theorique, Ecole Polytechnique, CNRS, 91128 Palaiseau, France.
3264527
Designing and mining multi-terabyte astronomy archives: the Sloan Digital Sky Survey
The next-generation astronomy digital archives will cover most of the sky at fine resolution in many wavelengths, from X-rays, through ultraviolet, optical, and infrared. The archives will be stored at diverse geographical locations. One of the first of these projects, the Sloan Digital Sky Survey (SDSS) is creating a 5-wavelength catalog over 10,000 square degrees of the sky (see http://www.sdss.org/). The 200 million objects in the multi-terabyte database will have mostly numerical attributes in a 100+ dimensional space. Points in this space have highly correlated distributions.
The archive will enable astronomers to explore the data interactively. Data access will be aided by multidimensional spatial and attribute indices. The data will be partitioned in many ways. Small tag objects consisting of the most popular attributes will accelerate frequent searches. Splitting the data among multiple servers will allow parallel, scalable I/O and parallel data analysis. Hashing techniques will allow efficient clustering, and pair-wise comparison algorithms that should parallelize nicely. Randomly sampled subsets will allow de-bugging otherwise large queries at the desktop. Central servers will operate a data pump to support sweep searches touching most of the data. The anticipated queries will require special operators related to angular distances and complex similarity tests of object properties, like shapes, colors, velocity vectors, or temporal behaviors. These issues pose interesting data management challenges.
9954967
Petabyte Scale Data Mining: Dream or Reality?
Science is becoming very data intensive. Today's astronomy datasets with tens of millions of galaxies already present substantial challenges for data mining. In less than 10 years the catalogs are expected to grow to billions of objects, and image archives will reach Petabytes. Imagine having a 100GB database in 1996, when disk scanning speeds were 30MB/s, and database tools were immature. Such a task today is trivial, almost manageable with a laptop. We think that the issue of a PB database will be very similar in six years. In this paper we scale our current experiments in data archiving and analysis on the Sloan Digital Sky Survey data six years into the future. We analyze these projections and look at the requirements of performing data mining on such data sets. We conclude that the task scales rather well: we could do the job today, although it would be expensive. There do not seem to be any show-stoppers that would prevent us from storing and using a Petabyte dataset six years from today.
19318578
Extending the SDSS Batch Query System to the National Virtual Observatory Grid
The Sloan Digital Sky Survey science database is approaching 2TB. While the vast majority of queries normally execute in seconds or minutes, this interactive execution time can be disproportionately increased by a small fraction of queries that take hours or days to run; either because they require non-index scans of the largest tables or because they request very large result sets. In response to this, we added a multi-queue job submission and tracking system. The transfer of very large result sets from queries over the network is another serious problem. Statistics suggested that much of this data transfer is unnecessary; users would prefer to store results locally in order to allow further cross matching and filtering. To allow local analysis, we implemented a system that gives users their own personal database (MyDB) at the portal site. Users may transfer data to their MyDB, and then perform further analysis before extracting it to their own machine. 
We intend to extend the MyDB and asynchronous query ideas to multiple NVO nodes. This implies development, in a distributed manner, of several features, which have been demonstrated for a single node in the SDSS Batch Query System (CasJobs). The generalization of asynchronous queries necessitates some form of MyDB storage as well as workflow tracking services on each node and coordination strategies among nodes.
9414220
Spatial Clustering of Galaxies in Large Datasets
Datasets with tens of millions of galaxies present new challenges for the analysis of spatial clustering. We have built a framework, that integrates a database of object catalogs, tools for creating masks of bad regions, and a fast (NlogN) correlation code. This system has enabled unprecedented efficiency in carrying out the analysis of galaxy clustering in the SDSS catalog. A similar approach is used to compute the three-dimensional spatial clustering of galaxies on very large scales. We describe our strategy to estimate the effect of photometric errors using a database. We discuss our efforts as an early example of data-intensive science. While it would have been possible to get these results without the framework we describe, it will be infeasible to perform these computations on the future huge datasets without using this framework.
55531346
REDESIGN OF THE ISIS MAIN MAGNET POWER SUPPLY STORAGE CHOKE
The ISIS facility, based at the Rutherford Appleton Laboratory in the UK, provides intense pulsed neutron and muon beams for condensed matter studies. As part of the facilities upgrade and refurbishment program, the 1MJ storage choke which forms part of the main magnet power supply system, will be replaced with a number of smaller units. The present storage choke, which consists of a split secondary winding transformer, is incorporated into a series-parallel resonant circuit known as the 'White circuit' [1]. This circuit ensures that each magnet receives identical currents, but is not subjected to excessive voltages. Although the storage choke is essentially a transformer, its secondary magnetising inductance is relatively low and a precisely defined value. This paper discusses the design and development of ten smaller units which will eventually replace the present equipment, and the testing of a one fifth scale model, which will be used to prove the technology.