16659387
Stability walls in heterotic theories
We study the sub-structure of the heterotic Kahler moduli space due to the presence of non-Abelian internal gauge fields from the perspective of the four-dimensional effective theory. Internal gauge fields can be supersymmetric in some regions of the Kahler moduli space but break supersymmetry in others. In the context of the four-dimensional theory, we investigate what happens when the Kahler moduli are changed from the supersymmetric to the non-supersymmetric region. Our results provide a low-energy description of supersymmetry breaking by internal gauge fields as well as a physical picture for the mathematical notion of bundle stability. Specifically, we find that at the transition between the two regions an additional anomalous U(1) symmetry appears under which some of the states in the low-energy theory acquire charges. We compute the associated D-term contribution to the four-dimensional potential which contains a Kahler-moduli dependent Fayet-Iliopoulos term and contributions from the charged states. We show that this D-term correctly reproduces the expected physics. Several mathematical conclusions concerning vector bundle stability are drawn from our arguments. We also discuss possible physical applications of our results to heterotic model building and moduli stabilisation.
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.
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.
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.
33676970
Gauge five-brane dynamics and small instanton transitions in heterotic models
We present the first examples of cosmological solutions to four-dimensional heterotic models which include an evolving bundle modulus. The particular bundle modulus we consider corresponds to the width of a gauge five brane. As such our solutions can be used to describe the evolution in one of these models after a small instanton transition. We find that certain properties are generic to these solutions, regardless of initial conditions. This enables us to make some definite statements about the dynamics subsequent to a small instanton transition despite the fact that we cannot microscopically describe the process itself. We also show that an effective description of the small instanton transition by a continuous matching of fields and their first derivatives is precluded by the form of the respective low-energy theories before and after the transition.
17764338
Yukawa Couplings in Heterotic Compactification
We present a practical, algebraic method for efficiently calculating the Yukawa couplings of a large class of heterotic compactifications on Calabi-Yau three-folds with non-standard embeddings. Our methodology covers all of, though is not restricted to, the recently classified positive monads over favourable complete intersection Calabi-Yau three-folds. Since the algorithm is based on manipulating polynomials it can be easily implemented on a computer. This makes the automated investigation of Yukawa couplings for large classes of smooth heterotic compactifications a viable possibility.
119413711
The sloan digital sky survey quasar catalog. II. First data release
We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than Mi = -22 (in a cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), have at least one emission line with FWHM larger than 1000 km s-1, and have highly reliable redshifts. The area covered by the catalog is ≈1360 deg2. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.43. For each object, the catalog presents positions accurate to better than 02 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains some radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. Calibrated digital spectra of all objects in the catalog, covering the wavelength region 3800–9200 A at a spectral resolution of 1800–2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summary of corrections to current quasar databases is also provided. The majority of the objects were found in SDSS commissioning data using a multicolor selection technique. Since the quasar selection algorithm was undergoing testing during the entire observational period covered by this catalog, care must be taken when assembling samples from the catalog for use in statistical studies. A total of 15,786 objects (94%) in the catalog were discovered by the SDSS; 12,173 of the SDSS discoveries are reported here for the first time. Included in the new discoveries are five quasars brighter than i = 16.0 and 17 quasars with redshifts larger than 4.5.
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.
10760123
Static VAr power factor correction for the ISIS main magnet power supply
ISIS sited at the Rutherford Appleton Laboratory (RAL) is the worlds brightest pulsed neutron source. Intense pulses of neutrons are produced at 50 Hz when a heavy metal target is bombarded with a beam of high energy (800MeV) protons. Energy is imparted to the protons by accelerating them in a synchrotron, the magnets of which are connected in a configuration known as a "white circuit". This white circuit suffers from problems arising from drifting values of capacitance and inductance which affect the resonant frequency. This paper provides a review of Static VAr technology, and focuses on the design and simulation of the implementation of this technology to regulate the resonant frequency of the white circuit.
12139365
TeraScale SneakerNet: Using Inexpensive Disks for Backup, Archiving, and Data Exchange
Large datasets are most economically trnsmitted via parcel post given the current economics of wide-area networking. This article describes how the Sloan Digital Sky Survey ships terabyte scale datasets both within the US and to Europe and Asia. We 3GT storage bricks (Ghz processor, GB ram, GbpsEthernet, TB disk) for about 2k$ each. These bricks act as database servers on the LAN. They are loaded at one site and read at the second site. The paper describes the bricks, their economics, and some software issues that they raise.
55346862
The Sloan Digital Sky Survey Quasar Survey: Quasar Luminosity Function from Data Release 3
We determine the number counts and z = 0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg2 of imaging data from SDSS Data Release 3. The sample extends from i = 15 to 19.1 at z 3 and to i = 20.2 for z 3. The number counts and luminosity function agree well with the results of the Two Degree Field QSO Redshift Survey (2QZ) at redshifts and luminosities at which the SDSS and 2QZ quasar samples overlap, but the SDSS data probe to much higher redshifts than does the 2QZ sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best-fit model has a flatter bright-end slope at high redshift than at low redshift. For z < 2.4 the data are best fit by a redshift-independent slope of ? = -3.1 [?(L) ? L?]. Above z = 2.4 the slope flattens with redshift to ? -2.37 at z = 5. This slope change, which is significant at the 5 ? level, must be accounted for in models of the evolution of accretion onto supermassive black holes.