An Exceptional Sector for F-theory GUTs

D3-branes are often a necessary ingredient in global compactifications of F-theory. In minimal realizations of flavor hierarchies in F-theory GUT models, suitable fluxes are turned on, which in turn attract D3-branes to the Yukawa points. Of particular importance are ``E-type'' Yukawa points, as they are required to realize a large top quark mass. In this paper we study the worldvolume theory of a D3-brane probing such an E-point. D3-brane probes of isolated exceptional singularities lead to strongly coupled N = 2 CFTs of the type found by Minahan and Nemeschansky. We show that the local data of an E-point probe theory determines an N = 1 deformation of the original N = 2 theory which couples this strongly interacting CFT to a free hypermultiplet. Monodromy in the seven-brane configuration translates to a novel class of deformations of the CFT. We study how the probe theory couples to the Standard Model, determining the most relevant F-term couplings, the effect of the probe on the running of the Standard Model gauge couplings, as well as possible sources of kinetic mixing with the Standard Model.Comment: v2: 32 pages, 1 figure, references added, appendix remove

Grand Unified Yukawa Matrix Ansatz: The Standard Model Fermion Mass, Quark Mixing and CP Violation Parameters

We propose a new mass matrix ansatz: At the grand unified (GU) scale, the standard model (SM) Yukawa coupling matrix elements are integer powers of the square root of the GU gauge coupling constant \varepsilon \equiv \sqrt{\alpha_{\text{GU}}}, multiplied by order unity random complex numbers. It relates the hierarchy of the SM ermion masses and quark mixings to the gauge coupling constants, greatly reducing the SM parameters, and can give good fitting results of the SM fermion mass, quark mixing and CP violation parameters. This is a neat but very effective ansatz.Comment: 4 pages (two columns), by REVTeX 4, 2 tables, no figures, version for publication in CP

Determining the Impact of Federal Antidiscrimination Policy on the Economic Status of Blacks: A Study of South Carolina

This paper assesses the contribution of federal antidiscrimination policy to the dramatic improvement of black economic status in manufacturing that occurred in South Carolina in the mid 1960's. Using a unique data source on wages and employment by race and sex in South Carolina we evaluate competing explanations. Human capital stories, supply shift stories and tight labor market stories do not account for the black breakthrough. Our study documents a significant contribution of federal antidiscrimination programs.

Local Starbursts in a Cosmological Context

In this contribution I introduce some of the major issues that motivate the conference, with an emphasis on how starbursts fit into the ``big picture''. I begin by defining starbursts in several different ways, and discuss the merits and limitations of these definitions. I will argue that the most physically useful definition of a starburst is its ``intensity'' (star formation rate per unit area). This is the most natural parameter to compare local starbursts with physically similar galaxies at high redshift, and indeed I will argue that local starbursts are unique laboratories to study the processes at work in the early universe. I will describe how NASA's GALEX mission has uncovered a rare population of close analogs to Lyman Break Galaxies in the local universe. I will then compare local starbursts to the Lyman-Break and sub-mm galaxies high redshift populations, and speculate that the multidimensional ``manifold'' of starbursts near and far can be understood largely in terms of the Schmidt/Kennicutt law and galaxy mass-metallicity relation. I will briefly summarize he properties of starburst-driven galactic superwinds and their possible implications for the evolution of galaxies and the IGM. These complex multiphase flows are best studied in nearby starbursts, where we can study the the hot X-ray gas that contains the bulk of the energy and newly produced metals.Comment: Proceedings of the Conference "Starbursts: Fropm 30 Doradus to Lyman Break Galaxies

A New Concept of Transonic Galactic Outflows in a Cold Dark Matter Halo with a Central Super-Massive Black Hole

We study fundamental properties of isothermal, steady and spherically symmetric galactic outflow in the gravitational potential of a cold dark matter halo and a central super-massive black hole. We find that there are two transonic solutions having different properties: each solution is mainly produced by the dark matter halo and the super-massive black hole, respectively. Furthermore, we apply our model to the Sombrero galaxy. In this galaxy, Chandra X-ray observatory detected the diffuse hot gas as the trace of galactic outflows while the star-formation rate is low and the observed gas density distribution presumably indicates the hydrostatic equilibrium. To solve this discrepancy, we propose a solution that this galaxy has a transonic outflow, however, the transonic point forms in a very distant region from the galactic center (?$\sim$ 127 kpc). In this slowly accelerated transonic outflow, the outflow velocity is less than the sound velocity for most of the galactic halo. Since the gas density distribution in this subsonic region is similar to the hydrostatic one, it is difficult to distinguish the wide subsonic region from hydrostatic state. Such galactic outflows are dfferent from the conventional supersonic outflows observed in star-forming galaxies.Comment: 7 pages, 3 figures, accepted for publication in JPS Conference Proceedings. arXiv admin note: substantial text overlap with arXiv:1405.345

On the Defect Group of a 6D SCFT

We use the F-theory realization of 6D superconformal field theories (SCFTs) to study the corresponding spectrum of stringlike, i.e. surface defects. On the tensor branch, all of the stringlike excitations pick up a finite tension, and there is a corresponding lattice of string charges, as well as a dual lattice of charges for the surface defects. The defect group is data intrinsic to the SCFT and measures the surface defect charges which are not screened by dynamical strings. When non-trivial, it indicates that the associated theory has a partition vector rather than a partition function. We compute the defect group for all known 6D SCFTs, and find that it is just the abelianization of the discrete subgroup of U(2) which appears in the classification of 6D SCFTs realized in F-theory. We also explain how the defect group specifies defining data in the compactification of a (1,0) SCFT.Comment: 24 page

The GED

The General Educational Development (GED) credential is issued on the basis of an eight hour subject-based test. The test claims to establish equivalence between dropouts and traditional high school graduates, opening the door to college and positions in the labor market. In 2008 alone, almost 500,000 dropouts passed the test, amounting to 12% of all high school credentials issued in that year. This chapter reviews the academic literature on the GED, which finds minimal value of the certificate in terms of labor market outcomes and that only a few individuals successfully use it as a path to obtain post-secondary credentials. Although the GED establishes cognitive equivalence on one measure of scholastic aptitude, recipients still face limited opportunity due to deficits in noncognitive skills such as persistence, motivation and reliability. The literature finds that the GED testing program distorts social statistics on high school completion rates, minority graduation gaps, and sources of wage growth. Recent work demonstrates that, through its availability and low cost, the GED also induces some students to drop out of school. The GED program is unique to the United States and Canada, but provides policy insight relevant to any nation's educational context.returns to education, GED, dropouts, graduation rate, noncognitive skills

The Discovery of an Active Galactic Nucleus in the Late-type Galaxy NGC 3621: Spitzer Spectroscopic Observations

We report the discovery of an Active Galactic Nucleus (AGN) in the nearby SAd galaxy NGC 3621 using Spitzer high spectral resolution observations. These observations reveal the presence of [NeV] 14 um and 24 um emission which is centrally concentrated and peaks at the position of the near-infrared nucleus. Using the [NeV] line luminosity, we estimate that the nuclear bolometric luminosity of the AGN is ~ 5 X 10^41 ergs s^-1, which corresponds based on the Eddington limit to a lower mass limit of the black hole of ~ 4 X 10^3 Msun. Using an order of magnitude estimate for the bulge mass based on the Hubble type of the galaxy, we find that this lower mass limit does not put a strain on the well-known relationship between the black hole mass and the host galaxy's stellar velocity dispersion established in predominantly early-type galaxies. Mutli-wavelength follow-up observations of NGC 3621 are required to obtain more precise estimates of the bulge mass, black hole mass, accretion rate, and nuclear bolometric luminosity. The discovery reported here adds to the growing evidence that a black hole can form and grow in a galaxy with no or minimal bulge.Comment: 5 pages, 7 figures, Accepted for publication in ApJ Letter

The Spatial Clustering of Low Luminosity AGN

We present the first multi-parameter analysis of the narrow line AGN clustering properties. Estimates of the two-point correlation function (CF) based on SDSS DR2 data reveal that Seyferts are clearly less clustered than normal galaxies, while the clustering amplitude (r_0) of LINERs is consistent with that of the parent galaxy population. The similarities in the host properties (color and concentration index) of Seyferts and LINERs suggest that the difference in their r_0 is not driven by the morphology-density relation. We find that the luminosity of [O I] emission shows the strongest influence on AGN clustering, with low L([O I]) sources having the highest r_0. This trend is much stronger than the previously detected dependence on L([O III]), which we confirm. There is a strong correspondence between the clustering patterns of objects of given spectral type and their physical properties. LINERs, which exhibit high r_0, show the lowest luminosities and obscuration levels, and relatively low gas densities (n_e), suggesting that these objects harbor black holes that are relatively massive yet weakly active or inefficient in their accretion, probably due to the insufficiency of their fuel supply. Seyferts, which have low r_0, are luminous and show large n_e, suggesting that their black holes are less massive but accrete quickly and efficiently enough to clearly dominate the ionization. The low r_0 of the H II galaxies can be understood as a consequence of both the morphology-density and star formation rate-density relations, however, their spectral properties suggest that their centers hide amidst large amounts of obscuring material black holes of generally low mass whose activity remains relatively feeble. Our own Milky Way may be a typical such case.[abridged]Comment: 27 pages, color figures, some are severely degraded in resolution, emulateapj. See http://www.physics.drexel.edu/~constant/work/agnclustering.ps for high resolution version. Accepted to Ap

T-Branes and Monodromy

We introduce T-branes, or "triangular branes," which are novel non-abelian bound states of branes characterized by the condition that on some loci, their matrix of normal deformations, or Higgs field, is upper triangular. These configurations refine the notion of monodromic branes which have recently played a key role in F-theory phenomenology. We show how localized matter living on complex codimension one subspaces emerge, and explain how to compute their Yukawa couplings, which are localized in complex codimension two. Not only do T-branes clarify what is meant by brane monodromy, they also open up a vast array of new possibilities both for phenomenological constructions and for purely theoretical applications. We show that for a general T-brane, the eigenvalues of the Higgs field can fail to capture the spectrum of localized modes. In particular, this provides a method for evading some constraints on F-theory GUTs which have assumed that the spectral equation for the Higgs field completely determines a local model.Comment: 110 pages, 5 figure