752 research outputs found
CHANGING ROLES IN IS: A ROLE THEORY PERSPECTIVE
The recent dramatic and interesting advances in computer technology have significantly altered the roles of both users and developers. Role theory might be applied to more fully understand and more effectively investigate organizational, behavioral, and social issues related to these changes. A framework for categorizing information systems roles is built from a matrix of information system and organizational activities. The information system activity dimension is composed of indirect user, direct user, autonomous developer, traditional developer, and facilitator categories. The organizational activity dimension contains clerical, professional, and managerial categories. The resulting matrix can facilitate descriptive research, model building, and hypothesis testing
Electroweak Symmetry Breaking in the DSSM
We study the theoretical and phenomenological consequences of modifying the
Kahler potential of the MSSM two Higgs doublet sector. Such modifications
naturally arise when the Higgs sector mixes with a quasi-hidden conformal
sector, as in some F-theory GUT models. In the Delta-deformed Supersymmetric
Standard Model (DSSM), the Higgs fields are operators with non-trivial scaling
dimension 1 < Delta < 2. The Kahler metric is singular at the origin of field
space due to the presence of quasi-hidden sector states which get their mass
from the Higgs vevs. The presence of these extra states leads to the fact that
even as Delta approaches 1, the DSSM does not reduce to the MSSM. In
particular, the Higgs can naturally be heavier than the W- and Z-bosons.
Perturbative gauge coupling unification, a large top quark Yukawa, and
consistency with precision electroweak can all be maintained for Delta close to
unity. Moreover, such values of Delta can naturally be obtained in
string-motivated constructions. The quasi-hidden sector generically contains
states charged under SU(5)_GUT as well as gauge singlets, leading to a rich,
albeit model-dependent, collider phenomenology.Comment: v3: 40 pages, 3 figures, references added, typos correcte
Toward a descriptive model of solar particles in the heliosphere
During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made
Linear Probability Models of the Demand for Attributes with an Empirical Application to Estimating the Preferences of Legislators
This paper formulates and estimates a rigorously-justified linear probability model of binary choices over alternatives characterized by unobserved attributes. The model is applied to estimate preferences of congressmen as expressed in their votes on bills. The effective dimension of the attribute space characterizing votes is larger than what has been estimated in recent influential studies of congressional voting by Poole and Rosenthal. Congressmen vote on more than ideology. Issue-specific attributes are an important determinant of congressional" voting patterns. The estimated dimension is too large for the median voter model to describe congressional voting
Non-simply-laced Lie algebras via F theory strings
In order to describe the appearance in F theory of the non--simply--laced Lie
algebras, we use the representation of symmetry enhancements by means of string
junctions. After an introduction to the techniques used to describe symmetry
enhancement, that is algebraic geometry, BPS states analysis and string
junctions, we concentrate on the latter. We give an explicit description of the
folding of D_{2n} to B_n of the folding of E_6 to F_4 and that of D_4 to G_2 in
terms of junctions and Jordan strings. We also discuss the case of C_n, but we
are unable in this case to provide a string interpretation.Comment: 24 pages, 3 figure
Multiwavelength star formation indicators: Observations
We present a compilation of multiwavelength data on different star formation
indicators for a sample of nearby star forming galaxies. Here we discuss the
observations, reductions and measurements of ultraviolet images obtained with
STIS, on board the Hubble Space Telescope, ground-based Halpha, and VLA 8.46
GHz radio images. These observations are complemented with infrared fluxes, as
well as large aperture optical radio and ultraviolet data from the literature.
This database will be used in a forthcoming paper to compare star formation
rates at different wavebands. We also present spectral energy distributions
(SEDs) for those galaxies with at least one far-infrared measurements from ISO,
longward of 100 um. These SEDs are divided in two groups, those which are
dominated by the far-infrared emission, and those where the contribution from
the far-infrared and optical emission is comparable. These SEDs are useful
tools to study the properties of high redshift galaxies.Comment: 39 pages, 17 jpeg figures, 1 eps figure, To appear in ApJS May 200
On hypercharge flux and exotics in F-theory GUTs
We study SU(5) Grand Unified Theories within a local framework in F-theory
with multiple extra U(1) symmetries arising from a small monodromy group. The
use of hypercharge flux for doublet-triplet splitting implies massless exotics
in the spectrum that are protected from obtaining a mass by the U(1)
symmetries. We find that lifting the exotics by giving vacuum expectation
values to some GUT singlets spontaneously breaks all the U(1) symmetries which
implies that proton decay operators are induced. If we impose an additional
R-parity symmetry by hand we find all the exotics can be lifted while proton
decay operators are still forbidden. These models can retain the gauge coupling
unification accuracy of the MSSM at 1-loop. For models where the generations
are distributed across multiple curves we also present a motivation for the
quark-lepton mass splittings at the GUT scale based on a Froggatt-Nielsen
approach to flavour.Comment: 38 pages; v2: emphasised possibility of avoiding exotics in models
without a global E8 structure, added ref, journal versio
Quantum W-symmetry in AdS_3
It has recently been argued that, classically, massless higher spin theories
in AdS_3 have an enlarged W_N-symmetry as the algebra of asymptotic isometries.
In this note we provide evidence that this symmetry is realised
(perturbatively) in the quantum theory. We perform a one loop computation of
the fluctuations for a massless spin field around a thermal AdS_3
background. The resulting determinants are evaluated using the heat kernel
techniques of arXiv:0911.5085. The answer factorises holomorphically, and the
contributions from the various spin fields organise themselves into vacuum
characters of the W_N symmetry. For the case of the hs(1,1) theory consisting
of an infinite tower of massless higher spin particles, the resulting answer
can be simply expressed in terms of (two copies of) the MacMahon function.Comment: 23 pages; v2: References adde
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