6,306 research outputs found
On symmetries of Chern-Simons and BF topological theories
We describe constructing solutions of the field equations of Chern-Simons and
topological BF theories in terms of deformation theory of locally constant
(flat) bundles. Maps of flat connections into one another (dressing
transformations) are considered. A method of calculating (nonlocal) dressing
symmetries in Chern-Simons and topological BF theories is formulated
String Theory on Dp-plane waves
We study the spectrum of solvable string models on plane waves descending
from non-conformal Dp-brane geometries. We mainly focus on S-dual F1/D1-waves
in type IIB and type I/heterotic 10D superstrings. We derive the Kaluza-Klein
spectrum of N=1,2 10D supergravities on D1/F1-waves. We compute helicity
supertraces counting multiplicities and R-charges of string excitations in the
plane wave geometry. The results are compared against the expectations coming
from gauge/supergravity descriptions. In the type I case, the Klein, Annulus
and Moebius one-loop amplitudes are computed for ten-dimensional D1-waves. We
test the consistency of the open string descendant by showing that after
modular transformations to the closed string channel, the three amplitudes
combine themselves to reconstruct a complete square (|B>+|C>)^2. Tadpole
conditions are also discussed.Comment: 22 pages, Minor corrections, References adde
Gravitational Lorentz Violations from M-Theory
In an attempt to bridge the gap between M-theory and braneworld
phenomenology, we present various gravitational Lorentz-violating braneworlds
which arise from p-brane systems. Lorentz invariance is still preserved locally
on the braneworld. For certain p-brane intersections, the massless graviton is
quasi-localized. This also results from an M5-brane in a C-field. In the case
of a p-brane perturbed from extremality, the quasi-localized graviton is
massive. For a braneworld arising from global AdS_5, gravitons travel faster
when further in the bulk, thereby apparently traversing distances faster than
light.Comment: 13 pages, 1 figure, LaTeX, references added, minor corrections and
addition
Supersymmetry and homogeneity of M-theory backgrounds
We describe the construction of a Lie superalgebra associated to an arbitrary
supersymmetric M-theory background, and discuss some examples. We prove that
for backgrounds with more than 24 supercharges, the bosonic subalgebra acts
locally transitively. In particular, we prove that backgrounds with more than
24 supersymmetries are necessarily (locally) homogeneous.Comment: 19 pages (Erroneous Section 6.3 removed from the paper.
All spacetimes with vanishing curvature invariants
All Lorentzian spacetimes with vanishing invariants constructed from the
Riemann tensor and its covariant derivatives are determined. A subclass of the
Kundt spacetimes results and we display the corresponding metrics in local
coordinates. Some potential applications of these spacetimes are discussed.Comment: 24 page
Hispanic Immigration to the United States
This chapter presents some of the exceptional characteristics of recent Hispanic immigration to the United States. In 2005, there were nearly 40 million Hispanic immigrants and descendants of Hispanic immigrants living in the U.S. The assimilation experience of this large cultural group does not seem to be following the path past immigrants to the U.S. followed. Most third generation Hispanics in the U.S. still find themselves with income and education levels below the U.S. averages. Most forecasts predict that about 60 million Hispanics and Hispanic-Americans will be living in the U.S. by 2030
How can personal development lead to increased engagement? The roles of meaningfulness and perceived line manager relations
There is an increasing need to understand the psychological processes that link personal development with employee engagement, particularly the boundary conditions at which these occur. The current study sought to meet this need by testing whether perceived opportunities for development are positively associated with job engagement indirectly through the experience of meaningfulness, and whether this indirect relationship is conditional on the level of perceived line manager relations. Questionnaire data was collected from 152 UK workers from a range of occupations and organizations. The results found support for all the hypotheses. In particular, the positive effects of perceived opportunities for development on job engagement (measured one month later) via meaningfulness were only significant for those who perceived that they had a good relationship with their line manager. Thus, there is a need for line managers to develop high quality relationships with their direct reports in order for development practices to translate into positive psychological outcomes. Engagement theory could be advanced by further understanding broaden-and-build and social exchange processes
On the symmetries of BF models and their relation with gravity
The perturbative finiteness of various topological models (e.g. BF models)
has its origin in an extra symmetry of the gauge-fixed action, the so-called
vector supersymmetry. Since an invariance of this type also exists for gravity
and since gravity is closely related to certain BF models, vector supersymmetry
should also be useful for tackling various aspects of quantum gravity. With
this motivation and goal in mind, we first extend vector supersymmetry of BF
models to generic manifolds by incorporating it into the BRST symmetry within
the Batalin-Vilkovisky framework. Thereafter, we address the relationship
between gravity and BF models, in particular for three-dimensional space-time.Comment: 29 page
Systematics of M-theory spinorial geometry
We reduce the classification of all supersymmetric backgrounds in eleven
dimensions to the evaluation of the supercovariant derivative and of an
integrability condition, which contains the field equations, on six types of
spinors. We determine the expression of the supercovariant derivative on all
six types of spinors and give in each case the field equations that do not
arise as the integrability conditions of Killing spinor equations. The Killing
spinor equations of a background become a linear system for the fluxes,
geometry and spacetime derivatives of the functions that determine the spinors.
The solution of the linear system expresses the fluxes in terms of the geometry
and specifies the restrictions on the geometry of spacetime for all
supersymmetric backgrounds. We also show that the minimum number of field
equations that is needed for a supersymmetric configuration to be a solution of
eleven-dimensional supergravity can be found by solving a linear system. The
linear systems of the Killing spinor equations and their integrability
conditions are given in both a timelike and a null spinor basis. We illustrate
the construction with examples.Comment: 46 pages. v2: systematics of a null spinor basis is included in
section
A doubled discretisation of abelian Chern-Simons theory
A new discretisation of a doubled, i.e. BF, version of the pure abelian
Chern-Simons theory is presented. It reproduces the continuum expressions for
the topological quantities of interest in the theory, namely the partition
function and correlation function of Wilson loops. Similarities with free
spinor field theory are discussed which are of interest in connection with
lattice fermion doubling.Comment: 5 pages, revtex, 2 ps figures (epsf required). To appear in
Phys.Rev.Let
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