5,131 research outputs found
Constraining Lorentz-violating, Modified Dispersion Relations with Gravitational Waves
Modified gravity theories generically predict a violation of Lorentz
invariance, which may lead to a modified dispersion relation for propagating
modes of gravitational waves. We construct a parametrized dispersion relation
that can reproduce a range of known Lorentz-violating predictions and
investigate their impact on the propagation of gravitational waves. A modified
dispersion relation forces different wavelengths of the gravitational wave
train to travel at slightly different velocities, leading to a modified phase
evolution observed at a gravitational-wave detector. We show how such
corrections map to the waveform observable and to the parametrized
post-Einsteinian framework, proposed to model a range of deviations from
General Relativity. Given a gravitational-wave detection, the lack of evidence
for such corrections could then be used to place a constraint on Lorentz
violation. The constraints we obtain are tightest for dispersion relations that
scale with small power of the graviton's momentum and deteriorate for a steeper
scaling.Comment: 11 pages, 3 figures, 2 tables: title changed slightly, published
versio
Management of Rural Water Services in Nicaragua: A Systematic Network Approach to Evaluating Stakeholder Alignment
Water sector literature attributes a substantial cause of rural water system failure in developing countries to poor alignment between water service stakeholders. This study aimed to investigate a means for assessing stakeholder alignment by comparing the systemic interaction of stakeholder values, where the term ‘stakeholder values’ refers to aspects stakeholders believe are necessary to ensure rural water services are sustainable. The research held focus groups with key stakeholder groups involved in the management of rural water infrastructure in Terrabona, Nicaragua, to identify stakeholder values, and then used cross-impact analysis to evaluate how these values interacted to form stakeholder value networks (SVNs). Using normalized betweenness centrality measures, the structures of SVNs were compared to determine alignment. Results from this study showed high levels of stakeholder alignment on the topics of water resources and technology for the sustainability of rural water systems, while there was marked nonalignment regarding the involvement of local government and organizations in the management of water infrastructure. This study offers compelling evidence for future studies to assess stakeholder alignment by identifying and structurally analyzing SVNs
Figures of merit and constraints from testing General Relativity using the latest cosmological data sets including refined COSMOS 3D weak lensing
We use cosmological constraints from current data sets and a figure of merit
(FoM) approach to probe any deviations from general relativity (GR) at
cosmological scales. The FoM approach is used to study the constraining power
of various combinations of data sets on modified gravity (MG) parameters. We
use recently refined HST-COSMOS weak-lensing tomography data, ISW-galaxy cross
correlations from 2MASS and SDSS LRG surveys, matter power spectrum from
SDSS-DR7 (MPK), WMAP7 temperature and polarization spectra, BAO from 2DF and
SDSS-DR7, and Union2 compilation of supernovae, in addition to other bounds
from H_0 measurements and BBN. We use 3 parametrizations of MG parameters that
enter the perturbed field equations. In order to allow for variations with
redshift and scale, the first 2 parametrizations use recently suggested
functional forms while the third is based on binning methods. Using the first
parametrization, we find that CMB + ISW + WL provides the strongest constraints
on MG parameters followed by CMB+WL or CMB+MPK+ISW. Using the second
parametrization or binning methods, CMB+MPK+ISW consistently provides some of
the strongest constraints. This shows that the constraints are parametrization
dependent. We find that adding up current data sets does not improve
consistently uncertainties on MG parameters due to tensions between best-fit MG
parameters preferred by different data sets. Furthermore, some functional forms
imposed by the parametrizations can lead to an exacerbation of these tensions.
Next, unlike some studies that used the CFHTLS lensing data, we do not find any
deviation from GR using the refined HST-COSMOS data, confirming previous claims
in those studies that their result may have been due to some systematic effect.
Finally, we find in all cases that the values corresponding to GR are within
the 95% confidence level contours for all data set combinations. (abridged)Comment: 18 pages, 6 figures, matches version published in PR
A flexible telerobotic system for space operations
The objective and design of a proposed goal-oriented knowledge-based telerobotic system for space operations is described. This design effort encompasses the elements of the system executive and user interface and the distribution and general structure of the knowledge base, the displays, and the task sequencing. The objective of the design effort is to provide an expandable structure for a telerobotic system that provides cooperative interaction between the human operator and computer control. The initial phase of the implementation provides a rule-based, goal-oriented script generator to interface to the existing control modes of a telerobotic research system, in the Intelligent Systems Research Lab at NASA Research Center
Multimetric extension of the PPN formalism: experimental consistency of repulsive gravity
Recently we discussed a multimetric gravity theory containing several copies
of standard model matter each of which couples to its own metric tensor. This
construction contained dark matter sectors interacting repulsively with the
visible matter sector, and was shown to lead to cosmological late-time
acceleration. In order to test the theory with high-precision experiments
within the solar system we here construct a simple extension of the
parametrized post-Newtonian (PPN) formalism for multimetric gravitational
backgrounds. We show that a simplified version of this extended formalism
allows the computation of a subset of the PPN parameters from the linearized
field equations. Applying the simplified formalism we find that the PPN
parameters of our theory do not agree with the observed values, but we are able
to improve the theory so that it becomes consistent with experiments of
post-Newtonian gravity and still features its promising cosmological
properties.Comment: 19 pages, no figures, journal versio
Weak-field limit of Kaluza-Klein models with spherical compactification: experimental constraints
We investigate the classical gravitational tests for the six-dimensional
Kaluza-Klein model with spherical (of a radius ) compactification of the
internal space. The model contains also a bare multidimensional cosmological
constant . The matter, which corresponds to this ansatz, can be
simulated by a perfect fluid with the vacuum equation of state in the external
space and an arbitrary equation of state with the parameter in the
internal space. For example, and correspond to the
monopole two-forms and the Casimir effect, respectively. In the particular case
, the parameter is also absent: . In the
weak-field approximation, we perturb the background ansatz by a point-like
mass. We demonstrate that in the case the perturbed metric
coefficients have the Yukawa type corrections with respect to the usual
Newtonian gravitational potential. The inverse square law experiments restrict
the parameters of the model: $a/\sqrt{\omega_1}\lesssim 6\times10^{-3}\
{{cm}}\gamma\omega_1>0\omega_1=0\gamma=1/3$,
which strongly contradicts the observations.Comment: 8 pages, no figures, revised version, equations and references added,
accepted for publication in Phys. Rev. D. arXiv admin note: significant text
overlap with arXiv:1107.338
Gravitomagnetism in superconductors and compact stars
There are three experimentally observed effects in rotating superconductors
that are so far unexplained. Some authors have tried to interpret such a
phenomena as possible new gravitational properties of coherent quantum systems:
in particular, they suggest that the gravitomagnetic field of that kind of
matter may be many orders of magnitude stronger than the one expected in the
standard theory. Here I show that this interpretation would be in conflict with
the common belief that neutron stars have neutrons in superfluid state and
protons in superconductive one.Comment: 9 pages, no figur
Cut Purses and Poisoned Paintings: Resisting Gender Objectification
The early modern English stage often portrays gender as polarized, creating an unwelcoming atmosphere toward characters who act exhibit characteristics from both male and female genders. Moll Cutpurse from Thomas Dekker and Thomas Middleton’s The Roaring Girl and Alice of Arden of Faversham resist early modern gender boundaries, conflating masculine and feminine attributes as they use objects to navigate their respective social spaces. Critics often describe Moll as a transvestite due to her fashion choice to wear a codpiece, along with her exaggerated, boisterous masculine behavior; however, she consistently defends her biological sex, implicating herself within her arguments concerning female chastity. As she duels with a sword for the honor of women, Moll inhabits a masculine persona. Alice, on the other hand, is often considered solely feminine, yet she exhibits early modern masculine characteristics when she acts within her commodity-driven surroundings to plot her husband’s murder by using poisoned objects and coins. By using objects to exert masculinity, Moll and Alice reveal the early modern concern of women’s abilities to adopt masculine qualities. The male responses within these plays show attempts to contain these women, as both are branded as criminals. Both women act against the law: Moll is a cutpurse, and Alice is an adulteress and, by the conclusion of the play, a murderess. Thus, The Roaring Girl and Arden of Faversham reveal the existence of female characters who defy the gender binary by using objects to adopt masculine characteristics. As they resist polarity, however, Moll and Alice must also exist within the realm of criminality
Screeches from the Red Hen: Public Accommodations Laws and Political Affiliation Discrimination in the United States and Louisiana
The article discusses issues on public accommodations laws and political affiliation discrimination in the U.S. and Louisiana, as well as the provisions of the Louisiana Constitution and the U.S. Constitution on public accommodation
- …