121 research outputs found
Exploring degeneracies in modified gravity with weak lensing
By considering linear-order departures from general relativity, we compute a
novel expression for the weak lensing convergence power spectrum under
alternative theories of gravity. This comprises an integral over a 'kernel' of
general relativistic quantities multiplied by a theory-dependent 'source' term.
The clear separation between theory-independent and -dependent terms allows for
an explicit understanding of each physical effect introduced by altering the
theory of gravity. We take advantage of this to explore the degeneracies
between gravitational parameters in weak lensing observations.Comment: 17 pages, 7 figures. v2: Minor changes to match version accepted by
PR
Testing the nature of gravitational wave propagation using dark sirens and galaxy catalogues
The dark sirens method enables us to use gravitational wave events without
electromagnetic counterparts as tools for cosmology and tests of gravity.
Furthermore, the dark sirens analysis code gwcosmo can now robustly account for
information coming from both galaxy catalogues and the compact object mass
distribution. We present here an extension of the gwcosmo code and methodology
to constrain parameterized deviations from General Relativity that affect the
propagation of gravitational waves. We show results of our analysis using data
from the GWTC-3 gravitational wave catalogues, in preparation for application
to the O4 observing run. After testing our pipelines using the First Two Years
mock data set, we reanalyse 46 events from GWTC-3, and combine the posterior
for BBH and NSBH sampling results for the first time. We obtain joint
constraints on H0 and parameterized deviations from General Relativity in the
Power Law + Peak BBH population model. With increased galaxy catalogue support
in the future, our work sets the stage for dark sirens to become a powerful
tool for testing gravity
Testing gravitational wave propagation with multiband detections
Effective field theories (EFT) of dark energy (DE) -- built to parameterise
the properties of DE in an agnostic manner -- are severely constrained by
measurements of the propagation speed of gravitational waves (GW). However, GW
frequencies probed by ground-based interferometers lie around the typical
strong coupling scale of the EFT, and it is likely that the effective
description breaks down before even reaching that scale. We discuss how this
leaves the possibility that an appropriate ultraviolet completion of DE
scenarios, valid at scales beyond an EFT description, can avoid present
constraints on the GW speed. Instead, additional constraints in the lower
frequency LISA band would be harder to escape, since the energies involved are
orders of magnitude lower. By implementing a method based on GW multiband
detections, we show indeed that a single joint observation of a GW150914-like
event by LISA and a terrestrial interferometer would allow one to constrain the
speed of light and gravitons to match to within . Multiband GW
observations can therefore firmly constrain scenarios based on the EFT of DE,
in a robust and unambiguous way.Comment: 11 pages, 4 figures. Updated to match the version published in JCA
Differences in Nonmedical Use of Prescription Stimulants Among Fraternity- and Sorority-Afiliated Students
The current study reviewed data from the 2022 College Prescription Drug Study of 4,967 undergraduate students to examine differences in lifetime and past-year misuse of prescription stimulants, academic motivations and consequences of misuse, and misperceptions of prescription stimulants. Results indicate that fraternity- and sorority-affiliated students are more likely to report misusing a prescription stimulant in their lifetime and within the past year than nonaffiliated students. Fraternity and sorority members are more influenced by academic reasons and social norms than nonaffiliated students, with gender identity further predicting level of risk. Implications for prevention programming for fraternity and sorority members are discussed
Phi Zeta Delta: Growth of Perturbations in Parameterized Gravity for an Einstein-de Sitter Universe
Parameterized frameworks for modified gravity are potentially useful tools
for model-independent tests of General Relativity on cosmological scales. The
toy model of an Einstein-de Sitter (EdS) universe provides a safe testbed in
which to improve our understanding of their behaviour. We implement a
mathematically consistent parameterization at the level of the field equations,
and use this to calculate the evolution of perturbations in an EdS scenario.
Our parameterization explicitly allows for new scalar degrees of freedom, and
we compare this to theories in which the only degrees of freedom come from the
metric and ordinary matter. The impact on the Integrated Sachs-Wolfe effect and
canonically-conserved superhorizon perturbations is considered.Comment: Updated to match published versio
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