1,841 research outputs found
Forecasts for Low Spin Black Hole Spectroscopy in Horndeski Gravity
We investigate the prospect of using black hole spectroscopy to constrain the
parameters of Horndeski gravity through observations of gravitational waves
from perturbed black holes. We study the gravitational waves emitted during
ringdown from black holes without hair in Horndeski gravity, demonstrating the
qualitative differences between such emission in General Relativity and
Horndeski theory. In particular, Quasi-Normal Mode frequencies associated with
the scalar field spectrum can appear in the emitted gravitational radiation.
Analytic expressions for error estimates for both the black hole and Horndeski
parameters are calculated using a Fisher Matrix approach, with constraints on
the `effective mass' of the Horndeski scalar field of order eV or tighter being shown to be achievable in some scenarios.
Estimates for the minimum signal-noise-ratio required to observe such a signal
are also presented.Comment: Updated to match published versio
Final Report: Talking about sex and relationships: The views of young people with learning disabilities
We ran a drama group with
young people with learning
disabilities.
We also interviewed parents
of young people with
learning disabilities.
We also talked to groups of
teachers.
There has not been much
research done about this
before
A covariant approach to parameterised cosmological perturbations
We present a covariant formulation for constructing general quadratic actions
for cosmological perturbations, invariant under a given set of gauge symmetries
for a given field content. This approach allows us to analyse scalar, vector
and tensor perturbations at the same time in a straightforward manner. We apply
the procedure to diffeomorphism invariant single-tensor, scalar-tensor and
vector-tensor theories and show explicitly the full covariant form of the
quadratic actions in such cases, in addition to the actions determining the
evolution of vector and tensor perturbations. We also discuss the role of the
symmetry of the background in identifying the set of cosmologically relevant
free parameters describing these classes of theories, including calculating the
relevant free parameters for an axisymmetric Bianchi-I vacuum universe.Comment: Updated to match published versio
Reptile thermogenesis and the origins of endothermy
Extant endotherms have high rates of metabolism, elevated body temperatures, usually tight control over body temperature, and a reasonable scope for further increases in metabolism through locomotor activity. Vertebrate ectotherms, on the other hand, rely on behavioural thermoregulation and cardiovascular adjustments to facilitate warming, and generally lack specific biochemical and cellular mechanisms for sustained, elevated metabolism. Nevertheless, the ancestral condition to endothermy is thought to resemble that of many extant reptiles, which raises the question of the origins and selection pressures relevant to the transitional state. Numerous hypotheses have emerged to explain the multiple origins of endothermy in vertebrates, including thermoregulatory, locomotory, and reproductive activity as possible drivers for these sustained and elevated metabolic rates. In this article, I discuss recent evidence for facultative endothermy in an extant lepidosaur, the tegu lizard. Since lepidosaurs are a sister group to the archosaurs, understanding how a novel form of endothermy evolved will open up opportunities to test the compatibility or incompatibility of the various endothermy hypotheses, with potential to elucidate and resolve long contentious ideas in evolutionary physiology
Kerr-(Anti-)de Sitter Black Holes: Perturbations and quasi-normal modes in the slow rotation limit
We study the perturbations of scalar, vector, and tensor fields in a slowly
rotating Kerr-(Anti-)de Sitter black hole spacetime, presenting new and
existing Schr\"odinger style master equations for each type of perturbation up
to linear order in black hole spin . For each type of field we calculate
analytical expressions for the fundamental quasi-normal mode frequencies. These
frequencies are compared to existing results for Schwarzschild-de Sitter,
slowly rotating Kerr, and slowly rotating Kerr-de Sitter black holes. In all
cases good agreement is found between the analytic expressions and those
frequencies calculated numerically. In addition, the axial and polar
gravitational frequencies are shown to be isospectral to linear order in
for all cases other than for both non-zero and .Comment: Updated to match published versio
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