285 research outputs found
Impacts of climate change on coastal habitats, relevant to the coastal and marine environment around the UK
Coastal habitats are at risk from both direct (temperature, rainfall), and indirect (sea-level rise, coastal erosion) impacts due to a changing climate. Beyond the environmental impacts and ensuing habitat loss, the changing climate will have a significant societal impact to coastal communities ranging from health to livelihoods, as well as the loss of important ecosystem services such as coastal defence – particularly relevant with predicted increase in storminess.
Vegetated coastal ecosystems sequester carbon – another ‘ecosystem service’ that could be disrupted due to climate change. There has been considerable recent attention to the potential role these habitats could play in climate mitigation, and also in transferring carbon across the land–sea interface. To understand the relative importance of these habitats within the global carbon cycle, coastal habitats need to be accounted for in national greenhouse gas inventories, and a true multidisciplinary catchment-to-coast approach to research is required.
Management options exist that can reduce the immediate impacts of climate change, such as managed realignment and sediment recharge. Fixed landward coastal defences are becoming unsustainable and creating ‘coastal squeeze’, highlighting the need to work with natural processes to recreate more-natural shorelines where possible
Alignment of galaxy spins in the vicinity of voids
We provide limits on the alignment of galaxy orientations with the direction
to the void center for galaxies lying near the edges of voids. We locate
spherical voids in volume limited samples of galaxies from the Sloan Digital
Sky Survey using the HB inspired void finder and investigate the orientation of
(color selected) spiral galaxies that are nearly edge-on or face-on. In
contrast with previous literature, we find no statistical evidence for
departure from random orientations. Expressed in terms of the parameter c,
introduced by Lee & Pen to describe the strength of such an alignment, we find
that c<0.11(0.13) at 95% (99.7%) confidence limit within a context of a toy
model that assumes a perfectly spherical voids with sharp boundaries.Comment: 8 pages, 4 figures; v2 discussion expanded, references fixed, matches
version accepted by JCA
Measures for a Transdimensional Multiverse
The multiverse/landscape paradigm that has emerged from eternal inflation and
string theory, describes a large-scale multiverse populated by "pocket
universes" which come in a huge variety of different types, including different
dimensionalities. In order to make predictions in the multiverse, we need a
probability measure. In landscapes, the scale factor cutoff measure
has been previously shown to have a number of attractive properties. Here we
consider possible generalizations of this measure to a transdimensional
multiverse. We find that a straightforward extension of scale factor cutoff to
the transdimensional case gives a measure that strongly disfavors large amounts
of slow-roll inflation and predicts low values for the density parameter
, in conflict with observations. A suitable generalization, which
retains all the good properties of the original measure, is the "volume factor"
cutoff, which regularizes the infinite spacetime volume using cutoff surfaces
of constant volume expansion factor.Comment: 30 pages, 1 figure Minor revisions, reference adde
The universe formation by a space reduction cascade with random initial parameters
In this paper we discuss the creation of our universe using the idea of extra
dimensions. The initial, multidimensional Lagrangian contains only metric
tensor. We have found many sets of the numerical values of the Lagrangian
parameters corresponding to the observed low-energy physics of our universe.
Different initial parameters can lead to the same values of fundamental
constants by the appropriate choice of a dimensional reduction cascade. This
result diminishes the significance of the search for the 'unique' initial
Lagrangian. We also have obtained a large number of low-energy vacua, which is
known as a 'landscape' in the string theory.Comment: 17 pages, 1 figur
A perspective on the landscape problem
I discuss the historical roots of the landscape problem and propose criteria
for its successful resolution. This provides a perspective to evaluate the
possibility to solve it in several of the speculative cosmological scenarios
under study including eternal inflation, cosmological natural selection and
cyclic cosmologies.Comment: Invited contribution for a special issue of Foundations of Physics
titled: Forty Years Of String Theory: Reflecting On the Foundations. 31
pages, no figure
Future research priorities for lichen sclerosus – results of a James Lind Alliance Priority Setting Partnership
Reptiles as food: Predation of Australian reptiles by introduced red foxes compounds and complements predation by cats
Context: Invasive species are a major cause of biodiversity loss across much of the world, and a key threat to Australia’s diverse reptile fauna. There has been no previous comprehensive analysis of the potential impact of the introduced European red fox, Vulpes vulpes, on Australian reptiles.
Aims: We seek to provide an inventory of all Australian reptile species known to be consumed by the fox, and identify characteristics of squamate species associated with such predation. We also compare these tallies and characteristics with reptile species known to be consumed by the domestic cat, Felis catus, to examine whether predation by these two introduced species is compounded (i.e. affecting much the same set of species) or complementary (affecting different groups of species).
Methods: We collated records of Australian reptiles consumed by foxes in Australia, with most records deriving from fox dietary studies (tallying >35 000 samples). We modelled presence or absence of fox predation records against a set of biological and other traits, and population trends, for squamate species.
Key results: In total, 108 reptile species (~11% of Australia’s terrestrial reptile fauna) have been recorded as consumed by foxes, fewer than that reported for cats (263 species). Eighty-six species have been reported to be eaten by both predators. More Australian turtle species have been reported as consumed by foxes than by cats, including many that suffer high levels of predation on egg clutches. Twenty threatened reptile species have been reported as consumed by foxes, and 15 by cats. Squamate species consumed by foxes are more likely to be undergoing population decline than those not known to be consumed by foxes. The likelihood of predation by foxes increased with squamate species’ adult body mass, in contrast to the relationship for predation by cats, which peaked at ~217 g. Foxes, but not cats, were also less likely to consume venomous snakes.
Conclusions: The two introduced, and now widespread, predators have both compounding and complementary impacts on the Australian reptile fauna.
Implications: Enhanced and integrated management of the two introduced predators is likely to provide substantial conservation benefits to much of the Australian reptile fauna
Genome-wide Polygenic Burden of Rare Deleterious Variants in Sudden Unexpected Death in Epilepsy
Peer reviewe
Constraining the dark energy dynamics with the cosmic microwave background bispectrum
We consider the influence of the dark energy dynamics at the onset of cosmic
acceleration on the Cosmic Microwave Background (CMB) bispectrum, through the
weak lensing effect induced by structure formation. We study the line of sight
behavior of the contribution to the bispectrum signal at a given angular
multipole : we show that it is non-zero in a narrow interval centered at a
redshift satisfying the relation , where the
wavenumber corresponds to the scale entering the non-linear phase, and is
the cosmological comoving distance. The relevant redshift interval is in the
range 0.1\lsim z\lsim 2 for multipoles 1000\gsim\ell\gsim 100; the signal
amplitude, reflecting the perturbation dynamics, is a function of the
cosmological expansion rate at those epochs, probing the dark energy equation
of state redshift dependence independently on its present value. We provide a
worked example by considering tracking inverse power law and SUGRA Quintessence
scenarios, having sensibly different redshift dynamics and respecting all the
present observational constraints. For scenarios having the same present
equation of state, we find that the effect described above induces a projection
feature which makes the bispectra shifted by several tens of multipoles, about
10 times more than the corresponding effect on the ordinary CMB angular power
spectrum.Comment: 15 pages, 7 figures, matching version accepted by Physical Review D,
one figure improve
The Mathematical Universe
I explore physics implications of the External Reality Hypothesis (ERH) that
there exists an external physical reality completely independent of us humans.
I argue that with a sufficiently broad definition of mathematics, it implies
the Mathematical Universe Hypothesis (MUH) that our physical world is an
abstract mathematical structure. I discuss various implications of the ERH and
MUH, ranging from standard physics topics like symmetries, irreducible
representations, units, free parameters, randomness and initial conditions to
broader issues like consciousness, parallel universes and Godel incompleteness.
I hypothesize that only computable and decidable (in Godel's sense) structures
exist, which alleviates the cosmological measure problem and help explain why
our physical laws appear so simple. I also comment on the intimate relation
between mathematical structures, computations, simulations and physical
systems.Comment: Replaced to match accepted Found. Phys. version, 31 pages, 5 figs;
more details at http://space.mit.edu/home/tegmark/toe.htm
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