108 research outputs found
Searching for Primordial Black Holes with the Einstein Telescope: impact of design and systematics
Primordial Black Holes (PBHs) have recently attracted much attention as they
may explain some of the LIGO/Virgo/KAGRA observations and significantly
contribute to the dark matter in our universe. The next generation of
Gravitational Wave (GW) detectors will have the unique opportunity to set
stringent bounds on this putative population of objects. Focusing on the
Einstein Telescope (ET), in this paper we analyse in detail the impact of
systematics and different detector designs on our future capability of
observing key quantities that would allow us to discover and/or constrain a
population of PBH mergers. We also perform a population analysis, with a mass
and redshift distribution compatible with the current observational bounds. Our
results indicate that ET alone can reach an exquisite level of accuracy on the
key observables considered, as well as detect up to tens of thousands of PBH
binaries per year, but for some key signatures (in particular high--redshift
sources) the cryogenic instrument optimised for low frequencies turns out to be
crucial, both for the number of observations and the error on the parameters
reconstruction. As far as the detector geometry is concerned, we find that a
network consisting of two separated L--shaped interferometers of 15 (20)~km arm
length, oriented at with respect to each other performs better
than a single triangular shaped instrument of 10 (15)~km arm length, for all
the metrics considered.Comment: 24 pages, 13 figure
Genetically induced dysfunctions of Kir2.1 channels: implications for short QT3 syndrome and autism-epilepsy phenotype.
Cosmology with the Laser Interferometer Space Antenna
The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational wave observations by LISA to probe the universe
Mechanisms for primordial black hole production in string theory
We consider mechanisms for producing a significant population of primordial black holes (PBHs) within string inspired single field models of inflation. The production of PBHs requires a large amplification in the power spectrum of curvature perturbations between scales associated with CMB and PBH formation. In principle, this can be achieved by temporarily breaking the slow-roll conditions during inflation. In this work, we identify two string setups that can realise this process. In string axion models of inflation, subleading non-perturbative effects can superimpose steep cliffs and gentle plateaus onto the leading axion potential. The cliffs can momentarily violate the slow-roll conditions, and the plateaus can lead to phases of ultra slow-roll inflation. We thus achieve a string motivated model which both matches the Planck observations at CMB scales and produces a population of light PBHs, which can account for an order one fraction of dark matter. In DBI models of inflation, a sharp increase in the speed of sound sourced by a steep downward step in the warp factor can drive the amplification. In this scenario, discovery of PBHs could indicate non-trivial dynamics in the bulk, such as flux-antibrane annihilation at the tip of a warped throat
Identification of an Anion Channel Protein from Transverse Tubules of Rabbit Skeletal Muscle
OpenMP Parallelization Strategies for a Discontinuous Galerkin Solver
This paper aims to report on the open multi-processing (OpenMP) parallel implementation of a fully unstructured high-order discontinuous Galerkin (DG) solver for computational fluid dynamics and computational aeroacoustics applications. Even if the use of OpenMP paradigm is confined to shared memory systems, it has some advantages over the use of the message passing interface (MPI) library, and getting the best of this approach potentially improves the parallel efficiency of codes running on clusters of multi-core nodes. While with MPI the use of a domain decomposition algorithm is almost unavoidable, the OpenMP shared memory context offers several opportunities. Three strategies, here optimised for a DG solver, are presented and compared: the first refers to a customization of a colouring approach, the second mimics an MPI implementation in the OpenMP context, while the third method is somehow half way between the previous two. The numerical tests performed on both inviscid and viscous test cases indicate that, thanks to the compactness of the DG discretization, all the code versions perform quite satisfactory. In particular, the domain decomposition algorithm reaches the highest level of parallel efficiency at low computational loads while the colouring approach excels at larger computational loads and it can be easily implemented within an existing MPI code. Moreover, colouring is very well suited to deal with hardware accelerators, an opportunity given by the OpenMP 4.0 standard. Finally, the performance gain observed in using a hybrid MPI/OpenMP version of the DG code on high performance computing facilities is demonstrated
Implications of the detection of primordial gravitational waves for the Standard Model
The detection of primordial gravitational waves would not only have extraordinary implications for our understanding of early cosmology, but would also give non-trivial constraints on Standard Model parameters, under the assumption that no new physics enters below the Higgs instability scale. We study the resulting bounds on the top quark mass and the strong coupling constant, discussing their theoretical uncertainties and their robustness against changes in other parameters
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