63 research outputs found
Do the cosmological observational data prefer phantom dark energy?
The dynamics of expansion and large scale structure formation of the Universe
are analyzed for models with dark energy in the form of a phantom scalar field
which initially mimics a -term and evolves slowly to the Big Rip
singularity. The discussed model of dark energy has three parameters -- the
density and the equation of state parameter at the current epoch,
and , and the asymptotic value of the equation of state parameter at
, . Their best-fit values are determined jointly
with all other cosmological parameters by the MCMC method using observational
data on CMB anisotropies and polarization, SNe Ia luminosity distances, BAO
measurements and more. Similar computations are carried out for CDM
and a quintessence scalar field model of dark energy. It is shown that the
current data slightly prefer the phantom model, but the differences in the
maximum likelihoods are not statistically significant. It is also shown that
the phantom dark energy with monotonically increasing density in future will
cause the decay of large scale linear matter density perturbations due to the
gravitational domination of dark energy perturbations long before the Big Rip
singularity.Comment: 13 pages, 8 figures, 5 tables; comments and references added; version
accepted for publication in Phys.Rev.
Primordial black holes and their gravitational-wave signatures
In the recent years, primordial black holes (PBHs) have emerged as one of the
most interesting and hotly debated topics in cosmology. Among other
possibilities, PBHs could explain both some of the signals from binary black
hole mergers observed in gravitational wave detectors and an important
component of the dark matter in the Universe. Significant progress has been
achieved both on the theory side and from the point of view of observations,
including new models and more accurate calculations of PBH formation,
evolution, clustering, merger rates, as well as new astrophysical and
cosmological probes. In this work, we review, analyse and combine the latest
developments in order to perform end-to-end calculations of the various
gravitational wave signatures of PBHs. Different ways to distinguish PBHs from
stellar black holes are emphasized. Finally, we discuss their detectability
with LISA, the first planned gravitational-wave observatory in space.Comment: 161 pages, 47 figures, comments welcom
Terrestrial Very-Long-Baseline Atom Interferometry:Workshop Summary
This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions
Sensitivity of the Cherenkov Telescope Array to the gamma-ray emission from neutrino sources detected by IceCube
Gamma-ray observations of the astrophysical neutrino sources are fundamentally important for understanding the underlying neutrino production mechanism. We investigate the Cherenkov Telescope Array (CTA) ability to detect the very-high-energy (VHE) gamma-ray counterparts to the neutrino-emitting Active Galaxies. The CTA performance under different configurations and array layouts is computed based on the neutrino and gamma-ray simulations of steady and transient types of sources, assuming that the neutrino events are detected with the IceCube neutrino telescope. The CTA detection probability is calculated for both CTA sites taking into account the visibility constraints. We find that, under optimal observing conditions, CTA could observe the VHE gamma-ray emission from at least 3 neutrino events per year
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