2,831 research outputs found
Effective field description of the Anton-Schmidt cosmic fluid
The effective theory of the Anton-Schmidt cosmic fluid within the Debye
approximation is investigated. In this picture, the universe is modeled out by
means of a medium without cosmological constant. In particular, the
Anton-Schmidt representation of matter describes the pressure of crystalline
solids under deformations imposed by isotropic stresses. The approach scheme is
related to the fact that the universe deforms under the action of the cosmic
expansion itself. Thus, we frame the dark energy term as a function of scalar
fields and obtain the corresponding dark energy potential .
Different epochs of the universe evolution are investigated in terms of the
evolution of . We show how the Anton-Schmidt equation of state is
capable of describing both late and early epochs of cosmic evolution. Finally,
numerical bounds on the Anton-Schmidt model with are derived through a
Markov Chain Monte Carlo analysis on the combination of data coming from type
Ia Supernovae, observations of Hubble parameter and baryon acoustic
oscillations. Statistical comparison with the CDM model is performed
by the AIC and BIC selection criteria. Results are in excellent agreement with
the low-redshift data. A further generalization of the model is presented to
satisfy the theoretical predictions at early-stage cosmology.Comment: 13 pages, Accepted for publication in Phys. Rev.
De Sitter-like configurations with asymptotic quintessence environment
We examine a spherically-symmetric class of spacetimes carrying vacuum
energy, while considering the influence of an external dark energy environment
represented by a non-dynamical quintessence field. Our investigation focuses on
a specific set of solutions affected by this field, leading to distinct kinds
of spacetime deformations, resulting in regular, singular, and wormhole
solutions. We thoroughly discuss the underlying physics associated with each
case and demonstrate that more complex deformations are prone to instability.
Ultimately, we find that our results lead to an \emph{isotropic de Sitter-like
solution} that behaves as a quintessence fluid. To achieve this, we investigate
the nature of the corresponding fluid, showing that it cannot provide the sound
speed equal to a constant equation of state near the center. Consequently, we
reinterpret the fluid as a slow-roll quintessence by investigating its behavior
in asymptotic regimes. Further, we explore the potential implications of
violating the isotropy condition on the pressures and we finally compare our
findings with the de Sitter and Hayward solutions, highlighting both the
advantages and disadvantages of our scenarios.Comment: 14 pages, 4 figures, 1 tabl
Phenomenology at the LHC of composite particles from strongly interacting Standard Model fermions via four-fermion operators of NJL type
A new physics scenario shows that four-fermion operators of
Nambu-Jona-Lasinio (NJL) type have a strong-coupling UV fixed point, where
composite fermions (bosons ) form as bound states of three (two) SM
elementary fermions and they couple to their constituents via effective contact
interactions at the composite scale (TeV). We
present a phenomenological study to investigate such composite particles at the
LHC by computing the production cross sections and decay widths of composite
fermions in the context of the relevant experiments at the LHC with
collisions at TeV and TeV.
Systematically examining all the different composite particles and the
signatures with which they can manifest, we found a vast spectrum of composite
particles that has not yet been explored at the LHC. Recasting the recent
CMS results of the resonant channel , we find that the composite fermion mass below 4.25 TeV is
excluded for / = 1. We further highlight the region of parameter
space where this specific composite particle can appear using 3 ab,
expected by the High-Luminosity LHC, computing 3 and 5 contour plots
of its statistical significance.Comment: To appear in EPJC. This revised version expands the search for
composite fermion F considering all its possible flavors and topologies and
highlighting the signatures not yet investigated at LH
Constraining primordial black holes as fraction of dark matter through accretion disk luminosity
In this paper, we consider the hypothesis that fractions of dark matter could
be constituted by primordial black holes (PBHs). To test this possibility, we
work out the observational properties of a static black hole embedded in the
dark matter envelope made of a PBH source. The corresponding modifications of
geometry due to such a physical system are investigated, with particular focus
on the accretion disk luminosity in spiral galaxies. The impact of the PBH
presence is analyzed through modification of the disk luminosity and kinematic
quantities. Thus, we discuss possible constraints on the PBH abundance in view
of the most recent theoretical bounds. The results of our study indicate that
suitable PBH masses are for PBH
fractions . In particular, a comparison with the
predictions of the exponential sphere density profile for dark matter suggests
that the best-matching configuration is achieved for and
. Consequences with respect to the current knowledge
on primordial black hole physics are discussed.Comment: 9 pages, 6 figure
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