Search

We develop a cosmological model in $ f(Q, C) $ gravity within the framework of symmetric teleparallel geometry. In addition to the non-metricity scalar $Q $, our formulation includes the boundary term $ C $, which accounts for its deviation from the standard Levi-Civita Ricci scalar $ R^* $ in the Lagrangian. We derive the field equations for the metric and affine connection, employ them within a cosmological setting, and a vanishing affine connection to derive modified Friedmann equations. We use the latest observational dataset OHD in the redshift range $ z \in [0, 2.36]$, Pantheon + SH0ES in the redshift range $ z \in (0.01, 2.26)$, BAO, and the joint datasets OHD + Pantheon + SH0ES and OHD + Pantheon + SH0ES + BAO to constrain the model parameters of our model by employing Markov Chain Monte Carlo (MCMC) method to minimize the $\chi^2$ term. Using the constrained free model parameters we examine the behaviour of different physical parameters of the model and notice that the model transits from deceleration to acceleration. Finally, we observe that the model demonstrates an expanding quintessence dark energy model and converges to the $ \Lambda $CDM in later times., Comment: 19 pages, 18 figures

In this investigation, we perform an observational statistical analysis in the theory of $ f(R, L_m) $ gravity. The proposed theoretical model is based on the Ricci scalar's non-linear contribution. We use a distinct parameterization for the deceleration parameter and constrain the model parameters by using various observational data. To determine the best-fit model for the cosmological parameters, we use different observational datasets such as the Hubble Space Telescope, the Pantheon Supernova Survey, the Gold dataset, the Gamma-Ray Burst (GRB), and the Baryon Acoustic Oscillations (BAO). Furthermore, we study the late-time cosmic evolution of the Universe in detail and examine the implications of the constraint values on cosmological parameters. Additionally, we conduct a thorough comparison with the standard cosmological model $ \Lambda $CDM and other standard models obtained by Odintsov et al. \cite{Odintsov:2023cli, Odintsov:2024lid} to examine the validity of our proposed model in the low-redshift regimes. Finally, we find that the proposed model encapsulates an intriguing transition from early deceleration at high redshift to acceleration at low redshift, a quintessence dark energy scenario, and convergence towards the well-established $ \Lambda $CDM model in late-time Universe's evolution., Comment: 18 pages, 15 figures

In this study, we explore the impact of an additional dimension, as proposed in Kaluza-Klein's theory, on the Casimir effect within the context of Lorentz invariance violation (LIV), which is represented by the ``aether field''. We demonstrate that the Casimir energy is directly influenced by the presence of the fifth dimension, as well as by the aether parameter. Consequently, the force between the plates is also subject to variations of these parameters. Furthermore, we examine constraints on both the size of the extra dimension and the aether field parameter based on experimental data. The LIV parameter can provide insights into addressing the size-related challenges in Kaluza-Klein's theory and offers a mean to establish an upper limit on the size of the extra dimension. This helps to rationalize the difficulties associated with its detection in current experiments., Comment: 13 pages, 7 figures, to appear in PRD

we review the Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO) telescope, an international collaboration, led by Brazil and China, aiming to explore the Universe history through integrated post-reionization 21cm signals and fast radio emissions. For identifying individually fast radio sources, the Advanced Bingo Dark Universe Studies (ABDUS) project has been proposed and developed and will combine the current BINGO construction with the main single-dish telescope and stations of phased-array and outrigger., Comment: 23 pages, work presented in Syros, Greece, September 2022, to appear in Springer

The Baryon Acoustic Oscillations (BAO) from Integrated Neutral Gas Observations (BINGO) radio telescope will use the neutral Hydrogen emission line to map the Universe in the redshift range $0.127 \le z \le 0.449$, with the main goal of probing BAO. In addition, the instrument optical design and hardware configuration support the search for Fast Radio Bursts (FRBs). In this work, we propose the use of a BINGO Interferometry System (BIS) including new auxiliary, smaller, radio telescopes (hereafter \emph{outriggers}). The interferometric approach makes it possible to pinpoint the FRB sources in the sky. We present here the results of several BIS configurations combining BINGO horns with and without mirrors ($4$ m, $5$ m, and $6$ m) and 5, 7, 9, or 10 for single horns. We developed a new {\tt Python} package, the {\tt FRBlip}, which generates synthetic FRB mock catalogs and computes, based on a telescope model, the observed signal-to-noise ratio (S/N) that we used to compute numerically the detection rates of the telescopes and how many interferometry pairs of telescopes (\emph{baselines}) can observe an FRB. FRBs observed by more than one baseline are the ones whose location can be determined. We thus evaluate the performance of BIS regarding FRB localization. We found that BIS will be able to localize 23 FRBs yearly with single horn outriggers in the best configuration (using 10 outriggers of 6 m mirrors), with redshift $z \leq 0.96$; the full localization capability depends on the number and the type of the outriggers. Wider beams are best to pinpoint FRB sources because potential candidates will be observed by more baselines, while narrow beams look deep in redshift. The BIS can be a powerful extension of the regular BINGO telescope, dedicated to observe hundreds of FRBs during Phase 1. Many of them will be well localized with a single horn + 6 m dish as outriggers.(Abridged), Comment: 13 pages, 9 figures, 5 tables, accepted for publication in A&A

In this work, we consider a propagating scalar field on Kaluza-Klein-type cosmological background. It is shown that this geometrical description of the Universe resembles - from a Hamiltonian standpoint - a damped harmonic oscillator with mass and frequency, both time-dependents. In this scenario, we construct the squeezed coherent states (SCSs) for the quantized scalar field by employing the invariant operator method of Lewis-Riesenfeld (non-Hermitian) in a non-unitary approach. The non-classicality of SCSs has been discussed by examining the quadrature squeezing properties from the uncertainty principle. Moreover, we compute the probability density, which allows us to investigate whether SCSs can be used to seek traces of extra dimensions. We then analyze the effects of the existence of supplementary space on cosmological particle production in SCSs by considering different cosmological eras., Comment: 23 pages, 4 figures; version accepted in Annals of Physics

The Universe is currently in a phase of accelerated expansion, a fact that was experimentally proven in the late 1990s. Cosmological models involving scalar fields allow the description of this accelerated expansion regime in the Cosmos and present themselves as a promising alternative in the study of the inflationary eras, especially the actual one which is driven by the dark energy. In this work we use the $f(R, T) - \Lambda(\phi)$ gravity to find different cosmological scenarios for our Universe. We also introduce a new path to derive analytic cosmological models which may have a non-trivial mapping between $f$ and $T$. We show that the analytic cosmological models obtained with this approach are compatible with a good description of the radiation era. In addition, we investigated the inflationary scenario and obtained a good agreement for the scalar spectral index $n_s$. Concerning the tensor-to-scalar ratio $r$, we found promising scenarios compatible with current CMB data., Comment: 10 figures; to be published in Physics of the Dark Universe

A possible astrophysical object to be found in General Relativity is the wormhole. This special solution describes a topological bridge connecting points in two distinguished universes or two different points in the same universe. Despite it was never observed so far, is desired to find traversable wormholes, i.e. wormholes which have a throat at which there is no horizon. However, the traversable wormhole constraints yield solutions that violate all the energy conditions in General Relativity. In the last few years, several models to describe gravity beyond $\Lambda$CDM have been proposed. Then, it is relevant to look for wormhole solutions for these new theories. In this study, we are going to unveil new wormhole solutions for the so-called $f(Q,T)$ gravity. This theory of gravity is based on the non-metricity scalar $Q$, which is responsible for the gravitational interaction together with the energy-momentum trace $T$. We use the embedding procedure to find both the energy and the equilibrium conditions for the existence of wormholes. Then, the nontrivial contributions coming from $f(Q,T)$ gravity are embedded into the effective equations for density and pressures. We also considered the presence of exotic strange matter in the wormhole throat. Such a matter obeys the notorious MIT bag Model. We are going to present new scenarios confirming the viability of traversable wormholes in $f(Q,T)$ gravity with the strange matter, satisfying SEC and WEC energy conditions., Comment: Comments are welcome

In this article, we study a flat homogeneous FLRW model in Lyra geometry which is described by a time-dependent displacement vector. We consider an appropriate parametrization of the energy density of scalar field $ \rho_\phi $ in terms of the cosmic scale factor. The result shows two transitions from deceleration to acceleration. Furthermore, we constrain the model parameter $ \alpha $ and the displacement field vector $ \beta $ using the recent supernovae data, Hubble data set of 77 points, and their joint data which predicts the accelerated expanding phase of the universe in late times. The effective equation of state parameter $ \omega_{eff} $ speculate $ \Lambda $CDM in late times. Finally, we use the statefinder diagnostic to differentiate our model from the various dark energy models., Comment: 14 pages, 14 figures

An intriguing solution that appears in General Relativity (GR) but has not been observed so far is the wormhole. This exotic solution describes a topological bridge connecting two distinct universes or two different points in the same universe. It is known that the traversable wormhole solutions violate all the energy conditions in GR, resulting in their instability. In this work, we are going to unveil new wormhole solutions for $f(Q)$ gravity where $Q$ is the non-metricity scalar, which is responsible for the gravitational interaction. The energy conditions to constraint these wormhole solutions were derived using the embedding procedure. This procedure consists of rewriting the density and the pressures of the solutions as those presented by General Relativity. Then, the nontrivial contributions coming from new theories of gravity are embedded into the effective equations for density and pressures. Along with our approach, we carefully analyze two families of $f(Q)$ models and we used two different shape functions to build the wormholes solutions for each of these $f(Q)$ models. We are going to present new scenarios with the possibility of traversable wormholes satisfying SEC or DEC energy conditions in the presence of exotic matter., Comment: EPL published version

We study an isotropic flat FLRW-model in Scale-covariant theory of gravity $ f_{\gamma \delta}(\phi) $ \cite{Canuto:1977zz} which is explained in terms of ordinary and covariant differentiation of scalar field $ \phi $. As we know the deceleration parameter is time-dependent, so we consider the deceleration parameter $ q $ as the function of $ t $. Using this methodology, we find all the important cosmological factors in terms of a hyperbolic function of the cosmic time $ t $. In turn, we create the model having the behavior of the late-time universe, which is ever accelerated expanding and faces a Big Freeze at the end. The model shows the quintessence dark energy model from early to late times. We compute the constrained values of Hubble parameter $ H_0=70.979^{+0.021}_{-0.0043} $ and the model parameter $ n=1.24079^{+0.00015}_{-0.00079} $ using joint analysis of the $ OHD $ data of 77-points and Pantheon bin data. The model exhibits point-type singularity, beginning with a point of zero volume, infinite energy density, and temperature. Furthermore, we obtain the present deceleration parameter $ (q_0) \approx {-0.54} $. Also, we examine the ultimate behavior of our model by properly analyzing energy conditions, cosmographical parameters, and Statefinder diagnostic. Finally, the proposed model behaves like a quintessence dark energy model., Comment: 20 pages, 19 figures

Observations of the redshifted 21-cm line of neutral hydrogen (HI) are a new and powerful window of observation that offers us the possibility to map the spatial distribution of cosmic HI and learn about cosmology. BINGO (Baryon Acoustic Oscillations [BAO] from Integrated Neutral Gas Observations) is a new unique radio telescope designed to be one of the first to probe BAO at radio frequencies. BINGO has two science goals: cosmology and astrophysics. Cosmology is the main science goal and the driver for BINGO's design and strategy. The key of BINGO is to detect the low redshift BAO to put strong constraints in the dark sector models. Given the versatility of the BINGO telescope, a secondary goal is astrophysics, where BINGO can help discover and study Fast Radio Bursts (FRB) and other transients, Galactic and extragalactic science. In this paper, we introduce the latest progress of the BINGO project, its science goals, describing the scientific potential of the project in each science and the new developments obtained by the collaboration. We introduce the BINGO project and its science goals and give a general summary of recent developments in construction, science potential and pipeline development obtained by the BINGO collaboration in the past few years. We show that BINGO will be able to obtain competitive constraints for the dark sector, and also that will allow for the discovery of several FRBs in the southern hemisphere. The capacity of BINGO in obtaining information from 21-cm is also tested in the pipeline introduced here. There is still no measurement of the BAO in radio, and studying cosmology in this new window of observations is one of the most promising advances in the field. The BINGO project is a radio telescope that has the goal to be one of the first to perform this measurement and it is currently being built in the northeast of Brazil. (Abridged), Comment: 23 pages. To appear in A&A

The measurement of diffuse 21-cm radiation from the hyperfine transition of neutral hydrogen (HI signal) in different redshifts is an important tool for modern cosmology. However, detecting this faint signal with non-cryogenic receivers in single-dish telescopes is a challenging task. The BINGO (Baryon Acoustic Oscillations from Integrated Neutral Gas Observations) radio telescope is an instrument designed to detect baryonic acoustic oscillations (BAOs) in the cosmological HI signal, in the redshift interval $0.127 \le z \le 0.449$. This paper describes the BINGO radio telescope, including the current status of the optics, receiver, observational strategy, calibration, and the site. BINGO has been carefully designed to minimize systematics, being a transit instrument with no moving dishes and 28 horns operating in the frequency range $980 \le \nu \le 1260$ MHz. Comprehensive laboratory tests were conducted for many of the BINGO subsystems and the prototypes of the receiver chain, horn, polarizer, magic tees, and transitions have been successfully tested between 2018 - 2020. The survey was designed to cover $\sim 13\%$ of the sky, with the primary mirror pointing at declination $\delta=-15^{\circ}$. The telescope will see an instantaneous declination strip of $14.75^{\circ}$. The results of the prototype tests closely meet those obtained during the modeling process, suggesting BINGO will perform according to our expectations. After one year of observations with a $60\%$ duty cycle and 28 horns, BINGO should achieve an expected sensitivity of 102 $\mu K$ per 9.33 MHz frequency channel, one polarization, and be able to measure the HI power spectrum in a competitive time frame., Comment: 13 pages, accepted for publication in A&A