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The search for a space-time variation of the fundamental constants has been explored over the years to test our physical theories. In this paper, we use the dispersion measure ($DM$) of fast radio bursts (FRB) combined with type Ia supernovae (SNe) data to investigate a possible redshift evolution of the fine-structure constant ($\alpha$), considering the runaway dilaton scenario, which predicts $\frac{\Delta \alpha}{\alpha} = - \gamma\ln{(1+z)}$, where $\gamma$ is a constant proportional to the current value of the coupling between the dilaton field and hadronic matter. We derive all the relevant expressions for the $DM$ dependence concerning the fine-structure constant and constrain the parameter $\gamma$ from measurements of 17 well-localized FRBs and 1048 SNe data from the Pantheon compilation. We also use Monte Carlo simulations to forecast the constraining power of larger samples of FRB measurements for data sets with $N = 500$ and $N = 1000$ points. We found that the uncertainty on $\gamma$ can be improved by one order of magnitude and that limits on $\frac{\Delta \alpha}{\alpha}$ beyond $\sigma \sim 10^{-2}$ will depend crucially on better control of statistical and systematic uncertainties of upcoming FRB data., Comment: 18 pages, 4 figures, 2 tables

Central Bank Digital Currency (CBDC) can be defined as a virtual currency based on node network and digital encryption algorithm issued by a country which has a legal credit protection. CBDCs are supported by Distributed Ledger Technologies (DLTs), and they may allow a universal means of payments for the digital era. There are many ways to proceed, they all require central banks to develop technological expertise. Considering these points, it is important to understand the new IT governance in the financial markets due to CBDC and digital economy. Information Technology is an essential driver that will allow the new financial industry design. This paper has the objective to answer two questions through an updated Systematic Literature Review (SLR). The first question is What IT resources and tools have been considered or applied to set the governance of CBDC adoption? The second; Identify IT governance models in the financial market due to CBDC adoption. Bank for International Settlements (BIS) publications, Scopus and Web of Science were considered as sources of studies. After the strings and including criteria were applied, fourteen papers were analyzed. This paper finds many IT resources used in the CBDC adoption and some preliminary IT design related to the IT governance of CBDC, in the results and discussion section the findings are more detailed. Finally, limitations and future work are considered. Keywords: Blockchain, Central Bank Digital Currency (CBDC), Digital Economy, Distributed Ledger Technology (DLT), Information Technology (IT), IT governance., Comment: Keywords: Blockchain, Central Bank Digital Currency (CBDC), Digital Economy, Distributed Ledger Technology (DLT), Information Technology (IT), IT governance

In standard cosmology, the cosmic homogeneity scale is the transition scale above which the patterns arising from non-uniformities -- such as groups and clusters of galaxies, voids, and filaments -- become indistinguishable from a random distribution of sources. Recently, different groups have investigated the feasibility of using such a scale as a cosmological test and arrived at different conclusions. In this paper, we complement and extend these studies by exploring the evolution of the spatial (${\cal{R}}_H$) and angular ($\theta_H$) homogeneity scales with redshift, assuming a spatially flat, $\Lambda$-Cold Dark Matter %($\Lambda$CDM) universe and linear cosmological perturbation theory. We confirm previous results concerning the non-monotonicity of ${\cal{R}}_H$ with the matter density parameter $\Omega_{m0}$ but also show that it exhibits a monotonical behavior with the Hubble constant $H_0$ within a large redshift interval. More importantly, we find that, for $z \gtrsim 0.6$, the angular homogeneity scale not only presents a monotonical behavior with $\Omega_{m0}$ and $H_0$ but is quite sensitive to $H_0$, especially at higher redshifts. These results, therefore, raise the possibility of using $\theta_H$ as a new, model-independent way to constrain cosmological parameters., Comment: 10 pages, 24 figures

Fast Radio Bursts (FRBs) are millisecond transient radio events with a high energy. By identifying the origin of the \textbf{burst}, it is possible to measure the redshift of the host galaxy, which can be used to constrain cosmological and astrophysical parameters and test aspects of fundamental physics when combined with the dispersion measure ($DM$). However, some factors limit the cosmological application of FRBs: (i) the poor modelling of the fluctuations in the $DM$ due to spatial variation in the cosmic electrons density; (ii) the fact that the fraction of baryon mass in the intergalactic medium ($f_{IGM}$) is degenerated with some cosmological parameters; (iii) the limited knowledge about host galaxy contribution ($DM_{host}$). In this work, we investigate the impact of different redshift distribution models of FRBs to constrain the baryon fraction in the IGM and host galaxy contribution. We use a cosmological model-independent method developed in previous work \cite{Lemos2023} to perform the analysis and combine simulated FRB data from Monte Carlo simulation and supernovae data. We assume four distribution models for the FRBs: gamma-ray bursts (GRB), star formation rate (SFR), uniform and equidistant (ED). Also, we consider samples with $N = 15, 30, 100$ and $500$ points and different values of the fluctuations of electron density in the $DM$, $\delta = 0, 100, 200, 400, 230\sqrt{z}$ pc/cm$^{3}$. Our analysis shows that all the distribution models present consistent results within $2\sigma$ for the free parameters $f_{IGM}$ and $DM_{host,0}$ and highlights the crucial role of $DM$ fluctuations in obtaining more precise measurements., Comment: 11 pages, 4 figures

Fast Radio Bursts (FRBs) are millisecond-duration radio transients with an observed dispersion measure ($DM$) greater than the expected Milky Way contribution, which suggests that such events are of extragalactic origin. Although some models have been proposed to explain the physics of the pulse, the mechanism behind the FRBs emission is still unknown. From FRBs data with known host galaxies, the redshift is directly measured and can be combined with estimates of the $DM$ to constrain the cosmological parameters, such as the baryon number density and the Hubble constant. However, the poor knowledge of the fraction of baryonic mass in the intergalactic medium ($f_{IGM}$) and its degeneracy with the cosmological parameters impose limits on the cosmological application of FRBs. In this work we present a cosmological model-independent method to determine the evolution of $f_{IGM}$ combining the latest FRBs observations with localized host galaxy and current supernovae data. We consider constant and time-dependent $f_{IGM}$ parameterizations and show, through a Bayesian model selection analysis, that a conclusive answer about the time-evolution of $f_{IGM}$ depend strongly on the $DM$ fluctuations due to the spatial variation in cosmic electron density ($\delta$). In particular, our analysis show that the evidence varies from strong (in favor of a growing evolution of $f_{IGM}$ with redshift) to inconclusive, as larger values of $\delta$ are considered., Comment: 8 pages, 3 figures

We report measurements of the angular scale of cosmic homogeneity ($\theta_{H}$) using the recently released luminous red galaxy sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV LRG DR16). It consists of a model-independent method, as we only use the celestial coordinates of these objects to carry out such an analysis. The observational data is divided into thin redshift bins, namely $0.67

We report measurements of the scale of cosmic homogeneity ($r_{h}$) using the recently released quasar sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV DR16). We perform our analysis in 2 redshift bins lying in the redshift interval $2.2 < z < 3.2$ by means of the fractal dimension $D_2$. By adopting the usual assumption that $r_{h}$ is obtained when $D_2 \sim 2.97$, that is, within 1% of $D_2=3$, we find the cosmic homogeneity scale with a decreasing trend with redshift, and in good agreement with the $\Lambda$CDM prediction. Our results confirm the presence of a homogeneity scale in the spatial distribution of quasars as predicted by the fundamental assumptions of the standard cosmological model., Comment: 8 pages, 3 figures, accepted for publication in JCAP

The possibility of variation of the fundamental constants of nature has been a long-standing question, with important consequences for fundamental physics and cosmology. In particular, it has been shown that variations in the fine-structure constant, $\alpha$, are directly related to violation of the distance duality relation (DDR), which holds true as long as photons travel on unique null geodesics and their number is conserved. In this paper we use the currently available measurements of ${\Delta \alpha}/{\alpha}$ to impose the most stringent constraints on departures of the DDR to date, here quantified by the parameter $\eta$. We also perform a forecast analysis to discuss the ability of the new generation of high-resolution spectrograph, like ESPRESSO/VLT and E-ELT-HIRES, to constrain the DDR parameter $\eta$. From the current data we obtain constraints on $\eta$ of the order of $10^{-7}$ whereas the forecasted constraints are two orders of magnitude lower. Considering the expected level of uncertainties of the upcoming measurements, we also estimate the necessary number of data points to confirm the hypotheses behind the DDR., Comment: 8 pages, 3 figures