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We explore a cosmological model inspired by the modified Kaniadakis entropy and disclose the influences of the modified Friedmann equations on the evolution of the Universe. We find that in modified Kaniadakis cosmology with only pressure-less matter, one can reproduce the accelerated Universe without invoking any kind of dark energy. We delve into the evolution of the Universe during the radiation-dominated era as well. We also investigate the behavior of the scale factor and the deceleration parameter for a multiple-component Universe consisting of pressure-less matter and a cosmological constant/dark energy. Interestingly enough, the predicted age of the Universe in the modified Kaniadakis cosmology becomes larger compared to the standard cosmology which may alleviate the age problem. Furthermore, the findings reveal that in the modified Kaniadakis cosmology, the transition from a decelerated phase to an accelerated Universe occurs at higher redshifts compared to the standard cosmology. These results shed light on the potential implications of incorporating Kaniadakis entropy into cosmological models and provide valuable insights into the behavior of the Universe in different cosmological scenarios. Moreover, they emphasize the crucial role of modifications to the geometry component and the significance of such modifications in understanding the dynamics of the Universe. [ABSTRACT FROM AUTHOR]

We study a group field theory (GFT) for quantum gravity coupled to four massless scalar fields, using these matter fields to define a (relational) coordinate system. We exploit symmetries of the GFT action, in particular under shifts in the values of the scalar fields, to derive a set of classically conserved currents, and show that the same conservation laws hold exactly at the quantum level regardless of the choice of state. We propose a natural interpretation of the conserved currents which implies that the matter fields always satisfy the Klein–Gordon equation in GFT. We then observe that in our matter reference frame, the same conserved currents can be used to extract all components of an effective GFT spacetime metric. Finally, we apply this construction to the simple example of a spatially flat homogeneous and isotropic Universe, where we derive an effective Friedmann equation directly from this metric. The Friedmann equation displays a bounce and a late-time limit equivalent to general relativity with a single scalar field. Our proposal goes substantially beyond the GFT literature in which only specific geometric quantities such as the total volume or volume perturbations could be defined, opening up the possibility to study more general geometries as emerging from GFT. [ABSTRACT FROM AUTHOR]

The ability of Big Bang Nucleosynthesis theory to accurately predict the primordial abundances of helium and deuterium, as well as the baryon content of the Universe, is considered one of the most significant achievements in modern physics. In the present study, we consider two highly motivated hybrid |$f(T)$| models and constrain them using the observations from the Big Bang Nucleosynthesis era. In addition, using late-time observations of Cosmic Chronometers and Gamma-Ray Bursts, the ranges of the model parameters are confined which are in good agreement with early time bounds. Subsequently, the common ranges obtained from the analysis for early and late time are summarized. Further, we verify the intermediating epochs by investigating the profiles of cosmographic parameters using the model parameter values from the common range. From this study, we find the considered teleparallel models are viable candidates to explain the primordial-intermediating-present epochs. [ABSTRACT FROM AUTHOR]

The Janis–Newman–Winicour spacetime corresponds to a static spherically symmetric solution of Einstein equations with the energy momentum tensor of a massless quintessence field. It is understood that the spacetime describes a naked singularity. The solution has two parameters, b and s. To our knowledge, the exact physical meaning of the two parameters is still unclear. In this paper, starting from the Janis–Newman–Winicour naked singularity solution, we first obtain a wormhole solution by a complex transformation. Then, letting the parameter s approach infinity, we obtain the well-known exponential wormhole solution. After that, we embed both the Janis–Newman–Winicour naked singularity and its wormhole counterpart in the background of a de Sitter or anti-de Sitter universe with the energy momentum tensor of massive quintessence and massive phantom fields, respectively. To our surprise, the resulting quintessence potential is actually the dilaton potential found by one of us. It indicates that, by modulating the parameters in the charged dilaton black hole solutions, we can obtain the Janis–Newman–Winicour solution. Furthermore, a charged wormhole solution is obtained by performing a complex transformation on the charged dilaton black hole solutions in the background of a de Sitter or anti-de Sitter universe. We eventually find that s is actually related to the coupling constant of the dilaton field to the Maxwell field and b is related to a negative mass for the dilaton black holes. A negative black hole mass is physically forbidden. Therefore, we conclude that the Janis–Newman–Winicour naked singularity solution is not physically allowed. [ABSTRACT FROM AUTHOR]

To describe the dark side of the universe, we adopt a novel approach where dark energy is explained as an electrically charged majority of dark matter. Dark energy, as such, does not exist. The Friedmann equation at the present time coincides with that in a conventional approach, although the cosmological "constant" in the Electromagnetic Accelerating Universe (EAU) Model shares a time dependence with the matter component. Its equation of state is ω ≡ P/ρ ≡ −1 within observational accuracy. [ABSTRACT FROM AUTHOR]

The general relativity unification and quantum theory is a significant open problem in theoretical physics. This problem arises from the fact that these two fundamental theories, which describe gravity and the behavior of particles at the microscopic level, respectively, are currently incompatible. The unification of these theories is crucial for a complete comprehension of the fundamental forces and the nature of the universe. In this regard, the quantum properties of a Black Hole result in fundamental importance. By analyzing such properties in quantum field theory, in the first step, the gravity enters as a classical background. In semi-classical approximation, Black Holes will emit Hawking radiation with an almost thermal spectrum, while Black Hole's entropy is proportional to the Black Hole's horizon. Besides, Hawking's temperature and Black Hole entropy should follow the first law of Black Hole thermodynamics. Also, Jacobson [Thermodynamics of spacetime: The Einstein equation of state, Phys. Rev. Lett.75 (1995) 1260, doi:10.1103/PhysRevLett.75.1260] showed shown that there is a connection between Black Hole thermodynamics and Einstein's equation that opens the root of a potential thermodynamic nature of gravity. This issue opened a new impressive research framework in which the Einstein field equation can be expressed as a form of the first law of thermodynamics and vice versa. In this study, it is assumed that the universe has a fractal structure. Accordingly, modified Friedmann's equations and the Black Holes thermodynamics in a fractal universe have been examined. The fractal framework shows what features and changes occur in the description of the universe, particularly in studying the thermodynamics of a Black Hole. However, the paper strategy is organized as follows: in the beginning, we consider the first thermodynamic law in a fractal universe. Then, we investigate the Friedmann equation of the fractal universe in the form of the entropy balance, this means d Q = T h d S h , where d Q and T h are the thermal energy and horizon temperature. We consider the entropy S h have two terms; (1) obeys the usual area law and (2) the entropy production term due to the non-equilibrium thermodynamics of a fractal universe. Therefore, in a fractal universe, a term with non-equilibrium thermodynamics of spacetime may be needed. Also, we study the generalized second law of thermodynamics in a fractal universe. When the temperature of the apparent horizon and the temperature of the matter fields inside the horizon are equal, i.e. T = T h , the second law of generalized thermodynamics can be obtained according to the state parameter range equation, which is consistent with the recent observations. Finally, in Sec. 6, based on the mathematical calculations, we study the various cosmological parameters such as the Hubble parameter, scale factor, deceleration parameter and equation of state parameter. [ABSTRACT FROM AUTHOR]

Relaxing the temporal constancy constraint on coupling constants in an expanding universe results in Friedmann equations containing terms that may be interpreted as dark energy and dark matter. When tired light (TL) was considered to complement the redshift due to the expanding universe, the resulting covarying coupling constants (CCC+TL) model not only fit the Type Ia supernovae data as precisely as the ΛCDM model, but also resolved concerns about the angular size of cosmic dawn galaxies observed by the James Webb Space Telescope. The model was recently shown to be compliant with the baryon acoustic oscillation features in the galaxy distribution and the cosmic microwave background (CMB). This paper demonstrates that dark energy and dark matter of the standard ΛCDM model are not arbitrary but can be derived from the CCC approach based on Dirac's 1937 hypothesis. The energy densities associated with dark matter and dark energy turn out to be about the same in the ΛCDM and the CCC+TL models. However, the critical density in the new model can only account for the baryonic matter in the universe, raising concerns about how to account for observations requiring dark matter. We therefore analyze some key parameters of structure formation and show how they are affected in the absence of dark matter in the CCC+TL scenario. It requires reconsidering alternatives to dark matter to explain observations on gravitationally bound structures. Incidentally, since the CCC models inherently have no dark energy, it has no coincidence problem. The model's consistency with the CMB power spectrum, BBN element abundances, and other critical observations is yet to be established. [ABSTRACT FROM AUTHOR]

We start with the cosmic Friedmann equations, where we adopt a novel perspective rooted in a Lagrangian formulation, grounded in Newtonian mechanics and the first law of thermodynamics. Our investigation operates under the assumption that the universe is populated by either a perfect fluid or a scalar field. By elucidating the intricate interplay between the Lagrangian formulation and the cosmic Friedmann equations, we uncover the fundamental principles governing the universe's dynamics within the framework of these elemental constituents. In our concluding endeavor, we embark on the task of harmonizing the classical equations—namely, the conservation, Euler, and Poisson equations—with the principles of General Relativity. This undertaking seeks to extend these foundational equations to encompass the gravitational effects delineated by General Relativity, thus providing a comprehensive framework for understanding the behavior of matter and spacetime in the cosmic context. [ABSTRACT FROM AUTHOR]

This is a summary of the main results within the Scale-Invariant Vacuum (SIV) paradigm based on Weyl integrable geometry. We also review the mathematical framework and utilize alternative derivations of the key equations based on the reparametrization invariance as well. The main results discussed are related to the early universe; that is, applications to inflation, Big Bang Nucleosynthesis, and the growth of the density fluctuations within the SIV. Some of the key SIV results for the early universe are a natural exit from inflation within the SIV in a later time t exit with value related to the parameters of the inflationary potential along with the possibility for the density fluctuations to grow sufficiently fast within the SIV without the need for dark matter to seed the growth of structure in the universe. In the late-time universe, the applications of the SIV paradigm are related to scale-invariant dynamics of galaxies, MOND, dark matter, and dwarf spheroidals, where one can find MOND to be a peculiar case of the SIV theory. Finally, within the recent time epoch, we highlight that some of the change in the length-of-the-day (LOD), about 0.92 cm/yr, can be accounted for by SIV effects in the Earth–Moon system. [ABSTRACT FROM AUTHOR]

In this article, we focus on the inflation dynamics of the early Universe using an inverse power law potential scalar field (V(ϕ) = V0ϕ-n) within the framework of Tsallis entropy. First, we derive the modified Friedmann equations from the non-additive Tsallis entropy by applying the first law of thermodynamics to the apparent horizon of the Friedmann-Robertson-Walker (FRW) Universe. We assume that the inflationary era of the Universe consists of two phases; the slow roll inflation phase and the kinetic inflation phase. We obtained the scalar spectral index ηs and tensor-to-scalar ratio r and compared our results with the latest Planck data for these phases. By choosing the appropriate values for the Tsallis parameters, which bounded by α < 2, and the inverse power-term of the potential η, we determined that the inflation era of the Universe in Tsallis entropy can only occur in the second phase (kinetic inflation), while the slow-roll inflation phase is incompatible with the Planck data. [ABSTRACT FROM AUTHOR]

The f (R , T) theory of gravity investigated by Harko et al. [T. Harko, F. S. N. Lobo, S. Nojiri and S. D. Odintsov, Phys. Rev. D 84 (2011) 024020; T. Harko, Phys. Rev. D 90(4) (2014) 044067] serves as the inspiration for the homogeneous and isotropic cosmological model presented in generalized f (R , T ϕ) theories connected with a scalar field. Assuming that T ϕ is the trace of the energy-momentum tensor, f (R , T ϕ) gravity can be understood as f (R , T) gravity with a self-interacting scalar field ϕ. To address this, we provide a novel model-independent method for the parametrization of the Hubble parameter, and we apply it to the Friedmann equations in the FLRW Universe. The Markov Chain Monte Carlo (MCMC) approach is then used to estimate the best-fit values of the model parameters using a combination of the updated H (z) dataset, which comprises 57 points, and the Pantheon dataset, which contains 1048 points. The evolution of the deceleration parameter shows a transition from the universe's deceleration phase to its acceleration phase. We also investigate the behavior of the statefinder and the Om diagnostic parameter. Finally, a thorough discussion of the model's physical attributes has been carried out. [ABSTRACT FROM AUTHOR]

The accelerated expansion of the Universe is impressively well described by a cosmological constant. However, the observed value of the cosmological constant is much smaller than expected based on quantum field theories. Recent efforts to achieve consistency in these theories have proposed a relationship between Dark Energy and the most compact objects, such as black holes (BHs). However, experimental tests are very challenging to devise and perform. In this article, we present a testable model with no cosmological constant in which the accelerated expansion can be driven by black holes. The model couples the expansion of the Universe (the Friedmann equation) with the mass function of cosmological halos (using the Press–Schechter formalism). Through the observed link between halo masses and BH masses, one thus gets a coupling between the expansion rate of the Universe and the BHs. We compare the predictions of this simple BH model with SN1a data and find poor agreement with observations. Our method is sufficiently general to allow us to also test a fundamentally different model, also without a cosmological constant, where the accelerated expansion is driven by a new force proportional to the internal velocity dispersion of galaxies. Surprisingly enough, this model cannot be excluded using the SN1a data. [ABSTRACT FROM AUTHOR]

We present for the first time a Friedmann-like construction in the framework of an osculating Finsler–Randers–Sasaki (F–R–S) geometry. In particular, we consider a vector field in the metric on a Lorentz tangent bundle, and thus the curvatures of horizontal and vertical spaces, as well as the extra contributions of torsion and non-linear connection, provide an intrinsic richer geometrical structure, with additional degrees of freedom, that lead to extra terms in the field equations. Applying these modified field equations at a cosmological setup we extract the generalized Friedmann equations for the horizontal and vertical space, showing that we obtain an effective dark energy sector arising from the richer underlying structure of the tangent bundle. Additionally, as it is common in Finsler-like constructions, we obtain an effective interaction between matter and geometry. Finally, we consider a specific model and we show that it can describe the sequence of matter and dark-energy epochs, and that the dark-energy equation of state can lie in the quintessence or phantom regimes, or cross the phantom divide. [ABSTRACT FROM AUTHOR]

We analyse traversable wormholes defined by the dynamic line elements that asymptotically approach Friedmann–Robertson–Walker (FRW) universe. These dynamical wormholes is supported by the galactic dark matter as well as perfect isotropic fluid. We will discuss several evolving Lorentzian wormholes comprising with different perfect isotropic fluids in addition to various scale factors. We will speculate the various significance, features and throat energy conditions for these evolving traversable Lorentzian wormholes. [ABSTRACT FROM AUTHOR]

We experience some challenges in general gravitational theory owing to Einstein to explain late time acceleration of universe. To address this issue, geometric components of gravity have been modified in quite a few occasions to have a more general structure with some freedom. One such approach is to change the geometric components of gravity where gravitational interaction is denoted by Q, Q being the non-metricity. In our work, we have considered symmetric teleparallel gravity i.e, modified the geometry with the help of non-metricity Q or f (Q) gravity. We have considered a specific form of f (Q) which is nothing but the linear combination of Q and α Q n , n ≠ 1 , where Q is coupled with Lagrangian matter. Forming the autonomous system from governing equations and then solving it, we have tried to analyze the nature of universe using dynamical system analysis. We have studied the behavior of the universe under several circumstances. Then, we have studied the stability around critical points and considering the recent observational data available for some cosmological parameters, feasible solutions are noted which depict late time acceleration. We can see that f (Q) gravity model can be considered as an alternative model to Λ CDM model. [ABSTRACT FROM AUTHOR]

Numerous studies have tried to explain the observed late acceleration of the Universe as being caused by the bulk viscosity associated with the dark matter (DM) component. However, for driving the said accelerated expansion, all such models require a violation of near equilibrium conditions (NECs) associated with the background viscous theory. But recently, it was found that, with the aid of a cosmological constant, it is possible to maintain NEC for the bulk viscous warm DM during certain evolutionary epochs of the Universe. Nevertheless, this negated the possibility of having a 'solely' viscous-driven late acceleration in Einstein gravity within the NEC limit. In the present study, we investigate a model of the Universe composed of mixed DM components, with viscous DM, and inviscid cold DM as its constituents, in the context of R + 2 λ T v m gravity, and show that the model predicts late acceleration by satisfying NEC, critical energy condition and second law of thermodynamics (SLT) throughout the evolution, even in the absence of a cosmological constant. One intriguing feature observed in this model is the possibility of having a negative bulk viscous coefficient and yet satisfying the SLT. Finally, by applying both theoretical and observational constraints on the model parameters, we determined the best-fit values of model parameters and thereby analyzed the evolutionary behavior of some relevant cosmological observables. [ABSTRACT FROM AUTHOR]

It is a fact that the universe lives on a gravitational wave background (GWB), which is extra space–time energy that is not contained in Einstein's field equations. In a previous work, this energy is treated as a property of space–time and not as a source. With this in mind, a new model was developed that incorporates this energy to explain the current accelerated expansion of the universe where the GWB was incorporated by extending Einstein's equations to |$R_{\mu \nu }-\frac{1}{2}Rg_{\mu \nu }+\frac{2\pi ^2}{{\lambda }^2}g_{\mu \nu }= \kappa ^2 T_{\mu \nu }$|⁠ , where λ is the Compton wavelength of the cosmological scale graviton. In the present work, we show that this extended form agrees very well with the observations of cosmic chronometers, baryon acoustic oscillations, and Pantheon SN Type Ia, reproducing the observational data with a Δχ2 = 3.26 in favour of the current model compared to the ΛCDM. The favoured values by these observations are Ω0m = 0.311 ± 0.065, H 0 = 68.3 ± 1.4 km s−1 Mpc−1, and Ω0k = 0.001 ± 0.011. We also find excellent agreement of this model with the cosmic microwave background and the mass power spectrum. We conclude that this model is an excellent alternative to explain the accelerated expansion of the universe without incorporating the cosmological constant or any type of extra matter. [ABSTRACT FROM AUTHOR]

Redshift drift is the phenomenon whereby the observed redshift between an emitter and observer comoving with the Hubble flow in an expanding FLRW universe will slowly evolve—on a timescale comparable to the Hubble time. In a previous article, three of the current authors performed a cosmographic analysis of the redshift drift in an FLRW universe, temporarily putting aside the issue of dynamics (the Friedmann equations). In the current article, we add dynamics while still remaining within the framework of an exact FLRW universe. We developed a suitable generic matter model and applied it to both standard FLRW and various dark energy models. Furthermore, we present an analysis of the utility of alternative cosmographic variables to describe the redshift drift data. [ABSTRACT FROM AUTHOR]

A recent JRASC paper (Brissenden 2020) demonstrated that a kinematic doppler interpretation of cosmological redshift can match Type 1a supernova measurements without expanding space or dark energy. Tis result is reviewed, and the omission of gravitational redshift, implications for general relativity, and the relevance of Milne cosmology are discussed. A new cosmological model is described where radius r replaces coordinate time-based ct. With this model, expansion of the Universe is associated with a kinematic increase in radius, and not the Friedmann-Robertson-Walker expanding space scale factor, a(t). A new metric tensor is proposed, to replace the FRW metric of standard cosmological theory. [ABSTRACT FROM AUTHOR]

The H 0 tension stands as a prominent challenge in cosmology, serving as a primary driver for exploring alternative models of dark energy. Another tension arises from measurements of the S 8 parameter, which is characterize the amplitude of matter fluctuations in the universe. In this study, we address the alleviation of both the Hubble tension and S 8 tension by incorporating Kaniadakis horizon entropy. We investigate two scenarios to explore the impact of this entropy on cosmological parameters. In the first scenario, utilizing modified Friedmann equations through Kaniadakis entropy, we estimate the values of H 0 and S 8 . In the subsequent scenario, we introduce the neutrino term and assess its effect on mitigating the Hubble and S 8 tensions. Our findings reveal that when considering the first scenario, the results closely align with Planck's 2018 outcomes for Hubble and S 8 tensions. Moreover, with the inclusion of neutrinos, these tensions are alleviated to approximately 2 σ , and the S 8 value is in full agreement with the results from the KiDS and DES survey. Furthermore, we impose a constraint on the parameter K in each scenario. Our analysis yields K = 0.12 ± 0.41 for Kaniadakis entropy without neutrinos and K = 0.39 ± 0.4 for the combined dataset considering Kaniadakis entropy in the presence of neutrinos. We demonstrate that the value of K may be affected by neutrino mass, which can cause energy transfer between different parts of the universe and alter the Hubble parameter value. [ABSTRACT FROM AUTHOR]

In this paper, the basic Einstein–Hilbert cosmological model is extended by adding a new functional F (G , T μ ν T μ ν) in the fundamental action, encoding specific geometrical effects due to a nontrivial coupling with the Gauss–Bonnet invariant (G), and the energy–momentum squared term ( T μ ν T μ ν ). After obtaining the corresponding gravitational field equations for the specific decomposition where F (G , T μ ν T μ ν) = f (G) + g (T μ ν T μ ν) , we have explored the physical features of the cosmological model by considering the linear stability theory, an important analytical tool in the cosmological theory which can reveal the dynamical characteristics of the phase space. The analytical exploration of the corresponding phase space structure revealed that the present model can represent a viable dark energy model, with various stationary points where the effective equation of state corresponds to a de-Sitter epoch, possible explaining the early and late time acceleration of the Universe. [ABSTRACT FROM AUTHOR]

First, we review the solutions of a complex-valued scalar field, termed scalar clouds, with and without electric charge, when coupled to a rotating Kerr–Newman (electrically charged) or Kerr (neutral) black hole (BH), respectively. To this aim, we determine the conditions and parameters that characterize the existence of solutions that represent bound states, with an energy-momentum tensor that respect the symmetries of the underlying spacetimes, even if the backreaction of the field is not taken into account at this stage. In particular, we show that in the extremal Kerr scenario the cloud solutions exist only when the mass of the BH satisfies certain bounds, which are obtained by analyzing an effective potential associated with the radial dependency of the scalar clouds that leads to a Schrödinger-like equation. Second, when the backreaction of the field in the spacetime is taken into account, we present a family of stationary, axisymmetric and asymptotically flat solutions of the Einstein–Klein–Gordon system that represent genuine rotating hairy black holes (RHBHs) and provide different values of some global quantities associated with them, such as the Komar mass and the Komar angular momentum. We also compute RHBH solutions with nodes in the radial part of the scalar field and also for a higher azimuthal number m. [ABSTRACT FROM AUTHOR]

This paper explores the fundamental cosmological principle, with a specific focus on the homogeneity and isotropy assumptions inherent in the Friedmann model that underpins the standard model. We propose a modified redshift model that is based on the spatial distribution of luminous matter, examining three key astronomical quantities: light intensity, number density, and the redshift of galaxies. Our analysis suggests that the model can account for cosmic accelerated expansion without the need for dark energy in the equations. Both simulations and analytical solutions reveal a unique pattern in the formation and evolution of cosmic structures, particularly in galaxy formation. This pattern shows a significant burst of activity between redshifts 0 < z < 0.4, which then progresses rapidly until approximately z ≈ 0.9, indicating that the majority of cosmic structures were formed during this period. Subsequently, the process slows down considerably, reaching a nearly constant rate until around z ≈ 1.6, after which a gradual decline begins. We also observe a distinctive redshift transition around z ≈ 0.9 before the onset of dark-matter-induced accelerated expansion. This transition is directly related to the matter density and is dependent on the geometry of the universe. The model's ability to explain cosmic acceleration without requiring fine tuning of the cosmological constant highlights its novelty, providing a fresh perspective on the dynamic evolution of the universe. [ABSTRACT FROM AUTHOR]

By restricting ω eff = − 1 in this study, we rebuild a f (T) gravity function from a Λ CDM model. The equation for obtaining the f (T) function is f (T) = 1 2 T − 2 α (− T) 1 2 − β , where α and β are positive constants. A flat FLRW space-time metric has been taken into account, and modified field equations for the Hubble function and scaling factor have been solved. With two observational datasets, H (z) and SNe Ia data, we placed observational constraints on the Hubble function and apparent magnitude m (z) and we were able to determine the model parameters with the best match. These numbers have been used to analyze a number of cosmic phenomena occurring in the expanding cosmos. We have discovered a Λ model-closed transit phase decelerating to accelerating universe model. [ABSTRACT FROM AUTHOR]

This study investigates the cosmic bulk flow through an analysis of luminosity distance variations in a perturbed Friedmann universe governed by f (R) gravity. The Hubble parameter, derived from perturbed Friedmann equations capturing intrinsic temporal fluctuations, is crucial. Redshift tomography is used to analyse observational data from the Pantheon catalogue from 0.015 to z < 2.3. Our objective is to constrain the cosmic bulk flow's direction and magnitude within this redshift range. At low redshifts (z < 0.06), the predominant bulk flow aligns with the dominating supercluster in the corresponding range, maintaining a relatively constant magnitude, consistent with Lambda cold dark matter (ΛCDM) model predictions. A shift towards (l, b) = (290 ± 21, 15 ± 20) with |$v_{\mathrm{bulk}} = 774 \pm 83 \, \mathrm{km\, s}^{-1}$| occurs between 0.06 < z < 0.1, coinciding with the cosmic microwave background dipole. For 0.1 < z < 0.2, the bulk flow shifts to (l, b) = (270 ± 21, 25 ± 20) with |$v_{\mathrm{bulk}} = 903 \pm 102 \, \mathrm{km\, s}^{-1}$|⁠ , supporting Kashlinsky et al.'s result. Beyond z > 0.2, the bulk flow's magnitude exceeds |$1000 \, \mathrm{km\, s}^{-1}$|⁠ , deviating from ΛCDM model expectations. Our findings suggest that matter density oscillations under f (R) gravity exhibit ΛCDM model properties at low redshifts. However, the microwave background anisotropy shows noticeable fluctuations at higher redshifts, validating prior findings of strong cosmic bulk flows at these scales. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of dark energy in cosmological scenarios by exploiting f (R ̄ , T ̄) gravity within the framework of a nonstandard theory, called K-essence theory, where R ̄ represents the Ricci scalar and T ̄ denotes the trace of the energy–momentum tensor associated with the K-essence geometry. The Dirac–Born–Infeld (DBI) nonstandard Lagrangian has been employed to generate the emergent gravity metric ( G ̄ μ ν) associated with the K-essence. This metric is distinct from the usual gravitational metric (g μ ν). It has been shown that under a flat Friedmann–Lemaître–Robertson–Walker (FLRW) background gravitational metric, the modified field equations and the Friedmann equations of the f (R ̄ , T ̄) gravity are distinct from the usual ones. In order to get the equation of state (EoS) parameter ω , we have solved the Friedmann equations by taking into account the function f (R ̄ , T ̄) ≡ f (R ̄) + λ T ̄ , where λ represents a parameter within the model. We have found a relationship between ω and time for different kinds of f (R ̄) by treating the kinetic energy of the K-essence scalar field ( ϕ ̇ 2 ) as the dark energy density which fluctuates with time. Surprisingly, this result meets the condition of the restriction on ϕ ̇ 2 . By presenting graphical representations of the EoS parameter with time, we show that our model is consistent with the data of SNIa + BAO + H (z) within a certain temporal interval. [ABSTRACT FROM AUTHOR]

The f(R, T) gravity models, for which R is the Ricci scalar and T is the trace of the energy–momentum tensor, elevate the degrees of freedom of the renowned f(R) theories, by making the Einstein field equations of the theory to also depend on T. While such a dependence can be motivated by quantum effects, the existence of imperfect or extra fluids, or even a cosmological "constant" which effectively depends on T, the formalism can truly surpass some deficiencies of f(R) gravity. As the f(R, T) function is arbitrary, several parametric models have been proposed ad hoc in the literature and posteriorly confronted with observational data. In the present article, we use gaussian process to construct an f (R , T) = R + f (T) model. To apply the gaussian process we use a series of measurements of the Hubble parameter. We then analytically obtain the functional form of the function. By construction, this form, which is novel in the literature, is well-adjusted to cosmological data. In addition, by extrapolating our reconstruction to redshift z = 0 , we were able to constrain the Hubble constant value to H 0 = 69.97 ± 4.13 km s - 1 Mpc - 1 with 5 % precision. Lastly, we encourage the application of the functional form herewith obtained to other current problems of observational cosmology and astrophysics, such as the rotation curves of galaxies. [ABSTRACT FROM AUTHOR]

In this work, we study the Kerr–Sen–de Sitter black hole (BH) in the Nariai limit where the event and cosmological horizon coincide. We show that the near-horizon Kerr–Sen–de Sitter black hole in Nariai limit is a fiber over AdS 2 with an appropriate coordinate transformation, instead of fiber over dS 2 . Hence, we can compute the associated central charge and CFT temperature by using the Kerr/CFT method. It is remarkably exhibited that through Cardy's growth of states, the Bekenstein–Hawking entropy on cosmological horizon is reproduced. Moreover, we show that the radial equation of the quantum scalar field in J- and Q-pictures on this charged rotating background in Nariai limit can be portrayed in quadratic Casimir operator form with S L (2 , R) × S L (2 , R) isometry. We also compute the corresponding thermodynamic quantities from CFT to find the absorption cross-section and real-time correlator in J-picture. In Q-picture, we do not find a well-defined CFT description. We then extend the study of quantum scalar field in Nariai limit for Kerr–Newman–dS black hole solution and show that the hidden conformal symmetry on this black hole's background in J- and Q-pictures is well-defined. [ABSTRACT FROM AUTHOR]

The Hubble tension is analyzed in the framework of quantum cosmological approach. It is found that there arises a new summand in the expression for the total energy density stipulated by the quantum Bohm potential. This additional energy density acts similarly to a stiff matter component, modifying the expansion history of the early universe and decaying with scale factor a as a - 6 , faster than radiation, in late universe. Taking account of this matter-energy component of quantum nature can, in principle, eliminate a discrepancy between the direct late time model-independent measurements of the Hubble constant and its indirect model dependent estimates. The considered model allows one to extend the standard cosmology to quantum sector. [ABSTRACT FROM AUTHOR]

Thermodynamics of non-flat Amended Friedmann–Robertson–Walker (AFRW) universe with cosmological constant as thermodynamic pressure is studied. The unified first law of thermodynamics, the Clausius relation and the gravity equations yield entropy on the dynamic apparent horizon. Temperature, volume, pressure, enthalpy, Gibb's free energy and Helmholtz's free energies, and specific heat capacity with constant pressure of the universe are calculated in terms of surface area of dynamic apparent horizon. The study shows a non-negative Joule–Thomson coefficient, indicating the cooling nature of the AFRW universe. Inversion pressure and inversion temperature are expressed in terms of the surface area of the apparent horizon. Finally, the thermodynamical AFRW universe is considered as a heat engine. Work done for the Carnot engine is derived with maximum efficiency, and a new engine is also considered for which the work done, and its efficiency are calculated for AFRW universe. [ABSTRACT FROM AUTHOR]

In this paper, generalized Friedmann–Robertson–Walker universe for Strange Quark Matter (SQM) and Normal Matter (NM) coupled with Domain Wall (DW) in form perfect fluid have been investigated in f (R , T) modified theory. f (R , T) function has been assumed as f (R , T) = R + μ T and Modified Field Equations (MEFEs) have been attained. The MEFEs of the constructed model do not allow solutions of open and closed FRW universe. Obtained modified field equations of higher dimensional flat FRW universe have been solved by using Linearly Varying Deceleration Parameter (LVDP) suggested by Akarsu and Dereli [Int. J. Theor. Phys. 51, 612 (2012)]. Pressure and energy density of the matter distributions for the Linearly Expansion Model (LEM) and Constant Expansion Model (CEM) have been attained as decreasing values by the cosmic time t and constant μ in f (R , T) gravity. But for the Exponential Expansion Model (XEM), these quantities have been obtained as time-independent. It is found out that the domain wall behaves like invisible matter when s 1 = 0 due to negative domain wall tension ( σ w LSQM = − B c ) for SQM with DW of LEM. Strange quark matters for LDW and CDW models behave like cold dark matter when s 1 = 0 and s 3 = 0 , respectively. One can say that SQM with DW for LEM and CEM may cause the expansion of the universe in these special situations. Also, solutions of XEM have shown that domain wall matter behaves like stiff matter when μ = 2 0 π. All solutions of the constructed model in f (R , T) theory have been reduced to General Relativity (GR) theory solutions by assuming μ = 0. Finally, all solutions obtained have been discussed in detail. [ABSTRACT FROM AUTHOR]

Combining cosmological probes has consolidated the standard cosmological model with per cent precision, but some tensions have recently emerged when certain parameters are estimated from the local or primordial Universe. The origin of this behaviour is still under debate; however, it is crucial to study as many probes as possible to cross-check the results with independent methods and provide additional pieces of information to the cosmological puzzle. In this work, by combining several late-Universe probes (0 < z < 10), namely, Type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, and gamma-ray bursts, we aim to derive cosmological constraints independently of local or early-Universe anchors. To test the standard cosmological model and its various extensions, considering an evolving dark energy equation of state and the curvature as a free parameter, we analyse each probe individually and all their possible permutations. Assuming a flat Lambda cold dark matter (ΛCDM) model, the full combination of probes provides |$H_0=67.2^{+3.4}_{-3.2}$| km s−1 Mpc−1 and Ωm = 0.325 ± 0.015 [68 per cent confidence level (C.L.)]. Considering a flat w CDM model, we measure |$w_0=-0.91^{+0.07}_{-0.08}$| (68 per cent C.L.), while by relaxing the flatness assumption (ΛCDM model, 95 per cent C.L.) we obtain |$\Omega _k=0.125^{+0.167}_{-0.165}$|⁠. Finally, we analytically characterize the degeneracy directions and the relative orientation of the probes' contours. By calculating the figure-of-merit, we quantify the synergies among independent methods, estimate the constraining power of each probe, and identify which provides the best contribution to the inference process. Pending the new cosmological surveys, this study confirms the exigency for new emerging probes in the landscape of modern cosmology. [ABSTRACT FROM AUTHOR]

Considering the condition on conservation of energy–momentum tensor (EMT), we study late time cosmological solutions in the context of f (R , T) = R + α T n gravity (where α and n are constants) in a flat Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime. The present model discusses the case of a barotropic perfect fluid as the matter content of the Universe, along with the case when dissipative effects are taken into account. Briefly, assuming a single perfect fluid, we find that the mentioned model is not capable of presenting an observationally consistent picture of the late time accelerated expansion of the Universe; nevertheless, the model leads to admissible solutions when the bulk viscosity is included. In this regard, a consistent setting is found considering the Eckart, Truncated and Full Israel–Stewart theories which determine the behavior of bulk viscosity. In the presence of bulk viscosity, the behavior of the deceleration parameter (DP) shows that the underlying model can describe an acceptable evolution even if the isotropic pressure of matter content of the Universe is negligible. [ABSTRACT FROM AUTHOR]

In this paper, F (ν) cosmology is proposed for the accelerating universe with asymptotic de Sitter expansion in terms of Hankel function index ν. To some extent, both the initial expansion during early inflation and the current accelerated expansion can be studied with a vacuum cosmic fluid, i.e. Λ in the pure de Sitter phase. Observational data further support the notion of a quasi-vacuum fluid, rather than a pure vacuum, contributing to the quasi-de Sitter acceleration in both the early and late universe. By examining the asymptotic expansion of the Henkel function as an approximate solution of the Mukhanov–Sasaki equation, we seek a more detailed study of quasi-de Sitter solutions in cosmology containing vacuum-like fluid. [ABSTRACT FROM AUTHOR]

General relativity has been the dominant paradigm theory of gravity for the last century, it manages to explain a plethora of astronomical and cosmological observations with high accuracy. A major challenge faced by general relativity is, that it predicts a singularity as the beginning of our universe. In this paper, we shall explore a well-known idea in the literature that of the emergent universe and its viability according to Planck 2018 data and BBN constraints. [ABSTRACT FROM AUTHOR]

We study the intermediate tachyon inflation in an anisotropic background. By using the Friedmann equations obtained in the anisotropic geometry, we obtain the slow-roll parameters in the tachyon model. The presence of the anisotropic effects in the slow-roll parameters changes the perturbation parameters in our setup which may change its observational viability. To check this, we perform a numerical analysis and test the results with Planck2018 TT, TE, EE +lowE+lensing+BK14(18)+BAO data. We show that the intermediate anisotropic inflation in some ranges of the anisotropic and intermediate parameters is observationally viable. We also show that the equilateral amplitude of the non-gaussianity in our model is of the order of 10 - 2 - 10 - 1 . By studying the reheating process in our setup, we find that it is possible to have instantaneous reheating in this model. We also find that the temperature during the reheating in our setup is consistent with Big-Bang nucleosynthesis. [ABSTRACT FROM AUTHOR]

We study the inflationary scenario in the Tsallis entropy-based cosmology. The Friedmann equations in this setup can be derived by using the first law of thermodynamics. To derive the relations of the power spectra of the scalar and tensor perturbations in this setup, we reconstruct an f(R) gravity model which is thermodynamically equivalent to our model in the slow-roll approximation. In this way, we find the inflationary observables, including the scalar spectral index and the tensor-to-scalar ratio in our scenario. Then, we investigate two different potentials in our scenario, including the quadratic potential and the potential associated with the natural inflation in which the inflaton is an axion or a pseudo-Nambu–Goldstone boson. We examine their observational viability in light of the Planck 2018 CMB data. We show that although the results of these potentials are in tension with the observations in the standard inflationary setting, their consistency with the observations can be significantly improved within the setup of the Tsallis entropy-based inflation. Moreover, we place constraints on the parameters of the considered inflationary models by using the current observational data. [ABSTRACT FROM AUTHOR]

This study examines Einstein's field equations in the context of general relativity, comparing five distinct methodologies: (a) vanishing complexity, (b) embedding class one or the Karmarkar condition, (c) conformally flat spacetime, (d) conformal killing symmetry, and (e) the Karmarkar scalar condition. The first four methods reveal a significant connection between two metric potentials, while the fifth method provides a coordinate-independent condition expressed in terms of structural scalars. The paper provides a comprehensive comparative analysis of a new exact solution derived by assuming a common metric function and solving the remaining metric functions through corresponding bridge equations to evaluate their effectiveness and validity. Critical parameters such as thermodynamic factors, causality conditions, stability, and mass function analysis are investigated. [ABSTRACT FROM AUTHOR]

We investigate the Teukolsky equation in horizon-penetrating coordinates to study the behavior of perturbation waves crossing the outer horizon. For this purpose, we use the null ingoing/outgoing Eddington–Finkelstein coordinates. The first derivative of the radial equation is a Fuchsian differential equation with an additional regular singularity to the ones the radial one has. The radial functions satisfy the physical boundary conditions without imposing any regularity conditions. We also observe that the Hertz-Weyl scalar equations preserve their angular and radial signatures in these coordinates. Using the angular equation, we construct the metric perturbation for a circularly orbiting perturber around a black hole in Kerr spacetime in a horizon-penetrating setting. Furthermore, we completed the missing metric pieces due to the mass M and angular momentum J perturbations. We also provide an explicit formula for the metric perturbation as a function of the radial part, its derivative, and the angular part of the solution to the Teukolsky equation. Finally, we discuss the importance of the extra singularity in the radial derivative for the convergence of the metric expansion. [ABSTRACT FROM AUTHOR]

In this paper, we study the Chaplygin gas equation in curvature-matter coupling gravity to describe the observed expansion of the universe. We consider the Chaplygin gas equation of state in terms of the energy density ρ and pressure p , by the relationship p = − A ρ and the curvature-matter coupling gravity as f (R , T) , where A is a positive constant, R and T denote, respectively, the Ricci scalar and the trace of energy–momentum tensor. Considering the gravitational lagrangian in the form f (R , T) = R + h (T) , where we used two forms of h (T) and by assuming a perfect fluid as matter source, we determined through the modified Friedmann equations, the corresponding energy and pressure for each model. By using the free parameters of our models, we performed the numerical results of the energy conditions to study its viability. Furthermore, we have derived some cosmological parameters like deceleration parameter and statefinder parameters and graphically investigated the nature of these parameters in Chaplygin gas model. [ABSTRACT FROM AUTHOR]

Recently, the scalar–tensor representation of f (R, T) gravity was used to explore gravitationally induced particle production/annihilation. Using the framework of irreversible thermodynamics of open systems in the presence of matter creation/annihilation, the physical and cosmological consequences of this setup were investigated in detail. In this paper, we test observationally the scalar–tensor representation of f (R, T) gravity in the context of the aforementioned framework, using the Hubble and Pantheon + measurements. The best fit parameters are obtained by solving numerically the modified Friedmann equations of two distinct cosmological models in scalar–tensor f (R, T) gravity, corresponding to two different choices of the potential, and by performing a Markov Chain Monte Carlo analysis. The best parameters are used to compute the cosmographic parameters, that is, the deceleration, the jerk, and the snap parameters. Using the output resulting from the Markov Chain Monte Carlo analysis, the cosmological evolution of the creation pressure and of the matter creation rates are presented for both models. To figure out the statistical significance of the studied scalar–tensor f (R, T) gravity, the Bayesian and the corrected Akaike information criteria are used. The latter indicates that the first considered model in scalar–tensor f (R, T) gravity is statistically better than ΛCDM, that is, it is more favoured by observations. Besides, a continuous particle creation process is present in Model 1. Alternatively, for large redshifts, in Model 2 the particle creation rate may become negative, thus indicating the presence of particle annihilation processes. However, both models lead to an accelerating expansion of the universe at late times, with a deceleration parameter equivalent to that of the ΛCDM model. [ABSTRACT FROM AUTHOR]

Dark energy is frequently modelled as an additional dynamical scalar field component in the Universe, referred to as 'quintessence', which drives the late-time acceleration. Furthermore, the quintessence field may be coupled to dark matter and/or baryons, leading to a fifth force. In this paper, we explore the consequences for non-linear cosmological structure formation arising from a momentum coupling between the quintessence field and dark matter only. The coupling leads to a modified Euler equation, which we implement in an N -body cosmological simulation. We then analyse the effects of the coupling on the non-linear power spectrum and the properties of the dark matter haloes. We find that, for certain quintessence potentials, a positive coupling can lead to significantly reduced structure on small scales and somewhat enhanced structure on large scales, as well as reduced halo density profiles and increased velocity dispersions. [ABSTRACT FROM AUTHOR]

Our proposed cosmological framework, which is based on fractional quantum cosmology, aims to address the issue of synchronicity in the age of the universe. To achieve this, we have developed a new fractional Λ CDM cosmological model. We obtained the necessary formalism by obtaining the fractional Hamiltonian constraint in a general minisuperspace. This formalism has allowed us to derive the fractional Friedmann and Raychaudhuri equations for a homogeneous and isotropic cosmology. Unlike the traditional de Sitter phase, our model exhibits a power-law accelerated expansion in the late-time universe, when vacuum energy becomes dominant. By fitting the model's parameters to cosmological observations, we determined that the fractional parameter of Lévy equals α = 1.986 . Additionally, we have calculated the age of the universe to be 13.8196 Gyr. Furthermore, we have found that the ratio of the age to Hubble time from the present epoch to the distant future is finite and confined within the interval 0.9858 ≤ H t < 95.238 . [ABSTRACT FROM AUTHOR]

With a Nobel Prize for Physics widely viewed as only given for 'settled' science, the award then essentially accepts the validity of universal nonlocality. Other key discoveries and insights in recent years are also progressively pointing to the appearance of our Universe, its energy-matter and space-time, as not being foundational but emerging from deeper, discarnate realms of causation. as digitized and meaningful, in-formation, its manifestation pixelated at the so-named Planck scale of existence. Extending from studies of black holes to the entire Universe, a growing number of cosmologists have also developed the so-named holographic principle, to model the four-dimensional appearance of our Universe (three dimensions of space and one of time) as a holographic projection of its two- dimensional boundary. In framing the emergent cosmology of a nonlocally unified, meaningfully in-formed and holographically manifested Universe, an expansion of the three universal Laws of Thermodynamics to three Laws of Information, or Infodynamics also points the way to reconciling Quantum Theory that describes energy-matter and Relativity Theory that describes space-time and offers too an understanding of how the lifecycle of our Universe flows from its first moment until its last. Treating gravity as an emergent consequence of the in-formational and holographic structure of space- time and describing it as the consequence of the intropy associated with the positions in space-time of massive bodies, also points to the findings of the loss of phenotype identity in zero gravity and the role between gravity and cellular identity and the emergence of symbiogenesis. [ABSTRACT FROM AUTHOR]

Symmetric Teleparallel Gravity allows for the reformulation of gravity in the form of nonmetricity by vanishing the contorsion term in the generic affine connection. Our focus is on investigating a recently proposed extension of this theory in which the Lagrangian has the form f(Q, C) by incorporating the boundary term C. In this work, we first use a reconstruction approach in f(Q, C) gravity that might admit the Λ CDM expansion history. Furthermore, we perform a novel approach for cosmological reconstruction of f(Q, C) gravity in terms of e-folding, and it shows how any FLRW cosmology can arise from a specific f(Q, C) gravity. A variety of instances are provided using this approach in which f(Q, C) gravity is reconstructed to yield the well-known cosmic evolution: Λ CDM era, acceleration/deceleration era which is equivalent to the presence of phantom and non-phantom matter, late-time acceleration with the crossing of phantom-divide line and transient phantom era. [ABSTRACT FROM AUTHOR]

We investigate the application of an equation of state that incorporates corrections derived from the Snyder model (and the Generalized Uncertainty Principle) to describe the behaviour of matter in a low-mass star. Remarkably, the resulting equations exhibit striking similarities to those arising from modified Einstein gravity theories. By modeling matter with realistic considerations, we are able to more effectively constrain the theory parameters, surpassing the limitations of existing astrophysical bounds. The bound we obtain is β 0 ≤ 4.5 × 10 47 . We underline the significance of realistic matter modeling in order to enhance our understanding of effects arising in quantum gravity phenomenology and implications of quantum gravitational corrections in astrophysical systems. [ABSTRACT FROM AUTHOR]

We start with the cosmic Friedmann equations, where we adopt a novel perspective rooted in a Lagrangian formulation, grounded in Newtonian mechanics and the first law of thermodynamics. Our investigation operates under the assumption that the universe is populated by either a perfect fluid or a scalar field. By elucidating the intricate interplay between the Lagrangian formulation and the cosmic Friedmann equations, we uncover the fundamental principles governing the universe’s dynamics within the framework of these elemental constituents. In our concluding endeavor, we embark on the task of harmonizing the classical equations—namely, the conservation, Euler, and Poisson equations—with the principles of General Relativity. This undertaking seeks to extend these foundational equations to encompass the gravitational effects delineated by General Relativity, thus providing a comprehensive framework for understanding the behavior of matter and spacetime in the cosmic context.

The constraint of the deceleration parameter associated with dark energy stands as one of the most captivating subjects in the present cosmological framework. This study centers on the parametric reconstruction of the deceleration parameter in a flat Friedmann–Robertson–Walker (FLRW) Universe that encompasses radiation, dark energy, and pressure-less dark matter. In this context, we thoroughly investigate a highly motivated parametrization of q(z), which offers an evolutionary scenario from deceleration to the acceleration phase of the Universe. The crucial task of estimating the parametrization of the Hubble parameter is accomplished through its incorporation into the Friedmann equation. The free parameters are subsequently constrained utilizing a comprehensive set of observational data, including H(z), type Ia supernovae (SNIa), Baryon Acoustic Oscillation (BAO), Gamma Ray Burst (GRB), and Quasar (Q) measurements. Implementing the Markov Chain Monte Carlo (MCMC) technique and the H(z) + BAO + SNIa + GRB + Q dataset, we derive the best-fit values for the model parameters. Consequently, we provide a graphical analysis of the cosmographic parameters such as deceleration, jerk, and snap parameters by applying these optimized model parameter values. Finally, we compare our results with those of the standard Λ CDM paradigm to evaluate the viability of our proposed models. [ABSTRACT FROM AUTHOR]

We study the properties of evolving wormholes able to exist in a closed Friedmann dust-filled universe and described by a particular branch of the well-known Lemaître–Tolman–Bondi solution to the Einstein equations and its generalization with a nonzero cosmological constant and an electromagnetic field. Most of the results are obtained with pure dust solutions. It is shown, in particular, that the lifetime of wormhole throats is much shorter than that of the whole wormhole region in the universe (which coincides with the lifetime of the universe as a whole), and that the density of matter near the boundary of the wormhole region is a few times smaller than the mean density of matter in the universe. Explicit examples of wormhole solutions and the corresponding numerical estimates are presented. The traversability of the wormhole under study is shown by a numerical analysis of radial null geodesics. [ABSTRACT FROM AUTHOR]

The recent results from the Pulsar Timing Array (PTA) collaborations show the first evidence for the detection of a stochastic background of gravitational waves at the nHz frequencies. This discovery has profound implications for the physics of both the late and the early Universe. In fact, together with the interpretation in terms of supermassive black hole binaries, many sources in the early Universe can provide viable explanations as well. In this paper, we study the gravitational wave background sourced by a network of axion-like-particle (ALP) domain walls at temperatures around the QCD crossover, where the QCD-induced potential provides the necessary bias to annihilate the network. Remarkably, this implies a peak amplitude at frequencies around the sensitivity range of PTAs. We extend previous analysis by taking into account the unavoidable friction on the network stemming from the topological coupling of the ALP to QCD in terms of gluon and pion reflection off the domain walls at high and low temperatures, respectively. We identify the regions of parameter space where the network annihilates in the scaling regime ensuring compatibility with the PTA results, as well as those where friction can be important and a more detailed study around the QCD crossover is required. [ABSTRACT FROM AUTHOR]