Dark fluid

We investigate a scalar field modulated by a spiral-time function as a candidate for a unified dark component, dynamically interpolating between Dark Matter (DM) and Dark Energy (DE). The model proposes that oscillatory regimes reproduce pressureless DM, while slowroll regimes mimic DE with negative pressure. The formulation naturally recovers ΛCDM in the limit of vanishing modulation and provides testable predictions: time-varying w(z), low-ℓ cosmic microwave background (CMB) anomalies, and modified weak lensing spectra. These features make the framework falsifiable with ongoing and upcoming surveys such as Planck, DESI, and Euclid.

The possibility that dark matter, whose existence is inferred from the study of the galactic rotation curves, and from the mass deficit in galaxy clusters, can be in a form of a Bose-Einstein Condensate, has been extensively investigated lately. In the present work, we consider a detailed analysis of the astrophysical properties of the Bose-Einstein Condensate dark matter halos that could provide clear observational signatures that help discriminate between different dark matter models. In the Bose-Einstein condensation model dark matter can be described as a non-relativistic, gravitationally confined Newtonian gas, whose density and pressure are related by a polytropic equation of state with index n = 1. The mass and gravitational properties of the condensate halos are obtained in a systematic form, including the mean logarithmic slopes of the density and of the tangential velocity. The lensing properties of the condensate dark matter are investigated in detail. In particular, a general analytical formula for the surface density, an important quantity that defines the lensing properties of a dark matter halos, is obtained in the form of series expansions. This enables arbitraryprecision calculations of the surface mass density, deflection angle, deflection potential, and of the magnification factor, thus giving the possibility of the comparison of the predicted lensing properties of the condensate dark matter halos with observations. The stability properties of the condensate halos are also investigated by using the scalar and the tensor virial theorems, respectively, and the virial perturbation equation for condensate dark matter halos is derived. As an application of the scalar virial theorem we consider the problem of the stability of a slowly rotating and slightly disturbed galactic dark matter halo. For such a halo the oscillations frequencies and the stability conditions are obtained in the linear approximation.

We investigate the interaction between dark energy and dark matter in the framework of irreversible thermodynamics of open systems with matter creation/annihilation. We consider dark energy and dark matter as an interacting two component (scalar field and "ordinary" dark matter) cosmological fluid in a homogeneous spatially flat and isotropic Friedmann-Robertson-Walker (FRW) Universe. The thermodynamics of open systems as applied together with the gravitational field equations to the two component cosmological fluid leads to a generalisation of the elementary dark energy-dark mater interaction theory, in which the decay (creation) pressures are explicitly considered as parts of the cosmological fluid stress-energy tensor. Specific models describing coherently oscillating scalar waves, leading to a high particle production at the beginning of the oscillatory period, and models with a constant potential energy scalar field are considered. Furthermore, exact and numerical solutions of the gravitational field equations with dark energy-dark matter interaction are also obtained.

We study a minimal, testable mapping from horizon thermodynamics to FRW cosmology. Assuming only (i) Bekenstein-Hawking area capacity (one nat per 4 ℓ 2 P per minimal area element) and (ii) the apparent-horizon temperature, we treat the FRW apparent horizon as an information boundary register. Using dE = T dS (Landauer/Clausius), one nat at the horizon temperature contributes energy kBTH. This yields a homogeneous vacuum term with density ρ Λ = fsat ρc and hence Ω Λ = fsat. The fraction fsat is treated as an empirical parameter; Planck 2015/2018 imply fsat ≈ ln 2 ≃ 0.693. We then show that if the initial load is one bit per minimal patch, capacitylimited compaction implies fsat = ln 2. The framework leaves on-shell physics unchanged and is falsifiable: after equilibration w =-1 and Ω Λ shows no late-time evolution. Appendices give an equivalent Landauer-de Sitter check and a unit/dimension audit.

We study the phenomenology associated to non-minimally coupled dark matter. In particular, we consider the model where the non-minimal coupling arises from the formation of relativistic Bose-Einstein condensates in high density regions of dark matter . This non-minimal coupling is of Horndeski type and leads to a local modification of the speed of gravity with respect to the speed of light. Therefore we can constrain the model by using the joint detection of GW170817 and GRB170817A. We show that the constraints obtained in this way are quite tight, if the dark matter field oscillates freely, whereas they are substantially weakened, if the oscillations are damped by the non-minimal coupling.

We study the phenomenology associated to non-minimally coupled dark matter. In particular, we consider the model where the non-minimal coupling arises from the formation of relativistic Bose-Einstein condensates in high density regions of dark matter . This non-minimal coupling is of Horndeski type and leads to a local modification of the speed of gravity with respect to the speed of light. Therefore we can constrain the model by using the joint detection of GW170817 and GRB170817A. We show that the constraints obtained in this way are quite tight, if the dark matter field oscillates freely, whereas they are substantially weakened, if the oscillations are damped by the non-minimal coupling.

We investigate a scalar field modulated by a spiral-time function as a candidate for a unified dark component, dynamically interpolating between Dark Matter (DM) and Dark Energy (DE). The model proposes that oscillatory regimes reproduce pressureless DM, while slowroll regimes mimic DE with negative pressure. The formulation naturally recovers ΛCDM in the limit of vanishing modulation and provides testable predictions: time-varying w(z), low-ℓ cosmic microwave background (CMB) anomalies, and modified weak lensing spectra. These features make the framework falsifiable with ongoing and upcoming surveys such as Planck, DESI, and Euclid.

We propose an update of the ETCQ model (Elastic Cosmic Quantum Web), in which the gravitational response of baryons is modified by an elasticity factor bounded by the fine-structure constant α. This bound acts as a universal cap that limits the web's ability to store energy, ensuring a direct link between atomic physics and cosmological dynamics.

In this paper we study the accelerating expansion of the Universe by unifying dark matter and dark energy with an exotic fluid the so-called Chaplygin gas. We consider the cosmological background expansion of a universe model filled with a radiation-baryonic matterChaplygin gas fluid system and show that such a model can solve the dark matter and dark energy problems, at least at the level of the background expansion. We present the numerical results of the deceleration parameter and luminosity distance, and show that they correlate well with observational data.

This is the proposed introduction for your book, designed to be transparent, scientifically ethical, and reflective of our discussions about the ΔQ model's performance (e.g., 95% success on SPARC, 48 problematic galaxies, and the need for peer review). It's ready for Zenodo and sets the right tone for readers.

A method for deriving Friedmann-Robertson-Walker (FRW) solutions developed in Int. J. Mod. Phys. D5(1996)71-84, is generalized to account for models with non-minimal coupling between the dark energy and the dark matter. New quintessence and phantom (flat) FRW solutions are found. Their physical significance is discussed. Additionally, the aforementioned method is modified so that, "coincidence free" solutions can be readily derived. Besides, we review some aspects of the phantom barrier crossing. In this regard we present a model which is free from the coincidence problem and, at the same time, does the crossing of the phantom barrier ω = -1 at late time. Finally, we give additional comments on the non predictive properties of scalar field cosmological models with or without energy transfer.

This paper aims to introduce a new parameterisation for the coupling Q in interacting dark matter and dark energy models by connecting said models with the Continuous Tower of Scalar Fields model. Based upon the existence of a dark matter and a dark energy sectors in the Continuous Tower of Scalar Fields, a simplification is considered for the evolution of a single scalar field from the tower, validated in this paper. This allows for the results obtained with the Continuous Tower of Scalar Fields model to match those of an interacting dark matter -dark energy system, considering that the energy transferred from one fluid to the other is given by the energy of the scalar fields that start oscillating at a given time, rather than considering that the energy transference depends on properties of the whole fluids that are interacting.

This paper provides concrete evidence that the expanding and accelerating Universe mathematically expressed by dark energy is a purely mathematical abstraction. The energy loss of photons interacting with crystallized electrons in the intergalactic medium combined with the effect of cosmic dust on the travelling radiation predict supernovae dimming with a perfect fit to observational data. Accordingly, there is no need for any adjustment parameters and corrections. The outcome of this research plots the quantitative distance modulus predictions against redshift and compares them to the results obtained by the Pantheon+ inquiry. In this work frame, the SN-Ia distance modulus is rigorously provided by the sum of four main contributions: the distance in a nonexpanding Universe, the energy loss of the travelling photons to the recoil of the crystallized electrons, the conversion value of the distances and, last but not least, the dust extinction due to interactions between photon and dust particles in the intergalactic medium.

This paper provides concrete evidence that the expanding and accelerating Universe mathematically expressed by dark energy is a purely mathematical abstraction. The energy loss of photons interacting with crystallized electrons in the intergalactic medium combined with the effect of cosmic dust on the travelling radiation predict supernovae dimming with a perfect fit to observational data. Accordingly, there is no need for any adjustment parameters and corrections. The outcome of this research plots the quantitative distance modulus predictions against redshift and compares them to the results obtained by the Pantheon+ inquiry. In this work frame, the SN-Ia distance modulus is rigorously provided by the sum of four main contributions: the distance in a nonexpanding Universe, the energy loss of the travelling photons to the recoil of the crystallized electrons, the conversion value of the distances and, last but not least, the dust extinction due to interactions between photon and dust particles in the intergalactic medium.

This paper provides concrete evidence that the expanding and accelerating Universe mathematically expressed by dark energy is a purely mathematical abstraction. The energy loss of photons interacting with crystallized electrons in the intergalactic medium combined with the effect of cosmic dust on the travelling radiation predict supernovae dimming with a perfect fit to observational data. Accordingly, there is no need for any adjustment parameters and corrections. The outcome of this research plots the quantitative distance modulus predictions against redshift and compares them to the results obtained by the Pantheon+ inquiry. In this work frame, the SN-Ia distance modulus is rigorously provided by the sum of four main contributions: the distance in a non-expanding Universe, the energy loss of the travelling photons to the recoil of the crystallized electrons, the conversion value of the distances and, last but not least, the dust extinction due to interactions between photon and dust particles in the intergalactic medium.

This paper reexamines the redshift-distance relation of Type Ia supernovae (SN1a) using the Pantheon+SHOES dataset, comparing the standard ΛCDM model with a firstprinciples attenuation model based on Zwicky and Hubble's 1929 predictions. The attenuation model, defined as 𝑧 = 𝑒 𝛼𝐷-1 Where the linear attenuation coefficient α is the measured Hubble term 67 Km/s/Mpc and c light speed. Therefore, for a given measurement of redshift z, the corresponding distance is: 𝐷(𝑀𝑝𝑐) = 𝑙𝑛(1 + 𝑧) 𝛼 with H = 67 km/s/Mpc, achieves an R2 = 0.9829, rivaling the ΛCDM model's R2 = 0.9902. Despite ΛCDM's circularity from parameter-tuned modulus μ, the attenuation model's simplicity and lack of dark energy align with observed mature spiral galaxies at high z, challenging Big Bang assumptions.

The higher-dimensional Weyl curvature induces on the brane a new source of gravity. This Weyl fluid of geometrical origin (reducing in the spherically symmetric, static configuration to a dark radiation and dark pressure) modifies spacetime geometry around galaxies and has been shown to explain the flatness of galactic rotation curves. Independent observations for discerning between the Weyl fluid and other dark matter models are necessary. Gravitational lensing could provide such a test. Therefore we study null geodesics and weak gravitational lensing in the dark radiation dominated region of galaxies in a class of spherically symmetric braneworld metrics. We find that the lensing profile in the braneworld scenario is distinguishable from dark matter lensing, despite both the braneworld scenario and dark matter models fitting the rotation curve data. In particular, in the asymptotic regions, light deflection is 18% enhanced as compared to dark matter halo predictions. For a linear equation of state of the Weyl fluid, we further find a critical radius below which braneworld effects reduce, while above it they amplify light deflection. This is in contrast to any dark matter model, the addition of which always increases the deflection angle.

We present a framework for discussing the cosmology of dark energy and dark matter based on two scalar degrees of freedom. An effective field theory of cosmological perturbations is employed. A unitary gauge choice renders the dark energy field into the gravitational sector, for which we adopt a generic Lagrangian depending on three-dimensional geometrical scalar quantities arising in the ADM decomposition. We add to this dark-energy associated gravitational sector a scalar field φ and its kinetic energy X as dark matter variables. Compared to the single-field case, we find that there are additional conditions to obey in order to keep the equations of motion for linear cosmological perturbations at second order. For such a second-order multi-field theory we derive conditions under which ghosts and Laplacian instabilities of the scalar and tensor perturbations are absent. We apply our general results to models with dark energy emerging in the framework of the Horndeski theory and dark matter described by a k-essence Lagrangian P (φ, X). We derive the effective coupling between such an imperfect-fluid dark matter and the gravitational sector under the quasi-static approximation on sub-horizon scales. By considering the purely kinetic Lagrangian P (X) as a particular case, the formalism is verified to reproduce the gravitational coupling of a perfect-fluid dark matter.

We investigate the impact of the generalized uncertainty principle proposed by some approaches to quantum gravity such as string theory and doubly special relativity on the cosmology. Using generalized Poisson brackets, we obtain the modified Friedmann and Raychaudhuri equations and suggest a dynamical dark energy to explain the late-time acceleration of the universe. After considering the interaction between dark matter and dark energy, originated from the minimal length, we obtain the effective cosmological parameters and equation of state parameter for dark matter and dark energy. Finally, we show that the resulting model is equivalent to the Phantom and Tachyon fields.

The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300 deg2 of the celestial sphere in 12 optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k × 9.2k e2v detector with 10 $\rm {\mu m}$ pixels, resulting in a field of view of 2 deg2 with a plate scale of 0.55 arcsec pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30°, 8000 deg2) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/[OII], Ca H + K, H δ, G band, Mg b triplet, H α, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z &...

We discuss the possibility to implement a viscous cosmological model, attributing to the dark matter component a behaviour described by bulk viscosity. Since bulk viscosity implies negative pressure, this rises the possibility to unify the dark sector. At the same time, the presence of dissipative effects may alleviate the so called small scale problems in the $\Lambda$CDM model. While the unified viscous description for the dark sector does not lead to consistent results, the non-linear behaviour indeed improves the situation with respect to the standard cosmological model.

We study the evolution of the dark energy parameter within the scope of a spatially flat and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy. To obtain the deterministic solution we choose the scale factor a(t) = √ te t which yields a time dependent deceleration parameter (DP). In doing so we consider the case minimally coupled with dark energy to the perfect fluid as well as direct interaction with it.

In this paper we study the evolution of the dark energy parameter within the scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy by revisiting the recent results (Amirhashchi et al. in Chin. Phys. Lett. 28:039801, 2011a). To prevail the deterministic solution we select the scale factor a(t) = √ t n e t which generates a time-dependent deceleration parameter (DP), representing a model which generates a transition of the universe from the early decelerating phase to the recent accelerating phase. We consider the two cases of an interacting and non-interacting twofluid (barotropic and dark energy) scenario and obtained general results. The cosmic jerk parameter in our derived model is also found to be in good agreement with the recent data of astrophysical observations under the suitable condition. The physical aspects of the models and the stability of the corresponding solutions are also discussed.

The standard model of cosmology (ΛCDM) relies on the cosmological scale factor-a global metric expansion term applied uniformly across the universe-to interpret observational data such as redshift, distance, and cosmic structure. However, this reliance represents a self-referential mathematical assumption rather than an independently verified physical process. This paper argues that the global application of the scale factor is the most consequential conceptual blunder in cosmology, resulting in artificial inflation of the universe, misinterpretation of redshift, and cascading theoretical patchwork such as dark energy and inflation. We propose that what has been interpreted as expansion may instead be a recursive misapplication of an abstract scale to a physically fragmented and gravitationally bound cosmos.

In this manuscript, we present a generalization of the interacting holographic dark energy model using the viscous generalized Chaplygin gas. We also study the model by considering a dynamical Newton's constant G. Then we reconstruct the potential and the dynamics of the scalar field which describe the viscous Chaplygin cosmology.

In this dissertation, we looked at the cosmological constraints of some f(R)-modified gravity models, such as f(R) = βRn (our first toy model), f(R) = αR + βRn (our second toy model), and more realistic ones like the Starobinsky and Hu-Sawicki models. We used 236 intermediate-redshift and 123 low-redshift Supernovae Type 1A data obtained from the SDSS-II/SNLS3 Joint Light-curve Analysis (JLA), with absolute magnitudes, for the B-filter, found on the NASA Extragalactic Database (NED). We also developed a Markov Chain Monte-Carlo (MCMC) simulation to find the best-fitting luminosity distance function value for each combination of cosmological parameters, namely the matter density distribution Ωm and the Hubble uncertainty parameter h̄ (firstly for the ΛCDM model and then for the f(R)-gravity models). We then used the ΛCDM model results to constrain the priors for the f(R)-gravity models. We assumed a flat universe Ωk = 0 and a radiation density distribution Ωr that is negligible to si...

Using a recently proposed gauge invariant formulation of light-cone averaging, together with adapted "geodesic light-cone" coordinates, we show how an "induced backreaction" effect emerges, in general, from correlated fluctuations in the luminosity distance and covariant integration measure. Considering a realistic stochastic spectrum of inhomogeneities of primordial (inflationary) origin we find that both the induced backreaction on the luminosity-redshift relation and the dispersion are larger than naïvely expected. On the other hand the former, at least to leading order and in the linear perturbative regime, cannot account by itself for the observed effects of dark energy at largeredshifts. A full second-order calculation, or even better a reliable estimate of contributions from the non-linear regime, appears to be necessary before firm conclusions on the correct interpretation of the data can be drawn.

We consider a self-consistent system of Bianchi type-I (BI) gravitational field and a binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., p = ζ ε, with ζ ∈ [0, 1] whereas, the dark energy density is considered to be either the quintessence or the Chaplygin gas. Exact solutions to the corresponding Einstein equations are obtained.

This module proposes that the scalar field within the Helix-Light-Vortex (HLV) Theory, which is spiral-modulated by the time function, acts as either Dark Matter (DM) or Dark Energy (DE) depending on its dynamic regime. The form of Spiral Time and the field's potential determine whether the field behaves as pressureless (DM-like) or with negative pressure (DE-like). This interpretation allows for a unified explanation of both dark cosmic components within a topologically coherent spiral model, replacing static cosmological constants with time-modulated spiral states. The module outlines the physical consistency, mathematical formulations, and symbolic connections within the G HLV grammar, providing a new perspective on the nature of cosmic darkness.

This module proposes that the scalar field within the Helix-Light-Vortex (HLV) Theory, which is spiral-modulated by the time function, acts as either Dark Matter (DM) or Dark Energy (DE) depending on its dynamic regime. The form of Spiral Time and the field's potential determine whether the field behaves as pressureless (DM-like) or with negative pressure (DE-like). This interpretation allows for a unified explanation of both dark cosmic components within a topologically coherent spiral model, replacing static cosmological constants with time-modulated spiral states. The module outlines the physical consistency, mathematical formulations, and symbolic connections within the G HLV grammar, providing a new perspective on the nature of cosmic darkness.

Taking into account the experimental results of the HiRes and AUGER collaborations, the present status of bounds on Lorentz symmetry violation (LSV) patterns is discussed. Although significant constraints will emerge, a wide range of models and values of parameters will still be left open. Cosmological implications of allowed LSV patterns are discussed focusing on the origin of our Universe, the cosmological constant, dark matter and dark energy. Superbradyons (superluminal preons) may be the actual constituents of vacuum and of standard particles, and form equally a cosmological sea leading to new forms of dark matter and dark energy.

We introduce and study a model designed to simultaneously shed light on the mysteries connected with Baryogenesis, Dark Matter and Dark Energy. The model describes a self-interacting complex axion field whose imaginary part, a pseudo-scalar axion, couples to the instanton density of gauge fields including the hypermagnetic field. This coupling may give rise to baryogenesis in the early universe. After tracing out the gauge and matter degrees of freedom, a non-trivial effective potential for the angular component of the axion field is obtained. It is proposed that oscillations of this component around a minimum of its effective potential can be interpreted as Dark Matter. The absolute value of the axion field rolls slowly towards 0. At late times, it can give rise to Dark Energy.

After recalling some puzzles in cosmology and briefly reviewing the Friedmann-Lemaître cosmos a simple unified model of the "Dark Sector" is described. This model involves a scalar field and a pseudo-scalar axion field that give rise to Dark Energy in the form of "quintessence" and to "fuzzy" Dark Matter, respectively. Predictions of the model concerning the late-time evolution of the Universe and possible implications for the problem of the observed Matter-Antimatter Asymmetry in the Universe are sketched.

The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300 deg2 of the celestial sphere in 12 optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k × 9.2k e2v detector with 10 $\rm {\mu m}$ pixels, resulting in a field of view of 2 deg2 with a plate scale of 0.55 arcsec pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30°, 8000 deg2) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/[OII], Ca H + K, H δ, G band, Mg b triplet, H α, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z &...

We derive, using the spherical collapse model, a generalized Layzer-Irvine equation which can be used to describe the gravitational collapse of cold dark matter in a dark energy background. We show that the usual Layzer-Irvine equation is valid if the dark matter and the dark energy are minimally coupled to each other and the dark energy distribution is homogeneous, independently of its equation of state. We compute the corrections to the standard Layzer-Irvine equation which arise in the presence of dark energy inhomogeneities. We show that, in the case of a dark energy component with a constant equation of state parameter consistent with the latest observational constraints, these corrections are expected to be small, even if the dark energy has a negligible sound speed. However, we find that, in more general models, the impact of dark energy perturbations on the dynamics of clusters of galaxies, which will be constrained by ESA's Euclid mission with unprecedented precision, might be significant.

We study the holographic dark energy (HDE) model in generalized Brans-Dicke scenario with a non-minimal coupling between the scalar field and matter lagrangian namely Chameleon Brans Dicke (CBD) mechanism. In this study we consider the interacting and non-interacting cases for two different cutoffs. The physical quantities of the model such as, equation of state (EoS) parameter, deceleration parameter and the evolution equation of dimensionless parameter of dark energy are obtained. We shall show that this model can describe the dynamical evolution of fraction parameter of dark energy in all epochs. Also we find the EoS parameter can cross the phantom divide line by suitable choices of parameters without any mines kinetic energy term.

We present a novel theoretical framework in which the cosmological constant Λ is promoted from a fixed scalar to a dynamical thermodynamic variable emerging from the quantum microstructure of spacetime. By extending the Einstein-Hilbert action through a non-minimal coupling between spacetime curvature and vacuum entropy density 𝑠 vac (𝑥), we derive modified field equations of the form: 𝑅 𝜇𝜈-1 2 𝑅𝑔 𝜇𝜈 + Λ(𝑥)𝑔 𝜇𝜈 + Ξ 𝜇𝜈 = 8𝜋𝐺𝑇 𝜇𝜈 , where the local cosmological function is given by: Λ(𝑥) = Λ 0 + 𝛾 ∇ 𝛼 𝑆 𝛼 (𝑥), with 𝑆 𝛼 (𝑥) denoting the entropy current associated with vacuum fluctuations and 𝛾 ∈ R + a coupling parameter. The correction tensor Ξ 𝜇𝜈 incorporates the scalar field 𝜙(𝑥) responsible for modulating vacuum entropy via: Ξ 𝜇𝜈 = 𝛼 ∇ 𝜇 𝜙∇ 𝜈 𝜙-1 2 𝑔 𝜇𝜈 ∇ 𝛼 𝜙∇ 𝛼 𝜙 + 𝛽 𝜙 2 𝑅 𝜇𝜈. The resulting field equations yield a self-regulating cosmological dynamics, in which the evolution of Λ(𝑥) is governed by: □𝜙 + 𝑉 ′ (𝜙) = 𝛿 𝜕𝑠 vac 𝜕𝜙 , establishing a direct link between quantum entropy production and large-scale acceleration. This framework unifies the early inflationary phase and the current dark energy epoch under a common dynamical mechanism, and addresses the longstanding discrepancy between quantum vacuum energy predictions and observed Λ obs ∼ 10-122 𝑀 4 Pl. We conclude by deriving testable predictions for next-generation cosmological probes such as CMB-S4, Euclid, and JWST, and show how deviations from ΛCDM at 𝑧 > 1.5 may serve as critical empirical signatures. This approach also paves the way for embedding vacuum thermodynamics within a topologically-constrained quantum gravity framework.

We present a comprehensive theoretical and experimental framework for gravitational modulation using entropy-driven, prime-resonant electromagnetic fields. By embedding symbolic entropy gradients into the dynamics of prime-indexed harmonic oscillators, we demonstrate the emergence of effective curvature in spacetime. This curvature is derived from coherent resonance collapse processes and quantified via a modified gravitational field tensor. We simulate the symbolic curvature field, visualize particle geodesic trajectories, and propose experimental schematics for physical implementation. This framework suggests a novel paradigm for manipulating spacetime geometry through symbolic information dynamics.

This mathematical framework shows how gravity emerges as the harmonic influence of standing waves in the DE/DM fields. The wave's motion toward maximum amplitude creates the sensation of gravitational "pull," while its negative phase could correlate with anti-particle emergence, contributing to a deeper understanding of universal symmetry.

We consider a self-consistent system of Bianchi type-I (BI) gravitational field and a binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., p = ζ ε, with ζ ∈ [0, 1] whereas, the dark energy density is considered to be either the quintessence or the Chaplygin gas. Exact solutions to the corresponding Einstein equations are obtained.

At the present paper, Locally Rotationally Symmetric (LRS) Bianchi type-II cosmological model with interacting dark matter (DM) and holographic dark energy (DE) have been discussed. In order to obtain solutions of the field equations, it is assume that the shear scalar ( σ ) is proportional to expansion scalar ( θ ). To have a general description of holographic dark energy and dark matter, a phenomenological parameterization of dark energy in terms of its equation of state (EoS) has been taken. Statefinder diagnostic pair i.e. { } , r s is adopted to separate other existing dark energy models from this model. Here we discuss two models: when 1 2 n = , we obtain acyclic universe and the model converges into phantom region whereas when 3 2 n = , we get a expanding universe and the model converges into quintessence region. Some important geometrical and physical features regarding to this model have also been studied.

In this paper we consider a universe filled with barotropic dark matter and Ricci dark energy in Lyras geometry with varying Λ. We assume two different kinds of interactions between dark matter and dark energy. Then, by using numerical analysis, we investigate some cosmological parameters of the models such as equation of state, Hubble and deceleration parameters.

We explore a Gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling, it condensates to super-structures with cosmic voids similar to the current picture of the universe. With the help of the equation of state of dry foam (equivalently a fluid with voids in it) from fluid mechanics, it is possible to show that tension within these cosmic walls due to their binding interaction may cause an accelerated expansion in the absence of dark energy. Furthermore, we give a cosmological analysis of this scenario with a semi-phenomenological ansatz, where we use recent Type Ia supernova compilation.

We explore a gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling it condensates to super-structures with cosmic voids similar to current picture of the universe. With the help of the equation of state of dry foam (equivalently a fluid with voids in it) from fluid mechanics it is possible to show that tension within these cosmic walls due to their binding interaction may cause accelerated expansion in the absence of dark energy.

We explore a Gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling, it condensates to super-structures with cosmic voids similar to the current picture of the universe. With the help of the equation of state of dry foam (equivalently a fluid with voids in it) from fluid mechanics, it is possible to show that tension within these cosmic walls due to their binding interaction may cause an accelerated expansion in the absence of dark energy. Furthermore, we give a cosmological analysis of this scenario with a semi-phenomenological ansatz, where we use recent Type Ia supernova compilation.

We explore a gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling it condensates to super-structures with cosmic voids similar to current picture of the universe. With the help of the equation of state of dry foam (equivalently a fluid with voids in it) from fluid mechanics it is possible to show that tension within these cosmic walls due to their binding interaction may cause accelerated expansion in the absence of dark energy.

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IV. Summary and Conclusions of the Workshop by H J de Vega and N G Sanchez V. Live Minutes of the Workshop by Peter Biermann A. Observations of galaxies B. Our galaxy C. Clusters of galaxies D. Small galaxies E. Galaxies F. Simulations: Pure DM 1. DM with stars and gas. keV scale DM. G. DM with stars, gas, magnetic fields and cosmic rays H. The Bullet Cluster & ΛCDM. I. Theory: Phase space and surface gravity constraints J. Black holes, pulsar kick K. Decisive Observations to find the DM particle 1. Very high precision experiments? III. HIGHLIGHTS BY THE LECTURERS

Cosmological background observations cannot fix the dark energy equation of state, which is related to a degeneracy in the definition of the dark sector components. Here we show that this degeneracy can be broken at perturbation level by imposing two observational properties on dark matter. First, dark matter is defined as the clustering component we observe in large scale structures. This definition is meaningful only if dark energy is unperturbed, which is achieved if we additionally assume, as a second condition, that dark matter is cold, i.e. non-relativistic. As a consequence, dark energy models with equation-of-state parameter -1 ≤ ω < 0 are reduced to two observationally distinguishable classes with ω = -1, equally competitive when tested against observations. The first comprises the ΛCDM model with constant dark energy density. The second consists of interacting models with an energy flux from dark energy to dark matter.