Cold Dark Matter

They are also expected to be produced copiously in stellar interiors with energies as high as the thermal photons undergoing photon to axion conversion. In our sun the axion energy spectrum peaks at about 4.4 keV, extending up to 10 keV. CAST collected preliminary data in 2002 and data taking with its full capability will start in the beginning of 2003.

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.

This note presents a speculative analogy between the P vs NP problem in computer science and the Ground Potential Theory of cosmology. I argue that just as absolute potential (Φ) defines the upper bound of all physical processes, the complexity class NP may be viewed as a constant expanse of possibility, while P represents the observer's accumulated past knowledge. In this framework, P expands with time as potential falls, but NP remains fixed, a boundary condition that can never be exceeded. This analogy reframes the open question not as a matter of equality, but of containment and cosmological asymmetry.

In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger th...

In order to specify cosmologically motivated initial conditions for major galaxy mergers (mass ratios ≤ 4:1) that are supposed to explain the formation of elliptical galaxies we study the orbital parameters of major mergers of cold dark matter halos using a high-resolution cosmological simulation. Almost half of all encounters are nearly parabolic with eccentricities e ≈ 1 and no correlations between the halo spin planes or the orbital planes. The pericentric argument ω shows no correlation with the other orbital parameters and is distributed randomly. In addition we find that 50% of typical pericenter distances are larger than half the halo's virial radii which is much larger than typically assumed in numerical simulations of galaxy mergers. In contrast to the usual assumption made in semi-analytic models of galaxy formation the circularities of major mergers are found to be not randomly distributed but to peak around a value of ≈ 0.5. Additionally all results are independent of the minimum progenitor mass and major merger definitions (i.e. mass ratios ≤ 4:1; 3:1; 2:1).

We measure cosmological parameters using the three-dimensional power spectrum P (k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data. Our results are consistent with a "vanilla" flat adiabatic ΛCDM model without tilt (ns = 1), running tilt, tensor modes or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1σ constraints on the Hubble parameter from h ≈ 0.74 +0.18 -0.07 to h ≈ 0.70 +0.04 -0.03 , on the matter density from Ωm ≈ 0.25 ± 0.10 to Ωm ≈ 0.30 ± 0.04 (1σ) and on neutrino masses from < 11 eV to < 0.6 eV (95%). SDSS helps even more when dropping prior assumptions about curvature, neutrinos, tensor modes and the equation of state. Our results are in substantial agreement with the joint analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive consistency check with independent redshift survey data and analysis techniques. In this paper, we place particular emphasis on clarifying the physical origin of the constraints, i.e., what we do and do not know when using different data sets and prior assumptions. For instance, dropping the assumption that space is perfectly flat, the WMAP-only constraint on the measured age of the Universe tightens from t0 ≈ 16.3 +2.3 -1.8 Gyr to t0 ≈ 14.1 +1.0 -0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running tilt, neutrino mass and equation of state in the list of free parameters, many constraints are still quite weak, but future cosmological measurements from SDSS and other sources should allow these to be substantially tightened. -0.33 0.55 +0.47 -0.29 0.177 +0.082 -0.058 0.313 +0.097 -0.087 0.36 +0.17 -0.14 0.25 +0.10 -0.10 0.326 +0.093 -0.086 h 2 Ωm 0.128 +0.022 -0.021 0.132 +0.021 -0.028 0.123 +0.020 -0.018 0.144 +0.018 -0.016 0.143 +0.020 -0.019 0.140 +0.020 -0.018 0.153 +0.020 -0.018 h 0.48 +0.27 -0.12 0.50 +0.16 -0.13 0.84 +0.12 -0.10 0.674 +0.087 -0.049 0.63 +0.14 -0.10 0.74 +0.18 -0.07 0.684 +0.070 -0.045 τ 0.33 +0.17 -0.17 0.22 +0.34 -0.13 0.19 +0.13 -0.09 0.15 +0.18 -0.07 0.19 +0.18 -0.10 0.21 +0.24 -0.11 < 0.35 (95%) z ion 25.9

We present initial results for counts in cells statistics of the angular distribution of galaxies in early data from the Sloan Digital Sky Survey (SDSS). We analyze a rectangular stripe 2.5 • wide, covering approximately 160 sq. degrees, containing over 10 6 galaxies in the apparent magnitude range 18 < r ′ < 22, with

We measure the large-scale real-space power spectrum P (k) using luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement to sharpen constraints on cosmological parameters from the Wilkinson Microwave Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation method using Pseudo-Karhunen-Loève eigenmodes, producing uncorrelated minimum-variance measurements in 20 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.01 h/Mpc < k < 0.2 h/Mpc. Results from the LRG and main galaxy samples are consistent, with the former providing higher signal-to-noise. Our results are robust to omitting angular and radial density fluctuations and are consistent between different parts of the sky. They provide a striking confirmation of the predicted large-scale ΛCDM power spectrum. Combining only SDSS LRG and WMAP data places robust constraints on many cosmological parameters that complement prior analyses of multiple data sets. The LRGs provide independent cross-checks on Ωm and the baryon fraction in good agreement with WMAP. Within the context of flat ΛCDM models, our LRG measurements complement WMAP by sharpening the constraints on the matter density, the neutrino density and the tensor amplitude by about a factor of two, giving Ωm = 0.24±0.02 (1σ), mν ∼ < 0.9 eV (95%) and r < 0.3 (95%). Baryon oscillations are clearly detected and provide a robust measurement of the comoving distance to the median survey redshift z = 0.35 independent of curvature and dark energy properties. Within the ΛCDM framework, our power spectrum measurement improves the evidence for spatial flatness, sharpening the curvature constraint Ωtot = 1.05±0.05 from WMAP alone to Ωtot = 1.003 ± 0.010. Assuming Ωtot = 1, the equation of state parameter is constrained to w = -0.94 ± 0.09, indicating the potential for more ambitious future LRG measurements to provide precision tests of the nature of dark energy. All these constraints are essentially independent of scales k > 0.1h/Mpc and associated nonlinear complications, yet agree well with more aggressive published analyses where nonlinear modeling is crucial.

We present the ETCQ (Elasticity of the Quantum Cosmic Lattice), an effective law of gravity based on the universal rigidity of the quantum vacuum. In this framework, baryons do not exert direct Newtonian attraction, but inject energy into a quantum lattice that absorbs, saturates, and then expels energy as a diluted flux ∝ 1/R 2. Newtonian gravity emerges as an effective description of this accumulation-saturation-diffusion process. The same constants, fixed once on the SPARC HQ++ sample, reproduce galaxy rotation curves, satellite dynamics, Solar System orbits, strong-lens time delays, and the observed dark-energy density.

Many models have been studied that contain more than one species of dark matter and some of these couple the Cold Dark Matter (CDM) to a light scalar field. In doing this we introduce additional long range forces, which in turn can significantly affect our estimates of cosmological parameters if not properly accounted for. It is, therefore, important to study these models and their resulting cosmological implications. We present a model in which a fraction of the total cold dark matter density is coupled to a scalar field. We study the background and perturbation evolution and calculate the resulting Cosmic Microwave Background anisotropy spectra. The greater the fraction of dark matter coupled to the scalar field and the stronger the coupling strength, the greater the deviation of the background evolution from ΛCDM. Previous work, with a single coupled dark matter species, has found an upper limit on the coupling strength of order O(0.1). We find that with a coupling of this magnitude more than half the dark matter can be coupled to a scalar field without producing any significant deviations from ΛCDM.

The origin of the universe in a hot, dense state known as the Big Bang is a cornerstone of modern cosmology. However, the ultimate fate of the cosmos remains one of the most profound open questions in physics. This paper reviews the primary theoretical scenarios for the end of the universe, broadly categorized into linear (onetime) and cyclical models. We develop the mathematical framework underpinning these scenarios, starting from the Friedmann-Lemaître-Robertson-Walker (FLRW) metric and the Friedmann equations derived from Einstein's field equations. We analyze the critical role of the universe's energy density components-particularly dark energy, characterized by its equation of state parameter w. Linear fates, such as the "Big Freeze" (Heat Death) for w =-1 and the more speculative "Big Rip" for w <-1, are contrasted with cyclical models like the "Big Crunch" and "Big Bounce," which require specific conditions on cosmic geometry and energy density. We conclude by discussing the overwhelming observational evidence from Type Ia supernovae, the Cosmic Microwave Background (CMB), and Baryon Acoustic Oscillations (BAO), which strongly supports a flat, accelerating universe dominated by a cosmological constant (Λ). This evidence positions the Big Freeze as the most probable scenario, suggesting a linear, one-way trajectory for our universe.

This work presents a rigorous comparative analysis between the standard Λ-CDM model and an alternative model based on baryonic inertial acceleration with vacuum braking (corrected ΦΚ/Kb'), applied to galactic rotation velocities. Using real and complete data from the SPARC database (175 galaxies), we demonstrate that corrected ΦΚ/Kb' outperforms Λ-CDM in 99.4% of cases against raw Λ-CDM and 97.71% against optimized Λ-CDM NFW, with an average RMSE of 32.24 km/s versus 56.43 km/s for optimized Λ-CDM, representing a 1.750x improvement. This exceptional performance is achieved through the inertial braking coe icient α = 0.01180 applied without free adjustment per galaxy. Data, RMSE calculations, and comparisons are provided for complete falsifiable validation.

This study presents a comprehensive analysis of galaxy rotation curves from the SPARC database, aimed at uncovering systematic patterns in their shape and oscillations. We show that the observed oscillations are not random noise. Instead, they are statistically significant, reproducible features exhibiting clear spatial localization and correlation with morphological type. Three robust dynamical regimes—rising, flat, and declining—are identified. These regimes show weak correlation with internal galaxy parameters, suggesting a dominant role of the large-scale environment. Analysis of the radial acceleration profile $g_{\rm obs}(r)$ reveals systematic oscillations, especially in central regions. This challenges the interpretation of scatter in the Radial Acceleration Relation (RAR) as a purely baryonic effect. Our results establish an \textbf{empirical fact}: any complete theory of galactic dynamics must explain not only the average shape of the rotation curve but also its oscillatory structure. We propose that the shape of the rotation curve be viewed as a \textbf{dynamic imprint} of a galaxy’s position within the hierarchical structure of the Universe.

We present a revolutionary alternative to the Big Bang cosmological model based on Filament Theory principles. Instead of expansion from a singular point, we propose the Great Hot Fragmentation (GHF)-a process where an initially uniform, hot filament medium undergoes spontaneous fragmentation into the structured universe we observe today. This model naturally explains the cosmic microwave background as thermal radiation from the fragmentation process rather than a relic of primordial expansion. We derive the critical fragmentation temperature (2.725 K) from first principles and show how large-scale structure formation emerges from filament density fluctuations rather than dark matter gravitational clustering. The model predicts specific signatures in the CMB power spectrum, explains the horizon problem without inflation, and provides a natural mechanism for the observed homogeneity and isotropy of the universe. Our approach resolves several fundamental problems of standard cosmology while making testable predictions that distinguish it from the Big Bang paradigm.

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.

This document summarizes the procedure for testing the ETCQ theory (Elastic Trame Cosmological Quantum) on strong lensing systems. Objective: reproduce the observed time delays without dark matter, solely via the trame response (λs, µs, η) and a small chronon factor (λs). Main Equations: 1. Time delay: ∆tss = ((1+zs)/c) • D∆t [ φ(θs;β)-φ(θs;β) ] with φ(θ;β) = 0.5sθ-βs²-ψ(θ). 2. ETCQ surface density: Σ_ETCQ = (1/(1+µs)) Σ_b + (µs/(1+µs))(Σ_b * G_sK) Σ_eff = (1+λs) Σ_ETCQ, with sK = η Rs. 3. Group SIS: α_SIS(θ) = θ_E,grp (θ-θ_g)/sθ-θ_gs. 4. Chronon: ∆t → (1+λs) ∆t, with λs ≈ 0.01-0.03.

The redshift observed in astronomy is explained by optical forces on electrons and atoms present in the intergalactic medium. The forces occur as a result of momentum exchange between light and matter. This produces an exchange of energy where the intergalactic medium is heated and the radiation is redshifted. The spectra of different light rays interact in the intergalactic medium to produce a spectral transfer redshift. Two mechanisms are examined: the dipole force which acts on atoms, and the ponderomotive force which acts on electrons. The dipole force produces a redshift which is wavelength dependent and can be distinguished from a Doppler redshift. The ponderomotive force produces a redshift which is independent of the wavelength and mimics a Doppler redshift. Both forces arise from a stimulated emission process which preserves the direction of propagation of one of the two interacting photons, a necessary condition to avoid blurring of images. This property distinguishes the spectral transfer redshift from all other redshift mechanisms proposed so far.

Cosmological inference with large galaxy surveys requires theoretical models that combine precise predictions for large-scale structure with robust and flexible galaxy formation modelling throughout a sufficiently large cosmic volume. Here, we introduce the millenniumTNG (MTNG) project which combines the hydrodynamical galaxy formation model of illustrisTNG with the large volume of the millennium simulation. Our largest hydrodynamic simulation, covering $(500 \, h^{-1}{\rm Mpc})^3 \simeq (740\, {\rm Mpc})^3$, is complemented by a suite of dark-matter-only simulations with up to 43203 dark matter particles (a mass resolution of $1.32\times 10^8 \, h^{-1}{\rm M}_\odot$) using the fixed-and-paired technique to reduce large-scale cosmic variance. The hydro simulation adds 43203 gas cells, achieving a baryonic mass resolution of $2\times 10^7 \, h^{-1}{\rm M}_\odot$. High time-resolution merger trees and direct light-cone outputs facilitate the construction of a new generation of semi-an...

We employed Mutual Information (MI) analysis to investigate the relationship between galaxy properties and the assembly history of their host dark matter (DM) haloes from the IllustrisTNG simulations. Focusing on central and satellite galaxies with stellar masses between 10 9 and 10 11. 5 h-1 M , we examined the correlation between halo assembly time and galaxy assembly time, specific star formation rate (sSFR), colour (gi), and galaxy formation efficiency F. Our results indicate a strong correlation between F and the halo assembly time for low-mass central galaxies, suggesting a co-evolutionary relationship. In contrast, sSFR and colour (gi) exhibit weaker correlations with halo assembly time, indicating that additional factors should influence these galaxy properties. Satellite galaxies show negligible correlation between their properties and halo assembly time, highlighting the impact of environmental processes on their evolution. We further extended our analysis to cluster observables, including the magnitude gap, the satellite richness, and the distances to the satellites. Although these cluster properties display weak o v erall correlations with halo assembly time, the richness consistently increases with stellar mass. This trend suggests that richness is more closely linked to formation history in more massive haloes, where satellite accretion dominates the growth of their host DM haloes. These findings establish F as a more sensitive indicator of halo assembly history than colour (gi), sSFR, or cluster observ ables, of fering ne w insights into the complex interplay between galaxy evolution and the hierarchical growth of their host dark matter haloes.

This theory proposes that dark matter is not only a mysterious component of the universe, but that astrophysical systems do not respond to its gravitational influence instantaneously. Instead, they undergo a period known as the Cosmic Adaptation Time. During this period, the gravitational response to dark matter is weak or absent, especially in dynamically stable systems. Dark matter becomes distinctly observable only when a major disturbance occurs (such as galaxy collisions or internal structural changes), which reactivates the gravitational response of dark matter. The theory is based on real astronomical observations and recent simulations, offering a new explanation for why some systems reveal dark matter while others do not.

Spiral galaxies exhibit flat or even rising rotation curves at large radii, a phenomenon widely attributed to massive halos of unseen dark matter. In this paper we show that such behavior arises naturally from flux attenuation in a transport-based revival of the Fatio-Le Sage process. Using the Beer-Lambert law of exponential attenuation applied to an isotropic momentum flux, the effective gravitational coupling becomes path-and geometry-dependent. In extended thin-disk systems such as spiral galaxies, cumulative in-plane attenuation suppresses the expected 1/r2 decline and produces flat rotation curves without recourse to dark matter. Numerical simulations with both structured and randomized stellar distributions reproduce measured profiles, including the upward "flip-up" observed in M33 and the averaged galaxy curves reported by NASA, with correlation coefficients exceeding 0.98. Because flux transport occurs at finite velocity c, the light-crossing time of large galactic disks (~10^5 years) introduces a rotational smearing of flux shadows, offering a causal explanation for velocity banding and spiral arm coherence. This analysis demonstrates one of the unique provisions of the transport model: spiral galaxy dynamics follow directly from the Fatio-Le Sage functional process when recast in modern radiation transport theory. The result highlights how causal substrate mechanics can replace ad hoc constructs, providing a testable alternative to dark matter in galactic dynamics.

Several models have been proposed to explain the cosmological constant as a consequence of alterations in the distance-redshift relation caused by the universe's inhomogeneities. We modelled the universe as a spherical galactic mass with a Gaussian radial profile, repeated at the nodes of a periodic 3D-lattice. The Einstein field density equation was solved to the first-order for the scalar field perturbation of the FLRW metric in the Newtonian gauge. The resulting metric solution is free of singularities. The diagonal Einstein spatial field equations exhibit only the subtraction of a constant second-order term. This term corresponds to the cosmological constant in the reference frame comoving with the galaxy positions. This geometrically derived cosmological constant accurately predicts the observed value using a realistic standard galaxy density profile and lattice periodicity, without introducing any additional adjustable parameters. Its value decreases exponentially as the galaxy size approaches the intergalactic distance. When the universe becomes homogeneous, the expansion rate equation reduces to that of the standard FLRW model. The model is Copernican in the sense that all galaxies share similar observational features. This approach opens a track of research to explain the origin of the cosmological constant within the framework of pure general relativity.

The equations for the specification of the curvature of space-time are inherent in the general theory of relativity (GTR). However, despite its enormous success, there are a number of difficulties with GTR. Standard GTR is mathematically very complex, and it predicts the formation of black hole singularities. Here we reformulate the equations for gravitation by mathematically defining the equations for the curvature of space-time. We then translate this curvature back into equations for the force of gravity. By using the original equations for calculating the curvature of space-time used in GTR, we can translate the equations for gravitation, back into equations for a modified force of Newtonian gravity. Using worked examples, we show that such an adaptation of gravity, gives results which technically give the same results as GTR, in the mass range of the solar system. At the same time, an analysis of the data shows that with binary pulsars, the new equations can give improved resul...

The so-called "Axis of Evil" -large-scale alignments of low multipoles in the cosmic microwave background (CMB) -has long posed a challenge to the cosmological principle. Its near-coincidence with the ecliptic plane suggests either a statistical artifact or an unrecognized physical mechanism. Here we propose, at the level of an idea, that this axis is not an intrinsic cosmic feature but a manifestation of a holographic projection principle: the apparent alignment emerges as an observer-dependent effect, analogous to the way holographic or concave optical masks appear to "follow" the observer's gaze. This interpretation resolves the paradox of the ecliptic alignment by rendering the effect universal -each observer sees an axis aligned to their own position. A clear falsification test is suggested: compare multipole alignments derived from the CMB as observed from spatially separated platforms (Earth vs. outer Solar System probe). If the axis is holographic, it will re-align with the displaced observer; if not, it should remain fixed on the sky. We emphasize this note as a conceptual proposal linking CMB anomalies to holographic cosmology, and invite further theoretical development and observational feasibility studies.

No final dos anos 70 e inicio dos anos 80, a geometria das variedades CR, modelo abstratode hipersuperficies reais em variedades complexas, atraiu a atencao de importantes matematicos tais como Chern, Moser, Fefferman, Jacobowitz, D. Jerison, J. Lee, Tanaka,Webster, entre outros. Essa geometria e particularmente rica quando a variedade CR e estritamente pseudoconvexa. Nesse caso, existe uma estreita relacao entre sua geometriae a geometria das variedades Riemannianas. Uma estrutura pseudohermitiana para uma variedade M munida de uma CR-estrutura T1;0(M) e uma forma de contato 0 que aniquilaa distribuicao de Levi H(M) = RefT1;0 + T0;1g, em que T0;1 = T1;0. Tal estrutura determinauma forma Hermitiana natural sobre a CR-estrutura T1;0(M), denominada forma deLevi e denotada por Lo. A forma de Levi e bem definida (para cada CR-estrutura) modulo multiplicacao por uma funcao suave, exatamente como ocorre na geometria Riemanniana conforme. Quando Lo e uma forma definida, dizemos que (M; ) e...

The thermal history of the universe before the epoch of nucleosynthesis is unknown. The maximum temperature in the radiation-dominated era, which we will refer to as the reheat temperature, may have been as low as 0.7 MeV. In this paper we show that a low reheat temperature has important implications for many topics in cosmology. We show that weakly interacting massive particles (WIMPs) may be produced even if the reheat temperature is much smaller than the freeze-out temperature of the WIMP, and that the dependence of the present abundance on the mass and the annihilation cross section of the WIMP differs drastically from familiar results. We revisit predictions of the relic abundance and resulting model constraints of supersymmetric dark matter, axions, massive neutrinos, and other dark matter candidates, nucleosynthesis constraints on decaying particles, and leptogenesis by decay of superheavy particles. We find that the allowed parameter space of supersymmetric models is altered, removing the usual bounds on the mass spectrum; the cosmological bound on massive neutrinos is drastically changed, ruling out Dirac (Majorana) neutrino masses mν only in the range 33 keV < ∼ mν < ∼ 6 (5) MeV, which is significantly smaller from the the standard disallowed range 94 eV < ∼ mν < ∼ 2 GeV (this implies that massive neutrinos may still play the role of either warm or cold dark matter); the cosmological upper bound on the Peccei-Quinn scale may be significantly increased to 10 16 GeV from the usually cited limit of about 10 12 GeV; and that efficient out-of-equilibrium GUT baryogenesis and/or leptogenesis can take place even if the reheat temperature is much smaller than the mass of the decaying superheavy particle.

We propose an alternative framework for the origin of the universe in which the Big Bang is
not a singular explosive event but the large-scale manifestation of quantum vacuum
fluctuations. In this model, virtual particle–antiparticle pairs, generated by zero-point energy,
could stabilize under sufficient energy conditions, initiating chain reactions that converted
vacuum energy into real particles. This collective process may explain the emergence of
spacetime expansion without requiring an initial singularity. Implications for early-universe
physics and potential observational signatures in the cosmic microwave background are
discussed.

We use Owens Valley Radio Observatory (OVRO) cosmic microwave background (CMB) anisotropy data to constrain cosmological parameters. We account for the OVRO beamwidth and calibration uncertainties, as well as the uncertainty induced by the removal of non-CMB foreground contamination. We consider open and spatially-flat-Λ cold dark matter cosmogonies, with nonrelativistic-mass density parameter Ω0 in the range 0.1–1, baryonic-mass density parameter ΩB in the range (0.005–0.029)h-2, and age of the universe t0 in the range (10–20) Gyr. Marginalizing over all parameters but Ω0, the OVRO data favors an open (spatially-flat-Λ) model with Ω0≃ 0.33 (0.1). At the 2σ confidence level model normalizations deduced from the OVRO data are mostly consistent with those deduced from the DMR, UCSB South Pole 1994, Python I-III, ARGO, MAX 4 and 5, White Dish, and SuZIE data sets.

We investigate the accretion rate, bolometric luminosity, black hole (BH) growth time and BH spin in a large AGN sample under the assumption that all such objects are powered via thin or slim accretion discs (ADs). We use direct estimates of the mass accretion rate, Ṁ , to show that many currently used values of L bol and L/L Edd are either under estimated or over estimated because they are based on bolometric correction factors that are adjusted to the properties of moderately accreting active galactic nuclei (AGN) and do not take into account the correct combination of BH mass, spin and accretion rate. The consistent application of AD physics to our sample of Sloan Digital Sky Survey (SDSS) AGN leads to the following findings: 1. Even the most conservative assumption about the radiative efficiency of fast accreting BHs shows that many of these sources must contain slim ADs. We illustrate this by estimating the fraction of such objects at various redshifts. 2. Many previously estimated BH growth times are inconsistent with the AD theory. In particular, the growth times of the fastest accreting BHs were over estimated in the past by large factors with important consequences to AGN evolution. 3. Currently used bolometric correction factors for low accretion rate very massive SDSS BHs, are inconsistent with the AD theory. Applying the AD set of assumptions to such objects, combined with standard photoionization calculations of broad emission lines, leads to the conclusion that many such objects must contain fast spinning BHs.

We propose the Mass Dissipation Model (MDM), a thermodynamically motivated extension of general relativity in which all matter continuously dissipates energy into spacetime. This dissipative flux is identified as the physical origin of gravity itself: spacetime curvature emerges not from static mass-energy, but from the continuous transfer of energy through dissipation. Within this framework, the phenomena usually attributed to dark matter and dark energy arise naturally without invoking exotic particles or a fundamental cosmological constant. Flat galaxy rotation curves, lensing anomalies, cosmic acceleration, and the Hubble tension all follow from the same mechanism. The evolving acceleration scale

We present an extensive comparison of models of structure formation with observations, based on linear and quasi-linear theory. We assume a critical matter density, and study both cold dark matter models and cold plus hot dark matter models. We explore a wide range of parameters, by varying the fraction of hot dark matter Ω ν , the Hubble parameter h and the spectral index of density perturbations n, and allowing for the possibility of gravitational waves from inflation influencing large-angle microwave background anisotropies. New calculations are made of the transfer functions describing the linear power spectrum, with special emphasis on improving the accuracy on short scales where there are strong constraints. For assessing early object formation, the transfer functions are explicitly evaluated at the appropriate redshift. The observations considered are the four-year COBE observations of microwave background anisotropies, peculiar velocity flows, the galaxy correlation function, and the abundances of galaxy clusters, quasars and damped Lyman alpha systems. Each observation is interpreted in terms of the power spectrum filtered by a top-hat window function. We find that there remains a viable region of parameter space for criticaldensity models when all the dark matter is cold, though h must be less than 0.5 before any fit is found and n significantly below unity is preferred. Once a hot dark matter component is invoked, a wide parameter space is acceptable, including n ≃ 1. The allowed region is characterized by Ω ν < ∼ 0.35 and 0.60 < ∼ n < ∼ 1.25, at 95 per cent confidence on at least one piece of data. There is no useful lower bound on h, and for curious combinations of the other parameters it is possible to fit the data with h as high as 0.65. You are reading the e-print archive version of this paper, which due to space restrictions doesn't have the figures. We strongly recommend you download the complete paper, either from papers.html (UK) or

We propose a mechanism for cosmological inflation based on energy redistribution from large-scale matter-antimatter annihilation in the early universe. Unlike standard inflationary models invoking a hypothetical scalar inflaton field, this approach introduces a translation term into the stress-energy tensor to account for residual energy density following annihilation. Incorporating this term into modified Friedmann dynamics, we demonstrate that even a minimal fraction of annihilation energy suffices to drive exponential expansion, satisfying the necessary e-folding condition without violating relativity or introducing exotic physics. Numerical estimates at Grand Unified Theory (GUT) scale densities confirm the mechanism exceeds inflationary requirements by many orders of magnitude. This framework preserves energy conservation and suggests new observational signatures in the cosmic microwave background (CMB) and primordial gravitational wave spectrum.

Evidence for the big bang can be provided from observational astronomy using Hubble's law (redshift of galaxies) also known as the 'Doppler effect' (Roy et al 2003) where the wavelength of light from distant galaxies is shifted towards the red end of the visible spectrum and results from receding galaxies. Hubble published his observations in 1929. It provides direct evidence that the galaxies in the universe are accelerating away from our reference point and implies that the universe is expanding (figure 1). This expansion has resulted in lower temperatures as the universe expanded compared to the initial high temperatures at the big bang. Radio astronomy has contributed significantly in providing evidence of the big bang by detecting radio signals from stars, galaxies, radio galaxies, quasars and pulsars way back to the singularity or big bang (Kaviraj, S. 2013).

We present new results on the angular momentum evolution of dark matter halos. Halos, from N-body simulations, are classified according to their mass growth histories into two categories: the accretion category contains halos whose mass has varied continuously and smoothly, while the merger category contains halos which have undergone sudden and significant mass variations (greater than 1/3 of their initial mass per event). We find that the angular momentum grows in both cases, well into the nonlinear regime. For individual halos we observe strong correlation between the angular momentum variation and the mass variation. The rate of growth of both mass and angular momentum has a characteristic transition time at around z ∼ 1.5 -1.8, with an early fast phase followed by a late slow phase. Halos of the merger catalog acquire more angular momentum even when the scaling with mass is taken into account. The spin parameter has a different behavior for the two classes: there is a decrease with time for halos in the accretion catalog whereas a small increase is observed for the merger catalog. When the two catalogs are considered together, no significant variation of the spin parameter distribution with the redshift is obtained. We have also found that the spin parameter neither depends on the halo mass nor on the cosmological model. From our simple model developed for the formation of a disk galaxy similar to the Milky Way, we conclude that our own halo must have captured satellites in order to acquire the required angular momentum and to achieve most of the disk around z ∼ 1.6. The distribution of the angular momentum indicates that at z ∼ 1.6 only 22% of the halos have angular momentum of magnitude comparable to that of disk galaxies in the mass range 10 10 -5 × 10 11 M ⊙ , clearly insufficient to explain the present observed abundance of these objects.

Brief Description: This work presents a fundamental alternative to the standard ΛCDM model that explains 85% of the presumed universe mass (dark matter) and cosmic acceleration (dark energy) through a single physical mechanism: primordial vortices in the timestream. The theory makes specific, testable predictions for pulsar timing arrays (100 ns anomalies), GPS clocks, and supernova observations. If confirmed, this would mean that the majority of assumed cosmic substances are geometric effects of spacetime itself-a paradigm shift of similar magnitude to relativity theory.

We develop an early-universe cosmology within the framework of the MAAT String Theory of Everything (ToE_MAAT), in which the five MAAT principles-Harmony (H), Balance (B), Creativity (S), Connectedness (V), and Respect (R)-are embedded as ethical invariants into string dynamics. Based on a modified Polyakov action, we derive effective 4D equations that introduce additional terms into the Friedmann equations near t = 0. We sketch a pre-inflationary regime, symmetry breaking, reheating, and testable signatures in the CMB, the stochastic gravitational wave background, and 21 cm cosmology. This work is conceptual and speculative; its aim is to provide a coherent, mathematically consistent narrative of the Big Bang as an ethical-physical phase transition.

We present a professional, equation-level autopsy of the ΛCDM paradigm and replace it with a minimal, Planck-covariant framework. The Planck two-measure 𝜎 P ∶= ℓ P 𝑡 P = ℏ 𝐺 𝑐 4 supplies the only regulator a tensor theory should need. We identify three structural failures in standard practice: (i) composite sources were never Planck-covariantly regulated, (ii) operators lacked a covariant open-systems limit, and (iii) the Kehrbruch 𝛼 𝜎 = 𝜎 P /(𝑅 𝑡) ∼ 10-123 was miscast as fine-tuning rather than scale ordering. With these repaired, dark-sector epicycles become dispensable, late-time tensions deflate, and the vacuum "catastrophe" reduces to a category error. The theory is unitary, covariant, minimal, and falsifiable-introducing no constants beyond {ℏ, 𝑐, 𝐺, 𝑘 B }.

We propose a minimal, covariant mechanism to defuse the Hubble tension using a spacetime fine-structure number α σ := σ P R t , σ P := P t P = G c 4 , where R is a cosmic length scale and t the cosmic age relevant to a probe. For R = c/H and t = 1/H one gets α σ = (t P H) 2 ∼ 10-122 today. Rather than changing early-universe physics, we use σ P to define a late-time, covariant coarse-grained contribution to the vacuum sector, ρ σ (a) = 3c 2 8πG ν(a) H 2 (a), with a-running ν(a) = ν 0 a p , p > 2, that is negligible at recombination and nonzero only at late times. This shifts late-time distance relations while leaving CMB physics intact, rotating degeneracy directions so that CMB/BAO-inferred H 0 and late-universe ladders overlap. We present closed-form background equations, synthetic posteriors illustrating the overlap, and falsifiable signatures in BAO, SNe Ia, and time-delay lenses. No new constants beyond { , c, G, k B } are introduced; σ P sets the covariant coarse-graining, and ν 0 is to be inferred.

If motion is the cosmic baseline, then "rest" is only a local approximation. We extend the Cooper Disparity Law (CDL)-originally formulated for mass, weight, and density-into the dynamical domain of speed, velocity, momentum, and inertia on cosmological scales. Working on an FLRW background with peculiar motions, we (i) formalize CDL's resonance-alignment and inertialmemory terms, (ii) embed them in the Newtonian-relativistic fluid picture used in large-scale structure (LSS), and (iii) derive phenomenological corrections to Euler/continuity dynamics, redshift-space statistics, and bulk-flow observables. We show how CDL terms map onto known tensions (e.g., Hubble-constant systematics from peculiar velocities) and propose falsifiable tests using DESI DR2 BAO, peculiar-velocity surveys, CMB dipole calibration, and cosmic-shear cross-correlations. Our extension reduces to ΛCDM when CDL parameters vanish, ensuring consistency with standard cosmology.

This paper presents a comprehensive framework for estimating the population and properties of particles within the observable universe. The methodology synthesizes the Standard Model of Particle Physics with the Lambda-Cold Dark Matter (ΛCDM) cosmological model, leveraging key observational data from the Cosmic Microwave Background (CMB), large-scale structure surveys, and high-energy astrophysics. We establish that the observable universe is dominated by components that cannot be directly counted: dark energy (∼68%) and dark matter (∼27%). The remaining ∼5% of the mass-energy budget consists of baryonic matter, which is itself outnumbered by relic photons and neutrinos from the Big Bang by orders of magnitude. We provide detailed calculations for estimating the abundance of long-lived particle species: approximately 10⁸⁰ protons and neutrons, a comparable number of electrons, 10⁸⁹ photons, and 10⁸⁹ neutrinos. The framework explicitly addresses the challenge of counting dark matter particles, presenting estimates contingent upon their hypothetical properties (e.g., Weakly Interacting Massive Particles (WIMPs)), and clarifies why dark energy is not a particulate substance and thus falls outside this inventory. Beyond mere enumeration, this review discusses the spatial distribution, energy spectra, and temporal evolution of these particle populations. We conclude by highlighting the profound implications of these findings-namely, that the matter constituting stars, planets, and life is an exceptionally rare constituent of the cosmos-and outline the future observational and experimental advancements necessary to refine this cosmic census. This work serves as a primer at the intersection of cosmology and particle physics, providing a structured approach to quantifying the fundamental contents of the universe.

Fuzzy dark matter (FDM) or wave dark matter is an alternative theory designed to solve the small-scale problems faced by the standard cold dark matter proposal for the primary material component of the Universe. It is made up of ultra-light axions having mass $\sim 10^{-22}\, {\rm eV}$ that typically have de Broglie wavelength of several kpc, alleviating some of the apparent small-scale discrepancies faced by the standard ΛCDM paradigm. In this paper, we calculate the halo mass function for the FDM using a sharp-k window function and compare it with one calculated using numerical simulations, finding the peak mass at roughly $10^{10}\, {M_{\odot }}$ for a particle mass of $2\times 10^{-22}\, {\rm eV}$. We also constrain the mass of FDM particle to be $^{\gtrsim}_{\sim} 2\times 10^{-22}\, {\rm eV}$ using the observations of high-redshift (z ∼ 10) lensed galaxies from CLASH survey.

We constrain flat cosmological models with a joint likelihood analysis of a new compilation of data from the cosmic microwave background (CMB) and from the 2dF Galaxy Redshift Survey (2dFGRS). Fitting the CMB alone yields a known degeneracy between the Hubble constant h and the matter density Ω m , which arises mainly from preserving the location of the peaks in the angular power spectrum. This 'horizonangle degeneracy' is considered in some detail and shown to follow a simple relation Ω m h 3.4 = constant. Adding the 2dFGRS power spectrum constrains Ω m h and breaks the degeneracy. If tensor anisotropies are assumed to be negligible, we obtain values for the Hubble constant h = 0.665±0.047, the matter density Ω m = 0.313±0.055, and the physical CDM and baryon densities Ω c h 2 = 0.115 ± 0.009, Ω b h 2 = 0.022 ± 0.002 (standard rms errors). Including a possible tensor component causes very little change to these figures; we set an upper limit to the tensor-to-scalar ratio of r < 0.7 at 95% confidence. We then show how these data can be used to constrain the equation of state of the vacuum, and find w < -0.52 at 95% confidence. The preferred cosmological model is thus very well specified, and we discuss the precision with which future CMB data can be predicted, given the model assumptions. The 2dFGRS power-spectrum data and covariance matrix, and the CMB data compilation used here, are available from .

We study the formation of structure in the Universe assuming that dark matter can be described by a scalar field Φ with a potential V (Φ) = -m 2 Φ2 /2 + λ Φ4 /4. We derive the evolution equations of the scalar field in the linear regime of perturbations. We investigate the symmetry breaking and possibly a phase transition of this scalar field in the early Universe. At low temperatures, the scalar perturbations have an oscillating growing mode and therefore, this kind of dark matter could lead to the formation of gravitational structures. In order to study the nonlinear regime, we use the spherical collapse model and show that, in the quadratic potential limit, this kind of dark matter can form virialized structures. The main difference with the traditional Cold Dark Matter paradigm is that the formation of structure in the scalar field model can occur at earlier times. Thus, if the dark matter behaves as a scalar field, large galaxies are expected to be formed already at high redshifts.

The dark matter candidates we are searching for, e.g. neutralinos, may be one of many components of the cold dark matter (CDM). We point out here that very subdominant components, constituting even 1% of the CDM for indirect detection and much less for direct detection, remain observable in current and future searches. So if a CDM signal is confirmed in CDM search experiments (except for a signal from annihilations in the dark halo) we will need to find out the halo fraction accounted for the CDM component we detected.

We study the occurrence of a strong first-order electroweak phase transition in composite Higgs models. Minimal constructions realising this scenario are based on the coset SO(6)/SO(5) which delivers an extended Higgs sector with an additional scalar. In such models, a two-step phase transition can be obtained with the scalar singlet acquiring a vacuum expectation value at intermediate temperatures. A bonus of the Nambu-Goldstone boson nature of the scalar-sector dynamics is the presence of non-renormalisable Higgs in- teractions that can trigger additional sources of CP violation needed to realise baryogenesis at the electroweak scale. Another interesting aspect of this scenario is the generation of gravitational wave signatures that can be observed at future space-based interferometers.

The observed galactic 511 keV line has been interpreted in a number of papers as a possible signal of dark matter annihilation within the galactic bulge. If this is the case then we should expect a similar spectral feature associated with nearby dwarf galaxies which are dark matter dominated. It has recently been argued [1] that the absence of such a signal excludes a dark matter explanation as the major source for the galactic 511 keV line. In the model presented here dark matter in the form of heavy quark nuggets produces the galactic 511 keV emission line through interactions with the visible matter. It is argued, however, that this type of interaction is not subject to the strong dark matter annihilation constraints presented in .