Dynamical Dark Energy in Light of Cosmic Distance Measurements.Ⅱ.A Study Using Current Observations

We extract key information on dark energy from current observations of BAO,OHD and H_(0),and find hints of dynamical behavior of dark energy.In particular,a dynamical dark energy model whose equation of state crosses-1 is favored by observations.We also find that the Universe has started accelerating at a lower redshift than expected.

Dynamical Dark Energy in Light of Cosmic Distance Measurements.Ⅰ.A Demonstration Using Simulated Datasets

We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity distances.Demonstrated using simulated data sets of the complete DESI,LSST and Roman surveys designed for BAO and SN distance measurements,we show that using our method,the dynamical behavior of the energy,pressure,equation of state(with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data,which allows for robust diagnostic tests for dark energy models.

The Origin, Properties and Detection of Dark Matter and Dark Energy

The pictures from the James Webb Space Telescope (JWST) suggest that massive galaxies were already at the beginning of the expansion of the Universe because there was too short time to create them. It is consistent with the new cosmology presented within the Scale-Symmetric Theory (SST). The phase transitions of the initial inflation field described in SST lead to the Protoworld—its core was built of dark matter (DM). We show that the DAMA/LIBRA annual-modulation amplitude forced by the change of the Earth’s velocity (i.e. baryonic-matter (BM) velocity) in relation to the spinning DM field in our Galaxy’s halo should be very low. We calculated that in the DM-BM weak interactions are created single and entangled spacetime condensates with a lowest mass/energy of 0.807 keV—as the Higgs boson they can decay to two photons, so we can indirectly detect DM. Our results are consistent with the averaged DAMA/LIBRA/COSINE-100 curve describing the dependence of the event rate on the photon energy in single-hit events. We calculated the mean dark-matter-halo (DMH) mass around quasars, we also described the origin of the plateaux in the rotation curves for the massive spiral galaxies, the role of DM-loops in magnetars, the origin of CMB, the AGN-jet and galactic-halo production, and properties of dark energy (DE).

A Dark Energy Hypothesis I

The cosmological constant, Λ, represents dark energy. The dark energy hypothesis (DEH) replaces Λ with a variable quantity, the cosmological parameter: Λ=1a2η2In this formula, “a” is the scale factor and η the conformal time: adη = cdt. A companion paper (DEH II) develops and explores a cosmological model with this variable parameter. This paper portrays the origin of the cosmological parameter in the uncoupling of time and space in the early universe from a prior state in which the comoving coordinates x0 = η and x1 = χ, the cosmic latitude, are coupled. In this hypothesis dark matter is a co-product of the decoupling, but its nature remains mysterious.

A Dark Energy Hypothesis II

The article develops a cosmological model based on a hypothesis that dark energy is a cosmological variable rather than a constant. A companion paper (DEH I) derives a formula for this variable cosmological parameter as well as an argument that the early universe produces it and dark matter. The developed model leads to a series of self-consistent results including a prediction that provides a test for it. The results include comparisons of the DEH and the ΛCDM theory.

Dark Matter and Dark Energy from Lattice Model of Universe

The article considers a conceptual universe model as a periodic lattice (network) with nodes defined by the wave function in a background-independent Hamiltonian based on their relations and interactions. This model gives rise to energy bands, similar to those in semiconductor solid-state models. In this context, valence band holes are described as dark matter particles with a heavy effective mass. The conducting band, with a spontaneously symmetry-breaking energy profile, contains particles with several times lighter effective mass, which can represent luminous matter. Some possible analogies with solid-state physics, such as the comparison between dark and luminous matter, are discussed. Additionally, tiny dark energy, as intrinsic lattice Casimir energy, is calculated for a lattice with a large number of lattice nodes.

Dynamic Spacetime: Key to the Mysteries of Dark Matter and Dark Energy

Physics is a branch of science to study matter and its motion in space and time. Development of physics usually upgrades human perspective and understanding of the space and time. Einstein successfully developed special and general theories of relativity and creatively promoted our perspective of spacetime from Newton’s absolute space and time to his relative spacetime. Based on redshift and distance measurements of galaxies and distant type Ia supernovae, cosmologists have suggested that our universe is expanding at an ever-increasing rate driven by a mysterious dark energy. Recently, the author has proposed that spacetime is dynamic. Spacetime is said to be absolute if it is independent of matter and motion, relative if it is affected by matter and motion, and dynamic if it mutually interacts with matter and motion. In dynamic spacetime, not only do matter and motion distort spacetime, but they are also affected by the distorted spacetime. Spacetime to be dynamic is a consequence of a deep insight to Mach’s principle, which tells us that the inertia of an object results from the gravitational interaction by the rest of the universe. Reaction of dynamic spacetime on a traveling light causes light redshift. Reaction of dynamic spacetime on a fast moving neutrino slows down the neutrino. The derived redshift-distance relation perfectly explained the measurements of distant type Ia supernovae and gamma ray bursts (GRBs) and also naturally obtained Hubble’s law as an approximate relation at small redshift. This explanation of cosmological redshift as the opposition of dynamic spacetime does not mandate the universe to be expanding and accelerating, so that it does not need the universe to be initiated from a Big Bang and driven out mainly by a mysterious dark energy. Extremely slowed down neutrinos in dynamic spacetime, when they are gravitationally trapped around clusters, galaxies, and any celestial objects, would play the role of dark matter in explaining the velocity-radius relations of galaxy’s or cluster’s rotations.

Introducing a 2nd Universal Space-Time Constant Can Explain the Observed Age of the Universe and Dark Energy

The purpose of this paper is to introduce new theoretical concepts as opposed to accepting the existence of dark entities, such as dark energy. This research sought to introduce a 2nd universal space-time constant, besides having a finite speed constant (speed of light in vacuum c). A finite universal age constant b is introduced. Namely, this paper shows that the changes in the Earth’s anomalistic year duration over time support the hypothesis of the age of the universe correlating with a maximum number of orbital revolutions constant. Neglecting the gravitational influence of other cosmological entities in the proximity of the Earth, the constant maximum number of revolutions is herewith determined solely by the Earth’s orbital revolutions around the Sun. The value of the universal age constant b is calculated to be around 13.8 billion orbital revolutions, derived out of an equation related to the changes in the Earth’s anomalistic year duration over time and the so-called Hubble tension. The above-mentioned calculated value b correlates well with the best fit to measured data of the cosmic microwave background radiation (CMBR) by the Planck spacecraft, the age of the observed universe is measured to be approximately 13.787 ± 0.020 billion years (2018 final data release). Developing a theory with this 2nd universal space-time constant b, being covariant with respect to the Lorentz transformations when time spans are large, gives results such as: A confirmation of the measured CMBR value of 13.787 ± 0.020 billion years. Correlating well with the observed expansion rate of the universe (dark energy). The universe’s expansion accelerating over the last four to five billion years.

How Gravitational Effects on the Quantum Vacuum Might Explain Dark Energy and Dark Matter Observations

Following a brief review of the “black hole dark energy radiation” and “gravitized vacuum” references, a novel theory of how gravity might affect the quantum vacuum is proposed. This overarching theory proposes that the gravitational field of a sufficiently concentrated collection of matter and/or energy upregulates the virtual particle activity of the adjacent quantum vacuum, thus its energy density and lensing capacity. In contrast to general relativity, the particle and wave duality of quantum physics is necessary for understanding quantum vacuum gravitational effects. Very recent supporting and pending observational studies are discussed, including the ingenious and extremely sensitive vacuum scale to be deployed for the Archimedes Experiment. Support or falsification of this proposal may be imminent.

Constraining Neutrino Mass in Dynamical Dark Energy Cosmologies with the Logarithm Parametrization and the Oscillating Parametrization

We constrain two dynamical dark energy models that are parametrized by the logarithm form of and the oscillating form of . Comparing with the Chevallier-Polarski-Linder (CPL) model, the two parametrizations for dark energy can explore the whole evolution history of the universe properly. Using the current mainstream observational data including the cosmic microwave background data and the baryon acoustic oscillation data as well as the type Ia supernovae data, we perform the X2 statistic analysis to global fit these models, finding that the logarithm parametrization and the oscillating parameterization are almost as well as the CPL scenario in fitting these data. We make a comparison for the impacts of the dynamical dark energy on the cosmological constraints on the total mass of active neutrinos. We find that the logarithm parametrization and the oscillating parameterization can increase the fitting values of Σmv. Looser constraints on Σmv are obtained in the logarithm and oscillating models than those derived in the CPL model. Consideration of the possible mass ordering of neutrinos reveals that the most stringent constraint on Σmv appears in the degenerate hierarchy case.

A Study of Holographic Dark Energy Models with Configuration Entropy

The holographic dark energy models provide an alternative description of dark energy.These models are motivated by the possible application of the holographic principle to the dark energy problem.In this work,we present a theoretical study of the one parameter Li holographic dark energy and the two parameter Barrow holographic dark energy models using configuration entropy of the matter distribution in the universe.The configuration entropy rate exhibits a distinct minimum at a specific scale factor that corresponds to the epoch,beyond which dark energy takes a driving role in the accelerated expansion of the universe.We find that the location of the minimum and magnitude of the entropy rate at the minimum are sensitive to the parameters of the models.We find the best fit relations between these quantities and the parameters of each model.We propose that these relations can be used to constrain the parameters of the holographic dark energy models from future observations such as the SKA.Our study suggests that the signature of a large quantum gravitational effect on the future event horizon can be detected from measurements of the configuration entropy of the matter distribution at multiple redshifts.

How Dark Energy Might Be Produced by Black Holes

If confirmed, the new galactic observations in support of rapidly growing supermassive black holes in association with their production of dark energy may provide for a quantum leap forward in our understanding of black holes, dark energy, and universal expansion. The primary implication of these observations is that growth of black holes may well be coupled with universal expansion (“cosmological coupling”). Study of the Flat Space Cosmology (FSC) model, in conjunction with these new observations, suggests a novel mechanism of “black hole dark energy radiation”. This brief note gives a rationale for how the high gravitational energy density vacuum within or adjacent to a black hole horizon could be sufficiently energetic to pull entangled pairs of positive matter energy particles and negative dark energy “particles” of equal magnitude out of the horizon vacuum and send them off in opposite directions (i.e., gravitationally-attractive matter inward and gravitationally-repelling dark energy outward). One effect would be that a black hole can rapidly grow in mass-energy without mergers or the usual accretion of pre-existing matter. A second effect would be continual production of dark energy within the cosmic vacuum, fueling a continuous and finely-tuned light-speed expansion of the universe.

From the Hubble Constant to the Black Hole Model. Universe Expansion with Matter Creation and a New Perspective on Dark Energy Observations

Comparison of the Hubble parameter with cosmological quantities strongly supports the black hole model for the description of the Universe evolution. Such evolution requires matter creation and has implications for what is currently referred to as “dark energy” and the “cosmological constant”.

Dark Matter, Dark Energy, and Occam’s Razor

Even though dark matter and dark energy have long been accepted as being of fundamental importance in cosmology, in this paper, we will present arguments to show that neither is necessary. Instead, the phenomena they are thought to be responsible for are consequences of a vacuum whose curvature varies with time. We will focus on three phenomena that are thought to require the existence of dark energy and dark matter. The first is the idea that dark energy is responsible for the observed accelerating expansion of the universe. We will show instead that with time-varying curvature, Einstein’s equations demand such an acceleration without reference to dark or any other form of energy. Turning to dark matter, it is supposedly required to explain the observed constant velocity profile of the stars making up the disks of spiral galaxies and to explain the strong gravitational lensing observed in galaxy clusters. We will show, however, that both phenomena can again be understood in terms of the vacuum and its curvature. In the former case, we will show that galaxies exist within a rotating volume of the vacuum and that this leads directly to the observed constant velocity profiles. In the latter case, gradients of the vacuum curvature serving as a varying index of refraction are responsible. Using numerical results from our new model of nucleosynthesis, we estimate the degree of bending to expect and find that the results are in accord with observation. Our new model very naturally explains the phenomena attributed to dark matter and dark energy and since neither has been observed after several decades of looking, Occam’s razor tells us that neither exists.

A New Approach to the Dark Matter/Dark Energy Puzzle

The dilemmas posed by dark matter and dark energy have been with us for decades without a satisfactory resolution. We propose that both DM and DE can be explained by the existence of long-lived topological gravitational vortices that were produced in the quark-gluon epoch of cosmic inflation due to the misalignment of the gravitational and strong forces. This is analogous to the misalignment mechanism proposed for the production of axions in the early universe. The masses of these topological vortices are expected to be on the order of the nucleon mass. Possible means for their detection are discussed.

Dark Energy from Kaluza-Klein Spacetime and Noether’s Theorem via Lagrangian Multiplier Method

The supposedly missing dark energy of the cosmos is found quantitatively in a direct analysis without involving ordinary energy. The analysis relies on five dimensional Kaluza-Klein spacetime and a Lagrangian constrained by an auxiliary condition. Employing the Lagrangian multiplier method, it is found that this multiplier is equal to the dark energy of the cosmos and is given by where E is energy, m is mass, c is the speed of light, and λ is the Lagrangian multiplier. The result is in full agreement with cosmic measurements which were awarded the 2011 Nobel Prize in Physics as well as with the interpretation that dark energy is the energy of the quantum wave while ordinary energy is the energy of the quantum particle. Consequently dark energy could not be found directly using our current measurement methods because measurement leads to wave collapse leaving only the quantum particle and its ordinary energy intact.

Friedmann Cosmology with Bulk Viscosity:A Concrete Model for Dark Energy

The universe content is considered as a non-perfect fluid with bulk viscosity and can be described by a general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. An explicitly bulk viscosity dark energy model is proposed to confront consistently with the current observational data sets by statistical analysis and is shown consistent with （not deviated away much from） the concordant A Cold Dark Matter （CDM） model by comparing the decelerating parameter. Also we compare our relatively simple viscosity dark energy model with a more complicated one by contrast with the concordant ACDM model and find our model improves for the viscosity dark energy model building. Finally we discuss the perspectives of dark energy probes for the coming years with observations.

Viscous holographic f(Q)cosmology with some versions of holographic dark energy with generalized cut-offs

The work reported in this paper demonstrates the cosmology of f(Q)gravity and the reconstruction of various associated parameters with different versions of holographic dark energy with generalized cut-offs,where Q=6 H^(2).The Universe is considered to be filled with viscous fluid characterized by a viscous pressureΠ=-3 Hξ,whereξ=ξ0+ξ1 H+ξ2(˙H+H^(2)and H is the Hubble parameter.Considering the power law form of expansion,we have derived the expression of f(Q)under a non-viscous holographic framework and it is then extended to viscous cosmological settings with extended generalized holographic Ricci dark energy.The forms of f(Q)for both the cases are found to be monotonically increasing functions of Q.In the viscous holographic framework,f(Q)is reconstructed as a function of cosmic time t and is found to stay at a positive level with Nojiri-Odintsov cut-off.In these cosmological settings,the slow roll parameters are computed and a scope of exit from inflation and quasiexponential expansion are found to be available.Finally,it is observed that warm inflationary expansion can be obtained from this model.

Singularities and Entropy in Bulk Viscosity Dark Energy Model

In this paper bulk viscosity is introduced to describe the effects of cosmic non-perfect fluid on the cosmos evolution and to build the unified dark energy （DE） with （dark） matter models. Also we derive a general relation between the bulk viscosity form and Hubble parameter that can provide a procedure for the viscosity DE model building. Especially, a redshift dependent viscosity parameter ζ ∝ λ0 ＋λ1（1 ＋z）n proposed in the previous work [X.H. Meng and X. Dou, Commun. Theor. Phys. B2 （2009） 377] is investigated extensively in this present work. Further more we use the recently released supernova dataset （the Constitution dataset） to constrain the model parameters. In order to differentiate the proposed concrete dark energy models from the well known ACDM model, statefinder diagnostic method is applied to this bulk viscosity model, as a complementary to the Om parameter diagnostic and the deceleration parameter analysis performed by us before. The DE model evolution behavior and tendency are shown in the plane of the statefinder diagnostic parameter pair {τ, s} as axes where the fixed point represents the A CDM model The possible singularity property in this bulk viscosity cosmology is also discussed to which we can conclude that in the different parameter regions chosen properly, this concrete viscosity DE model can have various late evolution behaviors and the late time singularity could be avoided. We also calculate the cosmic entropy in the bulk viscosity dark energy frame, and find that the total entropy in the viscosity DE model increases monotonously with respect to the scale factor evolution, thus this monotonous increasing property can indicate an arrow of time in the universe evolution, though the quantum version of the arrow of time is still very puzzling.

A Two-Dimensional Brans—Dicke Star Model with Exotic Matter and Dark Energy

A two-dimensional Brans-Dicke star model with exotic matter and dark energy is studied in this paper,the field equation and balance equation are derived at finite temperature,the analytic solutions of these equations canbe used to calculate the mass of star.In addition,we find that star's mass has a minimum when matter state parameterγ→0.