Now the prevailing practice has been to consider ρ in Equation (6) as encompassing **dark** **energy**, matter and radiation. Since the Hubble parameter H has to decrease over time in Equation (6) for the age of the universe to increase, it is sufficient for matter and radiation density to decrease while **dark** **energy** density can remain con- stant. Indeed, so far the astronomical observational constraints are consistent with a time-independent cosmo- logical constant. However, it may be argued that since 8π

The four regions in the light-**dark** dual universe include the light universe, the gravity bulk space, the antigravity bulk space, and the **dark** universe. Through the symmetry among the space regions, all regions expand synchronic- ally and equally (The symmetry is necessary for the ul- timate reversibility of all cosmic processes). The light universe is the only region with the four-dimensional space-time and with kinetic **energy** from the beginning, and all other three regions have variable dimensional space-time without kinetic **energy**. The light universe occupies 25% of the total universe, while the other regions occupy 75% of the total universe, so the maximum **dark** **energy** from the **dark** universe, the gravity bulk space, and the antigravity bulk space is 75%. The present observable universe about reaches the maximum (75%) at the ob- served 72.8% **dark** **energy** [17]. At 72.8% **dark** **energy**, the calculated values for baryonic matter and **dark** matter (with the 1:5 ratio) are 4.53% (=(100 – 72.8)/6) and 22.7% (=4.53 × 5), respectively, in excellent agreement with observed 4.56% and 22.7%, respectively [17].

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Recent astronomical NASA observations indi- cates that visible matter contributes only to about 4% of the universe total **energy** density, meanwhile, **dark** matter and **dark** **energy** con- tributes to 26% and 70% of the universe total **energy**, respectively, with an average density close to 10 –26 kg/m 3 . This paper proposes an equation of state of **dark** **energy** and **dark** matter as one unified entity. This equation is derived based on the ideal gas equation, Boltzmann constant, Einstein **energy**-mass principle and based on the assumption that **dark** **energy** and **dark** matter behave as a perfect fluid. This analysis presents what could be the most fun- damental particle and quanta of **dark** matter and **dark** **energy**. Considering NASA’s Cosmic Mi- crowave Background Explorer (CMB) which es- timated that the sky has an average temperature close to 2.7251 Kelvin, then the equivalent mass and **energy** of the proposed fundamental particle is determined. It is found that this candidate particle has an equivalent mass of 4.2141 × 10 –40

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The following sections are organized as follows: In section 2 we summarize the main tenets of Information Relativity theory, and depict its main transfor- mations. In section 3 we apply the theory to a simplified model of the Universe, in which large-scale celestial bodies, like galaxies and galaxy clusters, are com- pact bodies receding rectilinearly along the line-of-sight of an observer on Earth. In our simplistic model we neglect contributions to **dark** matter caused by the rotation of celestial structures (e.g., the rotation of galaxies), and of their consti- tuents (e.g., rotation of stars inside galaxies). For such a grossly simplified un- iverse, we define **dark** matter, and derive exact terms for the dynamics between matter and **dark** matter densities, and of their respective **energy** distributions in the universe, as functions of the recession velocity. In section 4 we express the derived terms as functions of the redshift z , and utilize the theoretical results to explain the GZK cosmic rays cutoff at z ≈ 1.6 [29] [30], and the “cosmological desert” at higher redshifts. In section 5 we propose a novel physical explanation of **dark** **energy**, according to which **dark** **energy** is simply the **energy** carried by **dark** matter. We corroborate our explanation by comparing the predicted amounts of the **energy** carried by **dark** matter in different ranges of redshift, with observed results based on ΛCDM cosmologies, and by comparing the predicted equality of matter and **dark** matter **energy** densities at redshift z = 0.5, with ob- servational data on what is known as the “coincidence problem”, namely the observed equality between the densities of matter and **dark** **energy** at redshift z ≈ 0.55 [31] [32] [33]. In Section 6 we summarize and draw main conclu- sions.

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Over abundance of magnetic monopoles predicted by the Grand Unification Theories is inconsistence with current astronomical observation. The inflation- ary hypotheses with a vacuum **energy** deriving the exponential expansion can explain the two long-standing problems, flatness and horizon of the universe; and somehow suppress the abundance of monopoles. However, the dynami- cal scalar field has considerable uncertainties, which even leads to inflationary models separating from particle physics. This paper makes a small change, the early universe undergoes free expansion rather than an adiabatic one widely adopted, In such a case, the annihilation of abundant magnetic monopoles is just required in driving the inflation, so that the three long-term problems are automatically solved. On the other hand, the relic mass of failed annihilation of monopoles is responsible for the **dark** matter at present epoch. And ongoing annihilation on stars and compact objects corresponds to the **dark** **energy**. As monopole relics may exist in the form of monopole anti-monopole pairs, a new strategy of direct search is proposed.

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It follows from the above that the problem of explanation of nature of **dark** matter and **dark** **energy** is interdisciplinary. Therefore, its solution requires coordinated theoretical and experimental studies of all exact sciences. However, such studies have so far been carried out only in the theory of linear electric cir- cuits. They have been still neither confirmed nor refuted by anyone. Thus, unadjusted errors of the exist- ing version of the STR still hamper the development of both physics and other exact sciences.

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In Chapter 3 of this work, which is based on Brout et al. (2018a) I present the detailed cosmological analyses underpinning the measurement of cosmological parameters from 207 spectroscopically classified type Ia supernovae (SNe Ia) from the first three years of the **Dark** **Energy** Survey Supernova Program (DES-SN), spanning a redshift range of 0.017 < z < 0.849. This detailed systematic uncertainty analysis indicates nearly equal contributions from photometric calibration, astrophysical bias corrections, and instrumen- tal bias corrections. While the sample is < 1/3 the size of the Pantheon sample, the constraints on w are only larger by 1.4 × , showing the impact of the DES SN Ia light curve quality. Interestingly, I find no evidence for a Hubble residual step (0.007 ± 0.018 mag) as a function of host galaxy mass for the DES subset, in 2.4σ tension with previous mea- surements. I also present novel validation methods of the sample using simulated SNe Ia inserted in DECam images and using large catalog-level simulations to test for biases in our analysis pipelines.

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Analysis of WMAP and Planck spacecraft data has proved that we live in an invisible Multiverse, referred to as hidden, that has a quaternion structure. It explains the reason for the mutual invisi- bility of parallel universes contained in the hidden Multiverse. It is shown that the hidden Multi- verse includes most likely twenty parallel universes from different dimensions, six of which are adjacent to our universe. Besides, edges of the hidden Multiverse are connected to other (from one to four) Multiverses, which are observable neither by electromagnetic nor by gravitational ma- nifestations. The Multiverse described contains four matter-antimatter pairs, annihilation of which is prevented by relative spatial position of the universes. The experimental proof of exis- tence of the hidden Multiverse is explained to be the phenomenon of **dark** matter and **dark** **energy** that correspond to other invisible parallel universes, except ours, included in the hidden Multi- verse. General scientific principle of physical reality of imaginary numbers, refuting some of the statements of the existing version of the special theory of relativity, is a physical and mathematical foundation of the outlined conception of the hidden Multiverse. The article presents relativistic formulas of the theory of special relativity adjusted in accordance with the principle. It also offers appropriate interpretation of multidimensional space of the hidden Multiverse.

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This is a new profound confirmation of our previous result and reinforces the confi- dence in the K-(or K3) Kähler gained from its use in superstring theory and E-Infinity theory alike [2]-[108]. In particular one should note that the negative sign of the signa- ture τ = − 16 can be interpreted as a clear hint that pure **dark** **energy** works in the op- posite direction to **dark** matter and ordinary **energy** [1]-[80]. It is also note worthy to observe that the above result agrees almost completely with that obtained from the geometry of Kerr black holes [8].

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The purpose of this paper, however, is not to explain why the FSC model, now integrated into the flat universe Friedmann equations with a cosmological term, rigorously follows observations of cosmic flatness within the CMB. This point has been made in previous FSC publications [Tatum (2015)]. Rather, it is the purpose of this paper to further explore the possible nature of gravity, **dark** **energy** and **dark** matter. While the FSC model clearly indicates that **dark** **energy** is systemic negative gravitational **energy**, the key question becomes “How does this finite constant velocity expanding cosmic system work at its most funda- mental level? Specifically, what is the fundamental nature of its gravity , especial- ly in relation to **dark** **energy** and **dark** matter ?”

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explanatory power to defend the integrity of physics against the multiverse hypothesis. We emphasize that noncommutative (NC) spacetime necessarily implies emergent spacetime if spacetime at micro- scopic scales should be viewed as NC [1]. We will elaborate the emergent gravity from a large N matrix model by considering the vacuum in the NC Coulomb branch satisfying the Heisenberg alge- bra and argue that **dark** **energy** and **dark** matter may arise as a cosmic uroboros of quantum gravity due to the coherent vacuum structure of spacetime.

value of unity for Ω. Even a value which came very close would need explanation in the same way as values of Ω close to 1 were thought to be too close for coincidence even when observations were only within 12% of the exact value. With the existing Planck data, it would be possible to investigate how the constraints on other cosmological parameters would be affected by applying an exact value of two thirds for the **dark** **energy** density, and how any possible deviations in the assumed universal isotropy and uniformity might lead to deviations from the ideal value.

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where again B is an arbitrary function of φ. Disfor- mal interactions have been shown to arise in the four dimensional effective theory resulting from various brane world scenarios [10, 11], in branon models [12, 13] and in theories of massive gravity [14, 15]. Disformal cou- plings are particularly interesting in theories where an (approximate) shift symmetry for the scalar field is used to protect the mass of the **dark** **energy** scalar, and ensure that it can remain light on cosmological scales. Unlike conformal couplings, disformal couplings to matter do not break this shift symmetry. One prime example is provided by the Goldstone modes of a global symmetry where the interaction potential results from a soft and explicit breaking of the symmetry. Axion quintessence models fall into this category and are an example of a thawing model of **dark** **energy** [16]. These theories do not make a definitive prediction for the scale of the dis- formal interaction, allowing it to lie anywhere between the **dark** **energy** scale Λ ∼ 10 −3 eV and the Planck scale

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Recently Kaloper and Padilla [11] have attacked the cos- mological constant from a novel standpoint, they have gone into the infra red for their resolution, as far as you can possibly go in fact, a global transformation. There have been many attempts to attack the cosmological con- stant from the UV standpoint but not from the IR. Their model is locally indistinguishable from General Relativity, deviations arising only at a global level, which they argue is at the heart of the cosmological constant, when thought of as the global component of the stress **energy** tensor. This global addition allows them to sequester from grav- ity all radiative corrections to the vacuum **energy** from a protected matter sector, which can of course include the Standard Model [11]. The result is a residual cosmological constant that is crucially radiatively stable and insensitive to matter loop corrections to the vacuum **energy** at any or- der in perturbation theory. However it is not large enough to provide the **dark** **energy**. In [12] they have addressed the **dark** **energy** question in the context of the seques- tering model and once again their solution is intriguing. One of the key aspects of the initial formulation of the mechanism for sequestering the Standard Model vacuum **energy** is that it relies on a Universe of finite spatial vol- ume, a closed Universe which will inevitably collapse in the future. In [12] they presented a mechanism which led to the collapse. The solution requires a new scalar field whose potential is linear and becomes negative, and in doing so provides the negative **energy** density required to end the expansion. The model is tightly constrained,

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In this paper, we have studied an anisotropic LRS Bianchi type-II early decelerating and late-time accelerating universe filled with minimally interacting **dark** matter and holographic **dark** **energy** components. We have obtained exact solution of Einsten's field equations by using hybrid expansion law for the average scale factor of the model. We have found that the anisotropy of expansion and the skewness parameter of the holographic **dark** **energy** vanish for large cosmic time leading to an isotropic universe. The EoS parameter of the **dark** **energy** is a function of time and assumes a constant negative value for large time and consequently the present and future holographic **dark** **energy** model behaves like a phantom model, C D M model and quintessence model for specific values of the parameter ().

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What is the nature of the “**dark** matter” of this mysterious material, which has a gravitational effect, but does not emit or absorb light? Astronomers do not know. **Dark** **energy** constitutes a significant part of the entire contents of the Universe, but this was not always known. Attempts to find a way to measure or calculate the value of the vacuum **energy** density completely failed or gave results inconsistent with observations or other proven theoretical results. Some of these results are theoretically implausible due to some unrealistic assumptions on which the calculation model is based. And some theoretical results are in conflict with observations, and the conflict itself is caused by some dubious hypotheses on which the theory is based.

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In 2008, Tomi Koivisto and David F. Mota presented a paper entitles “Vector field models of inflation and **Dark** **Energy**”[3]. In their work, spatial vector fields are shown to be compatible with the cosmological anisotropy bounds if only slightly displaced from the potential minimum while dominant, or if driving an anisotropic expansion with nearly vanishing quadropole today. The Bianchi I model with a spatial field and an isotropic fluid is studied as a dynamical system, and several types of scaling solutions are found. On the other hand, time-like fields are automatically compatible with large-scale isotropy. They show that they can be dynamically important if non-minimal gravity couplings are taken into account. As an example, they reconstruct a vector-Gauss-Bonnet model which generates the concordance model acceleration at late times and supports an inflationary epoch at high curvatures. The evolution of the vortical perturbations in these models is computed.

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The nature of **dark** **energy** is a central mystery in cosmology and is the thrust of major experimental activity, including the **Dark** **Energy** Survey [12] and the Euclid satellite, due to be launched in 2020 [13]. Chameleon theories are a significant target for these experiments. This article concerns the possibility that chameleons may be detected first in a table-top experiment on earth using ultracold atoms. Although the chameleon field φ is properly described by relativistic quantum field theory, a simple relation describes its non-relativistic steady-state: [4]

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The phenomenology of the higher-order operators intro- duced in Sec. II can be classified according to the **dark** **energy** scalar multiplicity in the final states. Since they all lead to the same signature, i.e., they contribute to missing **energy**, we may add the respective ϕ multiplicities inco- herently to the full hadronic final state to include the effects of the higher-order operators. The number of ϕ fields in a particular operator dictates the number of effective operator insertions, which again determines the effective scaling of a cross section with the scale M. For instance, L 7 describes a scalar self-interaction and will not contribute to 2ϕ pro- duction with for our case C 10 ¼ 0. However it can be combined with L 1;2 to obtain a 3ϕ final state with a scaling ∼M −7 at the amplitude level. Note, that this way the

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