Physics

The Friedmann equations valid for the transparent universe are modified for the universe with opacity caused by absorption of light by ambient cosmic dust in intergalactic space. The modified equations lead to a cosmological model, in which cosmic opacity produces radiation pressure that counterbalances gravitational forces. The proposed model predicts a cyclic expansion/contraction evolution of the Universe within a limited range of scale factors with no initial singularity. The maximum redshift, at which the contraction of the Universe stops, is ~14-15. The model avoids dark energy and removes some other tensions of the standard cosmological model.

We elaborate on statistical thermodynamics models of relativistic geometric flows as generalisations of G. Perelman and R. Hamilton theory centred around C. Carathéodory axiomatic approach to thermodynamics with Pfaffian differential equations. The anholonomic frame deformation method, AFDM, for constructing generic off--diagonal and locally anisotropic cosmological solitonic solutions in the theory of relativistic geometric flows and general relativity is developed. We conclude that such solutions can not be described in terms of the Hawking--Bekenstein thermodynamics for hypersurface, holographic, (anti) de Sitter and similar configurations. The geometric thermodynamic values are defined and computed for nonholonomic Ricci flows, (modified) Einstein equations, and new classes of locally anisotropic cosmological solutions encoding solitonic hierarchies.

In this paper, we investigate a transitioning model of Bianchi type V universe in Brans-Dicke theory of gravitation. The derived model not only validates Mach's principle but also describes the present acceleration of the universe. In this paper, our aim is to constrain an exact Bianchi type V universe in Brans - Dicke gravity. For this sake, firstly we obtain an exact solution of field equations in modified gravity and secondly constrain the model parameters by bounding the model with recent H(z) and Baryon acoustic oscillations (BAO) observational data. The current phase of accelerated expansion of the universe is also described by the contribution coming from cosmological constant screened scalar field with deceleration parameter showing a transition redshift of about z t =0.79 . Some physical properties of the universe are also discussed.

The masses of the elementary particles as well as their charges and spins (herein expressed in terms of the elementary charge and Planck's constant, respectively) belong to the fundamental physical constants. Presently, no fundamental theory describing them is available, so their values remain mysterious. In this work we offer an approach based on the Brown-York quasi-local energy which includes the self-energy of an object. In order to compute this energy we model the spacetime of the renormalized electron (and other leptons) by the Kerr-Newman metric. Placing conditions on the associated energies at different radii we arrive at various constraints on the mass, charge and spin.

In this work, we extend the work of gravastars to analyze the role of electromagnetic field in f(R,T) gravity. We consider the irrotational cylindrically symmetric geometry and established the f(R,T) field equations and conservation laws. After considering charged exterior geometry, the mathematical quantities for evaluating Israel junction conditions are being calculated. The mass of the gravastar-like cylindrical structure is calculated through the equations of motion at the hypersurface in the presence of an electromagnetic field. The behavior of electric charge on the length of the thin shell, energy content, and entropy of gravastar is being studied graphically. We concluded that charge has an important role in the length of the thin shell, energy content, and entropy of gravastar.

Coordinated inference problems are being introduced as a basis for a neural network representation of the locality problem in the holographic bulk. It is argued that a type of problem originating in the "prisoners and hats" dilemma involves certain non-local structures to be found in the AdS/CFT duality. The neural network solution to this problem introduces a new approach that can be flexible enough to identify holographic dualities beyond AdS/CFT. Neural networks are shown to have a significant role in the connection between the bulk and the boundary, being capable of inferring sufficient information capable of explaining the pre-arrangement of observables in the bulk that would lead to non-local precursor operators in the boundary.

In this work, we study emission correlations in Rainbow Gravity (RG) black holes known to have black hole remnants. Non-thermal corrections are responsible for generating non-zero correlations between particle emission events during the black hole evaporation process. With this in mind, we calculate the temperatures considering back-reaction effects. Then, we obtain the correlations between emission events for a RG metric proposed by Magueijo and Smolin. We also discuss through a numerical analysis the emission correlations behavior in the last stages of evaporation of the black hole.

The Einstein's General Relativity theory and the Friedmann-Lemaitre-Robertson-Walker (FLRW) metrics define the main equations that rule the history and future of the Universe. The Standard Model for cosmology collects this knowledge along with some other elements as cosmological distances. Thus, the link between the theory and observations is performed through some basic cosmological distances as luminosity distance D L and angular diameter distance D A . In this paper, Cosmic Lensing (CL) is presented. CL is a novel paradigm that demonstrates the inverse square law invariance within the FLRW geometry. In this way, CL reveals a new relationship between D L and D A in an expanding universe given by D L = D A (1+z) , opposed to the relation D L = D A (1+z ) 2 established about a century ago and assumed by the Standard Model. In the same sense, a compatible surface brightness vs luminosity relation -- different from the one proposed by Tolman -- is derived from Cosmic Microwave Background (CMB) equations. As a consequence, previous cosmology methods and results entrusting on luminosity as observational data must be reviewed. The expansion rate and the relative densities of the dark components of the Universe, as dark matter and dark energy, should be revised within the new paradigm.

The foundations of the Universe Expansion theory were formulated close to a century ago. Since early thirties, the Tolman surface brightness test was proposed to differentiate between static and expanding universes. According to this test, the surface brightness of astronomical sources should decrease with redshift as (1+z)^{-4}. Recently, Cosmic Lensing (CL) paradigm was presented. CL unveiled the flux focusing, an unnoticed feature of cosmological images that increase the received flux by (1+z)^2 with respect to what is expected since the test was proposed a century ago. Based on this property, Cosmic Lensing predicts a different behaviour for the surface brightness on an expanding universe decreasing as (1+z)^{-2}. In this paper, galaxy samples of two different surveys, SDSS and VIPERS, were submitted to the Tolman surface brightness test. The surface brightness μ was derived from the spectroscopic measurements in both cases. By averaging the surface brightness in redshift bins an estimation of μ(z) was obtained. μ(z) behaves close to CL predictions in a large redshift range about 0.47<z<0.8 for a uniform sample of bulge-shape galaxies, with small fluctuations mainly due to passive evolution. On the contrary, surface brightness transits far from the Stardard Model prediction in the same redshift range, being this behaviour inexplicable neither by galaxy spectral evolution nor by galaxy merging, and pointing to a fault of the model.

Physicists usually understand that physics cannot (and should not) derive that c≈3⋅ 10 8 m/s and ℏ≈1.054⋅ 10 −34 kg⋅ m 2 /s . At the same time they usually believe that physics should derive the value of the cosmological constant Λ and that the solution of the dark energy problem depends on this value. However, background space in General Relativity (GR) is only a classical notion while on quantum level symmetry is defined by a Lie algebra of basic operators. We prove that the theory based on Poincare Lie algebra is a special degenerate case of the theories based on de Sitter (dS) or anti-de Sitter (AdS) Lie algebras in the formal limit R→∞ where R is the parameter of contraction from the latter algebras to the former one, and R has nothing to do with the radius of background space. As a consequence, R is necessarily finite, is fundamental to the same extent as c and ℏ , and a question why R is as is does not arise. Following our previous publications, we consider a system of two free bodies in dS quantum mechanics and show that in semiclassical approximation the cosmological dS acceleration is necessarily nonzero and is the same as in GR if the radius of dS space equals R and Λ=3/ R 2 . This result follows from basic principles of quantum theory. It has nothing to do with existence or nonexistence of dark energy and therefore for explaining cosmological acceleration dark energy is not needed. The result is obtained without using the notion of dS background space (in particular, its metric and connection) but simply as a consequence of quantum mechanics based on the dS Lie algebra. Therefore, Λ has a physical meaning only on classical level and the cosmological constant problem and the dark energy problem do not arise.