scholarly journals Cosmological evolution and dark energy in osculating Barthel–Randers geometry

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Rattanasak Hama ◽  
Tiberiu Harko ◽  
Sorin V. Sabau ◽  
Shahab Shahidi
Keyword(s):  
Particle Creation ◽  
Arbitrary Point ◽  
Energy Balance Equation ◽  
Point Of View ◽  
Cosmological Evolution ◽  
Irreversible Processes ◽  
De Sitter ◽  
Satisfactory Description ◽  
Effective Cosmological Constant ◽  
Riemann Metric

AbstractWe consider the cosmological evolution in an osculating point Barthel–Randers type geometry, in which to each point of the space-time manifold an arbitrary point vector field is associated. This Finsler type geometry is assumed to describe the physical properties of the gravitational field, as well as the cosmological dynamics. For the Barthel–Randers geometry the connection is given by the Levi-Civita connection of the associated Riemann metric. The generalized Friedmann equations in the Barthel–Randers geometry are obtained by considering that the background Riemannian metric in the Randers line element is of Friedmann–Lemaitre–Robertson–Walker type. The matter energy balance equation is derived, and it is interpreted from the point of view of the thermodynamics of irreversible processes in the presence of particle creation. The cosmological properties of the model are investigated in detail, and it is shown that the model admits a de Sitter type solution, and that an effective cosmological constant can also be generated. Several exact cosmological solutions are also obtained. A comparison of three specific models with the observational data and with the standard $$\Lambda $$ Λ CDM model is also performed by fitting the observed values of the Hubble parameter, with the models giving a satisfactory description of the observations.

scholarly journals Particle creation in global de Sitter space: Bulk space consideration

2015 ◽  
Vol 24 (07) ◽  
pp. 1550052 ◽  
Author(s):  
M. Reza Tanhayi
Keyword(s):  
Plane Wave ◽  
Massive Particle ◽  
Particle Creation ◽  
Flat Space ◽  
De Sitter Space ◽  
Point Of View ◽  
Theoretical Point ◽  
De Sitter ◽  
Field Equations ◽  
Higher Spin

Recently in [P. R. Anderson and E. Mottola, Phys. Rev. D 89 (2014) 104039, arXiv:1310.1963 [gr-qc] and P. R. Anderson and E. Mottola, Phys. Rev. D 89 (2014) 104038, arXiv:1310.0030 [gr-qc].], it was shown that global de Sitter space is unstable even to the massive particle creation with no self-interactions. In this paper, we study the instability by making use of the coordinate-independent plane wave in de Sitter space. Within this formalism, we show that the previous results of instability of de Sitter space due to the particle creation can be generalized to higher-spin fields in a straightforward way. The so-called plane wave is defined globally in de Sitter space and de Sitter invariance is manifest since such modes are deduced from the group theoretical point of view by means of the Casimir operators. In fact, we employ the symmetry of embedding space namely the 4 + 1-dimensional flat space to write the field equations and the solutions can be obtained in terms of the plane wave in embedding space.

scholarly journals Superheavy dark matter in $$R+R^2$$ cosmology with conformal anomaly

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
E. V. Arbuzova ◽  
A. D. Dolgov ◽  
R. S. Singh
Keyword(s):  
Dark Matter ◽  
Coupling Strength ◽  
Modified Gravity ◽  
Particle Creation ◽  
Cosmological Evolution ◽  
Particle Mass ◽  
Conformal Anomaly ◽  
Gauge Bosons ◽  
Superheavy Dark Matter

AbstractCosmological evolution and particle creation in $$R^2$$ R 2 -modified gravity are considered for the case of the dominant decay of the scalaron into a pair of gauge bosons due to conformal anomaly. It is shown that in the process of thermalization superheavy dark matter with the coupling strength typical for the GUT SUSY can be created. Such dark matter would have the proper cosmological density if the particle mass is close to $$10^{12}$$ 10 12 GeV.

scholarly journals Extremal Cosmological Black Holes in Horndeski Gravity and the Anti-Evaporation Regime

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 210
Author(s):  
Ismael Ayuso ◽  
Diego Sáez-Chillón Gómez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Linear Order ◽  
Scalar Tensor Theory ◽  
De Sitter ◽  
Tensor Theory ◽  
Effective Cosmological Constant ◽  
Cosmological Black Holes ◽  
Extremal Black Holes

Extremal cosmological black holes are analysed in the framework of the most general second order scalar-tensor theory, the so-called Horndeski gravity. Such extremal black holes are a particular case of Schwarzschild-De Sitter black holes that arises when the black hole horizon and the cosmological one coincide. Such metric is induced by a particular value of the effective cosmological constant and is known as Nariai spacetime. The existence of this type of solutions is studied when considering the Horndeski Lagrangian and its stability is analysed, where the so-called anti-evaporation regime is studied. Contrary to other frameworks, the radius of the horizon remains stable for some cases of the Horndeski Lagrangian when considering perturbations at linear order.

The Airlines’ Point of View

1963 ◽  
Vol 67 (632) ◽  
pp. 519-522
Author(s):  
Henry Marking
Keyword(s):  
Good Deal ◽  
Special Problem ◽  
Point Of View ◽  
Air Transport ◽  
Satisfactory Description ◽  
Surface Transport ◽  
Special Rules

My Talk will be Brief because Mr. Kean has covered the field extensively and extremely well.What is Interchange? Mr. Kean indicated that it is not a very satisfactory description of what takes place because it is not a word which describes it accurately, and I think a good deal of confusion about interchange exists in the minds of many laymen because, unlike most air transport words which had their roots in surface transport, interchange so far as I know is peculiar to air transport; hence people are apt to think that it is something special, and that special rules must apply to it. In fact I suggest that it is nothing of the kind; all it is is a certain kind of charter, and the same rules apply to interchange of aircraft as to any other kind of charter, and the reason that it has been singled out as a special problem for lawyers is that its characteristics make it extremely difficult to work satisfactorily, internationally particularly, if the normal rules are applied.

scholarly journals ON DETERMINATION OF THE GEOMETRIC COSMOLOGICAL CONSTANT FROM THE OPERA EXPERIMENT OF SUPERLUMINAL NEUTRINOS

2012 ◽  
Vol 27 (11) ◽  
pp. 1250041 ◽  
Author(s):  
MU-LIN YAN ◽  
SEN HU ◽  
WEI HUANG ◽  
NENG-CHAO XIAO
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Fundamental Constant ◽  
Zero Point ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Point Energy ◽  
Sitter Spacetime ◽  
Effective Cosmological Constant

The recent OPERA experiment of superluminal neutrinos has deep consequences in cosmology. In cosmology a fundamental constant is the cosmological constant. From observations one can estimate the effective cosmological constant Λ eff which is the sum of the quantum zero point energy Λ dark energy and the geometric cosmological constant Λ. The OPERA experiment can be applied to determine the geometric cosmological constant Λ. It is the first study to distinguish the contributions of Λ and Λ dark energy from each other by experiment. The determination is based on an explanation of the OPERA experiment in the framework of Special Relativity with de Sitter spacetime symmetry.

Particle creation in de Sitter space

1985 ◽  
Vol 31 (4) ◽  
pp. 754-766 ◽  
Author(s):  
E. Mottola
Keyword(s):  
Particle Creation ◽  
De Sitter Space ◽  
De Sitter

scholarly journals The Glass Transition Within the Thermodynamics of Irreversible Processes

1998 ◽  
Vol 53 (3-4) ◽  
pp. 157-170
Author(s):  
H. Baur
Keyword(s):  
Glass Transition ◽  
Cooling Rate ◽  
Dissipative Process ◽  
Point Of View ◽  
Clear Distinction ◽  
Irreversible Processes ◽  
Free Enthalpy ◽  
Thermodynamics Of Irreversible Processes ◽  
Non Linear ◽  
Phenomenological Point

Abstract The glass transition caused by a finite cooling rate is a continuous non-linear dissipative process whose description requires a clear distinction between equilibrium and non-equilibrium quantities. The so-called Davies or Prigogine-Defay relations (in form of an equation as well as in form of an inequality) are not relevant in such a process. The determining quantities of the glass transition are -from a macroscopic phenomenological point of view -the fluidity of the melt and the partial free enthalpy of the microscopic vacancies in the melt. All of the characteristics of the dynamics of the glass transition are essentially due to these two quantities.

On spacelike curves in hyperbolic space times sphere

2014 ◽  
Vol 11 (03) ◽  
pp. 1450014 ◽  
Author(s):  
Lingling Kong ◽  
Donghe Pei
Keyword(s):  
Hyperbolic Space ◽  
Height Function ◽  
Point Of View ◽  
De Sitter ◽  
Height Functions ◽  
Geometric Point

The main goal of this paper is to study singularities of lightlike surfaces and focal surfaces of spacelike curves in Hyperbolic space times sphere. To do that, we construct a de Sitter height function and a Lightcone height function, and then show the relation between singularities of the lightlike surfaces (respectively, the focal surfaces) and that of the de Sitter height functions (respectively, the Lightcone height functions). In addition, some geometry properties of the spacelike curves are studied from geometric point of view.

scholarly journals Cosmology of cubic galileon in modified teleparallel gravity

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Hamza Boumaza
Keyword(s):  
Growth Rate ◽  
Equations Of Motion ◽  
Cosmological Parameters ◽  
Teleparallel Gravity ◽  
Cosmological Evolution ◽  
De Sitter ◽  
Dynamical Equations ◽  
Proposed Model ◽  
Best Fit ◽  
Friedmann Robertson Walker

AbstractIn this present paper, we study the cosmological evolution of the cubic galileon along with modified teleparallel gravity at perturbed and non-perturbed levels. We show the dynamical equations of motion and investigate the evolution of different cosmological parameters by using the dynamical variables analysis. In addition, a detailed analysis of different cosmological evolution in the matter, radiation and de Sitter eras is presented by solving the dynamical equations numerically. In our analysis, we find that the equations of motion in the Friedmann–Robertson–Walker (FRW) background metric is characterized by a stable de Sitter era and a tracker solution in which $$H{\dot{\varphi }}$$ H φ ˙ is always constant. We find also that the equation of state of dark energy associated to the proposed model in this work can deviate from − 2 at the matter era. Moreover, the conditions of avoiding ghost and Laplacian instabilities in our model are derived; then we show that the model is free of these instabilities. Furthermore we place an observational constraint on the parameters of the model through Monte Carlo numerical method using growth rate and observational Hubble data. Finally, using the best-fit values of parameters in the model we compare our growth rate of matter perturbation with the prediction of $$\varLambda $$ Λ CDM model and the latest measurement.

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