scholarly journals On the value of the cosmical constant

1931 ◽  
Vol 133 (822) ◽  
pp. 605-615 ◽  
Keyword(s):  
Wave Equation ◽  
Equations Of Motion ◽  
Geometrical Interpretation ◽  
De Sitter ◽  
Astronomical Observations ◽  
Alternative Expression ◽  
Scattering Force ◽  
Expansion Of The Universe ◽  
The Universe

1. The cosmical constant λ occurs in Einstein’s law of gravitation G μv = λ g μv . In the resulting equations of motion the term containing λ represents a scattering force which tends to make all very remote bodies recede from one another; this phenomenon is the basis of the theories of de Sitter and Lemaître concerning the “expansion of the universe.” If the observed recession of the spiral nebulæ is a manifestation of this effect the value of λ can be found from the astronomical observations. In this paper I put forward a simple geometrical interpretation of the term in the wave equation which contains the mass m of an electron; this interpretation provides an alternative expression for the term. The new expression involves λ, and by equating it to the ordinary expression we find a theoretical value of λ, viz., 9⋅8.10 -55 cm. -2 . This agrees satisfactorily with the value found from the observed recession of the spiral nebulae (8).

scholarly journals PRIMORDIAL BLACK HOLE FORMATION FROM INFLATON

2000 ◽  
Vol 09 (06) ◽  
pp. 705-710 ◽  
Author(s):  
XIN HE MENG ◽  
BIN WANG ◽  
S. FENG
Keyword(s):  
Black Hole ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
De Sitter ◽  
Hole Formation ◽  
Black Hole Formation ◽  
Expansion Of The Universe ◽  
Slow Rolling ◽  
The Relationship ◽  
The Universe

Measurements of the distances to SNe Ia have produced strong evidence that the expansion of the Universe is really accelarating, implying the existence of a nearly uniform component of dark energy with the simplest explanation as a cosmological constant. In this paper a small changing cosmological term is proposed, which is a function of a slow-rolling scalar field, by which the de Sitter primordial black holes' properties, for both charged and uncharged cases, are carefully examined and the relationship between the black hole formation and the energy transfer of the inflaton is eluciated. The criterion for primordial black hole formation is given.

scholarly journals CAN THE EXISTENCE OF DARK ENERGY BE DIRECTLY DETECTED?

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3426-3436 ◽  
Author(s):  
MARTIN L. PERL
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Energy Density ◽  
Total Mass ◽  
Mass Density ◽  
Mass Energy ◽  
Dark Energy Density ◽  
Astronomical Observations ◽  
Expansion Of The Universe ◽  
The Universe

Over the last decade, astronomical observations show that the acceleration of the expansion of the universe is greater than expected from our understanding of conventional general relativity, the mass density of the visible universe, the size of the visible universe and other astronomical measurements. The additional expansion has been attributed to a variety of phenomenon that have been given the general name of dark energy. Dark energy in the universe seems to comprise a majority of the energy in the visible universe amounting to about three times the total mass energy. But locally the dark energy density is very small. However it is not zero. In this paper I describe the work of others and myself on the question of whether dark energy density can be directly detected. This is a work-in-progress and I have no answer at present.

scholarly journals A novel teleparallel dark energy model

2016 ◽  
Vol 25 (02) ◽  
pp. 1650025 ◽  
Author(s):  
Giovanni Otalora
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Teleparallel Gravity ◽  
Accelerated Expansion ◽  
Late Time ◽  
De Sitter ◽  
Sitter Group ◽  
Current State ◽  
Expansion Of The Universe ◽  
The Universe

Although equivalent to general relativity, teleparallel gravity (TG) is conceptually speaking a completely different theory. In this theory, the gravitational field is described by torsion, not by curvature. By working in this context, a new model is proposed in which the four-derivative of a canonical scalar field representing dark energy is nonminimally coupled to the “vector torsion”. This type of coupling is motivated by the fact that a scalar field couples to torsion through its four-derivative, which is consistent with local spacetime kinematics regulated by the de Sitter group [Formula: see text]. It is found that the current state of accelerated expansion of the universe corresponds to a late-time attractor that can be (i) a dark energy-dominated de Sitter solution ([Formula: see text]), (ii) a quintessence-type solution with [Formula: see text], or (iii) a phantom-type [Formula: see text] dark energy.

Rotation as a Source of Accelerating Expansion of the Universe

2021 ◽  
Author(s):  
Andrzej Szummer
Keyword(s):  
Gravitational Force ◽  
Cosmological Parameters ◽  
Classical Mechanics ◽  
Astronomical Observations ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Difference ◽  
Changes Over Time ◽  
The Universe ◽  
Over Time

Abstract Assuming a hypothesis, that the universe is rotating from the very beginning – as soon as it appeared- creates new possibilities to explain accelerating expansion of the universe. A spinning universe is under the action of two enormous forces: gravitational force and centrifugal force. The difference between the two forces has been shown to give the resultant force that causes the expansion of the universe to accelerate. Applying classical mechanics as a method, I calculated the magnitude of this acceleration, the time when it appeared and how it changes over time. By applying only recognized cosmological parameters, interesting results were obtained that can be checked with astronomical observations. The presence of acceleration of expansion causes the rate of expansion of the universe to continue to increase, which is consistent with astronomical observations. However, the speed of this increase in the rate of expansion becomes slower over time.

Galileon inflation field with three dark eras of the universe

2020 ◽  
Vol 29 (10) ◽  
pp. 2050071
Author(s):  
A. I. Keskin
Keyword(s):  
Equations Of Motion ◽  
Vacuum State ◽  
Kinetic Term ◽  
Second Phase ◽  
De Sitter ◽  
Third Phase ◽  
Standard Cosmology ◽  
Slow Roll ◽  
Friction Term ◽  
The Universe

In this paper, we discuss possible three early eras of the universe in the theoretical context of the Galilean cosmology. The first phase is a slow-roll inflation phase in which the friction term in the equations of motion dominates over the kinetic term. This is the initial vacuum state leading to quasi-de Sitter expansion. The second phase is where the cosmological perturbations are supposed to be generated. In this phase, the friction term is supposed to be negligible which leads to the appearance of the Galileon inflation field. The third phase is the reheating phase in the standard cosmology, where the oscillations of a canonical scalar field in the model lead to this phase. These three eras for the early universe are shown by a single master equation of the theory. However, we compute observational indices (the scalar spectral index parameter and the tensor-to-scalar ratio) for the era where the era that the perturbations are produced. Finally, we compare viability of the theoretical findings with the latest Planck observational data.

scholarly journals The Discovery of the Expansion of the Universe

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 132
Author(s):  
Øyvind Grøn
Keyword(s):  
De Sitter ◽  
Historical Evidence ◽  
General Acceptance ◽  
Expansion Of The Universe ◽  
Edwin Hubble ◽  
The Universe

Alexander Friedmann, Carl Wilhelm Wirtz, Vesto Slipher, Knut E. Lundmark, Willem de Sitter, Georges H. Lemaître, and Edwin Hubble all contributed to the discovery of the expansion of the universe. If only two persons are to be ranked as the most important ones for the general acceptance of the expansion of the universe, the historical evidence points at Lemaître and Hubble, and the proper answer to the question, “Who discovered the expansion of the universe?”, is Georges H. Lemaître.

scholarly journals Primordial Dark Energy from a Condensate of Spinors in a 5D Vacuum

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Pablo Alejandro Sánchez ◽  
Mauricio Bellini
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Inflationary Universe ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Dark Energy Density ◽  
Sitter Spacetime ◽  
Interesting Candidate ◽  
Expansion Of The Universe ◽  
The Universe

We explore the possibility that the expansion of the universe can be driven by a condensate of spinors which are free of interactions in a 5D relativistic vacuum defined in an extended de Sitter spacetime which is Riemann flat. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective 4D (inflationary) de Sitter expansion which describes an inflationary universe. We found that the condensate of spinors studied here could be an interesting candidate to explain the presence of dark energy in the early universe. The dark energy density which we are talking about is poured into smaller subhorizon scales with the evolution of the inflationary expansion.

scholarly journals THE WARPING OF EXTRA SPACES ACCELERATES THE EXPANSION OF THE UNIVERSE

2010 ◽  
Vol 19 (14) ◽  
pp. 2281-2287 ◽  
Author(s):  
ISHWAREE P. NEUPANE
Keyword(s):  
Dimensional Space ◽  
Space Time ◽  
De Sitter ◽  
Four Dimensions ◽  
Accelerating Expansion ◽  
Higher Dimensional ◽  
Dimensional Space Time ◽  
Expansion Of The Universe ◽  
Theories Of Gravity ◽  
The Universe

Generic cosmological models derived from higher-dimensional theories with warped extra-dimensions have a nonzero cosmological constant-like term induced on the 3 + 1 space–time, or a physical three-brane. In the scenario where this 3 + 1 space–time is an inflating de Sitter "bran" embedded in a higher-dimensional space–time, described by warped geometry, the four-dimensional cosmological term is determined in terms of two length scales: one is a scale associated with the size of extra-dimension(s) and the other is a scale associated with the warping of extra-space(s). The existence of this term in four dimensions provides a tantalizing possibility of explaining the observed accelerating expansion of the universe from fundamental theories of gravity, e.g. string theory.

scholarly journals Does holographic equipartition demand a pure cosmological constant?

2020 ◽  
pp. 2050334
Author(s):  
P. B. Krishna ◽  
Titus K. Mathew
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Dark Energy Model ◽  
State Parameter ◽  
De Sitter ◽  
Entropy Maximization ◽  
Expansion Of The Universe ◽  
The Law ◽  
De Sitter Universe ◽  
The Universe

The spacial expansion of the universe could be described as a tendency for satisfying holographic equipartition which inevitably demands the presence of dark energy. We explore whether this novel idea proposed by Padmanabhan gives any additional insights into the nature of dark energy. In particular, we obtain the constraints imposed by the law of emergence on the equation of state parameter, [Formula: see text]. We also present a thermodynamic motivation for the obtained constraints on [Formula: see text]. Further, we explicitly prove the feasibility of describing a dynamic dark energy model through the law of emergence. Interestingly, both holographic equipartition and the entropy maximization demand an asymptotically de Sitter universe with [Formula: see text], rather than a pure cosmological constant.

scholarly journals Gravitation with Cosmological Term, Expansion of the Universe as Uniform Acceleration in Clifford Coordinates

2021 ◽  
Author(s):  
Alexander Kritov
Keyword(s):  
Clifford Algebra ◽  
Cosmological Term ◽  
Two Dimensional ◽  
De Sitter ◽  
Time Coordinate ◽  
Dimensional Spacetime ◽  
Expansion Of The Universe ◽  
Sitter Model ◽  
The Universe ◽  
De Sitter Model

The paper briefly reviews the Clifford algebras of space Cl(3,0) and anti-space Cl(0,3) with a particular focus on the paravector representation, emphasizing the fact that both algebras have an isomorphic center represented just by two coordinates. Since the paravector representation allows assigning the scalar element of grade 0 to the time coordinate, we consider the relativity in such two-dimensional spacetime for a uniformly accelerated frame with the constant acceleration 3Hc. Using the Rindler coordinate transformations in two-dimensional spacetime and then applying it to Minkowski coordinates, we obtain the FLRW metric, which in the case of the Clifford algebra of space Cl(3,0) corresponds to the anti-de Sitter (AdS) flat (k=0) case, the negative cosmological term and an oscillating model of the universe. The approach with anti-Euclidean Clifford algebra Cl(0,3) leads to the de Sitter model with the positive cosmological term and the exact form of the scale factor used in modern cosmology.

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