scholarly journals Vacuum energy and the cosmological constant

2015 ◽  
Vol 30 (22) ◽  
pp. 1540033 ◽  
Author(s):  
Steven D. Bass
Keyword(s):  
Energy Density ◽  
Large Hadron Collider ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Hadron Collider ◽  
Planck Scale ◽  
Vacuum Energy Density ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The accelerating expansion of the Universe points to a small positive value for the cosmological constant or vacuum energy density. We discuss recent ideas that the cosmological constant plus Large Hadron Collider (LHC) results might hint at critical phenomena near the Planck scale.

scholarly journals Revisiting the Cosmological Constant Problem within Quantum Cosmology

Universe ◽  
2020 ◽  
Vol 6 (8) ◽  
pp. 108
Author(s):  
Vesselin Gueorguiev ◽  
Andre Maeder
Keyword(s):  
Energy Density ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Vacuum Energy ◽  
Planck Scale ◽  
Vacuum Energy Density ◽  
Characteristic Scale ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Cosmological Constant Problem

A new perspective on the Cosmological Constant Problem (CCP) is proposed and discussed within the multiverse approach of Quantum Cosmology. It is assumed that each member of the ensemble of universes has a characteristic scale a that can be used as integration variable in the partition function. An averaged characteristic scale of the ensemble is estimated by using only members that satisfy the Einstein field equations. The averaged characteristic scale is compatible with the Planck length when considering an ensemble of solutions to the Einstein field equations with an effective cosmological constant. The multiverse ensemble is split in Planck-seed universes with vacuum energy density of order one; thus, Λ˜≈8π in Planck units and a-derivable universes. For a-derivable universe with a characteristic scale of the order of the observed Universe a≈8×1060, the cosmological constant Λ=Λ˜/a2 is in the range 10−121–10−122, which is close in magnitude to the observed value 10−123. We point out that the smallness of Λ can be viewed to be natural if its value is associated with the entropy of the Universe. This approach to the CCP reconciles the Planck-scale huge vacuum energy–density predicted by QFT considerations, as valid for Planck-seed universes, with the observed small value of the cosmological constant as relevant to an a-derivable universe as observed.

A Clifford-gravity-based cosmology, dark matter and dark energy

2015 ◽  
Vol 12 (03) ◽  
pp. 1550037 ◽  
Author(s):  
Carlos Castro
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Degrees Of Freedom ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Four Dimensions ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

A Clifford-gravity-based model is exploited to build a generalized action (beyond the current ones used in the literature) and arrive at relevant numerical results which are consistent with the presently-observed de Sitter accelerating expansion of the universe driven by a very small vacuum energy density ρ obs ~ 10-120(MP)4 (MP is the Planck mass) and provide promising dark energy/matter candidates in terms of the 16 scalars corresponding to the degrees of freedom associated with a Cl (3, 1)-algebra-valued scalar field Φ in four dimensions.

QUANTUM ANALYSIS FOR THE EVOLUTION OF THE COSMOLOGICAL CONSTANT VIA UNITARY TRANSFORMATION

2007 ◽  
Vol 16 (07) ◽  
pp. 1119-1132 ◽  
Author(s):  
JEONG RYEOL CHOI
Keyword(s):  
Energy Density ◽  
Cosmological Constant ◽  
Unitary Transformation ◽  
Vacuum Energy ◽  
Background Radiation ◽  
Vacuum Energy Density ◽  
First Case ◽  
Special Cases ◽  
Reheating Process ◽  
The Universe

The expectation value of the vacuum energy density tied to the cosmological constant is derived from the non-relativistic quantum description of the reheating process using the unitary transformation method. Our research is performed for two special cases, i.e. under the assumption of two different duration terms for the radiation-dominated era. We suppose that the radiation-dominated era lasted for 3,000 years in the first case, and for a very short time so that it can be ignored in the other case. For the former case, the resulting present cosmological constant is much higher than the previously known one. However, for the latter case, it is in good agreement with that obtained from recent cosmic microwave background radiation measurements. Hence, we cannot exclude the possibility that the change of the universe from the radiation-dominated era to the matter-dominated era might have progressed very swiftly after the beginning of reheating. The analysis shows that the vacuum energy density has been dissipated by the nonconservative force acting on the coherent oscillations of the scalar field according to the expansion of the universe.

scholarly journals Revolutionary Approach for Fusion of the Classic, Relativity and Quantum field Theories: Sayed’s Acceleration Equation and Probable Violation of E=mc2

2021 ◽  
Vol 19 ◽  
pp. 134-141
Author(s):  
Sayed A. El-Mongy
Keyword(s):  
Cosmological Constant ◽  
Planck Scale ◽  
Accelerated Expansion ◽  
Vacuum Energy Density ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Field Equations ◽  
Expansion Of The Universe ◽  
Atom Nucleus ◽  
The Universe

Expansion of the universe is a divine fact in the glorious Quran. The accelerated expansion of the universe is one of the physics mysteries and challenges. This article is a try to find an answer to this ambiguity. A simple fusion and merging of the Newton, Einstein and quantum field equations were carried out to clarify this topic. Innovative equations correlating the acceleration (As), cosmological constant (Ʌ), vacuum energy density (ρ) and distance (d) was deduced. It can be concluded that Sayed`s acceleration constant (As) is proportional to (Ʌ/ρ), (1/8mc2) and (1/πd2). The derivative equation reveals a probable violation of the mass-energy formula (E= mc2); the speed of light might be 12.5% more. This disparity may be due to antimatter contribution; neutrino-antineutrino, β-β+ annihilation and/or a predicted unrecognized very light particle in the atom nucleus. The Sayed`s acceleration constant (As) and (As/Ʌ) ratio were calculated and found to be 6.33825x10-8 m/s2 and 5.7620475x10+44 m3/s2 respectively. Using Sayed`s equations, the calculated acceleration in planck scale is matched with the declared 5.56081x1051 m/s2 value. The The calculated recession velocity at 1 Mpc was found to be 6.5192677 x 108 m/s .and the cosmological constant (Ʌ) is as measured;~1.1x10-52 m-2

scholarly journals ON TOPOLOGICAL DEFECTS AND COSMOLOGICAL CONSTANT

2014 ◽  
Vol 29 (01) ◽  
pp. 1450007 ◽  
Author(s):  
B. RAYCHAUDHURI ◽  
F. RAHAMAN ◽  
M. KALAM
Keyword(s):  
Cosmological Constant ◽  
Vacuum Energy ◽  
Ad Hoc ◽  
Topological Defects ◽  
Field Equations ◽  
Theoretical Support ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

Einstein introduced cosmological constant in his field equations in an ad hoc manner. Cosmological constant plays the role of vacuum energy of the universe which is responsible for the accelerating expansion of the universe. To give a theoretical support, it remains an elusive goal to modern physicists. We provide a prescription to obtain cosmological constant from the phase transitions of the early universe when topological defects, namely monopole might have existed.

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

scholarly journals Do we come from a quantum anomaly?

2019 ◽  
Vol 28 (14) ◽  
pp. 1944002 ◽  
Author(s):  
Spyros Basilakos ◽  
Nick E. Mavromatos ◽  
Joan Solà Peracaula
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Hubble Parameter ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Quantum Anomaly ◽  
Inflationary Phase ◽  
Axion Field ◽  
The Universe

We present a string-based picture of the cosmological evolution in which (CP-violating) gravitational anomalies acting during the inflationary phase of the universe cause the vacuum energy density to “run” with the effective Hubble parameter squared, [Formula: see text], thanks to the axion field of the bosonic string multiplet. This leads to baryogenesis through leptogenesis with massive right-handed neutrinos. The generation of chiral matter after inflation helps in cancelling the anomalies in the observable radiation- and matter-dominated eras. The present era inherits the same “running vacuum” structure triggered during the inflationary time by the axion field. The current dark energy is thus predicted to be mildly dynamical, and dark matter should be made of axions. Paraphrasing Carl Sagan [ https://www.goodreads.com/author/quotes/10538.Carl_Sagan .]: we are all anomalously made from starstuff.

BLACK HOLE QUANTIZATION, THERMODYNAMICS AND COSMOLOGICAL CONSTANT

2004 ◽  
Vol 13 (05) ◽  
pp. 885-898
Author(s):  
LI XIANG
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Planck Scale ◽  
Additional Term ◽  
Logarithmic Correction ◽  
De Sitter ◽  
Horizon Area ◽  
Constant Distance ◽  
The Universe

Bekenstein argues that the horizon area of a black hole has a constant distance spectrum. We investigate the effects of such a discrete spectrum on the thermodynamics of a Schwarzchild black hole (SBH) and a Schwarzchild–de Sitter black hole (SdBH), in terms of the time-energy uncertainty relation and Stefan–Boltzman law. For the massive SBH, a negative and logarithmic correction to the Bekenstein–Hawking entropy is obtained, as well as other authors by using other methods. As to the minimal hole near the Planck scale, its entropy is no longer proportional to the horizon area, but is of order of the mass of the hole. This is similar to an excited stringy state. The vanishing heat capacity of such a minimal black hole implies that it may be a remnant as the ground state of the evaporating hole. The properties of a SdBH are similar to the SBH, except for an additional term of square area associated with the cosmological constant. In order to maintain the validity of the Bekenstein–Hawking formula, the cosmological constant is strongly limited by the size of the biggest black hole in the universe. A relation associated with the cosmological constant, Planck area and the Stefan–Boltzman constant is obtained. The cosmological constant is not only related to the vacuum energy, but is also related to the thermodynamics.

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