scholarly journals Gravitational entropy of cosmic expansion

2014 ◽  
Vol 335 (6-7) ◽  
pp. 587-592 ◽  
Author(s):  
R. A. Sussman
Keyword(s):  
Cosmic Expansion ◽  
Gravitational Entropy

scholarly journals Cosmic expansion from boson and fermion fields

2011 ◽  
Vol 28 (12) ◽  
pp. 125006 ◽  
Author(s):  
Rudinei C de Souza ◽  
Gilberto M Kremer
Keyword(s):  
Cosmic Expansion ◽  
Fermion Fields

Missing energy and cosmic expansion

Nature ◽  
1996 ◽  
Vol 382 (6594) ◽  
pp. 768-768 ◽  
Author(s):  
Paul J. Steinhardt
Keyword(s):  
Missing Energy ◽  
Cosmic Expansion

The cooperation between loop quantum gravity and Entropic gravity

2021 ◽  
Author(s):  
Wen-Xiang Chen
Keyword(s):  
Boundary Condition ◽  
Quantum Gravity ◽  
Gravitational Potential ◽  
Complex Number ◽  
Loop Quantum Gravity ◽  
Gravitational Entropy ◽  
Entropic Gravity ◽  
New Form

In this paper, we show that bosons can produce bochromatic condensation without an energy layer when the boundary condition $\frac{T}{T_{c}}=z$(when z is complex) is preset. $r_{R}=zr_{A}\left(1-\frac{v^{2}}{c^{2}}\right)^{\frac{1}{2}}$(when z is A complex number). A new form of gravitational potential is obtained by combining the theory of gravitational entropy with loop quantum gravity.

scholarly journals Can accelerated expansion of the universe be due to spacetime vorticity?

2018 ◽  
Vol 33 (40) ◽  
pp. 1850240
Author(s):  
Babur M. Mirza
Keyword(s):  
Magnetic Field ◽  
Accelerated Expansion ◽  
Newtonian Gravity ◽  
Hubble’S Parameter ◽  
Cosmic Expansion ◽  
Zero Curvature ◽  
Expansion Of The Universe ◽  
General Relativistic ◽  
The Universe ◽  
The Magnetic Field

We present here a general relativistic mechanism for accelerated cosmic expansion and the Hubble’s parameter. It is shown that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one another at a rate equal to the Hubble’s constant. We therefore predict an oscillatory universe, with zero curvature, without assuming violation of Newtonian gravity at large distances or invoking dark energy/dark matter hypotheses. The value of the Hubble’s constant, along with the scale of expansion, as well as the high isotropy of CMB radiation are deduced from the model.

scholarly journals Testing the Vainshtein mechanism using stars and galaxies

2015 ◽  
Vol 24 (12) ◽  
pp. 1544021 ◽  
Author(s):  
Jeremy Sakstein ◽  
Kazuya Koyama
Keyword(s):  
General Relativity ◽  
Solar System ◽  
Main Sequence ◽  
Alternative Theories Of Gravity ◽  
The Novel ◽  
Main Sequence Stars ◽  
Cosmic Expansion ◽  
Astrophysical Objects ◽  
Theories Of Gravity ◽  
Alternative Theories

The Vainshtein mechanism is of paramount importance in many alternative theories of gravity. It hides deviations from general relativity (GR) in the solar system while allowing them to drive the acceleration of the cosmic expansion. Recently, a class of theories have emerged where the mechanism is broken inside astrophysical objects. In this essay, we look for novel probes of these theories by deriving the modified properties of stars and galaxies. We show that main-sequence stars are colder, less luminous and more ephemeral than GR predicts. Furthermore, the circular velocities of objects orbiting inside galaxies are slower and the lensing of light is weaker. We discuss the prospects for testing these theories using the novel phenomena presented here in light of current astrophysical surveys.

scholarly journals Stability of the Regular Hayward Thin-Shell Wormholes

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
M. Sharif ◽  
Saadia Mumtaz
Keyword(s):  
Black Hole ◽  
Thin Shell ◽  
Energy Conditions ◽  
Stability Conditions ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Cosmic Expansion ◽  
Stress Energy ◽  
Thin Shell Wormholes ◽  
The Stability

The aim of this paper is to construct regular Hayward thin-shell wormholes and analyze their stability. We adopt Israel formalism to calculate surface stresses of the shell and check the null and weak energy conditions for the constructed wormholes. It is found that the stress-energy tensor components violate the null and weak energy conditions leading to the presence of exotic matter at the throat. We analyze the attractive and repulsive characteristics of wormholes corresponding toar>0andar<0, respectively. We also explore stability conditions for the existence of traversable thin-shell wormholes with arbitrarily small amount of fluid describing cosmic expansion. We find that the space-time has nonphysical regions which give rise to event horizon for0<a0<2.8and the wormhole becomes nontraversable producing a black hole. The nonphysical region in the wormhole configuration decreases gradually and vanishes for the Hayward parameterl=0.9. It is concluded that the Hayward and Van der Waals quintessence parameters increase the stability of thin-shell wormholes.

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