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Accelerated universe with a traversable wormhole from Visser's massive gravity
El-Nabulsi Rami Ahmad 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.1
In this letter, the Friedmann–Robertson–Walker model with a traversable wormhole is considered from the view point of Visser’s massive gravity theory. If the matter in the universe is assumed to be divided into two parts, the cosmic part, which depends on time only, and the wormhole part which depends on space only, a late-time acceleratedly expanding universe with a traversable wormhole and dominated by phantom energy is obtained.
El-Nabulsi Rami Ahmad 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.4
We present a new viable modified theory of gravity in which the matter sector is characterized by a logarithmic Lagrangian density. The modified Einstein’s field equations are derived, and they are characterized by the emergence of an effective gravitational coupling constant and an effective negative cosmological constant both coupled to the Lagrangian of matter. Applied to the Friedmann-Robertson-Walker cosmological framework, it leads to motivating phenomenology. In particular, the universe is free from the initial singularity, and a unified description of the early inflationary phase, the succeeding non-accelerating, matter-dominated expansion, and then the transition to a late-time accelerating phase is obtained as well. Moreover, the effective dark energy sector can be quintessence, yet the universe starts contracting if the phantom divide-line is crossed. The model is confronted with observations that agree with recent astronomical data. Moreover, the model gives rise to Einstein’s field equations which resemble the equations obtained in unimodular gravity.
Wormholes in Higher Dimensions with Non-Linear Curvature Terms from Quantum Gravity Corrections
Ahmad Rami El-Nabulsi 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.5
In this work, we discuss a 7-dimensional universe in the presence of a static traversable wormhole and a decaying cosmological constant and dominated by higher-order curvature effects expected from quantum gravity corrections. We confirmed the existence of wormhole solutions in the form of the Lovelock gravity. Many interesting and attractive features are discussed in some detail.