منابع مشابه
Dark energy versus modified gravity.
There is now strong observational evidence that the expansion of the Universe is accelerating. The standard explanation invokes an unknown "dark energy" component. But such scenarios are faced with serious theoretical problems, which has led to increased interest in models where instead general relativity is modified in a way that leads to the observed accelerated expansion. The question then a...
متن کاملDark Energy and Modified Gravity
Explanations of the late-time cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are mostly based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but all share one feature in common – an inability to account for the gravitational properties of the vacuum energy, and a failure t...
متن کاملCosmological Acceleration: Dark Energy or Modified Gravity?
The recently observed accelerating cosmological expansion or ”dark energy” may be either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity) without any constituent Dark Energy. Lowor high-curvature modifications of Einstein gravity are distinguished by the spacetime (Ricci) curvature of their vacua. If constituent Dark Energy does not exist, s...
متن کاملModified gravity, Dark Energy and MOND
We propose a class of actions for the spacetime metric that introduce corrections to the Einstein-Hilbert Lagrangian depending on the logarithm of some curvature scalars. We show that for some choices of these invariants the models are ghost free and modify Newtonian gravity below a characteristic acceleration scale given by a0 = cμ, where c is the speed of light and μ is a parameter of the mod...
متن کاملDifferentiating between Modified Gravity and Dark Energy
The nature of the fuel that drives today’s cosmic acceleration is an open and tantalizing mystery. We entertain the suggestion that the acceleration is not the manifestation of yet another new ingredient in the cosmic gas tank, but rather a signal of our first real lack of understanding of gravitational physics. By requiring that the underlying gravity theory respects Birkhoff’s law, we derive ...
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ژورنال
عنوان ژورنال: General Relativity and Gravitation
سال: 2017
ISSN: 0001-7701,1572-9532
DOI: 10.1007/s10714-017-2276-x