منابع مشابه
Dark Energy from Brane-world Gravity
Recent observations provide strong evidence that the universe is accelerating. This confronts theory with a severe challenge. Explanations of the acceleration within the framework of general relativity are plagued by difficulties. General relativistic models require a “dark energy” field with effectively negative pressure. An alternative to dark energy is that gravity itself may behave differen...
متن کاملConformal Gravity: Dark Matter and Dark Energy
This short review examines recent progress in understanding dark matter, dark energy, and galactic halos using theory that departs minimally from standard particle physics and cosmology. Strict conformal symmetry (local Weyl scaling covariance), postulated for all elementary massless fields, retains standard fermion and gauge boson theory but modifies Einstein–Hilbert general relativity and the...
متن کاملDark Energy and Dark Gravity : Theory Overview
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet. Explanations of cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are nearly all based on...
متن کاملEmergent gravity and Dark Energy
Given the expansion rate of the universe in terms of the Hubble constant H0 = (ȧ/a)0, one can define a critical energy density ρc = 3H 2 0/8πG which is required to make the spatial sections of the universe compact. It is convenient to measure the energy densities of the different species, which drive the expansion of the universe, in terms of this critical density using the dimensionless parame...
متن کاملDark 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 کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Physical Review D
سال: 2018
ISSN: 2470-0010,2470-0029
DOI: 10.1103/physrevd.98.084060