Every time a major news story about dark matter and/or dark energy comes out, like the recent release of data from the Dark Energy Survey, I also come across articles and links about alternative theories to the 'dark' stuff, like MOND (Modified Newtonian Dynamics).....
When I typed Modified General Relativity into Google, this paper came up twice, near the top:
Subjects: General Relativity and Quantum Cosmology (gr-qc) Journal reference: Gen Relativ Gravit (2019) 51: 53 DOI: 10.1007/s10714-019-2537-y, https://arxiv.org/abs/1904.10803 Author: Gary Nash
Here's the gist:
An orthogonal decomposition of symmetric tensors can be constructed in terms of the Lie derivative along $X$ of the metric and a product of the unit vectors; and a linear sum of divergenceless symmetric tensors. A modified Einstein equation of general relativity is then obtained by using the principle of least action, the decomposition and a fundamental postulate of general relativity. The decomposition introduces a new symmetric tensor $\Phi_{\alpha\beta}$ which describes the energy-momentum of the gravitational field. It completes Einstein's equation and addresses the energy localization problem.
Not that understand everything in this paper, but I've never heard of the 'energy localization problem'.
What is the 'energy localization problem' with general relativity?