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I also don't know how it can be done and what it would mean. So I looking for is anyone did it somehow with some level of success, such as no internal logical contradictions and no obvious contradictions to experiments.

I am looking for generalizations of special relativity for flat spacetime. Of course, most well known generlaization of SR is general relativty. There are many other generalizations of SR for curved spacetime. All what I found is for curved spacetime. Are any more or less successfull attempts to...

Is it possible to derive laws of Newtonian gravity from some symmetries?

Thanks! And what about width of strings? Are they one dimensional or they expected to have non zero width?

Quite a long time ago, I read about length of strings in string theory. And, if I remember correctly, expected length was in light years. I looked at Wikipedia today, and I see currently expected length of string is very small, around Plank size. Is it changed over time, or the expected length...

Thanks. And another question about same. SU(3) seems as have less number of parameters than SU(3)xSU(2)xU(1). If there is SU(3) group, is is possible to say it is compatible with SU(3)xSU(2)xU(1) because SU(3) always contains SU(2) subgroups, and SU(2) always contains U(1)?

Hi, I trying to understand. If there is non-trivial SU(3) group, is it always possible to find SU(2) as part of SU(3)? And same question about SU(2) and U(1).

I think yes, at least I studied GR in university some years ago. But I work in area not related to GR. Problem is - I have some new hypothesis not related to cosmology, and unexpectedly found it is necessary to test the hypothesis with cosmology models. Well, I think I got some ideas for my...

Dilation of time if Universe had density ##\Omega_{t1}## to case if Universe had density ##\Omega_{t2}## and same size.

I thinking how to calculate time dilation in different time with usage of average mean density. Lets set that Universe have average mean density ##\Omega_{t1}## at time t1 and ##\Omega_{t2}## at time t2. How to get time dilation, for comoving observers, between time t1 and t2?

I reading article "The Cosmological Constant and Dark Energy" P. J. E. Peebles, Bharat Ratra http://arxiv.org/abs/astro-ph/0207347 They use following sources of density: ## \Omega_{M0}+\Omega_{R0}+\Omega_{\Lambda0}+\Omega_{K0}=1## Next I see " The measurements agree with the relativistic...

Thanks. What about compatibility to SO(3) symmetry Lorentz group?

I have question, is GR compatible with SO(3)?

Thanks, seems as I used incorrect phrase for search

I know it can be done. However, such result would not be precise, because some area have lower temperature, because of night or hurricanes, some area with higher temperatues. So I guess such approach can give only order of magnitude estimation. Luminocity of Sun is described in many places...