B Current status of Horava Lifshitz gravity?

[windy miller]

Many years I read a lay person friendly article on Horava Lifshitz gravity. https://www.scientificamerican.com/article/splitting-time-from-space-evidence/
Im curious to know how has this theory developed? Is it taken seriously? What are the outstanding problems ? Have there been any impressive achievements for it since it was first proposed? If anyone can give layperson friendly answer this would much appreciated.

 

[Melbourne Guy]

"impressive achievements"?

It's hard to find anything recent, @windy miller, and nothing I can find is layperson friendly, which is probably to be expected for a theory working to quantize gravity. The Hořava–Lifshitz gravity Wikipedia page has only five references and was last edited mid-2018. And it is not much discussed here on PF from what I can see; indeed your post asking essentially the same question as you've done above in 2017 may be the latest on the topic. And reading that post, it might be worth redoing your Google Scholar search to see how many additional papers have been submitted (noting @jim mcnamara's point that submission does not mean peer reviewed...or even correctly constructed).

But regarding your post, you stated, "the first 4 years it got 2210 articles. the next four years 2240", but was the second four years additional papers? Or did the total just increase by 30 papers? Either way, it might be instructive to compare it a different quantum gravity theory to see whether the number is high or low in terms of publications.

Finally, have you reached out to Petr Hořava directly? I've found that respectful questions via email are often answered, and you may find that he is responsive to your inquiry.

 

[windy miller]

"impressive achievements"?

It's hard to find anything recent, @windy miller, and nothing I can find is layperson friendly, which is probably to be expected for a theory working to quantize gravity. The Hořava–Lifshitz gravity Wikipedia page has only five references and was last edited mid-2018. And it is not much discussed here on PF from what I can see; indeed your post asking essentially the same question as you've done above in 2017 may be the latest on the topic. And reading that post, it might be worth redoing your Google Scholar search to see how many additional papers have been submitted (noting @jim mcnamara's point that submission does not mean peer reviewed...or even correctly constructed).

But regarding your post, you stated, "the first 4 years it got 2210 articles. the next four years 2240", but was the second four years additional papers? Or did the total just increase by 30 papers? Either way, it might be instructive to compare it a different quantum gravity theory to see whether the number is high or low in terms of publications.

Finally, have you reached out to Petr Hořava directly? I've found that respectful questions via email are often answered, and you may find that he is responsive to your inquiry.

Thanks for this i forgot i had laready posted about it back in 2017 so i reread that post but i don't think anyone gave a particularly insightful answer. As to the issue with google scholar yes there next four years were additional papers. I just did a search on the last three years and got 865 papers. I think that means people are still working on it.

 

[Melbourne Guy]

300-odd papers a year is not many, @windy miller, and suggests Hořava–Lifshitz gravity is an incidental approach. There have been about 17,000 papers each on loop quantum gravity and Causal Dynamical Triangulations in the last three years, three times that many on string theory, and even Euclidean Quantum Gravity has seen many thousands of papers written.

Thanks for clarifying the Google Scholar searches were distinct results, by the way, but even with that, a breakthrough resolving the constraints of Hořava–Lifshitz gravity probably has not eventuated.

 

[windy miller]

300-odd papers a year is not many, @windy miller, and suggests Hořava–Lifshitz gravity is an incidental approach. There have been about 17,000 papers each on loop quantum gravity and Causal Dynamical Triangulations in the last three years, three times that many on string theory, and even Euclidean Quantum Gravity has seen many thousands of papers written.

Thanks for clarifying the Google Scholar searches were distinct results, by the way, but even with that, a breakthrough resolving the constraints of Hořava–Lifshitz gravity probably has not eventuated.

Thanks for that comparison, it is helpful. But what are the biggest problems for the theory ? Do you know?

 

[Melbourne Guy]

I'm not even close to being an expert, @windy miller, but as I understand it, Hořava's approach is to quantise gravity using quantum field theories and these typically run into Ostrogradsky instabilities. Hořava breaks Lorentz invariance via a Lifshitz-type anisotropic scaling (no guessing where the name of the theory came from ) at high energies then recovers the invariance at low energies but if you do that the results must be self-consistent and conform to what we observe in the universe. Initial formulations Hořava–Lifshitz gravity did not match the physical universe, and various reworking seems to have failed to eliminate all the inconsistencies.

If you're interested in further reading, Anzhong Wang's "Hořava Gravity at a Lifshitz Point: A Progress Report" (https://arxiv.org/pdf/1701.06087.pdf) is a recent-ish summary.