Nikodem Poplawski's theories

[pervect]

What do people think of Nikodem Poplawski's proposal that adding torsion to GR (in the form of ECSK gravity) leads to, among other things, black holes that "bounce", and an alternative to inflation for the flatness/oldness problem?

Published in Physics Letters B, http://dx.doi.org/10.1016/j.physletb.2010.09.056 with a non-paywalled abstract at http://xxx.lanl.gov/pdf/1106.4859.pdf, I don't recall seeing it mentioned before on PF, a search finds some discussion but not in this group.

 

[PAllen]

Here is the arxiv link to the abstract + full article:

http://arxiv.org/abs/1007.0587

For a bunch of related papers by the author:

http://arxiv.org/find/grp_physics/1/au:+Poplawski/0/1/0/all/0/1

A quick scan looks interesting to me. I've come across descriptions of this formulation before (which is quite old), but never learned it or new what predictions it made different from GR.

(No substantive comments unless I read the paper).

 

[PAllen]

My first comment is on the discussion at the end of p.6, beginning of p.7:

"A massive star, that is causally connected, collapses gravitationally to a black
hole and an event horizon forms. Inside the horizon, spacetime is nonstationary and matter contracts to an extremely
dense, but because of torsion, finite-density state."
...
"After reaching its minimum size, the homogeneous and isotropic universe starts expanding. Such an expansion is not
visible for observers outside the black hole, for whom the horizon’s formation and all subsequent processes occur after
infinite time [22]. The new universe is thus a separate spacetime branch with its own timeline; it can last infinitely
long and grow infinitely large if dark energy is present."

Two things bother me. One is possibly purely linquistic. The invisibility of the proposed re-expansion is obvious. The clause "occurring after infinite time" is problematic for me, unless there is some major geometric difference from GR. In GR, one may easily define simultaneity slices that cross the horizon. My more physical concern to this model of a separate universe is that I don't see anything addressing further infall of matter. At least in GR, absolutely nothing prevents further infall across the horizon that would lead to a flow from the 'old universe' to the 'new unverse'. My initial scan shows nothing about this GR extension that would prohibit this, yet it is not addressed at all.

There is possible connection between the linguistic imprecision and the failure to address this issue.

[Edit: Putting the above more strongly, there is no discussion of the complete causal structure of the EH: the interior has no causal influence on the exterior; however the exterior has continuous causal influence on the interior. The interior sees the external history as running in parallel with the internal history.

I note that this whole observation is related to a possibly speculative discussion in the last section of the paper. The rest of the paper, on cosmology (without trying to answer about 'before the big bang') is untouched by these arguments. ]

 

[shantu]

See
http://viavca.in2p3.fr/nikodem_poplawski.html
for a video talk about this work.

 

[sardar]

Nikodem Poplawski's proposal to add torsion to General Relativity (GR) in the form of ECSK gravity is an interesting and thought-provoking idea. While it is not a widely accepted theory, it has sparked discussions and debates among scientists in the field.

One of the main implications of Poplawski's theory is the idea of "bouncing" black holes, where instead of collapsing into a singularity, they would bounce back and form a new universe. This is a fascinating concept that challenges our understanding of black holes and the nature of the universe.

Another aspect of Poplawski's theory is its potential to provide an alternative explanation for the flatness and oldness problems in cosmology. These are longstanding issues in the field, and any new proposal that offers a different perspective is worth exploring.

However, it is important to note that Poplawski's theory is still in its early stages and has not been extensively tested or supported by observational evidence. As with any scientific theory, it should be subject to further scrutiny and refinement before being accepted as a valid explanation for the phenomena it seeks to explain.

In summary, Nikodem Poplawski's theories are intriguing and have the potential to offer new insights into our understanding of the universe. However, more research and evidence are needed before it can be considered a viable alternative to current theories.