Talk:Ring singularity

message: To mention just one: through or missing the ring singularity: should clarify that one is discussing a level of structure underlying Lorentzian metric structure.---CH 09:00, 23 December 2005 (UTC)
thread_title: Problems

message: Having noted that there is some question about what form ring singularities actually take in realistic collapse,  I added the info to the appropriate section, along with references.  (The web references could probably use a formal entry in the references section, but I haven't done that yet).
Noticing claims that ring singularities "must" exist, I removed these claims as confusing.
Along the way I ran into this unsupported quote.  I removed it to the talk page under the guideline of doubtful quotes without a source.
:This problem is serious, since it suggests that perhaps the fieldline paradigm needs modification, or perhaps a particle entering a topological wormhole is unable to interact with anything on the far side, and sees itself to be in a single-ended cavity. 
Looking even further, I found a whole BUNCH of stuff to fix.  :-(, too much to list.  See the edit logs.
Pervect 22:17, 20 August 2006 (UTC)
thread_title:  Ring singularities & deletions 

message: The current page text reads, "Since a point cannot support rotation or angular momentum...".
Such a statement is awkward in light of the fact that quantum field theories all seem to insist that pointlike particles do, in fact, carry angular momentum.
While the geometrical arguments for the ring as the minimal shape that can support angular momentum are sensible, the widespread acceptance of the concept of point angular momentum seems to leave the above statement on less than firm footing.
Mseslacker 05:31, 8 January 2007 (UTC)
thread_title: Angular Momentum of Point Mass

message: There are a number of problems with this article as it currently stands: I hesitate to call it "wrong", because it is generally too imprecise to be unambiguously wrong.  But essentially, it conveys the idea that the Kerr spacetime singularity having a ring structure is essential for it to act as a wormhole, and event that "to go through the wormhole, one must go through the ring".  This is very wrong, as I can argue in two different ways: (1) by pointing out that the Reissner-Nordstrøm solution can also work as a wormhole, yet it has a point (timelike) singularity, and (2) by referring to fig 1(a) on page 1244 of Carter's 1966 *Phys. Rev.* article, “Complete Analytic Extension of the Symmetry Axis of Kerr's Solution of Einstein's Equations” (available here), in which it is quite apparent that one can navigate from one region I (aka "universe") to another while keeping r>0 at all times (compare with fig. 2 of the same article, which shows that going through the ring singularity means going to the region r<0); in fact, geodesic (2) in fig 3(a) does exactly that: it "goes through the wormhole" (and emerges in a different universe) without going through the ring.
In a slightly handwaving way, I would say that there are two different phenomena associated with the Kerr spacetime: one is the "eternal wormhole" spanning an infinite number of universes, separated by double pairs of horizons (to go from one region I to another, one must cross four horizons: an ingoing external horizon, an ingoing internal one, an outgoing internal one and an outgoing external one); the ring singularity is another feature, which leads to a different kind of world, one where the black hole is repulsive (and there are no horizons there, as witnessed by fig. 2 in the aforementioned article).  Confusion between the two is magnified by the fact that both phenomena (a black hole seen from the outgoing point of view and with its outgoing horizons; or a different kind of object with an apparently negative mass) have been called "white hole".
I would like to clarify this, but I'm not sure exactly how to proceed, and I'd like to test whether anyone has comments to make before slashing the article.  --Gro-Tsen (talk) 19:03, 21 February 2011 (UTC)
thread_title:  Article conveys wrong ideas about the "wormhole" 

message: This appeard on the main page, exactly as I relate it here, minus quotes: "[Layman's opinion: the MINIMAL shape is two points circling each other, isn't it?]."
This is an inappropriate statement in an article. Commentary should be reserved for the Talk page. Chardansearavitriol (talk) 01:29, 15 March 2011 (UTC)
thread_title:  Improper sentence. 

message: The article gives the wrong impression (in the section "Traversability and nakedness") that in order to avoid hitting the ring singularity one must carefully navigate through the relevant region. This idea probably comes from mentally grafting the Schwarzschild "look and feel" onto the Kerr case. But in fact a particle free-falling towards the Kerr black hole will almost NEVER hit the ring. I know that this is almost total opposite of the Schwarzschild black hole, nevertheless that's how it is with Kerr (and that's how the thing ought to be popularised in pop-sci presentations instead of the obligatory unavoidable singularity).
Specifically, for a particle falling into the Kerr black hole to hit the ring, its trajectory must be 100% equatorial. Even a slightest deviation or wobble will cause the ring to repulse the particle off itself. Rigid bodies are more complicated because their constituent particles do not follow paths of free fall. But it's still extremely difficult to hit the ring.
(Of course I'm leaving aside the tidal forces near the ring which FAPP would be equally nasty.)
On top of that there is the issue mentioned above by user Gro-Tsen: there are different "extra universes" such free-falling particle can go to: (1) if it's falling fast enough, it will go through the ring into the "Region III" universe in which the ring acts as a naked white hole singularity. (2) if it's falling slower (perhaps it was thrown in with less force), it will not reach the area around the ring but instead, having passed both horizons, it will turn back and cross two other horizons into another universe in which the two horizons surround a white hole.
It's all best seen on the Penrose diagram or something similar, with all the universes laid out "flat". JanBielawski (talk) 23:46, 29 July 2013 (UTC)
replies: text: I completely agree.  In fact, I think the article should be largely rewritten (although, to be honest, I'm not sure the ring singularity deserves its own page as opposed to a section of some article on the Kerr solution).  I don't have the time to do it, but if you do I will applaud.  (Also, may I insert a shameful plug to a page of mine as a suggestion for certain things that might be said here?) --Gro-Tsen (talk) 14:01, 1 August 2013 (UTC)
thread_title:  Hitting the ring is actually quite hard 

message: Inside a spinning supermassive black hole, can a point singularity handle its infinite curvature of spacetime and the angular momentum imposed on it by its surrounding galaxy? This is a hot topic. The answer depends on who you ask although it appears most cosmologistsThe GOD Equation by Michio Kaku, p. go with ring singularity. ~~ 2607:FB91:1993:15C9:D0C2:4F69:1B88:C5F (talk) 16:03, 12 August 2023 (UTC)
thread_title:  All Spinning Galaxies at their Center have Spinning Supermassive Black Holes which have Ring Singularities at their Core