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Contents 1 Archives 2 Discussion 2.1 Debate 2.2 Categorization 2.3 Merge Gravastar and Dark Energy Star 2.4 New dark energy star theory 2.5 Revision

[edit] Archives

I've moved the old (Feb 2004) talk to Talk:Gravastar/Archive1. Find below a copy of the newest contrinution. --Pjacobi 20:22, 27 Nov 2004 (UTC)

[edit] Discussion

[edit] Debate

I've read the quote from the nasa article, and it doesn't appear to say that they're using redshift to determine the distance of Gamma ray bursters, but that they are unable to. It also seems to me that there isn't an argument anymore, but both sides just bashing one another. What exactly is the discussion about? ! Obviously Plautus is in support of plasma theories over black hole ones. There's nothing wrong with that. But the way that everyone goes about these arguments concerning them (I also reference talk:black hole), is an indicator of... hostility. Can't we make our points without having a negative tone to our text? It makes it harder for people to get the point when they're too busy trying to sort through all of the negativity (this doesn't seem to be a side-specific thing). Debate all we want, but don't throw around insults. Pointing out lack of credibility can be much nicer, I believe. But then again, my opinion may be completely out there. 18:51, 27 Nov 2004 4.226.255.51

[edit] Categorization

I have removed the category links for "Black holes" and the redundent "Stellar mass black holes". Gravastars are not black holes. Instead I have placed this article under "general relativity". I also removed the "Cosmology" category link: I cannot see why a proposed stellar phenomenon relates to cosmology. (I may add "stellar phenomena" as a catergory now.) --EMS | Talk 16:10, 27 July 2005 (UTC)

[edit] Merge Gravastar and Dark Energy Star

see also Talk:Dark energy star

'Gravastar' vs 'Dark Energy Star'

Having read both entries and several linked pages, I am still unclear as to the distinction. Are these simply alternative names for a single concept? If so, would it not be advisable to merge them into a single entry?

Someone please perform the merge ASAP - JustinWick 03:58, 20 January 2006 (UTC)

'Gravastar' vs 'Dark Energy Star'

Please do NOT merge! AFAIK Gravastar is einstein-bose condensate. However Gravastar article is wrong - not all matter can form einstein-bose condensate. Some form fermion condensates. The catch with Gravastar is that *gravitons* form einstein-bose condensate cuz they have spin 2. On the contrary, this new buzz may or may not involve quantum condensates (they talk about superfluids), but only on the star surface. And bigger difference is, there's nothing about gravtions in this new one.

unsigned vote

I dissagree, the two pages shoule be kept seperate

Above vote by 20:37, 15 March 2006 User:Eevo

[edit] New dark energy star theory

This makes for an excellent read... New Scientist Article. From my reading of that the dark energy star is a completely different beast to the gravastar or dark star which some people seem to equate it with - it should end any confusion. --LiamE 10:13, 10 March 2006 (UTC)

Having said that a read a bit deeper it the article is rather similar to a gravastar as descibed in its article. Can someone please clarify the differences between the theories please. --LiamE 10:35, 10 March 2006 (UTC)

I read the articles and Gravastar and Dark Energy Star and Dark Star. At first they all seemed completely different - now they are starting to sound so similar that the Dark Energy Star appears like a refinement on the idea of a Gravastar. As far as I can tell, the heart of the Gravastar / Dark Energy Star articles is the idea that there are no event horizons, singularities, or regions of negative time-dilation - because of locally observable quantum effects at the Schwarzschild radius (in contradiction to classical General Relativity which suggests no locally observable effects at the horizon in the case of large masses). The Gravastar paper focuses on the geometry of space time that arises if a quantum shell forms close to the Schwarzschild radius and concludes that the shell is stable, there are no horizons, or singularities - it speculates somewhat tangentially and vaguely on both the nature of the quantum shell and observable differences between a Gravastar and a classical General Relativity Black Hole. The dark energy star paper makes passing reference to the Gravastar paper and its space-time geometry and stability (treating no negative time dilation, no horizons, no singularities, and stability as givens) and instead focuses on the behavior of infalling matter as it approaches the shell from outside. In particular, it predicts observably accelerated proton decay at the shell.

[edit] Revision

I don't mean to step on any toes, but I've made some revisions which will hopefully clarify issues and treat the idea in a more neutral and consistent tone. I don't believe that gravastars are a particularly interesting idea, but I think they should at least be described accurately in the wikipedia, presenting the claims of their creators in a fair light.

I'd like to clarify the difference between a gravastar and a dark energy star. Dark energy is a completely hypothetical form of energy which may exist in the Universe presently, and could explain certain problems in cosmology. In fact, it is thought that dark energy may account for roughly 70% of the mass-energy content of the Universe. This energy could find itself condensed in a region of space, and collapse to form a "star". Of course, there would be no reason for it to stop collapsing, since it presumably has almost no interactions, so a "dark energy star" should just be a black hole which formed out of dark energy somehow.

On the other hand, a gravastar (also completely hypothetical) would be composed of a very unusual form of matter which would be extremely rare in the Universe, except in the vicinity of a gravastar. Indeed, the primary mechanism for the formation of that form of matter would be the collapse nearly to what would be a regular black hole.

We know very little about either dark energy, or gravastar matter, but there is no reason to expect that they are related. It is possible that dark matter and/or dark energy and/or gravastar matter are related, but they are beyond present understanding of science.

As for the New Scientist article, I think the only issue it presents is that Chapline (somewhat arbitrarily) dubs part of this gravastar solution "dark energy". Calling a gravastar a "dark energy star" reeks of trying to put his name on a totally different idea. This is liable to be very confusing, but it might become standard usage among that tiny fraction of astrophysicists who give any credence to . Since they are essentially (though not exactly) the same idea, I think the dark energy page should just contain a brief explanation---maybe a clearer version of the mess I seem to be leaving on this page---of what a dark matter star should be, and what Chapline has dubbed it, along with a prominent link to this page.

Basically, the problem with dark energy, dark matter, and gravastars is that there is no good theoretical understanding of why or how they exist. On the other hand, there are at least observation clues which indicate that dark energy and dark matter do exist, whatever they're made of.

[I can give a first-hand account of that Gravity Meeting mentioned in the article. Note that the meeting does not have rigorous academic standards. I'm slightly surprised that New Scientist would treat Chapline's claims so seriously. I'm all for questioning accepted notions. I'm not all for rejecting accepted notions for no other reason than the fact that their accepted. Nor am I for accepting ideas just because I came up with them. Chapline does not seem to believe the same. Chapline's objections to more commonly accepted physics seem to be based on misunderstandings of it, or discomfort with a more-or-less random subset of ideas it contains. Chapline's proposed alternatives don't really explain much, either. (Pawel Mazur was also present, creating a ruckus along the same lines.) All in good fun, but no science resulted.]

P.S. I won't make any comment about the correct classification of this article, but "Stellar mass black holes" is not redundant in the presence of "Black holes". "Stellar mass black holes" are black holes which have roughly the same mass as an ordinary star, as opposed to tiny black holes, or supermassive black holes. --MOBle 07:12, 11 July 2006 (UTC)