Talk:Cosmic string

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diameter

In the article, it states

"Cosmic strings, if they exist, would be extremely thin with diameters on the same order as a proton."

How can a 1 dimensional object even have diameter, let alone as significant as a single particle.. the _only_ measurement would be length, right? --User:203.166.107.242

String theory says that as the strings vibrate very fast they may form loops or rings. These may be the diameters to which the article refers. -- Amaxson

I think that comment may actually be incorrect. From what I've heard, it is indeed 1 dimensional, and that would obviously violate the "order of a proton" scale. I'd be interested in knowing where that information came from, or if it's just the Wikipedia editor that tried in good will to be educative, but let that slip in the process. I listened to a lecture by Kip Thorne anyway, and he claimed that there was no diameter, due to it being a defect in spacetime. It's not something that could "contain" something. And if I'd speculate here as an amateur, I'd believe the scale, if any, would in that case be on the order of the planck length, a wildly different magnitude than that of a proton. -- Northgrove 05:43, 1 January 2007 (UTC)[reply]

The "infinitely thin" bit is just an approximation. The defect gets formed by some symmetry breaking, but that just determines the possible topologies; their thinness comes from subhorizon modes getting damped to basically nothing during radiation-dominance. -- bm

Perhaps the diameter is the measure of the space that isn't there, like if you cut a 2cm wide strip from the middle of a piece of paper where a measuring grid was printed on, discarded the strip and then taped the two remaining pieces of paper together at the seams, the measuring grid would show that the infinetly thin line is 2cm wide. --TiagoTiago (talk) 21:00, 9 November 2011 (UTC)[reply]

Confusion with string theory

A second piece of evidence supporting string theory is a phenomenon observed in observations of the "double quasar" called Q0957+561A,B.

Shouldn’t this read “cosmic string theory?” The issue appears to be unrelated to string theory.

Potential Update

There is a new development announced in New Scientist magazine this week, declairing that the teams findings at CSL-1 are inconclusive due to atmospheric interference. However, there is hope in that they have been granted time on the Hubble Space Telescope (they previously used the European Southern Observatory's Very Large Telescope), which should give better images and allow them to conclusivly prove that the image is a result of cosmic string refraction.

If this goes ahead, there could be a conclusive result to this question sooner than expected.

astro-ph/0601494: CSL-1 appeared to be just two similar galaxies, not a string. Should we add this?

Is this an advertisement for New Scientist? You want to add an article talking about hopes?83.103.38.68 (talk) 09:22, 19 August 2008 (UTC)[reply]

Confusing

This article is confusing. When it says "Fields", what are we as Wikipedians speaking of?

Is it Gravitational Fields or Magnetic Fields or some kind of Dark Matter - Dark Energy Field?

Perhaps it is a prairie field or baseball field. More clarity of wording would be nice.

Personally, I do not believe in this theory, but I admit I have been dead wrong before.

As far as I know, such a object cannot exist. How could it be extruded? How could it be stable?

I came here looking for an answer to my question and found no satisfactory answer.

Supercool Dude (talk) 13:50, 3 June 2009 (UTC)[reply]

Indeed, not all cosmic strings are stable, many disintegrate immediately but there are many stable configurations as well. The stability of cosmic strings in the context of string theory has been examined in http://arxiv.org/pdf/hep-th/0312067.

These objects are predicted by many theories of the early universe, including string theory and quantum field theories, and are therefore a fairly generic prediction.

User:wakabaloola 01:11, 23 August 2010 (BST) —Preceding unsigned comment added by 90.221.106.49 (talk)

All topological defect are stable by definition of a topological defect! Unstable things are not topological defects! As a cosmic string is a 1-dimensionnal topological defects they are stable. One open question is do loops (closed strings) are stable. Actually we don't have the answer: some simulation have as result that loops are stable (nabu-goto simulation), and others (which simulate the field himself) have as result that loop are unstable and rapidly disintegrate in scalar radiation. So in a area where there is a large amount of string, as collision can generate loop, the number of string can decrease... (if loops are unstable).

On the question of which field can contain topological defects such as cosmic string: this is an open question! The best one should be the inflaton field. But Basically , there is some element that are needed to generate a topological defect: a scalar field couple to a symmetry breaking potential and a dumping effect that make fall the field in his void. (Such defects are cummon in solid state physic (but are not named cosmic strings)) If the field have 1 dimension this will create domain walls, with 2 dimensional field (a complex field) this generate strings, with 3-dimensional field this generate monopoles, with more than 3 dimension it generate textures. The choice made by people that simulate such object is a Higgs field in the FRW metric. The Higgs potential generate the symmetry breaking, and the FRW metric the dumping effect. But this is a choice ! Mainly motivated by the fact that the Higgs potential is the only one that we know that is analytically solvable and have a symmetry breaking! But we actually do not know how is the inflaton field (in fact we only need to know how is his void) so we don't know if the topological defects generate by the symmetry breaking at the end of the inflation are cosmic strings or others topological defects. So the observation of effect due to topological defects would give us nice hint on the structure of the void of the inflaton. This is why this topic have still interest, as with this knowledge we will be able to exclude large number of inflation models. — Preceding unsigned comment added by 188.62.251.143 (talk) 18:03, 15 January 2012 (UTC)[reply]

1.6 km string as massive as the earth? Really? Are you sure you don't mean a mile?

The article mentions that a 1.6 km string might be more massive than the earth, which is clearly a direct metric conversion of an original quote, "a cosmic string, 1 mile in length, may be more massive than the earth!" It's a hypothetical and wildly uncertain comparison, so you don't have to bother with the 6 tenths. The offending line should be changed to "a cosmic string, about one kilometer in length, may be more massive than the Earth." —Preceding unsigned comment added by 67.188.144.35 (talk) 18:08, 4 November 2010 (UTC)[reply]

The question of the mass density of a cosmic string is not very hard to answer! The problem is simple : the density within the string remain constant during the time evolution. So the density of the string is the same as the mean density of the universe when the string form. Therefor the string can have a very large density if it is formed at early ages as the GUT period. One big problem is that actually we have not enough information to know exactly when the symmetry breaking that generate the topological defects that could be a string appears. Even worst, we have no idea on which field have this symmetry breaking : so we even don't know if the defects are walls, strings, monopoles or textures! Observing effect due to presence of strings (or walls,monopoles, textures) should give use this information ! And probably a Nobel price to the one who would have done the observation as it will give the first clue on how is the inflation field(s). — Preceding unsigned comment added by 188.62.251.143 (talk) 17:13, 15 January 2012 (UTC)[reply]

Planck data

Paper at http://arxiv.org/abs/1303.5085 . It seems to place some limits on what kind of strings can exist but I don't know enough physics to understand the details.Geni (talk) 21:57, 3 June 2013 (UTC)[reply]

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Another null result

This time in a gravitational-wave search:

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.024017

paper has about a thousand authors mind. preprint at:

https://arxiv.org/abs/1905.03457

Gravitation - mass equivalent source

I wonder if this site could work as a citation for this passage 'A cosmic string about a kilometer in length may be more massive than the Earth.'? The article mentions length density (Because of their mass (typically 10^21 kg/m),...) and has a few sources in the bibliography that might be the source of this claim. AstroChara (talk) 05:44, 8 April 2023 (UTC)[reply]