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Today, I was watching the Inexplicable Universe with Neil deGrasse Tyson.

He spoke about Dark Matter, Dark Energy, and then he spoke about Tachyons.

Naively, I thought what if the reason we can't understand dark matter/dark energy is because it is moving faster than light?

I would be very interested how this fits in to the current thinking about tachyons and dark matter/dark energy? Is there an obvious point that makes this association impossible? Is there a property of tachyons that is clearly in opposition to what we know about dark matter/dark energy?

Larry Freeman
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    I don't know if this paper is anything interesting. I found it on arxiv.org: http://arxiv.org/abs/astro-ph/0403048 – Larry Freeman Jan 03 '15 at 06:11
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    Dark matter is forming halos around galaxies, so if it does obey the usual laws of physics, it is not moving faster than ordinary matter. Dark energy, on the the hand, is merely a term to denote the accelerating expansion of the universe and there are no obvious effects that would link it to any form of tachyon model. – CuriousOne Jan 03 '15 at 06:50
  • Thanks very much. I knew that it was a naive hypothesis. My question was based on dark energy/dark matter not being understood and tachyons being purely theoretical particles. – Larry Freeman Jan 03 '15 at 07:14
  • Since someone down voted me, I would be very glad to understand why. Please post a comment if you would. I will delete this question if anyone feels that my question is not appropriate or not sincere. – Larry Freeman Jan 03 '15 at 07:15
  • Some people have a short fuse and sometimes it's hard to distinguish between someone with a naive idea who has a real question and a person who is just pushing their quack theories. Don't take it personally and keep asking. For what it's worth, I didn't vote you down and I'll be glad to expand on my comment if you have further questions. – CuriousOne Jan 03 '15 at 07:21
  • It's the right place but questions about tachyons are a bit like waving a red cloth in front of a bull. Most knowledgable folks are probably tired answering them. Unlike other theoretical corner cases that are not completely ruled out tachyons are suffering from too many problems to be taken seriously. It's just not possible to make them work properly, and not just in one theory, but basically in any theory. I would forget about them. Cold dark matter, on the other hand, is probably going to stay with us. – CuriousOne Jan 03 '15 at 07:59
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    Actually, I would say the opposite; this is not the right place for your question, because it is not a well justified question. You haven't given any reason to think dark matter or dark energy could be explained by tachyons. Considering that it's common knowledge among researchers and advanced students - the target audience of this site - that the properties of these three things are completely different, a question that doesn't give any reason to question that common knowledge shows a lack of research effort. – David Z Jan 03 '15 at 09:41
  • Hi @Larry Freeman: $\uparrow$ Link to video? Which minute in video? – Qmechanic Oct 14 '17 at 14:40
  • @Qmechanic, I called out the reference (Neil deGrass Tyson) and state the context independent of the video. The Amazon link to the video is here: https://www.amazon.com/Watch-Trailer/dp/B00P52ETL4/ref=sr_1_5?s=instant-video&ie=UTF8&qid=1508002714&sr=1-5&keywords=neil+degrasse+tyson – Larry Freeman Oct 14 '17 at 17:39
  • @Qmechanic, apologies. This was over two years ago. I was so excited I posted my question here and was told that it was a very stupid question (as you can see by the comments). I will read the paper posted by AnnaV (thanks, Anna) and add details if I have anything of interest to this community. – Larry Freeman Oct 14 '17 at 17:48
  • FYI: NdGT talks about dark matter, dark energy, & FTL. – Qmechanic Oct 14 '17 at 22:54
  • The dark matter/energy part of my question was my own wild supposition based on NdGT's talk about FTL. – Larry Freeman Oct 14 '17 at 23:29

2 Answers2

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The paper above mentioned (http://arxiv.org/abs/astro-ph/0403048) says that -

  • if tachyons make up some of the missing mass of the universe then their imaginary mass should be of millielectronvolts! (we don't know what imaginary mass means)

  • The number of species of subluminal particles (other massive particles) should be less.

Though considering tachyons as some component of dark matter doesn't change the cosmological consequences but they would indeed have some effect on the nucleosynthesis.

Tachyon field as dark energy has been studied. Their potential does give solutions to the accelerated expansion of the Universe. The major drawback in accepting such theory is- in general (like ΛCDM model) the expansion doesn't play a significant role beyond redshift z=1 but in tachyonic models they are significant. In such models, they indeed slow down the structure formations. But we have evidence to show that there should be a rapid structure formation (actually even faster than what ΛCDM model predicts- galaxy cluster- XMMU-J2235.3-2557 at z=1.4)

299792458
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PRAJWAL H.P.
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Byt the simple method of googling "tachyons and dark energy" two arXiv papers came on , the first published in phys rev D.

We present a detailed study of cosmological effects of homogeneous tachyon matter coexisting with non-relativistic matter and radiation, concentrating on the inverse square potential and the exponential potential for the tachyonic scalar field.

It seems that yes, models can be built using tachyon matter that display the expansion fitted with dark energy.

The second tackles dark matter also but is only an arxiv publication.

Anyhow the question can be answered by: that it is not impossible to construct such models , which will need many parameters fitted from observations.

anna v
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  • Comment to the answer (v1): The linked arXiv papers presumably talk about tachyonic fields (which are subluminal); while OP apparently asks about tachyonic point particles (which are superluminal), cf. this Phys.SE post. It would interesting to know exactly what Neil deGrasse Tyson said in that video. – Qmechanic Oct 14 '17 at 14:59
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    @Qmechanic it calls it "matter" in the abstract and also the main paper at, least the first link in the search. All matter is described by fields after all. Tachyon wavepackets must be superluminal by definition – anna v Oct 14 '17 at 16:09
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    Here is a link discussing tachyonic proposals https://link.springer.com/article/10.1140%2Fepjc%2Fs10052-016-4577-8 – anna v Oct 15 '17 at 04:06