Massive neutrinos and new standard cosmological model: No concordance yet

July 22, 2014
The research group demonstrates that adding such massive neutrinos to the standard model does not really explain all datasets. Credit: The Milky Way, NASA.

Neutrinos, also known as 'ghost particles' because they barely interact with other particles or their surroundings, are massless particles according to the standard model of particle physics. However, there is a lot of evidence that their mass is in fact non-zero, but it remains unmeasured. In cosmology, neutrinos are suspected to make up a fraction —small but important— of the mysterious dark matter, which represents 90% of the mass of the galaxy. Modifying the standard cosmological model in order to include fairly massive neutrinos does not explain all the physical observations simultaneously.

This is the conclusion of a new scientific paper published in the journal Physical Review Letters, signed by Licia Verde, ICREA researcher from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), Boris Leistedt and Hiranya V. Peiris, from the University College London.

A model that does not meet observed data

Some scientific studies suggest that the existence of massive could potentially explain other physical anomalies and phenomena observed in the Universe (for instance, the number of galaxy clusters observed by the Planck satellite). This hypothesis represents an extension of the standard cosmological model and may have profound implications for both cosmology and .

In the article published in the journal Physical Review Letters, the research group demonstrates that adding such massive neutrinos to the does not really explain all datasets. Researcher Licia Verde affirms that "the new paper proves that the new model is in fact not a satisfying solution, in the sense that it is not able to explain all data sets simultaneously. Therefore, it cannot be the correct of the Universe".

Neutrinos: elusive and difficult to detect particles

Neutrinos travel almost at the speed of light. Most of thousands of millions of neutrinos passing through the Earth emanate from the Sun and the atmosphere. However, gamma ray explosions, star formation and other cosmic phenomena can produce these particles, which are extremely hard to detect. Huge laboratories, such as the IceCube in Antartica, are necessary, and they only capture a few neutrinos (leading to poor measurements of neutrinos masses). Therefore, measuring the exact masses of the neutrinos is a major milestone for the entire physics community.

"Neutrinos' properties can be also measured by studying the cosmos —explains researcher Licia Verde—, but cosmological observations have not detected neutrinos' mass yet". According to Licia Verde, "we know that the mass of neutrinos is between ~0.05 eV and ~0.2 eV, so is closing in. There is a lot of work to do in order to get a robust measure but we hope that the next generation of cosmological data will be able to 'see' the mass of neutrinos and provide a more accurate measure of the mass of these particles".

Licia Verde, ICCUB researcher, also participates in the international project Sloan Digital Sky Survey (SDSS-III), one of the largest galaxy survey. She was member of the Wilkinson Microwave Anisotropy Probe (WMAP) team, and was awarded with the 2012 Gruber Cosmology Prize for her pioneering contributions to the study of primitive Universe.

Explore further: Massive neutrinos solve a cosmological conundrum

More information: "No New Cosmological Concordance with Massive Sterile Neutrinos." Boris Leistedt, Hiranya V. Peiris, Licia Verde. Physical Review Letters.

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3 / 5 (2) Jul 22, 2014
The particle models of dark matter cannot explain the situations, in which the field character of dark matter manifests itself (the superluminal shielding artifacts in particular). In addition, all attempts to observe the sterile neutrinos failed so far.
Jul 22, 2014
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1 / 5 (2) Jul 22, 2014
Are you sure neutrinos aren't just electrons at some different distance from the proton ground as it transits the gap? My thought anyway.
1 / 5 (5) Jul 22, 2014
A model that does not meet observed data

This is a worrisome trend in science lately. Perhaps we should rethink how these models are built.
Jul 22, 2014
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1 / 5 (2) Jul 22, 2014
That electrons travel from the nucleus to their highest point of orbit and back again. They would appear to change size and charge as they transit. I have a new model of theoretical physics that I would love to have challenged, but if you are not an "establishment" physicist, who do you talk to and how do you get anyone to listen to your concepts???
Jul 22, 2014
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Jul 22, 2014
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5 / 5 (4) Jul 23, 2014
maitriandkaruna: Electrons interact with matter quite readily. Detecting them is easy.

Neutrinos are not electrons. Their properties are completely - and I do mean completely - different. Detecting them is hard.

We don't need more crackpot physics here. Fall out of love with your imagination and instead read up. Start with Wikepedia. Not perfect, but the articles on electrons and neutrinos are not a bad place to begin.

Scroofinator: No, it is not a worrisome trend in science. What the researchers did makes good logical sense: they took a hypothesis, ground it into a model, and looked to see how closely the model results fit actual observations. They didn't fit. That's called 'falsification,' and it's an essential part of science. Learning that an hypothesis doesn't fit the data is always a step forward.

Of course that's only one study; we'll want to see it replicated, as well as confirmed by other experimental means.
Jul 23, 2014
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5 / 5 (4) Jul 23, 2014
This is a worrisome trend in science lately.

No. That's the norm. As a scientist you come up with a zillion ideas, but most of them don't pan out. Once in a while one does pan out (as those zillion ideas aren't random, but based on making a few, assumptions and extrapolating/calculating from there) - and that's where you hit the jackpot.

Publishing stuff that doesn't work is as important as publishing stuff that does (though journals tend to bias towards the latter due to limited space). It helps prevent other researchers from wasting time on duplicating that particular mistake. Scientists aren't infallible (Note: One should not extrapolate from this that what they publish is mostly wrong as that stuff goes through peer review.)
5 / 5 (2) Jul 23, 2014
It has been long known that hot dark matter (HDM) can't predict the standard cosmology, but cold DM (CDM) can. But mixed models can.

However, even massive neutrinos is but 0.2 % or so of the DM budget. So it is nice that they can exclude adding massive neutrinos would be a fully predictive cosmology model. That is both resolution and precision! I wish the press release took that tack, could have prevented the usual erroneous claims of "a constrained problem means science is useless" instead of the observationally correct "a constrained problem means science has once again advanced". :-/
5 / 5 (2) Jul 23, 2014
@maitriandkaruna: "I have a new model of theoretical physics that I would love to have challenged, but if you are not an "establishment" physicist, who do you talk to and how do you get anyone to listen to your concepts???"

Just by asking that question informed people can see that you have no idea how science works. (And then likely your idea, interesting as it may be, is not scientific.)

As Arties notes, you have to test your idea: what does it imply but more importantly IMO what would make it wrong? If you yourself can tell quantitatively (with the help of statistics on uncertainty et cetera) what your idea says and why it tentatively works (why the factors that could make it wrong are not present), you can get it published in peer review. Never mind if there are ideas that compete, presenting working alternatives are always useful. (Note "working", e.g. general relativity is so good that modified gravity isn't really a working alternative any longer.)

5 / 5 (2) Jul 23, 2014

So, you talk first to peers, e.g. you study the area and get familiar with the players, usually as a student of some sort. If you have no formal education at the start, you can approach any educator with your willingness to learn thoroughly, that is what education is for. It may take a few years, but that is the effort what education demands.* Then you cooperate, discuss, compete with the scientists/tutors. That leads to understanding how, and a base from which, you can publish.

*I have a PhD. It would take me many years to get to the science front, and have anything valuable to present, in a subject I'm no familiar with. Say, after I have mastered the basics, education leaves you typically 2-5 decades from the research front. So another 2-3 years to get there. All in all, I would say it would take 7-8 years to start to publish, form a generic university background.

Mind, people have published on unusual subjects, such as recreational mathematics, with a lot less effort.
5 / 5 (1) Jul 23, 2014
Almost all of the neutrinos released to space will be still out there somewhere.

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