Using the universe as a 'cosmological collider' (Update)

July 20, 2017, Harvard-Smithsonian Center for Astrophysics
New research finds how the properties of subatomic elementary particles, visualized in the middle of this artist's impression, may be imprinted in the largest cosmic structures visible in the universe, shown on either side. Credit: Paul Shellard

Physicists are capitalizing on a direct connection between the largest cosmic structures and the smallest known objects to use the universe as a "cosmological collider" and investigate new physics.

The three-dimensional map of galaxies throughout the cosmos and the leftover radiation from the Big Bang – called the (CMB) – are the largest structures in the that astrophysicists observe using telescopes. Subatomic , on the other hand, are the smallest known objects in the universe that particle physicists study using particle colliders.

A team including Xingang Chen of the Harvard-Smithsonian Center for Astrophysics (CfA), Yi Wang from the Hong Kong University of Science and Technology (HKUST) and Zhong-Zhi Xianyu from the Center for Mathematical Sciences and Applications at Harvard University has used these extremes of size to probe fundamental physics in an innovative way. They have shown how the properties of the elementary in the Standard Model of may be inferred by studying the largest cosmic structures. This connection is made through a process called cosmic .

Cosmic inflation is the most widely accepted theoretical scenario to explain what preceded the Big Bang. This theory predicts that the size of the universe expanded at an extraordinary and accelerating rate in the first fleeting fraction of a second after the universe was created. It was a highly energetic event, during which all particles in the universe were created and interacted with each other. This is similar to the environment physicists try to create in ground-based colliders, with the exception that its energy can be 10 billion times larger than any colliders that humans can build.

Inflation was followed by the Big Bang, where the cosmos continued to expand for more than 13 billion years, but the expansion rate slowed down with time. Microscopic structures created in these energetic events got stretched across the universe, resulting in regions that were slightly denser or less dense than surrounding areas in the otherwise very homogeneous early universe. As the universe evolved, the denser regions attracted more and more matter due to gravity. Eventually, the initial microscopic structures seeded the large-scale structure of our universe, and determined the locations of galaxies throughout the cosmos.

In ground-based colliders, physicists and engineers build instruments to read the results of the colliding events. The question is then how we should read the results of the cosmological collider.

"Several years ago, Yi Wang and I, Nima Arkani-Hamed and Juan Maldacena from the Institute of Advanced Study, and several other groups, discovered that the results of this cosmological collider are encoded in the statistics of the initial microscopic structures. As time passes, they become imprinted in the statistics of the spatial distribution of the universe's contents, such as galaxies and the cosmic microwave background, that we observe today," said Xingang Chen. "By studying the properties of these statistics we can learn more about the properties of elementary particles."

As in ground-based colliders, before scientists explore , it is crucial to understand the behavior of known fundamental particles in this cosmological collider, as described by the Standard Model of particle physics.

"The relative number of fundamental particles that have different masses – what we call the mass spectrum – in the Standard Model has a special pattern, which can be viewed as the fingerprint of the Standard Model," explained Zhong-Zhi Xiangyu. "However, this fingerprint changes as the environment changes, and would have looked very different at the time of inflation from how it looks now."

The team showed what the mass spectrum of the Standard Model would look like for different inflation models. They also showed how this mass spectrum is imprinted in the appearance of the large-scale structure of our universe. This study paves the way for the future discovery of new physics.

"The ongoing observations of the CMB and large-scale have achieved impressive precision from which valuable information about the initial microscopic structures can be extracted," said Yi Wang. "In this cosmological , any observational signal that deviates from that expected for in the Standard Model would then be a sign of new physics."

The current research is only a small step towards an exciting era when precision cosmology will show its full power.

"If we are lucky enough to observe these imprints, we would not only be able to study particle and fundamental principles in the early universe, but also better understand itself. In this regard, there are still a whole universe of mysteries to be explored," said Xianyu.

This research is detailed in a paper published in the journal Physical Review Letters on June 29, 2017, and the preprint is available online.

Explore further: Gravity may have saved the universe after the Big Bang, say researchers

More information: Xingang Chen et al, Standard Model Background of the Cosmological Collider, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.261302 , On Arxiv: https://arxiv.org/abs/1610.06597

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14 comments

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antialias_physorg
4.5 / 5 (2) Jul 20, 2017
Neat way of connecting the very large to the very small (for more than just the distribution visible in the CMBR)

Inflation was followed by the Big Bang...

Erm...whut?
Inflation is a phase of the Big Bang.
Seeker2
not rated yet Jul 20, 2017
Let me guess. You have to have spacetime so you can have somewhere for the Big Bang to happen. Like we're the only fish in the bowl. Our attitude moderator has accused me of arrogance, but not that much I would think.
nikola_milovic_378
Jul 22, 2017
This comment has been removed by a moderator.
Da Schneib
5 / 5 (1) Jul 22, 2017
@antialias,
Inflation was followed by the Big Bang...

Erm...whut?
Inflation is a phase of the Big Bang.
Not in many of the scenarios. The most plausible scenarios have the universe emerging from a quantum fluctuation in a substrate whose characteristics we have not yet been able to probe. The quantum fluctuation has a high cosmological constant. This quantum fluctuation undergoes inflation, and then undergoes vacuum decay, which dumps the energy from the high cosmological constant everywhere in space; this energy then becomes the Hot Big Bang, which happens across the no-longer-inflating universe spreading from the locations where the vacuum decay starts at the speed of light.

Thus, the inflation precedes the Hot Big Bang, and the vacuum decay of the cosmological constant precipitates it.
Seeker2
not rated yet Jul 24, 2017
... a substrate whose characteristics we have not yet been able to probe.
As for example an antimatter black hole? Merge one of those with a regular matter black hole and you should get a pretty good kick. At least a lot of high energy radiation. I was a bit confused in my previous idea about inflation being regulated by baryogenesis. It's regulated by leptogenesis which occurs long before baryogenesis. If not, this theory has been falsified. What, by the way, is inflation? I would suggest the distribution of leptons regulated by leptogenesis, now seen as the CMBR. I've described this process before, except with baryons instead of leptons. Anyway it involves gravity, or the energy density of spacetime, however you want to look at it.
Seeker2
not rated yet Jul 24, 2017
cont
Speaking of gravity it might be noted the energy density of spacetime, and thus gravity, was much higher during inflation. High enough to form lepton-antilepton particle pairs.
Seeker2
not rated yet Jul 24, 2017
cont
Thinking of Penrose's concentric circular patterns in the CMBR - could it be touch points where the two black holes I mentioned are merging?
Seeker2
not rated yet Jul 24, 2017
Speaking of gravity it might be noted the energy density of spacetime, and thus gravity, was much higher during inflation. High enough to form lepton-antilepton particle pairs.
And, by the way, the humongous black holes formed in the early U.
Seeker2
not rated yet Jul 24, 2017
cont
Note that when normal matter black holes merge, they ring, but then keep most of their matter. If however one black hole is antimatter they annihilate along their touch points when they ring so the circle of touch points eventually becomes smaller and smaller as with the concentric circles.
Merrit
not rated yet Jul 27, 2017
What if one of the BH is much larger than the other so that all the energy released from the annilation is still held by the remaining black. As is well known, nothing escapes from a black hole.
Seeker2
not rated yet Jul 27, 2017
What if one of the BH is much larger than the other so that all the energy released from the annilation is still held by the remaining black.
All the energy NOT released in the annihilation is retained by the larger BH.
As is well known, nothing escapes from a black hole.
I heard somewhere that they evaporate but that sort of shoots my theory.
Seeker2
not rated yet Aug 02, 2017
What, by the way, is inflation? I would suggest the distribution of leptons regulated by leptogenesis, now seen as the CMBR. I've described this process before, except with baryons instead of leptons. Anyway it involves gravity, or the energy density of spacetime, however you want to look at it.
During baryogenesis particle pairs are created and directed in opposite directions. If that direction is similar to the previous particle pair direction then the particles will accumulate otherwise annihilate and their energy thrown back into the process to form another particle pair. If you want to generate and separate N particle pairs then that would require something like 2^N or maybe N! pair creations. So you could create 2 separate universes, in each of which matter coalesces into black holes. Resulting in one universe of two black holes setting up another big bang event when they merge. Like Penrose's cyclical universe.
Seeker2
not rated yet Aug 02, 2017
cont
Similarly In leptogenesis the two groups of particles would be repulsive in a similar process and these groups could be distributed throughout both groups of baryons without incurring more annihilation.
Seeker2
not rated yet Aug 02, 2017
cont
Perhaps an interesting possibility - humongous black holes could be created before leptogenesis even occurred. With all the creation and re-creation going on it would seem like plenty of time would be available.

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