How physicists helped shape the cosmic web with a soft cloth

The reconstruction of the cosmic web - a vast network of fibrous structures of matter scattered throughout the universe - is based on patterns of textile mold growth.
Zoom in / The reconstruction of the cosmic web – a vast network of fibrous structures of matter scattered throughout the universe – is based on patterns of textile mold growth.

Joseph N. Burchett et al. / AJL

There is hardly a time to write about every cool science fiction that comes our way. So this year, we again run a special twelve days of the Christmas series of posts, publishing a science fiction story that went through the cracks in 2020, every day from December 25 to January 5. Today: How physicists use growth patterns to create filaments of the cosmic web The humble slime mold to model the dark matter.

The back of our universe is a vast network of giant fibers connected to each other, with huge waves. Most of the material that makes up this “cosmic web” is dark matter, with diffused and distant gases. Earlier this year, a team of scientists from the University of California, Santa Cruz (UCSC) developed a unique approach to modeling this cosmic web, based on a pattern of greenery growth, and found some surprising similarities. They described their approach in a March paper published in the Astrophysical Journal Letters.

“We don’t think the universe was created by a giant cloth mold,” co-author Joseph Burchett told Arsen, beating our hopes of a new creative myth. “This really comes down to the similarity of the products of these two very opposite processes. At the end of the day, similarities are produced in the superiority of nature.”

Slime mold is sometimes mistaken for a fungus, but technically it is a kind of amoeba: a single-celled organism that lacks neurons, the brain does not matter. Although they are capable of performing some amazing feats, some ask scientists to consider whether they are capable of some kind of primitive cognition. There are many varieties of slime mold (in fact over 900); In this case, we are talking about Fizaram polycephalam, An oo zing, spongy yellow mold commonly found on forest floor or on decaying logs.

Previous studies have shown that slime mold is able to solve mazes and get rid of traps, for example, making simple decisions. And in 2010, scientists loosened the mold of a cloth in a petri dish containing bits of automotive (a food of choice) representing Tokyo railway stations, enabling them to recreate that transport network, essentially the best routes. Finds.

When researchers put food on cities on a map, the slime mold collaborates, spreads out to map many possible configurations and then dies to illuminate the shortest route between cities and the most efficient overall system map.

At first glance, the mold seems to be very far from the web of the universe. As Matthew Francis explained back in 2014 in Ars Technica:

At the beginning of its history, there were no stars or galaxies in the universe, and the density of all things was remarkably uniform. However, as seen in the cosmic microwave background, small fluctuations in this density led to smaller regions where the amount of dark matter was slightly higher than elsewhere. In turn those slightly more objects attracted more matter, producing a slower cascade: some places collected a lot of dark matter and gas, while others evacuated in large quantities.

According to the sophisticated supercomputer computer simulation, the result was a cosmic web: knots of dark matter connected by thin filaments, with huge vv aids. Galaxies and clusters of galaxies form in regions falling from the gas attracted by the gravitational pull of the dark matter. The resulting web is called the massive creation of the universe, and most observational cosmology involves the process of mapping this cosmic web into three dimensions …. It is fundamentally difficult to observe the filaments that connect everything together. This is because it contains a lot of dark matter, relatively little gas, and few or no stars. Astronomers discovered some fibers by measuring the light absorbed by the gas; Others have used gravity lenses from dark matter.

Per Burchet, the textile mold work began as an archival data analysis project funded by the Hubble Space Telescope to study the distribution of gas in the cosmic web – that is, “the storage of gas, the fuel from which the galaxy is formed,” he said. Astronomers can identify these web nodes as dark matter haloes around the surrounding galaxies, while connect threads have proved more challenging in places. Burchett planned to use background quarters to essentially “light up” the home gas, but it became difficult to design a reliable algorithm to detect those fibers in a large set of observation data.

“The trouble you inevitably experience is, where do I draw the cosmic web?” He said, “Because the real backbone of the cosmic web is a dark matter. The diffused gas that spreads the dark matter structure is really the only way for us to detect this matter.” Burchet has found that the most sensitive approach is to use background quarters. “Even then, you have to find the gas as a shadow seen in the background quasar light,” he said.

Barchett U.S.C. Posted by Oscar Schlecker mentions this line of research on beers with Alec. More inspiration came from an improbable source. Alec’s mentor, Angus Forbes (second co-author), told him about the work of Sage Jensen, a Berlin-based media artist who was using a computer simulation of slim mold growth to create art, based on a 2010 paper by Jeff Jones. Journal of Artificial Life.

Alec was shocked by the growth patterns of slam molds in Jensen’s creations (you can see examples on his website), which showed similar filamentous features of the cosmic web. He and a programmer created a 3D version of a simulation for textile mold growth – dubbed the Monte Carlo Physaram Machine (MCPM) – and they plugged into the Sloan Digital Sky Survey (SDSS) dataset of 37,000 galaxies, just to see. Will happen.

Strength assessment for the MCPM model.  Some fine-level details are missing, but the overall structure is well preserved.
Zoom in / Strength assessment for the MCPM model. Some fine-level details are missing, but the overall structure is well preserved.

Joseph N. Burchett et al. / AJL

Given the already significant composition of the work using more traditional modeling approaches, Burchet admits to being a little skeptical when Alec first demonstrated the possibility. But the results worked surprisingly well. “Visually, it’s really amazing,” Birchett said. “If you look at a map of the galaxies in the sky, and the slim mold model fits that intuition very well, you can be healthy.” Just as slam molds create an optimized transport network, finding the most efficient ways to connect food sources, so the growth of structures in the cosmic web produces similarly optimal networks. The underlying processes for each are different, but they make the mathematical structures the same.

“It’s not that no one has proven that the cosmic web is a solid, mathematical reason why there should be a better transport network,” he said. “It just comes close to that. It was a more intuitive gut feeling that brought these things close enough to really work.”

MCPM, to verify results from Burchet Et al. Dark Matter created a catalog of haloes based on data from classic cosmological simulations, then ran an algorithm to rebuild the filamentary web connecting the haloes. The results are strongly related to the original cosmological simulation. Which enabled the team to further fix their slim mold model. As yet another “sanity investigation”, the team also compared the prediction of a slim mold model of gas density in the international medium with the star formation activity in the galaxy included in the SDSS.

Finally, they tested their model Dell’s predictions for the formation of a cosmic web against UV data from the Hubble Space Telescope’s Cosmic Origins Spectrograph qu 35050 quarts. “We knew that the filaments of the cosmic web were due to the texture of the fabric, so we could go to the archived Hubble Spectra for quarters that could explore the space and detect gas signatures.” “Wherever we saw the filament in our model, the Hubble Spectra showed a gas signal, and the signal toward the center of the fibers became stronger where the gas should be.” And as expected, in the Ga signal regions, where the gas gets too hot the signal stops, it becomes ionized, removing the sign of absorption.

There is still more interesting research to be done based on the success of MCPM. Brushchet focuses his attention on galaxies from the mapping of gases in the web filaments of the universe, and points out how well their properties are compatible with where they are in the cosmic web. As for Alec, he sees Slim Mold’s model Dell as a “structure finder” and is exploring how to potentially apply it to bioprinting, among other uses.

“We saw this as the tip of the iceberg of what we can do scientifically,” Birchet said. “This is splitting both cool applications inside and outside of astrophysics.”

DOI: Astrophysical Journal Letters, 2020. 10.3847 / 2041-8213 / ab700c (about DOI).