Do Slime Molds Dream of Dark Matter Universes?

A simple single-cell organism that may be growing on your lawn is helping astronomers probe the largest structures in the universe.

The orgamism is no other than Physarum polycephalum, a slime mold with an uncanny ability to seek out food sources, which has proved very efficient in solving labyrinthine mazes and other shortest path problems.

A team of astronomers has now turned to slime mold to help them model the so called cosmic web, the universe’s large-scale network of thread-like formations (filaments) of gravitationally bound galaxies, with a typical length of 200 to 500 million light-years that form the boundaries between large voids in the universe.

The cosmic web is supposed to consist fundamentally of dark matter. As its name suggests dark matter cannot be seen. Physicists have been forced to introduce it in order to account for gravitational effects that cannot be explained by accepted theories of gravity (e.g. general relativity). Dark matter is thought to account for approximately 85% of the matter in the universe and about a quarter of its total energy density.

The researchers turned to slime mold simulations when they were searching for a way to visualize the theorized connection between the cosmic web structure and the cool gas detected in previous Hubble spectroscopic studies.

The simulation art of Sage Jenson, a Berlin-based media artist, inspired the idea of a possible connection between the morphology of Physarum Polycephalum and the intergalactic medium structure.

Physarum, by Sage Benson

A key diculty in identifying Cosmic Web structures such as those filaments is the heavily under-constrained nature of the problem to reconstruct a physically plausible 3D structure out of sparse and often heterogeneous observations.

To solve this problem the team developed a generative model inspired by the work of Jeff Jones, who proposed an agent-based algorithm to mimic the growth and development of the Physarum polycephalum slime mold, a kind of virtual Physarum machine. They seeded the algorithm with the charted positions of 37,000 galaxies and ran it to generate a filamentary map.

It’s really fascinating that one of the simplest forms of life actually enables insight into the very largest-scale structures in the universe,

Joseph Burchett University of California (UC), Santa Cruz, Slime Mold Simulations Used to Map the Dark Matter Holding the Universe Together

It is a nice kind of paradox (and funny irony) that a humble organism like Physarum can help us try to understand such a dark theoretical conundrum.

Cosmic Web reconstruction using 37,662 galaxies with Monte Carlo Physarum Machine (MCPM) algorithm

Modern cosmology predicts that matter in our Universe has assembled today into a vast network of filamentary structures colloquially termed the Cosmic Web. Because this matter is either electromagnetically invisible (i.e., dark) or too difuse to image in emission, tests of this cosmic web paradigm are limited. Wide-field surveys do reveal web-like structures in the galaxy distribution, but these luminous galaxies represent less than 10% of baryonic matter. Statistics of absorption by the intergalactic medium (IGM) via spectroscopy of distant quasars support the model yet have not conclusively tied the difuse IGM to the web. Here, we report on a new method inspired by the Physarum polycephalum slime mold that is able to infer the density eld of the Cosmic Web from galaxy surveys.

Burchett, Joseph N., Oskar Elek, Nicolas Tejos, J. Xavier Prochaska, Todd M. Tripp, Rongmon Bordoloi, y Angus G. Forbes. «Revealing the Dark Threads of the Cosmic Web». The Astrophysical Journal 891, n.o 2 (marzo de 2020): L35. https://doi.org/10.3847/2041-8213/ab700c.

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