In today’s first story, we’re going to call attention to the powerful role of computers in shaping our understanding of the universe and, in this case, in shaping our understanding of the shape of the universe.

Since the beginning of the computer age, researchers have been trying to simulate how a universe made of a mostly smooth swarm of particles can, over time, evolve into the galaxies and large-scale structures that we see today. Early models started by simulating increasingly large numbers of particles of regular material – the kinds of baryonic matter that make up us and everything we touch. Those simulations didn’t work really well – something was missing. 

Dark matter was added, and folks began fussing with how dark matter might be one temperature and the regular matter another, and models matched better, but the processing required got harder and harder since these two kinds of particles interact gravitationally but not so much collisionally, and the software had to keep everything straight. Still, it was progress. 

But there was still stuff missing – neutrinos for instance – and that stuff interacts more like dark matter than regular matter but is constantly coming into and out of existence through formation in stars and destruction in rare interactions. These ghost particles, as they’ve been nicknamed, are in the universe tweaking its evolution. As explained by project principal investigator Naoki Yoshida: …these particle-based methods cannot accurately reproduce collisionless damping—a key process in which fast-moving neutrinos suppress the growth of structure in the Universe. 

So his team created a simulation that included neutrinos: a simulation that ran on up to 147,456 nodes of seven million CPU cores. And their new universe in a digital box got that much closer to resembling the actual universe.

What got me about this work is that neutrinos aren’t just hanging out in our normal x,y,z+time universe. Including them required solving what’s called the Vlasov equation in six dimensions. Since our universe has at least eleven dimensions, models will still need to grow, but this is amazing progress.

I can’t wait to see what folks can create when we have quantum computers.

More Information

University of Tsukuba press release

“A 400 trillion-grid Vlasov simulation on Fugaku supercomputer: large-scale distribution of cosmic relic neutrinos in a six-dimensional phase space,” Kohji Yoshikawa, Satoshi Tanaka, and Naoki Yoshida, 2021 November 14, SC ’21: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis