Need new physics? Experts discuss the possibility of updating fundamental concepts of physics

An unexpected discovery about the formation of our universe raises the question again: Do we need new physics? The answer could fundamentally change the way physics students are taught around the world.

A study by SMU and three other universities, available on the arXiv preprint server, investigated the possibility of updating fundamental concepts of physics.

SMU played a significant role in the analysis, using the university’s high-performance computing capabilities to explore different scenarios that could explain the results.

“The DESI (Dark Energy Spectroscopic Instrument) data, combined with what we already have, is the most precise data we’ve seen so far, and it suggests something different than what we expected,” said study co-author Joel Meyers, an associate professor of physics at SMU. “Now we need to understand why this is happening.”

Theoretical physicists Nathaniel Craig of UC Santa Barbara and the Kavli Institute for Theoretical Physics, Daniel Green of UC San Diego and Surjeet Rajendran of Johns Hopkins University worked with Meyers on this analysis.

What DESI discovered…and why it was surprising

DESI creates the largest and most accurate 3D map of our universe, providing a key measurement that allows cosmologists to calculate what they call the absolute neutrino mass scale.

This absolute mass scale was determined based on new measurements of DESI’s baryon acoustic oscillations, as well as information physicists already had about the “afterglow” from the Big Bang (when the universe was created), known as the cosmic microwave background.

Throughout the evolution of the universe, the behavior of neutrinos has impacted the growth of large-scale structures, such as the galaxy clusters we see today in the vast expanses of space. Neutrinos are one of the most abundant subatomic particles in the universe, but they are as mysterious as they are ubiquitous. One reason physicists want to know the mass scale of neutrinos is that it can help them better understand how matter clumped together as the universe evolved.

Cosmologists, those who study the origin and development of the universe, have long believed that massive neutrinos prevented matter from clumping together as much as it could have over 13.8 billion years of cosmic evolution.

“But rather than the expected suppression of matter clumping, the data instead favors enhanced matter clumping, meaning that matter in the cosmos is more clumped than we might expect,” said Meyers, who specializes in theoretical cosmology, including the cosmic microwave background, the early universe, and connections to high-energy and particle physics.

“Explaining this improvement could indicate a problem with the measurements, or it could require new physics not included in the Standard Model of particle physics and cosmology.”

The Standard Model of particle physics, the one students probably learned in physics class, has long been scientists’ best theory for explaining how the building blocks of matter interact. This neutrino discovery is the latest measurement, similar to what’s known as the “Hubble tension,” that suggests we may not know our universe as well as we think, Meyers said.

In their study, Meyers and his colleagues looked at scenarios in which physicists might need to modify the Standard Model, without rejecting it altogether. They also looked at the introduction of new physics concepts. They also investigated whether systematic errors in key measurements could explain DESI’s surprising discovery.

It will likely take years to know which of the researchers’ theories is correct. But the study provides a model for future research.