Waterloo scientists have developed a new way to understand how the universe began, and it could change what we know about the Big Bang and the earliest moments of cosmic history. Their work suggests that the universe’s rapid early expansion could have arisen naturally from a deeper, more complete theory of quantum gravity. The paper, “Ultraviolet completion of the Big Bang in quadratic gravity,” appears in Physical Review Letters.

Dr. Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo and Perimeter Institute (PI), led the research team that explored a novel method of combining gravity with quantum physics, the rules that govern how the smallest particles in the universe behave. While general relativity has been successful for more than a century, it breaks down at the extreme conditions that existed at the birth of the universe. To address this problem, the team used Quadratic Quantum Gravity, which remains mathematically consistent even at extremely high energies—similar to the kind present during the Big Bang.

Most existing explanations for the Big Bang rely on Einstein’s theory of gravity, plus additional components added by hand. This new approach offers a more unified picture that connects the earliest moments of the universe to the well-tested cosmology scientists observe today.

Dark matter, a type of matter that does not emit, reflect or absorb light, is predicted to account for most of the matter in the universe. As it eludes common experimental techniques for studying ordinary matter, understanding the nature and composition of dark matter has so far proved very challenging. One hypothesis is that it is made up of hypothetical particles known as quantum chromodynamics (QCD) axions. These are theoretical elementary particles that would interact very weakly with ordinary matter and are predicted to be extremely light, highly stable and electrically neutral.

While several large-scale studies have searched for small signals or effects that would indicate the presence of these particles or their interaction with ordinary matter, their existence has not yet been confirmed experimentally. In a paper recently published in Physical Review Letters, researchers at Perimeter Institute, University of North Carolina, Kavli Institute and New York University have introduced a new approach to search for QCD axions using a class of materials that generate electric fields when deformed, called piezoelectric materials.

“The axion was proposed in the late 1970s by Weinberg and Wilczek, as a solution to the strong CP (Charge-Parity) problem, a long-standing puzzle in the theory of the strong nuclear force,” Amalia Madden, co-senior author of the paper, told Phys.org.