LOGAN, UTAH, USA -- Exactly 100 years ago, famed Austrian physicist Erwin Schrödinger (yes, the cat guy) postulated his eponymous equation that explains how particles in quantum physics behave. A key component of quantum mechanics, Schrödinger's Equation provides a way to calculate the wave function of a system and how it changes dynamically in time.
"Quantum mechanics, along with Albert Einstein's theory of general relativity are the two pillars of modern physics," says Utah State University physicist Abhay Katyal. "The challenge is, for more than half a century, scientists have struggled to reconcile these two theories."
Quantum mechanics, says Katyal, a doctoral student and Howard L. Blood Graduate Fellow in the Department of Physics , describes the behavior of matter and forces at the subatomic level, while general relativity explains gravity on a large scale.
"Many unknowns in physics are explained by one side or the other, but these explanations are often incompatible," says Oscar Varela, associate professor and Katyal's faculty mentor. "Quantum gravity is an attempt to combine these theories but, to this day, we don't know what quantum gravity is."
In the quest toward finding the correct theory of quantum gravity, Varela and Katyal, with former USU postdoctoral fellow Ritabrata Bhattacharya, describe their progress in testing the holographic principle which, they say, is a key property of any valid theory of quantum gravity. The team published their findings in the April 6, 2025 online issue of the American Physical Society's Physical Review Letters. Their research is supported by the National Science Foundation Elementary Particle Physics-Theory program.
"Proposed theories of quantum qravity are difficult to test experimentally because we don't have the technology to predict effects occurring at extremely high energies or extremely small scales," Varela says. "For theoretical physicists like us, a precise mathematical model is akin to the apparatus of an experimental physicist: It can be used to make predictions about the physical world."
For the USU team, the holographic principle is the vehicle to push forward toward a new frontier in physics thought.
"The holographic principle is our model to make predictions about quantum gravity," Varela says.
