image: Cal Poly physics Assistant Professor Ben Shlear works with students on early universe cosmology theoretical study.
Credit: Photo by Alexis Kovacevic
Investigations into the unknowns of space and time -- and abstract questions around early universe cosmology relating to the Big Bang, black holes and universe expansion -- are focal points of ongoing research led by Cal Poly physics Assistant Professor Ben Shlaer.
Shlaer is the 2024-25 recipient of the Astronomy Faculty Research Fellowship, now in its third year at Cal Poly, and his work involves three different astrophysics and cosmology projects.
The program is supported by a generous donation from the Marrujo Foundation, established by Dan and Rosamaria Marrujo.
“I’ve always been very excited by the big picture and some of my previous mentors have been giants in the field of cosmology,” Shlaer said. “Their work tends to be optimistic. They aim pretty high. And that kind of rubbed off on me.”
The funding relieves faculty from teaching duties so that they can work closely with students on research.
Shlaer is working with three separate studies, one involving three current physics majors, and two with recent graduates that explore fundamental mysteries of the universe.
“There's no natural understanding of initial conditions of the universe,” Shlaer said. “But all of the physics we’ve ever developed is really a theory of how to predict what happens from certain initial conditions.”
Shlaer and his current students are trying to sidestep the thorny issue of initial conditions by basing their work on a model that predicts that time must flow backwards and forwards, and almost all motions can be reversed.
Therefore, a collapsing universe can stop collapsing and start expanding, regardless of the pull of gravity.
“By allowing for time, as perceived by gravity, to not always be increasing, but to decrease and then increase, that mimics the possibility of a collapsing universe that then re-expands,” Shlaer said. “But the mechanism that causes the universe to expand, and to produce the Big Bang, is that time itself is what’s reversing.”
Using the time-reversal theory, a Shlaer research team of recent Cal Poly graduates are proposing what could be called an explanation for the Big Bang; another team is using the model to investigate the interior structure of black holes.
Shlaer’s current student team of students Josiah Hauck, Aaron Whorl and Sanjay Sreejith are researching whether a time-reversal model can explain dark energy (the mysterious force that causes the observed accelerated expansion of our universe) in a more natural way than other theories.
Admittedly, Shlaer said a particular question his current student team is trying to answer is a lofty one: “Why is the universe so big?”
“It's really a tough mystery, because people have worked on (the cosmological constant problem) for 50 years and have not made much progress at all,” Shlaer said. “So, it's a bit of a pie in the sky problem, but I think we have a tool that really can solve it.”
Hauck said that his team’s research thus far has delved into exciting enigmas. They read existing academic literature and use mathematics and physics formulas to try to tackle puzzling problems.
“The questions we’re trying to answer are still being asked in the field,” Hauck said. “As an undergraduate researcher, our study is a great opportunity, even if it can be hard to conceptualize. I want to develop the skills of being able to approach a problem from a more theoretical approach.”
Whorl said the work challenges “a different part of your brain that you have to engage.”
Shlaer’s teams apply a model of “non-singular general relativity,” a modification of gravity that doesn't have singularities, or the point in time where gravity is so intense that it breaks down spacetime catastrophically and the density of matter becomes infinite.
Did the universe start with a singular Big Bang out of nothing? Or was it a bounce that involves a cycle of expansion and collapse after the universe emerged from a prior universe that collapsed until it became extremely dense? Shlaer’s teams hope their work can move closer to answering these types of questions.
“I'm very excited to have this fellowship with the time to focus on this fascinating research,” Shlaer said. “Thanks to the Marrujo Foundation, we expect to finish all three of these projects during winter and spring quarters, and to submit three manuscripts to journals for publication by the end of the year (roughly one per quarter). I’m thrilled our students have to opportunity to be part of this work to do high level research as undergraduates.”