There are times as an astronomer that I look at a research paper, know it is a potentially important paper, and my brain just says, “no.” That is the case with the next story we’re going to cover, and I’m not going to lie — many, many cups of coffee went into trying to make sense of this science.
Normally we wouldn’t inflict a journal article on you, but just this once, I feel compelled to share the introductory sentences of a Physical Review Letters paper that really wanted to put me to sleep: The asymmetry between matter and anti-matter is a cornerstone puzzle of modern particle cosmology, as the Standard Model fails to provide an explanation. An elegant paradigm for explaining the asymmetry is the Affleck-Dine mechanism. Supersymmetric theories generically have flat directions, which have non-zero baryon or lepton number. During inflation, a scalar condensate generically develops in these directions, whose non-zero vacuum expectation value (VEV) spontaneously breaks C and CP. At the end of inflation, a baryon and/or lepton asymmetry is generated as the VEV coherently evolves and the condensate fragments. These resulting clumps may be long-lived nontopological solitons (Q-balls), carrying either lepton or baryon number .
Hidden in that scientific language is a remarkable piece of information: researchers may have figured out why our universe is dominated by matter. This work is led by Graham White.
Here is the background you need: when our universe first formed, everything was energy. As the Universe expanded and cooled, that energy was able to condense out as particles. Theorists don’t understand why those particles weren’t half matter and half antimatter, but observers and computational modelers find that to explain the Universe we have today, for every ten billion antimatter particles, there must have been ten billion and one matter particles. Why? That has been a point of confusion.
In this new research, the idea is put forward that during the brief epoch of inflation in the first minute of the Universe, a field was responsible for driving the Universe ever larger. This field, like other fields, has associated particles and energies, and as the period of inflation came to an end, those particles decayed in a way that left an excess of matter and bundles of charged Q-balls. There is math to back the idea up, and it is math that requires a whole suite of new, supersymmetric particles to exist side by side with our known suite of particles.
We’ve been trying to find evidence of supersymmetry for a long time and have thus far totally failed, so the theory has a lot working against it.
While we can’t yet find supersymmetric particles, if they do exist, this paper lays out another possible way this paper can be proven: the team believes those Q-balls are temporary and when they decay, they would have enhanced the primordial gravitational waves that shaped our early universe. While we can’t peer into the pre-Cosmic Microwave Background universe because the microwave background is opaque, we can detect gravitational waves from that era. We don’t yet have the equipment to detect primordial gravitational waves, but maybe someday, and it is that maybe someday that makes this paper important; it offers a theory that is testable… eventually.
It also offers a really nice sleep aid; not all research is picturesque or can be written in exciting language. Still, even the science that wants to put me to sleep can be important to understanding our universe.
Kavli IPMU press release
“Detectable Gravitational Wave Signals from Affleck-Dine Baryogenesis,” Graham White, Lauren Pearce, Daniel Vagie, and Alexander Kusenko, 2021 October 27, Physical Review Letters