From Brown University via Futurism: “Dark Matter May Be a Product of Gravitational Waves with a Twist”

Brown University
Brown University

futurism-bloc

Futurism

February 12, 2018
Dom Galeon

1
Give us a wave! Right-handed or left-handed? Henze/NASA.

It is said that the universe is made up of over 80 percent dark matter. What dark matter exactly is, however, has continued to elude experts. Theories abound, and a recent one suggests an entirely different approach involving gravitational waves.

Breaking Symmetry

For decades now, the exact composition of matter in the universe has baffled astronomers and physicists alike. It would seem that, given the basic assumptions about the origins of the universe, there is still no way to account for the “missing” dark matter that makes up for as much as a quarter of all matter in the universe. That’s why a trio of researchers has proposed a new dark matter theory, which could explain how dark matter came about.

We know dark matter exists because we can observe how its gravity interacts with visible matter and electromagnetic radiation. There is something there, although we can’t yet see it, or put a finger on what it is.

In the new study, Evan McDonough and Stephon Alexander from Brown University, with David Spergel from Princeton University, suggest that a mechanism involving gravitational waves — basically, ripples in the fabric of space and time, first theorized by Einstein and confirmed to exist only in 2016 — could explain how dark matter came to be.

McDonough’s team used a model of the primordial universe that assumed the presence of particles called dark matter quarks, which aren’t the same as today’s dark matter. These dark quarks could have a property called chirality, referring to the way the particles twist, similar to neutrinos. The chirality or “handedness” of these dark quarks could have then interacted with the chiral gravitational waves in the early universe, producing the kind of dark matter we have today.

Lighter and Wimpier

Supposedly, as the universe settled into a cooler state, the interactions between chiral dark quarks and chiral gravitational waves resulted in a small excess of the former. These condensed into a quirky state of matter called a superfluid, which could still exist as a background field today. What we know to be dark matter are proposed as excitations of this background field, in the same way photons are excitations of an electromagnetic field.

Interestingly, the dark matter particles resulting from such a model would be lighter than what’s known as weakly interacting massive particles (WIMPs), which many researchers believe could make up dark matter. There hasn’t been enough evidence to suggest, however, that this is the case. At any rate, being lighter than WIMPs would mean that dark matter wouldn’t interact with normal matter. “It’s much wimpier than WIMPs,” Spergel told New Scientist.

As such, this dark matter theory could change how we should “look” for dark matter, as it wouldn’t be possible to see such particles directly at all. Unlike WIMPs, these particles would also be distributed more evenly across the galaxy. At the same time, the ratio of dark matter and normal matter wouldn’t necessarily be constant throughout the universe.

Spergel explained, however, that this unique behavior could also provide us with a way to find dark matter. A more uniform, non-clustered distribution of dark matter could spill over into cosmic microwave background — the Big Bang’s residual radiation — and produce a unique signature. It could even affect the formation of larger-scale structures, like galaxy clusters. It could also, perhaps, have an effect on gravitational waves.

In any case, any new dark matter theory is certainly a welcome one, as experts continue exploring other possibilities to account for dark matter — or even dismiss it altogether.

“It’s a cool idea,” Stanford University’s Michael Peskin, who wasn’t part of the study, told New Scientist. “Right now, dark matter is completely open. Anything you can do that brings in a new idea into this area, it opens a door. And then you have to walk down that corridor and see whether there are interesting things there that suggest new experiments. This opens another door.”

See the full article here .

Please help promote STEM in your local schools.

STEM Icon

Stem Education Coalition

Futurism covers the breakthrough technologies and scientific discoveries that will shape humanity’s future. Our mission is to empower our readers and drive the development of these transformative technologies towards maximizing human potential.

Welcome to Brown

Brown U Robinson Hall
Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.