• Research
In biology, phylogenetic trees represent the evolutionary history and diversification of species – the “family tree” of Life. Phylogenetic trees not only describe the evolution of a group of organisms but can also be constructed from the organisms within a particular environment or ecosystem, such as the human microbiome. In this way, they can describe how this ecosystem evolved and what its functional capabilities might be.

Now, researchers at Illinois have presented a new analysis of the patterns generated by phylogenetic trees, suggesting that they reflect previously hypothesized connections between evolution and ecology. The study was led by Swanlund Professor of Physics Nigel Goldenfeld (BCXT leader/GNDP), with team members graduate student Chi Xue and former undergraduate student Zhiru Liu, now at Stanford University. Their findings were published in a recent article in the journal Proceedings of the National Academy of Science, titled “Scale-invariant topology and bursty branching of evolutionary trees emerge from niche construction.”

  • Research

The charge of a single electron, e, is defined as the basic unit of electric charge. Because electrons—the subatomic particles that carry electricity—are elementary particles and cannot be split, fractions of electronic charge are not normally encountered. Despite this, researchers at the University of Illinois at Urbana-Champaign have recently observed the signature of fractional charges ranging from e/4 to 2e/3 in exotic materials known as topological crystalline insulators.

The team of researchers, led by Illinois Mechanical Science and Engineering Professor Gaurav Bahl and Illinois Physics Professor Taylor Hughes, has been using ultra high frequency electric circuits to study topological insulators since 2017. Their recent measurement of fractional charge, appearing in the current issue of the journal Science, stems from the team’s theoretical work on crystalline insulators.

Find out how you can shine with solar energy, even if you do not always get direct sunlight. In this discussion with an Illinois Solar Energy Association Solar Ambassador, you will learn:

  • How solar energy works in Illinois
  • The benefits and challenges of residential solar energy
  • The upfront costs and long-terms savings, including current financial incentives in Illinois
  • Considerations for properties with shade
  • Resources for finding reputable installers
  • In the Media
  • Research

The theory behind dark matter detection dates back to a 1985 paper that considered how a neutrino detector could be repurposed to look for particles of the substance. The study proposed that an incoming dark matter particle could hit an atomic nucleus in the detector and give it a kick—similar to one billiard ball crashing into another. This collision would transfer momentum from the dark matter, walloping the nucleus hard enough to make it spit out an electron or a photon.

At high energies, this picture is essentially fine. Atoms in the detector can be thought of as free particles, discrete and unconnected to one another. At lower energies, however, the picture changes.

“Your detectors are not made of free particles,” says Yonatan (Yoni) Kahn, a dark matter theorist at the University of Illinois at Urbana-Champaign and a co-author of the first paper. “They’re just made of stuff. And you have to understand the stuff if you want to understand how your detector actually works.”

For decades, scientists studying the muon have been puzzled by a strange pattern in the way muons rotate in magnetic fields, one that left physicists wondering if it can be explained by the Standard Model — the best tool physicists have to understand the universe.

This week, an international team of more than 170 physicists published the most reliable prediction so far for the theoretical value of the muon’s anomalous magnetic moment, which would account for its particular rotation, or precession. The magnetic moment of subatomic particles is generally expressed in terms of the dimensionless Landé factor, called g. While a number of international groups have worked separately on the calculation, this publication marks the first time the global theoretical physics community has come together to publish a consensus value for the muon’s magnetic moment.

Research Highlights

Article abstract: We derive the general analytical solution of the viscous hydrodynamic equations for an ultrarelativistic gas of hard spheres undergoing Bjorken expansion, taking into account effects from particle number conservation, and use it to analytically determine its attractor at late times. Differently than all the cases considered before involving rapidly expanding fluids, in this example the gradient expansion converges. We exactly determine the hydrodynamic attractor of this system when its microscopic dynamics is modeled by the Boltzmann equation with a fully nonlinear collision kernel. The exact late time attractor of this system can be reasonably described by hydrodynamics even when the gradients are large.

Illinois Physics Response to COVID-19

The COVID-19 pandemic presents complex challenges that bridge science and teaching with economics and politics. Illinois Physics faculty are hard at work addressing some of these challenges. Here are just a few examples.

  • Physics faculty, teaching assistants bring hands-on labs to students online
  • Cena y Ciencias outreach program continues to reach kids by delivering take-home science kits
  • Weissman helps local medical residents with COVID-19 statistical analysis

donor stories

Alumnus gift continues legacy of excellence at Illinois Physics

“We deeply appreciate Gary Kelly’s generosity and his investment in our department’s core missions of research, teaching, and outreach,” comments Head of Department and Professor Matthias Grosse Perdekamp. “Unrestricted funds such as these are applied where they will make the greatest impact. Through his generosity, Gary Kelly’s legacy at Illinois will include his support of important new opportunities directly in line with our core missions. A large portion of Gary’s gift will support the research of exceptional women faculty early in their careers, enabling Illinois Physics to attract and retain promising women physicists.”

Engineering Visionary Scholarships

Sara Shahid

Give to the Engineering Visionary Scholarship. EVS attracts the brightest students, ensures a diverse and talented class, and helps reduce student debt.

“The relief of financial burden this scholarship has lifted from my family‚Äôs shoulders is truly a priceless gift, and the generosity of donors that have made this possible inspires me to want to give others this same gift of relief, security, and most of all educational opportunity, as it has done for me.”

— Sara Shahid, Engineering Physics Class of '22, EVS Scholarship recipient

Learn more

Watch Professor Nadya Mason's TED talk!

Watch Professor Nadya Mason's TED talk!

Curious how stuff works? Do a hands-on experiment at home, says physicist Nadya Mason. She shows how you can demystify the world around you by tapping into your scientific curiosity -- and performs a few onstage experiments of her own using magnets, dollar bills, dry ice and more.

Watch the Center for the Physics of Living Cells video

Watch the Center for the Physics of Living Cells video

The Center for the Physics of Living Cells is an NSF Physics Frontiers Center. In true "Urbana style," theoretical and experimental scientists collaborating at the CPLC are elucidating the fundamental processes at the core of life in quantitative physical detail.  The CPLC Summer School is world renowned for its training of young scientists in leading-edge research methods, advancing this interdisciplinary physics frontier.


In our high school physics, we learn that magnetic force does not do work. But why do bar magnet stick together. Our hands feel force and they really move in that direction. It seems that some sort of work is done.

Events this week

1 p.m.
Yang Bai, University of Illinois at Urbana-Champaign