Theoretical Physics

Everything is Physics

At the first of the Kavli institutes, theory goes to the heart of science and the science of the heart.

PHYSICISTS like to say that, if you look deeply into any branch of science, you’ll find physics at its core. Not every chemist, biologist or psychologist may agree with that notion, but the physicists do have a point: they study matter at its most basic, and the physical sciences ultimately are trying to explain how matter works, whether in black holes or brain cells.

Turf issues aside, the application of physics to a wide range of scientific issues can prove fruitful for everyone involved. At the Kavli Institute for Theoretical Physics (KITP) at the University of California, Santa Barbara, such cross-fertilization across the disciplines is a guiding principle. KITP “brings together people of different communities and focuses on problems that are on the boundary,” says Institute Director David Gross, who received the 2004 Nobel Prize in Physics.

A view of the KIPT building.

“A lot of what we do is in traditional areas of physics,” Gross says, “but physicists are very pluralistic, and they often see problems in non-traditional areas that they want to solve.” KITP’s schedule of programs reflects that view. The Institute hosts cardiologists and climate scientists as well as cosmologists and string theorists. He calls it “the pre-eminent users’ facility for theoretical physics where 'physics' is defined in a very broad sense.”

Uncovering the Dynamics of the Heart

A month-long program hosted by KITP in 2006, titled “Cardiac Dynamics,” showed how theoretical physics in that “broad sense” was applied to a medical challenge. More than 40 cardiologists, physicists and biomedical scientists met at the Institute to apply physics theory – specifically, non-linear dynamics – to the problem of irregular heartbeats. The list of organizers, which included three physicists from institutions in Germany, France and the U.S., along with a bioengineer and a physiologist from State University of New York and Cornell University, gives some idea of the program’s diversity and global appeal.

Through a series of talks, tutorials and discussions, the scientists explored the causes of cardiac arrhythmia. These disruptions in heart rhythm can lead to fibrillation – a quivering motion that stops the heart from pumping – and sudden death when they occur in a ventricle, one of the heart’s main pumping chambers. Diverging from the traditional view, which blames arrhythmias mainly on congenital flaws in the heart aggravated by disease, the Kavli program looked at how usually harmless turbulence in the electrochemical signals controlling the heart can spiral into lethal chaos. Two of the program’s organizers physicist – Alain Karma of Northeastern University and physiologist Richard Gilmour of Cornell – demonstrated some results of this approach in a March 2007 article in Physics Today, “Nonlinear Dynamics of Heart Rhythm Disorders.” Drawing on computer simulations and animal experiments, Karma and Gilmour identified certain premature-beat sequences that appear to produce ventricular fibrillation through their own dynamics.

Karma and Gilmour noted that their article grew out of the 2006 Kavli program. But published papers are not the typical outcome of KITP gatherings, which include mini-programs of two weeks to one month (“Cardiac Dynamics” was one of these) to full-scale programs of three months or more. “Usually what happens here is harder to document,” Gross says. People who come together at KITP seed their disciplines with new ideas that might show up in research years later.

An event that just got going could have an impact not just in research but in politics, given its subject matter. This is a program of about three months on the physics of climate, and more than 80 meteorologists, climatologists and physicists will participate. “Physicists are getting interested in climate like everyone else,” says Gross, and he sees plenty of “interesting questions” to explore.

The Physics Behind Global Warming

One of these is the complex relation of warming not just to cloud formation but to cloud height. One of the factors expected to influence climate in coming years is the increase in cloudiness due to warming of the earth’s

surface, which adds more water vapor to the atmosphere through evaporation. To some degree, clouds contribute to planetary cooling by reflecting solar radiation back into space in the so-called “albedo effect.” But that impact varies by the height of the cloud tops. High cloud layers have a greater cooling effect because they intercept and reflect sunlight before it can penetrate – and warm – most of the atmosphere. Low clouds let more radiation in and thus may accelerate global warming. Gross says no one really knows if clouds would form high or low with rising temperatures. Untangling this mystery would help improve climate prediction and give governments surer science and clearer direction in setting policies.

What exactly does physics offer to a climate scientist trying to come up with a forecast for the year 2050? One answer is the physicists’ focus on the dynamics of matter in all phases -- gas, liquid, solid – which gives them plenty to say about the action of air, water and ice when the three are subjected to heat. Theoretical physics also encourages a view of complex events (like climate change) as systems following intelligible rules. Gross suggests that it may be the light that climatologists need to find their way through a fog of daily weather data from thousands of stations. “The vast majority of people studying climate are observers who try to make predictions,” he says. “They don’t try to understand systems.”

KITP was founded in 1979 as the Institute for Theoretical Physics. It became the first of the Kavli institutes in 2002, with funding from Fred Kavli and an extension to its building. As in the past, it still does plenty of physics in the narrower sense. Recent and upcoming programs cover topics such as the Large Hadron Collider (a particle accelerator near Geneva, Switzerland), star formation, dynamo theory and non-equilibrium dynamics in particle physics and cosmology. These share the schedule with gatherings that focus on biological clocks and the anatomy and development of the human brain. KITP may not quite prove the point that everything is physics, but it does show that physics has something to say to scientists of all stripes.