The physics, the math – evolution of computational physics

[“What’s changed in the last ~50 years” series]

Some of my more interesting work as a systems engineer at Hughes was on projects with satellite hardware engineers. In the days where they still wrote much of their own “software” for operating payloads. Maybe a few thousand lines of code. Often quick-and-dirty. Over the decades, that evolved to millions of lines of code. And career software engineers.

Something similar has evolved for particle physics. The tango / interplay of doing the physics and doing the math. The evolution of computational physics and the challenge of viable career paths and institutional knowledge.

• Symmetry Magazine > “The coevolution of particle physics and computing” by Stephanie Melchor (9-28-2021)

(quote) The incredible computational demands of particle physics and astrophysics experiments have consistently pushed the boundaries of what is possible.

As computing has grown increasingly more sophisticated, its own progress has enabled new scientific discoveries and breakthroughs.

Historical recap: Fermi Lab … mainframes … Tevatron … analyzing data from millions of particle collisions per second … microprocessor clusters … CERN … World Wide Web … SLAC National Accelerator Laboratory … Moore’s Law … computational nodes … supercomputers … simulations … Department of Energy’s Exascale Computing Project (exascale computers) … machine learning … quantum computers … National Quantum Initiative Act of 2018 …

(quote) In 1989, in recognition of the growing importance of computing in physics, Fermilab Director John Peoples elevated the computing department to a full-fledged division.

For more than a decade, supercomputers … have been providing theorists with the computing power to solve with high precision equations in quantum chromodynamics, enabling them to make predictions about the strong forces binding quarks into the building blocks of matter.

And although astrophysicists have always relied on high-performance computing for simulating the birth of stars or modeling the evolution of the cosmos, [Berkeley Lab astrophysicist] Nugent says they are now using it for their data analysis as well.

To properly correct for detector effects when analyzing particle detector experiments, they need to simulate more data than they collect. “If you collect 1 billion collision events a year,” [Berkeley Lab physicist] Calafiura says, “you want to simulate 10 billion collision events.”

Machine learning has been important in particle physics as well, says Fermilab scientist Nhan Tran. “[Physicists] have very high-dimensional data, very complex data,” he says. “Machine learning is an optimal way to find interesting structures in that data.”

In quantum computers, qubits rely on superposition in quantum physics, and someday perhaps permit simultaneous analysis of particle interactions for all possible paths. So, we might better examine multi-dimensional ripples (in space-time). Quantum fluid dynamics.

(quote) “Quantum chemistry problems are hard for the very reason why a quantum computer is powerful” — because to complete them, you have to consider all the different quantum-mechanical states of all the individual atoms involved.

Multiple forces are always at play, so to accurately model real-world complexity, you have to use more complex software—ideally software that doesn’t become impossible to maintain as it gets updated over time. “All of a sudden,” says Dubey [computational scientist at Argonne National Laboratory], “you start to require people who are creative in their own right—in terms of being able to architect software.”

That’s where people like Dubey come in. At Argonne, Dubey develops software that researchers use to model complex multi-physics systems—incorporating processes like fluid dynamics, radiation transfer and nuclear burning.

Complexity requires visualization, which is another computational story.