Quantum Physics: renormalization revisited (General)

by David Turell , Thursday, September 17, 2020, 20:15 (1526 days ago) @ David Turell

The lesson is not to try to be too small:

https://www.quantamagazine.org/how-renormalization-saved-particle-physics-20200917/

"Only by using a technique dubbed “renormalization,” which involved carefully concealing infinite quantities, could researchers sidestep bogus predictions. The process worked, but even those developing the theory suspected it might be a house of cards resting on a tortured mathematical trick.

“'It is what I would call a dippy process,” Richard Feynman later wrote. “Having to resort to such hocus-pocus has prevented us from proving that the theory of quantum electrodynamics is mathematically self-consistent.”

"Justification came decades later from a seemingly unrelated branch of physics. Researchers studying magnetization discovered that renormalization wasn’t about infinities at all. Instead, it spoke to the universe’s separation into kingdoms of independent sizes, a perspective that guides many corners of physics today.

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"Today, Feynman’s “dippy process” has become as ubiquitous in physics as calculus, and its mechanics reveal the reasons for some of the discipline’s greatest successes and its current challenges. During renormalization, complicated submicroscopic capers tend to just disappear. They may be real, but they don’t affect the big picture. “Simplicity is a virtue,” Fendley said. “There is a god in this.”

"That mathematical fact captures nature’s tendency to sort itself into essentially independent worlds. When engineers design a skyscraper, they ignore individual molecules in the steel. Chemists analyze molecular bonds but remain blissfully ignorant of quarks and gluons. The separation of phenomena by length, as quantified by the renormalization group, has allowed scientists to move gradually from big to small over the centuries, rather than cracking all scales at once.

"Yet at the same time, renormalization’s hostility to microscopic details works against the efforts of modern physicists who are hungry for signs of the next realm down. The separation of scales suggests they’ll need to dig deep to overcome nature’s fondness for concealing its finer points from curious giants like us.

“'Renormalization helps us simplify the problem,” said Nathan Seiberg, a theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey. But “it also hides what happens at short distances. You can’t have it both ways.'”

Comment: Quantum theory is as weird as ever, but it works. The universe is based on quantum mechanics, which tells us God works in mysterious ways. We are bright folks who always want to know how it works. Hopefully we'll figure it out.