FOR conquering infinity, two Dutch physicists have won this year鈥檚 Nobel
Prize in Physics. Gerardus 鈥榯 Hooft of the University of Utrecht and Martinus
Veltman, Emeritus Professor of Physics at the University of Michigan, won the
prize for banishing meaningless infinite results from the equations of quantum
mechanics鈥攁 problem that had dogged the theory for decades.
The laws of quantum mechanics dictate that the subatomic world is swimming
with 鈥渧irtual鈥� particles. Everywhere in space, particles are constantly winking
in and out of existence. For instance, around every electron there is a shroud
of virtual particles that hide the electron鈥檚 true charge.
Until the 1970s, quantum theory suggested that if physicists were somehow
able to strip away the virtual particles bit by bit, they would find that the
electron鈥檚 measured charge gets greater and greater, eventually becoming
infinite.
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Such nonsense results undermined the framework of quantum theory, so
physicists had to find some way of getting rid of them. The key to this is a
procedure called 鈥渞enormalisation鈥�, invented in the 1940s by Richard Feynman,
Julian Schwinger and Sin-Itiro Tomonaga. They won the 1965 physics Nobel for
their work, which purged infinities such as that of the electron鈥檚 charge from
the theory of electromagnetism.
But problems still remained. The weak force, which is responsible for
radioactive decay, and the strong force, which holds the nucleus of atoms
together, had their own infinities, analogous to those in electromagnetism. And
when physicists came up with a theory of how the electromagnetic and weak forces
acted as one in the early Universe, their 鈥渆lectroweak鈥� force turned out to have
the same affliction. 鈥淵ou couldn鈥檛 do anything with the theory,鈥� Veltman
recalls.
In the 1970s, 鈥榯 Hooft and Veltman solved the problem. They did this by using
mathematical descriptions called gauge theories, which got rid of the infinities
in the strong and electroweak forces. 鈥淎fter renormalisation, it was clear that
the theory made sense,鈥� says Ed Witten of the Institute for Advanced Study in
Princeton, New Jersey.
The electroweak theory was on track to make a successful comeback. 鈥淓veryone
had forgotten about it, but when the mathematical framework became known,
someone took it out of the refrigerator,鈥� says Veltman.
The work also threw up something unexpected: it suggested that certain
particles that nobody had ever seen must exist, including one called the top
quark. It also gave scientists some clues to how heavy the top quark should be.
鈥淭he theory without the top quark would be anomalous,鈥� says physicist Juan
Maldacena of Harvard University. 鈥淚t would not be possible to renormalise.鈥�
Time proved 鈥榯 Hooft and Veltman right. In 1995, physicists at Fermilab, near
Chicago, reported sighting the top quark in their accelerator experiments.
When 快猫短视频 spoke to Veltman last week, he was exhausted by
all the drama following the Nobel award. 鈥淩ight now, I need a nap,鈥� he said.