Americans James W. Cronin of the University of Chicago and Val L. Fitch of Princeton University have been given the 1980 Nobel Prize in physics for their groundbreaking research on the "big bang" theory of the origin of the universe, the Swedish Academy of Sciences announced yesterday in Stockholm.

The academy cited them for their 1963 discovery that certain subatomic particles do not conform to what physicists had long thought was an absolute principle of symmetry.

Many scientists now believe the two physicists' findings provide essential support -- and eventually may help explain -- the theory that the universe was created 10 billion years ago with a gigantic explosion, a "big bang," and has been expanding ever since.

Cronin and Fitch made the discovery while professors at Princeton, jointly heading a research group at Brookhaven National Laboratory in New York. Their studies involved the use of a proton accelerator to analyze a new type of elementary particles, called Kmesons.

Kmesons, created in collisions of protons, have a lifespan ranging from a billionth to one ten-millionth of a second. During that brief span, they switch back and forth from being particles to being antiparticles. Antiparticles have the opposite charge of particles and are a form of antimatter.

According to what had been thought an absolute principle of symmetry, the rate of the switch from particle to antiparticle would have been identical to the rate of the switch in the opposite direction. Some scientists used the principle to contest the big bang theory of the creation of universe, arguing that equal amounts of matter and antimatter -- postulated to come to being in such a blast -- would destroy each other immediately.

But Fitch and Cronin found that the two rates are measurably different, and thus unaffected by the principle known as "symmetry under the reversal of the arrow of time."

Fitch, now 57, remains at Princeton as chairman of its physics department. Cronin, since 1971, has been on the faculty at the University of Chicago.

"What the Cronin-Fitch discovery revealed was a breakdown in this pillar of physics," commented Prof. Sam Treiman, a Princeton colleague of Fitch.

Treiman is one of the number of scientists who have been using the discovery in attempts to support and explain the big bang theory. Under the symmetry principle, if a big bang did occur, there should now exist in the universe equal amounts of particles and antiparticles, of matter and antimatter.

Some scientists theorized for a time that our own galaxy had an antimatter duplicate somewhere else in the universe.

However, the Fitch-Cronin finding of an exception to the symmetry rule might explain why there has been little evidence of antimatter elsewhere in the universe and why a big bang might have resulted in an asymmetrical universe.

"The traditional view is that this [asymmetry] was the whim of the Creator and so beyond physical explanation," observed Treiman. He said the Fitch-Cronin discovery, "taken together with other recent theoretical developments," may explain the imbalance.

"Someone in my position has Kmesons for breakfast, lunch and dinner, and has to keep in mind that everybody else doesn't," said Fitch, after trying to explain his finding.

A quiet man who is an enthusiastic jogger, Fitch ran three miles this morning after being awakened by a phone call from a wire service reporter who broke the news to him.

Later, after he had returned and showered, a friend asked how he felt -- referring to the award. "All right," he replied, "I had a good run." f

At a press conference, Fitch lamented what he called a decline in American funding of basic experimental research.

"Clearly there was a marvelous research opportunity at the time," he said of the period during which he made the discovery. "The situation is not the same today. The country has not seen fit to invest in research . . . I guess it's part of the antitechnology movement and the greening of America."

He said he's been warned by fellow Princeton Nobel prize winner Philip W. Anderson, also a physicist, that the prize "gives one innumerable opportunities to pontificate on any and all subjects. I'll try to avoid that, but I will speak out on more research funding."

Fitch and Cronin will divide the Nobel Prize stipend of $212,000.