Amidst the usual containers of coffee and plain hardback chairs, the company of "The Physicists" started rehearsing yesterday in an otherwise bare room at the Kennedy Center and quietly began what producer Roger L. Stevens called "a new phase of our operations."

The eminent company for this play, the first of what has been dubbed the New Eisenhower Theater Season, includes Irene Worth, Brian Bedford, Len Cariou and George Grizzard -- three of them Tony Award winners. They are the first in what Stevens hopes will evolve into a national theater repertory company over the next three or four years.

"I'd like to gradually slide into a nucleus of people," said Stevens, who is using as models Britain's National Theater and Royal Shakespeare Company, and San Francisco's American Conservatory Theater (ACT). He envisions, in addition to a corps of secondary players, a series of well-known actors who would commit themselves to a 10-week stay here to rehearse and present a "play of real value." For example, he was quite smitten with Sally Field after seeing her in her new film, "Absence of Malice," and would like to get her to do a play. "She's done theater," he said. "I checked her bio."

Two-thirds of the cost of this season is being underwritten by CBS/Broadcast Group, an arrangement that is expected to last at least two more seasons. "If we can build up a following, it will work," said Stevens, who predicted a need for 20,000 subscribers to make a viable resident repertory theater of national stature.