NEW YORK (AP) _ Cambridge University theorist Stephen W. Hawking _ regarded by some as one of Albert Einstein's intellectual successors _ has conceded defeat in a famous six-year-old bet.

Hawking bet two professors at the California Institute of Technology that naked singularities _ variations on a cosmological phenomenon believed to lurk at the hearts of black holes _ could not exist.

Now it seems they could _ maybe.

The New York Times reports Wednesday that during a visit to Caltech last week, Hawking conceded defeat ``on a technicality'' to fellow physicists John P. Preskill and Kip S. Thorne. The stake was 100 pounds (about $164), plus clothing ``embroidered with a suitable concessionary message.''

Hawking, Preskill and Thorne are leaders in the study of relativity as applied to cosmology, and they meet often at scientific symposiums, discussing conjectures about time machines, wormholes, the origin of the universe and other questions.

Although he was unable to prove his disbelief in naked singularities, Hawking, the author of ``A Brief History of Time,'' proposed his bet at one such meeting in 1991. Because of its far-reaching theoretical implications, news of the bet spread widely among physicists.

For the unititiated, a singularity is a mathematical point at which space and time are infinitely distorted, where matter is infinitely dense, and where the rules of relativistic physics and quantum mechanics break down.

Singularities are believed to lurk at the center of black holes, which conceal their existence from the outer world. A naked singularity would be a singularity bereft of a concealing black-hole shell, and therefore visible, in principle, to outside observers.

Although neither light nor any other kind of signal can escape from them, a half-dozen or so black holes have been revealed by their gravitational effects of nearby stars. Black holes also have betrayed their presence by sucking matter from nearby space. As the matter spirals toward the hole, it is heated to incandescence, and the emission of X-rays and other radiation has been detected by observatories in space and on the ground.

Preskill and Thorne won the bet last week on the strength of supercomputer calculations by Matthew Choptuik of the University of Texas in Austin. Choptuik concluded from his mathematical analysis that there could be special circumstances in which a naked singularity might be created from a collapsing black hole, either by nature or perhaps even by some advanced civilization.

The chance of this happening, Choptuik told the Times, would be comparable to standing a pencil upright on its sharpened tip _ improbable, yet theoretically possible.

Hawking declined to yield unequivocally _ he made another bet with the Caltech physicists that although a very limited set of conditions had been found for creating naked singularities, no general conditions would be found.

And the concessionary message Hawking had printed on T-shirts hardly conceded defeat. The shirts read: ``Nature Abhors a Naked Singularity.''

``All this has a very serious undertone,'' Preskill told the Times. ``If we are ever to understand singularities we must do so in terms of some yet-to-be-discovered theory of quantum gravity, and that would be a revolution in physics. We're not there yet.''