Stanford physics Professor Andrei Linde, whose theories on the origin of the universe have revolutionized the field of cosmology, has been named co-recipient of the 2002 Dirac Medal by the Abdus Salam International Center for Theoretical Physics (ICTP) in Trieste, Italy. Linde will share the prize with physicists Alan Guth of the Massachusetts Institute of Technology and Paul Steinhardt of Princeton University. In announcing the award, ICTP officials credited the three scientists with developing the concept of ''inflationary cosmology'' - the idea that the universe began not with a fiery big bang but with an extraordinarily rapid expansion (inflation) of space in a vacuum-like state. ''Although the history of the very early universe has not been firmly established, the idea of inflation has already had notable observational successes, and it has become the paradigm for fundamental studies in cosmology,'' ICTP officials said. Inflationary cosmos Linde helped lay the foundation for inflationary cosmology in the 1980s while working at the Lebedev Physical Institute in his native Russia. According to inflation theory, the universe started out smaller than a proton, then - in less than a billionth of a billionth of a billionth of a second - expanded to a size trillions of times bigger than our observable universe. ''If somebody had told me that 25 years ago, I would have thought he was crazy,'' Linde quipped, ''but that's what we're getting this medal for. It represents the acceptance of our theory by the general community.'' According to ICTP, ''Difficulties with the original inflationary model were recognized by Guth and others, and were overcome with the introduction of 'new' inflation by Linde and Steinhardt. Linde went on to propose other promising versions of inflationary theory, such as chaotic inflation.'' In 1986, four years before joining the Stanford faculty, Linde published the theory of a self-reproducing inflationary universe - the idea that ours is but one of many inflationary universes that sprout from an eternal cosmic tree. Paul Dirac Founded in 1964 by Nobel laureate Abdus Salam, the ICTP is dedicated to fostering the growth of advanced studies and research in the developing countries. The center operates under the aegis of two United Nations agencies - the U.N. Educational, Scientific and Cultural Organization (UNESCO) and the International Atomic Energy Agency (IAEA). Major funding for ICTP is provided by the Italian government. The ICTP awards the Dirac Medal annually to individuals who have made significant contributions to theoretical physics and mathematics. The award is given in honor of English physicist Paul Dirac, recipient of the 1933 Nobel Prize. Winners are announced on Aug. 8, Dirac's birthday. The first medal was presented in 1985 - a year after his death. Helen Quinn, a theoretical physicist at the Stanford Linear Accelerator Center, received a medal in 2000. Linde and the other two recipients will receive medals and deliver a lecture in Trieste next spring or summer. A $5,000 prize will be shared by the three recipients.