In the article "America Must Remain the World's University" {Outlook, Nov. 15}, the writers do not deal adequately with the convergence of factors in the early 1990s that will adversely affect institutions of higher learning in the physical and mathematical sciences and in engineering. The primary facts are these: 1) The current significant decline in the number of 18-year-olds will continue until about the mid-1990s. 2) There will be a sharp rise in retirements of scientists and engineers in government, industry and universities in the early and mid-1990s .

Clearly, the number of high school graduates will decrease. Assuming that there is no change in the interest of these students in studying the physical sciences and mathematics in college -- and there is nothing to suggest otherwise -- the number of students graduating with advanced degrees in these areas will also decrease.

At the time that the decreased numbers of graduates and rising retirements converge, demand for graduates will exceed supply even with the availability of foreign nationals. The competition for the services of the best graduates will place most universities in an extremely hazardous position. First, they will be unable to offer the starting salaries of government and industry. Second, the federal budget decreases to be implemented shortly will reduce the availability of sponsored research funds on which much university research is dependent.

Today, many viable graduate programs in the physical sciences and mathematics would have to be sharply curtailed or even terminated were it not for foreign graduate students. Extrapolation to the 1990s presents a grim scenario for many institutions of higher learning. The data are real and irrefutable. America may remain the world's university, but it will do so with less prominence in the scientific disciplines. THEODORE P. PERROS Professor of Chemistry The George Washington University Washington