MIT Reports to the President 1998-99

DEPARTMENT OF PHYSICS

The mission of the Physics Department is to gain a fundamental quantitative understanding of nature, and to teach the analytic approach required for that understanding both to students pursuing careers in physics and to those entering other fields. The Department is one of the best in the world, with strengths in an extraordinarily broad range of research. A few highlights of research advances during the past year are given below. In the past year the Department has continued the process of renewal, as the large number of faculty hired in the Sputnik era has begun to retire. Four assistant professors have joined the Department during this academic year, and two more will join the faculty in the next year. In addition, the department has made a joint appointment to a junior faculty member in the Department of Brain and Cognitive Science. Paraskevas Sphicas will maintain a joint appointment as Professor of Physics at MIT and Senior Physicist at the European Laboratory for Particle Physics (CERN).

Physics faculty members continue to receive recognition by the outside community. Some of this year's major award recipients are the following: Professor Jerome Friedman was elected President of the American Physical Society. Professor Hale Bradt was awarded the 1999 Rossi Prize from the High Energy Division of the American Astronomical Society. Professor Bernard Burke was the 1998 National Radio Astronomy Observatory Karl C. Jansky Lecturer. Professor Wit Busza was elected to the Polish Academic of Arts & Sciences. Professor Mildred Dresselhaus received an honorary degree from the Sorbonne University, Paris, and was inducted into the Women in Science and Technology International Hall of Fame. Professor Lee Grodzins received an honorary degree from Purdue University. Professor Erich Ippen is the President Elect of the Optical Society of America. Professor Roman Jackiw received the 1998 Dirac Medal and was elected to the National Academy of Sciences. Professor Victoria Kaspi received the Annie Jump Cannon prize from the American Association of University Women. Professor Wolfgang Ketterle was elected to the American Academy of Arts and Sciences and received the 1999 London Prize. Professor David Pritchard was elected to the National Academy of Sciences, and was elected both as a member and as Vice-Chair of the International Union of Pure and Applied Physics Commission C15. Dr. Edwin Taylor received the 1998 Oersted Medal from the American Association of Physics for his contributions to teaching. An Alfred P. Sloan Foundation award was given Professor Amihay Hanany.

Members of the Department provide leadership both at MIT and in the Federal Government. Professor Robert Birgeneau serves as Dean of Science, and Professor J. David Litster is Vice President and Dean for Research and Dean of the Graduate School. Last year Professor Ernest J. Moniz was confirmed as Undersecretary of the Department of Energy.

Lisa Randall and Richard Milner were promoted to full Professor this year. Raymond Ashoori was promoted to Associate Professor with tenure, and Uwe-Jens Wiese and Tomás Arias were promoted to Associate Professor without tenure.

In past years only two faculty members, an undergraduate officer and a graduate officer, have supervised all the educational activities of the Department. In an effort to better serve our students, in 1998 we reorganized our educational administration under the supervision of Professor Thomas Greytak, Associate Head for Education. Tasks are divided among 11 faculty members, who also comprise the Physics Education Committee.

The size of the Department has decreased from a peak of over 100 in the late 1960s to 81 this year and 79 next year. This reduction in teaching faculty has required significant changes. First, the teaching responsibilities of each faculty member have increased. Second, graduate students now teach more freshman recitation sections. The graduate students have been enthusiastic about this opportunity to gain classroom teaching experience. In addition, a program of required tutoring has been introduced in 8.01 and 8.02. Graduate student tutors meet with no more than three freshmen at a time. In the fall of 1998, the Department initiated a training program for graduate students to prepare them for these important responsibilities. An experimental 8.01 format, which ran for four years, required many more teachers than the conventional format. The students were not enthusiastic about the new format. Consequently the traditional format of 8.01 was restored in the fall of 1998.

To encourage students to minor in Physics, the Physics Education Committee, with the consent of the entire Department, has liberalized the requirements for a minor. Whereas the previous curriculum was very specific, students will now be allowed to fulfill the physics minor requirements with any five physics courses beyond the freshman offerings.

MIT's Center for Advanced Educational Services (CAES) and Professor Walter Lewin have received a $735,000 gift from an anonymous donor to create a video tutoring web site for students taking 8.01. The gift requires matching funds of about $250,000, thereby making nearly $1,000,000 available for this two year project in which Professor Lewin will create a video archive of answers to frequently asked questions. The web-based learning environment, referred to as PIVOT, will simulate a private question and answer session that a student might have with Professor Lewin during his office hours. At each step in the process, the student may select from a menu of currently available answered questions or submit a free-form question. Once the 8.01 web-based system is completed and tested on the MIT campus, CAES plans to offer it to other learners as well (possibly with a tuition fee), including high school physics students and physics students at other universities. The system is not meant to replace traditional physics teaching and learning, but rather to supplement them. The PIVOT program will be tested in 8.01 in the fall of 1999 with Professor Lewin as the course lecturer. In a related initiative, Professor John Belcher is developing web-based animation, simulation, and visualization to enhance the teaching of 8.02. The latter effort is made possible by a gift from James A. Earl and the Helena Foundation and the National Science Foundation.

Our undergraduate majors are among the best in the United States. As an example, Anna Lopatnikova won the Apker Award of the American Physical Society for research done under the supervision of Professor Nihat Berker. This is the second student of Berker's to win the Apker. In addition, MIT's team won first place in the 1999 Boston Area Undergraduate Physics Competition where MIT's Mihai Ibanescu was the top scoring individual for the second year in a row.

Most physics research is done through participation of our faculty in labs and centers. The research of the Physics Department faculty is specifically addressed in the following lab and center reports: Laboratory for Nuclear Science, including the Bates Linear Accelerator Center and the Center for Theoretical Physics; the Center for Materials Science and Engineering; the Research Laboratory of Electronics; the Center for Space Research; the Plasma Fusion Center; the Harrison Spectroscopy Laboratory; and the Haystack Observatory. Rather than an overview, we discuss here a few highlights to give a sense of the excitement of research in the Department.

Named after pioneering MIT astrophysicist Bruno Rossi, NASA's Rossi X-ray Timing Explorer (RXTE) was launched in December 1995. An MIT group under the leadership of Professor Hale Bradt built and maintains the satellite's data system and one of its three instruments, the All Sky Monitor (ASM). The ASM has exceeded the hopes and expectations even of its designers in terms of scientific return.

Many of the objects RXTE was designed to study are X-ray transients. The ASM was built to monitor known sources (primarily neutron stars and black holes) and to trigger observing programs when these objects enter interesting phases. Roughly one third of all RXTE observations, including many of its most important, have been scheduled in response to ASM monitoring. The ASM also detects emission from previously unknown sources. An unexpected windfall from the ASM has come with its localization of gamma ray bursts.

Gamma ray bursts baffled astrophysicists for some thirty years following their discovery in the late 1960s. The lack of directionality of gamma ray detectors made it impossible to follow up the time dependence of emission at other wavelengths. In 1997, a rapidly fading X-ray afterglow from a gamma ray burst was seen by an Italian satellite, permitting its localization and follow-up. The ASM team quickly put together a system that has since led to the localization of a dozen bursts. In some cases, optical counterparts have been found that indicate that the bursts are at the edge of the visible universe. In other cases, despite searches, no optical or radio counterpart has been found, indicating a wide range in burst properties. The mechanism for these extremely energetic gamma ray bursts remains controversial. ASM will continue to make major contributions to the localization of gamma ray bursts until the launch of MIT's High Energy Transient Explorer in 2000.

Assistant Professor Deepto Chakrabarty has used RXTE to identify what appears to be a missing link between classes of pulsars. "Classical" radio pulsars are young neutron stars that spin as rapidly as 50 times per second. These slow down relatively quickly, in less time than it takes the Sun to complete one orbit of the Milky Way.

X-ray satellites detect pulses from much older neutron stars. These stars typically rotate once every few seconds, but emit pulses only when they are in binary systems and accreting mass from their companions. The very oldest known neutron stars pulse again at radio frequencies, spinning several hundred times per second. It is thought that these "millisecond" pulsars are spun up by accretion from a companion star, but a rapidly pulsing accreting star has not heretofore been seen. A second mystery is that many millisecond pulsars do not have the binary companions needed to spin them up. Chakrabarty was among those who recognized that a source chanced upon by RXTE was a neutron star spinning 400 times per second, thus linking X-ray and millisecond pulsars. Moreover, he found that the pulsar has a binary companion, and that intense X-ray radiation from the pulsar is evaporating the companion, destroying the evidence of its having been spun up. Chakrabarty suggests that this system is unusual not so much in that it is spinning rapidly, but in that its orientation to the line of sight accidentally permits us to see its pulsating X-rays. Similar but unfavorably oriented systems may appear as unpulsed X-ray sources.

The atomic physics group has a long tradition in the trapping of neutral atoms, and in the past several years, the MIT group under Wolfgang Ketterle has occupied a leadership position in the study of Bose-Einstein condensation (BEC) of atoms. One example of this group's recent achievements is the confinement of BEC atoms optically. Until recently, BEC was observed only in magnetic traps. The spins on the atoms are then necessarily aligned with the magnetic field. Last year, Ketterle managed to confine the atoms optically with laser radiation. This opens up the possibility of studying spin dependent phenomena in the BEC state, a potentially whole new area of investigation.

Another exciting recent development is the observation by Daniel Kleppner and Thomas Greytak of BEC in spin aligned hydrogen, the culmination of 20 years of intensive effort. The high density and low mass of this new collective state should yield an interesting contrast to the BEC of heavier atoms achieved previously. With this discovery, MIT has become the clear leader in the race to create and study this novel new state of matter.

More information about this department can be found on the World Wide Web at the following URL: http://web.mit.edu/physics/www/.

Marc Kastner

MIT Reports to the President 1998-99