ALAN H. GUTH, Victor F. Weisskopf
Professor of Physics
Research Interests
Most of Professor Guth's research has centered on the application
of theoretical particle physics to the early universe: what can
particle physics tell us about the history of the universe, and
what can cosmology tell us about the fundamental laws of nature?
In 1981 he proposed that many features of our universe, including
how it came to be so uniform and why it began so close to the critical
density, can be explained by a new cosmological model which he called
inflation. Inflation is a modification
of the conventional big bang theory, proposing that the expansion
of the universe was propelled by a repulsive gravitational force
generated by an exotic form of matter. Although Guth's initial proposal
was flawed (as he pointed out in his original paper), the flaw was
soon overcome by the invention of "new inflation," by
Andrei Linde in
the Soviet Union and independently by Andreas
Albrecht and Paul
Steinhardt in the US. After more than 20 years of development
and scrutiny the evidence for the inflationary universe model now
looks better than ever.
One of the intriguing consequences of inflation is that quantum
fluctuations in the early universe can be stretched to astronomical
proportions, providing the seeds for the large scale structure of
the universe. The predicted spectrum of these fluctuations was calculated
by Guth and others in 1982. These fluctuations can be seen today
as ripples in the cosmic background radiation, but the amplitude
of these faint ripples is only about one part in 100,000. Nonetheless,
these ripples were detected by the COBE satellite in 1992, and they
have now been measured to much higher precision by the WMAP
satellite and other experiments. The properties of the radiation
are found to be in excellent agreement with the predictions of the
simplest models of inflation [image].
Working with Prof. Edward Farhi
and others, Guth has explored the question of whether it is in principle
possible to ignite inflation in a hypothetical laboratory, thereby
creating a new universe. The answer is a definite maybe. They showed
that it cannot be done classically, but with quantum tunneling it
might be theoretically possible. The new universe, if it can be
created, would not endanger our own universe. Instead it would slip
through a wormhole and rapidly disconnect completely.
Another intriguing feature of inflation is that almost all versions
of inflation are eternal—once inflation starts, it never stops
completely. Inflation has ended in our part of the universe, but
very far away one expects that inflation is continuing, and will
continue forever. Is it possible, then, that inflation is also eternal
into the past? Recently Guth has worked with Alex
Vilenkin (Tufts) and Arvind
Borde (Southampton College) to show that the inflating region
of spacetime must have a past boundary, and that some new physics,
perhaps a quantum theory of creation, would be needed to understand
it.
Much of Guth's current work also concerns the study of density
fluctuations arising from inflation: What are the implications of
novel forms of inflation? Can the underlying theory be made more
rigorous? Guth is also interested in pursuing the possibility of
inflation in "brane world" models, which propose that
our universe is a 3+1–dimensional membrane floating in a higher
dimensional space.
Guth's earlier work has included the study of lattice gauge theory,
magnetic monopoles and instantons, Gott time machines, and a number
of other topics in theoretical physics.
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Biographical Sketch
Professor Alan Guth was born in New Brunswick, New Jersey, in 1947.
He grew up and attended the public schools in Highland Park, NJ,
but skipped his senior year of high school to begin studies at the
Massachusetts Institute of Technology. He remained at MIT from 1964
to 1971, acquiring S.B., S.M., and Ph.D. degrees, all in physics.
His Ph.D. thesis, done under the supervision of Francis
Low, was an exploration of an early model of how quarks combine
to form the elementary particles that we observe.
During the next nine years, Guth held postdoctoral positions at
Princeton University, Columbia University, Cornell University, and
the Stanford Linear Accelerator Center (SLAC), working mostly on
rather abstract mathematical problems in the theory of elementary
particles. While at Cornell, however, Guth was approached by a fellow
postdoctoral physicist, Henry
Tye, who persuaded Guth to join him in studying the production
of magnetic monopoles in the early universe. This work changed the
direction of Guth's career. The following year at SLAC he continued
to work with Tye on magnetic monopoles. They found that standard
assumptions in particle physics and cosmology would lead to a fantastic
overproduction of magnetic monopoles, a conclusion that was reached
slightly earlier by John
Preskill, then at Harvard (now at Caltech). Guth and Tye began
a search for alternatives that might avoid the magnetic monopole
overproduction problem, and from this work Guth invented a modification
of the big bang theory called the inflationary
universe.
The following September (1980), Guth returned to MIT as an associate
professor. Guth has since been elected to the National Academy of
Sciences and the American Academy of Arts and Sciences, and has
been awarded the MIT School of Science Prize for Undergraduate Teaching
(1999), the Franklin Medal for Physics of the Franklin Institute
(2001), and the Dirac Prize of the International Center for Theoretical
Physics in Trieste (2002). He is now the Victor F. Weisskopf Professor
of Physics and a Margaret MacVicar Faculty Fellow at MIT.
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Selected Publications
Professor Guth's publications can be found online at SPIRES.
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