Paul Steinhardt

Paul Joseph Steinhardt (born December 25, 1952) is an American theoretical physicist whose work focuses on understanding the universe and the nature of matter. He currently serves as the Albert Einstein Professor in Science at Princeton University, where he teaches in both the Physics and Astrophysical Sciences departments.

Steinhardt is best known for developing new ideas about how the universe began, changed over time, and might continue in the future. He also discovered a special kind of material called quasicrystals, which were once thought to only exist in laboratories. He found natural examples of these materials in old museum samples and later in meteorites from far eastern Russia.

In addition to his research, Steinhardt has written two popular books. Endless Universe: Beyond the Big Bang (2007), which he co-authored with Neil Turok, explains how scientists developed new theories about the universe that challenge the traditional Big Bang idea. His second book, The Second Kind of Impossible: The Extraordinary Quest for a New Form of Matter (2019), tells the story of how he and his student Dov Levine first imagined quasicrystals and how he later searched for them in meteorites.

Education and career

Paul Steinhardt was born in 1952 in Miami, Florida. He went to Coral Gables Senior High School and also took classes at a nearby university. He earned his Bachelor of Science in physics from the California Institute of Technology in 1974 and his Ph.D. in physics from Harvard University in 1978. After that, he worked at the Harvard Society of Fellows until 1981. He then joined the faculty at the University of Pennsylvania, where he became a professor. Since 1998, he has been a professor at Princeton University, where he also helped start the Princeton Center for Theoretical Science and led it from 2007 to 2019.

Research

Inflationary cosmology

Beginning in the early 1980s, Paul Steinhardt co-authored important papers that helped establish the foundations of inflationary cosmology. In 1982, Steinhardt and Andreas Albrecht, along with Andrei Linde, developed the first inflationary models that could speed up the expansion of the universe to explain its observed smoothness and flatness. These models included a "slow-roll" effect, which helped sustain inflation long enough to match what we see today.

Steinhardt also contributed to understanding how quantum fluctuations during inflation could create the seeds for galaxies. Later, he explored the idea of eternal inflation, which suggests that inflation could continue forever, leading to a multiverse — many different universes with different properties. However, Steinhardt expressed concerns that this idea makes it hard to predict anything specific about our universe.

Bouncing and cyclic cosmology

Because of issues with inflationary theory, Steinhardt developed new models that replace the big bang with a "bounce." In these models, the universe transitions smoothly from a period of slow contraction to expansion, avoiding problems like the multiverse. These bouncing models suggest a cyclic universe, where periods of expansion and contraction repeat over time.

Dark energy and dark matter

Steinhardt has also researched dark energy and dark matter. In the 1990s, he showed that there must be dark energy causing the universe's expansion to accelerate. He introduced the idea of quintessence, a form of dark energy that changes over time, as an alternative to the constant cosmological constant. He also worked on models of self-interacting dark matter to explain certain observations that standard models cannot.

Quasicrystals

In 1983, Steinhardt and Dov Levine introduced the theory of quasicrystals — a new type of solid with a unique atomic structure that was previously thought to be impossible. Their theory was proven when Dan Shechtman discovered a real quasicrystal in 1984. Steinhardt's team later found natural quasicrystals in meteorites and even in materials from the first atomic bomb test.

Photonics and hyperuniformity

Steinhardt's work expanded into creating new materials with special light properties. He helped design photonic quasicrystals that can control light in specific ways and discovered hyperuniform disordered solids, which can act like semiconductors for light. These materials have many potential uses, from communications to energy harvesting.

Amorphous solids

Steinhardt also studied disordered solids like glasses and amorphous metals. He created early computer models of these materials and explored their structural and electronic properties, contributing to our understanding of how atoms arrange themselves in these substances.

Honors and awards

Paul Steinhardt has received many awards for his important work in science. In 1986, he became a Fellow of the American Physical Society. In 1998, he received the P.A.M. Dirac Medal together with Alan Guth and Andrei Linde for their work on theories about the universe. In 2010, he was given the Oliver E. Buckley Condensed Matter Prize for his studies of special crystal shapes called quasicrystals. Later honors include the John Scott Award in 2012 and the Niels Bohr Institute Medal of Honour in 2020.