The Degree of Fine-Tuning in our Universe -- and Possibly Others

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Date/Time:Monday, 21 Oct 2019 from 4:10 pm to 5:00 pm
Location:Phys 0005
Contact:
Phone:515-294-5441
Channel:Colloquium
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Dr. Fred C. Adams, University of Michigan

Abstract: The fundamental constants of nature must fall within a range of values in order for the universe to develop structure and ultimately support life. This talk considers the current constraints on these quantities and assesses the degree of fine-tuning required for the universe to be viable. The first step is to determine what parameters are allowed to vary. In the realm of particle physics, we must specify the strengths of the fundamental forces and the particle masses. The relevant cosmological parameters include the density of the universe, the cosmological constant, the abundance of ordinary matter, the dark matter contribution, and the amplitude of primordial density fluctuations. These quantities ae constrained by the requirements that the universe lives for a sufficiently long time, emerges from its early epochs with an acceptable chemical composition, and can successfully produce galaxies. On smaller scales, stars and planets must be able to form and function. The stars must have sufficiently long lifetimes and hot surface temperatures. The planets must be large enough to maintain atmospheres, small enough to remain non-degenerate, and contain enough particles to support a biosphere. We also consider specific fine-tuning issues in stars, including the triple alpha reaction that produces carbon, the case of unstable deuterium, and the possibility of stable diprotons. For all of these issues, the goal of this enterprise is to delineate the range of parameter space for which universes can remain habitable.

Bio: Born in Redwood City, California, Fred Adams received his undergraduate training in Mathematics and Physics from Iowa State University in 1983 and his PhD in Physics from the University of California, Berkeley, in 1988. After a postdoctoral fellowship at the Harvard-Smithsonian Center for Astrophysics, he joined the Physics Faculty at the University of Michigan in 1991. He was promoted to Full Professor in 2001, elected to the Michigan Society of Fellows in 2007, and named as the Ta-you Wu Collegiate Professor of Physics in 2014. He has received the Robert J. Trumpler Award from the ASP, the NSF Young Investigator Award, the Helen B. Warner Prize from the AAS, and is a Fellow of the American Physical Society. Professor Adams works in theoretical astrophysics with a focus on the study of star formation and cosmology. He is internationally recognized for his work on the radiative signature of the star formation process, the dynamics of circumstellar disks, the development of a theory for the initial mass function, and studies of extra-solar planetary systems. In cosmology, he has studied the inflationary universe, cosmological phase transitions, magnetic monopoles, and cosmic background radiation fields. His work in cosmology also includes explorations of the long term fate and evolution of the universe, as well as fine-tuning issues.