Leonard Parker

Distinguished Professor Emeritus

: (414) 229-6437
Office: 422

Research Interests: Quantum Field Theory, Cosmology, Gravitation, Particle Physics, Astrophysics



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Leonard Parker


Professor Leonard Parker was first to show that quantum field theory implies particle creation in curved spacetimes. This process creates particles and amplifies small perturbations in an expanding universe. The observed features of the cosmic microwave background (CMB) radiation and of the large-scale structure of the present universe confirm that this particle creation process in an in inflationary universe was responsible for the CMB temperature anisotropies and for the clumping of matter that gave rise to galaxies and galactic clusters. 

Parker was first (with S. A. Fulling) to develop the method of adiabatic regularization in curved spacetime. He was also first to calculate the perturbations of the spectra of one-electron atoms in arbitrary gravitational fields in terms of the Riemann tensor.


Biographical Sketch

Leonard Parker received his Ph.D. in Physics from Harvard in 1967. He has been at UWM since 1968, first as Assistant professor, then as Associate Professor from 1970 until 1975 and as full professor from 1975 on. Professor Parker was also a member of the Institute for Advanced Study (Princeton) for periods during 1973-1977 and a visiting fellow at Princeton University from 1971 to 1972. He became an Emeritus Distinguished Professor in 2008.

Professor Parker has been the recipient of several prestigious awards and honors. The most recent, awarded in May 2011, is the First Award in the Gravity Essay competition from the Gravity Research Foundation (GRF). He was awarded the GRF Second Prize in 1984. Parker was elected Fellow of the American Physical Society by the Division of Particles and Fields in 1984. In 1995, he helped found the APS Topical Group in Gravitation and served on its first Executive Committee. He was named UWM Distinguished Professor in 2004. As another indicator of excellence, Parker's research has been continuously supported by National Science Foundation Grants from 1969 on.

Parker is a founding member and former director of the UWM Center For Gravitation And Cosmology. He has also been an Editorial Board Member of several journals, including the Journal of Mathematical Physics, the International Journal of Modern Physics A, Reports in Astrophysics and Cosmology and Modern Physics Letters A.

Selected publications


  • L. Parker
    "Quantized Fields and Particle Creation in Expanding Universes"
    Physical Review 183, 1057 (1969)
  • L. Parker and S. A. Fulling
    "Adiabatic Regularization of the Energy-Momentum Tensor of a Quantized Field in Homogeneous Spaces"
    Physical Review D9, 341 (1974)
  • L. Parker
    "Probability Distribution of Particles Created by a Black Hole"
    Physical Review D12, 1519 (1975)
  • L. Parker
    "Thermal Radiation Produced by the Expansion of the Universe"
    Nature 261, 20 (1976)
  • T. S. Bunch and L. Parker
    "The Feynman Propagator in Curved Spacetime: A Momentum Space Representation"
    Physical Review D20, 2499 (1979)
  • L. Parker
    "The One-Electron Atom as a Probe of Spacetime Curvature"
    Physical Review D22, 1922 (1980)
  • J. D. Bekenstein and L. Parker
    "Path Integral Evaluation of Feynman Propagator in Curved Spacetime"
    Physical Review D23, 2850 (1981)
  • J. L. Friedman, J. R. Ipser, and L. Parker
    "Rapidly Rotating Neutron Star Models"
    Astrophysical Journal 304, 115-139 (1986)
  • M. M. Glenz, and L. Parker
    "Study of the Spectrum of Inflaton Perturbations"
    Phys. Rev. D 80, 063534 (2009), 21 pages
  • I. Agullo, J. Navarro-Salas, Gonzalo J. Olmo, Leonard Parker
    "Revising the observable consequences of slow-roll inflation"
    Phys. Rev. D 81, 043514 (2010), 24 pages
  • I. Agullo, J. Navarro-Salas, Gonzalo J. Olmo, Leonard Parker
    "Hawking radiation by Kerr black holes and conformal symmetry"
    Phys. Rev. Lett. 105, 211305 (2010), 4 pages
  • I. Agullo and Leonard Parker
    "Non-Gaussianities and the stimulated creation of quanta in the inflationary universe"
    Phys. Rev. D 83, 063526 (2011), 25 pages
  • I. Agullo and Leonard Parker
    "Stimulated creation of quanta during inflation and the observable universe"
    Written for the Gravity Research Foundation 2011 Awards for Essays on Gravitation.
    This 9 page essay won the prestigious rst prize in this annual competition.

Books and Books Chapters

  • L. Parker and D. J. Toms
    "Quantum Field Theory in Curved Space-time: Quantized Fields and Gravity"
    Cambridge University Press, 2009, 500 pages; ISBN 9780521877879
  • L. Parker
    "Aspects of Quantum Field Theory in Curved Space-time: Effective Action and Energy-Momentum Tensor"
    In Recent Developments in Gravitation, edited by S. Deser and M. Levy
    Plenum Publishing Corp., New York, 1979), pp. 219-273