The Physics department colloquia are usually on Friday afternoons at 3 pm in Room 135. Coffee and cookies are served at 2:45 pm in the same room. Anyone is welcome.

The Creation of Bosons, Fermions, Gravitational Perturbations and Waves in the Expanding Universe
Dr. Leonard Parker, Distinguished Professor Emeritus, UW-Milwaukee, Dept. of Physics
Physics – Room 481

Quantum field theory predicts that particles, perturbations and gravitational waves may be created from the vacuum in an expanding universe. The quantum field theory basis for this particle creation from vacuum was first shown and thoroughly studied in my Ph.D. Thesis (Harvard University, 1966) and my related papers (Phys. Rev. Lett,, 1968, and Phys. Rev. 1969 and 1971). I go over the physical basis for these processes that follow from quantum field theory and general relativity. The effect of the creation of perturbations and particles is observed today in the small temperature anisotropies of the isotropic CMB radiation. Furthermore, part of the recently observed B-wave polarization pattern of the CMB radiation may result from the creation of gravitational wave perturbations by the early expanding universe.

Finally, I discuss the quantum field theory basis for the vacuum state of the exponentially expanding inflationary universe. I show how the inflationary vacuum state may arise by dynamical evolution from an initial Minkowski vacuum state in a flat space-time that spontaneously fluctuates to form some subregions undergoing inflationary exponential expansion.