Relationship between Population Dynamics and the Self-Energy in Driven Non-Equilibrium Systems

We compare the decay rates of excited populations directly calculated within a Keldysh formalism to the equation of motion of the population itself for a Hubbard-Holstein model in two dimensions. While it is true that these two approaches must give the same answer, it is common to make a number of simplifying assumptions within the differential equation for the populations that allows one to interpret the decay in terms of hot electrons interacting with a phonon bath. Here we show how care must be taken to ensure an accurate treatment of the equation of motion for the populations due to the fact that there are identities that require cancellations of terms that naively look like they contribute to the decay rates. In particular, the average time dependence of the Green's functions and self-energies plays a pivotal role in determining these decay rates.Comment: Submitted to Entrop

Rocket Combustion Properties for Coaxial Injectors Operated at Elevated Pressures

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76596/1/AIAA-2006-4704-966.pd

Mixing Lengths of Reacting and Nonreacting Coaxial Injectors in a Laboratory Rocket Combustor

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77156/1/AIAA-2008-5022-346.pd

Mixing Lengths of Coaxial Jets in a Rocket Combustor Configuration Using Acetone PLIF

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77322/1/AIAA-2007-5590-512.pd

Interstellar low-energy anti-protons as a probe of dark matter and primordial black holes

Cosmic ray antiprotons can originate from dark matter annihilating into quarks that subsequently decay into antiprotons. Evaporation of primordial black holes also can produce a significant antiproton flux. Since the spectrum of secondary antiprotons from cosmic ray interactions peaks at ~ 2 GeV and goes down sharply at lower energy, there is a window at energies < 1 GeV in which to look for excess antiprotons as a signature of these exotic antiproton sources. However, in the vicinity of the Earth low energy particles are strongly modulated by the solar wind, which makes any analysis ambiguous. The adverse effects of the solar wind can be avoided by placing a low energy antiproton spectrometer aboard an interstellar probe. The theoretical predictions are reviewed and the preliminary design of a light-weight, low-power instrument to make the measurements and a summary of the anticipated results are given in this paper

Determination of the critical current density in the d-wave superconductor YBCO under applied magnetic fields by nodal tunneling

We have studied nodal tunneling into YBa2Cu3O7-x (YBCO) films under magnetic fields. The films' orientation was such that the CuO2 planes were perpendicular to the surface with the a and b axis at 450 form the normal. The magnetic field was applied parallel to the surface and perpendicular to the CuO2 planes. The Zero Bias Conductance Peak (ZBCP) characteristic of nodal tunneling splits under the effect of surface currents produced by the applied fields. Measuring this splitting under different field conditions, zero field cooled and field cooled, reveals that these currents have different origins. By comparing the field cooled ZBCP splitting to that taken in decreasing fields we deduce a value of the Bean critical current superfluid velocity, and calculate a Bean critical current density of up to 3*10^7 A/cm2 at low temperatures. This tunneling method for the determination of critical currents under magnetic fields has serious advantages over the conventional one, as it avoids having to make high current contacts to the sample.Comment: 8 pages, 2 figure