James H. Applegate

Tel: (212) 854-6834

 1976             B.S.,  Michigan State University (Astrophysics) 
 
 1980             Ph.D.,  SUNY at Stony Brook (Physics) 
 
 1981             Postdoc,  Neils Bohr Institute 
 
 1981 -- 1984     Bantrell Research Fellow,  California Institute of Technology 
 
 1984 -- 1988     Assistant Professor, Department of Astronomy 
 
 1992 -- 1994     Co-Director,  Columbia Astrophysics Laboratory 
 
 1992 -- 1994     Chairman,  Department of Astronomy 
 
 1989 -- present  Associate Professor,  Department of Astronomy 

Research Interests:

Stellar Physics: Supernova Explosions, Neutron Stars, Nucleosynthesis, The Physics of Interacting Binaries, Millisecond Pulsars
Cosmology: Phase Transitions, Nucleosynthesis
Dynamics: Globular Cluster, Stability of the Solar System, Special Purpose Computers
Mathematics: Application of Ito Calculus and Stochastic Differential Equations in Astrophysics

I am a theoretical physicist with broad interests in astrophysics. I have developed a model for the orbital period variations seen in the Black Widow Pulsar system PSR B1957+20 which explains the observations and provides an attractive picture for the evolution of the system from a low-mass X-ray binary to a solitary millisecond pulsar or a millisecond pulsar with a family of planets. The novel feature of the model is that the companion is powered by the dissipation of heat by tidal friction. Detailed models of the structure and evolution of tidally powered objects are under development. In my work on cosmology, I have described the consequences of a first order phase transition in quantum chromodynamics on the early evolution of the universe, and shows how this transition might be detectable through its effect on big bang nucleosynthesis. I have performed a Monte-Carlo analysis of the consequences of supernova explosions in binaries. My interest in Ito calculus and stochastic differential equations arose from my trying to explain patterns in the ratios of abundances of elements in metal-poor stars. I believe that these techniques will have many applications in astrophysics.

Selected Publications:

• ``Relics of Cosmic Quark Condensation," Phys. Rev. D31, 3037 (1985)
• ``The Outer Solar System for 200 Million Years,'' A.J. 92, 176 (1986)
• ``Dynamical Effects of Stellar Evolution in Globular Clusters," Ap.J. 301, 132 (1986)
• ``The Quark-Hadron Transition in the Early Universe," Nucl. Phys. A527, 195c (1991)
• ``A Mechanism for Orbital Period Modulation in Close Binaries," Ap.J. 385, 621 (1992)
• ``Production of Heavy Elements in Inhomogeneous Cosmologies," Ap.J. 429, 499 (1994)
• ``Orbital Period Variability in the Eclipsing Pulsar Binary PSR B1957+20: Evidence for a Tidally Powered Star," Ap.J. 429, 499 (1994)