# Greg Comer, Ph.D.

Professor

Physics

## Education

- Ph.D. in Physics from the University of North Carolina
- B.S. in Physics and Mathematics from East Tennessee State University
- Postdoc, DARC, l'Observatoire de Paris-Meudon
- Postdoc, Racah Institute of Physics, The Hebrew University
- Adjunct Associate Professor of Physics, Department of Physics, Washington University
- Faculty Advisor to the Saint Louis University Society of Physics Students (SLU SPS)
- Director of the Center for Fluids at All Scales (CFAS)
- Associate Editor, Matters of Gravity, APS Topical Group on Gravity Newsletter
- Editor, The Spacetime Emporium

## Research Interests

A key question is the role of multiple fluid dynamics on the creation and emission of gravitational waves from neutron stars. Is such dynamics detectable by, say, future versions of LIGO? If yes, then novel aspects of the supranuclear equation of state will be revealed (such as entrainment, which means the momentum of a fluid element inside a neutron star is a linear combination of the fluxes of the independent superfluid/superconducting species). To model multiple fluid dynamics in neutron stars requires input from various areas:

- General relativity and gravitation (neutron star structure, gravitational waves, etc)
- Fluid dynamics (multiple fluxes, dissipation, etc)
- Numerical methods
- Condensed matter physics (superfluidity/superconductivity, stress calculations, etc)
- Nuclear and particle physics (supranuclear equations of state, reaction rates, etc)

Basically, one needs each and every volume of Landau and Lifschitz on their shelves to pursue this kind of modeling!

## Publications and Media Placements

Refereed Papers

- N. Andersson and G. L. Comer, ``Entropy Entrainment and Dissipation in Finite Temperature Superfluids,'' submitted to Proceedings A Royal Society (2009). Available as arXiv.org e-print 0811.1660v3.
- N. Andersson and G. L. Comer, ``Variational Multi-fluid Dynamics and Causal Heat Conductivity,'' Proceedings A Royal Society, to appear (2010). Available as arXiv.org e-print 0908.1707v1.
- L. Samuelsson, C. S. Lopez-Monsalvo, N. Andersson, and G. L. Comer, ``Relativistic Two-stream Instability,'' General Relativity and Gravitation, online, pp. 1-21 (2009). \Also available as arXiv.org e-Print 0906.4002v1.
- Lap-Ming Lin, N. Andersson, and G. L. Comer, ``Oscillations of General Relativistic Multi-fluid/Multi-Layer Compact Stars,'' Physical Review D, v. 78, n.8, 083008 (2008). Also available as arXiv.org e-Print 0709.0660.
- T. Sidery, N. Andersson, and G. L. Comer, ``Waves and Instabilities in Dissipative Rotating Superfluid Neutron Stars,'' Monthly Notices of Royal Astronomical Society, v. 385, pp. 335-348 (2008). Also available as arXiv.org e-Print 0706.0672.
- N. Andersson, T. Sidery, and G. L. Comer, ``Superfluid Neutron Star Turbulence,'' Monthly Notices of Royal Astronomical Society, v. 381, pp. 747-756 (2007). Also available as arXiv.org e-Print astro-ph/0703257.
- N. Andersson and G. L. Comer, ``Relativistic Fluid Dynamics: Physics for Many Different Scales,'' Living Reviews in Relativity, v. 10, (2007). Also available as arXiv.org e-Print gr-qc/0605010.
- N. Andersson and G. L. Comer, ``A Flux Conservative Formalism for Convective and Dissipative Multi-Fluid Systems, with Application to Newtonian Superfluid Neutron Stars,'' Classical and Quantum Gravity, v. 23, pp. 5505--5529 (2006). Also available as arXiv.org e-Print physics/ 0509241.
- N. Andersson, G. L. Comer, and T. Sidery, ``Mutual Friction in Superfluid Neutron Stars,'' Monthly Notices of Royal Astronomical Society, v. 368, pp. 162--170 (2006). Also available as arXiv.org e-Print astro-ph/0510057.
- N. Andersson, G. L. Comer, and K. Glampedakis, ``How Viscous is a Superfluid Neutron Star Core,'' Nuclear Physics A, v. 763, pp. 212--229 (2005). Also available as arXiv.org e-Print astro-ph/0411748.
- R. Prix, J. Novak, and G. L. Comer, ``Relativistic Numerical Models for Stationary Superfluid Neutron Stars,'' Physical Review D, v. 71, n. 4, 043005 (2005). Also available as arXiv.org e-Print gr-qc/0410023.
- N. Andersson, G. L. Comer, and K. Grosart, ``Lagrangian Perturbation Theory of Nonrelativistic Rotating Superfluid Stars,'' Monthly Notices of Royal Astronomical Society, v. 355, pp. 918--928 (2004). Also available as arXiv.org e-Print astro-ph/0402640.
- N. Andersson, G. L. Comer, and R. Prix, ``The Superfluid Two-Stream Instability and Pulsar Glitches,'' Monthly Notices of Royal Astronomical Society, v. 354, pp. 101--110 (2004). Also available as arXiv.org e-Print astro-ph/0211151.
- G. L. Comer, ``Slowly Rotating General Relativistic Superfluid Neutron Stars with Relativistic Entrainment,'' Physical Review D, v. 69, n. 12, 123009 (2004). Also available as arXiv.org e-Print gr-qc/0402015.
- R. Prix, G. L. Comer, and N. Andersson, ``Inertial Modes of Non-stratified Superfluid Neutron Stars,'' Monthly Notices of Royal Astronomical Society, v. 348, pp. 625--637 (2004). Also available as arXiv.org e-Print astro-ph/0308507.
- G. L. Comer and R. Joynt, ``A Relativistic Mean Field Model for Entrainment in General Relativistic Superfluid Neutron Stars,'' Physical Review D, v. 68, n. 2, 023002 (2003). Also available as arXiv.org e-Print gr-qc/0212083.
- N. Andersson, G. L. Comer, and R. Prix, ``Are Pulsar Glitches Triggered by a Superfluid Two-Stream Instability?,'' Physical Review Letters, v. 90, n. 9, 091101 (2003). Also available as arXiv.org e-Print astro-ph/0210486.
- G. L. Comer, ``Do Neutron Star Gravitational Waves Carry Superfluid Imprints?,'' Foundations of Physics, v. 32, n. 12, pp. 1903--1942 (2002). Also available as arXiv.org e-Print astro-ph/0207608.
- N. Andersson, G. L. Comer, and D. Langlois, ``Oscillations of General Relativistic Superfluid Neutron Stars,'' Physical Review D, v. 66, n. 10, 104002 (2002). Also available as arXiv.org e-Print gr-qc/0203039.
- R. Prix, G. L. Comer, and N. Andersson, ``Slowly Rotating Superfluid Newtonian Neutron Star Model with Entrainment,'' Astronomy & Astrophysics, v. 381, pp. 178--196 (2002). Also available as arXiv.org e-Print astro-ph/0107176}.
- N. Andersson and G. L. Comer, ``Probing Neutron Star Superfluidity with Gravitational Wave Data,'' Physical Review Letters, v. 87, n. 24, 241101 (2001). Also available as arXiv.org e-Print gr-qc/0110112.
- N. Andersson and G. L. Comer, ``On the Dynamics of Superfluid Neutron Star Cores,'' Monthly Notices of Royal Astronomical Society, v. 328, pp. 1129--1143 (2001). Also available as arXiv.org e-Print astro-ph/0101193.
- N. Andersson and G. L. Comer, ``Slowly Rotating General Relativistic Superfluid Neutron Stars,'' Classical and Quantum Gravity, v. 18, pp. 969--1002 (2001). Also available as arXiv.org e-Print gr-qc/0009089.
- G. L. Comer, D. Langlois, and L. M. Lin, ``Quasinormal Modes of General Relativistic Superfluid Neutron Stars,'' Physical Review D, v. 60, n. 10, 104025 (1999). Also available as arXiv.org e-Print gr-qc/9908040.
- G. L. Comer and Hisa-aki Shinkai, ``Generation of Scalar-Tensor Gravity Effects in Equilibrium State Boson Stars,'' Classical and Quantum Gravity v. 15, pp. 669-688 (1998).
- G. L. Comer, ``Long Wavelength Corrections to PPN Parameters and dG/dt/G,'' Classical and Quantum Gravity, v. 14, pp. 1371-1386 (1997).
- G. L. Comer, Nathalie Deruelle, and David Langlois, ``Long Wavelength Iteration Scheme and Scalar-Tensor Gravity,'' Physical Review D, v. 55, n.6, pp. 3497--3505 (1997).
- G. L. Comer, ``3+1 Approach to the Long Wavelength Iteration Scheme,'' Classical and Quantum Gravity, v. 14, pp. 407-420 (1997).
- G. L. Comer, ``Relativistic Kinetic Theory Description of Thick Einstein Shells,'' General Relativity and Gravitation, v. 28, n. 5, pp. 601--611 (1996).
- G. L. Comer, ``Thick Einstein Shells as `Heat' Baths for Black Holes,'' Proceedings of Journées Relativistes, Special Issue of International Journal of Modern Physics D, v. 3, n. 1, pp. 171-174 (1994).
- G. L. Comer, N. Deruelle, D. Langlois, and J. Parry, ``Growth or Decay of Cosmological Inhomogeneities as a Function of their Equation of State,'' Physical Review D, v. 49, n. 6, pp. 2759--2768 (1994).
- G. L. Comer and J. Katz, ``Some Conditions for Existence of Tension Stars,'' Monthly Notices of Royal Astronomical Society, v. 267, pp. 51--58 (1994).
- G. L. Comer and David Langlois, ``Hamiltonian Formulation for Relativistic Superfluids,'' Classical and Quantum Gravity, v. 11, pp. 709--721 (1994).
- G. L. Comer and David Langlois, ``Hamiltonian Formulation for Multi-Constituent Relativistic Perfect Fluids,'' Classical and Quantum Gravity, v. 10, pp. 2317--2327 (1993).
- G. L. Comer, David Langlois and P. Peter, ``A Brief Comment on Thick Einstein Shells,'' Classical and Quantum Gravity, v. 10, L127--L131 (1993).
- G. L. Comer and J. Katz, ``Thick Einstein Shells and their Mechanical Stability,'' Classical and Quantum Gravity, v. 10, pp. 1751--1765 (1993).
- G. L. Comer, ``Ensemble Dependence of the Stability of Thermal Black Holes,'' Classical and Quantum Gravity, v. 9, pp. 947--962 (1992).
- G. L. Comer, ``Expectation Value of the Horizon Area for Thermal Equilibrium Black Holes,'' Classical and Quantum Gravity, v. 8, pp. L119--L123 (1991).
- J. D. Brown, G. L. Comer, E. A. Martinez, J. Melmed, B. F. Whiting and J. W. York, ``Thermodynamic Ensembles and Gravitation,'' Classical and Quantum Gravity, v. 7, pp. 1433--1444 (1990).
- G. L. Comer, ``The Thermodynamic Stability of Systems Containing Black Holes,'' Ph.D. Thesis, University of North Carolina at Chapel Hill, July, 1990.

Funding and Collaboration

- Funding: National Science Foundation
- Collaboration: Nils Andersson, Department of Mathematics, Southampton University, UK

Selected Presentations

- A Flux-conservative Formalism for Convective and Dissipative Multi-fluids (see Flux Conservative).
- Multi-Fluids and the Two-Stream Instability (see Two Stream Instability).
- Do Neutron Star Gravitational Waves Carry Superfluid Imprints? (see GW Superfluid Imprints).