The Structure, Stability, & Dynamics of Self-Gravitating Fluids

This website is primarily intended to serve as an entry point to a MediaWiki environment that contains a detailed, technical discussion of the The Structure, Stability, & Dynamics of Self-Gravitating Fluids.

Much of astrophysics community's present understanding of the structure, stability, and dynamical evolution of individual stars, short-period binary star systems, and the gaseous disks that are associated with numerous types of stellar systems (including galaxies) is derived from an examination of the behavior of a specific set of coupled, partial differential equations. These equations — most of which also are heavily utilized in studies of continuum flows in terrestrial environments — are thought to govern the underlying physics of all macroscopic "fluid" systems in astronomy. Although relatively simple in form, they prove to be very rich in nature.

The literature on this subject is enormous, as serious discussions of the structure and dynamical properties of stars and galaxies date back more than a century. Although a reasonable attempt is made here to review this vast literature and to provide a bridge between discussions that traditionally have focused on stellar structure and those that have focused on galaxy disks, the primary purpose of this work is two-fold:

We have adopted MediaWiki as the hosting environment of choice, most signficantly, because — after incorporating the proper set of extensions — it facilitates the insertion of complex, LaTeX-formulated mathematical expressions into the text.

About the Author: A Fellow of the AAAS, Tohline has authored one hundred articles in scientific journals and proceedings, primarily on problems related to complex fluid flows in astrophysical settings. His expertise in utilizing high-performance computers to accurately simulate the processes by which stars form and to simulate catastrophic events that will give rise to bursts of gravitational radiation is recognized worldwide. Fifteen students — see also — have completed their doctoral dissertation research under his direction (an additional four under his co-direction) and, over the years, he has been a lead investigator on federal and state research or research-infrastructure grants totaling more than ten million dollars.

Tohline earned a B.S. in Physics from Centenary College of Louisiana in 1974 and a Ph.D. in Astronomy from the University of California, Santa Cruz in 1978. Before joining the Louisiana State University (LSU) faculty in 1982, Tohline held a J. Willard Gibbs instructorship in the Astronomy Department at Yale University and a postdoctoral fellowship at Los Alamos National Laboratory. He has served as a member of the Advisory Council for the Directorate of Mathematical & Physical Sciences of the U.S. National Science Foundation (NSF), as Chair of the Committee of Visitors for the NSF Astronomy Division, as co-editor of the Visualization Corner for Computing in Science & Engineering (a magazine published jointly by the American Institute of Physics and the IEEE Computer Society), as a member of the Applications Strategy Council of Internet2, on the Program Advisory Council of LIGO, as Chairman of LSU's Department of Physics & Astronomy, and as Director of LSU's Center for Computation & Technology (CCT).

Retired from LSU at the end of the 2013 calendar year, Tohline retains the titles of Director Emeritus of LSU's Center for Computation & Technology as well as Professor Emeritus in LSU's Department of Physics & Astronomy. In retirement he remains active in research.

OCTO-TIGER: a new, 3D hydrodynamic code for stellar mergers that uses HPX parallelization
This publication by D. C. Marcello et al. (2021, MNRAS, 504, Issue 4, pp.5345-5382) — see brief summary — illustrates that, following his retirement, Tohline's LSU colleagues (two, former doctoral students) have carried this tradition forward in exciting ways.

In an effort to show the considerable overlap that exists between the discussions presented across our accompanying MediaWiki site and the discussions that have appeared previously in the traditional print medium, we have constructed an appendix containing a set of key physical equations and, next to each equation, we have identified where this equation is introduced or discussed in each of seven published texts. The texts that we have selected are:

The key equations that we have chosen to highlight are drawn from a wide assortment of sub-fields of physics that feed into and, indeed, are essential to our modern understanding of astrophysical systems, including: classical mechanics, fluid dynamics, thermodynamics & statistical mechanics, quantum mechanics, radiation transport, and relativity. Each time one of these equations appears in our discussion, it will be marked as a key equation so that, from the information contained in our key equations appendix, the reader can be guided to parallel discussions of related concepts as they have been presented in the above-identified, published texts.

Note that virtually all of these key equations — and discussions of the physical concepts that underpin them — can also now be found in the pages of Wikipedia or other online references. Where appropriate, links to these online discussions are also provided in the text of our MediaWiki chapters so that readers can take advantage of this growing information resource.