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George R. Blumenthal helped formulate the cold dark matter account of the formation of galaxies and larger cosmic structures. The 1984 paper with Sandra Faber, Joel Primack and Martin Rees considered matter whose early velocity dispersion was sufficiently small that free streaming would not erase fluctuations on galactic scales.

This connects a proposed microscopic property of dark matter to observable cosmic structure: surviving density fluctuations grow through gravity, and their initial spectrum constrains the later distribution of galaxies. The paper evaluated a model with calculable consequences, rather than merely adding unseen mass to individual systems.^[ref]

Joel Primack helped formulate cold dark matter as a quantitative framework for galaxy formation. The 1984 study with George R. Blumenthal, Sandra Faber and Martin Rees linked a primordial fluctuation spectrum to the formation of galaxies and galaxy clusters when collisionless particles have sufficiently small early velocity dispersion.^[ref]

Here “cold” concerns the particles' early random velocities, not whether the later galaxies are thermally cold.

Sandra Faber contributed to the cold dark matter explanation of galaxy formation. With George R. Blumenthal, Joel Primack and Martin Rees, she developed the 1984 account in which small early particle velocity dispersion preserves galaxy-scale density fluctuations against free streaming.^[ref]

The central test connects particle behaviour to astronomical structure: the surviving fluctuation spectrum determines which scales can seed galaxies and galaxy clusters.