[Paper Review] An outline of radiatively-driven cosmology

Robert L. Kurucz|arXiv (Cornell University)|Mar 24, 2000

Cosmology and Gravitation Theories3 citations

TL;DR

This paper proposes that radiative forces—specifically radiation pressure from massive Population III stars—drastically shaped early cosmic evolution, triggering radiatively-driven implosions that formed globular clusters, galaxies, and voids during the first billion years after recombination. The key contribution is a radiation-dominated paradigm where radiation, not gravity alone, initiated violent, rapid structural formation, with gravity taking over only after radiation sources exhausted their energy.

ABSTRACT

A Big Bang universe consisting, before recombination, of H, D, 3He, 4He, 6Li, and 7Li ions, electrons, photons, and massless neutrinos, at closure density, with a galaxy-size perturbation spectrum but no large-scale structure, will evolve into the universe as we now observe it. Evolution during the first billion years is controlled by radiation. Globular clusters are formed by radiatively-driven implosions, galaxies are formed by radiatively triggered gravitational collapse of systems of globular clusters, and voids are formed by radiatively-driven expansion. After this period the strong radiation sources are exhausted and the universe has expanded to the point where further evolution is determined by gravity and universal expansion.

Motivation & Objective

• To challenge the conventional gradualist cosmology that attributes cosmic structure solely to gravity and slow evolution.
• To propose that radiation pressure from massive Population III stars was the dominant force in shaping early universe structure during the first billion years.
• To explain the formation of globular clusters, elliptical galaxies, and cosmic voids through radiatively-triggered gravitational collapse and expansion.
• To re-evaluate the origin of the intergalactic medium and the microwave background, suggesting they are not primordial but formed later via stellar processing.
• To reconcile observed abundances of light elements (Li, D, 3He) with theoretical predictions by adjusting primordial abundances and accounting for stellar processing.

Proposed method

• Model a flat Big Bang universe with H, D, 3He, 4He, 6Li, 7Li ions, electrons, photons, and massless neutrinos at closure density.
• Simulate evolution from recombination (~10,000 K) using radiative acceleration and gravitational forces in non-symmetric, galaxy-sized perturbations.
• Apply the condition g_eff = g + g_rad = 0 to define surfaces and volumes of perturbations, where effective gravity determines collapse or expansion.
• Track ionization and recombination sequences for all isotopes, including Li, He, and H, to model opacity and radiation pressure changes.
• Use gedanken experiments to simulate radiatively-driven implosions in small perturbations and radiatively-triggered expansion in dense galaxy clumps.
• Model the transition from radiation dominance to gravity dominance after massive stars explode and radiation sources are exhausted.

Experimental results

Research questions

• RQ1 How did radiative acceleration from massive Population III stars trigger the formation of globular clusters and galaxies in the early universe?
• RQ2 What role did radiation pressure play in the formation of cosmic voids, and how did it compete with gravitational collapse?
• RQ3 Why do observed abundances of Li, D, and 3He differ from standard Big Bang nucleosynthesis predictions, and how can this be reconciled with observations?
• RQ4 How did the intergalactic medium and microwave background radiation originate, and are they primordial or later-formed?
• RQ5 What explains the observed structure of the Milky Way, including its halo, bulge, disk, and globular cluster system, under a radiatively-driven formation model?

Key findings

• Radiation pressure from massive Population III stars triggered violent, rapid collapses that formed globular clusters of Population II stars, with implosions reaching near 100% completion.
• Galaxy-scale perturbations evolved into highly structured systems due to radiative acceleration, with non-symmetric density fluctuations generating angular momentum and complex dynamics.
• Voids formed via radiatively-driven expansion in dense clumps of galaxies, where radiation pressure overcame gravity in optically thick regions, especially in face-on spiral galaxies.
• The microwave background radiation is younger than the galaxies and originated after recombination, not as a primordial relic, due to late-time radiation processes.
• All matter in the universe was processed in stars: the interstellar medium and intergalactic medium are stellar products, not primordial, with the Milky Way's halo containing ~10^11 neutron stars and ~3×10^11 white dwarfs.
• The Milky Way's disk formed from gas lost by evolved halo stars, which collapsed and spun up due to angular momentum conservation, resulting in lower metallicity than the bulge despite later formation.