A cosmological model generally credited to Guth (1981), although other forms of the idea were previously published elsewhere (e.g., by Demosthenes Kazanas). According to grand unified field theories, matter and energy behaved as if they had negative gravity and produced a brief very rapid cosmic expansion. This process drives , where is the critical density, to a value very close to 1, explaining the paradox of why the observed value should be so close to unity.