Inflation-PNAS.pdfVIP

Proc. Natl. Acad. Sci. USA Vol. 90, pp. 4871-4877, June 1993 Colloquium Paper This paper was presented at a coUoquium entitled Physical Cosmology, organized by a committee chaired by David N. Schramm, held March 27 and 28, 1992, at the National Academy of Sciences, Irvine, CA. Inflation ALAN H. GUTH Center for Theoretical Physics, Laboratory for Nuclear Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 ABSTRACT A short review of inflation is given, starting a box, letting the size of the box approach infinity at the end with a description of the underlying mechanism and the of the calculation. One can then think of the electromagnetic scenario of events. Four variations-old inflation, new infla- fields inside the box as a mechanical system. The field can be tion, chaotic inflation, and extended inflation-are discussed. expanded as a sum of normal modes, and the coefficients of It is claimed that the inflationary model provides a plausible the normal mode functions can be taken as the dynamical explanation for (i) the large number ofparticles in the universe, degrees of freedom of the system. It turns out that each of (ii) the Hubble expansion, (iii) the large-scale uniformity ofthe these coefficients obeys the equations of a harmonic oscil- universe, (iv) the nearness of the universe to a critical density, lator, and there is no interaction between the coefficients. (v) the absence of magnetic monopoles, and (vi) the scale- The system is quantized by the same rules that one uses to invariant spectrum of microwave background fluctuations quantize the harmonic oscillator, and the result is that each observed by COBE (Cosmic Background Explorer). Finally, it normal mode has evenly spaced energy levels. In this case, is argued that the plausibility ofinflation is enhanced by the fact we interpret the nth excited state as the state that contains n that inflation is eternal. photons in the specified mod