| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 102 === We explored the possibility that tachyons, whose energy-momentum relation is E^2 = P^2 -m^2, as a component of the matter content of the universe. We start from the behavior of its energy density and pressure, and also compare them with that of ordinary particles. With these results, using the constraint from the primordial neucleosynthesis, we determined the temperature of tachyons nowadays, and therefore indicated that the tachyons decoupled earlier than the photons in cosmic microwave background radiation (CMBR) . Then we can analyze the behavior of the size R of the universe in the existence of tachyons and get the null conclusion that this type of tachyon can not induce a inflationary bahavior on R, however, some tips in this research illustrate that there may be some other kinds of tachyon which may truly give us the required inflation, which has been carefully discussed in the end.
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