We propose a new type of cosmological model by assuming that not only the temperature but also the curvature is limited to the mass scale of the Hagedorn temperature. We find that the big bang of this universe is smoothly connected to the big crunch of the previous universe through the Hagedorn universe in which the temperature and the curvature remain very close to their limiting values. Thus, we reach the picture of the cyclic universe. By estimating the entropy gained in each big crunch and big bang, we obtain the picture that our universe has repeated this process about forty times after it was created in the Planck scale. We also show that the model gives a scale-invariant spectrum of curvature perturbation.
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