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Register a new userAstrophysical Violations of the Kerr Bound as a Possible Signature of String Theory
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In 4D general relativity, the angular momentum of a black hole is limited by the Kerr bound. We suggest that in string theory, this bound can be breached and compact black-hole-like objects can spin faster. Near such superspinars, the efficiency of energy transfer from the accreting matter to radiation can reach 100%, compared to the maximum efficiency of 42% of the extremal Kerr (or 6% of the Schwarzschild) black hole. Finding such superspinning objects as active galactic nuclei, GBHCs, or sources of gamma ray bursts, could be viewed as experimental support for string theory.
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We construct a model of quintessence in string theory based on the idea of axion monodromy as discussed by McAllister, Silverstein and Westphal arXiv:0808.0706. In the model, the quintessence field is an axion whose shift symmetry is broken by the presence of 5-branes which are placed in highly warped throats. This gives rise to a potential for the axion field which is slowly varying, even after incorporating the effects of moduli stabilization and supersymmetry breaking. We find that the resulting time dependence in the equation of state of Dark Energy is potentially detectable, depending on the initial conditions. The model has many very light extra particles which live in the highly warped throats, but these are hard to detect. A signal in the rotation of the CMB polarization can also possibly arise.
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In this contribution we go through the developments that in the years 1968 to 1974 led from the Veneziano model to the bosonic string.
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