Axiverse and Black Hole
  String theory/M-theory generally predicts that axionic fields with a broad mass spectrum extending below 10^{-10}eV are produced after compactification to four dimensions. These axions/fields provoke a rich variety of cosmophysical phenomena on different scales depending on their masses and provide us new windows to probe the ultimate theory. In this article, after overviewing this axiverse idea, I take up the black hole instability as the most fascinating one among such axionic phenomena and explain its physical mechanism and astrophysical predictions. 
Hideo Kodama, Hirotaka Yoshino
hep-th astro-ph.CO astro-ph.HE gr-qc