The Dehn functions of Out(F_n) and Aut(F_n)

@article{Bridson2010TheDF,
  title={The Dehn functions of Out(F\_n) and Aut(F\_n)},
  author={Martin R. Bridson and Karen Vogtmann},
  journal={arXiv: Group Theory},
  year={2010}
}
For n > 2, the Dehn functions of Aut(F_n) and Out(F_n) are exponential. Hatcher and Vogtmann proved that they are at most exponential, and the complementary lower bound in the case n=3 was established by Bridson and Vogtmann. Handel and Mosher completed the proof by reducing the lower bound for n>4 to the case n=3. In this note we give a shorter, more direct proof of this last reduction. 
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TLDR
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