From: helbig@asclothestro.multivax.de   
      
   In article , "Phillip Helbig (undress to   
   reply)"  writes:   
      
   > In article <5e356d1b$0$10259$e4fe514c@news.xs4all.nl>, Jos Bergervoet   
   >  writes:   
   >   
   > > After the merger of two black holes there is a "ringdown" in which the   
   > > new black hole radiates off some energy.   
   > >   
   > > Presumably this ringdown amplitude decays exponentially, so it never   
   > > becomes exactly zero. We can also easily imagine (although not easily   
   > > test experimentally) the reverse: some incoming gravitational radiation   
   > > which is nicely focussed on an existing balck hole makes it "ring up"   
   > > instead of ring down..   
   > >   
   > > But if a black hole can have vibration amplitudes, for lots of spherical   
   > > harmonics as it seems, doesn't that violate the no-hair theorem?   
   >   
   > No, because the no-hair conjecture (it hasn't actually been proved)   
   > applies to static black holes.   
      
   As Jonathan Thornburg pointed out in a followup, "static" should be   
   "stationary".  (Obviously it does apply to rotating black holes, since   
   angular momentum is one of the three characteristics a hairless black   
   hole is allowed to have, along with mass and charge, and obviously   
   something rotating is not static---but it is stationary.)   
      
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