From: carlip@physics.ucdavis.edu   
      
   On 5/5/18 11:06 PM, Phillip Helbig (undress to reply) wrote:   
      
   > Two questions:   
   > First, if negative-mass black holes don't exist, can one by the same   
   > argument rule out negative-mass hammers?   
      
   With very high probability.  In principle, a quantum fluctuation   
   could create a negative mass hammer (with a *very* short lifetime),   
   provided there is a larger positive energy fluctuation elsewhere.   
   It's a safe bet that this hasn't happened, though there are people   
   who argue that if the universe is asymptotically de Sitter, such   
   a fluctuation is inevitable eventually.   
      
   > Second, isn't there a contradiction in your second statement?  If it is   
   > not true that a negative-mass particle would be repelled by a   
   > (positive-mass) black hole, why should a negative-mass black hole repel   
   > a positive-mass (or negative-mass) particle?  Aren't the two cases   
   > equivalent, due to symmetry?   
      
   There's no symmetry.  Positive mass attracts everything, negative   
   mass repels everything.  That means if you had a positive mass hammer   
   and a negative mass hammer and you put them next to each other, the   
   positive mass would attract the negative mass, the negative mass   
   would repel the positive mass, and the system would spontaneously   
   accelerate.  This wouldn't violate energy conservation -- the   
   negative mass hammer would have negative kinetic energy, and the   
   total energy would remain zero -- but it's still not good: it's   
   an illustration of the fact that a system that allows long-lived   
   negative energy excitations is never stable.   
      
   Steve Carlip   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)