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In the membrane model, when a baryon hits the event horizon its spatially separated quarks will impact the membrane at different times.

Doesn't this necessarily mean that black holes acquire, however transiently, color charge?

That is, in addition to mass, angular momentum, and electrical charge, a full accounting of the defining characteristics of a black hole must also include color charge? (And yes, weak hypercharge too.)

One way to interpret the above is that at the moment that, say, a down quark within a neutron hits the event horizon, the entire black hole very briefly becomes a mega-down-quark with $-1/3$ electrical charge and whatever color charge the down quark had at the time of impact.

So... does this argument mean that black holes are a bit hairier that is usually asserted?

Terry Bollinger
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2 Answers2

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There are a couple of reasons why your question isn't answerable.

Firstly if you're sitting outside the horizon trying to measure the colour of the particle then you'll never see it reach the horizon, let alone cross it, so you would just measure a white particle as usual. If you were sitting alongside the particle as it fell then there would be no horizon and you and the particle would be in a roughly flat spacetime (give or take a few tidal forces). Again the particle would remain white.

Secondly your argument relies upon the quarks being sufficiently localised that one quark can be said to cross the horizon before the other two. I can't think of any way you could achieve this. What would actually happen is that the probability distributions of the quarks would all overlap so you wouldn't have, for example, a red leading edge and a blue trailing edge.

John Rennie
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I think John's answer works in conjunction with the fact that the strong (and weak) force has massive mediating particles and hence is short range. There is no equivalent of the electric field and gravitational field that must survive beyond the event horizon and which could be observed a long range. Thus the only way you could observe the situation you pose is indeed to get up close to the particle in question.

There is more detail in No hair theorem for black holes and the baryon number and Black hole "no hair" theorem

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ProfRob
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