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Nonconservation of "charges" falling into a black hole



"James W. Wheeler" <jwheeler@eagle.lhup.edu> writes:

A question. Electrically charged black holes are allowed (magnetic charge
too if one believes in monopoles), what about hypercharge, baryon
and lepton number (assuming non-decay of protons) and color? Will any
*conserved* charge leave its mark on the black hole?

No, the only charges that a black hole may possess are those associated with
long-range forces (i. e. with exchange particles that are massless, which means
the graviton and the photon). The other charges that you measure are associated
with short-range forces, so the corresponding quantum numbers are "lost" as the
particles fall into the black hole. Thus a black hole can have only those
attributes that couple to the gravitational field (i. e. mass and angular
momentum) or to the electromagnetic field (i. e. electric charge).

This is a well-known effect, which I believe is described in most introductory
treatises on black holes. See also the following original references:

J. D. Bekenstein, Phys. Rev. D5, 1239 (1972) and D5, 2403 (1972).
C. Teitelboim, Lett. Nuovo Cimento 3, 326 (1972).



+++++++++++++++++++++++++++++++++++++++++++++++++++++++

Roger A. Freedman
Department of Physics and College of Creative Studies
University of California, Santa Barbara

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