Do gauge fields really contribute negatively to black hole entropy?

Understand

Quantum fluctuations of matter fields contribute to the thermal entropy of black holes.

• For free minimally-coupled scalar and spinor fields, this contribution is precisely the entanglement entropy.
• For gauge fields, Kabat found an extra negative divergent "contact term" with no known statistical interpretation.
• We compare this contact term to a similar term that arises for nonminimally-coupled scalar fields.