  The conditions and evolution of protoplanetary disks in multiple systems can
be considerably different from those around single stars, which may have
important consequences for planet formation. We present Very Large Array (VLA)
8.8 mm (34 GHz) and 5 cm (6 GHz) observations of the quadruple system HD 98800,
which consists of two spectroscopic binary systems (Aa-Ab, Ba-Bb). The Ba-Bb
pair is surrounded by a circumbinary disk, usually assumed to be a debris disk
given its $\sim$10 Myr age and lack of near infrared excess. The VLA 8.8 mm
observations resolve the disk size (5-5.5 au) and its inner cavity ($\approx$3
au) for the first time, making it one of the smallest disks known. Its small
size, large fractional luminosity, and millimeter spectral index consistent
with blackbody emission support the idea that HD 98800 B is a massive,
optically thick ring which may still retain significant amounts of gas. The
disk detection at 5 cm is compatible with free-free emission from photoionized
material. The diskless HD 98800 A component is also detected, showing partial
polarization at 5 cm compatible with non-thermal chromospheric activity. We
propose that tidal torques from Ba-Bb and A-B have stopped the viscous
evolution of the inner and outer disk radii, and the disk is evolving via mass
loss through photoevaporative winds. This scenario can explain the properties
and longevity of HD 98800 B as well as the lack of a disk around HD 98800 A,
suggesting that planet formation could have more time to proceed in multiple
systems than around single stars in certain system configurations.
