  We present results from multi-wavelength simultaneous X-ray and radio
observations of the black hole X-ray binary V404 Cyg in quiescence. Our
coverage with NuSTAR provides the very first opportunity to study the X-ray
spectrum of V404 Cyg at energies above 10 keV. The unabsorbed broad-band
(0.3--30 keV) quiescent luminosity of the source is 8.9$\times$10$^{32}$ erg
s$^{-1}$ for a distance of 2.4 kpc. The source shows clear variability on short
time scales (an hour to a couple of hours) in radio, soft X-ray and hard X-ray
bands in the form of multiple flares. The broad-band X-ray spectra obtained
from XMM-Newton and NuSTAR can be characterized with a power-law model having
photon index $\Gamma$=2.12$\pm$0.07 (90\% confidence errors); however,
residuals at high energies indicate spectral curvature significant at a
3$\sigma$ confidence level with e-folding energy of the cutoff to be
20$^{+20}_{-7}$ keV. Such curvature can be explained using synchrotron emission
from the base of a jet outflow. Radio observations using the VLA reveal that
the spectral index evolves on very fast time-scales (as short as 10 min.),
switching between optically thick and thin synchrotron emission, possibly due
to instabilities in the compact jet or stochastic instabilities in accretion
rate. We explore different scenarios to explain this very fast variability.
