  We present the results of our quasi-simultaneous radio, sub-mm, infrared,
optical and X-ray study of the Galactic black hole candidate X-ray binary MAXI
J1836-194 during its 2011 outburst. We consider the full multi-wavelength
spectral evolution of the outburst, investigating whether the evolution of the
jet spectral break (the transition between optically-thick and optically-thin
synchrotron emission) is caused by any specific properties of the accretion
flow. Our observations show that the break does not scale with the X-ray
luminosity or with the inner radius of the accretion disk, and is instead
likely to be set by much more complex processes. We find that the radius of the
acceleration zone at the base of the jet decreases from ~10$^6$ gravitational
radii during the hard intermediate state to ~10$^3$ gravitational radii as the
outburst fades (assuming a black hole mass of 8 M$_{\odot}$), demonstrating
that the electrons are accelerated on much larger scales than the radius of the
inner accretion disk and that the jet properties change significantly during
outburst. From our broadband modelling and high-resolution optical spectra, we
argue that early in the outburst, the high-energy synchrotron cooling break was
located in the optical band, between $\approx 3.2 \times 10^{14}$ Hz and $4.5
\times 10^{14}$ Hz. We calculate that the jet has a total radiative power of
$\approx 3.1 \times 10^{36}$ ergs s$^{-1}$, which is ~6% of the bolometric
radiative luminosity at this time. We discuss how this cooling break may evolve
during the outburst, and how that evolution dictates the total jet radiative
power. Assuming the source is a stellar-mass black hole with canonical state
transitions, from the measured flux and peak temperature of the disk component
we constrain the source distance to be 4-10 kpc.

High Energy Astrophysical Phenomena