  Filaments connecting halos are a long-standing prediction of cold dark matter
theories. We present a novel detection of the cosmic web emission connecting
two massive quasar-host galaxies at cosmic noon in the MUSE Ultra Deep Field
(MUDF) using unprecedentedly deep observations that unlock a high-definition
view of the filament morphology, a measure of the transition radius between the
intergalactic and circumgalactic medium, and the characterization of the
surface brightness profiles along the filament and in the transverse direction.
Through systematic comparisons with simulations, we validate the filaments'
typical density predicted in the current cold dark matter model. Our analysis
of the MUDF field, an excellent laboratory for quantitatively studying
filaments in emission, opens a new avenue to understanding the cosmic web that,
being a fundamental prediction of cosmology, bears key information on the
essence of dark matter.
