  Knowledge of the low-lying monopole strength in $\mathrm{^{12}C}$ $-$ the
Hoyle state in particular $-$ is crucial for our understanding of both the
astrophysically important $3\alpha$ reaction and of $\alpha$-particle
clustering. Multiple theoretical models have predicted a breathing mode of the
Hoyle State at $E_{x} \approx 9$ MeV, corresponding to a radial in-phase
oscillation of the underlying $\alpha$ clusters. The $\mathrm{^{12}C}(\alpha,
\alpha^{\prime})\mathrm{^{12}C}$ and $\mathrm{^{14}C}(p, t)\mathrm{^{12}C}$
reactions were employed to populate states in $^{12}$C in order to search for
this predicted breathing mode. A self-consistent, simultaneous analysis of the
inclusive spectra with R-matrix lineshapes, together with angular distributions
of charged-particle decay, yielded clear evidence for excess monopole strength
at $E_{x} \approx 9$ MeV which is highly collective. Reproduction of the
experimentally observed inclusive yields using a fit, with consistent
population ratios for the various broad states, required an additional source
of monopole strength. The interpretation of this additional monopole resonance
as the breathing-mode excitation of the Hoyle state would provide evidence
supporting a $\mathcal{D}_{3h}$ symmetry for the Hoyle state itself. The excess
monopole strength may complicate analysis of the properties of the Hoyle state,
modifying the temperature dependence of the $3\alpha$ rate at $T_{9} \gtrsim 2$
and ultimately, the predicted nucleosynthesis in explosive stars.
