We introduce a new family of primordial cosmological perturbations that are not described by traditional power spectra .
At the linear level , these perturbations live in the kernel of the spatial Laplacian operator , and thus we call them cosmological zero modes .
We compute the cosmic microwave background ( CMB ) temperature and polarization anisotropy induced by these modes , and forecast their detection sensitivity using a cosmic-variance limited experiment .
In particular , we consider two configurations for the zero modes : The first configuration consists of stochastic metric perturbations described by white noise on a “ holographic screen ” located at our cosmological horizon .
The amplitude of the power spectrum of this white noise can be constrained to be \lesssim 9 \times 10 ^ { -14 } .
The second configuration is a primordial monopole beyond our cosmological horizon .
We show that such a monopole , with “ charge ” Q , can be detected in the CMB sky up to a distance of 11.6 ~ { } Q ^ { 1 / 4 } \times horizon radius ( or 160 ~ { } Q ^ { 1 / 4 } Gpc ) .
More generally , observational probes of cosmological zero modes can shed light on non-perturbative phenomena in the primordial universe , beyond our observable horizon .