Explaining low $$\ell $$ ℓ anomalies in the CMB power spectrum with resonant superstring excitations during inflation

Abstract

Abstract We explore the possibility that both the suppression of the $$\ell = 2$$ ℓ=2 multipole moment of the power spectrum of cosmic microwave background temperature fluctuations and the possible dip for $$\ell = 10$$ ℓ=10 –30 can be explained as well as a possible new dip for $$\ell \approx 60$$ ℓ≈60 as the result of the resonant creation of sequential excitations of a fermionic (or bosonic) closed superstring that couples to the inflaton field. We consider a D$$\,=\,$$ = 26 closed bosonic string with one toroidal compact dimension as an illustration of how string excitations might imprint themselves on the CMB. We analyze the existence of successive momentum states, winding states or oscillations on the string as the source of the three possible dips in the power spectrum. Although the evidence of these dips are of marginal statistical significance, this might constitute the first observational evidence of successive superstring excitations in Nature.