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Power-law singularities in string theory and M-theory

We extend the definition of the Szekeres–Iyer power-law singularities to supergravity, string and M-theory backgrounds, and find that are characterized by Kasner-type exponents. The near singularity geometries of brane and some intersecting brane backgrounds are investigated and the exponents are computed. The Penrose limits of some of these power-law singularities have profiles A ∼ u−γ for γ ⩾ 2. We find the range of the exponents for which γ = 2 and the frequency squares are bounded by 1/4. We propose some qualitative tests for deciding whether a null or timelike spacetime singularity can be resolved within string theory and M-theory based on the near singularity geometry and its Penrose limits.