Clarifying the notion of ‘excitation of a degree of freedom’ in string theory

Clarify and formalize the microphysical meaning of ‘exciting a degree of freedom’ in the context of string theory, particularly for background fields and compactification modes, so that claims about their excitation by available energies can be assessed within a coherent theoretical framework.

Background

In assessing Penrose’s argument that ambient energies could excite compactification modes and unleash extra-dimensional degrees of freedom, the authors stress that the underlying notion of ‘exciting a degree of freedom’ is not well defined in this context. They suggest that a field-theoretic microphysical account—e.g., via string field theory—might supply a coherent meaning, but this is not explicitly provided by Penrose and raises issues of localization and energy density.

Without a precise definition, it is difficult to evaluate claims about excitation of background or compactification modes and their phenomenological impact, making this conceptual clarification necessary for properly assessing such arguments.