They think about D and F strings. An extract:

"String theory presupposes nine or 10 spatial dimensions, that is six or seven more spatial dimensions than have heretofore been assumed to exist in addition to the one dimension of time. Some of the "extra" dimensions are thought to be curled up or compactified and therefore exceedingly small; and some, to be larger, perhaps infinite.

"In his attempts to understand Inflation in terms of string theory, Tye and collaborators envisioned our reality as contained in a three-dimensional "brane" sitting in higher dimensional space.

"Branes, a key conceptual breakthrough discovered by Polchinski in 1995, are essential structures in string theory in addition to strings. Instead of being only one-dimensional like strings, branes can have any dimensionality, including one. One-dimensional branes are called "D1 branes or D strings." So there are essentially two types of strings-- the heterotic string or "F" (for "fundamental") string, which physicists knew about prior to 1995, and the "D string," or one-dimensional brane.

"Tye and collaborators explained Inflation in terms of a brane and an anti-brane separating from each other and then attracting back together and annihilating. So a brane and an anti-brane existing in the extra dimensions would thereby provide the energy responsible for Inflation. Everything existing afterwards--our universe--is the product of their annihilation. And, according to the Tye models, at the end of Inflation, when brane and anti-brane annihilate, not only does their annihilation produce heat and light, but also long closed strings that could grow with the expansion of the universe."

Most any day now you'll find physicists thinking about G strings.