# Does QFT Imply Strings the Same Way that String Theory Implies Branes?

It is part of every introductory course on string theory (e.g. Tong) that the open bosonic string in $$D = 26$$ dimensions with Neumann-Neumann boundary conditions for directions $$a \in \{0,\dots,p\}$$ and Dirichlet boundary conditions in directions $$I \in \{p+1,\dots,D-1\}$$ implies the existence of a non-perturbative object, the $$D_p$$ brane, a $$p$$-dimensional submanifold of the total space. The idea is of course that the $$D_p$$ brane is the subspace on which the open string with Neumann-Neumann boundary conditions ends. It is also generally known, even though non-trivial, that branes are as important as strings and that therefore general string theory is not only a theory of strings but also of branes.

My question is now, if there is a similar indication of strings or higher-dimensional objects that are as important as particles in QFT? It comes of course to mind that string theory was at first introduced as a candidate for the strong force to model flux tubes, later replaced by QCD. Furthermore, I know that there one can model flux tubes in superconductors as strings. So I guess my question is about further emergent or fundamental "stringy" or "brane-y" systems that cannot be modeled by theories that only work with "points". I find the idea that fundamental physics needs objects of different dimensions to work interesting, but am not sure if this is only something implied by string theory.