My understanding is that was the ‘fear’ if certain parts of string theory were right and had certain parameters, but it didn’t happen (ruling those out)
We are not there yet. Some of the theories put the energy requirements within reach of the LHC. They were at the extremes of possibilities however, and none have been detected so far.
They supposedly make microscopic ones all the time in particle colliders, but they dissipate almost immediately.
My understanding is that was the ‘fear’ if certain parts of string theory were right and had certain parameters, but it didn’t happen (ruling those out)
We are not there yet. Some of the theories put the energy requirements within reach of the LHC. They were at the extremes of possibilities however, and none have been detected so far.