https://medium.com/starts-with-a-bang/embracing-your-fifth-dimension-2e02d9a0572c

“These dualities are said to be “holographic” because they tell us that everything allowed to happen in the bulk space-time of the gravitational theory is encoded on the boundary of that space.”

I find this boundary concept puzzling. Are they saying that our Universe is part of “the bulk”, bounded by 2-brains that form a 2-D box?

Alternatively, could it be that our Universe is considered as having a boundary, beyond which there is nothing?

There never was nothing.