Or am I completely misunderstanding what it is saying?
The article talks about 2 different holograpic universes and then about our spacetime emerging from the primordial universe as higher spin symmetries broke.
One holographic universe, under an anti-de Sitter geometry (?), has a 3D spacetime reality with a 2 dimensional space and a 1 dimensional time where a 3rd (pseudo)space dimension emerges:
... Higher-spin fields promise to flesh out the holographic principle, which is a way to explain the origin of space and gravity. Suppose you have a hypothetical three-dimensional spacetime (two space dimensions, one time dimension) filled with particles that interact solely by a souped-up version of the strong nuclear force; there is no gravity. In such a setting, objects can behave in a very structured way. Objects of a given size can interact only with objects of comparable size, just as objects can interact only if they are spatially adjacent. Size plays exactly the same role as spatial position; you can think of size as a new dimension of space, materializing from particle interactions like a figure in a pop-up book. The original three-dimensional spacetime becomes the boundary of a four-dimensional spacetime, with the new dimension representing the distance from this boundary. Not only does a spatial dimension emerge, but so does the force of gravity. In the jargon, the strong nuclear force in 3-D spacetime (the boundary) is “dual” to gravity in 4-D spacetime (the bulk).
The other holographic universe, under a de Sitter universe, has a real 3D space dimensions lying in an infinite future and a 4th holographic dimension of time:
... In the real universe, dark energy has a positive density, for a de Sitter geometry or some approximation thereof. Extending the holographic principle to such a geometry is fraught. The boundary of 4-D de Sitter spacetime is a 3-D space lying in the infinite future. The emergent dimension in this case would not be of space but of time, which is hard even for theoretical physicists to wrap their minds around. But if they succeed in formulating a version of the holographic principle for a de Sitter geometry, it would not only apply to the real universe, but would also explain what time really is. A lack of understanding of time is at the root of almost every deep problem in fundamental physics today.
And then there is the emergence of our spacetime from the primordial universe:
... Matter and spacetime geometry are so thoroughly entwined that it becomes impossible to tease them apart, and our usual picture of matter as residing in spacetime becomes completely untenable. In the primordial universe, where Vasiliev theory reigned, the universe was an amorphous blob. As the higher-spin symmetries broke—for instance, as the higher harmonics of quantum strings become too costly to set into motion—spacetime emerged in its entirety.
Are these 3 different options? Or, if our universe emerged from a primordial amorphous blob, did it emerge into one of the holograpic universes described above - which one depending on the underlying geometry?
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