From an October 2017 homepage:

Nima Arkani-Hamed¹ of the Institute for Advanced Studies in Princeton, with a sweeping naturalness, proclaims “Spacetime is doomed”² (go to 5:45 minutes of 1.22.44). His really-real reality is within his ever-so-illusive amplituhedron³ with a string to a planar N.⁴ He declares that it’s equal to the perturbative topological B-model string theory in twistor space⁵ (an ever-so-positive Grassmannian⁶) (related ArXiv article).

To which I reply, “Yes, of course. We knew that.”

1 The first link goes to our correspondence (mostly emails) to Nima Arkani-Hamed. He has also received a few tweets as well.

2 Spacetime is doomed is a YouTube video. If you go to 5:45 minutes of his 1 hour 22 minute lecture, you will hear that indeed, spacetime is doomed. The entire lecture is his focus on this concept.

3 The amplituhedron has a special place within our work. It was one of many basic structures and by no means is the most basic. The transformations between circles and spheres to lines and tetrahedra and then octahedra are.

We knew that:

4 The N=4 supersymmetric Yang–Mills theory within Wikipedia is entirely readable, but not easily understood.

5 Twistor space for perturbative topological B-model string theory

6 Grassmannian the set of -dimensional subspaces in an -dimensional vector space.