In Ref.1 (L. Boyle, K. Finn and N. Turok, CPT-Symmetric Universe, Phys. Rev.
Lett. {\bf 121}, 251301 (2018)) the antispacetime Universe was suggested as the
analytic continuation of our Universe across the Big Bang singularity in
conformal time. We consider two different scenarios of analytic continuation.
In one of them the analytic continuation is extended to the temperature of the
system. This extension suggests that if such analytic continuation is valid,
then it is possible that the initial stage of the evolution of the Universe on
our side of the Big Bang was characterized by the negative temperature. In the
second scenario, the analytic continuation is considered in the proper time. In
this scenario the Big Bang represents the bifurcation point at which the Z2
symmetry between the spacetime and antispacetime is spontaneously broken.Comment: 2 pages, 1 figure, comment to PRL 121, 251301 (2018), accepted in
JETP Letter
