I want to find out the book which I've read some time ago. Now i don't remember who were the authors and exact title.
This book was on scattering theory or S-matrix or something similiar. I remember, that there are chapters with titles like S-matrix for scattering of spin 0, spin 1.
The...
zero-point energy is not observable, so no any sense to talk about its value and sign.
there are 2 contributions to curvature - from normal matter and dark one. so even without normal matter the curvature of space may be nonflat.