unitarity

There are two things, one is the definition of a probability and the other is unitarity.

So if unitarity is 1, then the interpretation of quantum field theories as probability distributions is straight forward.

Or this: [T]he new geometric approach to particle interactions removes locality and unitarity from its starting assumptions.

The star never crosses its horizon, so neither unitarity nor causality are violated, thereby solving the longstanding information loss paradox.

The reason for making this gauge choice is in order to make unitarity clear (/sorta automatic).

Usually with QFT you start with locality and unitarity as a sort of starting point.

An alternative route keeps manifest Lorentz invariance, but proceeding this way, unitarity is not clear.

Quantum field theory is the brainchild of the marriage of unitarity (from quantum mechanics) and the idea of locality (in field theory).

The positive grassmanian says nothing at all about unitarity or positivity, nothing about space or time, but it lets you calculate shit.

In finite regions of the universe, unitarity can therefore only be approximately known.

Right now, with Feynman diagrams, locality and unitarity are built in.

It's supported in both classical mechanics (Liouville's theorem, which is a vital component of the proof of Newton's second law) and in quantum mechanics (quantum unitarity).

The article states about unitarity and locality that "both are suspect".

But how could unitarity possibly be "suspect"?

Unitarity is aesthetic—it just “feels right”.

I understand it's kind of like "let's start without unitarity and locality baked in explicitly in the model and see where it leads and if they come out implicitly in the results".

Unitarity is basically the defining characteristic of quantum mechanics.

Unitarity is observable, that is closely connected to the information content of the system, and if memory serves to the evolution of the normalization factor of the wave function.