Paper detail

Generalized Tsirelson's bound from parity symmetry considerations

The Bell experiment is a random game with two binary outcomes whose statistical correlation is given by $E_0(Θ)=-\cos(Θ)$, where $Θ\in [-π, π)$ is an angular input that parameterizes the game setting. The correlation function $E_0(Θ)$ belongs to the affine space ${\cal H} \equiv \left\{E(Θ)\right\}$ of all continuous and differentiable periodic functions $E(Θ)$ that obey the parity symmetry constraints $E(-Θ)=E(Θ)$ and $E(π-Θ)=-E(Θ)$ with $E(0)=-1$ and, furthermore, are strictly monotonically increasing in the interval $[0, π)$. Here we show how to build explicitly local statistical models of hidden variables for random games with two binary outcomes whose correlation function $E(Θ)$ belongs to the affine space ${\cal H}$. This family of games includes the Bell experiment as a particular case. Within this family of random games, the Bell inequality can be violated beyond the Tsirelson bound of $2\sqrt{2}$ up to the maximally allowed algebraic value of 4. In fact, we show that the amount of violation of the Bell inequality is a purely geometric feature.