The rationally connected inequality for the delta-invariant

Let $X$ be a geometrically rationally connected smooth projective variety of dimension $n$, let $L$ be a big and nef $\mathbb Q$-divisor on $X$, let

$$a(X,L)=\inf\{t\in\mathbb R\mid K_X+tL\in\overline{\operatorname{Eff}}^1(X)\},$$

and let $\delta(X,L)$ be the delta-invariant defined via the stable base locus of divisors on the blow-up of the diagonal in $X\times X$. Rationally connected delta-invariant conjecture. One has

$$a(X,L)\leq 2n\delta(X,L).$$

The statement is motivated by Manin's conjecture and would compare the expected exponent of rational-point growth with the paper's general upper bound. It is presented as an expectation, with no resolution supplied in the source.