标题： 类时平均 null 能量条件 显示英文标题

标题： Achronal averaged null energy condition

摘要： 平均无能条件（ANEC）要求，应力-能量张量投影到测地线切向量上的完整无测地线积分永远不会为负。 这一条件足以证明广义相对论中的许多重要定理，但在弯曲时空中的量子场却违反了它。 然而，存在一个较弱的条件，没有已知的违反情况，仅要求在半经典引力中不存在完整的{\em 非时序的}无测地线，其上ANEC不会被违反。 我们指出为何可能会期望这种条件成立，并表明它足以排除虫洞和闭合类时曲线的存在。 显示英文摘要

摘要： The averaged null energy condition (ANEC) requires that the integral over a complete null geodesic of the stress-energy tensor projected onto the geodesic tangent vector is never negative. This condition is sufficient to prove many important theorems in general relativity, but it is violated by quantum fields in curved spacetime. However there is a weaker condition, which is free of known violations, requiring only that there is no self-consistent space-time in semiclassical gravity in which ANEC is violated on a complete, {\em achronal} null geodesic. We indicate why such a condition might be expected to hold and show that it is sufficient to rule out wormholes and closed timelike curves.