# Energy conditions In General Relativity, energy conditions constrain the stress tensor. Via Einstein's equation, such a constraint therefore also constrains the geometry. Different conditions are believed to hold at different levels. For example, it is generally expected that the Null Energy Condition (NEC) should hold classically but can be violated when quantum fields are included. See below for a list of conditions. ## Classical energy conditions - null energy condition ([[0480 Null energy condition|NEC]]) - violation by tunnelling - [[AlexandrePolonyi2021]]@[](https://arxiv.org/pdf/2101.08640.pdf) - dominant energy condition - average null energy condition ([[0417 Averaged null energy condition|ANEC]]) - ANEC is violated quantum mechanically - achronal ANEC (AANEC) - [[2007#Graham, Olum]] - [[2009#Wall (Oct)]]: GSL implies AANEC - self-consistent AANEC (SCAANEC) - [[2007#Graham, Olum]] - smeared NEC - [[FlissFreivogelKontou2021]][](https://arxiv.org/pdf/2111.05772.pdf) - [[2024#Fragoso, Guo]]: fermion, double smeared ## Quantum energy conditions - [[1965#Epstein, Glaser, Jaffe]]: shows that NEC is violated in QFT - [[2022#Swingle, van Raamsdonk]] ## Boundary energy condition from bulk ones - [[2021#Ishibashi, Maeda (Nov)]] - boundary ANEC on evaporating BH ## Related - [[0083 Traversable wormhole]] - [[0082 Generalised second law]]