COMPLEXITY GRADIENT. “Operators supported on the outer edge of the near‐horizon region—the onion skin—have the minimal complexity. As we peel the onion, the complexity increases. Eventually we get to the Planckian layer where the complexity has increased to a particular value .”
https://onlinelibrary.wiley.com/doi/full/10.1002/prop.201500092?casa_token=8OO3b1OY4e4AAAAA%3ARqriAgTwtxnvsxl09CqnNy79m7l4ye7ZrkZxcLtObB9kHsTwYgzBuIV2X-xXQ7ezoR6VQPfQLCS-vnI