On the basis of a number of Swampland conditions, we argue that the Hilbert space of baby universe states must be one-dimensional in a consistent theory of quantum gravity. This scenario may be interpreted as a type of "Gauss's law for entropy" in quantum gravity, and provides a clean synthesis of the tension between Euclidean wormholes and a standard interpretation of the holographic dictionary, with no need for an ensemble. Our perspective relies crucially on the recently-proposed potential for quantum-mechanical gauge redundancies between states of the universe with different topologies. By an application of the state-operator correspondence, this proposal rules out the possibility of nontrivial, strictly well-defined bulk operators supported in a compact region. We further comment on the possible exceptions in $d\leq 3$ for this hypothesis, and the role of an ensemble for holographic theories in low dimensions, such as JT gravity in $d = 2$ and possible cousins in $d=3$. We argue that these examples are incomplete physical theories that should be viewed as branes in a higher dimensional theory of quantum gravity, for which an ensemble plays no role.
Holography and the Swampland: Constraints on Quantum Gravity from Holographic Principles
Inter-University Centre for Astronomy and Astrophysics (IUCAA)（大学间天文学与天体物理学中心）；Department of Physics, K.L.S. College, Nawada, Magadh University（那达德KLS学院物理系，马加德大学）；Center for Theoretical Physics, Tomsk State Pedagogical University（托木斯克国立师范学院理论物理中心）；National Research Tomsk Polytechnic University（托木斯克理工大学国家研究型大学）；Núcleo Interdisciplinar de Ciências Exatas e da Natureza, NICEN, Universidade Federal de Pernambuco（伯南布哥联邦大学精确与自然科学跨学科核心）；Department of Nuclear Physics, Institute of Physics, University of São Paulo（圣保罗大学物理研究所核物理系）
Strong-to-Weak Spontaneous Symmetry Breaking from Wormholes in Holography
Kyoto University（京都大学）；The Hakubi Center for Advanced Research, Kyoto University（京都大学博慧中心）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）；University of Tokyo（东京大学）；Kavli Institute for the Physics and Mathematics of the Universe, UTIAS, University of Tokyo（东京大学宇宙起源研究前沿中心卡弗里宇宙物理学与数学研究所）；Trans-Scale Quantum Science Institute, University of Tokyo（东京大学跨尺度量子科学研究所）；Center for Interdisciplinary Theoretical and Mathematical Sciences, RIKEN（理化学研究所跨学科理论与数学科学中心）
Asymptotic safety, quantum gravity, and the swampland: a conceptual assessment
Arnold-Sommerfeld Center for Theoretical Physics, Ludwig Maximilians Universität München（慕尼黑大学阿诺德-索末菲理论物理中心）；Max-Planck-Institut für Physik (Werner-Heisenberg-Institut)（马克斯·普朗克物理研究所（维尔纳·海森堡研究所））；Institute for Theoretical Physics, Heidelberg University（海德堡大学理论物理研究所）；Niels Bohr International Academy, The Niels Bohr Institute（尼尔斯·玻尔国际学院，尼尔斯·玻尔研究所）；High Energy Physics Department, Institute for Mathematics, Astrophysics, and Particle Physics, Radboud University（拉德堡德大学数学、天体物理和粒子物理研究所高能物理系）
Toward Krylov-based holography in double-scaled SYK
Gwangju Institute of Science and Technology（光州科学技术院）；Instituto de Física Teórica UAM/CSIC（马德里自治大学/西班牙国家科研中心理论物理研究所）；Asia Pacific Center for Theoretical Physics（亚太理论物理中心）；Pohang University of Science and Technology（浦项科技大学）；Research Center for Photon Science Technology, Gwangju Institute of Science and Technology（光州科学技术院光子科学与技术研究中心）
University of Tokyo（东京大学）；Kavli Institute for Physics and Mathematics of the Universe (Kavli IPMU), UTIAS, University of Tokyo（东京大学宇宙线研究所（Kavli IPMU））；Trans-Scale Quantum Science Institute, University of Tokyo（东京大学跨尺度量子科学研究所）；Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), RIKEN（理化学研究所交叉理论数学科学中心（iTHEMS））
