Area Monotonicity of Wormhole Throats and a Geometric Bound on Information Transfer

Abstract

We develop a semiclassical geometric framework to constrain information transfer through traversable wormholes. This study is motivated by the growing intersection between spacetime geometry and quantum information theory, specifically the ER=EPR conjecture and the bit-thread formulation of holographic entropy. First, we prove a geometric monotonicity result for traversable wormhole throats, demonstrating that after a traversable window is established via an averaged null energy condition (ANEC) violating deformation, any subsequent signal-carrying matter satisfying the pointwise null energy condition (NEC) causes the throat cross-sectional area to be non-increasing. Second, we utilize this monotonicity to derive a semiclassical geometric upper bound on the number of independent quantum degrees of freedom (qubits) transmissible through the wormhole. This bound $Q_{\max} \leq A_{\min}/4G_N$, is motivated via the Max-Flow Min-Cut theorem for bit threads and interpreted as a geometric proxy for the holographic capacity of a quantum teleportation channel. We further discuss a holographic tensor-network analogy based on the HaPPY code, where the discrete max-flow/min-cut theorem provides an illustrative graph-theoretic counterpart of the bottleneck structure. Our results identify the wormhole throat as a natural geometric bottleneck, providing a geometric perspective on information-transfer limits in semiclassical gravity.