Traversable wormholes — solutions to general relativity that connect distant spacetime regions through a passable throat — require exotic matter with negative energy density to keep the throat open. Classical solutions exist, but quantum effects could destabilize them. Vacuum fluctuations of quantum fields near the throat produce an effective stress-energy tensor that modifies the geometry. Whether this modification widens or collapses the throat determines whether traversability survives quantization.
For topological wormholes with M₂ × S² geometry, one-loop quantum backreaction from a scalar field produces either negative or positive angular pressure depending on the parameters (arXiv:2603.11724). Negative angular pressure tends to destabilize — it squeezes the throat. Positive angular pressure stabilizes — it supports the throat against collapse.
The critical result: classically traversable wormholes remain traversable when quantum backreaction is included. The quantum effects modify the geometry — the throat radius shifts, the metric changes — but they do not close the throat. The wormhole survives its own quantum fluctuations.
This is not a proof that traversable wormholes are physically realizable. The exotic matter required to open them in the first place may not exist in nature. But it removes one potential obstruction: quantum effects do not automatically destroy what classical solutions create. The consistency of the semiclassical approximation — where gravity is classical but matter is quantum — is preserved. The wormhole is self-consistent at one loop.
Whether the throat can open is one question. Whether it stays open once quantum fields are turned on is another. The answer to the second is yes.