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  "path": "/abs/2605.10802v1",
  "publishedAt": "2026-05-12T00:00:00.000Z",
  "site": "https://arxiv.org",
  "tags": [
    "Argyrios Deligkas",
    "John Fearnley",
    "Alexandros Hollender",
    "Themistoklis Melissourgos"
  ],
  "textContent": "**Authors:** Argyrios Deligkas, John Fearnley, Alexandros Hollender, Themistoklis Melissourgos\n\nWe study the problem of computing approximate market equilibria in Fisher markets with separable piecewise-linear concave (SPLC) utility functions. In this setting, the problem was only known to be PPAD-complete for inverse-polynomial approximations. We strengthen this result by showing PPAD-hardness for constant approximations. This means that the problem does not admit a polynomial time approximation scheme (PTAS) unless PPAD$=$P. In fact, we prove that computing any approximation better than $1/11$ is PPAD-complete. As a direct byproduct of our main result, we get the same inapproximability bound for Arrow-Debreu exchange markets with SPLC utility functions.",
  "title": "Constant Inapproximability for Fisher Markets"
}