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    "title": "A neutral excitation gap forces zero charge susceptibility in local quantum matter",
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        "title": "Energy gap of neutral excitations implies vanishing charge susceptibility (arXiv1609.09543v3)",
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        "description": "The argument uses local Hamiltonian and charge densities, a well-defined reservoir and thermodynamic response limit, and a unique ground state within the selected charge sector. Its extension to symmetry-breaking degeneracy relies on suppressed matrix elements between the distinct states. The conclusion is zero susceptibility at the specified chemical potential; it does not by itself prove a plateau on a finite interval or a gap to charged excitations. The converse fails: gapless neutral excitations can coexist with zero susceptibility or a magnetization plateau.",
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          "citation": "Energy gap of neutral excitations implies vanishing charge susceptibility (arXiv1609.09543v3)",
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      "statement": "# A neutral excitation gap forces zero charge susceptibility in local quantum matter\n\nWatanabe connected a gap within a fixed conserved-charge sector to the static response of that charge at zero temperature. For local quantum systems with a U(1) symmetry, a subregion charge fluctuation creates a neutral variational excitation. The boundary cost of this excitation forces charge fluctuations per volume to vanish when the neutral gap stays positive. Combining this with a susceptibility bound gives zero charge susceptibility, without translation symmetry or a quasiparticle description. The result clarifies part of the connection between magnetization plateaus and neutral-excitation constraints.\n\n## Scientific scope\n\nThe argument uses local Hamiltonian and charge densities, a well-defined reservoir and thermodynamic response limit, and a unique ground state within the selected charge sector. Its extension to symmetry-breaking degeneracy relies on suppressed matrix elements between the distinct states. The conclusion is zero susceptibility at the specified chemical potential; it does not by itself prove a plateau on a finite interval or a gap to charged excitations. The converse fails: gapless neutral excitations can coexist with zero susceptibility or a magnetization plateau.\n\n## Reading status\n\nThis is a source-linked WRS catalogue note. A full explanatory guide and independent scientific reconstruction have not been completed for this entry. Read the identified original work for its complete narrative and arguments.\n\n## People and systems\n\nHaruki Watanabe\n\nThese are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.\n\n\n\n## Original sources\n\n- [Energy gap of neutral excitations implies vanishing charge susceptibility (arXiv1609.09543v3)](https://arxiv.org/pdf/1609.09543v3)\n",
      "summary": "Watanabe connected a gap within a fixed conserved-charge sector to the static response of that charge at zero temperature. For local quantum systems with a U(1) symmetry, a subregion charge fluctuation creates a neutral variational excitation. The boundary cost of this excitation forces charge fluctuations per volume to vanish when the neutral gap stays positive. Combining this with a susceptibility bound gives zero charge susceptibility, without translation symmetry or a quasiparticle description. The result clarifies part of the connection between magnetization plateaus and neutral-excitation constraints.",
      "title": "A neutral excitation gap forces zero charge susceptibility in local quantum matter"
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    "id": "watanabe-neutral-gap-vanishing-charge-susceptibility-2016",
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    "title": "A neutral excitation gap forces zero charge susceptibility in local quantum matter",
    "context": "Condensed matter theory / gaps and incompressibility",
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    "what_changed": "Watanabe connected a gap within a fixed conserved-charge sector to the static response of that charge at zero temperature. For local quantum systems with a U(1) symmetry, a subregion charge fluctuation creates a neutral variational excitation. The boundary cost of this excitation forces charge fluctuations per volume to vanish when the neutral gap stays positive. Combining this with a susceptibility bound gives zero charge susceptibility, without translation symmetry or a quasiparticle description. The result clarifies part of the connection between magnetization plateaus and neutral-excitation constraints.",
    "scope": "Watanabe connected a gap within a fixed conserved-charge sector to the static response of that charge at zero temperature. For local quantum systems with a U(1) symmetry, a subregion charge fluctuation creates a neutral variational excitation. The boundary cost of this excitation forces charge fluctuations per volume to vanish when the neutral gap stays positive. Combining this with a susceptibility bound gives zero charge susceptibility, without translation symmetry or a quasiparticle description. The result clarifies part of the connection between magnetization plateaus and neutral-excitation constraints. The argument uses local Hamiltonian and charge densities, a well-defined reservoir and thermodynamic response limit, and a unique ground state within the selected charge sector. Its extension to symmetry-breaking degeneracy relies on suppressed matrix elements between the distinct states. The conclusion is zero susceptibility at the specified chemical potential; it does not by itself prove a plateau on a finite interval or a gap to charged excitations. The converse fails: gapless neutral excitations can coexist with zero susceptibility or a magnetization plateau.",
    "evidence_summary": "The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The argument uses local Hamiltonian and charge densities, a well-defined reservoir and thermodynamic response limit, and a unique ground state within the selected charge sector. Its extension to symmetry-breaking degeneracy relies on suppressed matrix elements between the distinct states. The conclusion is zero susceptibility at the specified chemical potential; it does not by itself prove a plateau on a finite interval or a gap to charged excitations. The converse fails: gapless neutral excitations can coexist with zero susceptibility or a magnetization plateau.",
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