Theoretical analysis reveals local horizon residues and perturbed scalar quasinormal modes in quadratic f(Q) gravity, indicating modified near-horizon and photon-sphere dynamics.
We study the local horizon residue and minimally coupled massless-scalar quasinormal modes of the logarithmic connection-hair background obtained perturbatively in the quadratic model f(Q)=Q+α Q² f ( Q ) = Q + α Q 2 . After mass renormalization the displayed order- α ² α 2 blackening function is F(r)=1-[2M+η ln (r/r_ )]/r F ( r ) = 1 - [ 2 M + η ln ( r / r ⋆ ) ] / r , with η =α ²μ η = α 2 μ . Euclidean regularity and the simple pole of 1/ F give the same Hawking temperature, while the same residue multiplies the near-horizon logarithm of the scalar tortoise coordinate. We derive the massless-scalar master equation, its effective potential, the photon-sphere equation, and the controlled first-order shifts of the eikonal scalar frequency and damping rate. We do not identify the integration parameter M with a Hamiltonian or Noether mass: the logarithmic tail leaves the perturbative regime at large radius and does not satisfy the standard falloff required for a finite ADM charge. Consequently no physical entropy, heat capacity, Ruppeiner metric, or gravitational quasinormal-mode spectrum is claimed. For comparison only, we retain an explicitly labelled auxiliary Hessian construction and an algebraic evaluation of the resummed truncated metric at rₕ=2η r h = 2 η . That point has |η |/rₕ=1/2 | η | / r h = 1 / 2 and is therefore outside perturbative control; its finite scalar null-orbit and WKB frequencies are properties of the truncated function, not predictions of quadratic f ( Q ) gravity. The controlled result is the local temperature–scalar-monodromy residue identity and the distinct small-hair shifts sampled at the horizon and photon sphere.
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Wen-Xiang Chen (2026) studied this question.
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