We propose a method to reconstruct smeared spectral functions from two-point correlation functions measured on the Euclidean lattice. An arbitrary smearing function can be considered as long as it is smooth enough to allow an approximation using Chebyshev polynomials. We test the method with numerical lattice data of charmonium correlators. The method provides a framework to compare lattice calculation with experimental data including excited-state contributions without assuming quark–hadron duality.

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Finite-volume effects for the nucleon chiral partners are studied within the framework of the parity-doublet model. Our model includes the vacuum energy shift for nucleons, which is the Casimir effect. We find that for the antiperiodic boundary the finite-volume effect leads to chiral symmetry restoration, and the masses of the nucleon parity doublets degenerate. For the periodic boundary, the chiral symmetry breaking is enhanced, and the masses of the nucleons also increase. We also discuss the finite-temperature effect and the dependence on the number of compactified spatial dimensions.