We develop, from first principles, a general and compact formalism forpredicting the electromagnetic response of a metamaterial with non-magneticinclusions in the long wavelength limit, including spatial dispersion up to thesecond order. Specifically, by resorting to a suitable multiscale technique, weshow that medium effective permittivity tensor and the first and second ordertensors describing spatial dispersion can be evaluated by averaging suitablespatially rapidly-varying fields each satysifing electrostatic-like equationswithin the metamaterial unit cell. For metamaterials with negligiblesecond-order spatial dispersion, we exploit the equivalence of first-orderspatial dispersion and reciprocal bianisotropic electromagnetic response todeduce a simple expression for the metamaterial chirality tensor. Such anexpression allows us to systematically analyze the effect of the compositespatial symmetry properties on electromagnetic chirality. We find that even ifa metamaterial is geometrically achiral, i.e. it is indistinguishable from itsmirror image, it shows pseudo-chiral-omega electromagnetic chirality if therotation needed to restore the dielectric profile after the reflection iseither a $0^\circ$ or $90^\circ$ rotation around an axis orthogonal to thereflection plane. These two symmetric situations encompass two-dimensional andone-dimensional metamaterials with chiral response. As an example admittingfull analytical description, we discuss one-dimensional metamaterials whosesingle chirality parameter is shown to be directly related to the metamaterialdielectric profile by quadratures.
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