We investigate the correlations in the current fluctuations at differentterminals of metallic diffusive conductors. We start from scattering matrixexpressions for the shot noise and use the Fisher-Lee relation in combinationwith diagram technique to evaluate the noise correlations. Of particularinterest are exchange (interference) effects analogous to the HanburyBrown--Twiss effect in optics. We find that the exchange effect exists in theensemble averaged current correlations. Depending on the geometry, it mighthave the same magnitude as the mean square current fluctuations of the shotnoise. The approach which we use is first applied to present a novel derivationof the 1/3-suppression of shot noise in a two-terminal geometry, valid for anarbitrary relation between the length and wire width. We find that in allgeometries correlations are insensitive to dephasing.
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