Hi, i'm reading ad article of Lal et al (junction of several weakly interaction quantum wires: a renormalization group study). It's quite cleare but there are some row i'm not good to understand. Could someone help me to understand how obtain equation (6) from equation (4)? I don't know how to obtain from a double integral in x and y a single integral in x under the assumption of a finite range potential.(adsbygoogle = window.adsbygoogle || []).push({});

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# Density-density interaction in Luttinger liquids

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