2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/167660We discuss recent developments in the understanding of gauge-invariant transverse-momentum dependent (TMD) parton-distribution functions (PDF). We compute the leading-order $\overline{\text{MS}\vphantom{^1}}$-scheme anomalous dimension of such a quantity in the light-cone gauge and show that it receives a contribution that can be associated with a cusp obstruction at transverse light-cone infinity. This anomalous dimension is intimately related to expectation values composed of fields and eikonal factors along a cusped contour and is absent in covariant gauges. The implications of these findings are addressed and a modified definition of TMD PDFs is proposed.7 pages, 2 figures. Invited talk presented by the first author at International Workshop "Hadron Structure and QCD" (HSQCD'2008), June 30 - July 4, 2008, Gatchina, Russia (hsqcd.cls supplied)High Energy Physics - Phenomenologytext