Schwinger's proper time and worldline holographic renormalisation
  Worldline holography states that within the framework of the worldline approach to quantum field theory, sources of a quantum field theory over Mink$_4$ naturally form a field theory over AdS$_5$ {\sl to all orders} in the elementary fields and in the sources of arbitrary spin. (Such correspondences are also available for other pairs of spacetimes, not only Mink$_4\leftrightarrow\mathrm{AdS}_5$.) Schwinger's proper time of the worldline formalism is automatically grouped with the physical four spacetime dimensions into an AdS$_5$ geometry. We show that the worldline holographic effective action in general and the proper-time profiles of the sources in particular solve a renormalisation group equation and, reversely, can be defined as solution to the latter. This fact also ensures regulator independence. 
Dennis D. Dietrich and Adrian Koenigstein
hep-th hep-ph nucl-th