The Physics and Astronomy Classification Scheme® (PACS) was developed by the American Institute of Physics (AIP) and has been used in Physical Review since 1975 to identify fields and sub-fields of physics. PACS is a hierarchical partitioning of the whole spectrum of subject matter in physics, astronomy, and related sciences.
Further information is available on AIP's main PACS website. Please note that PACS is no longer being maintained; the most recent PACS scheme is from 2010 and is available at https://publishing.aip.org/publishing/pacs/pacs-2010-regular-edition. An alphabetical index is also available at https://publishing.aip.org/publishing/pacs/pacs-alphabetical-index
APS now has a new classification scheme for physics, PhySH - Physics Subject Headings, which replaced PACS. With the transition to PhySH, authors will no longer need to provide PACS.
Please note that earlier versions of PACS are no longer available on this website. Kindly contact help@aps.org with any questions.