Energy-Momentum Relocalization, Surface Terms, and Massless Poles in Axial Current Matrix Elements

• Main Author: Oleg Teryaev
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Symmetry
• Subjects: gravity; relocalization; topology; boundary; poles
• Online Access: https://www.mdpi.com/2073-8994/12/9/1409

The energy-momentum relocalization in classical and quantum theory is addressed with<br />specific impact on non-perturbative QCD and hadronic structure. The relocalization is manifested in<br />the existence of canonical and symmetric (Belinfante and Hilbert) energy momentum tensors (EMT).<br />The latter describes the interactions of hadrons with classical gravity and inertia. Canonical EMT,<br />in turn, is naturally emerging due to the translation invariance symmetry and appears when spin<br />structure of hadrons is considered. Its relation to symmetric Hilbert and Belinfante EMTs requires<br />the possibility to neglect the contribution of boundary terms for the classical fields. For the case of<br />quantum fields this property corresponds to the absence of zero-momentum poles of matrix element<br />of the axial current dual to the spin density. This property is satisfied for quarks manifesting the<br />symmetry counterpart of <em>U_A(1)</em> problem and may be violated for gluons due to QCD ghost pole.