The relativistic center of mass in field theory with spin

Abstract

In order to unravel the origin of the nucleon spin, one has to study in detail the question of orbital angular momentum, and in particular the reference point about which it is defined. With this in mind, we review the concept of relativistic center of mass, generalize the discussion to the case of asymmetric energy-momentum tensors, and establish the link with the light-front formalism. We find that the $p$-wave in the Dirac plane-wave solutions arises from a relativistic quantum-mechanical effect which forces the canonical reference point to depend on the observer. This explains why longitudinal spin is much simpler to study than transverse spin. It is also the reason behind the observation of induced shifts and distortions in the parton distributions defined within the light-front formalism.

41 pages, 1 figure, version accepted in EPJC

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Cited by in corpus (31)

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• Gravitational form factors of light mesons
• Covariant multipole expansion of local currents for massive states of any spin
• The energy-momentum tensor of spin-1 hadrons: formalism
• Angular momentum and generalized parton distributions for the proton with basis light-front quantization
• Gravitational form factors of the baryon octet with flavor SU(3) symmetry breaking
• Poincaré constraints on the gravitational form factors for massive states with arbitrary spin
• Nucleon relativistic polarization and magnetization distributions
• Relativistic spin sum rules and the role of the pivot
• Universality of the Poincaré gravitational form factor constraints
• On the deuteron relativistic charge distributions
• Spatial densities of momentum and forces in spin-one hadrons
• Electromagnetic multipole structure of a spin-one particle: Abel tomography case
• The spin alignment of vector mesons with light front quarks
• Stress out of charmonia
• Relativistic energy-momentum tensor distributions in a polarized nucleon
• Two-dimensional charge distributions of the $\Delta$ baryon: Interpolation between the nonrelativistic and ultrarelativistic limit
• Medium modification of the nucleon mechanical properties: Abel tomography case
• Six-dimensional light-front Wigner distribution of hadrons
• Potential linear and angular momentum in the scalar diquark model
• Mapping the transverse spin sum rule in position space
• Zero curvature is a necessary and sufficient condition for a spin-orbital decomposition
• Energy-momentum tensor in QCD: nucleon mass decomposition and mechanical equilibrium
• Energy, angular momentum and pressure force distributions inside nucleons
• Energy-momentum tensor of the nucleon on the light front: Abel tomography case
• Spin operators and representations of the Poincaré group
• Transverse energy-momentum tensor distributions in polarized nucleons
• A Quasigroup Approach for Conservation Laws in Asymptotically Flat Spacetimes