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1. Mechanical properties of particles

   https://doi.org/10.22323/1.346.0066  

   Polyakov, Maxim; Schweitzer, Peter (August 2019, 23rd International Symposium on Spin Physics (SPIN 2018))

   Selected topics related to the physics of the energy-momentum tensor (EMT) form factors are discussed. The topics are: 1) Fundamental mechanical properties of particles and gravity 2) Mechanical properties of non-spherical particles 3) Gravitational form factors of Goldstone bosons 4) Nucleon's seismology? 

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2. Energy-momentum tensor in Φ**4 theory at one loop

   https://doi.org/10.1103/PhysRevD.111.076001  

   Maynard, Brean (April 2025, Physical Review D)

   The energy-momentum tensor form factors are studied in Φ**4 to one-loop order with particular focus on the D-term, a particle property which has attracted a lot of attention in the recent literature. It is shown that the free Klein-Gordon theory value of D = -1 is reduced to D = − 1/3 even if the Φ**4 interaction is infinitesimally small. A companion work in Φ**3 theory confirms this result which may indicate that it is independent of the type of interaction as long as the scalar theory is renormalizable. Dispersion relations are studied. Various definitions of mean square radii including the mechanical radius are investigated. The findings contribute to a better understanding of the energy momentum tensor properties of particles and their interpretation. 

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3. Mass sum rules of the electron in quantum electrodynamics

   https://doi.org/10.1007/JHEP09(2020)067  

   Rodini, S.; Metz, A.; Pasquini, B. (September 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract Different decompositions of the nucleon mass, in terms of the masses and energies of the underlying constituents, have been proposed in the literature. We explore the corresponding sum rules in quantum electrodynamics for an electron at one-loop order in perturbation theory. To this aim we compute the form factors of the energy-momentum tensor, by paying particular attention to the renormalization of ultraviolet divergences, operator mixing and scheme dependence. We clarify the expressions of all the proposed sum rules in the electron rest frame in terms of renormalized operators. Furthermore, we consider the same sum rules in a moving frame, where they become energy decompositions. Finally, we discuss some implications of our study on the mass sum rules for the nucleon. 

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4. On Sugawara construction on celestial sphere

   https://doi.org/10.1007/JHEP09(2020)139  

   Fan, Wei; Fotopoulos, Angelos; Stieberger, Stephan; Taylor, Tomasz R. (September 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract Conformally soft gluons are conserved currents of the Celestial Conformal Field Theory (CCFT) and generate a Kac-Moody algebra. We study celestial amplitudes of Yang-Mills theory, which are Mellin transforms of gluon amplitudes and take the double soft limit of a pair of gluons. In this manner we construct the Sugawara energy-momentum tensor of the CCFT. We verify that conformally soft gauge bosons are Virasoro primaries of the CCFT under the Sugawara energy-momentum tensor. The Sugawara tensor though does not generate the correct conformal transformations for hard states. In Einstein-Yang- Mills theory, we consider an alternative construction of the energy-momentum tensor, similar to the double copy construction which relates gauge theory amplitudes with gravity ones. This energy momentum tensor has the correct properties to generate conformal transformations for both soft and hard states. We extend this construction to supertranslations. 

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5. Pressure Inside Hadrons: Criticism, Conjectures, and All That

   https://doi.org/10.5506/APhysPolB.56.3-A17  

   Lorcé, Cédric; Schweitzer, Peter (March 2025, Acta Physica Polonica B)

   Eides, M; Praszalowicz, M; Strakovsky, I (Ed.)

   The interpretation of the energy-momentum tensor form factor D(t) of hadrons in terms of pressure and shear force distributions is discussed, concerns raised in the literature are reviewed, and ways to reconcile the concerns with the interpretation are indicated. 

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