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Nuclear Theory·nucl-th

Thursday·July 23, 2026

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 05

    [Submitted on 22 Jul 2026] (cross-list from hep-lat)

    Nucleon unpolarized second Mellin moments using lattice QCD ensembles with physical quark masses and in the continuum limit

    Constantia Alexandrou (University of Cyprus and The Cyprus Institute)🇨🇾 · Simone Bacchio (The Cyprus Institute)🇨🇾 · Jacob Finkenrath (University of Wuppertal)🇩🇪 · Christos Iona (University of Cyprus and The Cyprus Institute)🇨🇾 · Giannis Koutsou (The Cyprus Institute)🇨🇾 · Christian Kummer (University of Cyprus and Technical University of Berlin)🇨🇾 · Yan Li (The Cyprus Institute)🇨🇾 · Bhavna Prasad (The Cyprus Institute)🇨🇾 · Gregoris Spanoudes (University of Cyprus)🇨🇾

    We compute the matrix elements of the energy-momentum tensor of the nucleon using four ensembles of twisted mass clover-improved fermions with the up, down, strange and charm quark masses tuned to approximately their physical values. The four ensembles have similar physical volume and lattice spacings ~fm, ~fm, ~fm, and fm, allowing us to take the continuum limit directly at the physical pion mass point. We compute both connected and disconnected quark contributions as well as gluon contributions. All renormalization functions, including the mixing of the quark singlet with the gluon, are determined non-perturbatively. We extract the gravitational form factors in the continuum limit at and evaluate the contribution of quarks and gluons to the momentum and angular momentum of the proton. Using the values of the intrinsic quark spin computed using the same gauge ensembles we also determine the orbital angular momentum for each quark flavor.

    Comments:
    33 pages, 34 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2607.20337 [pdf]
    1 citation
  2. 06

    [Submitted on 22 Jul 2026] (cross-list from cond-mat.quant-gas)

    Fermionic pairs, from the surface to the bulk

    Sandra Brandstetter · Carl Heintze · Fabian Brauneis · Stephanie M. Reimann · Georg Bruun · Maciej Gałka · Selim Jochim

    Fermion pairing underlies collective quantum phenomena across widely different forms of matter. In extended systems such as ultracold Fermi gases, pairing is commonly understood through the BCS--BEC crossover, where the pair size evolves from large, overlapping Cooper pairs to tightly bound dimers. In finite systems such as atomic nuclei, superconducting grains and quantum dots, however, the same pairing tendency competes with confinement, shell filling and spatial inhomogeneity, making the microscopic structure of pairs much harder to access. Here, we image pair correlations in a finite, tunable system of few fermionic atoms with single-particle resolution and full counting statistics. We observe that confinement and shell structure re-organize pairing in real space: In the weakly interacting, confinement-dominated regime, closed-shell configurations suppress correlations in the high-density trap center. Pairing is mainly observed toward the low-density surface. Open-shell systems, however, support substantially stronger central pairing. Already for surprisingly small systems, increasing either interaction strength or particle number restores a locally bulk-like Cooper-pair profile in the trap center, whereas the edge retains dimer-like correlations. By resolving where pairs form and how their character changes from localized dimers to overlapping Cooper pairs, our measurements provide a microscopic view of pairing in finite fermionic matter and connect the physics of mesoscopic cold atoms to pairing phenomena in nuclei and superconducting nanostructures.

    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2607.20412 [pdf]
    0 citations

Affiliations

first authorsco-authorsvia INSPIRE