Journal: Fortschritte der Physik

Abbreviation

Fortschr. Phys.

Publisher

Wiley-VCH

Journal Volumes

ISSN

0015-8208
1521-3978

Description

Filters

2023 - 20253
Reset filters

Search Results

Publications 1 - 3 of 3
  • Hamiltonian Analysis of f (ℚ) Gravity and the Failure of the Dirac–Bergmann Algorithm for Teleparallel Theories of Gravity
    Item type: Journal Article
    D'Ambrosio, Fabio; Heisenberg, Lavinia; Zentarra, Stefan (2023)
    Fortschritte der Physik
    In recent years,f (Q) gravity has enjoyed considerable attention in the literature and important results have been obtained. However, the question of how many physical degrees of freedom the theory propagates-and how this number may depend on the form of the function f-has not been answered satisfactorily. In this article it is shown that a Hamiltonian analysis based on the Dirac-Bergmann algorithm-one of the standard methods to address this type of question-fails. The source of the failure is isolated and it is shown that other commonly considered teleparallel theories of gravity are affected by the same problem. Furthermore, it is pointed out that the number of degrees of freedom obtained in Phys. Rev. D 106 no. 4, (2022) by K. Hu, T. Katsuragawa, and T. Qui (namely eight), based on the Dirac-Bergmann algorithm, is wrong. Using a different approach, it is shown that the upper bound on the degrees of freedom is seven. Finally, a more promising strategy for settling this important question is proposed.
  • On the Dark-Energy Enigma
    Item type: Journal Article
    Chamseddine, Ali H.; Fröhlich, Jürg (2025)
    Fortschritte der Physik
    A model is presented that provides an explanation for the presence of (Dark Matter and) Dark Energy in the universe. A key idea is to express the volume form of the Lorentzian metric on space–time in terms of a positive function of a new scalar field multiplying a certain four-form given by the wedge product of the differential of the mimetic scalar field and a certain closed three-form. An ansatz for this three-form related to one commonly used to determine the winding number of a map from a three-dimensional hypersurface to a three-sphere is discussed. An action functional depending on the space–time metric, the new scalar field, the mimetic scalar and the three-form is proposed, and the field equations are derived. Special solutions of these equations for a Friedmann–Lemaître universe are presented.
  • Double Copy From Tensor Products of Metric BV■-Algebras
    Item type: Journal Article
    Borsten, Leron; Jurčo, Branislav; Kim, Hyungrok; et al. (2025)
    Fortschritte der Physik
    Field theories with kinematic Lie algebras, such as field theories featuring color–kinematics duality, possess an underlying algebraic structure known as BV■-algebra. If, additionally, matter fields are present, this structure is supplemented by a module for the BV■-algebra. The authors explain this perspective, expanding on our previous work and providing many additional mathematical details. The authors also show how the tensor product of two metric BV■-algebras yields the action of a new syngamy field theory, a construction which comprises the familiar double copy construction. As examples, the authors discuss various scalar field theories, Chern–Simons theory, self-dual Yang–Mills theory, and the pure spinor formulations of both M2-brane models and supersymmetric Yang–Mills theory. The latter leads to a new cubic pure spinor action for 10-dimensional supergravity. A homotopy-algebraic perspective on colour–flavour-stripping is also given, obtain a new restricted tensor product over a wide class of bialgebras, and it is also show that any field theory (even one without colour–kinematics duality) comes with a kinematic L∞-algebra.
Publications 1 - 3 of 3