scholarly journals Gravity with Explicit Diffeomorphism Breaking

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 660
Author(s):  
Robert Bluhm ◽  
Yumu Yang
Keyword(s):  
Symmetry Breaking ◽  
Modified Theories Of Gravity ◽  
Standard Model Extension ◽  
Consistency Conditions ◽  
Spacetime Symmetry ◽  
Diffeomorphism Invariance ◽  
Model Extension ◽  
The Standard Model ◽  
Theories Of Gravity ◽  
Open Issues

Modified theories of gravity that explicitly break diffeomorphism invariance have been used for over a decade to explore open issues related to quantum gravity, dark energy, and dark matter. At the same time, the Standard-Model Extension (SME) has been widely used as a phenomenological framework in investigations of spacetime symmetry breaking. Until recently, it was thought that the SME was suitable only for theories with spontaneous spacetime symmetry breaking due to consistency conditions stemming from the Bianchi identities. However, it has recently been shown that, particularly with matter couplings included, the consistency conditions can also be satisfied in theories with explicit breaking. An overview of how this is achieved is presented, and two examples are examined. The first is massive gravity, which includes a nondynamical background tensor. The second is a model based on a low-energy limit of Hořava gravity, where spacetime has a physically preferred foliation. In both cases, bounds on matter–gravity interactions that explicitly break diffeomorphisms are obtained using the SME.

scholarly journals Is There Any Symmetry Left in Gravity Theories with Explicit Lorentz Violation?

Symmetry ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 433 ◽  
Author(s):  
Yuri Bonder ◽  
Cristóbal Corral
Keyword(s):  
Standard Model ◽  
Lorentz Violation ◽  
The Other ◽  
Standard Model Extension ◽  
Robust Algorithm ◽  
First Order ◽  
Other Hand ◽  
Model Extension ◽  
The Standard Model ◽  
Theories Of Gravity

It is well known that a theory with explicit Lorentz violation is not invariant under diffeomorphisms. On the other hand, for geometrical theories of gravity, there are alternative transformations, which can be best defined within the first-order formalism and that can be regarded as a set of improved diffeomorphisms. These symmetries are known as local translations, and among other features, they are Lorentz covariant off shell. It is thus interesting to study if theories with explicit Lorentz violation are invariant under local translations. In this work, an example of such a theory, known as the minimal gravity sector of the Standard Model Extension, is analyzed. Using a robust algorithm, it is shown that local translations are not a symmetry of the theory. It remains to be seen if local translations are spontaneously broken under spontaneous Lorentz violation, which are regarded as a more natural alternative when spacetime is dynamic.

scholarly journals D-oscillons in the standard model extension

2015 ◽  
Vol 91 (12) ◽  
Author(s):  
R. A. C. Correa ◽  
Roldão da Rocha ◽  
A. de Souza Dutra
Keyword(s):  
Standard Model ◽  
Standard Model Extension ◽  
Model Extension ◽  
The Standard Model

scholarly journals Lorentz Violation of the Photon Sector in Field Theory Models

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lingli Zhou ◽  
Bo-Qiang Ma
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Degrees Of Freedom ◽  
Lorentz Violation ◽  
Detailed Structure ◽  
Standard Model Extension ◽  
Model Extension ◽  
The Standard Model ◽  
Minimal Standard

We compare the Lorentz violation terms of the pure photon sector between two field theory models, namely, the minimal standard model extension (SME) and the standard model supplement (SMS). From the requirement of the identity of the intersection for the two models, we find that the free photon sector of the SMS can be a subset of the photon sector of the minimal SME. We not only obtain some relations between the SME parameters but also get some constraints on the SMS parameters from the SME parameters. The CPT-odd coefficients(kAF)αof the SME are predicted to be zero. There are 15 degrees of freedom in the Lorentz violation matrixΔαβof free photons of the SMS related with the same number of degrees of freedom in the tensor coefficients(kF)αβμν, which are independent from each other in the minimal SME but are interrelated in the intersection of the SMS and the minimal SME. With the related degrees of freedom, we obtain the conservative constraints(2σ)on the elements of the photon Lorentz violation matrix. The detailed structure of the photon Lorentz violation matrix suggests some applications to the Lorentz violation experiments for photons.

scholarly journals Effects of Lorentz violation through the γe → Wνe process in the Standard Model extension

2014 ◽  
Vol 41 (5) ◽  
pp. 055003 ◽  
Author(s):  
J I Aranda ◽  
F Ramírez-Zavaleta ◽  
D A Rosete ◽  
F J Tlachino ◽  
J J Toscano ◽  
...  
Keyword(s):  
Standard Model ◽  
Lorentz Violation ◽  
Standard Model Extension ◽  
Model Extension ◽  
The Standard Model
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