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The Scalar-matter Direct Coupling and Attraction of Brans-Dicke Gravity to General Relativity

Received: 7 November 2025     Accepted: 24 November 2025     Published: 16 March 2026
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Abstract

The original Brans-Dicke scalar-tensor gravity is believed to be attracted towards General Relativity with evolution of the Universe. In the presence of explicit scalar-matter direct coupling in the Brans-Dicke gravity, however, the attractor mechanism must be reconsidered. In this paper, the master equation found by Damour and Nordtvedt is rederived. It is shown that such a generalized master equation could modify the attraction to General Relativity and the scalar-matter direct coupling may accelerate or retard it. In original Brans-Dicke scalar-tensor gravity, the agent of the attraction to General Relativity is the gravitational coupling strength. However, in the presence of the scalar-matter direct coupling, the coupling function which characterizes the coupling of scalar field to matter, makes another potential associated with coupling and it produces a new coupling parameter in the existence of the scalar-matter direct coupling, the master equation which describes the evolution of scalar field, comes to have the force term of right hand side an additional term characterizing the scalar-matter coupling, i.e. the coupling parameter is lying in parallel with the strength parameter. Therefore, the attraction mechanism represented by the strength parameter alone comes to be modified by adding the new coupling parameter. The paper considered, in detail, the friction-dominated approximation which is a case of a negligible curvature of the scalar-curvature coupling potential. Then, depending on the sign of a new coupling parameter, the evolution of scalar field is shown to accelerate the attraction or to retard it. Consequently, the attraction towards General Relativity is modified on account of the scalar-matter direct coupling.

Published in American Journal of Modern Physics (Volume 15, Issue 2)
DOI 10.11648/j.ajmp.20261502.13
Page(s) 30-35
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Brans-Dicke Gravity, General Relativity, Cosmology

References
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[3] Clemson, T., Koyama. K., Zhao, G. B., & Maartens, R. Interacting dark energy-constraints and degeneracies. Phys. Rev. D 2012, 85, 043007.
[4] Damour, T.,& Nordtvedt, K. Tensor-scalar cosmological models and their relaxation toward general relativity. Phys. Rev. D 1993, 48(8), 3436.
[5] Damour, T.,& Polyakov, A. M. The String Diaton and a Least Coupling Principle. Nucl. Phys. B 1994, 423, 532.
[6] Damour, T.,& Polyakov, A. M. String theory and Gravity. Gen. Rel. Grav. 1994, 26, 1171.
[7] Damour, T.,& Esposito-Farese, G. Tensor-multi-scalar theories of gravitation. Class. Quant. Grav. 1992, 9, 2093.
[8] Dicke, R. H. Mach’s principle and invariance under transformation of units. Phys. Rev. 1963, 125, 2163.
[9] Guo, Z-K., Ohta, N., & Tsujikawa. S. Probing coupling between dark components of the universe. Phys. Rev. D 2007, 76, 023508.
[10] Kim, J. S., & Kim, C. J. Scalar-tensor gravity with scalar-matter direct coupling and its cosmological probe. Phys. Rev. D 2017, 96, 043507.
[11] Majerotto, E., Sapone. D., & Amendola, L. Supernovae type Ia data favour coupled phantom energy. arXiv: astro-ph, 0410503.
[12] Santiago, D. I., Kalligas. D., & Wagoner, R. V. Scalar-tensor cosmologies and their late time evolution. Phys. Rev. D 1998, 58, 124005.
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  • APA Style

    Kim, J. S., Ri, S. C., Kim, I. G., Kim, R. G. (2026). The Scalar-matter Direct Coupling and Attraction of Brans-Dicke Gravity to General Relativity. American Journal of Modern Physics, 15(2), 30-35. https://doi.org/10.11648/j.ajmp.20261502.13

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    ACS Style

    Kim, J. S.; Ri, S. C.; Kim, I. G.; Kim, R. G. The Scalar-matter Direct Coupling and Attraction of Brans-Dicke Gravity to General Relativity. Am. J. Mod. Phys. 2026, 15(2), 30-35. doi: 10.11648/j.ajmp.20261502.13

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    AMA Style

    Kim JS, Ri SC, Kim IG, Kim RG. The Scalar-matter Direct Coupling and Attraction of Brans-Dicke Gravity to General Relativity. Am J Mod Phys. 2026;15(2):30-35. doi: 10.11648/j.ajmp.20261502.13

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  • @article{10.11648/j.ajmp.20261502.13,
      author = {Jik Su Kim and Song Chol Ri and Il Guk Kim and Ryong Gwang Kim},
      title = {The Scalar-matter Direct Coupling and Attraction of 
    Brans-Dicke Gravity to General Relativity},
      journal = {American Journal of Modern Physics},
      volume = {15},
      number = {2},
      pages = {30-35},
      doi = {10.11648/j.ajmp.20261502.13},
      url = {https://doi.org/10.11648/j.ajmp.20261502.13},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajmp.20261502.13},
      abstract = {The original Brans-Dicke scalar-tensor gravity is believed to be attracted towards General Relativity with evolution of the Universe. In the presence of explicit scalar-matter direct coupling in the Brans-Dicke gravity, however, the attractor mechanism must be reconsidered. In this paper, the master equation found by Damour and Nordtvedt is rederived. It is shown that such a generalized master equation could modify the attraction to General Relativity and the scalar-matter direct coupling may accelerate or retard it. In original Brans-Dicke scalar-tensor gravity, the agent of the attraction to General Relativity is the gravitational coupling strength. However, in the presence of the scalar-matter direct coupling, the coupling function which characterizes the coupling of scalar field to matter, makes another potential associated with coupling and it produces a new coupling parameter in the existence of the scalar-matter direct coupling, the master equation which describes the evolution of scalar field, comes to have the force term of right hand side an additional term characterizing the scalar-matter coupling, i.e. the coupling parameter is lying in parallel with the strength parameter. Therefore, the attraction mechanism represented by the strength parameter alone comes to be modified by adding the new coupling parameter. The paper considered, in detail, the friction-dominated approximation which is a case of a negligible curvature of the scalar-curvature coupling potential. Then, depending on the sign of a new coupling parameter, the evolution of scalar field is shown to accelerate the attraction or to retard it. Consequently, the attraction towards General Relativity is modified on account of the scalar-matter direct coupling.},
     year = {2026}
    }
    

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  • TY  - JOUR
    T1  - The Scalar-matter Direct Coupling and Attraction of 
    Brans-Dicke Gravity to General Relativity
    AU  - Jik Su Kim
    AU  - Song Chol Ri
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    AU  - Ryong Gwang Kim
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    DO  - 10.11648/j.ajmp.20261502.13
    T2  - American Journal of Modern Physics
    JF  - American Journal of Modern Physics
    JO  - American Journal of Modern Physics
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    EP  - 35
    PB  - Science Publishing Group
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    UR  - https://doi.org/10.11648/j.ajmp.20261502.13
    AB  - The original Brans-Dicke scalar-tensor gravity is believed to be attracted towards General Relativity with evolution of the Universe. In the presence of explicit scalar-matter direct coupling in the Brans-Dicke gravity, however, the attractor mechanism must be reconsidered. In this paper, the master equation found by Damour and Nordtvedt is rederived. It is shown that such a generalized master equation could modify the attraction to General Relativity and the scalar-matter direct coupling may accelerate or retard it. In original Brans-Dicke scalar-tensor gravity, the agent of the attraction to General Relativity is the gravitational coupling strength. However, in the presence of the scalar-matter direct coupling, the coupling function which characterizes the coupling of scalar field to matter, makes another potential associated with coupling and it produces a new coupling parameter in the existence of the scalar-matter direct coupling, the master equation which describes the evolution of scalar field, comes to have the force term of right hand side an additional term characterizing the scalar-matter coupling, i.e. the coupling parameter is lying in parallel with the strength parameter. Therefore, the attraction mechanism represented by the strength parameter alone comes to be modified by adding the new coupling parameter. The paper considered, in detail, the friction-dominated approximation which is a case of a negligible curvature of the scalar-curvature coupling potential. Then, depending on the sign of a new coupling parameter, the evolution of scalar field is shown to accelerate the attraction or to retard it. Consequently, the attraction towards General Relativity is modified on account of the scalar-matter direct coupling.
    VL  - 15
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