Screening Mechanisms on White Dwarfs: Symmetron and Dilaton
This work provides the first comparison of the symmetron and dilaton fields in white dwarfs. We show how these screening mechanisms behave inside such stars and their impact on stellar properties. Employing a custom-developed shooting method, we solve the scalar–tensor equilibrium equations in the N...
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2025-05-01
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| author | Joan Bachs-Esteban Ilídio Lopes Javier Rubio |
| author_facet | Joan Bachs-Esteban Ilídio Lopes Javier Rubio |
| author_sort | Joan Bachs-Esteban |
| collection | DOAJ |
| description | This work provides the first comparison of the symmetron and dilaton fields in white dwarfs. We show how these screening mechanisms behave inside such stars and their impact on stellar properties. Employing a custom-developed shooting method, we solve the scalar–tensor equilibrium equations in the Newtonian approximation. We consider a Chandrasekhar equation of state and examine a range of potential mass scales and coupling strengths for both fields. Both fields enhance the pressure drop in low-density white dwarfs, leading to smaller stellar masses, radii, and luminosities. Unlike chameleon models, their effects are suppressed in more massive stars, with symmetron fields fully decoupling and dilaton fields weakening but not vanishing. Consequently, no mass–radius curve for screened white dwarfs exceeds the Newtonian prediction in any of these three mechanisms. The mass–radius deviations are generally more pronounced at lower densities, depending on model parameters. Due to their common runaway potential, we confirm that dilaton and chameleon fields display similar field and gradient profiles. In contrast, due to their environment-dependent coupling, the dilaton and symmetron mechanisms exhibit stronger density-dependent screening effects. These findings highlight both phenomenological differences and theoretical similarities among these mechanisms, motivating asteroseismology studies to constrain the symmetron and dilaton parameter spaces. |
| format | Article |
| id | doaj-art-d1bbf479430549fd8881ca4da32bbd32 |
| institution | Kabale University |
| issn | 2218-1997 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | MDPI AG |
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| series | Universe |
| spelling | doaj-art-d1bbf479430549fd8881ca4da32bbd322025-08-20T03:47:58ZengMDPI AGUniverse2218-19972025-05-0111515810.3390/universe11050158Screening Mechanisms on White Dwarfs: Symmetron and DilatonJoan Bachs-Esteban0Ilídio Lopes1Javier Rubio2Centro de Astrofísica e Gravitação—CENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL, Av. Rovisco Pais 1, 1049-001 Lisboa, PortugalCentro de Astrofísica e Gravitação—CENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL, Av. Rovisco Pais 1, 1049-001 Lisboa, PortugalDepartamento de Física Teórica and Instituto de Física de Partículas y del Cosmos (IPARCOS), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, SpainThis work provides the first comparison of the symmetron and dilaton fields in white dwarfs. We show how these screening mechanisms behave inside such stars and their impact on stellar properties. Employing a custom-developed shooting method, we solve the scalar–tensor equilibrium equations in the Newtonian approximation. We consider a Chandrasekhar equation of state and examine a range of potential mass scales and coupling strengths for both fields. Both fields enhance the pressure drop in low-density white dwarfs, leading to smaller stellar masses, radii, and luminosities. Unlike chameleon models, their effects are suppressed in more massive stars, with symmetron fields fully decoupling and dilaton fields weakening but not vanishing. Consequently, no mass–radius curve for screened white dwarfs exceeds the Newtonian prediction in any of these three mechanisms. The mass–radius deviations are generally more pronounced at lower densities, depending on model parameters. Due to their common runaway potential, we confirm that dilaton and chameleon fields display similar field and gradient profiles. In contrast, due to their environment-dependent coupling, the dilaton and symmetron mechanisms exhibit stronger density-dependent screening effects. These findings highlight both phenomenological differences and theoretical similarities among these mechanisms, motivating asteroseismology studies to constrain the symmetron and dilaton parameter spaces.https://www.mdpi.com/2218-1997/11/5/158scalar–tensor theoriesscreening mechanismswhite dwarfs |
| spellingShingle | Joan Bachs-Esteban Ilídio Lopes Javier Rubio Screening Mechanisms on White Dwarfs: Symmetron and Dilaton Universe scalar–tensor theories screening mechanisms white dwarfs |
| title | Screening Mechanisms on White Dwarfs: Symmetron and Dilaton |
| title_full | Screening Mechanisms on White Dwarfs: Symmetron and Dilaton |
| title_fullStr | Screening Mechanisms on White Dwarfs: Symmetron and Dilaton |
| title_full_unstemmed | Screening Mechanisms on White Dwarfs: Symmetron and Dilaton |
| title_short | Screening Mechanisms on White Dwarfs: Symmetron and Dilaton |
| title_sort | screening mechanisms on white dwarfs symmetron and dilaton |
| topic | scalar–tensor theories screening mechanisms white dwarfs |
| url | https://www.mdpi.com/2218-1997/11/5/158 |
| work_keys_str_mv | AT joanbachsesteban screeningmechanismsonwhitedwarfssymmetronanddilaton AT ilidiolopes screeningmechanismsonwhitedwarfssymmetronanddilaton AT javierrubio screeningmechanismsonwhitedwarfssymmetronanddilaton |