{"title":"f(R,T2)重力下无奇点宇宙的动力学","authors":"I. Hashim , M. Sharif , M. Zeeshan Gul","doi":"10.1016/j.hedp.2025.101223","DOIUrl":null,"url":null,"abstract":"<div><div>This study investigates bouncing cosmological solutions to understand cosmic evolution in the background of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> theory, where <span><math><mi>R</mi></math></span> denotes the Ricci scalar and <span><math><mrow><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><msup><mrow><mi>T</mi></mrow><mrow><mi>ξ</mi><mi>η</mi></mrow></msup><msub><mrow><mi>T</mi></mrow><mrow><mi>ξ</mi><mi>η</mi></mrow></msub></mrow></math></span> is the self-contraction of the stress energy tensor. For this purpose, we analyze a flat Friedmann–Robertson–Walker spacetime with perfect matter distribution and assume a specific functional form of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> theory to explore the effects of modified gravity on cosmic dynamics. Further, we evaluate super bounce and exponential bounce models to investigate the non-singular universe in this framework. The positive behavior of energy density and the negative behavior of pressure, as well as null energy condition ensure the existence of a viable cosmological bounce solutions. The equation of state parameter indicates the phantom region corresponding to the super bounce model and the quintessence era for exponential bounce model, indicating that the universe experiences cosmic acceleration. The stability of the obtained solutions is analyzed through linear perturbation, demonstrating the model’s robustness against small fluctuations and confirming its validity as a framework for understanding cosmic evolution. Our findings suggest that this modified gravitational theory provides an alternative framework to standard cosmology, offering insights into gravitational interactions and the early cosmic evolution.</div></div>","PeriodicalId":49267,"journal":{"name":"High Energy Density Physics","volume":"57 ","pages":"Article 101223"},"PeriodicalIF":0.9000,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Dynamics of a singularity-free universe in f(R,T2) Gravity\",\"authors\":\"I. Hashim , M. Sharif , M. Zeeshan Gul\",\"doi\":\"10.1016/j.hedp.2025.101223\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>This study investigates bouncing cosmological solutions to understand cosmic evolution in the background of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> theory, where <span><math><mi>R</mi></math></span> denotes the Ricci scalar and <span><math><mrow><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><msup><mrow><mi>T</mi></mrow><mrow><mi>ξ</mi><mi>η</mi></mrow></msup><msub><mrow><mi>T</mi></mrow><mrow><mi>ξ</mi><mi>η</mi></mrow></msub></mrow></math></span> is the self-contraction of the stress energy tensor. For this purpose, we analyze a flat Friedmann–Robertson–Walker spacetime with perfect matter distribution and assume a specific functional form of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><msup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> theory to explore the effects of modified gravity on cosmic dynamics. Further, we evaluate super bounce and exponential bounce models to investigate the non-singular universe in this framework. The positive behavior of energy density and the negative behavior of pressure, as well as null energy condition ensure the existence of a viable cosmological bounce solutions. The equation of state parameter indicates the phantom region corresponding to the super bounce model and the quintessence era for exponential bounce model, indicating that the universe experiences cosmic acceleration. The stability of the obtained solutions is analyzed through linear perturbation, demonstrating the model’s robustness against small fluctuations and confirming its validity as a framework for understanding cosmic evolution. Our findings suggest that this modified gravitational theory provides an alternative framework to standard cosmology, offering insights into gravitational interactions and the early cosmic evolution.</div></div>\",\"PeriodicalId\":49267,\"journal\":{\"name\":\"High Energy Density Physics\",\"volume\":\"57 \",\"pages\":\"Article 101223\"},\"PeriodicalIF\":0.9000,\"publicationDate\":\"2025-08-23\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"High Energy Density Physics\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1574181825000515\",\"RegionNum\":3,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"PHYSICS, FLUIDS & PLASMAS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"High Energy Density Physics","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1574181825000515","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"PHYSICS, FLUIDS & PLASMAS","Score":null,"Total":0}
Dynamics of a singularity-free universe in f(R,T2) Gravity
This study investigates bouncing cosmological solutions to understand cosmic evolution in the background of theory, where denotes the Ricci scalar and is the self-contraction of the stress energy tensor. For this purpose, we analyze a flat Friedmann–Robertson–Walker spacetime with perfect matter distribution and assume a specific functional form of theory to explore the effects of modified gravity on cosmic dynamics. Further, we evaluate super bounce and exponential bounce models to investigate the non-singular universe in this framework. The positive behavior of energy density and the negative behavior of pressure, as well as null energy condition ensure the existence of a viable cosmological bounce solutions. The equation of state parameter indicates the phantom region corresponding to the super bounce model and the quintessence era for exponential bounce model, indicating that the universe experiences cosmic acceleration. The stability of the obtained solutions is analyzed through linear perturbation, demonstrating the model’s robustness against small fluctuations and confirming its validity as a framework for understanding cosmic evolution. Our findings suggest that this modified gravitational theory provides an alternative framework to standard cosmology, offering insights into gravitational interactions and the early cosmic evolution.
期刊介绍:
High Energy Density Physics is an international journal covering original experimental and related theoretical work studying the physics of matter and radiation under extreme conditions. ''High energy density'' is understood to be an energy density exceeding about 1011 J/m3. The editors and the publisher are committed to provide this fast-growing community with a dedicated high quality channel to distribute their original findings.
Papers suitable for publication in this journal cover topics in both the warm and hot dense matter regimes, such as laboratory studies relevant to non-LTE kinetics at extreme conditions, planetary interiors, astrophysical phenomena, inertial fusion and includes studies of, for example, material properties and both stable and unstable hydrodynamics. Developments in associated theoretical areas, for example the modelling of strongly coupled, partially degenerate and relativistic plasmas, are also covered.