Thermodynamics of FLRW universe in quadratic gravity
International Journal of Geometric Methods in Modern Physics, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Basım Tarihi: 2026
- Doi Numarası: 10.1142/s0219887826503482
- Dergi Adı: International Journal of Geometric Methods in Modern Physics
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, MathSciNet, zbMATH, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO), Technology Collection (ProQuest)
- Anahtar Kelimeler: apparent horizon, FLRW universe, generalized Misner–Sharp energy, horizon thermodynamics, phase transitions, Quadratic gravity
- Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
- Kocaeli Üniversitesi Adresli: Evet
Özet
In this paper, we investigate the thermodynamic aspects of quadratic gravity in a D-dimensional Friedmann–Lemaître–Robertson–Walker (FLRW) universe. First, we derive the field equations and the effective energy–momentum tensor for quadratic gravity. Then, using these equations, we obtain the generalized Misner–Sharp energy within the framework of this model. We consider the thermodynamic behavior of the apparent horizon and derive the equations of state related to the pressure, temperature, and radius of the apparent horizon. By using the thermodynamic pressure, we obtain the critical points corresponding to phase transitions. We determine the critical temperature and critical radius in terms of model parameters, including the quadratic coupling and the cosmological constant. We also examine key thermodynamic quantities, such as Wald entropy, specific heat at constant pressure, enthalpy, Gibbs free energy. By examining the behavior of these quantities, we can gain insight into the thermodynamic stability of the quadratic gravity model. In particular, we find that quadratic terms change the stability conditions and can lead to new thermodynamic behaviors compared to general relativity.