Thesis

Astrophysical and cosmological applications of modified theories of gravity

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domains:

  General Relativity | Cosmology

• Supervisor:

  José Sande Lemos

• Co-Supervisor:

  Francisco Lobo

• Institution:

  Instituto Superior Técnico

• Host Institution:

  Instituto Superior Técnico

• Abstract:

  The late-time cosmic accelerated expansion is one of the most important and challenging current problems in cosmology. Although the standard model of cosmology has favored the dark energy models as fundamental candidates responsible for the cosmic expansion, the latter may be due to modifications of General Relativity, which introduce new degrees of freedom to the gravitational sector itself. This research project will explore the viability of a plethora of modified gravity models, consistently analyzing the reproduction of all the cosmological epochs. More specifically, we will consider generalizations of the Einstein-Hilbert action by including quadratic Lagrangians, involving second order curvature invariants, such as Lagrangians involving non-linear curvature invariants, such as, modified Gauss-Bonnet theories, Lovelock theories, or Lagrangians which in addition to higher-order curvature terms also include couplings to the matter sector. Another class of theories under our scrutiny will be generalized scalar-tensor or vector-tensor gravity theories, where scalar or vector fields play gravitational roles that can also be perceived as couplings to matter in an appropriate frame. Additionally, another fundamental goal is to study the theoretical issues of the extra degrees of freedom of the theory and finally astrophysical applications, such as in black hole physics, in all of these classes of modified gravity will also be analyzed. References: [1] S. Perlmutter et al. [Supernova Cosmology Project Collaboration], Astrophys. J. 517, 565 (1999). [2] A.G. Riess et al. [Supernova Search Team Collaboration], Astron. J. 116, 1009 (1998). [3] R. Maartens, Living Rev. Rel. 7, 7 (2004). [4] G.R. Dvali, G. Gabadadze and M. Porrati, Phys. Lett. B 485, 208 (2000). [5] T.P. Sotiriou and V. Faraoni, Rev. Mod. Phys. 82, 451 (2010); [6] A. De Felice and S. Tsujikawa, Livinging Rev. Rel. 13, 3 (2010); [7] S. Capozziello and M. De Laurentis, Phys. Rept. 509, 167 (2011). [8] S. Nojiri and S.D. Odintsov, Phys. Rept. 505, 59 (2011). [9] S.M. Carroll, V. Duvvuri, M. Trodden and M.S. Turner, Phys. Rev. D 70, 043528 (2004). [10] A.B. Balakin, V.V. Bochkarev, J.P.S. Lemos, Phys. Rev. D 85, 064015 (2012). [11] L. Amendola et al. [Euclid Theory Working Group Collaboration], Living Rev. Rel. 16, 6 (2013). [12] C. de Rham, Living Rev. Rel. 17, 7 (2014). [13] G.W. Horndeski, Int. J. Theor. Phys., 10, 363 (1974). [14] M.S. Volkov, Class. Quant. Grav. 30, 184009 (2013). [15] T.P. Sotiriou and S. Liberati, Annals Phys. 322, 935 (2007). [16] R. Ferraro and F. Fiorini, Phys. Rev. D 75, 084031 (2007). [17] E.V. Linder, Phys. Rev. D 81, 127301 (2010). [18] T. Harko, F.S.N. Lobo, G. Otalora and E.N. Saridakis, Phys.Rev. D 89, 124036, (2014). [19] Y.-F. Cai, S.-H. Chen, J.B. Dent, S. Dutta and E.N. Saridakis, Class. Quant. Grav. 28, 215011 (2011). [20] H. van Dam, M. Veltman, Nucl. Phys. B22, 397 411 (1970); V. Zakharov, JETP Lett. 12, 312 (1970). [21] W. J. Percival, et al, Mon. Not. Roy. Astron. Soc. 381, 1053 (2007). [22] J. E. Lidsey et al, Rev. Mod. Phys. 69 373 (1997). [23] E.J. Copeland, M. Sami and S. Tsujikawa, Int. J. Mod. Phys. D 15, 1753 (2006).