Department of Theoretical Physics

National Institute of Physics and Nuclear Engineering - Horia Hulubei

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Tachyons and reheating in a braneworld inflationary scenario

Goran Djordjevic, University of Nis



We introduce the inflationary scenario based on the tachyon field coupled with and without the radion of the second Randall-Sundrum model (RSII). The tachyon Lagrangian is derived from the dynamics of a 3-brane moving in the 4+1 dimensional bulk, i.e. with one extra dimension. Varying the free parameters and initial conditions we confront our numerical results with the Planck 2015 data.
We also consider the RSII model extended to more general warp functions, i.e. with a self-interacting scalar field. It leads to modification of the scale dependent four-dimensional gravitational constant. We study a power law warp factor which generates an inverse power-law potential of the tachyon field . We find a critical power that divides two subclasses with distinct asymptotic behaviors.
Further, we present a study of the cosmological particle creation in the RSII model extended to include matter in the bulk. The presence of matter modifies the warp factor with two effects: a modification of the RSII cosmology and a modification of the tachyon potential. It is briefly demonstrated how the interaction of the tachyon with the U(1) gauge field drives cosmological creation of massless particles and estimate the resulting reheating at the end of inflation.
We conclude with the indications obtained from new numerical results of the RSII extended model, suggestions for a general ``algorithm`` for calculation of the observational parameters for a wide class of tachyonic potentials, including a holographic braneworld universe.

References: 1. N. Bilic, D, Dimitrijevic, G. Djordjevic, M. Milosevic, IJMPA 32 (2017) No. 05, 1750039; arXiv:1607.04524 [gr-qc]
2. M. Milosevic, D. D. Dimitrijevic, G. S. Djordjevic and M. D. Stojanovic SAJ 92 (2016) 1-8, DOI: 10.2298/SAJ160312003M
3. N. Bilic, S. Domazet and G. S. Djordjevic, Class. Quantum Grav. 34 (2017) 165006; arXiv:1704.01072 [gr-qc]
4. N. Bilic, S. Domazet and G. S. Djordjevic, Phys. Rev. D 96, 083518 (2017); arXiv:1707.06023 [hep-th]



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