arXiv subjects

Marko Stojanovic

Publications and source records attributed to Marko Stojanovic.

6 recordsLinked to original sources

arXiv2026

Analytical calculation of the observational parameters for tachyon inflation

We investigate the possibility of analytically calculating observational parameters in tachyon inflation cosmology, using the Hubble expansion rate as a function of the tachyon field. First, in light of the newer Planck results, we analyze previous investigations in which the test Hubble rate functions were confronted with Planck 2013 data. We propose and analyze a number of new test Hubble rate functions, finding considerable improvement and approaching reasonable agreement with recent observational data. For a class of these functions, we were able to carry out analytical calculations. As a novelty, we introduce a functional dependence of the slow-roll Hubble flow parameters as an input, which facilitates an analytical study of inflation. In this way, we obtain explicit expressions for the scalar spectral index ($n_{\rm s}$) and the tensor-to-scalar ratio ($r$). We confront our analytical and numerical predictions with Planck observational constraints. Finally, we discuss the proposed linear dependence between the first two slow-roll parameters in light of recent data from ACT DR6, DESI, and others, as well as the potential to generalize this dependence to other inflation models.

gr-qc↗

arXiv2024

General Expressions for $n_{\rm s}$ and $r$ for Several Minimally Coupled Single Scalar Field Models

We derive a generalized expressions for the scalar power spectrum and the observational parameters of inflation (the scalar spectral index $n_{\rm s}$ and the tensor-to-scalar ratio $r$) for several single field scalar models minimally coupled with gravity. We work in the framework where the perturbed Einstein equations, at linear order, are of the same form to those obtained in the standard \textit{k}-inflation, with generalized form of the pump field $z$. By generalizing the expressions for $z$ and the speed of sound squared $c_{\rm s}^2$, using the slow-roll approximation, we calculate $n_{\rm s}$ and $r$ up to the second order in the Hubble flow parameters.

gr-qc↗

arXiv2024

On attractor behavior in braneworld constant-roll inflation

We investigate in detail the attractor behavior of some inflationary models based on braneworld dynamics under the constant-roll condition. We describe the dynamics of the models, assuming that the second slow-roll parameter remains constant during inflation. We show that the dynamics of the considered models have the property of a cosmological attractor.

gr-qc↗

arXiv2023

Constant-roll inflation with tachyon field in the holographic braneworld

We study inflation driven by the tachyon field in the holographic braneworld by assuming the second slow-roll parameter $\eta$ is constant. The parameter $\eta$ can be either defined by the tachyon scalar field and the Hubble parameter or by the Hubble parameter only. By assuming a constant $\eta$, we derive and numerically solve a differential equation for the Hubble expansion rate. We calculate numerically the scalar spectral index and the tensor-to-scalar ratio. We confront the results with the observational data and find some constraints on the free model parameters. The swampland conjectures are discussed in the context of the constant-roll inflation, with some accent on the holographic model.

gr-qc↗

arXiv2023

Tachyon constant-roll inflation in Randall-Sundrum II cosmology

We study inflation in a model with constant second slow-roll parameter $\eta$. In this case, the Hubble expansion rate equation has analytical solutions describing four possible, nontrivial inflation scenarios. The evolution of the inflaton governed by a tachyon field is studied in the framework of the standard and Randall-Sundrum II cosmology. The attractor behavior of the solution is briefly demonstrated. Finally, the calculated values of the parameters $n_{\rm s}$ and $r$ are compared with observational data.

gr-qc↗

arXiv2019

Tachyon inflation in the holographic braneworld

A model of tachyon inflation is proposed in the framework of holographic cosmology. The model is based on a holographic braneworld scenario with a D3-brane located at the holographic boundary of an asymptotic ADS$_5$ bulk. The tachyon field that drives inflation is represented by a DBI action on the brane. We solve the evolution equations analytically in the slow-roll regime and solve the exact equations numerically. We calculate the inflation parameters and compare the results with Planck 2018 data.

gr-qc↗