arXiv subjects

Milan Milosevic

Publications and source records attributed to Milan Milosevic.

8 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.

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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.

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arXiv2024

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 $η$ is constant. The parameter $η$ can be either defined by the tachyon scalar field and the Hubble parameter or by the Hubble parameter only. By assuming a constant $η$, 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.

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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.

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arXiv2023

Tachyon constant-roll inflation in Randall-Sundrum II cosmology

We study inflation in a model with constant second slow-roll parameter $η$. 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.

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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.

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arXiv2017

Tachyon inflation in an AdS braneworld with back-reaction

We analyze the inflationary scenario based on the tachyon field coupled with the radion of the second Randall-Sundrum model (RSII). The tachyon Lagrangian is derived from the dynamics of a 3-brane moving in the five dimensional bulk. The AdS$_5$ geometry of the bulk is extended to include the radion. Using the Hamiltonian formalism we find four nonlinear field equations supplemented by the modified Friedmann equations of the RSII braneworld cosmology. After a suitable rescaling we reduce the parameters of our model to only one free parameter related to the brane tension and the AdS$_5$ curvature. We solve the equations numerically assuming a reasonably wide range of initial conditions determined by physical considerations. Varying the free parameter and initial conditions we confront our results with the Planck 2015 data.

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arXiv2015

Classicalization and Quantization of Tachyon-like Matter on (non)Archimedean Spaces

We consider a class of tachyon-like potentials, inspired by string theory, D-brane dynamics and cosmology in the context of classical and quantum mechanics. Motivated by the trans-Plankcian problem in the very early stage of cosmological evolution of the Universe, we consider the theoretical role of DBI-type tachyon scalar field, defined over the field of real as well as $p$-adic numbers, i.e. archemedean and nonarchimedean spaces. To simplify the equation of motion for the scalar field, canonical transformations are defined and engaged. The corresponding quantum propagators in the Feynman path integral approach on real and nonarchimedean spaces are calculated and discussed, as are possibilities for a quantum adelic generalization and its application.

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