Nandan Roy

Nandan Roy
Naresuan University · The Institute for Fundamental Study

Doctor of Philosophy

About

32
Publications
3,639
Reads
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446
Citations
Introduction
Presently, I am a Overseas specialist lecturer at the Naresuan University . My research interest is dark energy models and dynamical systems analysis.
Additional affiliations
August 2018 - present
Naresuan University
Position
  • Lecturer
October 2016 - July 2018
University of Guanajuato
Position
  • PostDoc Position
April 2015 - September 2016
Harish-Chandra Research Institute
Position
  • PostDoc Position
Education
January 2010 - April 2015

Publications

Publications (32)
Preprint
Full-text available
We investigate the interaction between the dark sectors from a dynamical systems perspective. A general setup for interacting dark energy models that incorporates both quintessence and phantom fields through a switch parameter, allowing an interaction in the dark sectors has been considered. In the first part of our analysis, we have not assumed an...
Conference Paper
Full-text available
In this paper, we present a dynamical system analysis of the tachyon dark energy model by parametrization of the equation of state (EoS) of the dark energy. The choice of parametrization can constrain the form of the field potential, and as a result, the theory can be directly constrained from the observation without assuming a particular form of t...
Preprint
Full-text available
In this paper, we present a dynamical system analysis of the tachyon dark energy model by parametrization of the equation of state (EoS) of the dark energy. The choice of parametrization can constrain the form of the field potential, and as a result, the theory can be directly constrained from the observation without assuming a particular form of t...
Article
In this work, we present a new scheme to study the tachyon-dark-energy model using dynamical systems analysis by considering parametrization of the equation of state (EOS) of the dark energy. Both the canonical and phantom field dynamics are investigated. In our method, we do not require any explicit form of the tachyon potential. Instead of the po...
Preprint
Full-text available
This study examines interacting quintessence dark energy models and their observational constraints for a general parameterization of the quintessence potential, which encompasses a broad range of popular potentials. Four different forms of interactions are considered. The analysis is done by expressing the system as a set of autonomous equations f...
Preprint
Full-text available
In this work we present a new scheme to study the tachyon dark energy model using dynamical systems analysis by considering parametrization of the equation of state(EoS) of the dark energy. Both the canonical and phantom field dynamics are investigated. In our method we do not require any explicit form of the tachyon potential. Instead of the poten...
Article
In this work we propose a simple general parametrization scheme of the Hubble parameter for the scalar field dark energy models. In our approach it is possible to incorporate both the quintessence and phantom scalar field in a single analytical scheme and write down relevant cosmological parameters which are independent of the nature of the scalar...
Preprint
Full-text available
In this work we propose a simple general parametrization scheme of the Hubble parameter for the scalar field dark energy models. In our approach it is possible to incorporate both the quintessence and phantom scalar field in a single analytical scheme and write down relevant cosmological parameters which are independent of the nature of the scalar...
Article
In this work, we study tracker phantom dark energy models with a general parametrization of the scalar potentials. Our analysis also considers the scenario of having both phantom field and the cosmological constant as the dark energy components. A detailed statistical analysis with current cosmological observations shows an increase in the value of...
Preprint
Full-text available
In this work, we study tracker phantom dark energy models with a general parameterization of the scalar potentials. Our analysis also considers the scenario of having both phantom field and the cosmological constant as the dark energy components. A detailed statistical analysis with current cosmological observations shows an increase in the value o...
Article
We study the dynamical properties of tracker quintessence models using a general parametrization of their corresponding potentials, and show that there is a general condition for the appearance of a tracker behavior at early times. Likewise, we determine the conditions under which the quintessence tracker models can also provide an accelerating exp...
Preprint
We study the dynamical properties of tracker quintessence models using a general parametrisation of their corresponding potentials, and show that there is a general condition for the appearance of a tracker behavior at early times. Likewise, we determine the conditions under which the quintessence tracker models can also provide an accelerating exp...
Article
Full-text available
In this work we have performed the dynamical system analysis for steep(er) exponential potentials considering different values of the steepness index n. We have performed the analysis using centre manifold theory as well as by employing numerical method. We have shown that in most of the cases, the higher values of steepness index corresponds to an...
Article
Though we have entered an era of high precision cosmology the form of the quintessence potentials still remain arbitrary. In this work we explore the interacting quintessence models considering a parametrization of the quintessence potentials and tried to constrain the form of potentials using the recent cosmological observations. The particular pa...
Preprint
Full-text available
In this work we have performed the dynamical system analysis for steep(er) exponential potentials considering different values of the steepness index $n$. We have performed the analysis using centre manifold theory as well as by employing numerical method. We have shown that in most of the cases, the higher values of steepness index corresponds to...
Preprint
We study the interacting quintessence model with two different types of interaction by introducing a general parameterization of the quintessence potentials. The form of the quintessence potentials is arbitrary as the recent cosmological observations failed to constrain any particular form of the potentials. We explore the interacting quintessence...
Article
Full-text available
In this work, we study the dynamical systems analysis of phantom dark energy models considering five different potentials. From the analysis of these five potentials we have found a general parametrization of the scalar field potentials which is obeyed by many other potentials. Our investigation shows that there is only one fixed point which could...
Article
Full-text available
We present a new parameterization of quintessence potentials for dark energy based directly upon the dynamical properties of the equations of motion. Such parameterization arises naturally once the equations of motion are written as a dynamical system in terms of properly defined polar variables. We have identified two different classes of paramete...
Preprint
We present a new parameterization of quintessence potentials for dark energy based directly upon the dynamical properties of the equations of motion. Such parameterization arises naturally once the equations of motion are written as a dynamical system in terms of properly defined polar variables. We have identified two different classes of paramete...
Article
Full-text available
In this work, we have studied the effect of higher order perturbations, particularly the second order in details, on the sonic horizon. We have considered two different schemes of perturbations which are velocity potential perturbation and mass acceleration rate perturbation. These two schemes give us qualitatively similar behaviour. We have found...
Article
Full-text available
The present work deals with the dynamical system investigation of interacting dark energy models (quintessence and phantom) in the framework of Loop Quantum Cosmology by taking into account a broad class of self-interacting scalar field potentials. The main reason for studying potentials beyond the exponential type is to obtain additional critical...
Article
Full-text available
In this work, we study the dynamical systems analysis of phantom dark energy models considering a general potential. The stability analysis of the system shows that there is only one fixed point which could be the beginning of the universe but there could be many options for our future destiny. A detail numerical analysis of the system is also done...
Preprint
The present work deals with the dynamical system investigation of interacting dark energy models (quintessence and phantom) in the framework of Loop Quantum Cosmology by taking into account a broad class of self-interacting scalar field potentials. The main reason for studying potentials beyond the exponential type is to obtain additional critical...
Article
Full-text available
The stability criteria for the generalized Brans-Dicke cosmology in a spatially flat, homogeneous and isotropic cosmological model is discussed in the presence of a perfect fluid. The generalization comes through the channel that the Brans-Dicke coupling parameter $\omega$ is allowed to be a function of the scalar field $\phi$. This generalization...
Article
Full-text available
In this thesis, we used dynamical systems analysis to find the qualitative behaviour of some dark energy models. Specifically, dynamical systems analysis of quintessence scalar field models, chameleon scalar field models and holographic models of dark energy are discussed in this thesis.
Article
The stability of interacting holographic dark energy model is discussed. It is found that for some class of the rate of interaction between dark matter and dark energy, the system has a natural solution where the universe had been decelerating in the beginning but finally settles down to an accelerated phase of expansion.
Article
The present work is an extensive study of the viable stable solutions of chameleon scalar field models leading to possibilities of an accelerated expansion of the universe. It is found that for various combinations of the chameleon field potential $V(\phi)$ and the coupling $f(\phi)$ of the chameleon field with matter, a stable solution for an acce...
Article
Full-text available
The stability of interacting holographic dark energy model is discussed. It is found that for some class of the rate of interaction between dark matter and dark energy, the system has a natural solution where the universe had been decelerating in the begnning but finally settles down to an acelerated phase of expansion.
Article
Full-text available
The present work is an extensive study of the viable stable solutions of chameleon scalar field models leading to possibilities of an accelerated expansion of the universe. It is found that for various combinations of the chameleon field potential $V(\phi)$ and the coupling $f(\phi)$ of the chameleon field with matter, a stable solution for an acce...
Article
Full-text available
The present work deals with a dynamical systems study of quintessence potentials leading to the present accelerated expansion of the universe. The principal interest is to check for late time attractors which give an accelerated expansion for the universe. Two examples are worked out, namely the exponential and the power-law potentials.
Article
Full-text available
With the tracking condition, the stability of quintessence solutions are examined. It is found that there is only one physically relevant fixed point for the system generically. Two specific examples of quintessence potentials are worked out in the frame work.

Questions

Questions (2)
Question
HI, I want to draw 2d phase plot of a 3d system. I am using Mathematica to do this but the problem is I can only plot by fixing one variable to be constant. I don't like this and it also does not agree with my analytical finding. If some one can help me I will be grateful. I need a code which can solve the 3d system and can plot a 2d projection.
Question
What is the stability of a fixed point (non-isolated), which has zero eigenvalues? Is there any analytical procedure for finding stability of these type of fixed points. If numerical analysis can do the job, then how to do that?

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