arXiv subjects

Phongpichit Channuie

Publications and source records attributed to Phongpichit Channuie.

At least 91 records · Page 5Linked to original sources

arXiv2019

Quantum Information metric for time-dependent quantum systems and higher-order corrections

It is well established that quantum criticality is one of the most intriguing phenomena which signals the presence of new states of matter. Without prior knowledge of the local order parameter, the quantum information metric (or fidelity susceptibility) can indicate the presence of a phase transition as well as it measures distance between quantum states. In this work, we calculate the distance between quantum states which is equal to the fidelity susceptibility in quantum model for a time-dependent system describing a two-level atom coupled to a time-driven external field. As inspired by the Landau-Zener quantum model, we find in the present work information metric induced by fidelity susceptibility. We, for the first time, derive a higher-order rank-3 tensor as a third-order fidelity susceptibility. Having computed quantum noise function in this simple time-dependent model we show that the noise function eternally lasts long in our model.

quant-ph↗

arXiv2019

On gravitational wave modes in Nash theory of gravity

In this Letter, we consider original Nash theory of gravity. In terms of the scalar fields representation, Nash gravity is equivalent to the action of bi-scalar tensor gravity with four derivative terms of metric tensor. We then quantify the ghost in the theory. In order to study the gravitational wave modes of the theory, we perform a small perturbation over a fixed Minkowski background. We discover the standard wave equation and obtain the solutions as those of the standard general relativity. In order to satisfy the GR in the weak field limit, we further modify the original Nash theory by adding the Einstein-Hibert term called modified Nash gravity. In this theory, we once study the gravitational wave modes. We derive equations of motion and examine the solutions. We discover the two-mode solutions: the massless graviton and the massive one. Using a uniform prior probability on the graviton mass, we can constrain mass parameter.

gr-qc↗

arXiv2019

Deformed Starobinsky model in gravity's rainbow

In the context of gravity's rainbow, we study the deformed Starobinsky model in which the deformations take the form $f(R)\sim R^{2(1-α)}$, with $R$ the Ricci scalar and $α$ a positive parameter. We show that the spectral index of curvature perturbation and the tensor-to-scalar ratio can be written in terms of $N,\,λ$ and $α$, with $N$ being the number of {\it e}-foldings, $λ$ a rainbow parameter. We compare the predictions of our models with Planck data. With the sizeable number of {\it e}-foldings and proper choices of parameters, we discover that the predictions of the model are in excellent agreement with the Planck analysis. Interestingly, we obtain the upper limit and the lower limit of a rainbow parameter $λ$ and a positive constant $α$, respectively.

gr-qc↗

arXiv2018

Unification of inflation and dark matter in the Higgs-Starobinsky model

In this work, we study unified picture of inflation and dark matter in the Higgs-Starobinsky (HS) model. As pointed out in the literature, Starobinsky $R^2$ inflation is induced by quantum correction effect from the large Higgs-curvature (graviton) coupling. We start with non-minimal coupling HS action in Jordan frame. We then transform the Jordan frame action into the Einstein one using the conformal transformation. The inflation potential is derived from the gravitational action of non-minimal-Higgs coupling and Starobinsky term in Einstein frame where the $R^2$ term is dominated in the inflationary phase of the universe. For model of inflation, we compute the inflationary parameters and confront them with Planck 2015 data. We discover that the predictions of the model are in excellent agreement with the Planck analysis. In addition, we study the Higgs field as a candidate for dark matter. The renormalization group equations (RGEs) of Higgs-Starobinsky scenario with standard model at one-loop is qualitatively analyzed. By using the solutions of parameter spaces from RGE analysis, the remnants of the quantum effect ($R^2$ term) from Higgs-graviton coupling will be implied by dark matter relic abundance.

gr-qc↗

arXiv2018

Impact of the Rastall parameter on perfect fluid spheres

We examine the effects of the Rastall parameter on the behaviour of spherically symmetric static distributions of perfect fluid matter. It was claimed by Visser [Physics Letters B, 782, 83, (2018)] that the Rastall proposition is completely equivalent to the Einstein theory. While many authors have raised contrary arguments, our intention is to analyze the properties of Rastall gravity through variation of the Rastall parameter in the context of perfect fluids spheres that may be used to model neutron stars or cold fluid planets. This analysis also serves to counter the claim that Rastall gravity is equivalent to the standard Einstein theory. It turns out that the condition of pressure isotropy is exactly the same as for Einstein gravity and hence that any known solution of the Einstein equations may be used to study the effects of the Rastall dynamical quantities. Moreover, by choosing the well studied Tolman metrics, we discover that in the majority of cases there is substantial deviation from the Einstein case when the Rastall parameter vanishes and in cases where the Einstein model displays defective behaviour, certain Rastall models obey the well known elementary requirements for physical plausibility. These empirical findings do not support the idea that Rastall theory is equivalent to Einstein theory as several deviations in physical behavior are displayed as counter-examples.

gr-qc↗

arXiv2018

Noether symmetry in a nonlocal f(T) Gravity

It is well known that the Noether symmetry approach proves to be very useful not only to fix physically viable cosmological models but also to reduce dynamics and achieve exact solutions. In this work, We examine a formal framework of nonlocal $f(T)$ theory of gravity through the Noether symmetry approach. The Noether equations of the nonlocal $f(T)$ theory are obtained for flat FLRW universe. We analyse the dynamics of the field in a nonlocal $f(T)$ gravity admitted by the Noether symmetry. We observe that there exists a transition from a deceleration phase to the acceleration one in our present analysis. We check statefinder parameters for the obtained solutions which imply that some particular solutions are comparable with the Lambda-CDM model.

gr-qc↗

arXiv2018

On the Scalar-Vector-Tensor Gravity: Black Hole, Thermodynamics and Geometrothermodynamics

Recently, a new class of modified gravity theories formulated via an additional scalar and vector field on top of the standard tensor field has been proposed. The direct implications of these theories are expected to be relevant for cosmology and astrophysics. In the present work, we revisit the modified framework of the scalar-vector-tensor theories of gravity. Surprisingly, we discover novel metric function for the black hole solutions. We also investigate the semi-classical thermodynamics of the black holes and study the thermodynamic properties of the obtained solutions. Moreover, we quantify the entropy and the temperature of the new black hole and also calculate the heat capacity. Finally, we also apply the formalism of the geometrothermodynamics to examine thermodynamic properties of the new black hole. This formalism yields results consistent with those obtained from the usual thermodynamic implementation.

gr-qc↗

arXiv2018

Stable Gravastars: Guilfoyle's electrically charged solutions

Compelling alternatives to black holes, namely, gravitational vacuum star ({\it gravastar}) models, the multilayered structure compact objects, have been proposed to avoid a number of theoretical problems associated with event horizons and singularities. In this work, we construct a spherically symmetric thin-shell charged gravastar model where the vacuum phase transition between the de Sitter interior and the external Reissner--Nordstr$\ddot{\text{o}}$m spacetime (RN) are matched at a junction surface, by using the cut-and-paste procedure. Gravastar solutions are found among the Guilfoyle exact solutions where the gravitational potential $W^2$ and the electric potential field $ϕ$ obey a particularly relation in a simple form $ a\left(b-εϕ\right)^2 +b_1$, where $a$, $b$ and $b_1$ being arbitrary constants. The simplest ansatz of Guilfoyle's solution is implemented by the following assumption: that the total energy density $8πρ_m+\frac{Q^2}{ r^4}$ = constant, where $Q(r)$ is the electric charge up to a certain radius $r$. We show that, for certain ranges of the parameters, we can avoid the horizon formation, which allows us to study the linearized spherically symmetric radial perturbations around static equilibrium solutions. To lend our solution theoretical support, we also analyze the physical and geometrical properties of gravastar configurations.

gr-qc↗

arXiv2018

Noether symmetry in the Nash theory of gravity

This paper deals with the study of Bianchi type-I universe in the context of Nash gravity by using the Noether symmetry approach. We shortly revisit the Nash theory of gravity. We make a short recap of the Noether symmetry approach and consider the geometry for Bianchi-type I model. We obtain the exact general solutions of the theory inherently exhibited by the Noether symmetry. We also examine the cosmological implications of the model by discussing the two cases of viable scenarios. Surprisingly, we find that the predictions are nicely compatible with those of the LambdaCDM model.

physics.gen-ph↗

arXiv2018

Noether symmetry approach in the cosmological alpha-attractors

In cosmological framework, Noether symmetry technique has revealed a useful tool in order to examine exact solutions. In this work, we first introduce the Jordan-frame Lagrangian and apply the conformal transformation in order to obtain the Lagrangian equivalent to Einstein-frame form. We then analyse the dynamics of the field in the cosmological alpha-attractors using the Noether sysmetry approach by focusing on the single field scenario in the Einstein-frame form. We show that with a Noether symmetry the coresponding dynamical system can be completely integrated and the potential exhibited by the symmetry can be exactly obtained. With the proper choice of parameters, the behavior of the scale factor displays an exponential (de Sitter) behavior at the present epoch. Moreover, we discover that the Hubble parameters strongly depends on the initial values of parameters exhibited by the Noether symmetry. Interestingly, it can retardedly evolve and becomes a constant in the present epoch in all cases.

gr-qc↗

arXiv2018

Relativistic compact stars with charged anisotropic matter

In this article we perform a detailed theoretical analysis for a class of new exact solutions with anisotropic fluid distribution of matter for compact objects in hydrostatic equilibrium. To achieve this we call the relation between the metric functions, namely, embedding class one condition. The investigation is carried out by generalising the properties of a spherical star with an emphasis on hydrostatic equilibrium equation, i.e., the generalised Tolman-Oppenheimer-Volkoff equation, in our understanding of these compact objects. We match the interior solution to an exterior Reissner-Nordstrom solution, and study some physical features of this models, such as the energy conditions, speeds of sound, and mass - radius relation of the star. We also show that obtained solution is compatible with observational data for compact object Her X-1.

gr-qc↗

arXiv2017

Cosmological dynamics of magnetic Bianchi I in viable $f(R)$ models of gravity

Standard dynamical system analysis of Einstein-Maxwell equation in $f(R)$ theories is considered in this work. We investigate cosmological dynamics of a uniform magnetic field in the Orthogonal Spatially Homogeneous (OSH) Bianchi type I universe with viable $f(R)$ models of gravity. In this work, the $f(R) = R -αR^n$ and $f(R) = \left( R^b - Λ\right)^c$ models are examined by using our dynamical system analysis. Our results show that both of two $f(R)$ models have a viable cosmological consequence identical to the analysis present in Ref.\cite{Amendola:2007nt} for the FLRW background. Contrary to Ref.\cite{Amendola:2007nt}, we discover in our models that there is an additional anisotropic and non-zero cosmological magnetic fields fixed point emerging before the present of the standard matter epoch. This means that the universe has initially isotropic stage with the intermediated epoch as the anisotropic background and it ends up with the isotropic late-time acceleration. The primordial magnetic fields play a crucial role of the shear evolutions obtained from these two models which have the same scaling of the cosmic time as $σ\sim t^{-\frac13}$, instead of $σ\sim t^{-1}$ for the absence of the primordial magnetic cases.

gr-qc↗

arXiv2017

Preheating in an inflationary model with disformal coupling

In this work, we investigate the preheating mechanism in a disformally-coupled inflationary model where the scalar field $ϕ$ (which is the inflaton field) naturally coupled to another matter field $χ$ induced by the disformal transformation. In the present scenario, novel derivative interactions mixing the kinetic terms of the two fields emerge inherently. We start by deriving the evolution of the background system when the back reaction on the background field is neglected. We examine the particle production due to parametric resonances in the models and find in Minkowski space that the stage of parametric resonances can be described by the Mathieu equation. Interestingly, we discover that broad resonances in our models can be typically achieved. Finally, we compare our results with previously studied model with derivative couplings.

hep-ph↗

arXiv2017

A unified composite model of inflation and dark matter in the Nambu-Jona-Lasinio theory

In this work, we propose a cosmological scenario inherently based on the effective Nambu-Jona-Lasinio (NJL) model that cosmic inflation and dark matter can be successfully described by a single framework. On the one hand, the scalar channel of the NJL model plays a role of the composite inflaton (CI) and we show that it is viable to achieve successful inflation via a non-minimal coupling to gravity. For model of inflation, we compute the inflationary parameters and confront them with recent Planck 2015 data. We discover that the predictions of the model are in excellent agreement with the Planck analysis. We also present in our model a simple connection of physics from the high scales to low scales via renormalization group equations of the physical parameters. On the other hand, the pseudoscalar channel can be assigned as a candidate for composite dark matter (CD). For model of dark matter, we couple the pseudoscalar to the Higgs sector of the standard model with the coupling strength $κ$ and estimate its thermally-averaged relic abundance. We discover that the CD mass is strongly sensitive to the coupling $κ$. We find in case of light CD, $M_{s} M_{W,\,Z}$ (or $>M_{h}$), the required relic abundance can be satisfied for value of the CD mass $M_{s}\sim 410\,{\rm GeV}$ for $κ= 0.5$. In contradiction to the light mass case, however, the CD mass in this case can even be heavier when the coupling is getting larger.

hep-ph↗

arXiv2016

Preheating after technicolor inflation

We investigate the particle production due to parametric resonances in model of inflation where the lightest composite state stemming from the minimal walking technicolor theory plays the role of the inflaton. For model of inflation, the effective theory couples non-minimally to gravity. Regarding the preheating, we study in details a model of a composite inflaton field $ϕ$ coupled to another scalar field $χ$ with the interaction term $g^{2}ϕ^{2}χ^{2}$. Particularly, in the Minkowski space, the stage of parametric resonances can be described by the Mathieu equation. Interestingly, we discover that broad resonances can be typically achieved and potentially efficient in our model causing the number of particle density in this process exponentially increases.

hep-ph↗

arXiv2016

Composite Inflation in the light of 2015 Planck data

In this work, we examine cosmological constraints on models of composite inflation based on the slow-roll approximation by using the recent Planck measurement. We compare the spectral index of curvature perturbation (and its running) and the tensor-to-scalar ratio predicted by such models with Planck 2015 data. We find that the predictions of technicolor inflation are nicely consistent with the Planck analysis. Moreover, the predictions from the second model, glueball inflation, are in good agreement with the Planck data at $2σ$C.L. However, the final two models, super glueball inflation and orientifold inflation, favor only the rather large value of the tensor-to-scalar ratio of which the predictions are in tension with the Planck analysis.

hep-ph↗

arXiv2016

Starobinsky Model in Rainbow Gravity

In this paper, we study the Starobinsky model of inflation in the context of gravity's rainbow theory. We propose that gravity rainbow functions can be written in the power-law form of the Hubble parameter. We present a detailed derivation of the spectral index of curvature perturbation and the tensor-to-scalar ratio and compare the predictions of our models with Planck 2015 data. We discover that in order to be consistent with Planck data up to $2σ$ C.L., the viable values of $N_{k}$ $e$-folds would satisfy $42\lesssim N_{k}\lesssim 87$ and the rainbow parameter $λ$ is nicely constrained to be $λ\lesssim6.0$.

gr-qc↗

arXiv2015

Strong Dynamics and Inflation: a review

In this article, we review how strong dynamics can be efficiently employed as a viable alternative to study the mechanism of cosmic inflation. We examine single-field inflation in which the inflaton emerges as a bound state stemming from various strongly interacting field theories. We constrain the number of e-foldings for composite models of inflation in order to obtain a successful inflation. We study a set of cosmological parameters, e.g., the primordial spectral index $n_{s}$ and tensor-to-scalar ratio $r$, and confront the predicted results with the joint Planck data, and with the recent BICEP2 data.

hep-ph↗