arXiv subjects

Ankur Chaubey

Publications and source records attributed to Ankur Chaubey.

4 recordsLinked to original sources

arXiv2022

Magnetized matter effects on dilaton photon mixing

Dilatons ($ϕ(x)$) are a class of bosonic scalar particles associated with scaling symmetry and its compensation (under the violations of the same). Due to two photon coupling, they can produce optical signatures in a magnetic field. In vacuum or plain matter they couple to one of the transversely polarized state of the photon. But in a magnetized matter, they couple to both the transversely polarized state of photon (due to emergence of a parity violating part of photon self energy contribution from a magnetized matter). A part of this work is directed towards understanding the issue of mixing of scalar with various polarizations states of photon in a medium ( magnetized or unmagnetized ) due to the constraints from different discrete (CPT) symmetries associated with the interaction. Based on these symmetry aided arguments, the structure of the mixing matrix is found to be $3 \times 3$. Thus there exists non-zero finite probabilities of oscillation between different polarization states of photon to dilaton. Our analytical and numerical analysis show no existence of periodic oscillation length either in temporal or spatial direction for most general values of the parameters in the theory. Possible astrophysical consequences of these results, those can be detected through observations are discussed.

hep-ph↗

arXiv2022

Differentiating Dilatons from Axions by their mixing with photons

According to the model ($Λ$CDM), based on deep cosmological observations, the current universe is constituted of 5$\%$ baryonic matter and 25 $\%$ non-baryonic cold dark matter (of speculative origin). These include quanta of scalar filed like dilaton($ϕ$) of scale symmetry origin and quanta of pseudoscalar field of extra standard model symmetry ( Peccei-Quinn) origin, like axion ($ϕ'$). These fields couple to di-photons through dim-5 operators. In magnetized medium, they in principle can interact with the three degrees of freedom (two transverse ($A_{\parallel,\perp}$) and one longitudinal ($A_{L}$)) of photon($γ$) as long as the total spin is conserved. Because of intrinsic spin being zero, both $ϕ$ and $ϕ'$ could in principle have interacted with $A_{L}$, (having $s_{z}=0$). However, out of $ϕ$ and $ϕ'$ only one interacts with $A_{L}$. Furthermore, the ambient external magnetic field and media, breaks the intrinsic Lorentz symmetry of the system invoking Charge conjugation, Parity and Time reversal symmetries, we analyse the mixing dynamics of $ϕγ$ and $ϕ'γ$ systems and the structural {\it difference} of their mixing pattern. The strength of electromagnetic (EM) signals due to $ϕγ$ and $ϕ'γ$ mixing as a result would be {\it different}. We conclude by commenting on the possibility of detecting this {\it difference} -- in polarimetric observables the EMS -- using the existing space-borne detectors.

hep-ph↗

arXiv2020

Exploring scalar-photon interactions in energetic astrophysical events

Scalar fields like dilaton appear in quantum field theory (QFT) due to scale symmetry breaking. Their appeal also extends to modified theories of gravity, like $F(R)$ gravity, Horva Lifshitz gravity etc. In unified theories they make their appearance through compactification of the extra dimension. Apart from resolving the issues of compactification scale and size, the particles of their fields can also turn out to be excellent candidate to solve the dark energy (DE) and dark matter (DM) problem of the universe. In this work we study their mixing dynamics with photons in a magnetized media, by incorporating the effect of parity violating part of the photon polarization tensor, evaluated in a finite density magnetized media. This piece, though in general is odd in the external magnetic field strength $eB$; in this work we however have retained terms to $O$($eB$). We are able to demonstrate in this work that, in magnetized medium a dilatonic scalar field $(ϕ)$ can excite the two transverse degrees of freedom (DOF) of the photons. One due to direct coupling and the other indirectly through the parity violating term originating due to magnetized medium effects. This results in the mixing dynamics being governed by, $3\times 3$ mixing matrices. This mixing results in making the underlying media optically active. In this work we focus on the spectro-polarimetric imprints of these particles, on the spectra of the electromagnetic (EM) fields of Gamma Ray Bursters (GRB). Focusing on a range of parameters (i.e., magnetic field strength, plasma frequency $(ω_{p})$, size of the magnetized volume, coupling strength to photons and their mass) we make an attempt to point out how space-borne detectors should be designed to optimise their detection possibility.

astro-ph.HE↗

arXiv2019

Mixing dynamics of dimension-five interactions (scalar/pseudoscalar-photon) in magnetized medium

In many extentions of standard model, dimension-5 scalar di-photon ($g_{γγϕ}ϕ$ $F^{μν}F_{μν}$ ) or pseudoscalar di-photon ($g_{γγa}a\tilde{F}^{μν} F_{μν} $, ) interaction materializes due to scale symmetry breaking or $U_A(1)$ symmetry breaking. In a magnetized vacuum (i.e., in an external background field $\bar{F}_{μν} $) the transverse degrees of freedom of the photons-- for such systems-- can be described in terms of the form factors constructed out of the background field strength tensor ($\bar{F}_{μν} $) and the same for dynamical photon ($f^{μν}$); they happen to be $\bar{F}_{μν}f^{μν}$ and ${\tilde{\bar{F}}_{μν}f^{μν}}$. These form factors transform differently under CP transformation. While $\bar{F}_{μν}f^{μν}$ (describing polarization orthogonal to B ($|γ_{||} >$)) is CP even, the other one, ${\tilde{\bar{F}}_{μν}f^{μν}}$( describing polarization along B ($|γ_\bot >$), is CP odd. In the interaction Lagrangian, if the scalar is interchanged with the pseudoscalar, the role of the two form factors just gets interchanged. Thus for nearly degenerate strengths of the coupling constants ( $g_{γγϕ}$ and $g_{γγ_a}$ ) and masses ($m_ϕ$ and $m_a$ ) of the respective candidates, proper identification of one from the other may become very difficult in laboratory or astrophysics based experiments. The basic motivation of this investigation is to reduce this uncertainty through incorporation of parity violating ({\it originating through magnetized medium effects }) part of the photon self-energy in the effective Lagrangian. This step, in turn affects the (Pseudo) Scalar Photon mixing dynamics drastically and brings out a significant change in the spectrum of the electromagnetic beam undergoing such interaction.

hep-ph↗