arXiv subjects

Jafar Khodagholizadeh

Publications and source records attributed to Jafar Khodagholizadeh.

At least 19 recordsLinked to original sources

arXiv2026

Polarization of the CMB in the Standard Model Extension

In standard cosmology, Cosmic Microwave Background photons near the last scattering surface exhibit only linear polarization due to Compton scattering, leading to the assumption that primordial circular polarization is negligible. However, the physics of Lorentz violation (LV), associated with specific operators, can influence these polarization characteristics. This study employs the Boltzmann equation within the framework of the Standard Model Extension (SME) to explore how the background LV tensor $ K_{AF} $ can induce circular polarization in CMB radiation. By computing the transformation of linear polarization into circular polarization and utilizing the Faraday conversion angle, we derive a bound for $ K_{AF} $ on the order of $ 10^{-41} \, \text{GeV} $, aligning with recent findings. Additionally, we consider the total pure photon terms within the SME, demonstrating that LV in the presence of scalar perturbations can also generate cosmic birefringence (CB) in the CMB radiation. Through analysis of best-fitting CB angles, we establish a more stringent bound of approximately $ 10^{-32} \, \text{GeV} $ for $ K_{F} $.

astro-ph.CO↗

arXiv2025

Muon anomalous magnetic moment and Right handed sterile neutrino

The muon's magnetic moment is a fundamental quantity in particle physics and the deviation of its value from quantum electrodynamics (QED), motivates research beyond the standard models (SM). In this study, we utilize the effective coupling of right-handed sterile neutrinos with SM gauge bosons to calculate the muon anomalous magnetic moment ($\boldsymbolμ$AMM) at one-loop level. The contribution of the sterile neutrino interactions on the $\boldsymbolμ$AMM is calculated by considering the standard and non-standard neutrino interactions. Our results show that the standard sterile neutrino interactions give a negligible contribution to $Δa_{\boldsymbolμ}$ while the non-standard neutrino interactions can play a significant role in explaining the muon $(g-2)$ anomaly. In the context of the non-standard neutrino interaction, our calculation shows that a Dirac mass scale $M_D$ around $100\,\text{GeV}$ could explain the muon anomaly if the right handed sterile neutrino's coupling with SM particles is about $\mathcal{G}_R\approx 10^{-3}$. We have also plotted the allowed region of the model parameters that satisfy the experimental data on $Δa_{\boldsymbolμ}^{SN}$ and discuss the percentage of the ${\boldsymbolμ}$ anomaly compensation in terms of the coupling constant $\mathcal{G}_R$.

hep-ph↗

arXiv2024

Testing loop quantum gravity by quasi-periodic oscillations: rotating blackholes

We investigate a compelling model of a rotating black hole that is deformed by the effects of loop quantum gravity (LQG). We present a simplified metric and explore two distinct geometries: one in which the masses of the black hole and white hole are equal, and another in which they differ. Our analysis yields the radius of the innermost stable circular orbits (ISCO), as well as the energy and angular momentum of a particle within this framework. Additionally, we find the frequency of the first-order resonance separately. We constrain the model by the quasi-periodic oscillations (QPO) of the X-ray binary GRO J1655-40. We show that $λ=0.15^{+0.23}_{-0.14}$ at $1σ$ confidence level for equal mass black hole and white hole geometry. For the other geometry we get $λ=0.11^{+0.07}_{-0.07}$ at $1σ$ confidence level.We encounter a degeneracy in the parameter space that hinders our ability to constrain $λ$ with greater precision.

gr-qc↗

arXiv2024

Probing the warped vacuum geometry around a Kerr black hole by quasi-periodic oscillations

We investigate quasi-periodic oscillations (QPOs) in the context of a new rotating black hole solution that incorporates a cosmological constant. Recent work by the authors in \cite{Ovalle:2022eqb} interpreted the cosmological constant, denoted as $Λ$, as a form of vacuum energy and employed a gravitational decoupling approach to derive an extended Kerr-de Sitter black hole solution, which is geometrically richer than the classical case. In this study, we derive the expressions for timelike circular geodesics within this solution and, using a relativistic precision model, calculate the corresponding frequencies of the QPOs. To constrain our model, we apply Bayesian formalism, utilizing data from three well-known microquasars: GRO 1655-40, XTE 1550-564, and GRS 1915+105. Our analysis reveals that$Λ$ is degenerate and correlated with other parameters. Finally, we perform a Bayesian model comparison with the Kerr metric and find that the Kerr metric is favored among the models considered.

gr-qc↗

arXiv2024

Generation of the CMB cosmic Birefringence through Axion-like particles, Sterile and Active neutrinos

The cosmic birefringence (CB) angle refers to the rotation of the linear polarization plane of Cosmic Microwave Background (CMB) radiations when parity-violating theories are considered. We analyzed the Quantum Boltzmann equation for an ensemble of CMB photons interacting with the right-handed sterile neutrino dark matter (DM) and axion-like particles (ALPs) DM in the presence of the scalar metric perturbation. We used the birefringence angle of CMB to study those probable candidates of DM. It is shown that the CB angle contribution of sterile neutrino is much less that two other sources considered here. Next, we combined the results of the cosmic neutrinos' contribution and the contribution of the ALPs to producing the CMB birefringence and discussed the uncertainty on the parameter space of axions caused by the share of CMB-cosmic neutrino interaction in generating this effect. Finally, we plotted the EB power spectrum of the CMB and showed that this spectrum behaves differently in the presence of cosmic neutrinos and ALPs interactions in small $l$. Hence, future observed data for $C^{l}_{EB}$, will help us to distinguish the CB angle value due to the various sources of its production.

hep-ph↗

arXiv2023

Constraints on Dark Energy from the Gravitational Wave Background

Current observational data indicate that dark energy (DE) is a cosmological constant without considering its conclusiveness evidence. Considering the dynamic nature of $Λ$ individually as a function of time and the scale factor, we review their effects on the gravitational waves. This article is a continuation of the previous work \textit{JHEAp 36 (2022) 48-54}, in which DE only was based on Hubble's parameter and/or its derivatives. For the DE model based on the scale factor ($a^{-m}$), the results showed that the parameter $m$ is more limited as $ 2 < m \leqslant 3$ compared with the other models and due to the small value of DE density at the early universe. It is only in the mode $m=3$ that DE affects the low-frequency gravitational waves when its frequency is less than the $10^{-3}$Hz in a matter-dominated epoch. The broad bound on reducing the amplitude and the "B-B" polarization multipole coefficients, from maximum to minimum, is for the models developed based on the Hubble parameter function. There are primary sources of low- and very low-frequency GWs, such as the coalescence of massive black hole binaries with $M_{bh} > 10^{3} M_{sun}$, to determine the type of DE by mHz frequency space experiments (e.g., LISA) and by nHz-range NANOGrav 15-year data.

gr-qc↗

arXiv2023

Cosmic Birefringence as a probe of dark matter nature: Sterile neutrino and dipolar dark matter

Recently, non-zero rotation angle $β=0.30^\circ\pm0.11^\circ$ $(68\%\text{ C.L.})$ [Phys. Rev. Lett. \textbf{128}, no.9, 091302 (2022)] has been reported for linear polarization of cosmic microwave background (CMB) radiation, which is known as cosmic birefringence (CB). We used this birefringence angle of CMB to study and distinguish different candidates of dark matter (DM), e.g., dipolar and sterile neutrino DM. We calculated CMB forward scattering by those probable candidates of DM to generate $β$ in the presence of primordial scalar fluctuations' background. We explicitly plotted bounds on the mass and electromagnetic coupling for different sectors of DM, sterile neutrino, and dipolar DM, and compared them with other experimental bounds. Regarding dipolar DM, our calculations put a bound on the Majorana magnetic dipole moment about $\mathcal{M}\leqslant 1.4\times10^{-14}\,\fracβ{0.30^\circ}\sqrt{\frac{m_{\text{\tiny{DM}}}}{1\,GeV}}\, e.\text{\,cm}$. In the case of sterile neutrino DM, the bound on the mass and mixing angle was estimated at $θ^2 \leqslant 3.3\,(rad)^2\fracβ{0.30^\circ}\,\frac{m_{DM}}{\rm{KeV}} $, which can be a new constraint for sterile neutrino DM whose production mechanism is motivated by models with a hidden sector coupled to the sterile neutrino. Based on our results, if the constraint on the mass and the electromagnetic coupling for DM must be within the allowed region, none of the considered candidates can compensate for all the observed CB angles. We also discussed the maximum contribution of the CB angle via CMB forward scattering by different sectors of the dark matter.

hep-ph↗

arXiv2023

CMB Polarization by the Asymmetric Template of Scalar Perturbations

Inspired by a dipole asymmetric template for the CMB temperature map in the primordial scalar fluctuations observed by Planck at a large scale, we examine the contribution of a similar template for power asymmetry in modifying the linear polarization pattern of CMB. Replacing un-modulated temperature fluctuation with dipolar modulated one in time evolution equations somehow breaks linear perturbation in the various components of the CMB map. This non-linearity allows deflecting CMB polarization in patterns that contain divergence-free components. The explicit expressions for the angular power spectra of the electric and magnetic-type parities of linear polarization are derived in the form of the line of sight integral solutions. Our results demonstrate that the electric-type polarization is modified and the magnetic-type polarization would be produced. Such imprints depend on the linear and square of the asymmetric amplitude for $E$- and $B$-modes power spectra, respectively. For the observed dipole template, the value of $B$ polarization spectrum at the large scale ($\ell\lesssim 10$) is almost equivalent to the power spectrum obtained from Compton scattering in the presence of tensor perturbation with tensor to scalar ratio about $r\simeq0.005$.

gr-qc↗

arXiv2023

Cross-correlation Power Spectra and Cosmic Birefringence of the CMB via Photon-neutrino Interaction

In the context of the standard model of particles, the weak interaction of cosmic microwave background (CMB) and cosmic neutrino background (C$ν$B), can generate non-vanishing TB and EB power spectra in the order of one loop forward scattering, in the presence of scalar perturbation, which is in contrast with the standard scenario cosmology. Comparing our results with the current experimental data may provide, significant information about the nature of C$ν$B, including CMB-C$ν$B forward scattering for TB, TE, and EB power spectra. To this end, different cases were studied, including Majorana C$ν$B and Dirac C$ν$B. On the other hand, it was shown that the mean opacity due to cosmic neutrino background could behave as an anisotropic birefringent medium and change the linear polarization rotation angle. Considering the contributions from neutrino and anti-neutrino forward scattering with CMB photons (in the case of Dirac neutrino), we introduce relative neutrino and anti-neutrino density asymmetry ($δ_ν=\frac{Δn_ν}{n_ν}=\frac{n_ν-n_{\barν}}{n_ν}$). Then, using the cosmic birefringence angle reported by the Planck data release $β=0.30^\circ\pm0.11^\circ$ ($68\%C.L.$), some constraints can be put on $δ_ν$. Also, the value of cosmic birefringence due to Majorana C$ν$B medium is estimated at about $β|_ν\simeq0.2$ rad. In this respect, since Majorana neutrino and anti-neutrino are exactly the same, both CB contributions will be added together. However, this value is at least two orders larger than the cosmic birefringence angle reported by the Planck data release, $β=0.30^\circ\pm0.11^\circ$ ($68\%C.L.$).

hep-ph↗

arXiv2021

Neutrinos as a probe of curvature

Neutrinos, as the anisotropic stress tensor, have a damping effect on the tensor mode perturbation from inflation to the $ Λ$ dominated era. First, we study the squared amplitude reduction for the wavelength entering the horizon during radiation and matter-dominated phases in the negatively curved de Sitter spacetime. Then, by comparing with other spatial spacetimes, $ K=0 $ and $K=1$, the highest difference between closed and open cases is seen in the matter-dominated era. Thus, neutrinos can be added as another candidate for determining the nature of space-time.

gr-qc↗

arXiv2021

A new experiment for the gravitational waves detection

A new experiment for the gravitational waves (GWs) detection is proposed. It is indeed shown that the effect of GWs on sound waves (SWs) in a fluid is that GWs vary the pressure of the fluid by crossing it. This variation can be found by analysing the gauge of the local observer. It is shown that one can, in principle, detect GWs through the proposed new experiment. The variation of the pressure of the fluid, which represents detected signals, are indeed much higher than the correspondent values of GWs amplitudes. The examples of rotating neutron stars (NSs) and relic GWs are discussed. Remarkably, a confrontation of the proposed new method with a previous paper of Singh et al. on a similar approach shows a possible improvement of the sensitivity concerning the potential detection of GWs. It must be emphasized that this proposed procedure may be difficult in practical experiments because of the presence of different types of noise. For this reason, a Section of the paper is dedicated to the discussion of such noises. On the other hand, this paper must be considered as being pioneering in the new proposed approach. Thus, we hope in future, more precise studies of the noise which concerns the proposed new experiment will be done.

physics.gen-ph↗

arXiv2021

Gravitational Waves in a Closed Spacetime via Deviation Equation

Within the closed universe, we obtain the amplitude and frequency of gravitational waves in the terms of discrete wave numbers, wave propagation time, and cosmological constant using the deviation equation in the first-order perturbed metric. We demonstrate that the cosmological constant effect on GWs is only seen in the early universe. Also, by considering the time evolution of a gravitational wave in a closed spacetime, we investigate its effect on a circle of nearby massless particles, which will be compared with this case in the flat spacetime. Expanding the universe has effective damping on GWs; thus, we suggest it can be used as a tool to characterize the large-scale curvature of the universe

gr-qc↗

arXiv2021

Are latest detected events of gravitational waves in favor of some models of inflation based on string theory?

The general potential of power-law inflation is as $ V(ϕ)\propto ϕ^{n} $ with scalar field $ϕ$. The behavior of inflation is often known as power-law expansion like $S(η)\propto η^{1+β}$ with $1+β<0$. In this paper, the theoretical spectra of relic gravitational waves are compared with the measured strain sensitivity of Advanced LIGO and VIRGO, corresponding to the latest detected events of gravitational waves. The results show tight constraints on $β$ and $n$. Also, the obtained constraints indicate that special types of the potential of inflation, prototype, and KKLTI models, which are originated from string theory, are more suitable than other models. Our analysis shows that there exist some more chances for the detection of relic gravitational waves.

astro-ph.CO↗

arXiv2021

Aschenbach effect for spinning particles in Kerr-(A)dS spacetime

A non-monotonic behavior of the velocity gradient of a test particle revolving around a rapidly rotating black hole in the locally non-rotating frame of reference is known as the Aschenbach effect. This effect can serve as a distinguishing signature of rapidly rotating black holes, being potentially useful for the measurements of the astrophysical black hole spins. This paper is the generalization of our previous research to the motion of spinning particles around a rotating black hole with non-zero cosmological constant. We show that both the particle's spin $s$ and the cosmological constant $Λ$ modify the critical value of the black hole spin $a_c$, for which the Aschenbach effect can be observed; $a_c$ can increase or decrease depending on the signs of $s$ and $Λ$. We also found that the particle's spin $s$ can mimic the effect of the cosmological constant $Λ$ for a given $a_c$, causing thus a discrepancy in the measurements of $s$, $Λ$ and $a_c$ in the Aschenbach effect.

gr-qc↗

arXiv2020

Aschenbach effect for spinning particles in Kerr spacetime

The orbital velocity profile of circular timelike geodesics in the equatorial plane of a Kerr black hole has a non-monotonic radial behavior, provided that the spin parameter $a$ of the black hole is bigger than a certain critical value $a_c \approx 0.9953 M$. Here the orbital velocity is measured with respect to the Locally Non-Rotating Frame (LNRF), and the non-monotonic behavior, which is known as the Aschenbach effect, occurs only for co-rotating orbits. Using the Mathisson-Papapetrou-Dixon equations for a massive spinning particle, we investigate the Aschenbach effect for test particles with spin. In addition to the black-hole spin, the absolute value of the particle's spin and its orientation (parallel or anti-parallel to the black-hole spin) also play an important role for the Aschenbach effect. We determine the critical value $a_c$ of the spin parameter of the Kerr black hole where the Aschenbach effect sets in as a function of the spin of the probe. We consider not only black holes ($a^2 \le M^2$) but also naked singularities ($a^2>M^2$). Whereas for spinless (geodesic) particles the orbital velocity is always monotonically decreasing if the motion is counter-rotating, we find that for spinning particles in counter-rotating motion with anti-parallel spin around a naked singularity the orbital velocity is increasing on a certain radius interval.

gr-qc↗

arXiv2020

B-mode Power Spectrum of CMB via Polarized Compton Scattering

In this work, according to some evidence from being an asymmetry in the number density of left and right-handed electrons, $δ_L$, in-universe motivate us to calculate the dominated contribution of this asymmetry in the generation of B-mode power spectrum $C_{ B\,l}^{(S)}$. Note, in the standard cosmological scenario, Compton scattering in the presence of scalar matter perturbation can not generate magnetic like pattern in linear polarization while in the case of polarized Compton scattering, we have shown $C_{B\,l}^{(S)}\propto δ_L^2$. We add up the spectrum of the B-mode generated by the polarized Compton scattering to the spectra produced by weak lensing effects and Compton scattering in the presence of tensor perturbations. The results show a significant amplification in $C_{B\,l}$ in large scale $l<500$ for $δ_L>10^{-6}$ which will be observable in future high resolution B-mode polarization detection. Finally, we have shown that $C_{ B\,l}^{(S)}$ generated by polarized Compton scattering can suppress the tensor to scalar ratio, $r$ parameter so that this contamination can be comparable to a primordial tensor-to-scalar ratio spatially for $δ_L>10^{-5}$.

astro-ph.CO↗

arXiv2019

Curvature and topology dependency of the cosmological spectra

In this article we investigate dependency of the adiabatic and entropy spectral indices of the cosmological perturbations on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e. radiation-dust mixture era. For this purpose, we first extract an explicit equation describing evolution of the comoving curvature perturbation in the FLRW universe with arbitrary spatial sectional curvature. We may percept when $K\neq 0$, curvature scale would be as significant as the perturbations scales to recognize the behavior of the spectral indices. We also focus on the entropy perturbation in order to extract behavior of the isocurvature spectral index in terms of the curvature index and time. Our analysis shows that spectra of curvature and entropy perturbations in sub-horizon scales could be function of topology. Moreover, an accurate analysis makes clear that time-average of isocurvature index in case $K=0$ is about zero,so that imprint of entropy perturbation in time duration may be negligible. We also consider evolution of the cosmological indices for super-curvature modes in the case $K=-1$. In the most results dependency to curvature, initial conditions and scale modes are thoroughly vivid.

gr-qc↗

arXiv2018

Generation of Circular Polarization of CMB via Polarized Compton Scattering

The standard scenario of cosmology predicts a measurable amount for linear polarization of the Cosmic Microwave Background radiation (CMB) via Thomson scattering, while through this scenario, the generation of circular polarization is excluded. On the another hand, the circular polarization of CMB has not been excluded in observational evidence. The generation of CMB photons circular polarization via their Compton scattering with polarized cosmic electrons is considered in this paper. Our motivation for considering polarized Compton scattering comes from the effects of the external magnetic field in large scale, the chiral magnetic instability and new physics interactions of the cosmic electrons. It is shown that damping term of polarized Compton scattering in the presence of scalar perturbation can generate circular polarization in CMB radiation, so that the power spectrum of circular polarization of CMB $C_l^{V(S)}$ is proportional to the power spectrum of temperature anisotropy of CMB $C_l^{I(S)}$ and also $δ^2$ which is a fraction of polarized electron number density to the total one with net Left- or Right-handed polarizations. We have discussed that at least we need $δ<10^{-4}$ to find consistency with a reported upper limit of CMB circular polarization.

astro-ph.CO↗