arXiv subjects

D. V. Chubukov

Publications and source records attributed to D. V. Chubukov.

8 recordsLinked to original sources

arXiv2026

Vacuum photon emission and mean electromagnetic field in pair-creating external backgrounds

We develop a perturbative description of vacuum radiative processes in quantum electrodynamics with a prescribed external electromagnetic background capable of producing electron-positron pairs. Since the initial vacuum is then unstable and the in- and out-vacua are inequivalent, radiative observables require a real-time formulation beyond the ordinary in-out approach of vacuum-stable QED. Using the Keldysh-Schwinger-Fradkin nonequilibrium technique, we derive the mean number density of emitted photons through the second nonvanishing order in the fine-structure constant. The leading term, of order $α$, reproduces the known vertex and tadpole mechanisms, while the complete order-$α^2$ correction contains interference, loop, and induced-current contributions. We also give an independent derivation based on the spectral decomposition of the identity operator in the in-Fock space, where the photon number density is represented as a sum of squared transition amplitudes and vacuum-disconnected terms are canceled by the optical theorem generalized to an unstable vacuum. In addition, we compute the mean electromagnetic field through order $e^3$, including the electromagnetic dressing of the induced vacuum current, and verify it using the corresponding Schwinger-Dyson equations. The final formulas are expressed in terms of exact solutions and propagators of the Dirac equation in the external background and apply to general spacetime-dependent field configurations.

hep-th↗

arXiv2026

Axion-Exchange Contribution to the Energy of Lithium-Like Ions

Axions and axion-like particles are among the most promising candidates for dark matter and for manifestations of new physics beyond the Standard Model. In the present work, the contribution of axion exchange to the energy of lithium-like ions is investigated within the framework of relativistic bound-state quantum electrodynamics. A formalism for the interelectronic interaction mediated by axion exchange is developed in the Furry picture with finite nuclear size taken into account. Energy shifts are calculated for a wide range of nuclear charge numbers $Z$ and axion masses. The magnitude of the axion-induced contribution is shown to increase with increasing $Z$ for all states considered. Based on the analysis of lithium-like bismuth, constraints on the axion-electron interaction parameters are obtained in the high-mass region. The results indicate that precision spectroscopy of highly charged ions is a promising tool for searches for new physics associated with the exchange of pseudoscalar bosons.

physics.atom-ph↗

arXiv2025

$\mathcal{T}$, $\mathcal{P}$-odd electron-nucleon interaction via a Higgs-boson exchange at the quark-gluon level

The electron pseudoscalar -- nucleon scalar $\mathcal{T}$,~$\mathcal{P}$-odd interaction within the framework of the Standard Model is considered as an exchange mediated by the Higgs boson at the quark-gluon level. $\mathcal{CP}$ violation is introduced through a phase factor in the Cabibbo-Kobayashi-Maskawa matrix, which characterizes the flavor structure of the quark loop. We explicitly demonstrate that the total three-loop contribution vanishes for the Higgs boson exchange mechanism. A nonzero contribution appears at the four-loop quark-gluon level only with the insertion of an additional gluon line between the quarks. The estimate of the $\mathcal{CP}$-odd electron-nucleon interaction coupling constant after reduction of divergencies of the quark loop integral using the Glashow-Iliopoulos-Maiani (GIM) mechanism yields a value $ \sim10^{-28}$. The final result, expressed in terms of the equivalent electron electric dipole moment ($e$EDM), is $10^{-48} \,\, e\text{cm}$, and its order of magnitude coincides with that of the GIM estimate of the $e$EDM at the quark-gluon level. Our parametric estimate of the $e$EDM differs from previous studies by a factor that depends on the mass of the $b$ quark.

hep-ph↗

arXiv2021

$\mathcal{P}$, $\mathcal{T}$-odd Faraday rotation in intracavity absorption spectroscopy with molecular beam as a possible way to improve the sensitivity of the search for the time reflection noninvariant effects in nature

The present constraint on the space parity ($\mathcal{P}$) and time reflection invariance ($\mathcal{T}$) violating electron electric dipole moment ($e$EDM) is based on the observation of the electron spin precession in an external electric field using the ThO molecule. We propose an alternative approach: observation of the $\mathcal{P}$,~$\mathcal{T}$-odd Faraday effect in an external electric field using the cavity-enhanced polarimetric scheme in combination with a molecular beam crossing the cavity. Our theoretical simulation of the proposed experiment with the PbF and ThO molecular beams shows that the present constraint on the $e$EDM in principle can be improved by a few orders of magnitude.

physics.atom-ph↗

arXiv2019

$\mathcal{P}$,$\mathcal{T}$-odd Faraday rotation on atoms and molecules in intra-cavity absorption spectroscopy as an alternative way to search for the $\mathcal{P}$,$\mathcal{T}$-odd effects in nature

Present limit on the electron electric dipole moment ($e$EDM) is based on the electron spin precession measurement. We propose an alternative approach - observation of the $\mathcal{P}$,$\mathcal{T}$-odd Faraday effect in an external electric field on atoms and molecules using cavity-enhanced polarimetric scheme in combination with molecular (atomic) beam crossing the cavity. Our calculations of the effective electric fields and theoretical simulation of the proposed experiment on Tl and Pb atoms, PbF, YbF, ThO, and YbOH show that the present limit on the $e$EDM can be improved by 6-7 orders of magnitude.

physics.atom-ph↗

arXiv2019

Accurate Evaluation of $\mathcal{P}$,$\mathcal{T}$-odd Faraday Effect in Atoms of Xe and Hg

Accurate evaluation of the $\mathcal{P}$,$\mathcal{T}$-odd Faraday effect (rotation of the polarization plane for the light propagating through a medium in presence of an external electric field) is presented. This effect can arise only due to the $\mathcal{P}$,$\mathcal{T}$-odd interactions and is different from the ordinary Faraday effect, i.e. the light polarization plane rotation in an external magnetic field. The rotation angle is evaluated for the ICAS (intracavity absorption spectroscopy) type experiments with Xe and Hg atoms. The results show that Hg atom may become a good candidate for a search for the $\mathcal{P}$,$\mathcal{T}$-odd effects in atomic physics.

physics.atom-ph↗

arXiv2016

P,T-odd Faraday effect as a tool for observation of CP violation in Standard Model

It is proposed to employ the P,T-odd Faraday effect, i.e. rotation of the polarization plane of the light propagating through a medium in presence of the electric field, as a tool for observation of P,T-odd effects caused by CP violation within the Standard Model. For this purpose the vapors of heavy atoms like Tl, Pb, Bi are most suitable. Estimates within the Standard Model show: provided that applied field is about 10^5 V/cm and the optical length can be as large as 70000 km, the rotation angle may reach the value corresponding to the recently observable values (10^{-9} rad). These estimates demonstrate that the P,T-odd Faraday effect observations may effectively compete with the recent measurements of the electron spin rotation in an external electric field, performed with diatomic molecules. These measurements exclude the P,T-odd effects at the level 9 orders of magnitude higher than the predictions of the Standard Model.

physics.atom-ph↗

arXiv2014

The electric dipole moment of an electron in H-like ions in an electrostatic storage ring

Theoretical studies are presented how the electric dipole moment (EDM) of the electron in H-like ions in electrostatic storage rings can sensitively be determined. With the proposed experiments a new constraint of about $10^{-29}$ e cm for the electron EDM can be established what is by an order of magnitude more restrictive than the existing bounds. Experiments with H-like ions may provide a possibility to distinguish between the electron EDM effect and the effect of P,T violating interaction between the atomic electron and the nucleus.

physics.atom-ph↗