arXiv subjects

Artem Popov

Publications and source records attributed to Artem Popov.

11 recordsLinked to original sources

arXiv2026

Wave packet description of Majorana neutrino oscillations in a magnetic field

Majorana neutrino oscillations in a magnetic field are considered using the wave packets formalism. The modified Dirac equation for Majorana neutrinos with non-zero transition magnetic moments propagating in a magnetic field is solved analytically in the two flavour case. The expressions for the oscillations probabilities are derived accounting for the decoherence effect emerging at distances exceeding the coherence length. It is shown that for Majorana neutrinos propagating in a magnetic field the coherence length coincides with the coherence length for neutrino oscillations in vacuum when the vacuum frequency is much greater than the magnetic frequency ($ω_{vac} \gg ω_B$), while it is proportional to the cube of the average neutrino momentum if ($ω_{vac} \ll ω_B$). We show that the decoherence effect may appear during neutrino propagation in a magnetic field of supernova.

hep-ph↗

arXiv2025

Three-flavour neutrino oscillations in a magnetic field

In this paper we study Dirac and Majorana neutrino oscillations in a magnetic field in the three-flavour case. A theoretical framework developed in \cite{Popov:2019} is extended to the case of three neutrino species, as well as to the Majorana neutrinos case. The closed expression for the Dirac neutrinos flavour and spin oscillations are given. Majorana neutrino oscillations are studied numerically. We show that the probabilities exhibit a complicated interplay of oscillation on magnetic $μ_νB$ and vacuum $Δm^2_{ij}/2p$ frequencies. It is also shown that neutrino oscillations in an interstellar magnetic field can modify neutrino fluxes observed in neutrino telescopes.

hep-ph↗

arXiv2025

High-energy neutrinos flavour composition as a probe of neutrino magnetic moments

Neutrino propagation in the Galactic and extragalactic magnetic fields is considered. We extend an approach developed in \cite{Popov:2019nkr} to describe neutrino flavour and spin oscillations using wave packets. The evolution equations for the neutrino wave packets in a uniform and non-uniform magnetic fields are derived. The analytical expressions for neutrino flavour and spin oscillations probabilities accounting for damping due to the wave packet separation are obtained for the case of a uniform magnetic field. It is shown that terms in the flavour oscillations probabilities that depend on the magnetic field strength are characterized by two coherence lengths. One of the coherence lengths coincides with the coherence length for neutrino oscillations in vacuum, while the second one is proportional to the cube of the average neutrino momentum $p_0^3$. The probabilities of flavour and spin oscillations are calculated numerically for neutrino interacting with the non-uniform Galactic magnetic field. It is shown that oscillations on certain frequencies are suppressed on the Galactic scale due to the neutrino wave packets separation. The flavour compositions of high-energy neutrino flux coming from the Galactic centre and ultra-high energy neutrinos from an extragalactic sourse are calculated accounting for neutrino interaction with the magnetic field and decoherence due to the wave packet separation. It is shown that for neutrino magnetic moments $\sim 10^{-13} μ_B$ and larger these flavour compositions significantly differ from ones predicted by the vacuum neutrino oscillations scenario.

hep-ph↗

arXiv2024

Wave packet treatment of neutrino flavour and spin oscillations in galactic and extragalactic magnetic fields

We consider neutrino flavour and spin oscillations in a magnetic field using formalism of wave packets. Decoherence effects due to neutrino wave packets separation are studied. The considered effects are especially important for describing astrophysical neutrino oscillations, since they propagate on kiloparsec scale and bigger. The obtained results are of interest for neutrino telescopes IceCube, Baikal-GVD and KM3NeT, and also can be applied for description of supernovae neutrino oscillations effects would be detected by JUNO and Hyper-Kamiokande.

hep-ph↗

arXiv2023

Oscillations of Majorana neutrinos in supernova and CP violation

Leptonic CP violation is one of the most important topics in neutrino physics. CP violation in the neutrino sector is strongly related to the nature of neutrinos: whether they are Dirac or Majorana particles. In \cite{Popov:2021icg} we have shown that for Majorana neutrinos arance of nonzero Majorana CP-violating phases combined with strong magnetic field during supernova core-collaple can induce new resonances in neutrino oscillations, for example in $ν_e \to \barν_τ$ channel. In this contribution we further study new resonances in Majorana neutrino oscillations, in particular energy dependence of amplitudes of these resonances. Our findings suggest a potential astrophysical setup for studying the nature of neutrino masses and leptonic CP violation and may be important for future neutrino experiments, such as JUNO, Hyper-Kamiokande and DUNE.

hep-ph↗

arXiv2021

Manifestations of non-zero Majorana CP violating phases in oscillations of supernova neutrinos

We investigate effects of non-zero Dirac and Majorana CP violating phases on neutrino-antineutrino oscillations in a magnetic field of astrophysical environments. It is shown that in the presence of strong magnetic fields and dense matter, non-zero CP phases can induce new resonances in the oscillations channels $ν_e \leftrightarrow \barν_e$, $ν_e \leftrightarrow \barν_μ$ and $ν_e \leftrightarrow \barν_τ$. We also consider all other possible oscillation channels with $ν_μ$ and $ν_τ$ in the initial state. The resonances can potentially lead to significant phenomena in neutrino oscillations accessible for observation in experiments. In particular, we show that neutrino-antineutrino oscillations combined with Majorana-type CP violation can affect the $\barν_e$/$ν_e$ ratio for neutrinos coming from the supernovae explosion. This effect is more prominent for the normal neutrino mass ordering. The detection of supernovae neutrino fluxes in the future experiments, such as JUNO, DUNE and Hyper-Kamiokande, can give an insight into the nature of CP violation and, consequently, provides a tool for distinguishing the Dirac or Majorana nature of neutrinos.

hep-ph↗

arXiv2020

Neutrino eigenstates and flavour, spin and spin-flavour oscillations in a constant magnetic field

We develop the approach to the problem of neutrino oscillations in a magnetic field introduced in \cite{Popov:2019nkr} and extend it to the case of three neutrino generations. The theoretical framework suitable for computation of the Dirac neutrino spin, flavour and spin-flavour oscillations probabilities in a magnetic field is given. It is shown that there is an entanglement between neutrino flavour and spin oscillations and in the general case it is not possible to consider these two types of neutrino oscillations separately. The closed analytic expressions for the probabilities of oscillations are obtained accounting for the normal and inverted hierarchies and the possible effect of CP violation. In particular, it is shown that the probabilities of the conversions without neutrino flavor change, i.e. $ν_e^L \rightarrow ν_e^L$ and $ν_e^L \rightarrow ν_e^R$, do not exhibit the dependence on the CP phase, while the other neutrino conversions are affected by the CP phase. In general, the neutrino oscillation probabilities exhibit quite a complicated interplay of oscillations on the magnetic $μ_ν B$ and vacuum frequencies. The obtained results are of interest in applications to neutrino oscillations under the influence of extreme astrophysical environments, for example peculiar to magnetars and supernovas, as well as in studying neutrino propagation in interstellar magnetic fields.

hep-ph↗

arXiv2019

Neutrino eigenstates and flavour, spin and spin-flavour oscillations in a constant magnetic field

We further develop a recently proposed new approach to the description of the relativistic neutrino flavour $ν_e^L \leftrightarrow ν_μ^L$, spin $ν_e^L \leftrightarrow ν_{e}^R$ and spin-flavour $ν_e^L \leftrightarrow ν_μ^R$ oscillations in a constant magnetic field that is based on the use of the exact neutrino stationary states in the magnetic field. The neutrino flavour, spin and spin-flavour oscillations probabilities are calculated accounting for the whole set of possible conversions between four neutrino states. In general, the obtained expressions for the neutrino oscillations probabilities exhibit new inherent features in the oscillation patterns. It is shown, in particular, that: 1) in the presence of the transversal magnetic field for a given choice of parameters (the energy and magnetic moments of neutrinos and the strength of the magnetic field) the amplitude of the flavour oscillations $ν_e^L \leftrightarrow ν_μ^L$ at the vacuum frequency is modulated by the magnetic field frequency, 2) the neutrino spin oscillation probability (without change of the neutrino flavour) exhibits the dependence on the mass square difference $Δm^2$. It is shown that the discussed interplay of neutrino oscillations in magnetic fields on different frequencies can have important consequences in astrophysical environments, in particular in those peculiar for magnetars.

hep-ph↗

arXiv2019

Neutrino oscillations and exact eigenstates in magnetic field

hep-ph↗

arXiv2018

Neutrino motion and spin oscillations in magnetic field and matter currents

A brief review of a neutrino oscillations effect in an external magnetic field and matter currents is given. An ultra-relativistic neutrino propagation in moving external media is investigated. We have found a new spin operator which commutes with the corresponding Hamiltonian, exact wave functions and energy spectrum are obtained.

hep-ph↗

arXiv2017

Interpretable probabilistic embeddings: bridging the gap between topic models and neural networks

We consider probabilistic topic models and more recent word embedding techniques from a perspective of learning hidden semantic representations. Inspired by a striking similarity of the two approaches, we merge them and learn probabilistic embeddings with online EM-algorithm on word co-occurrence data. The resulting embeddings perform on par with Skip-Gram Negative Sampling (SGNS) on word similarity tasks and benefit in the interpretability of the components. Next, we learn probabilistic document embeddings that outperform paragraph2vec on a document similarity task and require less memory and time for training. Finally, we employ multimodal Additive Regularization of Topic Models (ARTM) to obtain a high sparsity and learn embeddings for other modalities, such as timestamps and categories. We observe further improvement of word similarity performance and meaningful inter-modality similarities.

cs.CL↗