arXiv subjects
Publications and source records attributed to Maxim Dvornikov.
In this work, we employ Ordinary Differential Equation solution method to study neutrino spin oscillations in the case when they are gravitationally scattered off a rotating Kerr black hole. Previously, this problem involved the integral solution of the Hamilton-Jacobi equation. We analyze the consistency of these two methods.
We analyze the possibility to construct propagators of flavor neutrinos, which are particles with indefinite masses. This kind of propagators was used previously while studying neutrino flavor oscillations in frames of the quantum field theory (QFT) based approach. Starting with the operator and the path integral formulations of the QFT, we obtain that the naive derivation of propagators for flavor neutrinos violates the basic principles of the QFT. Nevertheless, we can still construct the effective propagator of flavor neutrinos considering the mass mixing term as a perturbation. In this situation, the effective propagator arises from the solution of a Dyson-like equation. We use the derived effective propagator to rederive the quantum mechanical transition probability for neutrino oscillations in vacuum in frames of the QFT. The application of the obtained results to neutrino oscillations in background matter is also considered.
We study the emission of Cherenkov plasmons by the gas of neutrinos with a nonzero temperature and a chemical potential. The background plasma, consisting of charged leptons, is taken to be nonrelativistic. The energy emission rate is obtained for longitudinal plasmons. To get the neutrino emissivity we average quantum field theory matrix element over the distribution functions of incoming and outgoing particles. Our results are applied for the description of the cooling down of a neutrino cluster formed in the early universe. Such clusters can exist owing to the neutrino interaction with a hypothetical light scalar boson. Using particular cluster parameters, we demonstrate that the considered cooling mechanism is efficient for some clusters. We find the temperature range where the proposed cooling channel is valid. Some useful calculations of the polarization tensor, as well as the plasmon form factors and their dispersion relations are also provided.
We study the spin-flavor precession of neutrinos in a magnetic field within the quantum field theory approach in which neutrinos are virtual particles. Neutrinos are taken to be Majorana particles having a nonzero transition magnetic moment. We derive the dressed propagators of the neutrino mass eigenstates exactly accounting for the magnetic field contribution. The matrix element and the transition probability for the spin-flavor precession are obtained in the approximation of the forwardly scattered charged leptons. The leading term in the transition probability is shown to coincide with the result of the standard quantum mechanical description of neutrino oscillations. We also discuss the quantum field theory contributions to the neutrino dressed propagators and demonstrate that these contributions result in a small correction to the transition probability. The case of charged leptons with arbitrary energies is considered.
We study the evolution of neutrinos electroweakly interacting with a rotating matter. The description of neutrinos is based on the Dirac equation in the corotating noninertial frame where matter is at rest. We find solution of this Dirac equation, where the matter angular velocity is accounted for exactly, for massless neutrinos. In case of massive particles, this solution is obtained for a slowly rotating matter. Our findings are compared with previous research. We consider two applications of our results. First, we compute the electroweak contribution to the vector current of neutrinos along the rotation axis, which is analogous to the chiral vortical effect. This current is shown to be nonzero for both massless and massive particles. Then, we take into account the nonzero mixing between different mass eigenstates. It allows us to study neutrino flavor oscillations in rotating matter and account for noninertial effects. We derive the transition probability which reveals the resonance. These findings generalize the description of neutrino oscillations in a nonmoving matter. Some astrophysical applications are briefly discussed.
We study neutrino oscillations in external fields using the approach based on the quantum field theory (QFT). Neutrinos are virtual particles in this formalism. Neutrino mass eigenstates are supposed to be Dirac fermions. We consider two cases of external fields: the neutrino electroweak interaction with background matter and the interaction with an external magnetic field owing to the presence of the transition magnetic moment. The formalism used involves the dressed propagators of mass eigenstates in external fields. In the matter case, finding of these propagators for Dirac neutrinos has certain difficulties compared to the Majorana particles considered previously. These difficulties are overcome by regularizing the effective potential of the neutrino interaction with matter. The QFT formalism application to the spin-flavor precession also encounters certain peculiarities in the Dirac case compared to the Majorana one. They are related to the observability of right polarized Dirac neutrinos. We derive the matrix elements and the probabilities for Dirac neutrinos interacting with both types of external fields. In case of the spin-flavor precession, we obtain the small QFT contribution to the probabilities in addition to the prediction of the quantum mechanical approach.
We review the applications of the quantum field theory (QFT) for the description of massive Dirac neutrinos in external fields. Two particular cases of external background are considered. First, we examine neutrinos in background matter. Then, we study neutrinos with anomalous magnetic moments in a magnetic field. In both situations, we derive the operator valued neutrino wavefunctions, accounting for external fields, which obey the canonical anticommutation relations. Then, we check that the total energy and momentum of a neutrino field have the appropriate forms. Using the exact solution in a Dirac equation in a magnetic field, we also derive the propagator for a massive Dirac neutrino in this external background. The results obtained are of importance for the QFT application to neutrino oscillations in external fields.
We study neutrino flavor oscillations using the approach based on the quantum field theory (QFT), where neutrinos are taken to be virtual particles. One deals with the propagators of neutrino mass eigenstates in this formalism. Previously, while applying this approach to neutrino oscillations in external fields, we decomposed the propagators and used only the particle contribution in the calculation of the matrix element. In the present work, we carefully justify the validity of this kind of transformation by considering neutrino oscillations in vacuum. In principle, the results obtained can be extended for the QFT applied to neutrino oscillations in external fields.
In this work, we study the propagation and spin oscillations of neutrinos in their scattering by a supermassive black hole (SMBH) surrounded by a realistic accretion disk. We review various descriptions of the fermion spin evolution in a curved spacetime under the influence of external fields. The overview of the test particle motion in the gravitational field of a rotating SMBH is also present. The external fields which a neutrino spin interacts with are the electroweak forces in plasma and the toroidal magnetic field in the accretion disk surrounding SMBH. Spin precession of neutrinos, which are supposed to be Dirac particles, is caused by the interaction of the neutrino magnetic moment with the magnetic field in the disk. We use a semi-analytical model of a thick accretion disk and review its characteristics. The cases of co-rotating and counter-rotating disks with respect to BH are discussed. We consider the incoming flux of neutrinos having an arbitrary angle with respect to the BH spin since the recent results of the Event Horizon Telescope indicate that the BH spin in the galactic center is not always perpendicular to the galactic plane. For our study, we consider a large number of incoming test neutrinos. We briefly discuss our results and their applications in the observations of astrophysical neutrinos.
In this work, we study neutrino spin oscillations in the case when they are gravitationally scattered off a rotating Kerr black hole surrounded by a thick magnetized accretion disk. We consider only toroidal magnetic field inside the disk. Neutrino spin precession is caused by the interaction of the neutrino magnetic moment with the magnetic field in the disk. Our treatment of the spin oscillations of the observed neutrino fluxes is based on numerical simulations of the propagation of a large number of incoming test neutrinos using High Performance Parallel Computing. We briefly discuss our results and their applications in the observations of astrophysical neutrinos.
We study spin oscillations of neutrinos in relativistic moving matter inside an accretion disk. These neutrinos are gravitationally scattered off a spinning Kerr black hole surrounded by a thick accretion disk. The disk can co-rotate and counter-rotate with respect to BH spin. We perform numerical simulations of the propagation of a large number of incoming test neutrinos. We briefly discuss our results.
We study massive Majorana neutrinos in background matter. Representing these particles in terms of Weyl spinors, we carry out their quantization. The propagators of these fields are also constructed. Then, we apply the Hamilton dynamics based formalism to describe massive Majorana neutrinos in matter on the classical level. Finally, we study a classical Dirac particle in vacuum, described with $c$-number variables, within the Hamiton formalism. Such a Dirac field is also canonically quantized.
We study the evolution of interacting large scale magnetic and axionic fields. Based on the new induction equation accounting for the contribution of spatially inhomogeneous axions, we consider the evolution of a magnetized spherical axion structure. Using the thin layer approximation, we derive the system of the nonlinear ordinary differential equations for harmonics of poloidal and toroidal magnetic fields, as well as for the axion field. In this system, we account for up to four modes. Considering this small and dense axion clump to be in a solar plasma, we numerically simulate the evolution of magnetic fields. We obtain that the behavior of magnetic fields depends on the initial fields configuration. Moreover, we find an indication on a magnetic field instability in the magnetohydrodynamics with inhomogeneous axions.
We study neutrino oscillations in background matter within the quantum field theory formalism where neutrino mass eigenstates are virtual particles. In this case, neutrino mass eigenstates are mixed owing to the interaction with matter. Assuming that neutrinos are Majorana particles, we find the exact propagators for massive neutrinos accounting for the interaction with matter by solving the analog of the Dyson equation. These propagators are used to calculate the transition probability which coincides with the prediction of the standard quantum mechanical treatment of neutrino flavor oscillations in uniform matter. Finally, we analyze the approximations made in our analysis.
We summarize our recent achievements in the description of neutrino oscillations in various gravitational fields. After the short review of the previous studies of neutrinos in gravitational fields, we consider the neutrinos propagation and oscillations in two gravitational backgrounds. First, we discuss neutrino spin oscillations in their gravitational scattering off a supermassive black hole surrounded by a thick magnetized accretion disk. Second, we study neutrino flavor oscillations in stochastic gravitational waves. We also consider applications of the obtained results for oscillations of astrophysical neutrinos.
We study neutrino spin oscillations while the particles scatter off a rotating black hole surrounded by a thick magnetized accretion disk. Neutrino spin precession is caused by the interaction of the neutrino magnetic moment with the magnetic field in the disk which has both toroidal and poloidal components. Our calculation of the observed neutrino fluxes, accounting for spin oscillations, are based on numerical simulations of the propagation of a great number of incoming test particles using High Performance Parallel Computing. The obtained results significantly improve our previous findings. We briefly discuss the applications for the observations of astrophysical neutrinos.
We study the time evolution of magnetic fields in various configurations of spatially inhomogeneous pseudoscalar fields, which are the coherent superposition of axions. The new induction equation for the magnetic field, which accounts for this inhomogeneity, is derived for such systems. Based on this equation, we study, first, the evolution of two Chern-Simons (CS) waves interacting with a linearly decreasing pseudoscalar field. The nonzero gradient of the pseudoscalar field results in the mixing between these CS waves. Then, we consider the problem in a compact domain, when an initial CS wave is mirror symmetric. In this situation, the inhomogeneity of a pseudoscalar field acts as the effective modification of the $α$-dynamo parameter. Thus, we conclude that the influence of a spatially inhomogeneous pseudoscalar field on the magnetic field evolution strongly depends on the geometry of the system.
We study the formation of a superfluid condensate of neutrinos inside a neutrino cluster. The attractive interaction between neutrinos is mediated by a scalar boson which is lighter than a neutrino. We consider the appearance of neutrino bound states consisting of particles with oppositely directed spins. The gap equation for such a system is derived. Based on numerical simulations of the neutrino distribution in a cluster, we find the phase transition temperature and the coherence length inside such a cluster for various parameters of the system. The constraints on the parameters of the Yukawa interaction, resulting in the neutrino superfluidity, are derived. We obtain that the cosmic neutrino background can contribute to the superfluid condensate inside a neutrino cluster having realistic characteristics. The mechanism of the neutrino cluster cooling in the early universe, based on the plasmons Čerenkov radiation, is proposed.