Vacuum polarization by a Coulomb center and a strong magnetic field. Uehling's correction

The problem of vacuum polarization by the Coulomb field of the nucleus and a constant homogeneous magnetic field is examined by the proper time method. For this the magnetic field is exactly taken into account, and the Coulomb field is considered by perturbation theory. In the case of a magnetic field equal to zero, we calculate the change of the Coulomb potential which results from vacuum polarization. The result obtained coincides with the well-known Uehling correction.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 86–92, September 1986.     

Vectons in a Coulomb field

The problem is solved within the framework of an approach developed by the author. The author believes this approach to be free of deficiencies characteristic of theories for particles with unit and larger spins. We derive integrals of motion, separate variables, derive radial-state equations, and then solve them. We find coupled particle states; these are vector atoms that may be observed in nature. They possess a discrete energy spectrum similar to that of electrons in hydrogen atoms as seen in Dirac theory. We also note cases of particle repulsion from the center of fields, zero rest mass, and elementary free motion.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 107–111, November, 1991.     

Vacuum polarization by a Coulomb center and strong magnetic field. modification of Coulomb's law

The proper time method is used to examine the effect of polarization of the electron-positron vacuum on the nature of the interaction of a charged particle with the field of a nucleus and a magnetic field. It is shown that the interaction of an electron with a nucleus becomes anisotropic in the presence of a magnetic field. The dielectric constants of the vacuum and the effective charge of the Coulomb center are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 38–45, November, 1986.     

Higher corrections in the theory of vacuum polarization by an isotropic gravitational field

A version of the effective Lagrangian method is proposed, which proves to be more effective than the well-known Schwinger-de Witt method for solving self-consistent problems concerning polarization of the matter field vacuum by an isotropic gravitational field. The main result of the paper is computation of polarizationinduced corrections of fourth order in space-time curvature and its derivatives, for scalar and vector massive fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 61–68, October, 1989.The authors thank K. A. Bronnikov, V. N. Lukash, V. N. Mel'nikov, V. N. Ponomarev, A. A. Starobinskii, and V. P. Frolov for many useful discussions of the results of this paper.     

Renormalization of the two-photon vacuum polarization and the self energy vacuum polarization for a tightly bound electron

The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ) is used in order to derive the renormalized energy shift due to the gauge invariant K?llén-Sabry diagram of the two-photon vacuum polarization (VPVP) as well as the self energy vacuum polarization S(VP)E beyond the Uehling approximation. It is outlined, that no outer renormalization is required for the two-photon vacuum polarization and that only the inner renormalization has to be accomplished. It is shown that the so-called nongauge invariant spurious term is absent for a wide class of vacuum polarization (VP) diagrams if one applies the widely used spherical expansion of bound and free-electron propagator. This simplifies significantly calculations in bound state quantum electrodynamics. As one result of our paper the use of the BPHZ-approach in bound state QED is established. Received 28 September 2001     

Coulomb formation and evolution of muonium in vacuum

An exact calculation ofμ ⁺ e ^? Coulomb capture cross sections at various energies in the centre-of-mass system is reported. The population of 1s, 2s and 2p levels as function of the time elapsed after muonium formation is shown.     

Influence of temperature on strain-induced polarization Coulomb field scattering in AIN/GaN heterostructure field-effect transistors

Electron mobility scattering mechanism in AlN/GaN heterostuctures is investigated by temperature-dependent Hall measurement, and it is found that longitudinal optical phonon scattering dominates electron mobility near room temperature while the interface roughness scattering becomes the dominant carrier scattering mechanism at low temperatures （~ 100 K）. Based on measured current-voltage characteristics of prepared rectangular AlN/GaN heterostructure field-effect transistor under different temperatures, the temperature-dependent variation of electron mobility under different gate biases is inves- tigated. The polarization Coulomb field （PCF） scattering is found to become an important carrier scattering mechanism after device processing under different temperatures. Moreover, it is found that the PCF scattering is not generated from the thermal stresses, but from the piezoelectric contribution induced by the electrical field in the thin A1N barrier layer. This is attributed to the large lattice mismatch between the extreme thinner AlN barrier layer and GaN, giving rise to a stronger converse piezoelectric effect.     

Influence of temperature on strain-induced polarization Coulomb field scattering in AlN/GaN heterostructure field-effect transistors

Electron mobility scattering mechanism in AlN/GaN heterostuctures is investigated by temperature-dependent Hall measurement, and it is found that longitudinal optical phonon scattering dominates electron mobility near room temperature while the interface roughness scattering becomes the dominant carrier scattering mechanism at low temperatures(～100 K).Based on measured current–voltage characteristics of prepared rectangular AlN/GaN heterostructure field-effect transistor under different temperatures, the temperature-dependent variation of electron mobility under different gate biases is investigated. The polarization Coulomb field(PCF) scattering is found to become an important carrier scattering mechanism after device processing under different temperatures. Moreover, it is found that the PCF scattering is not generated from the thermal stresses, but from the piezoelectric contribution induced by the electrical field in the thin AlN barrier layer. This is attributed to the large lattice mismatch between the extreme thinner AlN barrier layer and GaN, giving rise to a stronger converse piezoelectric effect.     

Splitting of a high-energy photon in a strong Coulomb field

The helical splitting amplitudes of a high-energy photon in an external Coulomb field are found exactly with respect to Zα. Both screened and unscreened potentials are investigated. The treatment is carried out within the semiclassical approach, which is valid for small angles between the momenta of all photons. A new representation is used for the semiclassical electronic Green’s function. The resulting expressions are analyzed in detail for the case of transverse components of the momenta of the final photons that are large compared with the electron mass. Zh. éksp. Teor. Fiz. 112, 1921–1940 (December 1997)     

Calculated polarization after Coulomb excitation in beam-foil interaction

The excitation of a hydrogen beam by the shielded Coulomb potentials of the ionic cores of an Aufoil is calculated in first Born approximation for a beam velocityv=1.4 a.u. Different formation depths of the final 2p term are considered and weighted with the survival probability. Stokes parameters for the emitted light are compared with He (n=3→ 2) transitions. It is demonstrated that the coherence of the excitation by neighbouring target cores tends to reduce the excitation amplitudes for the 2pm states withm≠0. Adsorbates are estimated to have a considerable effect on the polarization.     

Scattering of a low-energy electron in a strong Coulomb field

The low-energy electron scattering cross section in a strong Coulomb field is analyzed theoretically. It is shown that the exact cross section in a wide energy range significantly differs from the results obtained in the first Born approximation and in the nonrelativistic approximation.     

Structure of the Yang-Mills vacuum in the Coulomb gauge

The non-uniqueness of Yang-Mills potential in the Coulomb gauge leads to a non-trivial vacuum structure featuring vacuum fields of both integer and half-integer topological charge. Instantons fit in consistently with this picture and their interpretation is not charged. Integer and half-integer vacua are connected by certain meron solutions and the existence of half-integer charged states appears to be important for the confinement properties of the theory.     

Two-loop self-energy correction in a strong Coulomb nuclear field

The two-loop self-energy correction to the ground-state energy levels of hydrogen-like ions with nuclear charges Z≥10 is calculated without the Zα expansion, where α is the fine-structure constant. The data obtained are compared with the results of analytical calculations within the Zα expansion; significant disagreement with the analytical results of order α²(Zα)⁶ has been found. Extrapolation is used to obtain the most accurate value for the two-loop self-energy correction for the 1s state in hydrogen.     

One loop vacuum polarization in a locally de Sitter background

We compute the one loop vacuum polarization from massless, minimally coupled scalar QED in a locally de Sitter background. Gauge invariance is maintained through the use of dimensional regularization, whereas conformal invariance is explicitly broken by the scalar kinetic term as well as through the conformal anomaly. A fully renormalized result is obtained. The one loop corrections to the linearized, effective field equations do not vanish when evaluated on-shell. In fact the on-shell one loop correction depends quadratically on the inflationary scale factor, similar to a photon mass. The contribution from the conformal anomaly is insignificant by comparison.