Exchange and correlation potentials in the one-electron equation

The self-energy operator of an electron liquid is examined by including the particle-hole and particle-particle ladder types of vertex corrections to the simplest approximation discussed by Hedin and Lundqvist. It is found that the real part of the self-energy correction ∑(p, ε_p) is much more independent of the wavenumber p than that in the simplest approximation because of the strong short-range correlations at metallic densities. The quasi-particle mass ratio m¹/m in the present approximation gives values smaller than 1 in the whole metallic density region.     

Self-energy correction to the wave function in the effect of parity violation for the amplitude of the 6s–7s transition in the 133Cs atom

The quantum electrodynamic self-energy correction to the wave function in the effect of parity violation for the amplitude of the 6s–7s transition in the ¹³³Cs atom is calculated in explicit form without using the nonrelativistic approximation for the self-energy operator. The result obtained refines some previous estimates and indicates that the correction to the parity violation may be comparable with the corresponding correction to the vacuum polarization. The necessity of taking complete relativistic account of all the quantum electrodynamic corrections in calculations of the electroweak charge Q _W in atomic systems is shown.     

Electron-boson coupling and oxygen-isotope effect in the optical conductivity of high-Tc superconductors

We have investigated electron-boson coupling in the optical conductivity of high-T_c superconductors through the optical self-energy. The real part of the self-energy (ReΣ^op(ω)) of YBa₂Cu₃O_y (YBCO) shows a characteristic doping dependence. In the optimally doped YBCO, ReΣ^op(ω) has a single peak around 65 meV, which corresponds to the kink structure of the band dispersion. On the other hand, in the under-doped YBCO, the peak structure of ReΣ^op(ω) splits into two parts. To evaluate contribution from the phonons in electron-boson coupling, we have measured oxygen-isotope effects by substituting ¹⁶O→¹⁸O for the optimally doped and under-doped YBCO.     

Neutrino Self-Energy and Index of Refraction in Strong Magnetic Field: A New Approach

The Ritus E_p eigenfunction method is extended to the case of spin-1 charged particles in a constant electromagnetic field and used to calculate the one-loop neutrino self-energy in the presence of a strong magnetic field. From the obtained self-energy, the neutrino dispersion relation and index of refraction in the magnetized vacuum are determined within the field range m²_e?eB?M²_W. The propagation of neutrinos in the magnetized vacuum is anisotropic due to the dependence of the index of refraction on the angle between the directions of the neutrino momentum and the external field. Possible cosmological implications of the results are discussed.     

Hodge theory used to produce finite self-energy models of the electron

The relationship between electromagnetic fields and topology is discussed. Hodge theory is generalized to classify static fields in static wormhole models. This generalization is used to show models of the electron exist which have finite self-energy. These models always have 1/R ² electric fields and self-energies of 4πq ²/R ₀, whereR ₀ is the inner radius of the wormhole.     

Influence of nonmagnetic impurities on the kondo effect

The influence of scattering by nonmagnetic impurities is studied in perturbation theory. While the finite lifetime of the electrons in intermediate states due to scattering by nonmagnetic impurities does not lead to a change in the logT-behaviour of the third-order self-energy, certain vertex-corrections give rise to an additional term which varies like 1/√T at low temperatures. Similar correction terms are found to occur in the higher order self-energy contributions. Although these terms diverge more strongly atT=0 than the logarithmic contributions they are quite small at finite temperatures since they depend on the lifetime τ of the electrons through a factor of (? _F τ)^?5/2 (? _F Fermi energy). The possibility of observing these interference effects experimentally is discussed.     

Self-energy analysis of multiple-bosonic mode coupling in Sr2RuO4

We report angle-resolved photoemission spectroscopy studies on Sr₂RuO₄. We observe multiple-bosonic mode coupling in the α and β band dispersions. To extract the self-energy from the data for which the usual fitting methods do not work well, we propose a scheme that exploits the relation between the spectral intensity and self-energy, termed as relative self-energy. The relative self-energy obtained in that way contains important features of the self-energy. We observe not only the features that can be obtained from the band dispersions but also additional features that were not seen.     

Self-consistent approximations for correlation functions in the theory of triplet pairing superfluidity in3He

A self-consistent and “spin conserving” approximation scheme is developed for the two-particle correlation functions in superfluid³He. It is shown that the irreducible vertex part occuring in the Bethe-Salpeter equation for the generalized correlation function (having 4⁴ components) must be equal to the functional derivative of the approximate self-energy part with respect to the Green's function. The theory is specialized to the Hartree-Fock approximation yielding the RPA susceptibility belowT _c . An important feature of the resulting diagrammatic expansion is that the spin-fluctuation effects in the superfluid phase arise from infinite iteration of pairs of anomalous propagators inboth the particle-hole and in the particle-particle channels.     

The general three-vertex,BRS identities and renormalizability of the light-cone gauge

The general one-loop three-vertexГ _μeλ ^abc (p, q, r) in the four-component formulation of the Yang-Mills theory is calculated in the light-cone gauge. The nonvanishing counter Lagrangian constructed from this three-vertex and the self-energy is proportional to the original Lagrangian, the single renormalization constant being -11g² C _YM Г(2?ω)/48π². Gauge dependent and nonlocal counterterms do not contribute to the renormalization constant, but are needed to verify the appropriate Slavnov-Taylor (ST) and Becchi-Rouet-Stora (BRS) identities.     

Electroweak radiative corrections to the e+e− →+− asymmetry

The electromagnetic and purely weak one-loop corrections to e⁺e^? →^+? have been calculated in the SU(2) × U(1) standard model using an on-shell renormalisation scheme with finite Green functions. Thier influence on the forward backward asymmetry A_FB together with soft and hard bremsstrahlung is discussed for PETRA energies. Whereas the electromagnetic corrections to ψ and Z⁰ exchange diminish A_FB, the weak corrections increase A_FB almost compensating the QED correction to Z⁰ exchange. The main weak contribution comes from the Z⁰ self-energy. The other diagrams give only small changes in A_FB.     

Deviation from Kittel's magnetic resonance formula near Tc of CdCr2Se4

Approaching the Curie temperature of the cubic ferromagnet CdCr₂Se₄ from above, the g-factor increasingly shifts from the value predicted by Kittel's formula. In the exchange critical region (susceptibility χ ?1) the g-shift is consistent with δg/g ≈ χ² following from the complex self-energy.     

Fokker-Planck description of Navier-Stokes fluid

The Navier-Stokes equations with random stirring forces studied by Forster et al. are analyzed in the formalism developed recently. It is shown that without an Einstein relation detailed balance is violated. In detailed balance zero-frequency non-renormalization theorems are used to define a general renormalized viscosity v_R and to show the non-renormalization of the 3-point vertex for all wave numbers. Based on the response self-energy calculated to second order, recursion relations for v^?1_K are obtained which are used to rederive the results of Forster et al. for model A.     

Determination of the ground state energies of the H 2 + , D 2 + and H 2 + molecular ions taking into account relativistic corrections

On the basis of determination of the asymptotic behavior of correlation functions of the corresponding field currents with the corresponding quantum numbers an analytic method for determination of the energy spectrum of three-body Coulomb system is suggested. Our results show that the constituent masses of particles, which we have defined as masses of particles in a bound state, differ from masses of particles in a free-state. The constituent mass to the free state mass relation for the electron is greater than the same mass relation for the proton, deuteron and triton. It was also found that this constituent electron mass has different values in each systems, i.e. in H ₂ ⁺ , D ₂ ⁺ and T ₂ ⁺ hydrogen molecular ions. The contributions of exchange and self-energy diagrams were taken into account in the determination of the energy spectrum of the three-body Coulomb system. Our results show that the self-energy diagram contribution is inversely proportional to the square of the constituent mass of particles. This contribution is sufficient for the electron and is negligible for the proton, deuteron and triton. When defining the energy and the wave function (WF), it is necessary to take into account the contributions of both the exchange and self-energy diagrams.     

Crossed diagram contribution to the electron self-energy due to impurity scattering in a magnetic field

We consider the contribution of crossed diagrams to the self-energy for a system of free electrons and fixed point impurities in the presence of a strong magnetic field. At the peaks of the Shubnikov-de Haas (S.d.H.) oscillations the dependence on the impurity concentration of the crossed diagram is the same as in the generalized Born approximation (n _i ^2/3 ). Nevertheless, for the S.d.H. regime the contribution of the crossed diagrams is shown to be unimportant.     

Description of the pressure-induced insulator-metal transition in BaCoS2 within the LDA + DMFT approach

The pressure-induced insulator-metal transition in paramagnetic sulfide BaCoS₂ at a temperature of 370 K has been described for the first time using the combination of the local electron density approximation and the dynamic mean field theory (LDA + DMFT). Based on the analysis of the spectral functions of Co 3d orbitals, the local magnetic moments of Co, and the frequency dependence of the imaginary part of the self-energy, the existence of the insulator-metal transition for 97% of the BaCoS₂ unit cell volume at normal pressure has been established. Simultaneously, the high-to-low spin magnetic transition of Co²⁺ ions occurs.     

High Z effects in accounting for radiative component of the electron magnetic moment in hydrogen-like atoms

The behavior of electron energy levels in hydrogen-like atoms is studied while taking into account the nonperturbative interaction between the radiative component of the magnetic moment of a free electron Δg _free and the Coulomb field of an atomic nucleus with charge Z, including those with Z > 137. It is shown that for Zα ? 1 the energy-level shift is rather effectively determined through the matrix elements of the corresponding Dirac-Pauli operator with relativistic Coulomb wave functions. At the same time, for superheavy nuclei with Z ～ 170, this shift, generated by Δg _free, is genuinely nonperturbative, behaves like ～Z ⁵ near the threshold of negative continuum, exceeds all the estimates of radiative corrections coming from vacuum polarization and electron self-energy known so far, and turns out to be at least of the same order as the effects of nuclear charge screening by filled electron shells.     

The mass of the muon

It is shown that a classical relativistic charged particle has an anomalous magnetic moment g=4α/3. If such a “dressed” particle with its mass m, charge e, and anomalous magnetic moment g is quantized by a generalized Dirac equation, then the wave equation predicts a second mass m_μ=m_e(3/2α+1). It is suggested that a magnetic portion of the self-energy is quantized.     

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.     

A Comparative Analysis of In-Medium Spectral Functions for N(940) and N ∗(1535) in Real-Time Thermal Field Theory

In the real-time thermal field theory, the nucleon self-energy at finite temperature and density is evaluated where an extensive set of pion-baryon (π B) loops are consider. On the other side, the in-medium self-energy of N ^?(1535) for π N and η N loops is also determined in the same framework. The detail branch cut structures for these different π B loops for nucleon N(940) and π N, η N loops for N ^?(1535) are addressed. Using the total self-energy of N(940) and N ^?(1535), which contain the contributions of their corresponding loop diagrams, the complete structures of their in-medium spectral functions have been obtained. The Landau and unitary cut contributions provide two separate peak structures in the nucleon spectral function while N ^?(1535) has a single peak structure in its unitary cuts. At high temperature, the peak structures of both at their individual poles are attenuated while at high density Landau peak structure of nucleon is completely suppressed and its unitary peak structure is tending to be shifted towards the melted peak of N ^?(1535). The non-trivial modifications of these chiral partners may indicate some association of chiral symmetry restoration.