Crystal field contribution to Mössbauer isomer shift

The crystal field hamiltonian H_c = B₂⁰Y₂⁰ + B₂²(Y₂² + Y₂^?2) commonly used in the study of electron-spin resonance is employed to obtain new contributions to the ⁵⁷Fe³⁺ isomer shift in the Mössbauer effect. A numerical estimate of the shift is also presented.     

Stark shift contribution to field statistics in a generalized Jaynes-Cummings model

The nonlinear and multiphoton interaction between a single two-level atom and two modes of radiation is studied in a generalized Jaynes-Cummings model. An intensity-dependent level shift is considered. The time evolution operator is obtained. The detuning has a photon number dependence. Different statistical aspects pertaining to either the atom or the fields are calculated. The dipole moment, the dipole-dipole correlation function, as well as the transient spectrum are obtained.     

Hadronic light-by-light scattering contribution to the muon g - 2: an effective field theory approach

The hadronic light-by-light contribution to a(mu), the anomalous magnetic moment of the muon, is discussed from the point of view of an effective low-energy theory. As an application, the coefficient of the leading logarithm arising from the two-loop graphs involving two anomalous vertices is computed, and found to be positive. This corresponds to a positive sign for the pion-pole contribution to the hadronic light-by-light correction to a(mu), and to a sizable reduction of the discrepancy between the present experimental value of a(mu) and its theoretical counterpart in the standard model.     

Radiation shift of the electron mass in a magnetic field (Higgs boson contribution)

The single-loop contribution of Higgs bosons to the radiation shift of the energy of an electron moving in a homogeneous permanent magnetic field is calculated. On the basis of this contribution, the appropriate contribution to the anomalous magnetic moment of the electron and the probability of magnetic-braking radiation of Higgs bosons by an electron are found. The dependence of the mentioned quantities on the electron energy and the external field intensity is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 75–79, May, 1988.The authors are grateful to V. Ch. Zhukovskii, A. I. Studenikin, and I. A. Obukhov for useful discussion of the research results.     

Phonon contribution to the shear viscosity of a superfluid Fermi gas in the unitarity limit

We present a detailed analysis of the contribution of small-angle Nambu–Goldstone boson (phonon) collisions to the shear viscosity, η$\eta$, in a superfluid atomic Fermi gas close to the unitarity limit. We show that the experimental values of the shear viscosity coefficient to entropy ratio, η/s$\eta /s$, obtained at the lowest reached temperature can be reproduced assuming that phonons give the leading contribution to η$\eta$. The phonon contribution is evaluated considering 1↔2$1\leftrightarrow 2$ processes and taking into account the finite size of the experimental system. In particular, for very low temperatures, T?0.1T_F$T?0.1T_F$, we find that phonons are ballistic and the contribution of phonons to the shear viscosity is determined by the processes that take place at the interface between the superfluid and the normal phase. This result is independent of the detailed form of the phonon dispersion law and leads to two testable predictions: the shear viscosity should correlate with the size of the optical trap and it should decrease with decreasing temperature. For higher temperatures the detailed form of the phonon dispersion law becomes relevant and, within our model, we find that the experimental data for η/s$\eta /s$ can be reproduced assuming that phonons have an anomalous dispersion law.     

Hadronic vacuum polarization contribution to the Lamb shift in muonic hydrogen

We report on the accuracy of the measurement of the total cross section of the process e⁺e^– ZH and of the Higgs boson mass that would be achieved in a linear collider operating at a centre-of-mass energy of 350 GeV, assuming an integrated luminosity of 500 fb^–1. For that we have exploited the recoil mass off the Z using its leptonic decays into electron and muon pairs. The Higgs mass is determined with 150 MeV accuracy, the recoil mass resolution is about 1.5 GeV and the cross section is obtained with a statistical error of 3%.     

Upper bound on the hadronic light-by-light contribution to the muon g - 2

There are indications that hadronic loops in some electroweak observables are almost saturated by parton level effects. Taking this as the hypothesis for this work, we propose a genuine parton level estimate of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, a(LBL)/(mu)(had). Our quark mass definitions and values are motivated in detail, and the simplicity of our approach allows for a transparent error estimate. For infinitely heavy quarks our treatment is exact, while for asymptotically small quark masses a(LBL)/(mu)(had) is overestimated. Interpolating, this suggests quoting an upper bound. We obtain a(LBL)/(mu)(had)<1.59x10;{-9} (95% C.L.).     

Hadronic light-by-light contribution to muon g - 2 in chiral perturbation theory

We compute the hadronic light-by-light scattering contributions to the muon anomalous magnetic moment, a(LL)(mu)(had), in chiral perturbation theory that are enhanced by large logarithms and a factor of N(C). They depend on a low-energy constant constrained by eta-->mu(+) mu(-) and pi(0)-->e(+)e(-) branching ratios. However, the dependence of a(LL)(mu)(had) on nonlogarithmically enhanced effects cannot be constrained except through the measurement of the anomalous moment itself.     

Thermal Raman shift of the C60 tangentialA g mode

Fullerence C₆₀ exhibits a continuous and reversibleA _g (2) mode softening from 1469 to 1459 cm^–1, which is linear with laser power up to 21.9 kW/cm² for C₆₀ crystals under vacuum. Model calculations taking into account the temperature distribution that is induced by the Gaussian intensity profile of the laser beam reproduce the measured frequency shifts. A thermal conductivity of microcrystalline fullerene of 0.27(±0.03) W/mK is derived from this numerical analysis.     

Leading logarithmic contribution to the second-order lamb shift induced by the loop-after-loop diagram

The contribution of order alpha(2)(Zalpha)(6)ln (3)(Zalpha)(-2) to the ground-state Lamb shift in hydrogen induced by the loop-after-loop diagram is evaluated analytically. An additional contribution of this order is found compared to the previous calculation by Karshenboim [Sov. Phys. JETP 76, 541 (1993)]. As a result, agreement is achieved for this correction between different numerical and analytical methods.     

Phonon frequency shift and effect of correlation on the electron-phonon interaction in heavy fermion systems

The electron-phonon interaction in the periodic Anderson model (PAM) is considered. The PAM incorporates the effect of onsite Coulomb interaction (U) between f-electrons. The influence of Coulomb correlation U on the phonon response of the system is studied by evaluating the phonon spectral function for various parameters of the model. The numerical evaluation of the spectral function is carried out in the long wavelength limit at finite temperatures keeping only linear terms in U. The observed behaviour is found to agree well with the general features obtained experimentally for some heavy fermion (HF) systems.     

A contribution to the Rainich theory of the neutrino field

The neutrino-gravitational field is divided into fourteen distinct classes. This classification is shown also to determine the class of the space-time. Then for four particular classes of space-time, necessary and sufficient conditions on the concomitants of the Ricci tensor are given for it to admit a neutrino field. It is further shown that for three of these classes the neutrino field is determined uniquely by the metric of space-time.     

Electronic contribution to electric field gradient in β-gallium

Electronic contribution to electric field gradient (EFG) inβ-Ga has been calculated for the first time using the band wave functions. The results show that the magnitudes of the quadrupole resonance frequency and the net EFG agree with experiment to within 7% and 2% respectively.     

Electronic contribution to electric field gradient in dilute alloys

A simple relation for calculating the electronic contribution to the electric field gradient in dilute alloys of transition metals is reported and is compared with the conduction electron charge shift model. The dependence of the field gradient on thes andd electrons and the difference in radii between the host and the probe atoms is considered for calculating the field gradient. It is found that thed electrons are the major contributors to the field gradient.     

Evaluation of the specific mass shift and field shift in the alkaline-earth Sr atom

Vinti's expression for the Specific mass shift, determined as a sum over Slater integrals, has been used in a first-order perturbation treatment of alkaline-earth atoms. The Specific mass shift and Field shift have been evaluated for a number of transitions in the Sr atom. Mixing of the main configuration with one or two excited configurations has been taken into account in the levels involved in some of the transitions. The orbitals were generated in a potential, with adjustable radial scaling parameters, represented by an analytic expression with an infinite radius of convergence. The present results are compared, where possible, with results of other theoretical calculations and with experimental data.     

Absorption edge shift: Internal electric field model

The shift of the optical absorption edge caused by defect-induced electric fields through Redfield's internal Franz-Keldysh mechanism is discussed for semiconductors and insulators.