Relativistic Many-body Theory Research Articles

Relativistic Coupled Cluster (RCC) Computation of the Electric Dipole Moment Enhancement Factor of Francium Due to the Violation of Time Reversal Symmetry

A relativistic many-body theory for the electric dipole moment (EDM) of paramagnetic atoms arising from the electric dipole moment of the electron is presented and implemented. The relativistic coupled-cluster method with single and double excitations (RCCSD) using the Dirac-Coulomb Hamiltonian and a weak parity and time reversal violating interaction to the first-order of perturbation has been employed to obtain the EDM enhancement factor for the ground state of the Fr atom due to the intrinsic EDM of the electron. The trends of different correlation effects and the leading contributions from different physical states are discussed. Our results in combination with that of the Fr EDM experiment that is currently in progress possess the potential to probe the validity of the standard model (SM) of elementary particle physics.

Development of a configuration-interaction plus all-order method for atomic calculations

We develop a theoretical method within the framework of relativistic many-body theory to accurately treat correlation corrections in atoms with few valence electrons. This method combines the all-order approach currently used in precision calculations of properties of monovalent atoms with the configuration-interaction approach that is applicable for many-electron systems. The method is applied to Mg, Ca, Sr, Zn, Cd, Ba, and Hg to evaluate ionization energies and low-lying energy levels.

High-precision x-ray spectroscopy in few-electron ions

The experimental and spectrum analysis procedures that led to about 15 new, high-precision, relative x-ray line energy measurements are presented. The measured lines may be used as x-ray reference lines in the 2.4–3.1 keV range. Applications also include tests of the atomic theory, and in particular of quantum electrodynamics and of relativistic many-body theory calculations. The lines originate from 2- to 4-electron ions of sulfur (Z=16), chlorine (Z=17) and argon (Z=18). The precision reached for their energy ranges from a few parts per million (ppm) to about 50 ppm. This places the new measurements among the most precise performed in mid-Z highly charged ions (Z is the nuclear charge number). The elements of the experimental setup are described: the ion source (an electron cyclotron resonance ion trap), the spectrometer (a single, spherically bent crystal spectrometer), as well as the spectrum acquisition camera (low-noise, high-efficiency CCD). The spectrum analysis procedure, which is based on a full simulation of the spectrometer response function, is also presented.

Improved Measurement of the1s2s S01−1s2p P13Interval in Heliumlike Silicon

Using colinear fast-beam laser spectroscopy with copropagating and counter-propagating beams we have measured the 1s2s 1S0-1s2p 3P1 intercombination interval in 28Si12+ with the result 7230.585(6) cm{-1}. The experiment made use of a dual-wavelength, high-finesse, power build-up cavity excited by single-frequency lasers at 1319 and 1450 nm. The result will provide a precision test of ab initio relativistic many-body atomic theory at moderate Z.

Influence of the isospin and hypercharge chemical potentials on the location of the critical end point in theμB−Tphase diagram of theSU(3)L×SU(3)Rchiral quark model

We investigate the influence of the asymmetric quark matter (${\ensuremath{\rho}}_{u}\ensuremath{\ne}{\ensuremath{\rho}}_{d}\ensuremath{\ne}{\ensuremath{\rho}}_{s}$) on the mass of the quasiparticles and the phase diagram of the chiral quark model parametrized at the one-loop level of the renormalized theory, using the optimized perturbation theory for the resummation of the perturbative series. The effect of various chemical potentials introduced in the grand canonical ensemble is investigated with the method of relativistic many-body theory. The temperature dependence of the topological susceptibility is estimated with the help of the Witten-Veneziano mass formula.

Relativistic many-body calculation of energies, lifetimes, hyperfine constants, and polarizabilities inL7i

The excitation energies of $ns$, $np$, $nd$, and $nf$ $(n\ensuremath{\le}6)$ states in neutral lithium are evaluated within the framework of relativistic many-body theory. First-, second-, third-, and all-order Coulomb energies and first- and second-order Breit corrections to energies are calculated. All-order calculations of reduced matrix elements, oscillator strengths, transition rates, and lifetimes are given for levels up to $n=4$. Electric-dipole $(2s\ensuremath{-}np)$, electric-quadrupole $(2s\ensuremath{-}nd)$, and electric-octupole $(2s\ensuremath{-}nf)$, matrix elements are evaluated to obtain the corresponding ground-state multipole polarizabilities using the sum-over-states approach. Scalar and tensor polarizabilities for the $2{p}_{1/2}$ and $2{p}_{3/2}$ states are also calculated. Magnetic-dipole hyperfine constants $A$ are determined for low-lying levels up to $n=4$. The quadratic Stark shift for the $(F=2\text{ }M=0)\ensuremath{\leftrightarrow}(F=1\text{ }M=0)$ ground-state hyperfine transition is found to be $\ensuremath{-}0.0582\text{ }\text{Hz}/{(\text{kV}/\text{cm})}^{2}$, in slight disagreement with the experimental value $\ensuremath{-}0.061\ifmmode\pm\else\textpm\fi{}0.002\text{ }\text{Hz}/{(\text{kV}/\text{cm})}^{2}$. Matrix elements used in evaluating polarizabilities, hyperfine constants, and the quadratic Stark shift are obtained using the all-order method.

A new formulation of the relativistic many-body theory of electric dipole moments of closed shell atoms

The electric dipole moments of closed-shell atoms are sensitive to the parity and time-reversal violating phenomena in the nucleus. The nuclear Schiff moment is one such property, it arises from the parity and time reversal violating quark-quark interactions and the quark-chromo electric dipole moments. We calculate the electric dipole moment of atomic 199Hg arising from the nuclear Schiff moment using the relativistic coupled-cluster theory. This is the most accurate calculation of the quantity to date. Our calculations in combination with the experiment data provide important insights to the P and T violating coupling constants at the elementary particle level. In addition, a new limit on the tensor-pseudo tensor induced atomic EDM, calculated using the relativistic coupled-cluster theory is also presented.

Theoretical studies of the atomic transitions in boron-like ions: Mg VIII, Si X and S XII

In this paper, we have carried out the calculations of the weighted oscillator strengths and the transition probabilities for a few low-lying transitions of boron-like ions: Mg VIII, Si X and S XII, which are astrophysically important, particularly in the atmosphere of the solar corona. We have employed an all-order relativistic many-body theory called the relativistic coupled-cluster theory to calculate very precisely these atomic quantities of astrophysical interest. We have reported for the first time the transition probabilities for some forbidden transitions which are unavailable in the literature, either theoretically or experimentally. We also discuss the physical effects associated with these transitions. Our data can be used for the identification of spectral lines arising from the coronal atmospheres of the Sun and Sun-like stars having an extended corona.

Ab initio determination of the lifetime of the 62P3/2 state for 207Pb+ by relativistic many-body theory

Relativistic coupled-cluster theory has been employed to calculate the lifetime of the 62P3/2 state of singly ionized lead (207Pb) and compared with the corresponding values obtained from second-order relativistic many-body perturbation theory and an accurate ion trapping experiment. This is one of the very few applications of this theory to excited state properties of heavy atomic systems. Contributions from the different electron correlation effects are given explicitly.

Relativistic many-body theory with radioactive ion beams: Surface pion condensation

We critically review the present relativistic mean-field theory from the viewpoint of missing pions. We introduce the interesting experimental data on pionic states taken at RCNP. These data seem to suggest the occurrence of pion condensation in the nuclear surface. Qualitative discussion is made on the consequence of surface pion condensation on Gamow-Teller transitions and spin response functions and others. The radioactive ion beams are the tools of studying the unstable nuclei, which have extended nuclear surfaces. We shall start with radioactive ion beams the nuclear surface science, which includes the surface pion condensation as the important ingredient in addition to spin-orbit splitting and surface pairing.

Longitudinal and transverse spin responses in relativistic many-body theory

We study theoretically the spin response functions using the relativistic many-body theory. The spin response functions in the relativistic theory are reduced largely from the ones of the non-relativistic theory, in particular the longitudinal spin responses. This fact enables us to remove the difficulty in reproducing the ratio of the longitudinal and transverse response functions seen experimentally. We use the local density approximation with the eikonal prescription of the nuclear absorption on the incoming and outgoing nucleons for the calculations of the response functions of finite nuclei. We compare the calculated results with the recent experimental results with ( p, n ) reactions on C and Ca.

Measurement of the two-photon spectral distribution from decay of the1s2s1S0level in heliumlike nickel

A measurement of the shape of the spectral distribution of two-photon decay of the $1s2s{}^{1}{S}_{0}$ level in heliumlike nickel is described. Uncertainties in detector efficiencies which had limited the precision of earlier measurements were eliminated by comparing the continuum emission from two-photon decays of H-like and He-like nickel. Our results are in agreement with the nonrelativistic calculation of Drake and the fully relativistic calculation of Derevianko and Johnson and suggest a method for testing relativistic atomic many-body theory in strong fields.

Relativistic many-body theory for unstable nuclei and astrophysics

We discuss the properties of unstable nuclei and the equations of state of nuclear matter in the framework of the relativistic many-body theory. We take the relativistic mean-field (RMF) theory as a phenomenological theory with several parameters, whose form is constrained by the successful microscopic theory (RBHF), and whose values are extracted by using the experimental values of unstable nuclei. We find the outcome with the newly obtained parameter sets (TM1 and TMA) is promising in comparison with various experimental data. We calculate systematically the ground-state properties of even-even nuclei up to the drip lines; about 2000 nuclei. We find that the neutron magic shells at the standard magic numbers stay at the same numbers even far from the stability line and hence provide the r-process nuclei. However, many proton magic numbers disappear at the neutron numbers far away from the magic numbers owing to the deformations. We also study the neutron star profiles with the equation of state of nuclear matter with the use of RMF with TM1. We find that the proton fraction at the neutron star centre is as large as 20%, which is much larger than the conventional number of less than 1%.

High-density limit in relativistic many-body theory of nuclear matter

High-density limit in relativistic many-body theory of nuclear matter

Hard Photon Productions in Proton-Induced Reactions11The project supported by the Grant LWTZ-1298 of Chinese Academy of Sciences

We briefly describe Brown's T-matrix formulation and deep attractive forbidden state potentials most recently proposed by Neudatchin et al. Differential cross sections of are calculated, and the results are in agreement with experimental data. By including the Pauli principle, Fermi momentum of target nucleus and nucleon effective mass determined by relativistic nuclear many-body theory, which reflects nucleon multiple-scattering effects in nuclear medium, the hard photon productions in proton-deuteron, proton-carbon and proton-lead collisions are investigated.

Relation of QCD sum rules in matter and the nuclear many-body problem.

The method of QCD sum rules provides a powerful technique for the calculation of properties of hadrons in terms of a number of parameters that specify various condensate matrix elements. One may hope that it will be possible to calculate some of the condensate matrix elements using effective Lagrangians. If we concentrate on quark condensates, the Nambu--Jona-Lasinio model may provide a useful model. In this work we study the relation between relativistic nuclear many-body theory and the analysis of the nucleon self-energy in nuclear matter made using QCD sum rules. This is done by introducing the fields of a bosonized version of the Nambu--Jona-Lasinio (NJL) model. Using the simplest version of the QCD sum-rule analysis, we replace the QCD order parameters in matter with related order parameters describing a Lorentz scalar and a vector field. In our mean-field analysis we find that the many-body theory, based upon the bosonization of the NJL model, is consistent with the simplest version of the QCD sum-rule calculation of the nucleon self-energy in matter.

Precision lifetimes for the Ca+ 4p 2P levels: Experiment challenges theory at the 1% level.

The mean lifetimes \ensuremath{\tau} of the ${\mathrm{Ca}}^{+}$ 4p $^{2}$${\mathit{P}}_{3/2}$ and $^{2}$${\mathit{P}}_{1/2}$ levels have been measured to \ensuremath{\approxeq}0.3% precision using a variant of the collinear laser-beam\char21{}ion-beam spectroscopy technique. Like previously measured precision lifetimes of light alkali-metal-like systems, these data fall significantly higher than calculations by the most recent multiconfiguration Hartree-Fock and relativistic many-body perturbation theories. Discrepancies between experiment and theory for alkali-metal-like systems have implications for the interpretation of parity-violation research.

EOS and Fermi-liquid properties in the [formula omitted] expansion of a relativistic many-body theory

The equation of state (EOS) for cold nuclear and neutron matter is investigated in the framework of relativistic meson-nucleon theory employing the 1 N expansion scheme. It is found that the inclusion of the relativistic Fock and correlation energies leads to a softening of the EOS, bringing the results closer to the empirical body of information on the state of matter at high densities. The resulting properties of quasiparticles are investigated using methods of the Landau-Migdal theory. As applications, neutron-star structure and collective excitations in infinite nuclear matter are discussed.

Fermi-liquid properties of nuclear matter in a relativistic many-body theory

Fermi-liquid properties of nuclear matter in a relativistic many-body theory

Electromagnetic properties of quasiparticles in a relativistic many-body theory

Using a relativistic meson-nucleon theory we describe both the ground state of nuclear matter and the electromagnetic current of a quasiparticle including vacuum fluctuation effects in the same framework. The energy density of nuclea matter is calculated in the two-loop approximation including also those higher-order effects which are known to be essential for stability, and the quasiparticle current is calculated in the one-loop approximation. Due to the consistency between the description of the strong and electromagnetic interactions, all requirements of gauge invariance can be satisfied. Relativistic corrections to the magnetic g-factors are studied in detail.