## Victor Flambaum Group

## About:

## Introduction

The staff of the Department of Theoretical Physics carry out research in a wide variety of areas as outlined below. A significant part of our research is carried out as collaborative projects with colleagues at other Australian institutions and overseas.

## Areas of Research

##### Parity Non-conservation and Time-invariance Violation in Atoms and Nuclei

This is one of the most interesting and challenging topic of the modern atomic and nuclear physics. It is focused on the investigation of the fundamental nature forces with the aim to contribute towards their grand unification. The information obtained by the measurements of parity non-conservation (PNC) and time invariance violation (TIV) in atoms is of the similar value as those which comes from huge and expensive accelerators. On the other side, the PNC and TIV effects in atoms are usually very small and require sophisticated experimental technique for the measurements and high-precision atomic calculations for the accurate interpretation of the experimental results.

Using the technique which is described below we have performed the most accurate calculations of the PNC effect in Cs, Fr, Tl, Pb and Bi. We are working on further improvement of the accuracy of calculations and on calculation of the PNC or TIV effects for those atoms where such measurements have been proposed (Dy, Hg, Ra, Ba+, etc.)(see, e.g. [1-3]).

[1] V. A. Dzuba, V. V. Flambaum, J. S. M. Ginges, Phys. Rev. D, 66, 076013 (2002).

[2] V. V. Flambaum, J. S. M. Ginges,Phys. Rev. A, 65, 032113 (2002).

[3] V. A. Dzuba, V. V. Flambaum, J. S. M. Ginges, M. G. Kozlov, Phys. Rev. A, 66, 012111 (2002).

##### Variation of Fundamental Constants

The possibility that fundamental constants (such as the speed of light, the electron charge and mass, the Planck constant, etc.) can change in time is predicted by some unified field theories. The detection of such a variation would be an important confirmation of these theories. The analysis of the spectra of distant quasars performed at UNSW does indicate that the fine structure constant alpha might be changing in time [1]. This analysis is done by a method suggested by our group [2]. It relies on the comparison of frequencies of electric dipole transitions of atoms in distant parts of the Universe (billions of light years away) with those on Earth. These frequencies are much more sensitive to the value of the fine structure constant than the fine structure intervals used in previous studies. Accurate relativistic calculations are used to link atomic frequencies with the fine structure constant (see, e.g. [3]).

[1] J. K. Webb, V. V. Flambaum, C. W. Churchill, M. J. Drinkwater, and J. D. Barrow, Phys. Rev. Lett. 82, 884 (1999); J. K. Webb, M. T. Murphy, V. V. Flambaum, V. A. Dzuba, J. D. Barrow, C. W. Churchill, J. X. Prochaska, and A. M. Wolfe, Phys. Rev. Lett. 87, 091301 (2001).

[2] V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. Lett. 82, 888 (1999).

[3] V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. A 59, 230 (1999).

##### Isotope Shift

The isotope shift (IS) is a difference in energies of different isotopes of the same atom due to differences in nuclear mass and volume. Studies of isotope shifts are interesting for at least two reasons. First, the IS is an important systematic effect which could mimic the effect of a varying fine structure constant in absorption spectra of distant quasars. Second, a comparison of calculated and measured ISs is a way to study nuclear structure.

We are developing an all-order (in the Coulomb interaction) technique which would allow us to calculate ISs to very high precision.

##### Many-body theory and methods for high-precision atomic calculations

Many-body theory and methods for high-precision atomic calculations Relativistic Hartree-Fock (sometimes called Dirac-Hartree-Fock) method and Random-Phase Approximation (or Time-Dependent Hartree-Fock method in external field) are used as a starting point for high-precision calculations for many-electron atoms. To include electron correlations the following methods have been developed in our group:

- Perturbation Theory in Screened Coulomb Interaction and Correlation Potential methods - for atoms with one valence electron (positron) above closed shells [1].
- Combined Configuration Interaction and Many-Body Perturbation Theory method - for atoms with any number of valence electrons [2].

This enables us to perform calculations for many-electron neutral or nearly neutral atoms with the best accuracy available at present time. The Breit interaction (the magnetic interaction between atomic electrons) and radiative corrections can also be taken into account when nessasary [3].

[1] V. A. Dzuba, V. V. Flambaum, O. P. Sushkov, Phys. Lett. A, 140, 493 (1989); Phys. Lett. A, 141, 147 (1989); V. A. Dzuba, V. V. Flambaum, A. Ya. Kraftmakher, O. P. Sushkov, Phys. Lett. A, 142, 373 (1989).

[2] V.A.Dzuba, V.V.Flambaum, M.G.Kozlov, Phys. Rev. A, 54, 3948 (1996).

[3] V. A. Dzuba, C. Harabati, W. R. Johnson, M. S. Safronova, Phys. Rev. A., 63, 044103 (2001).