Study of the correlation effects in Yb^+ and implications for parity violation

Calculation of the energies, magnetic dipole hyperfine structure constants, E1 transition amplitudes between the low-lying states, and nuclear spin-dependent parity-nonconserving amplitudes for the ^2S_{1/2} - ^2D_{3/2,5/2} transitions in ^{171}Yb^+ ion is performed using two different approaches. First, we carried out many-body perturbation theory calculation considering Yb^+ as a monovalent system. Additional all-order calculations are carried out for selected properties. Second, we carried out configuration interaction calculation considering Yb as a 15-electron system and compared the results obtained by two methods. The accuracy of different methods is evaluated. We find that the monovalent description is inadequate for evaluation of some atomic properties due to significant mixing of the one-particle and the hole-two-particle configurations. Performing the calculation by such different approaches allowed us to establish the importance of various correlation effects for Yb^+ atomic properties for future improvement of theoretical precision in this complicated system.Comment: 11 pages;v2: minor changes and one reference adde

Metal-insulator transition and glassy behavior in two-dimensional electron systems

Studies of low-frequency resistance noise demonstrate that glassy freezing occurs in a two-dimensional electron system in silicon in the vicinity of the metal-insulator transition (MIT). The width of the metallic glass phase, which separates the 2D metal and the (glassy) insulator, depends strongly on disorder, becoming extremely small in high-mobility (low-disorder) samples. The glass transition is manifested by a sudden and dramatic slowing down of the electron dynamics, and by a very abrupt change to the sort of statistics characteristic of complicated multistate systems. In particular, the behavior of the second spectrum, an important fourth-order noise statistic, indicates the presence of long-range correlations between fluctuators in the glassy phase, consistent with the hierarchical picture of glassy dynamics.Comment: Contribution to conference on "Noise as a tool for studying materials" (SPIE), Santa Fe, New Mexico, June 2003; 15 pages, 12 figs. (includes some low-quality figs; send e-mail to get high-quality figs.

Transition frequency shifts with fine-structure constant variation for Yb II

In this paper we report calculations of the relativistic corrections to transition frequencies (q factors) of Yb II for the transitions from the odd-parity states to the metastable state 4f^{13}6s^2 ^2F_{7/2}^o. These transitions are of particular interest experimentally since they possess some of the largest q factors calculated to date and the $^2F_{7/2}^o$ state can be prepared with high efficiency. This makes Yb II a very attractive candidate for the laboratory search for variation of the fine-structure constant alpha.Comment: 5 page

Magnetotransport in the low carrier density ferromagnet EuB_6

We present a magnetotransport study of the low--carrier density ferromagnet EuB_6. This semimetallic compound, which undergoes two ferromagnetic transitions at T_l = 15.3 K and T_c = 12.5 K, exhibits close to T_l a colossal magnetoresistivity (CMR). We quantitatively compare our data to recent theoretical work, which however fails to explain our observations. We attribute this disagreement with theory to the unique type of magnetic polaron formation in EuB_6.Comment: Conference contribution MMM'99, San Jos

Mobility-Dependence of the Critical Density in Two-Dimensional Systems: An Empirical Relation

For five different electron and hole systems in two dimensions (Si MOSFET's, p-GaAs, p-SiGe, n-GaAs and n-AlAs), the critical density, $n_c$ that marks the onset of strong localization is shown to be a single power-law function of the scattering rate $1/\tau$ deduced from the maximum mobility. The resulting curve defines the boundary separating a localized phase from a phase that exhibits metallic behavior. The critical density $n_c \to 0$ in the limit of infinite mobility.Comment: 2 pages, 1 figur

Electric dipole moment enhancement factor of thallium

The goal of this work is to resolve the present controversy in the value of the EDM enhancement factor of Tl. We have carried out several calculations by different high-precision methods, studied previously omitted corrections, as well as tested our methodology on other parity conserving quantities. We find the EDM enhancement factor of Tl to be equal to -573(20). This value is 20% larger than the recently published result of Nataraj et al. [Phys. Rev. Lett. 106, 200403 (2011)], but agrees very well with several earlier results.Comment: 5 pages; v2: link to supplemental material adde

On the issue of assessing the safety of adjunction on roads

The principal aim of this article is to meticulously investigate and enhance the standards of highway safety and the accompanying infrastructural elements. The article scrutinizes data pertaining to vehicular mishaps over the preceding years, pinpointing crucial elements that precipitate the incidents. Among these contributing factors are the condition of the paved roadway, the clarity of view, the magnitude of vehicular flow, illumination, amongst others. The authors devote considerable attention to the utilization of engineering management strategies, alongside risk management systems, to bolster the safety measures on highways. The discourse proposes the implementation of fuzzy logic allied with the FisPro system, as means to dissect and prognosticate traffic scenarios. The employment of these methodologies enables the consideration of the intricate and multidimensional nature of the issue of highway safety, taking into account the myriad of intertwined parameters. The article underscores the necessity for a holistic approach to effectively amplify the safety standards of highways, encompassing all factors that exert influence on the prevailing traffic conditions. Such a comprehensive methodology permits not merely the response to budding issues, but also the anticipation of potential risks, consequently enabling the timely implementation of preventative measures to avert them

The atomic electric dipole moment induced by the nuclear electric dipole moment; the magnetic moment effect

We have considered a mechanism for inducing a time-reversal violating electric dipole moment (EDM) in atoms through the interaction of a nuclear EDM (d_N) with the hyperfine interaction, the "magnetic moment effect". We have derived the operator for this interaction and presented analytical formulas for the matrix elements between atomic states. Induced EDMs in the diamagnetic atoms 129Xe, 171Yb, 199Hg, 211Rn, and 225Ra have been calculated numerically. From the experimental limits on the atomic EDMs of 129Xe and 199Hg, we have placed the following constraints on the nuclear EDMs, |d_N(129Xe)|< 1.1 * 10^{-21} |e|cm and |d_N(199Hg)|< 2.8 * 10^{-24} |e|cm.Comment: 8 pages 1) Some typos are corrected. 2) A comparison of contributions to the atomic EDM due to the nuclear EDM and the nuclear Schiff moment is adde

Transition frequency shifts with fine structure constant variation for Fe II: Breit and core-valence correlation correction

Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant \alpha. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible variation of \alpha in cause of cosmic time. In this paper we calculated the dependence of the transition frequencies on \alpha^2 (q-factors) for Fe II ion. We found corrections to these coefficients from valence-valence and core-valence correlations and from the Breit interaction. Both the core-valence correlation and Breit corrections to the q-factors appeared to be larger than had been anticipated previously. Nevertheless our calculation confirms that the Fe II absorption lines seen in quasar spectra have large q-factors of both signs and thus the ion Fe II alone can be used in the search for the \alpha-variation at different cosmological epochs.Comment: 7 pages, submitted to Phys. Rev.

Calculation of P,T-odd electric dipole moments for diamagnetic atoms 129^{129}Xe, 171^{171}Yb, 199^{199}Hg, 211^{211}Rn, and 225^{225}Ra

Electric dipole moments of diamagnetic atoms of experimental interest are calculated using the relativistic Hartree-Fock and random-phase approximation methods, the many-body perturbation theory and configuration interaction technique. We consider P,T-odd interactions which give rise to atomic electric dipole moment in the second order of the perturbation theory. These include nuclear Schiff moment, P,T-odd electron-nucleon interaction and electron electric dipole moment. Interpretation of a new experimental constraint of a permanent electric dipole moment of $^{199}$Hg [W. C. Griffith {\it et al.}, Phys. Rev. Lett. {\bf 102}, 101601 (2009)] is discussed.Comment: 9 page