Second moment of the Husimi distribution as a measure of complexity of quantum states

We propose the second moment of the Husimi distribution as a measure of complexity of quantum states. The inverse of this quantity represents the effective volume in phase space occupied by the Husimi distribution, and has a good correspondence with chaoticity of classical system. Its properties are similar to the classical entropy proposed by Wehrl, but it is much easier to calculate numerically. We calculate this quantity in the quartic oscillator model, and show that it works well as a measure of chaoticity of quantum states.Comment: 25 pages, 10 figures. to appear in PR

Human rights and ethical reasoning : capabilities, conventions and spheres of public action

This interdisciplinary article argues that human rights must be understood in terms of opportunities for social participation and that social and economic rights are integral to any discussion of the subject. We offer both a social constructionist and a normative framework for a sociology of human rights which reaches beyond liberal individualism, combining insights from the work of Amartya Sen and from French convention theory. Following Sen, we argue that human rights are founded on the promotion of human capabilities as ethical demands shaped by public reasoning. Using French convention theory, we show how the terms of such deliberation are shaped by different constructions of collectively held values and the compromises reached between them. We conclude by demonstrating how our approach offers a new perspective on spheres of public action and the role these should play in promoting social cohesion, individual capabilities and human rights

Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers

An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is performed by computing Bloch and Husimi projections. The eigenstate analysis is combined with the calculation of absorption bands of asymmetric dimer configurations constituted by monomers with nonidentical excitation energies and optical transition matrix elements. Absorption bands with regular and irregular fine structures are obtained and related to the transition from the coexistence to a mixing of adiabatic branches in the spectrum. It is shown that correlations between spin states allow for an interpolation between absorption bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.

Cold atoms in a high-Q ring-cavity

We report the confinement of large clouds of ultra-cold 85-Rb atoms in a standing-wave dipole trap formed by the two counter-propagating modes of a high-Q ring-cavity. Studying the properties of this trap we demonstrate loading of higher-order transverse cavity modes and excite recoil-induced resonances.Comment: 4 pages, 4 figure

Theory of exciton-exciton correlation in nonlinear optical response

We present a systematic theory of Coulomb interaction effects in the nonlinear optical processes in semiconductors using a perturbation series in the exciting laser field. The third-order dynamical response consists of phase-space filling correction, mean-field exciton-exciton interaction, and two-exciton correlation effects expressed as a force-force correlation function. The theory provides a unified description of effects of bound and unbound biexcitons, including memory-effects beyond the Markovian approximation. Approximations for the correlation function are presented.Comment: RevTex, 35 pages, 10 PostScript figs, shorter version submitted to Physical Review

New Limits to the Drift of Fundamental Constants from Laboratory Measurements

We have remeasured the absolute $1S$-$2S$ transition frequency $\nu_{\rm {H}}$ in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of $(-29\pm 57)$ Hz for the drift of $\nu_{\rm {H}}$ with respect to the ground state hyperfine splitting $\nu_{{\rm {Cs}}}$ in $^{133}$Cs. Combining this result with the recently published optical transition frequency in $^{199}$Hg$^+$ against $\nu_{\rm {Cs}}$ and a microwave $^{87}$Rb and $^{133}$Cs clock comparison, we deduce separate limits on $\dot{\alpha}/\alpha = (-0.9\pm 2.9)\times 10^{-15}$ yr$^{-1}$ and the fractional time variation of the ratio of Rb and Cs nuclear magnetic moments $\mu_{\rm {Rb}}/\mu_{\rm {Cs}}$ equal to $(-0.5 \pm 1.7)\times 10^{-15}$ yr$^{-1}$. The latter provides information on the temporal behavior of the constant of strong interaction.Comment: 4 pages, 3 figures, LaTe

Statistics of electromagnetic transitions as a signature of chaos in many-electron atoms

Using a configuration interaction approach we study statistics of the dipole matrix elements (E1 amplitudes) between the 14 lower odd states with J=4 and 21st to 100th even states with J=4 in the Ce atom (1120 lines). We show that the distribution of the matrix elements is close to Gaussian, although the width of the Gaussian distribution, i.e. the root-mean-square matrix element, changes with the excitation energy. The corresponding line strengths are distributed according to the Porter-Thomas law which describes statistics of transition strengths between chaotic states in compound nuclei. We also show how to use a statistical theory to calculate mean squared values of the matrix elements or transition amplitudes between chaotic many-body states. We draw some support for our conclusions from the analysis of the 228 experimental line strengths in Ce [J. Opt. Soc. Am. v. 8, p. 1545 (1991)], although direct comparison with the calculations is impeded by incompleteness of the experimental data. Nevertheless, the statistics observed evidence that highly excited many-electron states in atoms are indeed chaotic.Comment: 16 pages, REVTEX, 4 PostScript figures (submitted to Phys Rev A

Isotope Shift Measurements of Stable and Short-Lived Lithium Isotopes for Nuclear Charge Radii Determination

Changes in the mean-square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a new laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8 ms lifetime isotope with production rates on the order of only 10,000 atoms/s. The method was applied to all bound isotopes of lithium including the two-neutron halo isotope Li-11 at the on-line isotope separators at GSI, Darmstadt, Germany and at TRIUMF, Vancouver, Canada. We describe the laser spectroscopic method in detail, present updated and improved values from theory and experiment, and discuss the results.Comment: 34 pages, 24 figures, 14 table

Soft X-ray resonant scattering study of single-crystal LaSr2_2Mn2_2O7_7

Soft X-ray resonant scattering studies at the Mn $L_{\texttt{II, III}}$- and the La $M_{\texttt{IV, V}}$- edges of single-crystal LaSr$_2$Mn$_2$O$_7$ are reported. At low temperatures, below $T_\texttt{N} \approx 160$ K, energy scans with a fixed momentum transfer at the \emph{A}-type antiferromagnetic (0 0 1) reflection around the Mn $L_{\texttt{II, III}}$-edges with incident linear $\sigma$ and $\pi$ polarizations show strong resonant enhancements. The splitting of the energy spectra around the Mn $L_{\texttt{II, III}}$-edges may indicate the presence of a mixed valence state, e.g., Mn$^{3+}$/Mn$^{4+}$. The relative intensities of the resonance and the clear shoulder-feature as well as the strong incident $\sigma$ and $\pi$ polarization dependences strongly indicate its complex electronic origin. Unexpected enhancement of the charge Bragg (0 0 2) reflection at the La $M_{\texttt{IV, V}}$-edges with $\sigma$ polarization has been observed up to 300 K, with an anomaly appearing around the orbital-ordering transition temperature, $T_{\texttt{OO}} \approx 220$ K, suggesting a strong coupling (competition) between them.Comment: Accepted by European Physical Journal