Breakdown of the classical double copy for the effective action of dilaton-gravity at NNLO

We demonstrate that a recently proposed classical double copy procedure to construct the effective action of two massive particles in dilaton-gravity from the analogous problem of two color charged particles in Yang-Mills gauge theory fails at next-to-next-to-leading orders in the post-Minkowskian (3PM) or post-Newtonian (2PN) expansions

Topological Phenomena in Classical Optical Networks

We propose a scheme to realize a topological insulator with optical-passive elements, and analyze the effects of Kerr-nonlinearities in its topological behavior. In the linear regime, our design gives rise to an optical spectrum with topological features and where the bandwidths and bandgaps are dramatically broadened. The resulting edge modes cover a very wide frequency range. We relate this behavior to the fact that the effective Hamiltonian describing the system's amplitudes is long-range. We also develop a method to analyze the scheme in the presence of a Kerr medium. We assess robustness and stability of the topological features, and predict the presence of chiral squeezed fluctuations at the edges in some parameter regimes.Comment: 18 pages, 9 figure

Rotational properties of nuclei around 254^{254}No investigated using a spectroscopic-quality Skyrme energy density functional

Nuclei in the $Z\approx100$ mass region represent the heaviest systems where detailed spectroscopic information is experimentally available. Although microscopic-macroscopic and self-consistent models have achieved great success in describing the data in this mass region, a fully satisfying precise theoretical description is still missing. By using fine-tuned parametrizations of the energy density functionals, the present work aims at an improved description of the single-particle properties and rotational bands in the nobelium region. Such locally optimized parameterizations may have better properties when extrapolating towards the superheavy region. Skyrme-Hartree-Fock-Bogolyubov and Lipkin-Nogami methods were used to calculate the quasiparticle energies and rotational bands of nuclei in the nobelium region. Starting from the most recent Skyrme parametrization, UNEDF1, the spin-orbit coupling constants and pairing strengths have been tuned, so as to achieve a better agreement with the excitation spectra and odd-even mass differences in $^{251}$Cf and $^{249}$Bk. The quasiparticle properties of $^{251}$Cf and $^{249}$Bk were very well reproduced. At the same time, crucial deformed neutron and proton shell gaps open up at $N=152$ and $Z=100$, respectively. Rotational bands in Fm, No, and Rf isotopes, where experimental data are available, were also fairly well described. To help future improvements towards a more precise description, small deficiencies of the approach were carefully identified. In the $Z\approx100$ mass region, larger spin-orbit strengths than those from global adjustments lead to improved agreement with data. Puzzling effects of particle-number restoration on the calculated moment of inertia, at odds with the experimental behaviour, require further scrutiny.Comment: 9 pages, 10 figures; to be published in Physical Review

Two-photon transport through a waveguide coupling to a whispering gallery resonator containing an atom and photon-blockade effect

We investigate the two-photon transport through a waveguide side-coupling to a whispering-gallery-atom system. Using the Lehmann-Symanzik-Zimmermann (LSZ) reduction approach, we present the general formula for the two-photon processes including the two-photon scattering matrices, the wavefunctions and the second order correlation functions of the out-going photons. Based on the exact results of the second order correlation functions, we analyze the quantum statistics behaviors of the out-going photons for two different cases: (a) the ideal case without the inter-modal coupling in the whispering gallery resonator; (b) the case in the presence of the inter-modal coupling which leads to more complex nonlinear behavior. In the ideal case, we show that the system consists of two independent scattering pathways, a free pathway by a cavity mode without atomic excitation, and a "Jaynes-Cummings" pathway described by the Jaynes-Cummings Hamiltonian of a single-mode cavity coupling to an atom. The free pathway does not contribution to correlated two-photon processes. In the presence of intermodal mixing, the system no longer exhibit a free resonant pathway. Instead, both the single-photon and the two photon transport properties depend on the position of the atom. Thus, in the presence of intermodal mixing one can in fact tune the photon correlation properties by changing the position of the atom. Our formalism can be used to treat resonator and cavity dissipation as well.Comment: 9 pages, 7 figure

Deformations and quasiparticle spectra of nuclei in the nobelium region

We have performed self-consistent Skyrme Hartree-Fock-Bogolyubov calculations for nuclei close to $^{254}$No. Self-consistent deformations, including $\beta_{2,4,6,8}$ as functions of the rotational frequency, were determined for even-even nuclei $^{246,248,250}$Fm, $^{252,254}$No, and $^{256}$Rf. The quasiparticle spectra for N=151 isotones and Z=99 isotopes were calculated and compared with experimental data and the results of Woods-Saxon calculations. We found that our calculations give high-order deformations similar to those obtained for the Woods-Saxon potential, and that the experimental quasiparticle energies are reasonably well reproduced.Comment: 6 pages, 2 figures; ICFN5 conference proceeding

Structure and superconductivity in the binary Re1−x_{1-x}Mox_x alloys

The binary Re$_{1-x}$Mo$_x$ alloys, known to cover the full range of solid solutions, were successfully synthesized and their crystal structures and physical properties investigated via powder x-ray diffraction, electrical resistivity, magnetic susceptibility, and heat capacity. By varying the Re/Mo ratio we explore the full Re$_{1-x}$Mo$_x$ binary phase diagram, in all its four different solid phases: hcp-Mg ($P6_3/mmc$), $\alpha$-Mn ($I\overline{4}3m$), $\beta$-CrFe ($P4_2/mnm$), and bcc-W ($Im\overline{3}m$), of which the second is non-centrosymmetric with the rest being centrosymmetric. All Re$_{1-x}$Mo$_x$ alloys are superconductors, whose critical temperatures exhibit a peculiar phase diagram, characterized by three different superconducting regions. In most alloys the $T_c$ is almost an order of magnitude higher than in pure Re and Mo. Low-temperature electronic specific-heat data evidence a fully-gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling across the series. Considering that several $\alpha$-Mn-type Re$T$ alloys ($T$ = transition metal) show time-reversal symmetry breaking (TRSB) in the superconducting state, while TRS is preserved in the isostructural Mg$_{10}$Ir$_{19}$B$_{16}$ or Nb$_{0.5}$Os$_{0.5}$, the Re$_{1-x}$Mo$_x$ alloys represent another suitable system for studying the interplay of space-inversion, gauge, and time-reversal symmetries in future experiments expected to probe TRSB in the Re$T$ family.Comment: 8 pages, 7 figures, accepted for publication on Physical Review Material

A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

A comprehensive model atom for Fe with more than 3000 energy levels is presented. As a test and first application of this model atom, Fe abundances are determined for the Sun and five stars with well determined stellar parameters and high-quality observed spectra. Non-LTE leads to systematically depleted total absorption in the Fe I lines and to positive abundance corrections in agreement with the previous studies, however, the magnitude of non-LTE effect is smaller compared to the earlier results. Non-LTE corrections do not exceed 0.1 dex for the solar metallicity and mildly metal-deficient stars, and they vary within 0.21 dex and 0.35 dex in the very metal-poor stars HD 84937 and HD 122563, respectively, depending on the assumed efficiency of collisions with hydrogen atoms. Based on the analysis of the Fe I/Fe II ionization equilibrium in these two stars, we recommend to apply the Drawin formalism in non-LTE studies of Fe with a scaling factor of 0.1. For the Fe II lines, non-LTE corrections do not exceed 0.01 dex in absolute value. The solar non-LTE abundance obtained from 54 Fe I lines is 7.56+-0.09 and the abundance from 18 Fe II lines varies between 7.41+-0.11 and 7.56+-0.05 depending on the source of the gf-values. Thus, gf-values available for the iron lines are not accurate enough to pursue high-accuracy absolute abundance determinations. Lines of Fe I give, on average, a 0.1 dex lower abundance compared to those of Fe II lines for HD 61421 and HD 102870, even when applying a differential analysis relative to the Sun. A disparity between Fe I and Fe II points to problems of stellar atmosphere modelling or/and effective temperature determination.Comment: 19 pages, 8 figures, online material, accepted by A&

Microbubble Cavitation Imaging

Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications such as sonothrombolysis (STL) in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (moderate oscillations, stable cavitation, and inertial cavitation) and activity level in and around a treatment area. Acoustic passive cavitation detectors (PCDs) have been used to this end but do not provide spatial information. This paper presents a prototype of a 2-D cavitation imager capable of producing images of the dominant cavitation state and activity level in a region of interest. Similar to PCDs, the cavitation imaging described here is based on the spectral analysis of the acoustic signal radiated by the cavitating microbubbles: ultraharmonics of the excitation frequency indicate stable cavitation, whereas elevated noise bands indicate inertial cavitation; the absence of both indicates moderate oscillations. The prototype system is a modified commercially available ultrasound scanner with a sector imaging probe. The lateral resolution of the system is 1.5 mm at a focal depth of 3 cm, and the axial resolution is 3 cm for a therapy pulse length of 20 mu s. The maximum frame rate of the prototype is 2 Hz. The system has been used for assessing and mapping the relative importance of the different cavitation states of a microbubble contrast agent. In vitro (tissue-mimicking flow phantom) and in vivo (heart, liver, and brain of two swine) results for cavitation states and their changes as a function of acoustic amplitude are presented