Seed Germination in Ginkgo biloba L. I. Influences of Cold Treatment, Gibberellic Acid and Red Light

The influences of cold treatment, gibberellic acid and red light treatment on rate of germination of seeds of Ginkgo biloba L. were followed for a 12-wk period. Dispersal units were collected, and the outer fleshy layer was removed soon after harvest. Of water-imbibed, non-cold-treated seeds, 50% of those which germinated did so within 11 wk after planting. A single application of red light accelerated the 50% germination time by 3 wk. Imbibition in GA3 solution did not appear to accelerate germination. With 4-wk cold treatment the 50% germination time was accelerated 6 wk in water-imbibed seeds. Both red light and GA3 treated seeds also were accelerated 6 wk by cold treatment. An 8-wk cold treatment accelerated the 50% germination time 7 wk for all three treatment groups. The influence of red light observed on non-cold-treated seeds was not seen with seeds receiving a cold treatment prior to irradiation. A 12-wk cold treatment period delayed germination in all treated groups. Dry storage of seeds for 4mo at 25 C also delayed germination regardless of red light, GA3 or cold treatment

Intrinsic optical dichroism in the chiral superconducting state of Sr2_{2}RuO4_{4}

We present an analysis of the Hall conductivity $\sigma_{xy}(\omega, T)$ in time reversal symmetry breaking states of exotic superconductors. We find that the dichroic signal is non-zero in systems with inter-band order parameters. This new intrinsic mechanism may explain the Kerr effect observed in strontium ruthenate and possibly other superconductors. We predict coherence factor effects in the temperature dependence of the imaginary part of the ac Hall conductivity $Im\sigma_{xy}(\omega, T)$, which can be tested experimentally.Comment: 4+ pages, 4 figures, published versio

Higher Spin Superfield interactions with the Chiral Supermultiplet: Conserved Supercurrents and Cubic Vertices

We investigate cubic interactions between a chiral superfield and higher spin superfield corresponding to irreducible representations of the $4D,\, \mathcal{N}=1$ super-Poincar\'{e} algebra. We do this by demanding an invariance under the most general transformation, linear in the chiral superfield. Following Noether's method we construct an infinite tower of higher spin supercurrent multiplets which are quadratic in the chiral superfield and include higher derivatives. The results are that a single, massless, chiral superfield can couple only to the half-integer spin supermultiplets $(s+1,s+1/2)$ and for every value of spin there is an appropriate improvement term that reduces the supercurrent multiplet to a minimal multiplet which matches that of superconformal higher spins. On the other hand a single, massive, chiral superfield can couple only to higher spin supermultiplets of type $(2l+2\hspace{0.3ex},\hspace{0.1ex}2l+3/2)$ and there is no minimal multiplet. Furthermore, for the massless case we discuss the component level higher spin currents and provide explicit expressions for the integer and half-integer spin conserved currents together with a R-symmetry current

The Kerr rotation in the unconventional superconductor Sr2_2RuO4_4

The interpretation of Kerr rotation measurements in the superconducting phase of Sr$_2$RuO$_4$ is a controversial topic. Both intrinsic and extrinsic mechanisms have been proposed, and it has been argued that the intrinsic response vanishes by symmetry. We focus on the intrinsic contribution and clarify several conflicting results in the literature. On the basis of symmetry considerations and detailed calculations we show that the intrinsic Kerr signal is not forbidden in a general multi- band system but has a rich structure in the near infrared regime. We distinguish different optical transitions determined by the superconducting gap (far infrared) and the inter orbital coupling of the normal state (near infrared). We argue that the low frequency transitions do not contribute to the Hall conductivity while only the inter-orbital transitions in the near infrared regime contribute. Finally, we discuss the difficulties to connect the calculations for the optical Hall conductivity to the experimental measurement of the Kerr angle. We will compare different approximations which might lead to conflicting results.Comment: 9 pages, 8 figures, 1 tabl

Gap Nodes and Time Reversal Symmetry Breaking in Strontium Ruthenate

We study the superconducting state of Sr$_2$RuO$_4$ on the bases of a phenomenological but orbital specific description of the electron-electron attraction and a realistic quantitative account of the electronic structure in the normal state. We found that a simple model which features both `in plane' and `out of plane' coupling with strengths $U_{\parallel}=40$meV and $U_{\perp}=48$meV respectively reproduced the experimentally observed power law behaviour of the low temperature specific heat $C_v(T)$, superfluid density $n_s(T)$ and thermal conductivity in quantitative detail. Moreover, it predicts that the quasi-particle spectrum on the $\gamma$ -sheet is fully gaped and the corresponding order parameter breaks the time reversal symmetry. We have also investigated the stability of this model to inclusion of further interaction constants in particular %those which describe `proximity coupling' between orbitals contributing to the $\gamma$ sheet of the Fermi surface and the $\alpha$ and $\beta$ sheets. We found that the predictions of the model are robust under such changes. Finally, we have incorporated a description of weak disorder into the model and explored some of its consequences. For example we demonstrated that the disorder has a more significant effect on the $f$-wave component of the order parameter than on the p-wave one.Comment: EPJ B submitte