Unified Formalism for calculating Polarization, Magnetization, and more in a Periodic Insulator

In this paper, we propose a unified formalism, using Green's functions, to integrate out the electrons in an insulator under uniform electromagnetic fields. We derive a perturbative formula for the Green's function in the presence of uniform magnetic or electric fields. Applying the formula, we derive the formula for the polarization, the orbital magnetization, and the orbital magneto-polarizability, without assuming time reversal symmetry. Specifically, we realize that the terms linear in the electric field can only be expressed in terms of the Green's functions in one extra dimension. This observation directly leads to the result that the coefficient of the $\theta$ term in any dimensions is given by a Wess-Zumino-Witten-type term, integrated in the extended space, interpolating between the original physical Brillouin zone and a trivial system, with the group element replaced by the Green's function. This generalizes an earlier result for the case of time reversal invariance [see Z. Wang, X.-L. Qi, and S.-C. Zhang, Phys. Rev. Lett. {\bf 105}, 256803 (2010)].Comment: 16 pages, 1 figure. The version accepted by PR

Peak shifts due to B(∗)−Bˉ(∗)B^{(*)}-\bar{B}^{(*)} rescattering in Υ(5S)\Upsilon(5S) dipion transitions

We study the energy distributions of dipion transitions $\Upsilon(5S)$ to $\Upsilon(1S,2S,3S)\pi^+\pi^-$ in the final state rescattering model. Since the $\Upsilon(5S)$ is well above the open bottom thresholds, the dipion transitions are expected to mainly proceed through the real processes $\Upsilon(5S)\to B^{(*)}\bar{B}^{(*)}$ and $B^{(*)}\bar{B}^{(*)}\to \Upsilon(1S,2S,3S)\pi^+\pi^-$. We find that the energy distributions of $\Upsilon(1S,2S,3S)\pi^+\pi^-$ markedly differ from that of $\Upsilon(5S)\to B^{(*)}\bar{B}^{(*)}$. In particular, the resonance peak will be pushed up by about 7-20 MeV for these dipion transitions relative to the main hadronic decay modes. These predictions can be used to test the final state rescattering mechanism in hadronic transitions for heavy quarkonia above the open flavor thresholds.Comment: Version published in PRD, energy dependence of the total width in Eq.(12) restored and corresponding figure changed, more discussion and clarification adde

Squeezing and entanglement of matter-wave gap solitons

We study quantum squeezing and entanglement of gap solitons in a Bose-Einstein condensate loaded into a one-dimensional optical lattice. By employing a linearized quantum theory we find that quantum noise squeezing of gap solitons, produced during their evolution, is enhanced compared with the atomic solitons in a lattice-free case due to intra-soliton structure of quantum correlations induced by the Bragg scattering in the periodic potential. We also show that nonlinear interaction of gap solitons in dynamically stable bound states can produce strong soliton entanglement.Comment: 4 pages, 5 figure

Multiple Equilibria in a Single-Column Model of the Tropical Atmosphere

A single-column model run under the weak temperature gradient approximation, a parameterization of large-scale dynamics appropriate for the tropical atmosphere, is shown to have multiple stable equilibria. Under conditions permitting persistent deep convection, the model has a statistically steady state in which such convection occurs, as well as an extremely dry state in which convection does not occur. Which state is reached depends on the initial moisture profile.Comment: Submitted to Geophysical Research Letter

Relativistic corrections to J/ψJ/\psi exclusive and inclusive double charm production at B factories

In order to clarify the puzzling problems in double charm production, relativistic corrections at order $v^{2}$ to the processes $e^{+}e^{-}\to J/\psi+\eta_{c}$ and $e^{+}e^{-}\to J/\psi+c\bar{c}$ at B factories are studied in non-relativistic quantum chromodynamics. The short-distance parts of production cross sections are calculated perturbatively, while the long-distance matrix elements are estimated from $J/\psi$ and $\eta_c$ decays up to errors of order $v^4$. Our results show that the relativistic correction to the exclusive process $e^{+}e^{-}\to J/\psi+\eta_{c}$ is significant, which, when combined together with the next-to-leading order $\alpha_{s}$ corrections, could resolve the large discrepancy between theory and experiment; whereas for the inclusive process $e^{+}e^{-}\to J/\psi+c\bar{c}$ the relativistic correction is tiny and negligible. The physical reason for the above difference between exclusive and inclusive processes largely lies in the fact that in the exclusive process the relative momentum between quarks in charmonium substantially reduces the virtuality of the gluon that converts into a charm quark pair, but this is not the case for the inclusive process, in which the charm quark fragmentation $c\to J/\psi+c$ is significant, and QCD radiative corrections can be more essential.Comment: Version to appear in PRD. In the summary an explicit statement added: "for the J/\psi eta_c cross section the relativistic correction alone gives an enhancement factor of 1.7 while the combination of relativistic correction with QCD radiative correction results in a much larger enhancement factor of 9". One reference added. A few typos correcte