N=2 supersymmetric gauge theories and quantum integrable systems

We study N=2 supersymmetric gauge theories on the product of a two-sphere and a cylinder. We show that the low-energy dynamics of a BPS sector of such a theory is described by a quantum integrable system, with the Planck constant set by the inverse of the radius of the sphere. If the sphere is replaced with a hemisphere, then our system reduces to an integrable system of the type studied by Nekrasov and Shatashvili. In this case we establish a correspondence between the effective prepotential of the gauge theory and the Yang-Yang function of the integrable system.Comment: 24 pages. v2: references added; v3: minor changes, published versio

Heavy and light flavor jet quenching at RHIC and LHC energies

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. The dependence of the jet quenching parameter $\hat{q}$ on medium temperature and jet flavor is quantitatively extracted.Comment: 6 pages, 6 figure

Giant Strains in Non-Textured (Bi1/2Na1/2)TiO3-Based Lead-Free Ceramics

Recent intense research on lead-free piezoceramics has led to the discovery of many oxide ceramics with excellent properties.[1-4] Among reported solid solution families, the bismuth-alkali titanate-based system develops the largest strain under applied electric field (0.45%–0.48%),[5-7] making it a promising material for applications in actuators.[8, 9] However, high electric fields are required in this system, resulting in a low d33* (the large-signal piezoelectric coefficient). Values of d33* greater than 1000 pm V−1 were reported in barium titanate- and alkali-niobate-based families, but the achievable electrostrain is quite low (often below 0.3%).[10-12] Single crystals possess remarkable values for both d33* and electrostrain,[13, 14] the difficulties in fabrication and associated high cost have yet to be overcome for production in quantity. In this Communication, we report giant electrostrain (0.70%) and d33* (1400 pm V−1) in a non-textured lead-free polycrystalline ceramic. These excellent properties are attributed to electric-field-induced phase transitions, according to in situ transmission electron microscopy (TEM) examinations. The results are directly beneficial to next-generation actuators, and may also shed light on the development of deformable structural ceramics