Abstract

With coupling unification and neutrino oscillation discovered, one can argue that proton decay remains as The Missing Piece of Grand Unification. The colloquium will explain why this is so and will emphasize the importance of improved searches for proton decay in a large Underground detector, which is yet to be built.

Abstract

nO is of considerable interest for optoelectronic device applications dueto its wide band gap and high exciton binding energy. In spite of decadesof study and recent progress in research on ZnO properties, there remainedunresolved controversies which are mainly related to native defects formedduring crystal growth. Positron annihilation spectroscopy (PAS) is amongthe methods to tackle this structural issue. ZnO nanostructures, like e.g.nanorods and tetrapods, are of special interest for device applications.However, their characterization remains an ongoing challenge. This talkintends to review our recent efforts and latest achievements in thisdirection. Results obtained will comprise PAS in the form of Slow PositronImplantation Spectroscopy (SPIS) and Pulsed Low Energy Positron LifetimeSpectroscopy (PLEPS), Nuclear Reaction Analysis (NRA), Atomic ForceMicroscopy (AFM), conductive AFM (C-AFM), Nuclear Magnetic Resonance(NMR), Electron Spin Resonance (ESR), Photoluminescence (PL) spectroscopy,and latest theoretical investigations of structure-related and positronproperties of selected defects. The fundamental importance of arelationship between fabrication conditions, native defect formation, andresulting optical and electronic properties is demonstrated by gettingeither inferior (nanorods) or significantly improved (tetrapods) opticalproperties compared to single crystal samples, depending on thenanostructure fabrication method.

Abstract

complete description of quantum information theory needs to incorporate simultaneously at least three important concepts or principles, namely: (a) quantum entanglement, (b) quantumcoherence versus decoherence (i.e., in the presence of dissipation),and (c) the quantum- classical limit (or quantum-classical interface). We discuss how the concept of quantum phasespace can be enlarged to provide just such a unified and consistent description. Quantum phase-space methods and, especially, such quantum phase-space distribution functionsas the P-, Q-, Wigner and Weyl functions, have played an important role over many years in quantum mechanics and such allied areas as quantum optics. We introduce here in a very fundamental manner a natural hierarchy of extended quantum phase spaces and associated extended distribution functions with the capacity to describe simultaneously both quantum noise and quantum correlations at increasingly higher-order levels. We show further how the extendedphase-space formalism provides valuable insights into the important issue of quantum versus classical correspondence, and also how it has extremely appealing properties for a consistent description of quantum information theory. At the next-to-lowest (x-p-X-P) level in the extendedhierarchy the description of mixed states becomes unified, and a very convenient means is opened up, for example, to discuss together, and on the same footing, the ordinary Wigner and Weyl functions of a quantal system. The doubling of the number of degrees of freedom, which, rather surprisingly, has its roots in classical mechanics, has strong overlaps with a similar feature of thermo-field dynamics, and hence with the treatment of quantum systems subject to thermal noise.

Swift Heavy Ion (SHI) irradiation of semiconductor nanostructures is arapidly developing area of nanomaterials research which resultssignificant changes in structural and physical properties of such lowdimensional systems. The present study describes SHI irradiation effect onbare and silica (SiO2) coated semiconductor nanoparticles embedded ininsulating polymer (polyvinyl alcohol) and on a composite of semiconductornanoparticles and conductingpolymer(2-methoxy-5-(2-ethyl-hexyloxy)-pphenylene vinylene). The nanosemiconductor samples of PbS, CdS and ZnS were prepared following aninexpensive chemical route. Characterizations of the samples were carriedout with X-ray diffraction, optical absorption spectroscopy,photoluminescence and transmission electron microscopy. The UV–Visabsorption spectra reveal blue shift relative to bulk material inabsorption energy while PL spectra suggest that surface state and nearband edge emissions are dominating in case of bare and coated samplesrespectively. The samples were irradiated with 160 MeV Ni-ion beam withfluences in the range of 1e12 to 1e13 ions/cm2. The investigation afterSHI irradiation showed fluence dependent luminescence behavior and sizeenhancement of bare nanoparticles while reduction of particle size wasobserved in the composite system. However, coated samples exhibit betterstability upon SHI irradiation compared to the bare one.