Probing the matter term at long baseline experiments

We consider (\nu_\mu --> \nu_e) oscillations in long baseline experiments within a three flavor framework. A non-zero measurement of this oscillation probability implies that the (13) mixing angle `phi' is non-zero. We consider the effect of neutrino propagation through the matter of earth's crust and show that, given the constraints from solar neutrino and CHOOZ data, matter effects enhance the mixing for neutrinos rather than for anti-neutrinos. We need data from two different experiments with different baseline lengths (such as K2K and MINOS) to distinguish matter effects unambiguously.Comment: 9 pages including three figure

Localized electromechanical interactions in ferroelectric P(VDF-TrFE) nanowires investigated by scanning probe microscopy

We investigate the electromechanical interactions in individual polyvinylidene fluoride-trifluoroethylene nanowires in response to localized electrical poling via a conducting atomic force microscope tip. Spatially resolved measurements of piezoelectric coefficients and elastic moduli before and after poling reveal a striking dependence on the polarity of the poling field, notably absent in thin films of the same composition. These observations are attributed to the unclamped nature of the nanowires and the inherent asymmetry in their chemical and electrical interactions with the tip and underlying substrate. Our findings provide insights into the mechanism of poling/switching in polymer nanowires critical to ferroelectric device performance.S.K.-N. and Y.C. are grateful for financial support from the European Research Council through an ERC Starting Grant (Grant No. ERC-2014-STG-639526, NANOGEN). R.A.W. thanks the EPSRC Cambridge NanoDTC, EP/G037221/1, for studentship funding. Q.J. is grateful for financial support through a Marie Sklodowska Curie Fellowship, H2020-MSCA-IF-2015-702868

Development of high power transferred electron effect devices for X-band and Ku-band oscillators

High power transferred electron effect devices for superhigh frequency oscillator

Phenomenology of Neutrino Oscillations

The phenomenology of solar, atmospheric, supernova and laboratory neutrino oscillations is described. Analytical formulae for matter effects are reviewed. The results from oscillations are confronted with neutrinoless double beta decay.Comment: 11 pages, 2 figures, latex, Plenary talk given at Workshop in High Energy Particle Physics-6, Chennai, Indi

Solar Neutrinos and the Eclipse Effect

The solar neutrino counting rate in a real time detector like Super--Kamiokanda, SNO, or Borexino is enhanced due to neutrino oscillations in the Moon during a partial or total solar eclipse. The enhancement is calculated as a function of the neutrino parameters in the case of three flavor mixing. This enhancement, if seen, can further help to determine the neutrino parameters.Comment: 24 Pages Revtex, 8 figures as one ps file. To appear in Phys. Rev. D; Some typos corrected and a reference adde

Vertically Self-Gravitating ADAFs in the Presence of Toroidal Magnetic Field

Force due to the self-gravity of the disc in the vertical direction is considered to study its possible effects on the structure of a magnetized advection-dominated accretion disc. We present steady-sate self similar solutions for the dynamical structure of such a type of the accretion flows. Our solutions imply reduced thickness of the disc because of the self-gravity. It also imply that the thickness of the disc will increase by adding the magnetic field strength.Comment: Accepted for publication in Astrophysics and Space Science

Observation of Confinement-Induced Self-Poling Effects in Ferroelectric Polymer Nanowires Grown by Template Wetting

Ferroelectric polymer nanowires grown using a template-wetting method are shown to achieve an orientated 'self-poled' structure resulting from the confined growth process. Self-poling is highly desirable as it negates the need for high electric fields, mechanical stretching and/or high temperatures typically associated with poling treatments in ferroelectric polymers, as required for piezoelectric and/or pyroelectric applications. Here, we present differential scanning calorimetry, infrared spectroscopy and dielectric permittivity measurements on as-fabricated template-grown polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) nanowires, and quantitatively compare the results with spin-cast films of the same composition that have been electrically poled, both before and after subsequent de-poling temperature treatment. The measurements reveal remarkably similar trends between the physical properties of the as-grown nanowires and the electrically poled film samples, providing insight into the material structure of the 'self-poled' nanowires. In addition, piezo-response force microscopy (PFM) data is presented that allow s for unambiguous identification of self-poling in ferroelectric polymer nanostructures, and indicates the suitability of the template-wetting approach in fabricating nanowires that can be used directly for piezoelectric/pyroelectric applications, without the need for post-deposition poling/processing.The authors are grateful for financial support from the European Research Council through an ERC Starting Grant (Grant no. ERC-2014-STG-639526, NANOGEN). R.A.W. thanks the EPSRC Cambridge NanoDTC, EP/G037221/1, for studentship funding.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Wiley

Piezoelectric Semiconducting Nanowires

© 2018 Elsevier Inc. Piezoelectric semiconducting nanowires have generated much interest due to the interplay of their mechanical, electrical, and optical properties, which paves the way for potential applications in mechanical energy harvesting as well as sensing. The nature of piezoelectricity in these nanowires is governed by the crystalline phases present, which in turn can be controlled during the nanowire growth process. This chapter provides insight into the manifestation of piezoelectricity in semiconducting nanowires, the effect of growth on their piezoelectric properties, and importantly, how piezoelectricity is characterized at the nanoscale in these materials. Energy-related applications of semiconducting piezoelectric nanowires are described in detail, including their incorporation into nanogenerators for energy harvesting, as well as in piezotronic and photo-piezotronics devices based on the electromechanical and opto-electromechanical interactions taking place in piezoelectric semiconductor-nanowire junction-based devices. Advances in nanofabrication, nanoscale characterization, and device engineering, coupled with a greater understanding and control of piezoelectricity in semiconducting nanowires, will ultimately help unlock the full potential of these fascinating nanomaterials.European Research Council (Grant no. ERC–2014–STG–639526, NANOGEN

Cluster Cores, Gravitational Lensing, and Cosmology

Many multiply--imaged quasars have been found over the years, but none so far with image separation in excess of 8\arcsec. The absence of such large splittings has been used as a test of cosmological models: the standard Cold Dark Matter model has been excluded on the basis that it predicts far too many large--separation double images. These studies assume that the lensing structure has the mass profile of a singular isothermal sphere. However, such large splittings would be produced by very massive systems such as clusters of galaxies, for which other gravitational lensing data suggest less singular mass profiles. Here we analyze two cases of mass profiles for lenses: an isothermal sphere with a finite core radius (density $\rho \propto (r^2+r_{core}^2)^{-1})$, and a Hernquist profile ($\rho \propto r^{-1}(r+a)^{-3}$). We find that small core radii $r_{core} \sim 30 h^{-1}$ kpc, as suggested by the cluster data, or large a \gsim 300 h^{-1} kpc, as needed for compatibility with gravitational distortion data, would reduce the number of large--angle splittings by an order of magnitude or more. Thus, it appears that these tests are sensitive both to the cosmological model (number density of lenses) and to the inner lens structure, which is unlikely to depend sensitively on the cosmology, making it difficult to test the cosmological models by large--separation quasar lensing until we reliably know the structure of the lenses themselves.Comment: 17 pages, uuencoded compressed tarred postscript file including text and 1 figure. To appear in January 20, 1996 issue of ApJ Letter

Hierarchical Four-Neutrino Oscillations With a Decay Option

We present a new and novel synthesis of all existing neutrino data regarding the disappearance and appearance of $\nu_e$ and $\nu_\mu$. We assume four neutrinos: $\nu_e, \nu_\mu, \nu_\tau$, as well as a heavier singlet neutrino $\nu_s$ of a few eV. The latter may decay into a massless Goldstone boson (the singlet Majoron) and a linear combination of the doublet antineutrinos. We comment on how this scenario may be verified or falsified in future experiments.Comment: 13 pages, no figur