6,186 research outputs found
Laser Spinning of Nanotubes: A path to fast-rotating microdevices
We show that circularly polarized light can spin nanotubes with GHz
frequencies. In this method, angular moments of infrared photons are resonantly
transferred to nanotube phonons and passed to the tube body by "umklapp"
scattering. We investigate experimental realization of this ultrafast rotation
in carbon nanotubes, levitating in an optical trap and undergoing mechanical
vibrations, and discuss possible applications to rotating microdevices.Comment: 4 pages, 3 Postscript figure
Double Beta Decay
The motivation, present status, and future plans of the search for the
neutrinoless double beta decay are reviewed. It is argued that, motivated by
the recent observations of neutrino oscillations, there is a reasonable hope
that neutrinoless double beta decay corresponding to the neutrino mass scale
suggested by oscillations, of about 50 meV, actually exists. The
challenges to achieve the sensitivity corresponding to this mass scale, and
plans to overcome them, are described.Comment: 34 pages, 3 figures included, Submitted to Annu. Rev. Nucl. Part.
Sci., vol.5
Hybrid quantum/classical study of hydrogen-decorated screw dislocations in tungsten : ultrafast pipe diffusion, core reconstruction, and effects on glide mechanism
The interaction of hydrogen (H) with dislocations in tungsten (W) must be understood in order to model the mechanical response of future plasma-facing materials for fusion applications. Here, hybrid quantum mechanics/molecular mechanics (QM/MM) simulations are employed to study the ⟨111⟩ screw dislocation glide in W in the presence of H, using the virtual work principle to obtain energy barriers for dislocation glide, H segregation, and pipe diffusion. We provide a convincing validation of the QM/MM approach against full DFT energy-based methods. This is possible because the compact core and relatively weak elastic fields of ⟨111⟩ screw dislocations allow them to be contained in periodic DFT supercells. We also show that H segregation stabilizes the split-core structure while leaving the Peierls barrier almost unchanged. Furthermore, we find an energy barrier of less than 0.05 eV for pipe diffusion of H along dislocation cores. Our quantum-accurate calculations provide important reference data for the construction of larger-scale material models
Kochen-Specker set with seven contexts
The Kochen-Specker (KS) theorem is a central result in quantum theory and has
applications in quantum information. Its proof requires several yes-no tests
that can be grouped in contexts or subsets of jointly measurable tests.
Arguably, the best measure of simplicity of a KS set is the number of contexts.
The smaller this number is, the smaller the number of experiments needed to
reveal the conflict between quantum theory and noncontextual theories and to
get a quantum vs classical outperformance. The original KS set had 132
contexts. Here we introduce a KS set with seven contexts and prove that this is
the simplest KS set that admits a symmetric parity proof.Comment: REVTeX4, 7 pages, 1 figur
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