4,532 research outputs found
Coupled thermo-hydro-mechanical behaviour of a deep clay
An experimental study on Ypresian clays –one of the potential deep formations in Belgium for the geological disposal of heat-emitting radioactive waste– was undertaken to systematically study its thermal properties and coupled hydro-mechanical response during fast heating pulse tests. An accurate characterisation of the thermal properties is required for assessing the near-field perturbations around disposal galleries that the sedimentary host rock formation will undergo. A new experimental cell adapted to apply the high in situ stresses and with thermal flux sensors was used to directly measure the thermal conductivity at different sample orientations (heat flux orthogonal and parallel to bedding planes). A clear influence of the degree of saturation – despite being close to saturation – and anisotropic features on thermal conductivity have been detected. The study was complemented by performing fast heating pulse tests under constant volume on a new and fully-instrumented axisymmetric cell. The cell allowed recording the pore pressure build-up and dissipation along a heating pulse and under water-undrained conditions.Postprint (published version
Effect of Coulomb interactions on the optical properties of doped graphene
Recent optical conductivity experiments of doped graphene in the infrared
regime reveal a strong background in the energy region between the intra and
interband transitions difficult to explain within conventional pictures. We
propose a phenomenological model taking into account the marginal Fermi liquid
nature of the quasiparticles in graphene near the neutrality point that can
explain qualitatively the observed features. We also study the electronic Raman
signal and suggest that it will also be anomalous.Comment: 4 pages, 2 figure
Non-gaussianity at tree and one-loop levels from vector field perturbations
We study the spectrum P_\zeta and bispectrum B_\zeta of the primordial
curvature perturbation \zeta when the latter is generated by scalar and vector
field perturbations. The tree-level and one-loop contributions from vector
field perturbations are worked out considering the possibility that the
one-loop contributions may be dominant over the tree level terms (both (either)
in P_\zeta and (or) in B_\zeta) and viceversa. The level of non-gaussianity in
the bispectrum, f_{NL}, is calculated and related to the level of statistical
anisotropy in the power spectrum, g_\zeta. For very small amounts of
statistical anisotropy in the power spectrum, the level of non-gaussianity may
be very high, in some cases exceeding the current observational limit.Comment: LaTeX file, 11 pages, Main body: 8 pages, References: 3 pages. v2:
Minor corrections. References added. Conclusions unchanged. v3: Minor
corrections. Some references added and others updated. Version accepted for
publication in Physical Review
Exponential torsion growth for random 3-manifolds
We show that a random 3-manifold with positive first Betti number admits a tower of cyclic covers with exponential torsion growth
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