38 research outputs found
Small-q phonon-mediated superconductivity in organic \kappa-BEDT-TTF compounds
We propose a mew picture for superconductivity in
salts arguing that small-{\bf q} electron-phonon scattering dominates the
pairing. We reproduce the distinct X-shaped d-wave gap reported recently by
magnetooptic measurements and we argue that the softness of the momentum
structure of the gap and the near degeneracy of s- and d-wave gap states may be
at the origin of the experimental controversy about the gap symmetry. We show
that a magnetic field applied parallel to the planes may induce extended
gapless-regions on the FS accounting for the experimental signatures of a
Fulde-Ferrel-Larkin-Ovchinikov state and it may induce gap symmetry transitions
as well.Comment: 4 pages and 7 figure
Gravitational Waves from a Pulsar Kick Caused by Neutrino Conversions
It has been suggested that the observed pulsar velocities are caused by an
asymmetric neutrino emission from a hot neutron star during the first seconds
after the supernova collapse. We calculate the magnitude of gravitational waves
produced by the asymmetries in the emission of neutrinos. The resulting
periodic gravitational waves may be detectable by LIGO and LISA in the event of
a nearby supernova explosion.Comment: 15 pages, 2 figure
Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
This is the author accepted manuscript. the final version is available from EDP Sciences via the DOI in this recordThe highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A∗ is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU ≈ 1400 Schwarzschild radii, the star has an orbital speed of ≈ 7650 km s-1, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Δλ / λ ≈ 200 km s-1/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 ± 0.09|stat ± 0.15|sys. The S2 data are inconsistent with pure Newtonian dynamics
Elastic Properties of Fullerenes
We report on ultrasonic investigations of the frequency dependent and temperature dependent sound velocity in pure C60 and in C60/C70-compounds. For both compositions of pressed bulk samples used here elastic anomalies owing to the wellknown transitions at about 260 K and 160 K are observed. Concerning the absolute values of the elastic stiffness our results differ markedly from those found by means of low frequency vibrating reed techniques on C60 single crystals