Snorre Farner

Evidence for Unconventional Superconductivity of Sr2RuO4 from Specific-Heat Measurements.

We measured the specific heat of single crystals of non-cuprate layered perovskite superconductor Sr 2 RuO 4 . The crystals with different T c up to 1.2 K exhibit a large residual electronic coefficient γ 0 , which decreases systematically with increasing T c . This behavior is consistent with the presence of nodes in the superconducting gap and with the variations of T c due to pair breaking by impurities and defects. To quantitatively account for the observed large γ 0 , however, we need to introduce additional mechanism.

Contribution to harmonic balance calculations of self-sustained periodic oscillations with focus on single-reed instruments

The harmonic balance method (HBM) was originally developed for finding periodic solutions of electronical and mechanical systems under a periodic force, but has been adapted to self-sustained musical instruments. Unlike time-domain methods, this frequency-domain method does not capture transients and so is not adapted for sound synthesis. However, its independence of time makes it very useful for studying any periodic solution, whether stable or unstable, without care of particular initial conditions in time. A computer program for solving general problems involving nonlinearly coupled exciter and resonator, HARMBAL, has been developed based on the HBM. The method as well as convergence improvements and continuation facilities are thoroughly presented and discussed in the present paper. Applications of the method are demonstrated, especially on problems with severe difficulties of convergence: the Helmholtz motion (square signals) of single-reed instruments when no losses are taken into account, the reed being modeled as a simple spring.

Pairing symmetry of superconducting Sr2RuO4 from specific heat measurements

Abstract We report the low temperature specific heat of single crystals of non-cuprate layered perovskite superconductor Sr2RuO4(Tc ∼ 1K). In this paper we focus on the relation between the residual value γ0 of the electronic specific heat and the specific-heat jump across Tc. The results provide strong evidence for unconventional superconducting state.

Electrophysiological Study of Algorithmically Processed Metric/Rhythmic Variations in Language and Music

This work is the result of an interdisciplinary collaboration between scientists from the fields of audio signal processing, phonetics and cognitive neuroscience aiming at studying the perception of modifications in meter, rhythm, semantics and harmony in language and music. A special time-stretching algorithm was developed to work with natural speech. In the language part, French sentences ending with tri-syllabic congruous or incongruous words, metrically modified or not, were made. In the music part, short melodies made of triplets, rhythmically and/or harmonically modified, were built. These stimuli were presented to a group of listeners that were asked to focus their attention either on meter/rhythm or semantics/harmony and to judge whether or not the sentences/melodies were acceptable. Language ERP analyses indicate that semantically incongruous words are processed independently of the subjects attention thus arguing for automatic semantic processing. In addition, metric incongruities seem to influence semantic processing. Music ERP analyses show that rhythmic incongruities are processed independently of attention, revealing automatic processing of rhythm in music.

Timbre variations as an attribute of naturalness in clarinet play

A digital clarinet played by a human and timed by a metronome was used to record two playing control parameters, the breath control and the reed displacement, for 20 repeated performances. The regular behaviour of the parameters was extracted by averaging and the fluctuation was quantified by the standard deviation. It was concluded that the movement of the parameters seem to follow rules. When removing the fluctuations of the parameters by averaging over the repetitions, the result sounded less expressive, although it still seemed to be played by a human. The variation in timbre during the play, in particular within a notes duration, was observed and then fixed while the natural temporal envelope was kept. The result seemed unnatural, indicating that the variation of timbre is important for the naturalness.