arXiv subjects

Gabriele U. Varieschi

Publications and source records attributed to Gabriele U. Varieschi.

23 records · Page 2Linked to original sources

arXiv2009

Intonation and Compensation of Fretted String Instruments

In this paper we present mathematical and physical models to be used in the analysis of the problem of intonation of musical instruments such as guitars, mandolins and the like, i.e., we study how to improve the tuning on these instruments. This analysis begins by designing the placement of frets on the fingerboard according to mathematical rules and the assumption of an ideal string, but becomes more complicated when one includes the effects of deformation of the string and inharmonicity due to other string characteristics. As a consequence of these factors, perfect intonation of all the notes on the instrument can never be achieved, but complex compensation procedures are introduced and studied to minimize the problem. To test the validity of these compensation procedures, we have performed extensive measurements using standard monochord sonometers and other basic acoustical devices, confirming the correctness of our theoretical models. In particular, these experimental activities can be easily integrated into standard acoustics courses and labs, and can become a more advanced version of basic experiments with monochords and sonometers.

physics.class-ph↗

arXiv2008

Kinematical Conformal Cosmology: fundamental parameters from astrophysical observations

We continue our presentation of an alternative cosmology based on conformal gravity, following our kinematical approach introduced in a recent paper. In line with the assumptions of our model, which proposes a closed-form expression for the cosmic scale factor R(t), we first revise the Hubble and deceleration parameters and also introduce modified cosmological distances, analyzing in particular the case of the luminosity distance. Our kinematical conformal cosmology is then able to explain the anomalous acceleration of the Pioneer spacecraft, as due to a local region of gravitational blueshift. From the reported values of the Pioneer anomaly we also compute the current value of our first fundamental parameter, gamma_{0} = 1.94 x 10^{-28} cm^{-1}, in line with the original estimate by P. Mannheim of this quantity. Our second fundamental parameter, delta_{0} = 3.83 x 10^{-5}, interpreted as the current value of a cosmological time variable, is derived from a detailed fitting of type Ia Supernovae "gold-silver" data, producing Hubble plots of the same quality of those obtained by standard cosmology, but without requiring any dark matter or dark energy contribution. If further experiments will confirm the presence of an anomalous frequency blueshift in the outer region of the Solar System, as described by our model, kinematical conformal cosmology might become a viable alternative to standard cosmological theories.

astro-ph↗

arXiv2006

Eight Minutes and a Half

In this paper we describe a simple conceptual problem, regarding the actual position of the Sun at sunset or sunrise. Although this problem can be easily explained in terms of rotating frames of references and standard Coriolis Effect, it is sometimes misunderstood by students and even by some physics textbooks. We also present a simple experimental activity which can be used as a demonstration of this peculiar kinematical effect in general physics courses, or become part of laboratory activities.

physics.class-ph↗

arXiv2005

The Projectile inside the Loop

In this paper we describe an alternative use of the loop-the-loop apparatus, which can be used to study an interesting case of projectile motion. We also present an effective way to perform and analyze these experiments, by using video capture software together with a digital video camera. These experiments can be integrated into classroom demonstrations for general physics courses, or become part of laboratory activities.

physics.class-ph↗

arXiv2004

Toy Blocks and Rotational Physics

In this paper we summarize the theory of the "falling chimney," which deals with the breaking of tall structures in mid-air, when they fall to the ground. We describe how to reproduce these effects using small-scale models built with toy blocks. We also present an improved and more effective way to perform and analyze these interesting experiments, by using video capture software together with a digital video camera.

physics.class-ph↗