Physics Faculty WorksCopyright (c) 2016 Loyola Marymount University and Loyola Law School All rights reserved.
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Recent documents in Physics Faculty Worksen-usSun, 30 Oct 2016 01:43:51 PDT3600Intonation and Compensation of Fretted String Instruments
http://digitalcommons.lmu.edu/phys_fac/18
http://digitalcommons.lmu.edu/phys_fac/18Fri, 28 Oct 2016 17:08:24 PDT
We discuss theoretical and physical models that are useful for analyzing the intonation of musical instruments such as guitars and mandolins and can be used to improve the tuning on these instruments. The placement of frets on the fingerboard is designed according to mathematical rules and the assumption of an ideal string. The analysis becomes more complicated when we include the effects of deformation of the string and inharmonicity due to other string characteristics. As a consequence, perfect intonation of all the notes on the instrument cannot be achieved, but complex compensation procedures can be introduced to minimize the problem. To test the validity of these procedures, we performed extensive measurements using standard monochord sonometers and other acoustical devices, confirming the correctness of our theoreticalmodels. These experimental activities can be integrated into acoustics courses and laboratories and can become a more advanced version of basic experiments with monochords and sonometers.
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Gabriele U. Varieschi et al.Toy Blocks and Rotational Physics
http://digitalcommons.lmu.edu/phys_fac/17
http://digitalcommons.lmu.edu/phys_fac/17Fri, 28 Oct 2016 17:08:18 PDT
Have you ever observed a child playing with toy blocks? A favorite game is to build towers and then make them topple like falling trees. To the eye of a trained physicist this should immediately look like an example of the physics of “falling chimneys,” when tall structures bend and break in mid-air while falling to the ground. The game played with toy blocks can actually reproduce well what is usually seen in photographs of falling towers, such as the one that appeared on the cover of the September 1976 issue of The Physics Teacher.1 In this paper we describe how we performed and analyzed these simple but interesting experiments with toy blocks.
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Gabriele U. Varieschi et al.Toy Models for the Falling Chimney
http://digitalcommons.lmu.edu/phys_fac/16
http://digitalcommons.lmu.edu/phys_fac/16Fri, 28 Oct 2016 17:08:11 PDT
In this paper we review the theory of the ‘‘falling chimney,’’ which deals with the breaking in mid-air of tall structures when they fall to the ground. We show that these ruptures can be caused by either shear forces typically developing near the base, or by the bending of the structure which is caused primarily by the internal bending moment. In the latter case the breaking is more likely to occur between one-third and one-half of the height of the chimney. Small scale toy models are used to reproduce the dynamics of the falling chimney. By examining photos taken during the fall of these models we test the adequacy of the theory. This type of experiment, which is easy to perform and conceptually challenging, can become part of a rotational mechanics lab for undergraduate students.
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Gabriele U. Varieschi et al.Wormhole Geometries in Fourth-Order Conformal Weyl Gravity
http://digitalcommons.lmu.edu/phys_fac/15
http://digitalcommons.lmu.edu/phys_fac/15Thu, 14 Jul 2016 16:21:40 PDT
We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remain the same as in the seminal study by Morris and Thorne, namely, that effective super-luminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at the junction between our solutions and flat spacetime, but we demonstrate that the averaged null energy condition (as evaluated along radial null geodesics) is satisfied for a particular set of wormhole geometries. Therefore, if fourth-order conformal Weyl gravity is a correct extension of general relativity, traversable wormholes might become a realistic solution for interstellar travel.
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Gabriele U. Varieschi et al.Astrophysical Tests of Kinematical Conformal Cosmology in Fourth-Order Conformal Weyl Gravity
http://digitalcommons.lmu.edu/phys_fac/14
http://digitalcommons.lmu.edu/phys_fac/14Thu, 14 Jul 2016 16:21:33 PDT
In this work we analyze kinematical conformal cosmology (KCC), an alternative cosmological model based on conformal Weyl gravity (CG), and test it against current type Ia supernova (SNIa) luminosity data and other astrophysical observations. Expanding upon previous work on the subject, we revise the analysis of SNIa data, confirming that KCC can explain the evidence for an accelerating expansion of the Universe without using dark energy or other exotic components. We obtain an independent evaluation of the Hubble constant, H0 = 67:53 kms-1 Mpc-1, very close to the current best estimates. The main KCC and CG parameters are re-evaluated and their revised values are found to be close to previous estimates. We also show that available data for the Hubble parameter as a function of redshift can be fitted using KCC and that this model does not suffer from any apparent age problem. Overall, KCC remains a viable alternative cosmological model, worthy of further investigation.
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Gabriele U. VarieschiKerr Metric, Geodesic Motion, and Flyby Anomaly in Fourth-Order Conformal Gravity
http://digitalcommons.lmu.edu/phys_fac/13
http://digitalcommons.lmu.edu/phys_fac/13Thu, 14 Jul 2016 16:21:27 PDT
In this paper we analyze the Kerr geometry in the context of Conformal Gravity, an alternative theory of gravitation, which is a direct extension of General Relativity (GR). Following previous studies in the literature, we introduce an explicit expression of the Kerr metric in Conformal Gravity, which naturally reduces to the standard GR Kerr geometry in the absence of Conformal Gravity effects. As in the standard case, we show that the Hamilton–Jacobi equation governing geodesic motion in a space-time based on this geometry is indeed separable and that a fourth constant of motion—similar to Carter’s constant—can also be introduced in Conformal Gravity. Consequently, we derive the fundamental equations of geodesic motion and show that the problem of solving these equations can be reduced to one of quadratures. In particular, we study the resulting time-like geodesics in Conformal Gravity Kerr geometry by numerically integrating the equations of motion for Earth flyby trajectories of spacecraft. We then compare our results with the existing data of the Flyby Anomaly in order to ascertain whether Conformal Gravity corrections are possibly the origin of this gravitational anomaly. Although Conformal Gravity slightly affects the trajectories of geodesic motion around a rotating spherical object, we show that these corrections are minimal and are not expected to be the origin of the Flyby Anomaly, unless conformal parameters are drastically different from current estimates. Therefore, our results confirm previous analyses, showing that modifications due to Conformal Gravity are not likely to be detected at the Solar System level, but might affect gravity at the galactic or cosmological scale.
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Gabriele U. VarieschiSimulating a Guitar with a Conventional Sonometer
http://digitalcommons.lmu.edu/phys_fac/12
http://digitalcommons.lmu.edu/phys_fac/12Thu, 14 Jul 2016 16:21:20 PDT
In this paper we present a simple way to convert a conventional sonometer into a simulated fretted instrument, such as a guitar or similar, by adding a fingerboard to the sonometer. In particular, we use this modified apparatus in relation to the problem of the instrument intonation, i.e., how to obtain correctly tuned notes on these string instruments. The experimental procedures presented in this study can become a more structured laboratory activity to be used in general physics courses or acoustics classes.
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Zily Burstein et al.Conformal Gravity and the Alcubierre Warp Drive Metric
http://digitalcommons.lmu.edu/phys_fac/11
http://digitalcommons.lmu.edu/phys_fac/11Thu, 14 Jul 2016 16:21:14 PDT
We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, that is, effective superluminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity is a correct extension of general relativity, superluminal motion via an Alcubierre metric might be a realistic solution, thus allowing faster-than-light interstellar travel.
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Gabriele U. Varieschi et al.Prompt Atmospheric Neutrinos and Muons: NLO versus LO QCD Predictions
http://digitalcommons.lmu.edu/phys_fac/10
http://digitalcommons.lmu.edu/phys_fac/10Thu, 07 Nov 2013 18:25:24 PSTGabriele U. VarieschiConformal Cosmology and the Pioneer Anomaly
http://digitalcommons.lmu.edu/phys_fac/9
http://digitalcommons.lmu.edu/phys_fac/9Thu, 07 Nov 2013 18:20:38 PSTGabriele U. VarieschiKinematical Conformal Cosmology: Fundamental Parameters from Astrophysical Observations
http://digitalcommons.lmu.edu/phys_fac/8
http://digitalcommons.lmu.edu/phys_fac/8Thu, 07 Nov 2013 18:20:35 PSTGabriele U. VarieschiPrompt Atmospheric Neutrinos and Muons: Dependence on the Gluon Distribution Function
http://digitalcommons.lmu.edu/phys_fac/7
http://digitalcommons.lmu.edu/phys_fac/7Thu, 07 Nov 2013 18:16:15 PSTGabriele U. VarieschiMeasuring the Prompt Atmospheric Neutrino Flux with Down-Going Muons in Neutrino Telescopes
http://digitalcommons.lmu.edu/phys_fac/6
http://digitalcommons.lmu.edu/phys_fac/6Thu, 07 Nov 2013 18:16:01 PSTGabriele U. VarieschiBounds on Relic Neutrino Masses in the Z-burst Model
http://digitalcommons.lmu.edu/phys_fac/5
http://digitalcommons.lmu.edu/phys_fac/5Thu, 07 Nov 2013 18:15:45 PSTGabriele U. VarieschiMeasurement of the Gluon Parton Distribution Function at Small x with Neutrino Telescopes
http://digitalcommons.lmu.edu/phys_fac/4
http://digitalcommons.lmu.edu/phys_fac/4Thu, 07 Nov 2013 18:15:32 PST
We analyze the possibility that neutrino telescopes may provide an experimental determination of the slope λ of the gluon distribution in the proton at momentum fractions x smaller than the accelerator reach. The method is based on a linear relation between λ and the spectral index ~slope! of the down-going atmospheric muon flux above 100 TeV, for which there is no background. Considering the uncertainties in the charm production cross section and in the cosmic ray composition, we estimate the error on the measurement of l through this method, excluding the experimental error of the telescopes, to be ±0.2.
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Gabriele U. VarieschiA Kinematical Approach to Conformal Cosmology
http://digitalcommons.lmu.edu/phys_fac/3
http://digitalcommons.lmu.edu/phys_fac/3Thu, 07 Nov 2013 18:15:25 PST
We present an alternative cosmology based on conformal gravity, as originally introduced by H. Weyl and recently revisited by P. Mannheim and D. Kazanas. Unlike past similar attempts our approach is a purely kinematical application of the conformal symmetry to the Universe, through a critical reanalysis of fundamental astrophysical observations, such as the cosmological redshift and others. As a result of this novel approach we obtain a closed-form expression for the cosmic scale factor R(t) and a revised interpretation of the space-time coordinates usually employed in cosmology. New fundamental cosmological parameters are introduced and evaluated. This emerging new cosmology does not seem to possess any of the controversial features of the current standard model, such as the presence of dark matter, dark energy or of a cosmological constant, the existence of the horizon problem or of an inﬂationary phase. Comparing our results with current conformal cosmologies in the literature, we note that our kinematic cosmology is equivalent to conformal gravity with a cosmological constant at late (or early) cosmological times. The cosmic scale factor and the evolution of the Universe are described in terms of several dimensionless quantities, among which a new cosmological variable δ emerges as a natural cosmic time. The mathematical connections between all these quantities are described in details and a relationship is established with the original kinematic cosmology by L. Infeld and A. Schild. The mathematical foundations of our kinematical conformal cosmology will need to be checked against current astrophysical experimental data, before this new model can become a viable alternative to the standard theory.
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Gabriele U. VarieschiEight Minutes and a Half
http://digitalcommons.lmu.edu/phys_fac/2
http://digitalcommons.lmu.edu/phys_fac/2Thu, 07 Nov 2013 18:15:21 PSTGabriele U. VarieschiThe Projectile Inside the Loop
http://digitalcommons.lmu.edu/phys_fac/1
http://digitalcommons.lmu.edu/phys_fac/1Thu, 07 Nov 2013 18:15:14 PSTGabriele U. Varieschi