FORM Matters: Fast Symbolic Computation under UNIX

We give a brief introduction to FORM, a symbolic programming language for massive batch operations, designed by J.A.M. Vermaseren. In particular, we stress various methods to efficiently use FORM under the UNIX operating system. Several scripts and examples are given, and suggestions on how to use the vim editor as development platform.Comment: 10 pages, PDF document (PDFLaTeX source available upon request) with 2 JPG figures; submitted to Computers & Mathematics with Application

The variational principle in transformation optics engineering and some applications

Transformation optics specializes in the engineering of advanced optical devices, and in combination with differential geometry it allows to control electromagnetic fields with artificial media in an unprecedented manner. In this work, we model transformation optics in an inherently covariant fashion starting with a fundamental Lagrangian function. As an application, we present the construction of a flat reflectionless immersion lens whose superior performance is important to applications in bio- and nano-technology.This work has been supported by the Spanish Ministerio de Ciencia e Innovacion under the grant MTM2009-08587, contract CSD2008-00066, and the FPU programme.García Meca, C.; Tung, MM. (2013). The variational principle in transformation optics engineering and some applications. Mathematical and Computer Modelling. 57(7):1773-1779. https://doi.org/10.1016/j.mcm.2011.11.035S1773177957

Acoustics in 2D Spaces of Constant Curvature

[EN] In this work, we will consider a locally homogeneous and isotropic (2+1)D spacetime of Robertson-Walker type and therefore with underlying de Sitter space.M. M. T. wishes to thank the Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (ERDF) for financial support under grant TIN2014-59294-PTung, MM.; Gambi, JM.; María Luisa García del Pino (2016). Acoustics in 2D Spaces of Constant Curvature. Springer. 483-489. https://doi.org/10.1007/978-3-319-63082-3_75S483489Beals, R., Szmigielski, J.: Meijer G-functions: a gentle introduction. Not. Am. Math. Soc. 60(7), 866–872 (2013)Chen, H.Y., Chan, C.T.: Acoustic cloaking and transformation acoustics. J. Phys. D 43(11), 113001 (2010)Choquet-Bruhat, Y., Damour, T.: Introduction to General Relativity, Black Holes, and Cosmology. Oxford University Press, Oxford (2015)Cummer, S.A.: Transformation acoustics. In: Craster, V.R., Guenneau, S. (eds.) Acoustic Metamaterials: Negative Refraction, Imaging, Lensing and Cloaking, pp. 197–218. Springer Netherlands, Dordrecht (2013)Cummer, S.A., Schurig, D.: One path to acoustic cloaking. New J. Phys. 9(3), 45–52 (2007)Islam, J.N.: An Introduction to Mathematical Cosmology. Cambridge University Press, Cambridge (2001)Kalnins, E.G.: Separation of Variables for Riemannian Spaces of Constant Curvature. Pitman Monographs and Surveys in Pure and Applied Mathematics. Longman Scientific & Technical, New York (1986)Kuchowicz, B.: Conformally flat space-time of spherical symmetry in isotropic coordinates. Int. J. Theor. Phys. 7(4), 259–262 (1973)Lanczos, C.: The Variational Principles of Mechanics. Dover Publications, New York (1970)Mechel, F.P.: Formulas of Acoustics. Springer, Berlin (2002)Norris, A.N.: Acoustic metafluids. J. Acoust. Soc. Am. 125(2), 839–849 (2009)Redkov, V.M., Ovsiyuk, E.M.: Quantum mechanics in spaces of constant curvature. In: Contemporary Fundamental Physics. Nova Science, New York (2012)Rosenberg, S.: The Laplacian on a Riemannian Manifold: An Introduction to Analysis on Manifolds. London Mathematical Society Student Text, vol. 31. Cambridge University Press, Cambridge (1997)Tung, M.M.: A fundamental Lagrangian approach to transformation acoustics and spherical spacetime cloaking. Europhys. Lett. 98, 34002–34006 (2012)Tung, M.M., Peinado, J.: A covariant spacetime approach to transformation acoustics. In: Fontes, M., Günther, M., Marheineke, N. (eds.) Progress in Industrial Mathematics at ECMI 2012. Mathematics in Industry, vol. 19. Springer, Berlin (2014)Tung, M.M., Weinmüller, E.B.: Gravitational frequency shifts in transformation acoustics. Europhys. Lett. 101, 54006–54011 (2013)Tung, M.M., Gambi, J.M., García del Pino, M.L.: Maxwell’s fish-eye in (2+1)D spacetime acoustics. In: Russo, G.R., Capasso, V., Nicosia, G., Romano, V. (eds.) Progress in Industrial Mathematics at ECMI 2014. Mathematics in Industry, vol. 22. Springer, Berlin (2016)Visser, M., Barceló, C., Liberati, S.: Analogue models of and for gravity. Gen. Rel. Grav. 34, 1719–1734 (2002)Wolf, J.A.: Spaces of Constant Curvature. American Mathematical Society, Providence, Rhode Island (2011

Gravitational frequency shifts in transformation acoustics

In metamaterial acoustics, it is conceivable that any type of fine-tuned acoustic properties far beyond those found in nature may be transferred to an appropriate medium. Effective design and engineering of these modern acoustic metadevices poses one of the forefront challenges in this field. As a practical example of a new covariant approach for modelling acoustics on spacetime manifolds, we choose to implement the acoustic analogue of the frequency shift due to gravitational time dilation. In accordance with Einstein's equivalence principle, two different spacetimes, corresponding to uniform acceleration or uniform gravity, are considered. For wave propagation in a uniformly accelerating rigid frame, an acoustic event horizon arises. The discussion includes a detailed numerical analysis for both spacetime geometries. Copyright (c) EPLA, 2013MMT wishes to thank MARKUS SCHOBINGER for an introduction to the SBVP MATLAB solver and acknowledges partial support by the Universidad Politecnica de Valencia (PAID-00-12) and the International Office of the Vienna University of Technology.Tung, MM.; Weinmüller, EB. (2013). Gravitational frequency shifts in transformation acoustics. EPL. 101(5):54006-54011. https://doi.org/10.1209/0295-5075/101/54006S5400654011101

On the inverse of the Caputo matrix exponential

[EN] Matrix exponentials are widely used to efficiently tackle systems of linear differential equations. To be able to solve systems of fractional differential equations, the Caputo matrix exponential of the index a > 0 was introduced. It generalizes and adapts the conventional matrix exponential to systems of fractional differential equations with constant coefficients. This paper analyzes the most significant properties of the Caputo matrix exponential, in particular those related to its inverse. Several numerical test examples are discussed throughout this exposition in order to outline our approach. Moreover, we demonstrate that the inverse of a Caputo matrix exponential in general is not another Caputo matrix exponential.This work has been partially supported by Spanish Ministerio de Economia y Competitividad and European Regional Development Fund (ERDF) grants TIN2017-89314-P and by the Programa de Apoyo a la Investigacion y Desarrollo 2018 of the Universitat Politecnica de Valencia (PAID-06-18) grant SP20180016.Defez Candel, E.; Tung, MM.; Chen-Charpentier, BM.; Alonso Abalos, JM. (2019). On the inverse of the Caputo matrix exponential. Mathematics. 7(12):1-11. https://doi.org/10.3390/math7121137S111712Moler, C., & Van Loan, C. (2003). Nineteen Dubious Ways to Compute the Exponential of a Matrix, Twenty-Five Years Later. SIAM Review, 45(1), 3-49. doi:10.1137/s00361445024180Ortigueira, M. D., & Tenreiro Machado, J. A. (2015). What is a fractional derivative? Journal of Computational Physics, 293, 4-13. doi:10.1016/j.jcp.2014.07.019Caputo, M. (1967). Linear Models of Dissipation whose Q is almost Frequency Independent--II. Geophysical Journal International, 13(5), 529-539. doi:10.1111/j.1365-246x.1967.tb02303.xRodrigo, M. R. (2016). On fractional matrix exponentials and their explicit calculation. Journal of Differential Equations, 261(7), 4223-4243. doi:10.1016/j.jde.2016.06.023Garrappa, R., & Popolizio, M. (2018). Computing the Matrix Mittag-Leffler Function with Applications to Fractional Calculus. Journal of Scientific Computing, 77(1), 129-153. doi:10.1007/s10915-018-0699-

Numerical approximations of second-order matrix differential equations using higher-degree splines

Many studies of mechanical systems in engineering are based on second-order matrix models. This work discusses the second-order generalization of previous research on matrix differential equations dealing with the construction of approximate solutions for non-stiff initial problems Y 00(x) = f(x, Y (x), Y 0 (x)) using higher-degree matrix splines without any dimensional increase. An estimation of the approximation error for some illustrative examples are presented by using Mathematica. Several MatLab functions have also been developed, comparing, under equal conditions, accuracy and execution times with built-in MatLab functions. Experimental results show the advantages of solving the above initial problem by using the implemented MatLab functions.The authors wish to thank for financial support by the Universidad Politecnica de Valencia [grant number PAID-06-11-2020].Defez Candel, E.; Tung ., MM.; Solis Lozano, FJ.; Ibáñez González, JJ. (2015). Numerical approximations of second-order matrix differential equations using higher-degree splines. Linear and Multilinear Algebra. 63(3):472-489. https://doi.org/10.1080/03081087.2013.873427S472489633Loscalzo, F. R., & Talbot, T. D. (1967). Spline Function Approximations for Solutions of Ordinary Differential Equations. SIAM Journal on Numerical Analysis, 4(3), 433-445. doi:10.1137/0704038Al-Said, E. A. (2001). The use of cubic splines in the numerical solution of a system of second-order boundary value problems. Computers & Mathematics with Applications, 42(6-7), 861-869. doi:10.1016/s0898-1221(01)00204-8Al-Said, E. A., & Noor, M. A. (2003). Cubic splines method for a system of third-order boundary value problems. Applied Mathematics and Computation, 142(2-3), 195-204. doi:10.1016/s0096-3003(02)00294-1Kadalbajoo, M. K., & Patidar, K. C. (2002). Numerical solution of singularly perturbed two-point boundary value problems by spline in tension. Applied Mathematics and Computation, 131(2-3), 299-320. doi:10.1016/s0096-3003(01)00146-1Micula, G., & Revnic, A. (2000). An implicit numerical spline method for systems for ODEs. Applied Mathematics and Computation, 111(1), 121-132. doi:10.1016/s0096-3003(98)10111-xDefez, E., Soler, L., Hervás, A., & Santamaría, C. (2005). Numerical solution ofmatrix differential models using cubic matrix splines. Computers & Mathematics with Applications, 50(5-6), 693-699. doi:10.1016/j.camwa.2005.04.012Defez, E., Hervás, A., Soler, L., & Tung, M. M. (2007). Numerical solutions of matrix differential models using cubic matrix splines II. Mathematical and Computer Modelling, 46(5-6), 657-669. doi:10.1016/j.mcm.2006.11.027Ascher, U., Pruess, S., & Russell, R. D. (1983). On Spline Basis Selection for Solving Differential Equations. SIAM Journal on Numerical Analysis, 20(1), 121-142. doi:10.1137/0720009Brunner, H. (2004). On the Divergence of Collocation Solutions in Smooth Piecewise Polynomial Spaces for Volterra Integral Equations. BIT Numerical Mathematics, 44(4), 631-650. doi:10.1007/s10543-004-3828-5Tung, M. M., Defez, E., & Sastre, J. (2008). Numerical solutions of second-order matrix models using cubic-matrix splines. Computers & Mathematics with Applications, 56(10), 2561-2571. doi:10.1016/j.camwa.2008.05.022Defez, E., Tung, M. M., Ibáñez, J. J., & Sastre, J. (2012). Approximating and computing nonlinear matrix differential models. Mathematical and Computer Modelling, 55(7-8), 2012-2022. doi:10.1016/j.mcm.2011.11.060Claeyssen, J. R., Canahualpa, G., & Jung, C. (1999). A direct approach to second-order matrix non-classical vibrating equations. Applied Numerical Mathematics, 30(1), 65-78. doi:10.1016/s0168-9274(98)00085-3Froese, C. (1963). NUMERICAL SOLUTION OF THE HARTREE–FOCK EQUATIONS. Canadian Journal of Physics, 41(11), 1895-1910. doi:10.1139/p63-189Marzulli, P. (1991). Global error estimates for the standard parallel shooting method. Journal of Computational and Applied Mathematics, 34(2), 233-241. doi:10.1016/0377-0427(91)90045-lShore, B. W. (1973). Comparison of matrix methods applied to the radial Schrödinger eigenvalue equation: The Morse potential. The Journal of Chemical Physics, 59(12), 6450-6463. doi:10.1063/1.1680025ZHANG, J. F. (2002). OPTIMAL CONTROL FOR MECHANICAL VIBRATION SYSTEMS BASED ON SECOND-ORDER MATRIX EQUATIONS. Mechanical Systems and Signal Processing, 16(1), 61-67. doi:10.1006/mssp.2001.1441Flett, T. M. (1980). Differential Analysis. doi:10.1017/cbo978051189719

Improvement on the bound of Hermite matrix polynomials

In this paper, we introduce an improved bound on the 2-norm of Hermite matrix polynomials. As a consequence, this estimate enables us to present and prove a matrix version of the Riemann-Lebesgue lemma for Fourier transforms. Finally, our theoretical results are used to develop a novel procedure for the computation of matrix exponentials with a priori bounds. A numerical example for a test matrix is provided. © 2010 Elsevier Inc. All rights reserved.This work has been partially supported by the Universidad Politecnica de Valencia under project PAID-06-07/3283 and the Generalitat Valenciana under project GVPRE/2008/340.Defez Candel, E.; Tung, MM.; Sastre, J. (2011). Improvement on the bound of Hermite matrix polynomials. Linear algebra and its applications. 434(8):1910-1919. https://doi.org/10.1016/j.laa.2010.12.015S19101919434