Cyclic sums of comparative indices and oscillation theory of symplectic difference systems

Volume 38, Issue 4, pp 479--501 https://dx.doi.org/10.22436/jmcs.038.04.05
Publication Date: February 11, 2025 Submission Date: August 08, 2024 Revision Date: October 26, 2024 Accteptance Date: January 08, 2025

Authors

J. Elyseeva - Department of Applied Mathematics, Moscow State University of Technology, Vadkovskii per. 3a, 101472, Moscow, Russia.


Abstract

In this paper, we generalize the notion of the comparative index which has fundamental applications in oscillation theory of symplectic difference systems and linear differential Hamiltonian systems. We introduce cyclic sums \(\mu_c(Y_1,Y_2,\ldots,Y_m)\) and \(\mu_c^{*}(Y_1,Y_2,\ldots,Y_m),\,m\ge 2\) of the comparative indices for the set of \(n\)-dimensional Lagrangian subspaces. We formulate and prove main properties of the cyclic sums, in particular, we connect the cyclic sums of the comparative indices with the number of positive and negative eigenvalues of \(mn\times mn\) symmetric matrices defined in terms of the Wronskians \(Y_i^T J Y_j\), \(i,j=1,\ldots,m.\) We present first applications of the cyclic sums in the oscillation theory of the discrete symplectic systems connecting the number of focal points of their conjoined bases with the positive and negative inertia of symmetric matrices.


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ISRP Style

J. Elyseeva, Cyclic sums of comparative indices and oscillation theory of symplectic difference systems, Journal of Mathematics and Computer Science, 38 (2025), no. 4, 479--501

AMA Style

Elyseeva J., Cyclic sums of comparative indices and oscillation theory of symplectic difference systems. J Math Comput SCI-JM. (2025); 38(4):479--501

Chicago/Turabian Style

Elyseeva, J.. "Cyclic sums of comparative indices and oscillation theory of symplectic difference systems." Journal of Mathematics and Computer Science, 38, no. 4 (2025): 479--501


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