Analytic regularity for a class of semi-linear weakly hyperbolic equations of second order

A class of semi-linear weakly hyperbolic equations of second order in 1 space dimension is considered. Using the properties of the analytic functions we give energy estimates for the solutions and then we prove the propagation of the analytic regularity.     

Theory of degenerate second order hyperbolic equations

Yakutsk. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 31, No. 2, pp. 68–75, March–April, 1990.     

Circulant preconditioners for second order hyperbolic equations

Linear systems arising from implicit time discretizations and finite difference space discretizations of second-order hyperbolic equations in two dimensions are considered. We propose and analyze the use of circulant preconditioners for the solution of linear systems via preconditioned iterative methods such as the conjugate gradient method. Our motivation is to exploit the fast inversion of circulant systems with the Fast Fourier Transform (FFT). For second-order hyperbolic equations with initial and Dirichlet boundary conditions, we prove that the condition number of the preconditioned system is ofO() orO(m), where is the quotient between the time and space steps andm is the number of interior gridpoints in each direction. The results are extended to parabolic equations. Numerical experiments also indicate that the preconditioned systems exhibit favorable clustering of eigenvalues that leads to a fast convergence rate.     

On third order hyperbolic equations

We shall consider the third order hyperbolic equation in [0,T] ×Rx where α≥ 2, Β ≥ 1, η ≥ 0, λ ≥ 0, Σ≥ 0, Μ ≥ 0, Ω ≥ 0 and θ≥ 0 are integers. We prove that the Cauchy problem (1) is Gevrey well-posed.     

On the Cauchy problem for finitely degenerate hyperbolic equations of second order

This paper is devoted to the study of the Cauchy problem inC ^∞ and in the Gevrey classes for some second order degenerate hyperbolic equations with time dependent coefficients and lower order terms satisfying a suitable Levi condition.     

On energy estimates for second order hyperbolic equations with Levi conditions for higher order regularity

We consider energy estimates for second order homogeneous hyperbolic equations with time dependent coefficients. The property of energy conservation, which holds in the case of constant coefficients, does not hold in general for variable coefficients; in fact, the energy can be unbounded as t → ∞ in this case. The conditions to the coefficients for the generalized energy conservation (GEC), which is an equivalence of the energy uniformly with respect to time, has been studied precisely for wave type equations, that is, only the propagation speed is variable. However, it is not true that the same conditions to the coefficients conclude (GEC) for general homogeneous hyperbolic equations. The main purpose of this paper is to give additional conditions to the coefficients which provide (GEC); they will be called as C ^k -type Levi conditions due to the essentially same meaning of usual Levi condition for the well-posedness of weakly hyperbolic equations.     

On a class of semilinear weakly hyperbolic equations

Abstract  In this paper, we deal with some global existence results for the large data smooth solutions of the Cauchy Problem associated with the semilinear weakly hyperbolic equations

A class of second order differential equations

We study the differential equationf″=N(f)f′ ² +M(f)f′+L(f), whereL, M, N are rational functions, and prove that if the differential equation has a transcendental meromorphic solutionf with order,p(f)>2, then the differential equation must be one of nine forms; and, moreover, we construct examples showing the existence of these nine forms with a transcendental meromorphic solution.     

Representation of solutions of second order one-dimensional model hyperbolic equations

We study the Fourier-Walsh spectrum \(\{ \widehat \mu (S);S \subset \{ 1, \ldots n\} \} \) of the Moebius function µ restricted to {0, 1, 2, …, 2ⁿ ? 1} ? {0, 1}ⁿ and prove that it is not captured by levels \(\{ \widehat \mu (S):|S| < \rho n\} \), with ρ a sufficiently small constant. This improves the author’s earlier result in [B2].     

Oscillatory properties for semilinear degenerate hyperbolic equations of second order

We consider three kind of oscillatory properties of the solutions to semilinear degenerate hyperbolic equations. Several sufficient conditions for the oscillation or non-oscillation are presented. In particular, they give us the positivity of the solutions for semilinear hyperbolic equations degenerating at initial point in one space dimension. Moreover we establish a few oscillatory conditions for the solutions of the mixed problem reduced to in one space dimension.     

First Darboux problem for nonlinear hyperbolic equations of second order

We study the first Darboux problem for hyperbolic equations of second order with power nonlinearity. We consider the question of the existence and nonexistence of global solutions to this problem depending on the sign of the parameter before the nonlinear term and the degree of its nonlinearity. We also discuss the question of local solvability of the problem.     

Time regularity of the solutions to second order hyperbolic equations

We consider the Cauchy problem for a second order weakly hyperbolic equation, with coefficients depending only on the time variable. We prove that if the coefficients of the equation belong to the Gevrey class g^s₀\gamma^{s_{0}} and the Cauchy data belong to g^s₁\gamma^{s_{1}}, then the Cauchy problem has a solution in  g^s₀([0,T^*];g^s₁(\mathbbR))\gamma^{s_{0}}([0,T^{*}];\gamma^{s_{1}}(\mathbb{R})) for some T ^*>0, provided 1≤s ₁≤2−1/s ₀. If the equation is strictly hyperbolic, we may replace the previous condition by 1≤s ₁≤s ₀.