Abstract:Abstract. An exponential wave integrator sine pseudospectral method is presented and analyzed for discretizing the Klein-Gordon-Zakharov (KGZ) system with two dimensionless parameters 0 < ε ≤ 1 and 0 < γ ≤ 1 which are inversely proportional to the plasma frequency and the speed of sound, respectively. The main idea in the numerical method is to apply the sine pseudospectral discretization for spatial derivatives followed by using an exponential wave integrator for temporal derivatives in phase space. The metho… Show more
“…In the above numerical study, they paid particular attention on the resolution of different numerical methods, i.e., meshing strategy requirement (or ε-scalability) for (1.1) when 0 < ε 1. Based on their results, in order to capture "correctly" the oscillatory solution of (1.1) in practical computations, the frequently used FDTD methods request mesh size h = O(1) and time step τ = O(ε 3 ) and the EWI-FP methods require h = O(1) and τ = O(ε 2 ), when 0 < ε 1 [5,6,8]. Thus the FDTD and EWI-FP methods converge optimally in space and time for any fixed ε = ε 0 = O(1), but they do not converge when τ = O(ε).…”
We propose and analyze a multiscale time integrator Fourier pseudospectral (MTI-FP) method for solving the Klein-Gordon (KG) equation with a dimensionless parameter 0 < ε ≤ 1 which is inversely proportional to the speed of light. In the nonrelativistic limit regime, i.e., 0 < ε 1, the solution of the KG equation propagates waves with amplitude at O(1) and wavelength at O(ε 2 ) in time and O(1) in space, which causes significantly numerical burdens due to the high oscillation in time. The MTI-FP method is designed by adapting a multiscale decomposition by frequency (MDF) to the solution at each time step and applying an exponential wave integrator to the nonlinear Schrödinger equation with wave operator under well-prepared initial data for ε 2 -frequency and O(1)-amplitude waves and a KG-type equation with small initial data for the reminder waves in the MDF. We rigorously establish two independent error bounds in H 2 -norm to the MTI-FP method at O(h m 0 +τ 2 +ε 2 ) and O(h m 0 +τ 2 /ε 2 ) with h mesh size, τ time step, and m 0 ≥ 2 an integer depending on the regularity of the solution, which immediately imply that the MTI-FP converges uniformly and optimally in space with exponential convergence rate if the solution is smooth, and uniformly in time with linear convergence rate at O(τ ) for all ε ∈ (0, 1] and optimally with quadratic convergence rate at O(τ 2 ) in the regimes when either ε = O(1) or 0 < ε ≤ τ . Numerical results are reported to confirm the error bounds and demonstrate the efficiency and accuracy of the MTI-FP method for the KG equation, especially in the nonrelativistic limit regime.
“…In the above numerical study, they paid particular attention on the resolution of different numerical methods, i.e., meshing strategy requirement (or ε-scalability) for (1.1) when 0 < ε 1. Based on their results, in order to capture "correctly" the oscillatory solution of (1.1) in practical computations, the frequently used FDTD methods request mesh size h = O(1) and time step τ = O(ε 3 ) and the EWI-FP methods require h = O(1) and τ = O(ε 2 ), when 0 < ε 1 [5,6,8]. Thus the FDTD and EWI-FP methods converge optimally in space and time for any fixed ε = ε 0 = O(1), but they do not converge when τ = O(ε).…”
We propose and analyze a multiscale time integrator Fourier pseudospectral (MTI-FP) method for solving the Klein-Gordon (KG) equation with a dimensionless parameter 0 < ε ≤ 1 which is inversely proportional to the speed of light. In the nonrelativistic limit regime, i.e., 0 < ε 1, the solution of the KG equation propagates waves with amplitude at O(1) and wavelength at O(ε 2 ) in time and O(1) in space, which causes significantly numerical burdens due to the high oscillation in time. The MTI-FP method is designed by adapting a multiscale decomposition by frequency (MDF) to the solution at each time step and applying an exponential wave integrator to the nonlinear Schrödinger equation with wave operator under well-prepared initial data for ε 2 -frequency and O(1)-amplitude waves and a KG-type equation with small initial data for the reminder waves in the MDF. We rigorously establish two independent error bounds in H 2 -norm to the MTI-FP method at O(h m 0 +τ 2 +ε 2 ) and O(h m 0 +τ 2 /ε 2 ) with h mesh size, τ time step, and m 0 ≥ 2 an integer depending on the regularity of the solution, which immediately imply that the MTI-FP converges uniformly and optimally in space with exponential convergence rate if the solution is smooth, and uniformly in time with linear convergence rate at O(τ ) for all ε ∈ (0, 1] and optimally with quadratic convergence rate at O(τ 2 ) in the regimes when either ε = O(1) or 0 < ε ≤ τ . Numerical results are reported to confirm the error bounds and demonstrate the efficiency and accuracy of the MTI-FP method for the KG equation, especially in the nonrelativistic limit regime.
“…As a benchmark for comparisons, we write down the Gautschi type exponential wave integrator sine pseudospectral method (shorted as GISP) proposed in . The scheme of the GISP is given in the three level format as: choose initial values same as before and define ,, for as (2.11), then for , …”
Section: An Exponential Wave Integrator Pseudospectral Methodsmentioning
confidence: 99%
“…In this section, we shall establish the rigorous error estimate results of the EWI‐SP (2.11)–(2.13) for solving the KGZ system (2.1), where the CFL‐type condition required in is removed. We shall first give the main theorem on the error bounds in the energy space for the variables and , respectively, then prove the theorem by posterior error estimate techniques.…”
Section: Convergence Analysismentioning
confidence: 99%
“…Now, combining the Lemmas , we give the proof of Theorem by energy method with the help of mathematical induction argument , or the equivalent cutoff technique for the boundedness of numerical solutions. Proof of Theorem , from the scheme and assumption (A), we have Moreover, noting , and , we get Then by triangle inequality, …”
Section: Convergence Analysismentioning
confidence: 99%
“…By working with the two-level scheme in the correct energy space, rigorous finite time error estimates for the proposed exponential wave integrator sine pseudospectral (EWI-SP) method are established without any CFL-type conditions. The results show that the method has the same accuracy order as the one proposed in [21], that is the second order accuracy in time and spectral accuracy in space. Numerical experiments are done to justify the theoretical results.…”
We present the fourth-order compact finite difference (4cFD) discretizations for the long time dynamics of the nonlinear Klein-Gordon equation (NKGE), while the nonlinearity strength is characterized by p with a constant p ∈ N + and a dimensionless parameter ∈ (0, 1]. Based on analytical results of the lifespan of the solution, rigorous error bounds of the 4cFD methods are carried out up to the time at O(−p). We pay particular attention to how error bounds depend explicitly on the mesh size h and time step as well as the small parameter ∈ (0, 1], which indicate that, in order to obtain 'correct' numerical solutions up to the time at O(−p), the-scalability (or meshing strategy requirement) of the 4cFD methods should be taken as: h = O(p/4) and = O(p/2). It has better spatial resolution capacity than the classical second order central difference methods. By a rescaling in time, it is equivalent to an oscillatory NKGE whose solution propagates waves with wavelength at O(1) in space and O(p) in time. It is straightforward to get the error bounds of the oscillatory NKGE in the fixed time. Finally, numerical results are provided to confirm our theoretical analysis.
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