# Representation of solutions to wave equations with profile functions

## TL;DR

This paper introduces a simplified reconstruction method for wave equation solutions that approximates the evolution operator for large times by reducing the problem to a one-dimensional profile evolution.

## Contribution

It presents a novel three-step reconstruction formula that simplifies wave equation analysis by focusing on profile functions and shell operators, valid for large time scales.

## Key findings

- Provides an explicit approximation for wave solutions at large times
- Reduces the wave problem to a one-dimensional profile evolution
- Proves the approximation's accuracy for times of order ^{-2}.

## Abstract

Solutions to the wave equation with constant coefficients in $\mathbb{R}^d$ can be represented explicitly in Fourier space. We investigate a reconstruction formula, which provides an approximation of solutions $u(.,t)$ to initial data $u_0(.)$ for large times. The reconstruction consists of three steps: 1) Given $u_0$, initial data for a profile equation are extracted. 2) A profile evolution equation determines the shape of the profile at time $\tau = \varepsilon^2 t$. 3) A shell reconstruction operator transforms the profile to a function on $\mathbb{R}^d$. The sketched construction simplifies the wave equation, since only a one-dimensional problem in an $O(1)$ time span has to be solved. We prove that the construction provides a good approximation to the wave evolution operator for times $t$ of order $\varepsilon^{-2}$.