Linear Algebra: A Modern Introduction
Linear Algebra: A Modern Introduction
4th Edition
ISBN: 9781285463247
Author: David Poole
Publisher: Cengage Learning
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help me with part b and c please. DO NOT use any AI tools. please handwrite if possible
Transcribed Image Text:2. The Klein-Gordon equation
Utt Uxx+u=0
arises in many areas of physics, including relativistic quantum mechanics. Let -∞< x < ∞, t > 0,
and consider the following initial value problem: the given initial values u(x, 0) and ut(x, 0) are
real, and we assume that u → 0 sufficiently rapidly as |x| →∞.
(a) Show that the dispersion relation for the wave solution u = ei(kx-wt) is given by w2 = 1+k2.
Further, show that the phase speed c(k) = w/k satisfies |c(k)| ≥ 1, while for the group velocity
C(k) = we have |C(k)| ≤ 1.
=
dw
dk
(b) Establish that the Fourier transform solution is given by
1
u(x,t) = 2/7/7 √∞
= ∞ (A(k)e' (k+t√k2+1) + B(k)e3(k=−t√k2+1)) dk.
2πT
Further, show that, in view of the fact that u(x, 0) and ut(x, 0) are real we indeed have
1
u(x,t) =
2πT
·S∞ (A(k)ei(kz+t√k2+1)) dk + (*),
where (*) denotes the complex conjugate of the first integral.
(c) Show that as t∞ with x/t fixed, |x/t| < 1, we have
1
u(x, t) ~
t
-x
A
√√2π (t2x2)3/4
ei√t2−x2+i1 + (*).
+2
x2
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