TITLE: Solving the "Transport" PDE in the sense of distributions with Dirac Delta Source
QUESTION [5 upvotes]: Let $\delta_0$ be the standard Dirac Delta distribution. I wish to solve the PDE $$u_t+cu_x=\delta_0$$ in the sense of distributions with initial condition $u(x,0)=g(x)$ for some continuous $g$. That is, I wish to find $u(x,t)$ such that
$$-\iint_\mathbb{R} u(x,t)(\phi_t+c\phi_x)dA=\phi(0,0)$$
where $\phi$ is any so-called test function.
Can anyone point in me the right direction? I tried to take a Fourier transform but that didn't seem to do much.
Edit:
To respond to a comment, taking the Fourier transform yields:
$$\mathcal{F}(u)_t+cik\mathcal{F}(u)=1$$
This is equivalent to the ODE $$f'(t)+cikf(t)=1$$
This ODE is solved by
$$\mathcal{F}(u)=f(t)=C e^{-(i kc t)} - i/(kc)$$
I'm unsure of where to go from here, or if this is correct.

REPLY [2 votes]: OP's first-order initial value problem (IVP) is
$$ \frac{\partial u(x,t)}{\partial t}+ c\frac{\partial u(x,t)}{\partial x}~=~\delta(t)\delta(x), \qquad u(x,t\!=\!0)~=~g(x).\tag{1}$$
One idea is to transform the IVP (1) into the form
$$ \frac{\partial v(x^{\prime},t^{\prime})}{\partial t^{\prime}}~=~\delta(t^{\prime})\delta(x^{\prime}), \qquad v(x^{\prime},t^{\prime}\!=\!0)~=~g(x^{\prime}),\tag{2}$$
by make a suitable linear coordinate transformation $(x,t)\mapsto (x^{\prime},t^{\prime})$. A bit of thought using the chain rule reveals that the coordinate transformation
$$ x~=~x^{\prime}+ct^{\prime}, \qquad t~=~t^{\prime}, \tag{3}$$
will do the job.
The unique solution to the IVP (2) is evidently
$$ v(x^{\prime},t^{\prime})~=~\frac{1}{2}{\rm sgn}(t^{\prime})\delta(x^{\prime})+ g(x^{\prime}). \tag{4}$$ 
Hence the unique solution to the original IVP (1) is
$$ u(x,t)~=~\frac{1}{2}{\rm sgn}(t)\delta(x\!-\!ct)+ g(x\!-\!ct). \tag{5}$$