= Instantaneous solvent term in a relaxation modulus
{title2=$G=\mu_0\delta_++G_0e^{-s/\tau}$}
For a <linear viscoelastic fluid>, write the solvent stress explicitly as $2\mu_0E(t)$, or use the displayed kernel with a causal endpoint delta satisfying $\int_0^\infty\delta_+(s)f(s)\,ds=f(0)$. If a symmetric delta is integrated with half its weight at the endpoint, its coefficient must instead be $2\mu_0$. Mixing those conventions loses a factor of two. The <Oldroyd-B model> has the displayed exponentially decaying polymer part after linearization.
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