deletions | additions       diff --git a/Introduction.tex b/Introduction.tex  index 8f917fb..baa0ae6 100644  --- a/Introduction.tex  +++ b/Introduction.tex 
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In metals, transition from first to second regime occurs approximately about 10$^7$ W.cm$^{-2}$. This is equal to the energy of the laser we used, so the predominant regime in our experiment cannot be determined yet.  In the thermoelastic regime, a local dilatation of the medium occurs. In an unbounded solid, this would lead to a curl-free displacement, so no shear wave would occur. However, in the case presented, the solid is semi-infinite (the laser beam is absorbed on one side of the medium), and the local expansion acts as dipolar forces parallel to the surface. A unidimension analysis lead to a local displacement $u_z$ along $z$ #: \cite{scruby1990laser}:  \begin{equation}  u_z = \frac{3 \lambda + 2 \mu}{\lambda + 2\mu} \frac{\alpha \E}{\rho C S}  \label{eq:deplUnidim} 
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