\begin{table}%t2
%\centering
\par
\caption{Line-force parameters.\label{tabla2}} 
$$
\begin{array}{ccc}   %{p{0.5\linewidth}l}
\hline \hline
\noalign{\smallskip}
k\;& \alpha \; & \delta \; \\%
\noalign{\smallskip}
\hline
\noalign{\smallskip}
0.212\; & 0.56\; & 0.02\; \\
\noalign{\smallskip}
\hline
\end{array}
$$
\end{table}