Add new figures in Tikz

Signed-off-by: Riccardo Finotello <riccardo.finotello@gmail.com>

sec/part1/fermions.tex

@@ -95,7 +95,7 @@ Their solutions are the ``holomorphic'' functions $\psi_{+}^i(\xi_+)$ and $\psi_
 }
 \begin{figure}[tbp]
   \centering
-  \includegraphics[width=0.4\linewidth]{img/point-like-defects}
+  \import{tikz}{defects.pgf}
   \caption{Propagation of the string in the presence of the worldsheet defects.}
   \label{fig:point-like-defects}
 \end{figure}
@@ -838,7 +838,7 @@ Finally we get the anti-commutation relations as
 
 \begin{figure}[tbp]
   \centering
-  \includegraphics[width=0.5\linewidth]{img/complex-plane}
+  \import{tikz}{complex_plane_defects.pgf}
   \caption{%
     Fields are glued on the $x < 0$ semi-axis with non trivial discontinuities for $x_{(t)} < x < x_{(t-1)}$ for $t = 1,\, 2,\, \dots,\, N$ and where $x_{(t)} = \exp( \htau_{E,\, (t)} )$.
   }
@@ -1636,7 +1636,7 @@ Moreover notice that for $\rL \le -1$ both $b^{(\rE)}_{\rL \le n \le 0}$ and $b^
 
 \begin{figure}[tbp]
   \centering
-  \includegraphics[width=0.5\linewidth]{img/in-annihilators.pdf}
+  \import{tikz}{inconsistent_theories.pgf}
   \caption{As a consistency condition, we have to exclude the values of
   $\rL$ for which both $b^{(
 E)}_n$ and $b^{*\, ( \brE )}_{\rL + 1 - n}$ are in-annihilators