diff --git a/img/chanpaton.pdf b/img/chanpaton.pdf
deleted file mode 100644
index b32a438..0000000
Binary files a/img/chanpaton.pdf and /dev/null differ
diff --git a/img/chanpaton.pdf_tex b/img/chanpaton.pdf_tex
deleted file mode 100644
index 10e1d01..0000000
--- a/img/chanpaton.pdf_tex
+++ /dev/null
@@ -1,62 +0,0 @@
-%% Creator: Inkscape 1.0 (4035a4fb49, 2020-05-01), www.inkscape.org
-%% PDF/EPS/PS + LaTeX output extension by Johan Engelen, 2010
-%% Accompanies image file 'chanpaton.pdf' (pdf, eps, ps)
-%%
-%% To include the image in your LaTeX document, write
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics{<filename>.pdf}
-%% To scale the image, write
-%%   \def\svgwidth{<desired width>}
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics[width=<desired width>]{<filename>.pdf}
-%%
-%% Images with a different path to the parent latex file can
-%% be accessed with the `import' package (which may need to be
-%% installed) using
-%%   \usepackage{import}
-%% in the preamble, and then including the image with
-%%   \import{<path to file>}{<filename>.pdf_tex}
-%% Alternatively, one can specify
-%%   \graphicspath{{<path to file>/}}
-%% 
-%% For more information, please see info/svg-inkscape on CTAN:
-%%   http://tug.ctan.org/tex-archive/info/svg-inkscape
-%%
-\begingroup%
-  \makeatletter%
-  \providecommand\color[2][]{%
-    \errmessage{(Inkscape) Color is used for the text in Inkscape, but the package 'color.sty' is not loaded}%
-    \renewcommand\color[2][]{}%
-  }%
-  \providecommand\transparent[1]{%
-    \errmessage{(Inkscape) Transparency is used (non-zero) for the text in Inkscape, but the package 'transparent.sty' is not loaded}%
-    \renewcommand\transparent[1]{}%
-  }%
-  \providecommand\rotatebox[2]{#2}%
-  \newcommand*\fsize{\dimexpr\f@size pt\relax}%
-  \newcommand*\lineheight[1]{\fontsize{\fsize}{#1\fsize}\selectfont}%
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-      \relax%
-    \else%
-      \setlength{\unitlength}{\unitlength * \real{\svgscale}}%
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-    \setlength{\unitlength}{\svgwidth}%
-  \fi%
-  \global\let\svgwidth\undefined%
-  \global\let\svgscale\undefined%
-  \makeatother%
-  \begin{picture}(1,0.93408683)%
-    \lineheight{1}%
-    \setlength\tabcolsep{0pt}%
-    \put(0,0){\includegraphics[width=\unitlength,page=1]{chanpaton.pdf}}%
-    \put(0.23383963,0.6252787){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\lambda^1_{12}$\end{tabular}}}}%
-    \put(0.63712159,0.74159928){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\lambda^2_{23}$\end{tabular}}}}%
-    \put(0.59234979,0.2759758){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\lambda^3_{22}$\end{tabular}}}}%
-    \put(0.23684408,0.08102738){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\lambda^4_{31}$\end{tabular}}}}%
-  \end{picture}%
-\endgroup%
diff --git a/img/complex_plane.pdf b/img/complex_plane.pdf
deleted file mode 100644
index 4701f41..0000000
Binary files a/img/complex_plane.pdf and /dev/null differ
diff --git a/img/complex_plane.pdf_tex b/img/complex_plane.pdf_tex
deleted file mode 100644
index 241046f..0000000
--- a/img/complex_plane.pdf_tex
+++ /dev/null
@@ -1,65 +0,0 @@
-%% Creator: Inkscape 1.0 (4035a4fb49, 2020-05-01), www.inkscape.org
-%% PDF/EPS/PS + LaTeX output extension by Johan Engelen, 2010
-%% Accompanies image file 'complex_plane.pdf' (pdf, eps, ps)
-%%
-%% To include the image in your LaTeX document, write
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics{<filename>.pdf}
-%% To scale the image, write
-%%   \def\svgwidth{<desired width>}
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics[width=<desired width>]{<filename>.pdf}
-%%
-%% Images with a different path to the parent latex file can
-%% be accessed with the `import' package (which may need to be
-%% installed) using
-%%   \usepackage{import}
-%% in the preamble, and then including the image with
-%%   \import{<path to file>}{<filename>.pdf_tex}
-%% Alternatively, one can specify
-%%   \graphicspath{{<path to file>/}}
-%% 
-%% For more information, please see info/svg-inkscape on CTAN:
-%%   http://tug.ctan.org/tex-archive/info/svg-inkscape
-%%
-\begingroup%
-  \makeatletter%
-  \providecommand\color[2][]{%
-    \errmessage{(Inkscape) Color is used for the text in Inkscape, but the package 'color.sty' is not loaded}%
-    \renewcommand\color[2][]{}%
-  }%
-  \providecommand\transparent[1]{%
-    \errmessage{(Inkscape) Transparency is used (non-zero) for the text in Inkscape, but the package 'transparent.sty' is not loaded}%
-    \renewcommand\transparent[1]{}%
-  }%
-  \providecommand\rotatebox[2]{#2}%
-  \newcommand*\fsize{\dimexpr\f@size pt\relax}%
-  \newcommand*\lineheight[1]{\fontsize{\fsize}{#1\fsize}\selectfont}%
-  \ifx\svgwidth\undefined%
-    \setlength{\unitlength}{220.75220544bp}%
-    \ifx\svgscale\undefined%
-      \relax%
-    \else%
-      \setlength{\unitlength}{\unitlength * \real{\svgscale}}%
-    \fi%
-  \else%
-    \setlength{\unitlength}{\svgwidth}%
-  \fi%
-  \global\let\svgwidth\undefined%
-  \global\let\svgscale\undefined%
-  \makeatother%
-  \begin{picture}(1,0.88543026)%
-    \lineheight{1}%
-    \setlength\tabcolsep{0pt}%
-    \put(0,0){\includegraphics[width=\unitlength,page=1]{complex_plane.pdf}}%
-    \put(0.27574802,0.61228508){\color[rgb]{0,0,0}\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$w$\end{tabular}}}}%
-    \put(0.50518806,0.22302129){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\abs{z_{(0)}} = e^{\tau_{E\, (0)}}$\end{tabular}}}}%
-    \put(0.67824248,0.61043922){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\abs{z_{(1)}} = e^{\tau_{E\, (1)}}$\end{tabular}}}}%
-    \put(0.83536879,0.37349547){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\Re z$\end{tabular}}}}%
-    \put(0.43673387,0.85101321){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\Im z$\end{tabular}}}}%
-    \put(0.23797204,0.25979961){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\ccC_{(0)}$\end{tabular}}}}%
-    \put(0.12028046,0.14723528){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\ccC_{(1)}$\end{tabular}}}}%
-  \end{picture}%
-\endgroup%
diff --git a/img/quark.pdf b/img/quark.pdf
deleted file mode 100644
index 5901c66..0000000
Binary files a/img/quark.pdf and /dev/null differ
diff --git a/img/quark.pdf_tex b/img/quark.pdf_tex
deleted file mode 100644
index 9628e91..0000000
--- a/img/quark.pdf_tex
+++ /dev/null
@@ -1,61 +0,0 @@
-%% Creator: Inkscape 1.0 (4035a4fb49, 2020-05-01), www.inkscape.org
-%% PDF/EPS/PS + LaTeX output extension by Johan Engelen, 2010
-%% Accompanies image file 'quark.pdf' (pdf, eps, ps)
-%%
-%% To include the image in your LaTeX document, write
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics{<filename>.pdf}
-%% To scale the image, write
-%%   \def\svgwidth{<desired width>}
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics[width=<desired width>]{<filename>.pdf}
-%%
-%% Images with a different path to the parent latex file can
-%% be accessed with the `import' package (which may need to be
-%% installed) using
-%%   \usepackage{import}
-%% in the preamble, and then including the image with
-%%   \import{<path to file>}{<filename>.pdf_tex}
-%% Alternatively, one can specify
-%%   \graphicspath{{<path to file>/}}
-%% 
-%% For more information, please see info/svg-inkscape on CTAN:
-%%   http://tug.ctan.org/tex-archive/info/svg-inkscape
-%%
-\begingroup%
-  \makeatletter%
-  \providecommand\color[2][]{%
-    \errmessage{(Inkscape) Color is used for the text in Inkscape, but the package 'color.sty' is not loaded}%
-    \renewcommand\color[2][]{}%
-  }%
-  \providecommand\transparent[1]{%
-    \errmessage{(Inkscape) Transparency is used (non-zero) for the text in Inkscape, but the package 'transparent.sty' is not loaded}%
-    \renewcommand\transparent[1]{}%
-  }%
-  \providecommand\rotatebox[2]{#2}%
-  \newcommand*\fsize{\dimexpr\f@size pt\relax}%
-  \newcommand*\lineheight[1]{\fontsize{\fsize}{#1\fsize}\selectfont}%
-  \ifx\svgwidth\undefined%
-    \setlength{\unitlength}{111.70488613bp}%
-    \ifx\svgscale\undefined%
-      \relax%
-    \else%
-      \setlength{\unitlength}{\unitlength * \real{\svgscale}}%
-    \fi%
-  \else%
-    \setlength{\unitlength}{\svgwidth}%
-  \fi%
-  \global\let\svgwidth\undefined%
-  \global\let\svgscale\undefined%
-  \makeatother%
-  \begin{picture}(1,1.16881925)%
-    \lineheight{1}%
-    \setlength\tabcolsep{0pt}%
-    \put(0,0){\includegraphics[width=\unitlength,page=1]{quark.pdf}}%
-    \put(-0.00743098,0.01862117){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$r,\, g,\, b$\end{tabular}}}}%
-    \put(0.66442584,0.01873966){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$u,\, d$\end{tabular}}}}%
-    \put(0,0){\includegraphics[width=\unitlength,page=2]{quark.pdf}}%
-  \end{picture}%
-\endgroup%
diff --git a/img/radial_ordering.pdf b/img/radial_ordering.pdf
deleted file mode 100644
index cc09512..0000000
Binary files a/img/radial_ordering.pdf and /dev/null differ
diff --git a/img/radial_ordering.pdf_tex b/img/radial_ordering.pdf_tex
deleted file mode 100644
index a92ee58..0000000
--- a/img/radial_ordering.pdf_tex
+++ /dev/null
@@ -1,62 +0,0 @@
-%% Creator: Inkscape 1.0 (4035a4fb49, 2020-05-01), www.inkscape.org
-%% PDF/EPS/PS + LaTeX output extension by Johan Engelen, 2010
-%% Accompanies image file 'radial_ordering.pdf' (pdf, eps, ps)
-%%
-%% To include the image in your LaTeX document, write
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics{<filename>.pdf}
-%% To scale the image, write
-%%   \def\svgwidth{<desired width>}
-%%   \input{<filename>.pdf_tex}
-%%  instead of
-%%   \includegraphics[width=<desired width>]{<filename>.pdf}
-%%
-%% Images with a different path to the parent latex file can
-%% be accessed with the `import' package (which may need to be
-%% installed) using
-%%   \usepackage{import}
-%% in the preamble, and then including the image with
-%%   \import{<path to file>}{<filename>.pdf_tex}
-%% Alternatively, one can specify
-%%   \graphicspath{{<path to file>/}}
-%% 
-%% For more information, please see info/svg-inkscape on CTAN:
-%%   http://tug.ctan.org/tex-archive/info/svg-inkscape
-%%
-\begingroup%
-  \makeatletter%
-  \providecommand\color[2][]{%
-    \errmessage{(Inkscape) Color is used for the text in Inkscape, but the package 'color.sty' is not loaded}%
-    \renewcommand\color[2][]{}%
-  }%
-  \providecommand\transparent[1]{%
-    \errmessage{(Inkscape) Transparency is used (non-zero) for the text in Inkscape, but the package 'transparent.sty' is not loaded}%
-    \renewcommand\transparent[1]{}%
-  }%
-  \providecommand\rotatebox[2]{#2}%
-  \newcommand*\fsize{\dimexpr\f@size pt\relax}%
-  \newcommand*\lineheight[1]{\fontsize{\fsize}{#1\fsize}\selectfont}%
-  \ifx\svgwidth\undefined%
-    \setlength{\unitlength}{220.75220544bp}%
-    \ifx\svgscale\undefined%
-      \relax%
-    \else%
-      \setlength{\unitlength}{\unitlength * \real{\svgscale}}%
-    \fi%
-  \else%
-    \setlength{\unitlength}{\svgwidth}%
-  \fi%
-  \global\let\svgwidth\undefined%
-  \global\let\svgscale\undefined%
-  \makeatother%
-  \begin{picture}(1,0.88543026)%
-    \lineheight{1}%
-    \setlength\tabcolsep{0pt}%
-    \put(0,0){\includegraphics[width=\unitlength,page=1]{radial_ordering.pdf}}%
-    \put(0.28214993,0.64314169){\color[rgb]{0,0,0}\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$w$\end{tabular}}}}%
-    \put(0.83536879,0.37349547){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\Re z$\end{tabular}}}}%
-    \put(0.43673387,0.85101321){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\Im z$\end{tabular}}}}%
-    \put(0.24816849,0.48333669){\makebox(0,0)[lt]{\lineheight{1.25}\smash{\begin{tabular}[t]{l}$\ccC_{w}$\end{tabular}}}}%
-  \end{picture}%
-\endgroup%
diff --git a/sec/part1/dbranes.tex b/sec/part1/dbranes.tex
index 7358d8f..4a2c006 100644
--- a/sec/part1/dbranes.tex
+++ b/sec/part1/dbranes.tex
@@ -81,15 +81,13 @@ We thus choose $X_{(t)}^1$ and $X_{(t)}^2$ to be the coordinates parallel to the
   \centering
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{branesangles.pdf_tex}
+    \import{tikz}{branesangles.pgf}
     \caption{D-branes as lines on $\R^2$.}
   \end{subfigure}
   \hfill
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{welladapted.pdf_tex}
+    \import{tikz}{welladapted.pgf}
     \caption{Well adapted system of coordinates.}
   \end{subfigure}
   \caption{%
diff --git a/sec/part1/introduction.tex b/sec/part1/introduction.tex
index 314ab72..c1e912b 100644
--- a/sec/part1/introduction.tex
+++ b/sec/part1/introduction.tex
@@ -233,15 +233,13 @@ In fact a transformation $\xi \mapsto \chi(\xi)$ and $\bxi \mapsto \bchi(\bxi)$
   \centering
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{complex_plane.pdf_tex}
+    \import{tikz}{complex_plane.pgf}
     \caption{Radial ordering.}
   \end{subfigure}
   \hfill
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{radial_ordering.pdf_tex}
+    \import{tikz}{radial_ordering.pgf}
     \caption{Difference of time ordered contours.}
   \end{subfigure}
   \caption{Map to the complex plane.}
@@ -1284,16 +1282,14 @@ The field $\cA^a$ forms a vector representation of the group \SO{D-1-p} and from
   \centering
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{0.8\linewidth}
-    \import{img}{chanpaton.pdf_tex}
+    \import{tikz}{chanpaton.pgf}
     \caption{Chan-Paton factors labelling strings.}
   \end{subfigure}
   \hfill
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{0.7\linewidth}
-    \import{img}{quark.pdf_tex}
-    \caption{Naive model of a left handed massive quark.}
+    \import{tikz}{quark.pgf}
+    \caption{Naive model of left handed massive quarks.}
   \end{subfigure}
   \caption{Strings attached to different D-branes.}
   \label{fig:dbranes:chanpaton}
@@ -1346,8 +1342,7 @@ The light spectrum is thus composed of the desired matter content alongside with
 
 \begin{figure}[tbp]
   \centering
-  \def\svgwidth{0.7\linewidth}
-  \import{img}{smbranes.pdf_tex}
+  \import{tikz}{smbranes.pgf}
   \caption{%
     Example of \sm-like construction using intersecting D-branes with the indications of the hypercharge $Y$.
     Perpendicular angles are only a matter of convenience: they are in principal arbitrary.
diff --git a/thesis.cls b/thesis.cls
index 6092299..662a0b4 100644
--- a/thesis.cls
+++ b/thesis.cls
@@ -37,6 +37,8 @@
 \RequirePackage{changepage} %------------------- change page layout
 \RequirePackage{lastpage} %--------------------- reference to last page
 \RequirePackage{tocloft} %---------------------- modify table of contents
+\RequirePackage{tikz} %------------------------- TikZ pictures
+\RequirePackage{pgf} %-------------------------- pgf plots
 \RequirePackage[type={CC},
                 modifier={by-nc-nd},
                 version={4.0}]{doclicense} %---- licence
diff --git a/tikz/branesangles.pgf b/tikz/branesangles.pgf
new file mode 100644
index 0000000..7429bed
--- /dev/null
+++ b/tikz/branesangles.pgf
@@ -0,0 +1,35 @@
+\begin{tikzpicture}
+
+% draw axis
+\draw[thick, ->] (-3cm, 0cm) -- (3cm, 0cm) node[anchor=south] {$X^1$};
+\draw[thick, ->] (0cm, -3cm) -- (0cm, 3cm) node[anchor=east] {$X^2$};
+
+% draw the D-branes
+\draw[dash pattern=on 5pt off 2pt on 5pt off 2pt on 4cm off 2pt] (-2.5cm, -1cm) -- (2.75cm, -2.15cm);
+\draw[dash pattern=on 5pt off 2pt on 5pt off 2pt on 5pt off 2pt on 5pt off 2pt on 4.5cm off 2pt] (-2.5cm, -2cm) -- (1cm, 2.75cm);
+\draw[dash pattern=on 5pt off 2pt on 5pt off 2pt on 4.5cm off 2pt] (0.6cm, 2.9cm) -- (2cm, -2.75cm);
+
+% give the D-branes names
+\node[anchor=base] (D1) at (-0.75cm, -2.25cm) {$D_{(1)}$};
+\node[anchor=base] (D2) at (-1.25cm, 1cm) {$D_{(2)}$};
+\node[anchor=base] (D3) at (1.7cm, 0.8cm) {$D_{(3)}$};
+
+% draw the distance of each side from the center
+\draw[thin] (0cm, 0cm) -- (-0.3cm, -1.47cm) node[anchor=north] {$g_{(1)}$};
+\draw[thin] (0cm, 0cm) -- (-0.7cm, 0.45cm) node[anchor=east] {$g_{(2)}$};
+\draw[thin] (0cm, 0cm) -- (1.27cm, 0.22cm) node[anchor=west] {$g_{(3)}$};
+
+% prolong the end points
+\draw[dotted] (1.3cm, -1.925cm) node[anchor=north] {$f_{(1)}$} -- (3cm, -1.925cm);
+\draw[dotted] (0.3cm, 2.4cm) -- (2cm, 2.4cm) node[anchor=north east] {$f_{(2)}$};
+\draw[dotted] (-2.3cm, -1.14cm) node[anchor=north east] {$f_{(3)}$} -- (-0.6cm, -1.14cm);
+
+% draw the arcs for the angles
+
+\draw[thin, <-] (2.6cm, -2.12cm) arc (0:30:0.4cm) node[anchor=south] {$\pi \alpha_{(1)}$};
+\draw[thin, <-] (-2.1cm, -1.5cm) arc (250:360:0.4cm) node[anchor=south west] {$\pi \alpha_{(2)}$};
+\draw[thin, <-] (1.1cm, 2.4cm) arc (0:100:0.4cm) node[anchor=south] {$\pi \alpha_{(3)}$};
+
+\end{tikzpicture}
+
+% vim: ft=tex
\ No newline at end of file
diff --git a/tikz/chanpaton.pgf b/tikz/chanpaton.pgf
new file mode 100644
index 0000000..8fe719c
--- /dev/null
+++ b/tikz/chanpaton.pgf
@@ -0,0 +1,27 @@
+\usetikzlibrary{decorations.markings}
+\usetikzlibrary{decorations.pathmorphing}
+\usetikzlibrary{arrows}
+
+\begin{tikzpicture}
+
+% draw the D-branes
+\draw[thick] (0cm, 0cm) -- (1cm, 0.5cm) -- (1cm, 4cm) -- (0cm, 3.5cm) -- cycle;
+\draw[thick] (2.5cm, 0cm) -- (3.5cm, 0.5cm) -- (3.5cm, 4cm) -- (2.5cm, 3.5cm) -- cycle;
+\draw[thick] (5cm, 0cm) -- (6cm, 0.5cm) -- (6cm, 4cm) -- (5cm, 3.5cm) -- cycle;
+
+% draw strings
+\draw[decorate, decoration={snake, segment length=1cm}, dash pattern=on 2.45cm off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt, postaction={decoration={markings, mark=at position 0.5 with {\arrow{>}}}, decorate}] (0.5cm, 3cm) -- (3cm, 1.5cm);
+\node[anchor=base] (l1) at (1.75cm, 2.75cm) {$\tensor{\lambda}{^1_1_2}$};
+
+\draw[decorate, decoration={snake, segment length=1cm}, dash pattern=on 2.45cm off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt, postaction={decoration={markings, mark=at position 0.5 with {\arrow{>}}}, decorate}] (3cm, 3cm) -- (5.5cm, 1.5cm);
+\node[anchor=base] (l2) at (4.25cm, 2.75cm) {$\tensor{\lambda}{^2_2_3}$};
+
+\draw[decorate, decoration={snake, segment length=1cm}, postaction={decoration={markings, mark=at position 0.765 with {\arrow{>}}}, decorate}] (3cm, 2.5cm) .. controls (3.5cm, 2cm) and (3.5cm, 1cm) .. (3cm, 0.5cm);
+\node[anchor=base] (l3) at (4cm, 1.5cm) {$\tensor{\lambda}{^3_2_2}$};
+
+\draw[decorate, decoration={snake, segment length=1cm}, dash pattern=on 5.15cm off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt, postaction={decoration={markings, mark=at position 0.5 with {\arrow{<}}}, decorate}] (0.5cm, 1cm) .. controls (1.5cm, 0cm) and (4cm, 0cm) .. (5.5cm, 1cm);
+\node[anchor=base] (l4) at (3cm, -0.5cm) {$\tensor{\lambda}{^4_3_1}$};
+
+\end{tikzpicture}
+
+% vim: ft=tex
diff --git a/tikz/complex_plane.pgf b/tikz/complex_plane.pgf
new file mode 100644
index 0000000..1514022
--- /dev/null
+++ b/tikz/complex_plane.pgf
@@ -0,0 +1,28 @@
+\usetikzlibrary{decorations.markings}
+\usetikzlibrary{arrows}
+
+\begin{tikzpicture}
+
+% draw axis
+\draw[thick, ->] (-3cm, 0cm) -- (3cm, 0cm) node[anchor=south] {$\Re z$};
+\draw[thick, ->] (0cm, -3cm) -- (0cm, 3cm) node[anchor=east] {$\Im z$};
+
+% draw closed loops
+\draw[dotted, decorate, decoration={markings, mark=at position 0.0 with {\arrow{latex}}}] (0cm, 0cm) circle [radius=1.0cm];
+\draw[dotted, decorate, decoration={markings, mark=at position 0.0 with {\arrow{latex}}}] (0cm, 0cm) circle [radius=2.5cm];
+
+% draw arrows
+\draw[-latex] (0,0) -- (1.75cm, 1.75cm) node[anchor=south west] (z1) {$\abs{z_{(1)}} = e^{\tau_{E\, (1)}}$};
+\draw[-latex] (0,0) -- (0.45cm, -0.9cm) node[anchor=north west] (z0) {$\abs{z_{(0)}} = e^{\tau_{E\, (0)}}$};
+
+% draw isolated point
+\draw[fill] (-1.5cm, 1.1cm) circle [radius=2pt] node[anchor=south west] (w) {$w$};
+
+% draw the names of the paths (use $\mathcal{C}$ instead of $\ccC$ if it does not compile)
+\node (c0) at (-0.7cm, -1.2cm) {$\ccC_{(0)}$};
+\node (c0) at (-1.5cm, -2.6cm) {$\ccC_{(1)}$};
+
+\end{tikzpicture}
+
+
+% vim: ft=tex
diff --git a/tikz/quark.pgf b/tikz/quark.pgf
new file mode 100644
index 0000000..1500be2
--- /dev/null
+++ b/tikz/quark.pgf
@@ -0,0 +1,21 @@
+\usetikzlibrary{decorations.markings}
+\usetikzlibrary{decorations.pathmorphing}
+\usetikzlibrary{arrows}
+
+\begin{tikzpicture}
+
+% draw the D-branes
+\draw[thick] (0cm, 0cm) node[anchor=north] (r) {$r$} -- (1cm, 0.5cm) -- (1cm, 4cm) -- (0cm, 3.5cm) -- cycle;
+\draw[thick] (0.3cm, 0cm) node[anchor=north] (g) {$g$} -- (1.3cm, 0.5cm) -- (1.3cm, 4cm) -- (0.3cm, 3.5cm) -- cycle;
+\draw[thick] (0.6cm, 0cm) node[anchor=north] (b) {$b$} -- (1.6cm, 0.5cm) -- (1.6cm, 4cm) -- (0.6cm, 3.5cm) -- cycle;
+
+\draw[thick] (4cm, 0cm) node[anchor=north] (u) {$u$} -- (5cm, 0.5cm) -- (5cm, 4cm) -- (4cm, 3.5cm) -- cycle;
+\draw[thick] (4.3cm, 0cm) node[anchor=north] (d) {$d$} -- (5.3cm, 0.5cm) -- (5.3cm, 4cm) -- (4.3cm, 3.5cm) -- cycle;
+
+% draw the strings
+\draw[decorate, decoration={snake, segment length=1cm}, dash pattern=on 3.35cm off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt, postaction={decoration={markings, mark=at position 0.5 with {\arrow{>}}}, decorate}] (0.85cm, 2.5cm) -- (4.25cm, 2.5cm);
+\draw[decorate, decoration={snake, segment length=1cm}, dash pattern=on 3.35cm off 1pt on 1pt off 1pt on 1pt off 1pt on 1pt off 1pt, postaction={decoration={markings, mark=at position 0.5 with {\arrow{<}}}, decorate}] (0.85cm, 1.5cm) -- (4.25cm, 1.5cm);
+
+\end{tikzpicture}
+
+% vim: ft=tex
diff --git a/tikz/radial_ordering.pgf b/tikz/radial_ordering.pgf
new file mode 100644
index 0000000..98a1dbb
--- /dev/null
+++ b/tikz/radial_ordering.pgf
@@ -0,0 +1,22 @@
+\usetikzlibrary{decorations.markings}
+\usetikzlibrary{arrows}
+
+\begin{tikzpicture}
+
+% draw axis
+\draw[thick, ->] (-3cm, 0cm) -- (3cm, 0cm) node[anchor=south] (ascissa) {$\Re z$};
+\draw[thick, ->] (0cm, -3cm) -- (0cm, 3cm) node[anchor=east] (ordinata) {$\Im z$};
+
+% draw isolated point
+\draw[fill] (-1.5cm, 1.1cm) circle [radius=2pt] node[anchor=south west] (w) {$w$};
+
+% draw closed loops
+\draw[dotted, decorate, decoration={markings, mark=at position 0.0 with {\arrow{latex}}}] (-1.5cm, 1.1cm) circle [radius=0.6cm];
+
+% draw the names of the paths (use $\mathcal{C}$ instead of $\ccC$ if it does not compile)
+\node (c0) at (-2.1cm, 0.3cm) {$\ccC_{(w)}$};
+
+\end{tikzpicture}
+
+
+% vim: ft=tex
diff --git a/tikz/smbranes.pgf b/tikz/smbranes.pgf
new file mode 100644
index 0000000..6cd9153
--- /dev/null
+++ b/tikz/smbranes.pgf
@@ -0,0 +1,35 @@
+\usetikzlibrary{decorations.markings}
+\usetikzlibrary{decorations.pathmorphing}
+\usetikzlibrary{arrows}
+
+\begin{tikzpicture}
+
+% draw the baryonic stack
+\draw[thick] (-2.5cm, 5cm) -- (2.5cm, 5cm);
+\draw[thick] (-2.5cm, 4.9cm) -- (2.5cm, 4.9cm) node[anchor=west] (baryonic) {baryonic $\qty(Y = \frac{1}{3} )$};
+\draw[thick] (-2.5cm, 4.8cm) -- (2.5cm, 4.8cm);
+
+% draw the left stack
+\draw[thick] (-2.25cm, 5.25cm) -- (-2.25cm, 0cm);
+\draw[thick] (-2.15cm, 5.25cm) -- (-2.15cm, 0cm) node[anchor=north east] (left) {left $\qty( Y = - \frac{1}{2} )$};
+
+% draw leptonic and right stacks
+\draw[thick] (-2.5cm, 2.5cm) -- (2.5cm, 2.5cm) node[anchor=west] (l1) {leptonic $\qty( Y = 0 )$};
+\draw[thick] (-2.5cm, 0.5cm) -- (2.5cm, 0.5cm) node[anchor=west] (l2) {leptonic $\qty( Y = -1 )$};
+\draw[thick] (0cm, 5.25cm) -- (0cm, 0cm) node[anchor=north] (r1) {right $\qty( Y = -1 )$};
+\draw[thick] (2.25cm, 5.25cm) -- (2.25cm, 0cm) node[anchor=north west] (r2) {right $\qty( Y = 0 )$};
+
+% draw left quarks
+\draw[decorate, decoration={snake, segment length=0.5cm}, postaction={decoration={markings, mark=at position 0.5 with {\arrow{>}}}, decorate}] (-2.15cm, 3.5cm) node[anchor=south east] {$\mqty( u_L \\ d_L )$} -- (-1cm, 4.8cm);
+% draw up right quark
+\draw[decorate, decoration={snake, segment length=0.5cm}, postaction={decoration={markings, mark=at position 0.5 with {\arrow{<}}}, decorate}] (0cm, 3.5cm) node[anchor=east] {$\baru_R$} -- (1cm, 4.8cm);
+% draw down right quark
+\draw[decorate, decoration={snake, segment length=0.5cm}, postaction={decoration={markings, mark=at position 0.5 with {\arrow{<}}}, decorate}] (2.25cm, 3.5cm) node[anchor=west] {$\bard_R$} -- (1.15cm, 4.8cm);
+% draw left leptons
+\draw[decorate, decoration={snake, segment length=0.5cm}, postaction={decoration={markings, mark=at position 0.5 with {\arrow{>}}}, decorate}] (-2.15cm, 0.9cm) node[anchor=south east] {$\mqty( \nu^e_L \\ e^-_L )$} -- (-1cm, 2.5cm);
+% draw right leptons
+\draw[decorate, decoration={snake, segment length=0.5cm}, postaction={decoration={markings, mark=at position 0.5 with {\arrow{<}}}, decorate}] (0cm, 0.9cm) node[anchor=east] {$\bare^+_R$} -- (1cm, 2.5cm);
+
+\end{tikzpicture}
+
+% vim: ft=tex
diff --git a/tikz/welladapted.pgf b/tikz/welladapted.pgf
new file mode 100644
index 0000000..d48fdf3
--- /dev/null
+++ b/tikz/welladapted.pgf
@@ -0,0 +1,13 @@
+\begin{tikzpicture}
+
+% draw the D-brane
+\draw (0cm, 0cm) -- (5cm, -1cm) -- (6cm, 3cm) -- (1.5cm, 4cm) node[anchor=south west] {$D_{(t)}$} -- cycle;
+
+% draw a triad of axis
+\draw[thick, ->] (3cm, 1cm) -- (2.7cm, 0.1cm) node[anchor=east] {$X^1_{(t)}$};
+\draw[thick, ->] (3cm, 1cm) -- (5cm, 0.6cm) node[anchor=south] {$X^2_{(t)}$};
+\draw[thick, ->] (3cm, 1cm) -- (3cm, 2.75cm) node[anchor=east] {$X^3_{(t)}$};
+
+\end{tikzpicture}
+
+% vim: ft=tex
\ No newline at end of file