2

I need to draw a path for my final essay. Unfortunately it is not very common and I could not find it in previous questions, but I'm not sufficiently familiar with Tikz to draw it by myself or to modify one of the similar ones.

enter image description here

Can someone please help me? Texts and dashed line are not necessary. Thanks in advance!

2
  • 2
    Welcome to TEXSE, what have you tried so far? – Raaja_is_at_topanswers.xyz Sep 5 '19 at 14:58
  • 1
    Hello and welcome. A question that has 4 answers deserves my vote. Then +1 – AndréC Sep 6 '19 at 4:54
5

This might be useful as a starting point

Left without comments as I'm heading home.

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}

  \draw[->] (-1.5,0) -- ++ (3,0);
  \draw[->] (0,-1.5) -- ++ (0,3);

  \def\StartAng{5}
  \def\DeltaAng{30}
  \coordinate (a) at (\StartAng:1);
  \coordinate (a') at (180-\StartAng-\DeltaAng:1);

  \draw (a) arc [start angle=\StartAng,delta angle=\DeltaAng, radius=1]
  -- (a')
  arc [start angle={180-\StartAng-\DeltaAng}, delta angle=\DeltaAng, radius=1]
  -- cycle;
  ;

  \def\StartAng{50}
  \coordinate (a) at (\StartAng:1);

  \draw (a) arc [start angle=\StartAng,
  end angle = {180-\StartAng}, radius=1]
  -- cycle
  ;

  \def\StartAng{-5}
  \coordinate (a) at (\StartAng:1);

  \draw (a) arc [start angle={\StartAng},
  end angle = {-180-\StartAng}, radius=1]
  -- cycle
  ;


\end{tikzpicture}
\end{document}

enter image description here

3

A bit similar to daleif's answer but with bent arrows.

\documentclass[tikz,border=3mm]{standalone}
\usepackage{amsmath}
\DeclareMathOperator{\im}{Im}
\DeclareMathOperator{\re}{Re}
\usetikzlibrary{arrows.meta,bending,decorations.markings}
\tikzset{% https://tex.stackexchange.com/a/430239
    arc arrow/.style args={%
    to pos #1 with length #2}{
    decoration={
        markings,
         mark=at position 0 with {\pgfextra{%
         \pgfmathsetmacro{\tmpArrowTime}{#2/(\pgfdecoratedpathlength)}
         \xdef\tmpArrowTime{\tmpArrowTime}}},
        mark=at position {#1-\tmpArrowTime} with {\coordinate(@1);},
        mark=at position {#1-2*\tmpArrowTime/3} with {\coordinate(@2);},
        mark=at position {#1-\tmpArrowTime/3} with {\coordinate(@3);},
        mark=at position {#1} with {\coordinate(@4);
        \draw[-{Stealth[length=#2,bend]}]       
        (@1) .. controls (@2) and (@3) .. (@4);},
        },
     postaction=decorate,
     }
}
\begin{document}
\begin{tikzpicture}[thick]
 \draw[-stealth] (0,-2.5) -- (0,2.5);
 \draw[-stealth] (-2.2,0) -- (2.2,0) node[right]{$\im\varepsilon=0$};
 \draw[arc arrow=to pos 0.4 with length 3mm] (50:2) coordinate(aux1) arc(50:130:2) -- cycle;
 \draw[arc arrow=to pos 0.55 with length 3mm] (5:2) arc(5:40:2) coordinate(aux2) -- 
 (140:2) arc(140:175:2) -- cycle;
 \draw[arc arrow=to pos 0.25 with length 3mm] (185:2) arc(185:355:2) --  cycle; 
 \path (aux1) -- (aux2) coordinate[midway] (aux) (aux-|0,0) coordinate(aux0);
 \draw[dashed] (-2,0|-aux) -- (2,0|-aux)
  node[right]{$\im(\varepsilon-\mathrm{i}\omega)=0$};
 \draw plot[only marks,mark=x,mark options={thin,red}] 
  coordinates {(aux0) (0,0)};
\end{tikzpicture}
\end{document}

enter image description here

1

Similar to @Schrödinger's cat answer, but with little bit different code:

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{decorations.markings}

\begin{document}
    \begin{tikzpicture}[
line/.style = {decoration={markings, 
                           mark=at position #1 with 
                            {\arrow[very thick]{>}}},
               postaction={decorate}}
                        ]
\draw[->]   (-3,0) -- (3,0) node[right] {$\mathrm{Im}\,\epsilon = 0$};
\draw[->]   (0,-3) -- (0,3);
\fill[red]  (0,0) circle[radius=2pt];
%
\draw[line=0.45]
    ( 30:2.4) arc (30:150:2.4) -- cycle;
\draw[line=0.04]
    (155:2.4) arc (155:175:2.4) -- (5:2.4) arc ( 5:25:2.4) -- cycle;
\draw[line=0.18]
    (185:2.4) arc (185:355:2.4) -- cycle;
\coordinate (aux) at (152.25:2.4);
\draw[dashed] (-3,0 |- aux) -- ++ (6,0) 
                            node[right] {$\mathrm{Im}(\epsilon-\mathrm{i}\omega) = 0$};
\fill[red]  (aux -| 0,0) circle[radius=2pt];
\end{tikzpicture}
\end{document}

enter image description here

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