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Suppose we have a regionplot as follows:

mpion = 0.137;
meta = 0.548;
metap = 0.958;
con1 = Sqrt[meta^2 + w1^2 + w2^2 - 2  mpion^2 + 2 Sqrt[w1^2 - mpion^2]  Sqrt[w2^2 - mpion^2]];
con2 = Sqrt[meta^2 + w1^2 + w2^2 - 2  mpion^2 -2 Sqrt[w1^2 - mpion^2]  Sqrt[w2^2 -mpion^2]];

RegionPlot[
 Re[con2] < metap - w1 - w2 < Re[con1], {w1, .13, .27}, {w2, .13, .27},  
 BoundaryStyle -> Directive[Red, Thick], FrameLabel -> {"w1", "w2"}, 
 PlotStyle -> None, BaseStyle -> FontSize -> 16]

enter image description here

Which we can plot it in x-y plane (x and y are defined as w1 and w2 functions):

 Q = metap - meta - 2*mpion;
solw = Solve[x == Sqrt[3]/Q*(w1 - w2) && y == -(2 + meta/mpion)/Q*(w1 + w2) - 
      1 +  (2 + meta/mpion)/Q*(metap - meta), {w1, w2}];
w1funxy = w1 /. solw[[1]];
w2funxy = w2 /. solw[[1]];


RegionPlot[(Re[con2] < metap - w1 - w2 < Re[con1]) /. 
   w1 -> w1funxy /. w2 -> w2funxy, {x, -1.4, 1.4}, {y, -1.1, 1.2},  
 BoundaryStyle -> Directive[Blue, Thick], FrameLabel -> {"x", "y"}, 
 BaseStyle -> FontSize -> 16, PlotStyle -> None]

enter image description here

How can I make the boundary of the region in x-y plane smaller? just like this graph (The blue and green boundaries). I need the points in blue and green regions around x=y=0 point. I couldn't change the inequality equation of the region in the way that it gives what I want. enter image description here

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1 Answer 1

up vote 4 down vote accepted

you mean this?

balabala……
Manipulate[
   RegionPlot[Evaluate[(Re[con2] < metap - w1 - w2 < Re[con1]) /. 
   w1 -> w1funxy /. w2 -> w2funxy /. {x -> ratio x, 
    y -> ratio y}], {x, -1.4, 1.4}, {y, -1.1, 1.2}, 
  BoundaryStyle -> Directive[Blue, Thick], FrameLabel -> {"x", "y"}, 
BaseStyle -> FontSize -> 16, PlotStyle -> None], {ratio, 1, 5}]
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Yes, this is exactly what I want. thanks a lot. –  Soodeh Z. Mar 27 at 13:20
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