Question: Plot the function with the "Error, (in signum) too many levels of recursion"

Hello.

I wrote a simple code for the plot of the function:

restart;
Omega := 2*Pi*N; R0 := a*tanh((a^2-mu)/(2*T_c))*ln((2*a^2+2*a*q+q^2-2*mu-I*Omega)/(2*a^2-2*a*q+q^2-2*mu-I*Omega))/q-2;                      
T_c := 0.169064e-1; mu := .869262; N := 10;
R1 := int(R0, a = 0.1e-3 .. 100);    
R2 := evalf(abs(R1));
plot(R2, q = 0.1e-2 .. 10);

If the parameter N is not equal to zero then after near one hour calculations I got the desired plot. But for N=0 I have an error

Error, (in signum) too many levels of recursion

I searched this error on this site but I can't find anything relevant for this problem.

Thank you in advance for the help.

 

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