Should the electric force and the strong force be equal for a nuclei to be stable? Because if perhaps, the strong force is now more than that of the electric force, then shouldn't the nucleus collapse due to the constant interaction of the particles in the nucleus?

Let's take a look at the Feynman propagator for a massive scalar field: $$D_F(x-y)=\int\frac{dp^3}{(2\pi)^3}\int\frac{dp^0}{2\pi}\frac{ie^{-ip \cdot (x-y)}}{p^2-m^2}$$ We can use this as the Green's function for a function $u(x)$ with a corresponding $f(y)$: $$u(x)=\int f(y)G(x-y)dy$$ My question...

Our primary objective in thermodynamics is to explain the bulk behavior of matter. In trying to do so we may think of going with the straightforward approach of explaining the bulk behavior by explaining the behavior of its constituents. This would require us to find the positions and velocities ...

I am confused from the equation 6, why we get Euler-Lagrange equation from equation 8 but not from equation 6? Why we need to use $\zeta$ as invariant parameter in equation 8 even we already have invariant parameter $s$ in equation 6, in order to get relativistic euler-lagrange equation? Refere...