arivero
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arivero said:y_i^2= 2 \sqrt 2 G_F m_i^2
Hmm how do we put units back in this formula? If G_F is measured in (\hbar c)^3 \over GeV^2 and mass is measured in GeV \over c^2 then the square of yukawa coupling has units, er, \hbar^3 \over c.

Hmm it is already strange here
{G_F \over \sqrt 2} = \frac 18 {g^2 \over M^2_W}
Because in the LHS we have again (hc)^3 / Gev^2
The point of this question is, if we agree that g and y_i are adimensional coupling constants, then we need to add the h and c to restore dimensionality. Furthermore if we postulate that the yukawa coupling of Top is unity, the formula is
1= {c \over \hbar^3} 2 \sqrt 2 G_F m_{top}^2
This is, if we had a theory implying the exact value of y_t=1, this theory give us a formula for the constant \hbar^3 / c. I had expected a formula for \hbar.
Well, at least we can tell that the Area of Planck is
A_P= l_P^2 = {G_N \hbar \over c^3} = {1 \over (\hbar c) ^2} 2 \sqrt 2 G_N G_F m_{top}^2
or, using (\hbar c)=m^2_P G_N
G_N= {2 \sqrt 2 G_F m_{top}^2 \over m_P^4 l_P^2} =<br /> \; 2 \sqrt 2 \; ({ m_{top} \over m_P })^2 { 1 \over m_P^2 \; l_P^2 } G_F
But there should be more fundamental ways of defining the conversion constant (hc) because after all it is the critical value of coulombian dirac equation. This is because classically a coulombian relativistic coupling hc has minimum angular momentum h (when the orbit radius goes to cero and the orbit speed goes to c). In fact, in the formula above, the denominator m^2_X \; l^2_X has the only goal of producing a conversion factor and it works at any scale, not compulsorily the Planck scale. It is more physical perhaps to write
m_P^2 G_N= { 2 \sqrt 2 \over m^2_X \; l^2_X} m_{top}^2 G_F
The funny thing of this formula is that it does not use explicitly h nor c, the necessary combination is hidden in the condition of having m_X and l_X defined at the same scale. As for the powers of m and l, they come from dimensional considerations: Fermi force goes as 1/r^4, gravitation as 1/r^2 so we need a length square. Fermi force does not depend of mass, gravitations depende on product of two masses, so we need a mass square. The only ad-hocness is, as said, to ask the needed mass and the needed length to be defined at the same scale (ie the length must be compton length of the corresponding mass), even if arbitrary; in this way mass and length cancel to produce h/c factors.
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