quantum field theory - Weak force: attractive or repulsive?

We are always told that there are the four fundamental forces or interactions of nature: gravitation, electromagnetism, and the weak and strong forces. We know that gravitation is attractive, that electromagnetism can be attractive or repulsive depending on the electric charge of the interacting particles, and that the strong force is attractive between quarks.

But when the weak force is mentioned, the description is always something such as 'responsible for radioactive decay', but there is no mention of whether this force is attractive or repulsive. So my question is: is the weak force/interaction attractive or repulsive?

Answer

Since the electroweak interaction is mediated by spin 1 bosons, it is the case that "like (charge) repels like and opposites attract".

In the electroweak case, the charges in question are weak isospin and weak hypercharge.

For weak isospin, there are two isospin charges (or flavors), up and down, and their associated anti-charges, anti-up and anti-down.

So:

• up repels up (anti-up repels anti-up)


• down repels down (anti-down repels anti-down)


• up attracts down (anti-up attracts anti-down)


• up attracts anti-up (down attracts anti-down)


• up repels anti-down (down repels anti-up)

For weak hypercharge, there is just one type of charge and its associated anti-charge.

So:

• hypercharge repels hypercharge (anti-hypercharge repels anti-hypercharge)


• hypercharge attracts anti-hypercharge

Note that electric charge is a certain mixture of weak isospin and weak hypercharge.

Since (left-handed) particles carry both weak isospin and weak hypercharge, both must be taken into account to determine which particles attract or repel under the electroweak interaction.