# Weak interaction - is it a force?

• I

A friend, well-read in popular accounts of physics, posted the following question to me: is the weak force attractive or repulsive?

Now I have read about the weak interaction. I know that it violates parity, that it is involved in beta decay, that it unifies with the electromagnetic interaction at higher energies, etc.

But I could not answer my friend's question except to suggest that the weak interaction is not really a force, except insofar as it makes things happen (and so could perhaps be regarded as a force).

## Answers and Replies

The weak interaction is definitely not a force in the sense of a force being a push or a pull on an object. However a push or a pull is a subset of a more general set of 'interactions' that include all the things the four fundamental forces are capable of. So a force could be considered to be a specific type of interaction and it is probably more accurate to call the fundamental forces fundamental interactions instead.

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Weak interaction has some similarities with electromagnetic (EM) interaction. For the latter, the force is attractive/repulsive between electric charges of the opposite/same sign. In the case of weak interaction we have weak charges, so one may expect a similar answer. It is more complicated due to the self-interaction term of the weak gauge fields, but in principle the question is well posed and can be answered. For that purpose, one has to solve the classical field equations of weak gauge fields, in which the charged weak current is modeled by a classical pointlike particle.

Is weak interaction generally repulsive/attractive, or by specific cases?

For example, neutrinos can undergo elastic scattering off particles capable of weak interactions, such as leptons or nucleons, even when they do not meet thresholds for any reactions. But do neutrinos possess, and confer on the particles they weakly and elastically interact with, any term of potential energy?

The weak interaction is definitely not a force in the sense of a force being a push or a pull on an object. However a push or a pull is a subset of a more general set of 'interactions' that include all the things the four fundamental forces are capable of. So a force could be considered to be a specific type of interaction and it is probably more accurate to call the fundamental forces fundamental interactions instead.

If one could characterise the weak interaction then, how could it be described? If not pull or push, what is it exactly in lay terms?

IH

If one could characterise the weak interaction then, how could it be described? If not pull or push, what is it exactly in lay terms?

I'm sorry, but I don't know enough about how the weak force works to describe it in any accurate way. Perhaps @Demystifier can help you.

Maybe this is just a matter of semantics?

Perhaps what is meant uniquely by the term ‘weak interaction’ is collectively (per Wiki):

An interaction that changes the favour of quarks; and
Violates both P and CP parity symmetry; and
Is mediated by massive bosons.

In a semantic and lexical context, it would not be a simple interaction but a composite one. Maybe the definition of the weak interaction is not about forces and scattering but about the how of the interaction and the interaction end-products instead, in that sense this would also be an additional point of uniqueness, of definition.

Does this make sense or is there a simpler definition?

IH

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Does this make sense or is there a simpler definition?

That's makes sense to me.