The Standard Model: Interactions (Bosons)

All interactions (forces) in nature are mediated by gauge fields. The electromagnetic, weak and nuclear forces are described by quantum fields. A quantum theory of gravity is provided by string theory, which also explains the appearance of gauge fields from deeper principles.

The Forces of Nature

Electromagnetic

Electrons are bound to the nucleus via photons (light) which are the carriers of the electromagnetic interaction. The photon is the expression of the local electromagnetic potential A_µ (x), called a U(1) gauge field & has spin 1.

Weak Interaction

The neutron outside the nucleus is unstable and disintegrates after about 15 minutes via the weak force.

n (udd) -> p (uud) + e + V_e

or in terms of quarks, we have the following

d -> u + e + V_e

The weak force is mediated by the combination of three local gauge fields Z⁰_µ, W^±_µ also called SU (2) gauge fields and maybe a spin 0 Higgs field.

Nuclear or Strong Force

The quarks are bound together inside the nucleus by the nuclear force which is mediated by eight local gluon fields B¹_µ, B²_µ, ... B⁸_µ and taken together form an SU (3) gauge field with spin 1.

Gravity

All forms of energy attract each other via gravity, that is mediated by the graviton which is a spin 2 particle and results from the metric g_µv.

Other as yet undiscovered forces ("Fifth force" etc.)

All the Known Interactions

Picture showing the constituents of matter

Picture showing the different generations

Last updated: 13 June, 2005

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