# Pointlike particles and the emergence of classicality

#### DMuitW

I've got some conceptual problems on how to interpret the emergence of a classical world, in which, i can't walk through walls, by what is in quantum mechanics described as dimensionless energy 'particles' who have manifested themselves out of the collapse of the wave function (by whichever process, decoherence, measuring,...)

Can anyone enlighten me on this subject? thanks

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DMuitW said:
I've got some conceptual problems on how to interpret the emergence of a classical world, in which, i can't walk through walls, by what is in quantum mechanics described as dimensionless energy 'particles' who have manifested themselves out of the collapse of the wave function (by whichever process, decoherence, measuring,...)

Can anyone enlighten me on this subject? thanks
The particles have forces acting between them - quite strong forces. When you try to push your hand through the wall you are trying to move these powerful force configurations to a higher energy state. That takes a lot of work!

#### DMuitW

So, actually, mass is just an illusion that we perceive as pointlike charges who interact on their environments through forces?

#### MalleusScientiarum

No, mass is not an illusion. It can be sort of classified as a quantity analogous to charge for gravity, except for the always attractive nature of the gravitational force.

Tunneling is improbable for one electron; in order for you to walk through a wall, you'd need to have every single particle in your body spontaneously tunnel through the wall and return to the original configuration. Although this might happen, the probability of its happening is zero.

Essentially, the classical regime appears because certain states are more probable than others, and when we get into large action (as in the $$\int_{t_0}^t' L(\dot{q}, q, t) dt$$ action) certain paths and actions become more probable. These are the "classical paths" that are returned from quantum mechanics. There's some degree of detail of "deriving" classical mechanics from the path integral formulation of quantum mechanics in any book that discusses path integration.

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