nLab
configuration space

Context

Physics

physics, mathematical physics, philosophy of physics

Surveys, textbooks and lecture notes


theory (physics), model (physics)

experiment, measurement, computable physics

Contents

Idea

The configuration space of a physical system is the space of all possible states of a physical system. For a classical mechanical system with nn-degrees of freedom it is a manifold of dimension nn.

For some purposes, like in relativistic field theory it is convenient to consider not space of states at the point in time, but rather the space of histories or trajectories.

In mathematics, one often talks about the configuration space of NN distinct points in a manifold MM, see Fadell's configuration space.

Idea of histories variant

For a system described by an action functional the configuration space is the domain space of that functional.

More precisely, let H\mathbf{H} be the ambient (∞,1)-topos with a natural numbers object and equipped with a line object 𝔸 1\mathbb{A}^1. Then an action functional is a morphism

exp(iS(−)):C→𝔸 1/ℤ \exp(i S(-)) : C \to \mathbb{A}^1/\mathbb{Z}

in H\mathbf{H}. The configuration space is the domain CC of this functional.

If H\mathbf{H} is a cohesive (∞,1)-topos then there is an intrinsic differential of the action functional to a morphism

dexp(iS(−)):C→♭ dR𝔸 1/ℤ. d \exp(i S(-)) : C \to \mathbf{\flat}_{dR}\mathbb{A}^1/\mathbb{Z} \,.

This is the Euler-Lagrange equation of the system. The homotopy fiber

P→C P \to C

of this morphism is the covariant phase space inside the configuration space: the space of classically realized trajectories/histories of the system.

Revised on October 10, 2011 18:09:32 by Zoran Å koda (161.53.130.104)