http://link.springer.com/content/pdf/10.1007%2FJHEP04%282011%29029.pdf
Perhaps the best known example is the elasticity of a polymer. A single polymer
molecule can be modeled by joining together many monomers of xed length, where each
monomer can freely rotate around the points of attachment and direct itself in any spatial
direction. Each of these con gurations has the same energy. When the polymer molecule
is immersed into a heat bath, it likes to put itself into a randomly coiled con guration
since these are entropically favored. There are many more such con gurations when the
molecule is short compared to when it is stretched into an extended con guration. The
statistical tendency to return to a maximal entropy state translates into a macroscopic
force, in this case the elastic force.
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