Speaker
Description
In O(N) models, the multi-cluster algorithm generates spins
clusters, which are usually considered as purely algorithmic
objects. We show that the histograms of their sizes scale
towards a continuum limit, with a fractal dimension D, which
suggests that these clusters do have a physical meaning.
We demonstrate this property for the quantum rotor in separate
topological sectors (where D=1), for the 2d XY model in the
massive and in the massless phase (where D<2, and where we
also define a cluster vorticity), and in the 3d O(4) model
(where we relate D to the critical exponents).
The latter represents an effective theory for 2-flavor
QCD in the chiral limit, at high temperature, where the
topological charge corresponds to the baryon number.
For a suitable lattice actions, it can be traced back to
the topological charge assigned to the clusters.
Clusters are therefore the physical carriers of topology
and vorticity, beyond semi-classical approximations.
