26,422 research outputs found
The non-perturbative renormalization group in the ordered phase
We study some analytical properties of the solutions of the non perturbative
renormalization group flow equations for a scalar field theory with
symmetry in the ordered phase, i.e. at temperatures below the critical
temperature. The study is made in the framework of the local potential
approximation. We show that the required physical discontinuity of the magnetic
susceptibility at ( spontaneous magnetization) is
reproduced only if the cut-off function which separates high and low energy
modes satisfies to some restrictive explicit mathematical conditions; we stress
that these conditions are not satisfied by a sharp cut-off in dimensions of
space .Comment: 27 pages, 14 figures, 7 table
Extrapolation of lattice QCD results beyond the power-counting regime
Resummation of the chiral expansion is necessary to make accurate contact
with current lattice simulation results of full QCD. Resummation techniques
including relativistic formulations of chiral effective field theory and
finite-range regularization (FRR) techniques are reviewed, with an emphasis on
using lattice simulation results to constrain the parameters of the chiral
expansion. We illustrate how the chiral extrapolation problem has been solved
and use FRR techniques to identify the power-counting regime (PCR) of chiral
perturbation theory. To fourth-order in the expansion at the 1% tolerance
level, we find 0 \le m_pi \le 0.18 GeV for the PCR, extending only a small
distance beyond the physical pion mass.Comment: 12 pages, 5 figures, plenary talk at BARYONS 2004, Paris, Oct. 25-2
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