A field theoretic model derived from a lattice spin model is studied within the framework of the renormalisation group. To second order in epsilon =4-d, where d is the dimensionality of the lattice, the non-universal fixed point and the amplitude of the leading correction to scaling for the susceptibility are determined for two types of lattice. The functional form obtained for the amplitude compares qualitatively well with high-temperature series work; in particular, it gives a prediction for the amplitude of corrections to scaling for the spin- 1 / 2 Ising model on a body centred cubic lattice in three dimensions that is in fair numerical agreement with high temperature series estimates.
Correction-to-scaling amplitudes are calculated to second order in $\ensuremath{\epsilon}=4\ensuremath{-}d$ by renormalized perturbation theory. It is shown that ratio of any two such amplitudes is universal, and that thermodynamic scaling laws among effective exponents break down beyond zeroth order in $\ensuremath{\epsilon}$. Values found are $\frac{{{a}_{\ensuremath{\xi}}}^{+}}{{{a}_{\ensuremath{\chi}}}^{+}}=0.65 (n=1, d=3) \mathrm{and} 0.63 (n=2, d=3)$ in good agreement with high-temperature series, and $\frac{{{a}_{m}}^{\ensuremath{-}}}{{{a}_{\ensuremath{\chi}}}^{+}}=0.85 (n=1, d=3)$.
We report a detailed study of twelve-term, high-temperature series for the second moment of spin-pair correlations ${\ensuremath{\mu}}_{2}(t)$ and the specific heat
cH(t) of the nearest-neighbor spin-
s Ising model in zero magnetic field on the fcc lattice. Near criticality we find ${\ensuremath{\mu}}_{2}(t)={A}_{2}(s)t{(s)}^{\ensuremath{-}(\ensuremath{\gamma}+2\ensuremath{\nu})}[1 + {B}_{2}(s)t{(s)}^{{\ensuremath{\Delta}}_{1}}+ \ensuremath{\cdots}]$, {$t(s)=\frac{[T\ensuremath{-}{T}_{c}(s)]}{T}$}, showing a confluent correction to the dominant scaling singularity. To within uncertainties the exponents have the universal (i.e., spin-independent) values $\ensuremath{\nu}={0.638}_{\ensuremath{-}0.008}^{+0.002}$ (with $\ensuremath{\gamma}={1.250}_{\ensuremath{-}0.007}^{+0.003}$) and ${\ensuremath{\Delta}}_{1}=0.6\ifmmode\pm\else\textpm\fi{}0.1$. The confluent exponent ${\ensuremath{\Delta}}_{1}$ is in reasonable agreement with the correction-to-scaling index derived from earlier analysis of the susceptibility, as predicted by renormalization-group arguments. A similar analysis of the specific heat
cH for the same model finds no detectable confluent singularities in rather noisy, high-temperature series and gives $\ensuremath{\alpha}=0.125\ifmmode\pm\else\textpm\fi{}0.020$ in general confirmation of earlier
s=21 estimates. With $\ensuremath{\nu}$ as quoted above the hyperscaling relation $d\ensuremath{\nu}=2\ensuremath{-}\ensuremath{\alpha}$ at
d=3 requires $\ensuremath{\alpha}={0.086}_{\ensuremath{-}0.006}^{+0.024}$ so the validity of hyperscaling remains problematical.