Singular Behaviour of the Potts Model in the Thermodynamic Limit

The self-duality transformation is applied to the Fisher zeroes near the critical point in the thermodynamic limit in the q>4 state Potts model in two dimensions. A requirement that the locus of the duals of the zeroes be identical to the dual of the locus of zeroes (i) recovers the ratio of specific heat to internal energy discontinuity at criticality and the relationships between the discontinuities of higher cumulants and (ii) identifies duality with complex conjugation. Conjecturing that all zeroes governing ferromagnetic critical behaviour satisfy the latter requirement, the full locus of Fisher zeroes is shown to be a circle. This locus, together with the density of zeroes is shown to be sufficient to recover the singular form of all thermodynamic functions in the thermodynamic limit.Comment: Contribution to Lattice 97, LaTeX, 3 pages, 0 figure

On the algebraic approach to solvable lattice models

We develop an algebraic approach to solvable lattice models based on a chain of algebras obeyed by the models. In each subalgebra we use a unit, giving a chain of ideals. Thus, we divide the models into distinct sectors which do not mix. This method gives the usual Bethe anzats results in cases it is known, but generalizes it to non integrable models. We exemplify the method on the Temperley--Lieb and Fuss--Catalan algebras. For the Fuss--Catalan algebra we show that the ground state energy is zero and there is a mass gap of one for $\alpha>\sqrt2$, and that for $\alpha=1$ we seem to get an RCFT as the scaling limit.Comment: 14 pages, one table. Minor typos correcte

Determinant of the Potts model transfer matrix and the critical point

By using a decomposition of the transfer matrix of the $q$-state Potts Model on a three dimensional $m \times n \times n$ simple cubic lattice its determinant is calculated exactly. By using the calculated determinants a formula is conjectured which approximates the critical temperature for a d-dimensional hypercubic lattice.Comment: 8 page

Fisher Zeroes and Singular Behaviour of the Two Dimensional Potts Model in the Thermodynamic Limit

The duality transformation is applied to the Fisher zeroes near the ferromagnetic critical point in the q>4 state two dimensional Potts model. A requirement that the locus of the duals of the zeroes be identical to the dual of the locus of zeroes in the thermodynamic limit (i) recovers the ratio of specific heat to internal energy discontinuity at criticality and the relationships between the discontinuities of higher cumulants and (ii) identifies duality with complex conjugation. Conjecturing that all zeroes governing ferromagnetic singular behaviour satisfy the latter requirement gives the full locus of such Fisher zeroes to be a circle. This locus, together with the density of zeroes is then shown to be sufficient to recover the singular form of the thermodynamic functions in the thermodynamic limit.Comment: 10 pages, 0 figures, LaTeX. Paper expanded and 2 references added clarifying duality relationships between discontinuities in higher cumulant

The antiferromagnetic transition for the square-lattice Potts model

We solve the antiferromagnetic transition for the Q-state Potts model (defined geometrically for Q generic) on the square lattice. The solution is based on a detailed analysis of the Bethe ansatz equations (which involve staggered source terms) and on extensive numerical diagonalization of transfer matrices. It involves subtle distinctions between the loop/cluster version of the model, and the associated RSOS and (twisted) vertex models. The latter's continuum limit involves two bosons, one which is compact and twisted, and the other which is not, with a total central charge c=2-6/t, for sqrt(Q)=2cos(pi/t). The non-compact boson contributes a continuum component to the spectrum of critical exponents. For Q generic, these properties are shared by the Potts model. For Q a Beraha number [Q = 4 cos^2(pi/n) with n integer] the two-boson theory is truncated and becomes essentially Z\_{n-2} parafermions. Moreover, the vertex model, and, for Q generic, the Potts model, exhibit a first-order critical point on the transition line, i.e., the critical point is also the locus of level crossings where the derivatives of the free energy are discontinuous. In that sense, the thermal exponent of the Potts model is generically nu=1/2. Things are profoundly different for Q a Beraha number, where the transition is second order, with nu=(t-2)/2 determined by the psi\_1 parafermion. As one enters the adjacant Berker-Kadanoff phase, the model flows, for t odd, to a minimal model of CFT with c=1-6/t(t-1), while for t even it becomes massive. This provides a physical realization of a flow conjectured by Fateev and Zamolodchikov in the context of Z\_N integrable perturbations. Finally, we argue that the antiferromagnetic transition occurs as well on other two-dimensional lattices

Chromatic Polynomials for J(∏H)IJ(\prod H)I Strip Graphs and their Asymptotic Limits

We calculate the chromatic polynomials $P$ for $n$-vertex strip graphs of the form $J(\prod_{\ell=1}^m H)I$, where $J$ and $I$ are various subgraphs on the left and right ends of the strip, whose bulk is comprised of $m$-fold repetitions of a subgraph $H$. The strips have free boundary conditions in the longitudinal direction and free or periodic boundary conditions in the transverse direction. This extends our earlier calculations for strip graphs of the form $(\prod_{\ell=1}^m H)I$. We use a generating function method. From these results we compute the asymptotic limiting function $W=\lim_{n \to \infty}P^{1/n}$; for $q \in {\mathbb Z}_+$ this has physical significance as the ground state degeneracy per site (exponent of the ground state entropy) of the $q$-state Potts antiferromagnet on the given strip. In the complex $q$ plane, $W$ is an analytic function except on a certain continuous locus ${\cal B}$. In contrast to the $(\prod_{\ell=1}^m H)I$ strip graphs, where ${\cal B}$ (i) is independent of $I$, and (ii) consists of arcs and possible line segments that do not enclose any regions in the $q$ plane, we find that for some $J(\prod_{\ell=1}^m H)I$ strip graphs, ${\cal B}$ (i) does depend on $I$ and $J$, and (ii) can enclose regions in the $q$ plane. Our study elucidates the effects of different end subgraphs $I$ and $J$ and of boundary conditions on the infinite-length limit of the strip graphs.Comment: 33 pages, Latex, 7 encapsulated postscript figures, Physica A, in press, with some typos fixe

Dynamics of parental work hours, job insecurity, and child wellbeing during middle childhood in Australian dual-income families

This study examines the relationship between parental employment characteristics and child well-being during middle childhood in Australian dual-earner families. Parental employment provides important resources for children’s wellbeing, but may also be associated with variations in parental time availability, parental stress levels and wellbeing, differences in parenting styles and variations in household dynamics. Further, there may be gender differences in how mothers’ and fathers’ employment characteristics relate to child wellbeing, as well as variations by age. Our study contributes to existing research by 1) examining longitudinal data that enables us to examine changes in the association between parental work hours, job insecurity and child wellbeing, within and across parent-child relationships; 2) focusing on dual-employed households to examine the effects of mothers’ and fathers’ employment characteristics on girls’ and boys’ wellbeing; and 3) testing possible mediators in the relationship between parental employment characteristics and child well-being. Drawing on 3 waves of data from two cohorts of the Longitudinal Study of Australian Children (N = 3,216), from 2004 to 2012, we find that mothers who work long hours on average over the study period have children with poorer socio emotional development, while fathers with increasing work hours have children with poorer socio-emotional development. Mothers’ job security is associated with better child development comparing both across mothers and within mothers over time. We find little evidence that these associations are mediated by parenting style or work-family balance, suggesting further research is needed to understand the mechanisms linking parental employment with children’s outcomes