We present the third data release from the Parkes Pulsar Timing Array (PPTA) project. The release contains observations of 32 pulsars obtained using the 64-m Parkes ‘Murriyang’ radio telescope. The data span is up to 18 yr with a typical cadence of 3 weeks. This data release is formed by combining an updated version of our second data release with $\sim$3 yr of more recent data primarily obtained using an ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. We provide calibrated pulse profiles, flux density dynamic spectra, pulse times of arrival, and initial pulsar timing models. We describe methods for processing such wide-bandwidth observations and compare this data release with our previous release.

New data on leads and surface-melt phenomena in the Arctic, based on mapping of DMSP visible images, are presented. Lead orientations in the Beaufort Sea are broadly correlated with geostrophic wind direction and show similar synoptic scale patterns. Preliminary results of airborne 1.06 μm lidar transects over Baffin Bay demonstrate its great potential for high-resolution mapping of open-water areas and, in winter/spring, their ice-crystal plumes. Some of these sub-visible plumes are observed to penetrate the Arctic inversion. Snow-melt maps for the entire Arctic prepared for four summer seasons have been used to derive surface-albedo data. From these data the variability of the surface-energy balance is estimated to be equivalent to 0.6 m of ice melt.

For a $\mathbb{Z}^{d}$ -action $\unicode[STIX]{x1D6FC}$ by commuting homeomorphisms of a compact metric space, Lind introduced a dynamical zeta function that generalizes the dynamical zeta function of a single transformation. In this article, we investigate this function when $\unicode[STIX]{x1D6FC}$ is generated by continuous automorphisms of a compact abelian zero-dimensional group. We address Lind’s conjecture concerning the existence of a natural boundary for the zeta function and prove this for two significant classes of actions, including both zero entropy and positive entropy examples. The finer structure of the periodic point counting function is also examined and, in the zero entropy case, we show how this may be severely restricted for subgroups of prime index in $\mathbb{Z}^{d}$ . We also consider a related open problem concerning the appearance of a natural boundary for the dynamical zeta function of a single automorphism, giving further weight to the Pólya–Carlson dichotomy proposed by Bell and the authors.

This article argues that the Chinese state has more highly articulated policies to deal with social disturbance than previously recognized by specialists. It does so by highlighting and critically analyzing the policies followed to improve the opportunities for migrant worker representation. The state has adopted a three-pronged policy. It has improved migrant worker rights, encouraged the official unions to help enforce these rights and allowed NGOs to offer certain services. The official unions are encouraged to adopt a legal watchdog role by a combination of legislation and limited external organizational competition. We argue that the dynamic of organizational competition is a previously unrecognized factor in moving China in a ‘socialist corporatist’ direction.

An algebraic flip system is an action of the infinite dihedral group by automorphisms of a compact abelian group $X$. In this paper, a fundamental structure theorem is established for irreducible algebraic flip systems, that is, systems for which the only closed invariant subgroups of $X$ are finite. Using irreducible systems as a foundation, for expansive algebraic flip systems, periodic point counting estimates are obtained that lead to the orbit growth estimate

$$\begin{eqnarray}Ae^{hN}\leqslant {\it\pi}(N)\leqslant Be^{hN},\end{eqnarray}$$

${\it\pi}(N)$

$N$

$A$

$B$

$h$

A new phase Zn3Cu4Sb2O12 was analyzed by X-ray powder diffraction. Its monoclinic unit cell parameters are a=21.0378(19) Å, b=8.7825(7) Å, c=5.5860(4) Å, and β=112.578(7)°, and the space group is either Cc (9) or C2/c (15). From comparison with density measurements, Z=4.

The purpose of this paper is to exhibit highly structured subdynamics for a class of non-expansive algebraic ℤd-actions based on the closed orbits of elements of an action. This is done using dynamical Dirichlet series to encode orbit counts. It is shown that there is a distinguished group homomorphism from ℤd onto a finite abelian group that controls the form of the Dirichlet series of elements of an action and that these series have common analytic properties. Corresponding orbit growth asymptotics are subsequently investigated.

An algebraic $\mathbb{Z}^d$-action of entropy rank one is one for which each element has finite entropy. Using the structure theory of these actions due to Einsiedler and Lind, this paper investigates dynamical zeta functions for elements of the action. An explicit periodic point formula is obtained leading to a uniform parameterization of the zeta functions that arise in expansive components of an expansive action, together with necessary and sufficient conditions for rationality in a more general setting.

A framework for understanding the geometry of continuous actions of $\mathbb Z^d$ was developed by Boyle and Lind using the notion of expansive behaviour along lower-dimensional subspaces. For algebraic $\mathbb Z^d$-actions of entropy rank one, the expansive subdynamics are readily described in terms of Lyapunov exponents. Here we show that periodic point counts for elements of an entropy rank-one action determine the expansive subdynamics. Moreover, the finer structure of the non-expansive set is visible in the topological and smooth structure of a set of functions associated to the periodic point data.

We study mixing properties of algebraic actions of $\mathbb Q^d$, showing in particular that prime mixing $\mathbb Q^d$ actions on connected groups are mixing of all orders, as is the case for $\mathbb Z^d$-actions. This is shown using a uniform result on the solution of $S$-unit equations in characteristic zero fields due to Evertse, Schlickewei and W. Schmidt. In contrast, algebraic actions of the much larger group $\mathbb Q^*$ are shown to behave quite differently, with finite order of mixing possible on connected groups.

A general framework for investigating topological actions of \mathbb{Z}^d on compact metric spaces was proposed by Boyle and Lind in terms of expansive behavior along lower-dimensional subspaces of \mathbb{R}^d. Here we completely describe this expansive behavior for the class of algebraic \mathbb{Z}^d-actions given by commuting automorphisms of compact abelian groups. The description uses the logarithmic image of an algebraic variety together with a directional version of Noetherian modules over the ring of Laurent polynomials in several commuting variables.

We introduce two notions of rank for topological \mathbb{Z}^d-actions, and for algebraic \mathbb{Z}^d-actions describe how they are related to each other and to Krull dimension. For a linear subspace of \mathbb{R}^d we define the group of points homoclinic to zero along the subspace, and prove that this group is constant within an expansive component.