Interpolating Action for Strings and Membranes - a Study of Symmetries in the Constrained Hamiltonian Approach

A master action for bosonic strings and membranes, interpolating between the Nambu--Goto and Polyakov formalisms, is discussed. The role of the gauge symmetries vis-\`{a}-vis reparametrization symmetries of the various actions is analyzed by a constrained Hamiltonian approach. This analysis reveals the difference between strings and higher branes, which is essentially tied to a degree of freedom count. The cosmological term for membranes follows naturally in this scheme. The conncetion of our aproach with the Arnowitt--Deser--Misner representation in general relativity is illuminated.Comment: LaTex, 23 pages; discussion on ADM representation included and new references adde

Star formation in evolving molecular clouds

Molecular clouds are the principle stellar nurseries of our universe, keeping them in the focus of both observational and theoretical studies. From observations, some of the key properties of molecular clouds are well known but many questions regarding their evolution and star formation activity remain open. While numerical simulations feature a large number and complexity of involved physical processes, this plenty of effects may hide the fundamentals that determine the evolution of molecular clouds and enable the formation of stars. Purely analytical models, on the other hand, tend to suffer from rough approximations or a lack of completeness, limiting their predictive power. In this paper, we present a model that incorporates central concepts of astrophysics as well as reliable results from recent simulations of molecular clouds and their evolutionary paths. Based on that, we construct a self-consistent semi-analytical framework that describes the formation, evolution and star formation activity of molecular clouds, including a number of feedback effects to account for the complex processes inside those objects. The final equation system is solved numerically but at much lower computational expense than, e.g., hydrodynamical descriptions of comparable systems. The model presented in this paper agrees well with a broad range of observational results, showing that molecular cloud evolution can be understood as an interplay between accretion, global collapse, star formation and stellar feedback.Comment: 11 pages, 11 figures. Accepted for publication in A&

Fixed-step anonymous overtaking and catching-up

We investigate criteria for evaluating infinite utility streams that satisfy Fixed-step anonymity and includes some notion of overtaking or catching-up. We do so in a generalized setting which do not require us to specify the underlying finite-dimensional criterion (e.g., utilitarianism or leximin). We present axiomatizations that rely on weaker axioms than those in the literature, and which in one case is new. We also provide a complete analysis of the relationships between the symmetric parts of these criteria and likewise for the asymmetric parts.Intergenerational justice; Utilitarianism; Leximin

Markets and Violence

In this commentary, I address different forms of corporate violence, in particular how some contemporary corporate practices result in violence. Violence is carried out often without impunity by a market-state nexus that enables accumulation by dispossession. Structural violence concentrates power on certain groups while creating a class of disposable labour. Epistemic violence involves using language and law to disempower specific groups of people. The state often uses instrumental violence to quell resistance. I discuss how violence operates in the political economy by discussing conflicts in the extractive industries