Thiemann transform for gravity with matter fields

The generalised Wick transform discovered by Thiemann provides a well-established relation between the Euclidean and Lorentzian theories of general relativity. We extend this Thiemann transform to the Ashtekar formulation for gravity coupled with spin-1/2 fermions, a non-Abelian Yang-Mills field, and a scalar field. It is proved that, on functions of the gravitational and matter phase space variables, the Thiemann transform is equivalent to the composition of an inverse Wick rotation and a constant complex scale transformation of all fields. This result holds as well for functions that depend on the shift vector, the lapse function, and the Lagrange multipliers of the Yang-Mills and gravitational Gauss constraints, provided that the Wick rotation is implemented by means of an analytic continuation of the lapse. In this way, the Thiemann transform is furnished with a geometric interpretation. Finally, we confirm the expectation that the generator of the Thiemann transform can be determined just from the spin of the fields and give a simple explanation for this fact.Comment: LaTeX 2.09, 14 pages, no figure

The Mexican Identity and Music: Audioscapes and The Transnational Death Metal Band Brujeria

The California-based Mexican-American “activist” metal band Brujeria, uses a powerful, yet conflicting, blend of nihilism, anarchism, and racism with a dose of hyper-patriotism in its attempt to convey the voice of oppressed Mexicans on both sides of the border. While it is uncertain whether or not Brujeria is intentionally political, their live performances and song lyrics are highly critical of both the U.S. and Mexico regarding immigration policy, border-crossing, and other issues which have resonated among an international audience. In this paper I explore the conflicting notions of space, performativity, binationality and U.S. Mexico relations within the context of Brujeria messages. While using Brujeria as the focus of my work, I also explain what I call the notion of “Audioscapes.” In simple terms: it deals with the cognitive processes which create perceptions of music from mind to mind, state to state, and space to space

Unitary evolution in Gowdy cosmology

Recent results on the non-unitary character of quantum time evolution in the family of Gowdy T**3 spacetimes bring the question of whether one should renounce in cosmology to the most sacred principle of unitary evolution. In this work we show that the answer is in the negative. We put forward a full nonperturbative canonical quantization of the polarized Gowdy T**3 model that implements the dynamics while preserving unitarity. We discuss possible implications of this result.Comment: 5 pages, no figures. V2 discussion expanded, references added. Final version to appear in PR

Activism for corporate responsibility: Conceptualizing private regulation opportunity structures

In this article, we examine how private regulatory initiatives (PRIs) – which define standards for corporate responsibility (CR) issues and sometimes monitor their application by firms – create opportunities and constraints for activist groups aiming to push firms towards more stringent CR activities. Drawing on social movement theory, we conceptualize how private regulation opportunity structures affect such CR-based activist groups' targets and tactics at both the firm and field levels. At the field level, we argue that both radical and reformative activist groups direct most of their time and resources towards PRIs with comparatively more stringent standards. At the firm level, while radical activist groups are likely to target firms participating in more stringent PRIs, reformative activist groups target firms participating in less stringent PRIs, or those that do not participate in PRIs at all. When facing unfavourable opportunity structures, CR-based activist groups tend either to advocate the creation of new PRIs or to shift their activities to pressure other focal points. This article contributes to moving beyond extant literature's emphasis of PRIs as settlements of contentious firm–activist interactions towards also viewing them as starting points for activist groups aiming to push firms towards a more substantive CR engagement

Activists as moral entrepreneurs: How shareholder activists brought active ownership to Switzerland

Action from activists is at the origin of many initiatives that end up injecting moral concerns into the way companies operate. In such instances, activists function as moral entrepreneurs that lastingly change the definition of what constitutes morally acceptable corporate behavior. Yet, in order to have such a lasting effect on companies, activist efforts need to pass through multiple stages that deal with both the effective mobilization of their own constituents and the triggering of corporate responses that can induce broader change in the economy. In the present article, we study how local shareholder activists initiated and helped sustain the process that led to the establishment of active ownership in Switzerland between 1997 and 2011. Active ownership refers to the active engagement of shareholders with firms to push them towards considering environmental, social, and corporate governance (ESG) criteria in their decision-making. The case illustrates the processual nature of moralizing dynamics initiated by activists and emphasizes the long-term and cumulative nature of many moralization projects

Spherically symmetric perfect fluid in area-radial coordinates

We study the spherically symmetric collapse of a perfect fluid using area-radial coordinates. We show that analytic mass functions describe a static regular centre in these coordinates. In this case, a central singularity can not be realized without an infinite discontinuity in the central density. We construct mass functions involving fluid dynamics at the centre and investigate the relationship between those and the nature of the singularities.Comment: Accepted by CQG. LaTex file, 14 pages, no figure

Quantum Cylindrical Waves and Sigma Models

We analyze cylindrical gravitational waves in vacuo with general polarization and develop a viewpoint complementary to that presented recently by Niedermaier showing that the auxiliary sigma model associated with this family of waves is not renormalizable in the standard perturbative sense.Comment: 11 pages (DIN A4), accepted in International Journal of Modern Physics

Spin wave spectrum of the quantum ferromagnet on the pyrochlore lattice Lu2V2O7

Neutron inelastic scattering has been used to probe the spin dynamics of the quantum (S=1/2) ferromagnet on the pyrochlore lattice Lu2V2O7. Well-defined spin waves are observed at all energies and wavevectors, allowing us to determine the parameters of the Hamiltonian of the system. The data are found to be in excellent overall agreement with a minimal model that includes a nearest- neighbour Heisenberg exchange J = 8:22(2) meV and a Dzyaloshinskii-Moriya interaction (DMI) D =1:5(1) meV. The large DMI term revealed by our study is broadly consistent with the model developed by Onose et al. to explain the magnon Hall effect they observed in Lu2V2O7 [1], although our ratio of D=J = 0:18(1) is roughly half of their value and three times larger than calculated by ab initio methods [2].Comment: 5 pages, 4 figure

Plane waves in quantum gravity: breakdown of the classical spacetime

Starting with the Hamiltonian formulation for spacetimes with two commuting spacelike Killing vectors, we construct a midisuperspace model for linearly polarized plane waves in vacuum gravity. This model has no constraints and its degrees of freedom can be interpreted as an infinite and continuous set of annihilation and creation like variables. We also consider a simplified version of the model, in which the number of modes is restricted to a discrete set. In both cases, the quantization is achieved by introducing a Fock representation. We find regularized operators to represent the metric and discuss whether the coherent states of the quantum theory are peaked around classical spacetimes. It is shown that, although the expectation value of the metric on Killing orbits coincides with a classical solution, its relative fluctuations become significant when one approaches a region where null geodesics are focused. In that region, the spacetimes described by coherent states fail to admit an approximate classical description. This result applies as well to the vacuum of the theory.Comment: 11 pages, no figures, version accepted for publication in Phys. Rev.