Consistent matter couplings for Plebanski gravity

We develop a scheme for the minimal coupling of all standard types of tensor and spinor field matter to Plebanski gravity. This theory is a geometric reformulation of vacuum general relativity in terms of two-form frames and connection one-forms, and provides a covariant basis for various quantization approaches. Using the spinor formalism we prove the consistency of the newly proposed matter coupling by demonstrating the full equivalence of Plebanski gravity plus matter to Einstein--Cartan gravity. As a byproduct we also show the consistency of some previous suggestions for matter actions.Comment: 20 page

Commuting in small towns in rural areas: the case of St Andrews.

Since many rural commuters depend on the private car due to lack of convenient public transport, car reduction policies designed for large cities with ample public transport may be unsuitable for smaller towns. In particular, pricing policies designed to encourage public transport use may be less effective, as commuters with no convenient substitute to driving will be unable to switch. This paper develops multinomial and mixed logit models of commuters’ mode choice using data from a survey of commuters in the University of St Andrews. We find that the direct elasticities of the car mode are comparable to estimates reported in studies of commuting in larger urban areas, while the demand for public transport is considerably more elastic. The value of in-vehicle time is found to be about half of the UK average, reflecting that the roads in the St Andrews area are relatively uncongested.Mode choice, Rural commuting, Discrete choice models

Transient and stationary behavior of the Olami-Feder-Christensen earthquake model

Using long-term computer simulations and mean-field like arguments, we investigate the transient time and the properties of the stationary state of the Olami-Feder-Christensen earthquake model as function of the coupling parameter $\alpha$ and the system size $N$. The most important findings are that the transient time diverges nonanalytically when $\alpha$ approaches zero, and that the avalanche-size distribution will not approach a power law with increasing system size.Comment: 10 pages, 8 figure

Incoherent ensemble dynamics in disordered systems

We derive a quantum master equation which describes the dynamics of the ensemble-averaged state of homogeneous disorder models at short times, and mediates a transition from coherent superpositions into classical mixtures. While each single realization follows unitary dynamics, this decoherencelike behavior arises as a consequence of the ensemble average. The master equation manifestly reflects the translational invariance of the disorder correlations and allows us to relate the disorder-induced dynamics to a collisional decoherence process, where the disorder correlations determine the spatial decay of coherences. We apply our theory to the (one-dimensional) Anderson model.Comment: 7 page

Schwinger-Keldysh formalism II: Thermal equivariant cohomology

Causally ordered correlation functions of local operators in near-thermal quantum systems computed using the Schwinger-Keldysh formalism obey a set of Ward identities. These can be understood rather simply as the consequence of a topological (BRST) algebra, called the universal Schwinger-Keldysh superalgebra, as explained in our companion paper arXiv:1610.01940. In the present paper we provide a mathematical discussion of this topological algebra. In particular, we argue that the structures can be understood in the language of extended equivariant cohomology. To keep the discussion self-contained, we provide a basic review of the algebraic construction of equivariant cohomology and explain how it can be understood in familiar terms as a superspace gauge algebra. We demonstrate how the Schwinger-Keldysh construction can be succinctly encoded in terms a thermal equivariant cohomology algebra which naturally acts on the operator (super)-algebra of the quantum system. The main rationale behind this exploration is to extract symmetry statements which are robust under renormalization group flow and can hence be used to understand low-energy effective field theory of near-thermal physics. To illustrate the general principles, we focus on Langevin dynamics of a Brownian particle, rephrasing some known results in terms of thermal equivariant cohomology. As described elsewhere, the general framework enables construction of effective actions for dissipative hydrodynamics and could potentially illumine our understanding of black holes.Comment: 72 pages; v2: fixed typos. v3: minor clarifications and improvements to non-equilbirum work relations discussion. v4: typos fixed. published versio

The eightfold way to dissipation

We provide a complete characterization of hydrodynamic transport consistent with the second law of thermodynamics at arbitrary orders in the gradient expansion. A key ingredient in facilitating this analysis is the notion of adiabatic hydrodynamics, which enables isolation of the genuinely dissipative parts of transport. We demonstrate that most transport is adiabatic. Furthermore, of the dissipative part, only terms at the leading order in gradient expansion are constrained to be sign-definite by the second law (as has been derived before).Comment: 5 pages, 1 figure. v2: minor clarifications. v3: minor changes. title in published version differ

The incidence of capital taxation and the magnitude of its burden.

Capital ; Taxation

Do state corporate income taxes reduce wages?

Amid falling revenues and impending budget shortfalls, state policymakers must find ways to increase revenue, cut spending, or both. At the same time, they must develop policies that attract or keep businesses and jobs. Some policymakers may consider raising corporate tax rates because it avoids directly taxing workers who are already suffering the effects of this recession. But as states reevaluate their current tax policy, it is important to consider the effects of each tax component. One important question is: Who will bear the burden of the taxes? ; State corporate income taxes are complex, and thus the answer to this question is far from obvious. Many believe that the state corporate tax structure is highly progressive because the corporate capital taxed is owned disproportionately by wealthy individuals. In today's economy, however, the burden of the corporate tax may have shifted to consumers or labor, resulting in a less progressive tax structure. ; Research has shown that in some cases labor bears a substantial weight of the corporate tax. While this burden has fluctuated over time, the relationship between corporate taxes and wages has been consistently negative. In other words, higher corporate taxes are typically associated with lower wages. ; Felix examines the impact of state corporate taxes on wages. She shows that corporate taxes reduce wages and that the magnitude of the negative relationship between the taxes and wages has increased over the past 30 years. She also finds that state corporate taxes have a larger negative effect on more highly educated workers.