Unitarity Relations in c=1 Liouville Theory

We consider the S-matrix of c=1 Liouville theory with vanishing cosmological constant. We examine some of the constraints imposed by unitarity. These completely determine (N,2) amplitudes at tree level in terms of the (N,1) amplitudes when the plus tachyon momenta take generic values. A surprising feature of the matrix model results is the lack of particle creation branch cuts in the higher genus amplitudes. In fact, we show the naive field theory limit of Liouville theory would predict such branch cuts. However, unitarity in the full string theory ensures that such cuts do not appear in genus one (N,1) amplitudes. We conclude with some comments about the genus one (N,2) amplitudes.Comment: 14 pages, 3 figures (not included), phyzz

Taking up the Slack: Lessons from a Cap-and-Trade Program in Chicago

The Emissions Reduction Market System (ERMS), an emissions-trading program for volatile organic materials (VOMs) in Chicago, Illinois, has been characterized by emissions significantly below the annual allocation of emission allowances, allowance prices much lower than predicted, limited trading, and emission allowances that expire unused. Essentially, it appears that a fundamental prerequisite for a tradable allowance program is missing—there is no scarcity of allowances. We evaluate a variety of hypotheses that may explain why the ERMS cap does not appear to be affecting abatement behavior and identify three that contributed to the lack of scarcity in the ERMS program: (1) a baseline process that inflated the cap; (2) hazardous air pollutant regulations that contributed to VOM reductions at some sources; and (3) numerous facility shutdowns. We conclude that the ERMS experience illustrates the inherent unpredictability of economic, regulatory, and other factors when setting an emissions target; a conclusion that resonates with the recent experience of the European Union Emissions Trading Scheme. This argues for gathering reliable emissions data, developing sophisticated emissions projections, and making transparent assumptions about the impacts of other policies and regulations during the program planning and design phase. However, even with all these attributes, it is still difficult to anticipate every possible outcome. Thus, it is desirable to have robust mechanisms to address the uncertainties of emissions-trading markets and to make midcourse corrections if necessary. Finally, we offer some comments on how to think about the results of ERMS versus a hypothetical command and control program that might have been designed to reach the same environmental outcome.emissions-trading, ERMS, European Union, climate change

Automated technologies needed to prevent radioactive materials from reentering the atmosphere

Project SIREN (Search, Intercept, Retrieve, Expulsion Nuclear) was created to identify and evaluate the technologies and operational strategies needed to rendezvous with and capture aerospace radioactive materials (e.g., a distressed or spent space reactor core) before such materials can reenter the terrestrial atmosphere and then to safely move these captured materials to an acceptable space destination for proper disposal. A major component of the current project SIREN effort is the development of an interactive technology model (including a computerized data base) that explores, in building-block fashion, the interaction of the technologies and procedures needed to successfully accomplish a SIREN mission. The SIREN model will include appropriate national and international technology elements--both contemporary and projected into the next century. To obtain maximum flexibility and use, the SIREN technology data base is being programmed for use on 286-class PC's. The major technical elements for a successful SIREN mission include: ground and space-based tracking, launch vehicles of needed payload capacity, telerobotic systems, sensors, capture technologies, and space transport and disposal. However, Project SIREN also will impose specialized requirements including the use of dextrous aerospace systems capable of properly functioning in intense radiation and thermal environments

Fixed parameter tractability of crossing minimization of almost-trees

We investigate exact crossing minimization for graphs that differ from trees by a small number of additional edges, for several variants of the crossing minimization problem. In particular, we provide fixed parameter tractable algorithms for the 1-page book crossing number, the 2-page book crossing number, and the minimum number of crossed edges in 1-page and 2-page book drawings.Comment: Graph Drawing 201

HCU400: An Annotated Dataset for Exploring Aural Phenomenology Through Causal Uncertainty

The way we perceive a sound depends on many aspects-- its ecological frequency, acoustic features, typicality, and most notably, its identified source. In this paper, we present the HCU400: a dataset of 402 sounds ranging from easily identifiable everyday sounds to intentionally obscured artificial ones. It aims to lower the barrier for the study of aural phenomenology as the largest available audio dataset to include an analysis of causal attribution. Each sample has been annotated with crowd-sourced descriptions, as well as familiarity, imageability, arousal, and valence ratings. We extend existing calculations of causal uncertainty, automating and generalizing them with word embeddings. Upon analysis we find that individuals will provide less polarized emotion ratings as a sound's source becomes increasingly ambiguous; individual ratings of familiarity and imageability, on the other hand, diverge as uncertainty increases despite a clear negative trend on average

Superconductivity of disordered Dirac fermions

We study the effect of disorder on massless, spinful Dirac fermions in two spatial dimensions with attractive interactions, and show that the combination of disorder and attractive interactions is deadly to the Dirac semimetal phase. First, we derive the zero temperature phase diagram of a clean Dirac fermion system with tunable doping level ({\mu}) and attraction strength (g). We show that it contains two phases: a superconductor and a Dirac semimetal. Then, we show that arbitrarily weak disorder destroys the Dirac semimetal, turning it into a superconductor. We discuss the strength of the superconductivity for both long range and short range disorder. For long range disorder, the superconductivity is exponentially weak in the disorder strength. For short range disorder, a uniform mean field analysis predicts that superconductivity should be doubly exponentially weak in the disorder strength. However, a more careful treatment of mesoscopic fluctuations suggests that locally superconducting puddles should form at a much higher temperature, and should establish global phase coherence at a temperature that is only exponentially small in weak disorder. We also discuss the effect of disorder on the quantum critical point of the clean system, building in the effect of disorder through a replica field theory. We show that disorder is a relevant perturbation to the supersymmetric quantum critical point. We expect that in the presence of attractive interactions, the flow away from the critical point ends up in the superconducting phase, although firm conclusions cannot be drawn since the renormalization group analysis flows to strong coupling. We argue that although we expect the quantum critical point to get buried under a superconducting phase, signatures of the critical point may be visible in the finite temperature quantum critical regime.Comment: Added some discussion, particularly pertaining to proximity effec