Catastrophic Decays of Compactified Space-Times

Witten long ago pointed out that the simplest Kaluza-Klein theory, without supersymmetry, is subject to a catastrophic instability. There are a variety of string theories which are potentially subject to these instabilities. Here we explore a number of questions: how generic are these instabilities? what happens when a potential is generated on the moduli space? in the presence of supersymmetry breaking, is there still a distinction between supersymmetric and non-supersymmetric states?Comment: Typos corrected, references adde

The interaction between gaze and facial expression in the amygdala and extended amygdala is modulated by anxiety

Behavioral evidence indicates that angry faces are seen as more threatening, and elicit greater anxiety, when directed at the observer, whereas the influence of gaze on the processing of fearful faces is less consistent. Recent research has also found inconsistent effects of expression and gaze direction on the amygdala response to facial signals of threat. However, such studies have failed to consider the important influence of anxiety on the response to signals of threat; an influence that is well established in behavioral research and recent neuroimaging studies. Here, we investigated the way in which individual differences in anxiety would influence the interactive effect of gaze and expression on the response to angry and fearful faces in the human extended amygdala. Participants viewed images of fearful, angry and neutral faces, either displaying an averted or direct gaze. We found that state anxiety predicted an increased response in the dorsal amygdala/substantia innominata (SI) to angry faces when gazing at, relative to away from the observer. By contrast, high state anxious individuals showed an increased amygdala response to fearful faces that was less dependent on gaze. In addition, the relationship between state anxiety and gaze on emotional intensity ratings mirrored the relationship between anxiety and the amygdala/SI response. These results have implications for understanding the functional role of the amygdala and extended amygdala in processing signals of threat, and are consistent with the proposed role of this region in coding the relevance or significance of a stimulus to the observer

Dynamics in atomic signaling games

We study an atomic signaling game under stochastic evolutionary dynamics. There is a finite number of players who repeatedly update from a finite number of available languages/signaling strategies. Players imitate the most fit agents with high probability or mutate with low probability. We analyze the long-run distribution of states and show that, for sufficiently small mutation probability, its support is limited to efficient communication systems. We find that this behavior is insensitive to the particular choice of evolutionary dynamic, a property that is due to the game having a potential structure with a potential function corresponding to average fitness. Consequently, the model supports conclusions similar to those found in the literature on language competition. That is, we show that efficient languages eventually predominate the society while reproducing the empirical phenomenon of linguistic drift. The emergence of efficiency in the atomic case can be contrasted with results for non-atomic signaling games that establish the non-negligible possibility of convergence, under replicator dynamics, to states of unbounded efficiency loss

Gorenstein Projective (Pre)Covers

The existence of the Gorenstein projective precovers is one of the main open problems in Gorenstein Homological algebra. We give sufficient conditions in order for the class of Gorenstein projective complexes to be special precovering in the category of complexes of R-modules Ch(R). More precisely, we prove that if every complex in Ch(R) has a special Gorenstein flat cover, every Gorenstein projective complex is Gorenstein flat, and every Gorenstein flat complex has finite Goenstein projective dimension, then the class of Gorenstein projective complexes, GP(C), is special precovering in Ch(R)

Effects of Orientation Change on Spatial Learning of Novel Environments on Younger and Older Adults

Yamamoto and DeGirolamo (2012) found that increasing age has unequal effects of impairment on spatial learning dependent on the perspective in which an environment is learned. Further, the learned condition of ground-level perspective (first-person exploratory) showed greater decline in elderly participants than was found in aerial (map reading) conditions. These results supported previous research involving fMRI scans implicating the medial temporal lobe (MTL) role in exploratory navigation of novel environments and MRI scans indicating MTL atrophy with age. However, Yamamoto and DeGirolamo (2012) did not consider the effects of conducting the experiment with one condition being presented with changing orientation (ground-level) and the other condition having fixed orientation (aerial). Utilizing new research revealing the MTL\u27s role in orientation processing, the present study reexamined Yamamoto and DeGirolamo (2012) findings with the introduction of the condition aerial-with-turns (map reading with changing orientation). The findings of this experiment suggest changing orientation in the learning condition has greater impact on elderly participants\u27 performance of spatial learning tasks than that of the perspective in which the learning condition is i

Carbon Free Boston: Offsets Technical Report

Part of a series of reports that includes: Carbon Free Boston: Summary Report; Carbon Free Boston: Social Equity Report; Carbon Free Boston: Technical Summary; Carbon Free Boston: Buildings Technical Report; Carbon Free Boston: Transportation Technical Report; Carbon Free Boston: Waste Technical Report; Carbon Free Boston: Energy Technical Report; Available at http://sites.bu.edu/cfb/OVERVIEW: The U.S. Environmental Protection Agency defines offsets as a specific activity or set of activities intended to reduce GHG emissions, increase the storage of carbon, or enhance GHG removals from the atmosphere [1]. From a city perspective, they provide a mechanism to negate residual GHG emissions— those the city is unable to reduce directly—by supporting projects that avoid or sequester them outside of the city’s reporting boundary. Offsetting GHG emissions is a controversial topic for cities, as the co-benefits of the investment are typically not realized locally. For this reason, offsetting emissions is considered a last resort, a strategy option available when the city has exhausted all others. However, offsets are likely to be a necessity to achieve carbon neutrality by 2050 and promote emissions reductions in the near term. While public and private sector partners pursue the more complex systems transformation, cities can utilize offsets to support short-term and relatively cost-effective reductions in emissions. Offsets can be a relatively simple, certain, and high-impact way to support the transition to a low-carbon world. This report focuses on carbon offset certificates, more often referred to as offsets. Each offset represents a metric ton of verified carbon dioxide (CO2) or equivalent emissions that is reduced, avoided, or permanently removed from the atmosphere (“sequestered”) through an action taken by the creator of the offset. The certificates can be traded and retiring (that is, not re-selling) offsets can be a useful component of an overall voluntary emissions reduction strategy, alongside activities to lower an organization’s direct and indirect emissions. In the Global Protocol for Community-Scale Greenhouse Gas Emissions Inventories (GPC), the GHG accounting system used by the City of Boston, any carbon offset certificates that the City has can be deducted from the City’s total GHG emissions.http://sites.bu.edu/cfb/files/2019/06/CFB_Offsets_Technical_Report_051619.pdfPublished versio

Carbon Free Boston: Energy Technical Report

Part of a series of reports that includes: Carbon Free Boston: Summary Report; Carbon Free Boston: Social Equity Report; Carbon Free Boston: Technical Summary; Carbon Free Boston: Buildings Technical Report; Carbon Free Boston: Transportation Technical Report; Carbon Free Boston: Waste Technical Report; Carbon Free Boston: Offsets Technical Report; Available at http://sites.bu.edu/cfb/INTRODUCTION: The adoption of clean energy in Boston’s buildings and transportation systems will produce sweeping changes in the quantity and composition of the city’s demand for fuel and electricity. The demand for electricity is expected to increase by 2050, while the demand for petroleum-based liquid fuels and natural gas within the city is projected to decline significantly. The city must meet future energy demand with clean energy sources in order to meet its carbon mitigation targets. That clean energy must be procured in a way that supports the City’s goals for economic development, social equity, environmental sustainability, and overall quality of life. This chapter examines the strategies to accomplish these goals. Improved energy efficiency, district energy, and in-boundary generation of clean energy (rooftop PV) will reduce net electric power and natural gas demand substantially, but these measures will not eliminate the need for electricity and gas (or its replacement fuel) delivered into Boston. Broadly speaking, to achieve carbon neutrality by 2050, the city must therefore (1) reduce its use of fossil fuels to heat and cool buildings through cost-effective energy efficiency measures and electrification of building thermal services where feasible; and (2) over time, increase the amount of carbon-free electricity delivered to the city. Reducing energy demand though cost effective energy conservation measures will be necessary to reduce the challenges associated with expanding the electricity delivery system and sustainably sourcing renewable fuels.Published versio