Some Basic Radio System OPSEC Considerations

This is an unscientific introduction to basic radio frequency system OPSEC aspects that I have found to be overlooked and lacking in high security system deployments that may have benefited from them

A Covert Channel Using Named Resources

A network covert channel is created that uses resource names such as addresses to convey information, and that approximates typical user behavior in order to blend in with its environment. The channel correlates available resource names with a user defined code-space, and transmits its covert message by selectively accessing resources associated with the message codes. In this paper we focus on an implementation of the channel using the Hypertext Transfer Protocol (HTTP) with Uniform Resource Locators (URLs) as the message names, though the system can be used in conjunction with a variety of protocols. The covert channel does not modify expected protocol structure as might be detected by simple inspection, and our HTTP implementation emulates transaction level web user behavior in order to avoid detection by statistical or behavioral analysis.Comment: 9 page

Boundary Counterterms and the Thermodynamics of 2-D Black Holes

We utilize a novel method to study the thermodynamics of two dimensional type 0A black holes with constant RR flux. Our approach is based on the Hamilton-Jacobi method of deriving boundary counterterms. We demonstrate this approach by recovering the standard results for a well understood example, Witten's black hole. Between this example and the 0A black hole we find universal expressions for the entropy and black hole mass, as well as the infra-red divergence of the partition function. As a non-trivial check of our results we verify the first law of thermodynamics for these systems. Our results for the mass disagree with the predictions of a proposed matrix model dual of the 0A black hole.Comment: 27 pages, uses utarticle.cls; corrected typos and added reference

Gravity Dual of a Quantum Hall Plateau Transition

We show how to model the transition between distinct quantum Hall plateaus in terms of D-branes in string theory. A low energy theory of 2+1 dimensional fermions is obtained by considering the D3-D7 system, and the plateau transition corresponds to moving the branes through one another. We study the transition at strong coupling using gauge/gravity duality and the probe approximation. Strong coupling leads to a novel kind of plateau transition: at low temperatures the transition remains discontinuous due to the effects of dynamical symmetry breaking and mass generation, and at high temperatures is only partially smoothed out.Comment: 27 pages, 6 figures, harvmac; v2, references and minor comments added, version to be submitted to JHEP; v3, corrections to section

The Moduli Space and Phase Structure of Heterotic Strings in Two Dimensions

We explore the moduli space of heterotic strings in two dimensions. In doing so, we introduce new lines of compactified theories with Spin(24) gauge symmetry and discuss compactifications with Wilson lines. The phase structure of d=2 heterotic string theory is examined by classifying the hypersurfaces in moduli space which support massless quanta or discrete states. Finally, we compute the torus amplitude over much of the moduli space.Comment: 23 pages, 1 figure, harvmac.tex; v2: minor changes to introduction, version to be published in Phys. Rev.

Two Flaws In Business Cycle Accounting

Using 'business cycle accounting' (BCA), Chari, Kehoe and McGrattan (2006) (CKM) conclude that models of financial frictions which create a wedge in the intertemporal Euler equation are not promising avenues for modeling business cycle dynamics. There are two reasons that this conclusion is not warranted. First, small changes in the implementation of BCA overturn CKM's conclusions. Second, one way that shocks to the intertemporal wedge impact on the economy is by their spillover effects onto other wedges. This potentially important mechanism for the transmission of intertemporal wedge shocks is not identified under BCA. CKM potentially understate the importance of these shocks by adopting the extreme position that spillover effects are zero.

Two flaws in business cycle dating

Using “business cycle accounting,” Chari, Kehoe, and McGrattan (2006) conclude that models of financial frictions which create a wedge in the intertemporal Euler equation are not promising avenues for modeling business cycle dynamics. There are two reasons that this conclusion is not warranted. First, small changes in the implementation of business cycle accounting overturn Chari, Kehoe, and McGrattan’s conclusions. Second, one way that shocks to the intertemporal wedge affect the economy is by their spillover effects onto other wedges. This potentially important mechanism for the transmission of intertemporal-wedge shocks is not identified under business cycle accounting. Chari, Kehoe, and McGrattan potentially understate the importance of these shocks by adopting the extreme position that spillover effects are zero.Business cycles

The Transfer Playbook: Essential Practices For Two- And Four-year Colleges

Recognizing the critical need to help millions of community college students failed by current transfer practices and policies.  A new report provides a detailed guide for two- and four-year colleges on how to improve bachelor's degree outcomes for students who start at community college.Every year, millions of students aiming to attain a bachelor's degree attend community colleges because of their affordability and accessibility. Most will not realize their goals. While the vast majority of students report they want to earn a bachelor's degree, only 14 percent of degree-seeking students achieve that goal within six years, according to recent research from CCRC, Aspen, and the National Student Clearinghouse Research Center. The odds are worse for low-income students, first-generation college students, and students of color—those most likely to start at a community college