Inflationary Hubble Parameter from the Gravitational Wave Spectrum in the General Slow-roll Approximation

Improved general slow-roll formulae giving the primordial gravitational wave spectrum are derived in the present work. Also the first and second order general slow-roll inverse formulae giving the Hubble parameter $H$ in terms of the gravitational wave spectrum are derived. Moreover, the general slow-roll consistency condition relating the scalar and tensor spectra is obtained

The effects of polydispersity on the morphology of polystyrene-polyferrocenyldimethylsilane block copolymer thin films

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 35).Introduction: As the size of electronic and magnetic devices decreases, nanoscale patterning becomes an increasingly important area of research. Two different approaches have been taken to pattern media: top-down methods such as lithography, and bottom-up methods such as self-assembly. Top-down assembly methods have the advantages of precision and accuracy, but are hard to scale for certain industrial applications due to their low throughput. Self-assembly methods are more easily scalable for applications requiring mass production. Thus, self-assembly has attracted attention and is an area of ongoing research for its potential to create high-throughput, periodic nanoscale patterns. Block copolymers are a class of commonly-studied materials for nanoscale selfassembly. Block copolymers are long molecules that consist of "blocks" of chemically differing polymers attached end-to-end. Under the right conditions, these blocks will phase separate, spontaneously forming periodic microdomains. Diblock copolymers, which have only two blocks, have been found to form a variety of well-ordered morphologies with nanoscale periodicity ...by Joy C. Perkinson.S.B

Schroedinger Invariance from Lifshitz Isometries in Holography and Field Theory

We study non-relativistic field theory coupled to a torsional Newton-Cartan geometry both directly as well as holographically. The latter involves gravity on asymptotically locally Lifshitz space-times. We define an energy-momentum tensor and a mass current and study the relation between conserved currents and conformal Killing vectors for flat Newton-Cartan backgrounds. It is shown that flat NC space-time realizes two copies of the Lifshitz algebra that together form a Schroedinger algebra (without the central element). We show why the Schroedinger scalar model has both copies as symmetries and the Lifshitz scalar model only one. Finally we discuss the holographic dual of this phenomenon by showing that the bulk Lifshitz space-time realizes the same two copies of the Lifshitz algebra.Comment: 5 pages, modified abstract, clarifications added, typos fixed, refs update

Cognitive radio-enabled Internet of Vehicles (IoVs): a cooperative spectrum sensing and allocation for vehicular communication

Internet of Things (IoTs) era is expected to empower all aspects of Intelligent Transportation System (ITS) to improve transport safety and reduce road accidents. US Federal Communication Commission (FCC) officially allocated 75MHz spectrum in the 5.9GHz band to support vehicular communication which many studies have found insufficient. In this paper, we studied the application of Cognitive Radio (CR) technology to IoVs in order to increase the spectrum resource opportunities available for vehicular communication, especially when the officially allocated 75MHz spectrum in 5.9GHz band is not enough due to high demands as a result of increasing number of connected vehicles as already foreseen in the near era of IoTs. We proposed a novel CR Assisted Vehicular NETwork (CRAVNET) framework which empowers CR enabled vehicles to make opportunistic usage of licensed spectrum bands on the highways. We also developed a novel co-operative three-state spectrum sensing and allocation model which makes CR vehicular secondary units (SUs) aware of additional spectrum resources opportunities on their current and future positions and applies optimal sensing node allocation algorithm to guarantee timely acquisition of the available channels within a limited sensing time. The results of the theoretical analyses and simulation experiments have demonstrated that the proposed model can significantly improve the performance of a cooperative spectrum sensing and provide vehicles with additional spectrum opportunities without harmful interference against the Primary Users (PUs) activities

Phase transitions and bubble nucleations for a phi^6 model in curved spacetime

Condsidering a massive self-interacting phi ^6 scalar field coupled arbitrarily to a (2+1) dimensional Bianchi type-I spacetime, we evaluate the one-loop effective potential. It is found that phi ^6 potential can be regularized in (2+1) dimensional curved spacetime. A finite expression for the energy-momentum tensor is obtained for this model. Evaluating the finite temperature effective potential, the temperature dependence of phase transitions is studied. The crucial dependence of the phase transitions on the spacetime curvature and on the coupling to gravity are also verified. We also discuss the nucleation of bubbles in a phi ^6 model. It is found that there exists an exact solution for the damped motion of the bubble in the thin wall regime.Comment: 15 pages, 6 figure

“I live a model life, now I’m ready to be a top wife”: Stereotypical Representations of Black Women in Reality Television

Stereotypical representations of Black women have endured throughout various forms of media for decades, with one of the most recent platforms being reality television programming. The theory of encoding and decoding posit dominant stereotypes are key in television encoding. Using critical discourse analysis, this paper demonstrates that the dominant ideologies in the eleventh season of The Real Housewives of Atlanta are social class norms and negative depictions of Black women. I present evidence that RHOA continues to reinforce upper-class ideologies while perpetuating the Jezebel, Sapphire and the Strong Black woman stereotypes. I also identify a correlation with the strong Black woman and the Sapphire stereotype which ultimately calls for more attention to mental health support to Black women who are faced with very difficult situations and have never learnt healthy ways of expressing emotion. With Black women being the highest consumers of Black reality television, the constant hypersexualization, hyperaggression, and self-sacrificing representations of Black women often endorses stereotypes consistent with these representations while upper middle-class ideologies often lead to the implicit denials of social injustices that are as a result of class distinctions

The U.S. Embargo Against Cuba and the Diplomatic Challenges to Extraterritoriality

Many analysts have criticized the U.S. embargo against Cuba as an anachronistic holdover from the Cold War. Yet its problems go well beyond that. In many regards, the U.S. embargo against Cuba represents a caricature of the various American misapplications of economic sanctions: if the goal is to end the Castro regime this policy has not only failed, but has spent half a century doing so. If the intent is to support Cubans in their aspirations for a different political system the sanctions have failed in that regard as well, since even the most vocal dissidents in Cuba criticize the embargo. In the face of the “smart sanctions” movement to develop economic tools that target the leadership rather than the people, the embargo against Cuba represents the opposite pole: it impacts the Cuban population indiscriminately, affecting everything from family travel, to the publication of scientific articles by Cuban scholars, to the cost of buying chicken for Cuban households. This article will briefly describe the history and the main components of the U.S. embargo against Cuba, and the impact of the unilateral measures on Cuba\u27s economy. It will look at some of the ways in which the U.S. embargo is extraterritorial --impacting Cuba\u27s trade with third [*64] countries--as well as ways in which the United States\u27 unilateral embargo functions in effect as a global measure. It will then examine the overwhelming response of the international community, and in particular, the United Nations General Assembly, in condemning the embargo as a violation of international law. This response represents a diplomatic challenge to the United States that is unparalleled in the last fifty years of global governance