M-theory and superstring cosmology: Brane gases in the early universe and nonsingular gravity

Easson, Damien Alexander Brown University 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This thesis will examine two major themes in modern cosmology. The first part of the thesis is concerned with the interface of superstring theory and M-theory with cosmology. We begin by providing a general background of various superstring cosmological models. In particular, we focus on the “Brane Gas” model of string cosmology (BGC) which was developed, in part, by the author. In this scenario the initial state of the Universe is taken to be small, dense and hot with all fundamental degrees of freedom near thermal equilibrium. Such a starting point is in close analogy with the Standard Big-Bang (SBB) model. The topology of the Universe is assumed to be toroidal in all nine spatial dimensions and the Universe is filled with a gas of p-branes. The dynamics of winding modes allow, at most, three spatial dimensions to become large, thus explaining the origin of our macroscopic 3 + 1-dimensional Universe. Specific solutions that are found within the model exhibit loitering, i.e. the Universe experiences a short phase of contraction during which the Hubble radius grows larger than the physical extent of the Universe. As a result, the brane problem (domain wall problem) in BGC is solved. The initial singularity and horizon problems of the SBB scenario are also solved without relying on an inflationary phase. The second part of the thesis focuses on a particular model of nonsingular gravity. This theory is constructed by adding to the usual string frame, dilaton gravity action, higher derivative terms motivated by the limited curvature construction described below. We examine cosmological, spatially homogeneous and isotropic solutions to the resulting equations of motion. All solutions of the resulting theory of gravity with these symmetries are nonsingular and all curvature invariants are bounded. For initial conditions inspired by the pre-big-bang scenario, solutions exist which correspond to a spatially flat Universe starting in a dilaton-dominated superinflationary phase and making a smooth transition to an expanding Friedmann-Robertson-Walker Universe. Hence, the graceful exit problem of pre-big-bang cosmology is solved in a natural way. Using this modified theory of gravity we discuss the ongoing search for a nonsingular four-dimensional Schwarzschild black hole. We end with comments on the hypothesis that our Universe may have been created on the interior of a black hole and the implications of such a scenario.

PHYSICIAN KNOWLEDGE, ATTITUDES, AND PRACTICE REGARDING ENVIRONMENTAL HEALTH HAZARDS: LAY VS. PROFESSIONAL INTERACTION IN A TOXIC WASTE SETTING (LAY PROFESSIONAL INTERACTION, PHYSICIAN EDUCATION)

KELLEY, JUDITH KIRWAN BROWN UNIVERSITY. 1999 해외박사

Des iconoclastes heureux et sans complexe: Pour une dialectique des litteratures francophones (Belgium, French text)

Hennuy, Jean-Frederic Brown University 2004 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In today's world, national borders tend to become obsolete. Their porosity has grown so great that they no longer play their historic role as barriers. New concepts---globalization, multi-culturalism, trans-nationalism---are now definitions to describe the radical changes national borders undergo. Such changes put the concept of identity under question. The notion of identity is no longer univocal, it changes constantly in function of each individual's properties. Identity is now defined by its "plasticity," it has become a heterogenous concept in permanent evolution. Hierarchical bi-polarities like center-periphery, self-other, interior-exterior, subject-object, etc. are challenged by identities referring to multiple appurtenances. Therefore this study crosses borders at the same time it is a meeting point for Francophone literatures. The question of the relation to the Other and to oneself is omnipresent in every text studied forces to reconsider categories of identity such as language, history, territory and nationality. Jean-Philippe Toussaint and Abdelkebir Khatibi show that our travels are forcing us to adopt a diasporic identification process in order to draw a multi-dimensional identity card. Charles De Coster and Rejean Ducharme demonstrate that the singularity of our identity is also define by our re-appropriation of language. "Embabellir" the French language is not just an aesthetic project but aims to question its universality. Pierre Mertens and Assia Djebar writes historical palimpsests in order to show that collective identity is built through individual histories. And finally, second generation immigrant such as Saber Assal et Girolamo Santocono demonstrate that multi-cultural societies are non-menacing realities for a Belgian national identity but allow its redefinition. The study of these francophone writers allow us to experiment non only the difficulties of border crossing but also the suffering it can generate. It shows also that in our global world not all borders are disappearing, that some cultural borders remain and are sometimes reinforced.

From equivalence to equity: Myths of equality in American letters

Emerson, Amanda Marie Brown University 2004 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Texts written in the US between the Revolutionary and Civil wars construct the nation, "America," around an inwardly conflicted and socially contested myth of equality. This dissertation shows how that instability itself functioned as a means to unify the new nation. Chapter 1 explains the inheritance of ambiguous notions of equality from a British natural rights tradition and how those notions split in early America between conceptions of an idealistic equivalence (sameness) and a more pragmatic equity (impartially assigned difference). Chapter 2 observes how early Americans preserve a sense of themselves as defined by equality despite evidence to the contrary in the form of immigration, war, and disease. From Crevecoeur's homogeneous "competence" to the dangerous leveling of Charles Brockden Brown's 1790s Philadelphia: American texts register a change in emphasis in the national myth from equivalence to equity. Chapter 3 observes how the trend toward equity---an equality based on the presumption of difference---informs fictional Barbary captivity narratives by Royall Tyler and Susanna Rowson. These tales dramatize how all whites are equal in their inner proclivity for freedom. Proof of this collective equality depends on the erasure of the black slave and the displacement of slavery from North America to North Africa. The chapter ends with Leatherstocking's vernacular philosophy of gifts in James Fenimore Cooper's Deerslayer. Gifts name those natural endowments of color that distinguish "whites" and "reds" and, crucially, justify their living according to different but equal ethical imperatives. Chapter 4 describes how white women writers in the early to mid-nineteenth century confront excesses of equivalence and equity in the laws of coverture and in the discourse of "separate spheres." To imagine ideal womanhood as a multiple rather than a unitary possibility---and thus head off coverture---Catharine Sedgwick's Hope-Leslie looks backward to imagine ideal womanhood in several possible forms. Margaret Fuller's Woman in the Nineteenth Century opens the possibility that women might stand both inside and outside gender and anticipates the union of the myth of equality with a liberal ideal. Resilient in the face of contradiction, the myth of equality will continue to inform national self-image.

Numerical calculations of quantum field theories on the continuum

Emirdag, Pinar Brown University 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Source Galerkin technique is an alternative numerical method developed by Garcìa, Guralnik, and Lawson at Brown. It is not based on any statistical methods and has controllable errors. It also has the advantage that it can be used in a continuum formulation. This new method promises an increase in accuracy and speed of calculations. In this method, we treat field theory with the presence of external sources. The functional relations become a set of coupled differential equations for the generating functional <italic>Z</italic>. Source Galerkin is used to solve these equations for the Green's functions of the theory. According to this technique, the set of the residuals and the test functions are required to be orthogonal with respect to some inner product. The test functions that we are using are polynomials that consists of source terms and preserve the group symmetry of the problem. Symmetries of translation and reflection invariance are used in constructing the solution. A good choice of the test functions and the initial guess speeds the convergence to the result. The accuracy of the approximation can be judged by measuring its numerical stability and convergence. An exact solution can be obtained as the number of test functions increases. This sort of techniques for solving sets of differential equations are known as Galerkin methods. Application of this method to various field theories are investigated. Quantities such as mass gap and β function are calculated. The results are compared to the results in the literature.

"If sons, then heirs": A study of kinship and ethnicity in Paul's letters

Johnson Hodge, Caroline Elizabeth Brown University 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Christianity is widely understood to be a “universal” religion that transcends the particularities of history and culture, including differences related to kinship and ethnicity. In traditional Pauline scholarship, this portrait of Christianity has been justified by the letters of Paul. Interpreters claim that Paul eliminates ethnicity or at least separates it from what is important about Christianity. This study challenges that perception. Through a detailed examination of kinship and ethnic language in Paul's letters, I demonstrate that notions of peoplehood and lineage are not rejected or downplayed by Paul; instead they are central to his gospel. Paul's chief concern is the status of the gentile peoples who are alienated from the Judean God. Ethnicity defines this theological problem, just as it shapes his own evangelizing of the ethnic and religious “other.” According to Paul, God has responded to the gentile predicament through Christ, in whom non-Judeans can be made peoples of the Judean God. Using the logic of patrilineal descent, Paul constructs a myth of origins for gentiles: through baptism into Christ the gentiles become descendants of Abraham, adopted sons of God and coheirs with Christ. Although Judeans and gentiles now share a common ancestor, Paul does not collapse them into one group (of “Christians,” for example). Judeans and gentiles-in-Christ are separate but related lineages of Abraham. Many of Paul's contemporaries also reconstruct histories, lineages, and the collective myths of whole peoples. Kinship and ethnicity work well in these arguments, for at the same time that they present themselves as natural and fixed, they are also open to negotiation and reworking. This paradox renders them effective tools in organizing people and power, shaping self-understanding and defining membership. My analysis of kinship and ethnicity demonstrates that Paul's thinking is immersed in the story of a specific people and their God. He speaks not as a Christian theologian, but as a first-century Judean teacher of gentiles responding to concrete situations in the communities he founded. The salvation of Judeans and gentiles does not transcend notions of peoplehood and familial ties; rather, kinship and ethnicity serve as agents of this salvation.

Extending Grothendieck topologies to diagram categories and Serre functors on diagram schemes

Ulfarsson, Henning Arnor Brown University 2009 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

We study Serre functors and related constructions. A Serre functor on a triangulated category was defined by Bondal and Kapranov to be an auto-equivalence inducing certain natural dualities on homorphism sets in the category. In the special case of the bounded derived category of complexes of coherent sheaves on a smooth scheme Y the Serre functor is given by twisting by the dualizing sheaf and shifting by the dimension of the scheme. In the work of Lunts it is shown that a Serre functor exists if the scheme Y is replaced by a diagram scheme, which is a collection of schemes connected by morphisms; or more precisely a functor X : D → Schemes where D is some category, often called the shape of the diagram. We will give a description of the Serre functor for certain diagram schemes. Related to the description of the Serre functor for diagram schemes is the study of the category DiagSchemes of diagram schemes and how it inherits properties from the category of schemes. We will consider inheritance of Grothendieck topologies and construct a general method for diagrammatizing any topology in such a way that desirable properties are not lost in the process. We will then consider how to carry prestacks and stacks over along with a Grothendieck topology. A part of this work is joint with Jonathan Wise, at Stanford University.

Essentially Shimmering: Contemporary Poetics at the Edges of Materialism

Simon, Emily ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

prelude | what is essentially shimmeringEarly in her azure-saturated, poetic treatise Bluets, contemporary writer Maggie Nelson enumerates various ambient factors that are enmeshed with our perception of a seemingly self-contained and self-evident quality like color:Try, if you can, not to talk as if colors emanated from a single physical phenomenon. Keep in mind the effects of all the various surfaces, volumes, light-sources, films, expanses, degrees of solidity, solubility, temperature, elasticity, on color. Think of an object’s capacity to emit, reflect, absorb, transmit, or scatter light; think of “the operation of light on a feather.” Ask yourself, what is the color of a puddle? Is your blue sofa still blue when you stumble past it on your way to the kitchen for water in the middle of the night; is it still blue if you don’t get up, and no one enters the room to see it? (20).Nelson entreats readers to eschew our customary, facile sense of “color” as an isolable, singular, and determinate property of an object—what anthropologist Michael Taussig calls “the spot-of-color-on-the-page idea of color”—in favor of the illimitable “operation of light on a feather” or the indiscernible, inconstant hue of a “puddle” (249). Framed by these protean phenomena, “color” is evidently not something, but rather a luminous and ongoing effect, a processual coloring. And so, we recognize the impossibility of answering her question about the color of a puddle not only because we can pretty fairly say that a puddle (and which puddle?) does not have a single color—it may be bright blue or dark grey, shining silver or muddy brown—but because these different hues also indicate the way in which the quality of color more intimately constellates, and expresses, a welter of interlocking and shifting physical and perceptual factors. “What is the color of a puddle” also means: Is the puddle cloudy or translucent? Gleaming or matte? Shallow or deep? Surface tension, the weather, temperature, shade all converge and conspire in the articulation of this momentary tone.Such a luminously imbricated vision of color makes it hard to say for certain what, exactly, the color in question is. Later in this same section of Bluets, Nelson frames the historical development of chromatic schema (color wheels, palettes, etc) as a retroactive effort to resolve this constitutive undecidability: to make sense, she writes, out “of what is essentially shimmering” (20). In this particular instance, “what is essentially shimmering” refers the way that colors cannot be stabilized into a singular, ineluctable hue (like blue), but are rather perpetually gradated by variations in all of the different factors that Nelson lists (light, solidity, texture, perspective). At the same time, the case of color gestures to a more general indistinction between the physical and the phenomenal that animates the poetry and thought around which my dissertation revolves. This indistinction is what is encompassed by the gorgeously paradoxical notion of the “essentially shimmering,” or the sense in which the materiality of a thing (and especially of a surface) is inextricably bound up with and modulated by fluctuations in time and perception. Nelson’s formulation of this dynamic claims as an intrinsic, perdurable attribute (the “essential”) a phenomenon that is contingent, superficial, and mercurial (“shimmering”). That is, to be essentially shimmering is to exist at the uneasy or impossible intersection of a received distinction between a thing’s material reality or facticity and what would seem to be its mere appearance, those transient sensations interposed by the film of subjectivity or passing angles of light.1 It insinuates a materialism that at the same time verges on the immaterial.

Investigations of the effects of impact shock, water and oxidation on SNC (Martian) meteorites, magma petrogenesis and spectral properties

Minitti, Michelle Elaine Brown University 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The research contained in this thesis utilizes data from planetary missions and from the SNC (<bold>S</bold>hergotty-<bold>N</bold>akhla-<bold> C</bold>hassigny) meteorites to answer questions about igneous processes on Mars. Two broad themes encompass the chapters: (1) investigation of the amount and role of water in Martian magmas; and (2) exploration of connections between chemical and mineralogical data from planetary missions and the SNC meteorites. The potential amount of water was investigated indirectly by studying the effects of impact shock on water loss and H isotope fractionation in hornblende. Combined results from petrography, water extraction and mass spectrometry analyses of unshocked and shocked hornblende suggest that impact shock potentially leads to losses of ∼1 wt% H₂O and H isotopic fractionations of ΔD ≈ +100‰. This finding implies that impact shock was an important factor in establishing the low water contents and H isotopic character of the SNC kaersutites. The role of water was investigated more directly by studying the effect of water on the crystallization of a SNC basalt, with the goal of understanding the origin of the andesitic “sulfur-free” rock composition established from measurements at the Mars Pathfinder landing site. We determined that water (1–1.5 wt% H₂O) is required in the formation of the sulfur-free rock from a SNC parental basalt and that water facilitates extraction of such andesitic liquids. Further connections between the SNC meteorites and planetary mission data were investigated by establishing the effects of glass content and oxidation on spectra of SNC basalt compositions. We then determined if SNC basalt spectra affected by one or both of these factors could reproduce Mars remote sensing data. We found that the relative amounts of glass, pyroxene and plagioclase that change with crystallinity lead to progressive changes in spectral character of SNC basalts at both visible and near-infrared (VISNIR) and mid-infrared (mid-IR) wavelengths. We also determined that oxidation products, largely hematite, alter the spectral character of SNC basalts in the VISNIR and mid-IR and that the combined effects of oxidation and glass content produce SNC basalt spectra with characteristics resembling Martian spectra at VISNIR and mid-IR wavelengths.

A deposed elite and the issue of responsibility: How Communist-era politicians are coping with their reputation as perpetrators in Leipzig, Germany

Touval, Amitai Brown University 2000 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The goal of my fieldwork in Leipzig was to determine how former East German politicians are coping with their politically-tainted past. Regardless of whether they are responsible for any past abuses, East German politicians are widely suspected of having had close contact with the Stasi, or secret police. The Stasi represents all that was wrong in East Germany: stringent travel restrictions, political repression and a poor consumer market. The case of ex-politicians is an opportunity to explore how members of a deposed elite relate to the issue of responsibility. Do they see themselves as responsible for past abuses or only for past successes? And what does their sense of responsibility teaches us about their sense of self, and more broadly, German identity?. I argue that ex-politicians are in a double-bind. They distance themselves from the tainted past while striving to affirm their socialist ideals. I explore how they invoke sentiments of estrangement and identification across different spheres of life, including their relationships with former colleagues, career prospects and opinions about German unification. I then contend that their struggles with the tainted past are paradigmatic of the identity struggles of their compatriots. German identity is no longer symbolized exclusively with reference to the figure of the victim (in West Germany) or the resistance fighter (in East Germany). Daniel Goldhagen's <italic>Hitler's Willing Executioners </italic> has struck a chord in Germany precisely because it resonates with this shift in national identity. Rather than suppress the presence of the perpetrator in society, as was the case in the aftermath of World War II, accomplices to evil are presumed to be present in large numbers in Eastern Germany.