Drivers of understory plant diversity and composition in managed temperate second-growth forests

Duguid, Marlyse Corallo ProQuest Dissertations & Theses Yale University 2016 해외박사(DDOD)

Large forest areas across eastern North America---and increasingly the world---are second-growth, arising after agricultural abandonment or other intense land-uses. In addition, many of these second-growth forests are actively managed for timber. Unfortunately, the long-term consequences of this agricultural legacy, combined with the additional effects of subsequent forest harvesting on plant diversity and composition are unknown. The majority of plant diversity in these forests is found in the understory, and its structure and composition directly influences ecosystem function, animal diversity, and forest development. There is an increasing acceptance of the importance of this stratum for conservation and forest management. Understanding how forest understories vary across topographic and soil types and how site conditions interact with forest harvesting effects and other land-use is critical to biodiversity conservation in these second-growth forests. My dissertation work examines understory plant community response to human land use through a series of analytic, observational, and manipulative experiments at varying scales. In Chapter 1, I used meta-analysis to test for overall effects and temporal patterns of understory species richness in response to forest harvesting across the entire temperate forest biome and found that no consistent effect of forest harvesting on understory plant species richness. The analysis supported the importance of site and harvest specific characteristics in defining understory plant diversity response to forest harvesting. In Chapters 2 and 3, I examined the relative importance of these site and harvest specific characteristics on understory community response following forest harvesting. By tracking understory plant communities for 15 years following forest harvesting across a series of experimental linear gaps, I was able to isolate the relative importance of gap position (light), ground-disturbance, and site quality on understory diversity and compositional patterns following forest harvesting. Again, results highlighted site specific responses to forest harvesting. Individual soil types retained compositional difference following forest harvesting and showed varying temporal capacity to recover. In Chapter 4, I conducted an observational study across a varied physiographic, soil and disturbance landscape to explore patterns of herb layer diversity and identify the most important environmental drivers influencing herb-layer diversity and compositional patterns in a second-growth managed forest in southern New England. I conducted a survey of vascular plants using 420 fixed area plots across the 3213-hectare Yale-Myers forest and paired the floristic data with over 20 direct environmental measurements. I found that managed second-growth forests can house a significant amount of understory plant diversity, and that patterns are driven more by niche partitioning than dispersal limitation. Edaphic factors were the most influential on species diversity and composition, but environmental controls had greater explanatory power on species richness than composition. In my final Chapter 5, I explore the unmeasured drivers of understory plant composition. A qualitative review of the biotic interactions between woodland herbs and other organisms, I show that these relationships and interactions have the potential to act as strongly as niche factors as commonly measured abiotic factors. Further, that the actions and populations of these biotic drivers may covary with abiotic resource gradients confounding our understanding of the drivers of these understory plant communities. My dissertation demonstrates the importance of site-specific variables in driving understory plant community dynamics, an assumption commonly encountered in the literature. Further, it highlights important avenues for future research, specifically the interaction between biotic and abiotic variables in driving temperate forest diversity patterns.

Elucidating the Mechanisms of Water and Ion Transport Under Nanoconfinement

Ritt, Cody L ProQuest Dissertations & Theses Yale University 2022 해외박사(DDOD)

Water scarcity is among the most prominent humanitarian crises of our time. Achieving equitable access to safe drinking water for all humankind necessitates the treatment of unconventional and underutilized sources. Pressure-driven desalination technologies are particularly well-suited for augmenting global water supplies due to their energy efficiency. In these technologies, the membrane is the critical component driving process efficacy and requires material breakthroughs to achieve paradigm-shifting performance.Attempts to improve conventional membrane materials and investigations into numerous novel materials have failed to produce the next generation of desalination membranes due to our limited understanding of the mechanisms that govern water and ion transport under nanoconfinement. Hence, the objective of this dissertation research is to elucidate fundamental synthesis–structure–performance relationships in conventional- and novel-material based membranes, in the context of how these relationships can be exploited to improve practical water treatment processes.Electrostatic interactions between the membrane and charged constituents in the feed water are central to membrane performance. These interactions depend on the extent to which the membrane is charged, yet the reasoning behind the ionization behavior of state-of-the-art polymers used for desalination has been unknown for years. This dissertation unravels the anomalous ionization behavior of nanoporous polyamide, revealing that a large portion of the ionizable moieties in polyamide films remain uncharged, and thus, unutilized, during typical operation due to extreme confinement effects. Several approaches to exploit these ionizable groups for improved performance are highlighted. Electrostatic interactions may also depend on the physicochemical characteristics of the charged constituents in solution, such as the molecular shape of ions. To help guide the development of ion-ion selective membranes, this work utilizes machine learning to assess molecular-level features that influence ion transport in nanoporous cellulose acetate membranes. The findings suggest that attention should be redirected from the ion’s bulk solvation properties to their intrinsic electrical properties for selective separations. Ion-specific adsorption reactions can also dictate the effective pore charge through charge regulation. Cation-specific transport in charged nanochannels is thus rationalized from a charge regulation perspective, representing the phenomenon as an adsorption equilibrium process. This approach enables the use of conductance measurements to indirectly probe ion-surface reactions within the nanochannels—previously inaccessible experimentally.The role of defects in novel material-based membranes, which is frequently overlooked, are identified in this dissertation. This work focuses primarily on framework defects found in two-dimensional (2D) materials. The overlapping of framework defects are found to create percolation networks that greatly hinder the separation performance of 2D lamellar membranes. It is therefore emphasized that the mitigation of defects in novel material-based membranes is imperative to achieve practically viable desalination membranes that can compete with materials already commercially available. If unavoidable, the impact of defects in 2D material-based membranes on membrane performance can be masked if the water permeability remains high for thick membranes. This would require significant slip flow through the nanochannels, a phenomenon that can be experimentally resolved by the nanofluidic devices developed in this work. An interferometry-based apparatus is also designed to enable measurement of the ultralow flow rates (~few nL h-1) that are expected from these nanochannels.Overall, this dissertation investigates transport phenomena unique to extremely confined environments that are relevant to real-world water purification technologies. Electrostatic interactions between ions and the membrane are shown to be highly important for selective separations in conventional materials, and can even go as far as to influence the intrinsic charge of the membrane. For novel materials, fabrication-induced defects critically limit their future implementation in desalination technologies, making precisely controlled nanofluidic platforms essential for understanding defect-free transport within these frameworks. This dissertation demonstrates new approaches to studying nanoconfined transport and provides insight that may lead to next-generation membranes for desalination and water purification.

The Church's Book: Theology of Scripture in Ecclesial Context in the Work of John Howard Yoder, Robert Jenson, and John Webster

East, Bradley Raymond ProQuest Dissertations & Theses Yale University 2017 해외박사(DDOD)

Theological interpretation of Scripture has been ascendant in recent decades, and theologians and biblical scholars from a variety of backgrounds, areas of expertise, and ecclesial commitments have rallied around it. Increasingly, however, divisions are fraying the heretofore united front against historical criticism's dominance in academic biblical interpretation. This dissertation is an exploration of the reasons for these divisions. Its motivating thesis is that differences in ecclesiology lie behind disagreements about bibliology, which manifest in turn as divergences over theological interpretation. Prior to and operative within judgments about the nature, authority, and interpretation of the Bible stand judgments about the being, mission, and authority of the church. But the relationship between the two is not so linear as that. For the connections between them are direct and materially operative, and only more so when they remain implicit and therefore unexamined. Every account of the Bible both assumes and implies an account of the church, and vice versa: the lines of influence are reciprocal and circular. The Bible is always the church's book, the church always the community under the Bible's authority. This dissertation responds, diagnostically and constructively, to this situation through engagement with particular figures. Specifically, it expounds one specific strand of bibliology influenced by the great Protestant theologian Karl Barth: the work, respectively, of John Howard Yoder, Robert Jenson, and John Webster. Each of these theologians is a contemporary Barthian of a sort, a student but not a disciple of the Swiss master. Given Barth's influence over the development of theological interpretation, this commonality is helpful both genetically (all three trace their thought to the--proximate--source) and substantively (their proposals share enough to make disagreement intelligible, and interesting). Moreover, Jenson, Webster, and Yoder represent, between them, the three great traditions of western Christendom: catholicism, the magisterial reformation, and the radical reformation. The specific ways in which their ecclesial commitments shape, inform, and at times determine their theological treatments of Scripture provide ideal examples of the phenomenon at issue in this dissertation. Across five chapters, the project's principal aim is to demonstrate as well as examine the inseparable relationship between theology of Scripture and theology of the church. Along the way, the positions and proposals represented by Yoder, Jenson, and 'Webster come to light, and critical analysis of each highlights their respective strengths and shortcomings. In fulfilling these tasks the dissertation serves both as an initial reception of these theologians' bibliologies and as a critique of a feature--at times a problem--endemic to the current renewal of theological interpretation of Scripture.

Paleoenvironmental Context of Early Stone Age Archaeology: An Analysis of the Gona Fauna Between ~3 and 1 Ma

Leiss, Amanda Christie ProQuest Dissertations & Theses Yale University 2022 해외박사(DDOD)

The advent of tool-making has long been associated with expanding grasslands in Africa. My dissertation reconstructs paleoenvironments at Gona, in the Afar region of Ethiopia, between ~3–1 Ma (1) to make inferences about how hominins were utilizing the paleo-landscape and interacting with mammalian communities and (2) to investigate whether the environment was influential in the development of stone tools. This time period spans the origin of our genus Homo and the evolution of Homo erectus, and it provides evidence of increased behavioral complexity (stone tools), brain expansion, and the acquisition of large nutrient-rich food sources (animal carcasses). Because of the scarcity of fossil and artifact-bearing deposits, little is known about the paleoenvironment during this time. There is an opportunity to address this at Gona, with its long record of Early Stone Age (ESA) archaeology, including among the earliest stone tools (Oldowan), evidence of carcass processing at ~2.6 Ma, and early Acheulean assemblages at 1.7 Ma. The emergence of the Acheulean is noteworthy for the standardized and purposeful technique which required a preconception of form (Semaw et al., 2009). Mammalian fossils throughout this sequence that are relatively understudied have the potential to help interpret the context in which these anatomical and behavioral changes occurred, specifically between ~3–1 Ma.I collected bovid tribal abundance, ecomorphological, and stable isotope data to reconstruct habitats throughout four intervals and analyzed them temporally and spatially in association with stone tools. As part of the Gona Research Project, my study complements and contributes to ongoing taphonomic, lithic, and geologic studies to provide a significant contribution to better understand the origin and evolution of stone tool technology. Tool use is a key innovation linked to behavioral and cognitive advances that led to the evolution of our species.The first chapter introduces the central concepts and explains the dissertation format. Chapter 2 provides the geological, paleontological, and archaeological context for the fossil and archaeological localities included in this dissertation. I discuss the research design used in this dissertation and place these localities into four temporally constrained study intervals or units that range from 2.96 to 0.81 Ma, spanning the emergence of Acheulean technology at Gona. Chapter 3 reports new stable carbon and oxygen isotope enamel values from large herbivores. I reconstruct faunal diets through analyses of δ13Cenamel from fossil assemblages of paleontological and archaeological contexts and then compare them to a large dataset of published stable carbon isotopes from enamel and pedogenic carbonates from eastern Africa to place my observations at Gona in a regional framework. Using community assemblage data and the proportion of grazers (as indicated by taxa with high δ13Cenamel values), I find that the habitats at Gona had more C4 grassy resources between ~3-1 Ma than all other contemporaneous fossil and archaeological localities in eastern Africa. Statistically significant increases in carbon values in the Lower Acheulean study interval provide further evidence for increased exploitation of grassy habitats.Alcelaphini bovids in particular are significantly enriched in δ13Cenamel values in archaeological contexts compared to paleontological contexts during the Lower Acheulean study interval. Alcelaphini from archaeological contexts in the Lower Acheulean study interval are also significantly enriched in δ13Cenamel compared to Alcelaphini from archaeological contexts in the Oldowan study interval. Chapter 4 presents the results of my bovid ecomorphological analyses of multiple elements and bovid tribal abundances. I find more open ecomorphs and Alcelaphini bovids in archaeological compared to paleontological contexts suggesting an increased reliance on open environments during the Lower Acheulean study interval. These data demonstrate an increase in open settings at the emergence of the Acheulean and a long-term increase in edaphic grasslands at Gona, with a marked increase at ~1.26 Ma. Chapter 5 summarizes the conclusions of this study and the implications for hominin behavior. These new data from Gona fill a significant gap in the eastern African Plio-Pleistocene paleoenvironmental record. I provide a nearly continuous sequence of paleoenvironmental and behavioral land use patterns by early Homo during the Early Stone Age. Overall, this study supports the hypothesis that the Acheulean technology was an adaptation to increased grasslands in eastern Africa.

The Avant-Garde of Feeling: Queer Love and Modernism

Abraham, Michael Yale University ProQuest Dissertations & Theses 2023 해외박사(DDOD)

This dissertation reads the lives and works of Gertrude Stein, Alice B. Toklas, H.D., Bryher, and Langston Hughes to understand love's potential for queer flourishing for American subjects in the pre-Stonewall era. Through readings of literature that run the gamut of genre from memoirs to poetry, novels to cookbooks, it teases out what love means to each of these authors and explores their orientations toward cisheteronormative constructions of kinship in twentieth-century America and Europe, while they resist, recontextualize, and sometimes capitulate to the complex of forces that constitutes normativity.The last three decades have generated manifold theorizations of queer desire, but very little writing addresses the issue of queer love, and a significant body of literature exists that situates love squarely within the bourgeois project of modern normative kinship formation. This dissertation contests that thesis. The introduction theorizes love as a resource for identificatory and relational experimentation, drawing upon the work of Simone Weil, Luce Irigaray, and bell hooks. Love is a curious phenomenological suspension of force that occurs in an intersubjective moment of maximal identificatory and relational fecundity and provides the possibility of new scripts for identification and relation. The introduction posits the possibility that love is a queer resource available to everyone, not merely to those people whom we identify as queer.Chapter One investigates the centrality of the domestic to Stein's and Toklas's conceptualizations of both love and queerness, arguing that their famous home at 27 rue de Fleurus provided the material conditions of possibility for their experimentations with gender and sexuality and their relationship to one another, which they considered a marriage. Their Saturday night salon was also a testing ground for the development of queer expatriate American identity generally, allowing for the flourishing of many others. Chapter Two on H.D. and Bryher formulates love as a transcendence of the epistemological boundaries of the modern empirical frame. Focusing on the importance of their occult work to their relationship, the chapter studies the way their experimentation with ulterior forms of knowledge-production opens up the possibility of experiment with ulterior genders, sexualities, and intimate configurations. Chapter Three on Hughes explores the queerness of being a bachelor and of being closeted, arguing that Hughes looked to literature to find avenues for intimacy he did not have in his relational life. Hughes's writing animates Harlem in such a way as to afford him intimate knowledge of the figures within his neighborhood, situating him as lover and beloved to the entire community. In his poetry for children, Hughes enacts a kind of family-making-in-text, an effort to adopt Black children across the country into his vision of what love is and means. The coda argues that the queer lifeworld of modernism must be understood as an inconvenient mix of contradictory desires and positionings, rather than a reflection of contemporary queer subjects.

EFTs for Nearly Conformal Gauge Theories

Ingoldby, James ProQuest Dissertations & Theses Yale University 2019 해외박사(DDOD)

The phenomena of electricity and magnetism, beta decay in radioactive nuclei, and the confinement of quarks within the proton can each be explained using the three different gauge theories which collectively make up the standard model. Alternative gauge theories display new kinds of exotic phenomena, which are not fully understood. For example, if the field content is chosen appropriately, a non-abelian gauge theory is said to lie inside the conformal window, and can acquire a conformal symmetry when its coupling parameter takes a specific value. In this case, all fundamental mass scales vanish from the theory and its states no longer strictly correspond to collections of particles. This thesis focuses on nearly conformal gauge theories, which have a field content chosen to place them just outside of the conformal window. They exhibit confinement at low energies, but numerical studies indicate that their properties differ markedly from the familiar gauge theories of the standard model. In particular, an anomalously light composite scalar forms in these theories, which could be interpreted as a candidate Higgs boson that would resolve the standard model hierarchy problem.Revealing the variety of phenomena exhibited by nearly conformal gauge theories is challenging because these theories confine, are strongly coupled and therefore cannot be analyzed using the standard tools of perturbation theory. Lattice gauge theory has been used to study these theories numerically. These studies have revealed a wealth of useful information about the nearly conformal gauge theories, including properties of the spectrum of composite states, but they required significant computer resources, so having complimentary theoretical tools is advantageous.To this end, two effective field theories (EFTs) are developed in this thesis: A dilaton EFT in which the lightest scalar state is interpreted as a pseudo--Goldstone boson arising from the spontaneous breaking of conformal symmetry, and a linear sigma EFT, in which the lightest scalar belongs to a multiplet of states transforming linearly under an internal symmetry. These weakly coupled EFTs include only the lightest degrees of freedom present in the spectrum of the gauge theories and provide a simple, approximate description of the same physics, enabling extrapolation of the lattice results to regions of parameter space that are otherwise inaccessible. The dilaton EFT is fitted to lattice data with encouraging results.

The Fragmented Gateway to Collective Repentance: Race, Policing, and the Black Church in America

Denney, Matthew G. T Yale University ProQuest Dissertations & Theses 2023 해외박사(DDOD)

This dissertation examines the response of Black faith communities to policing and racial inequality in America. I explore the puzzle of why policing has compelled unique levels of mass mobilization for racial justice among Black faith communities, despite significant disagreement, while other areas of entrenched inequality have not received the same level of attention, despite more widespread agreement. This project draws on historical-archival research, ethnographic work based in New Haven, focus group interviews with Black faith leaders from around the country, and a large national survey to provide a holistic picture of the role of Black faith communities in conversations around policing and racial inequality.Part 1 (chapters 1-2) provides an overview of theory to understand race, policing, and the Black Church: policing as a fragmented gateway to collective repentance. In this framework, racial violence compels mobilization around policing and serves as a gateway through which Black faith communities call for collective repentance, which includes acknowledging histories of racial sins, stopping injustice, and seeking repair from the harms done. Racial violence serves this role because it provides visible displays of injustice and contestable targets in the form of policing. But mobilization around policing becomes fragmented due to internal debates about defunding the police, external resistance to broader racial justice, and religious-political cross pressures. Chapter 1 provides the background, method, and overview. Chapter 2 describes each core component of the argument, with representative evidence from focus group interviews and survey data.Part 2 (chapters 3-4) situates this framework in historical perspective and anchors the voices of contemporary Black faith communities to the Black prophetic tradition. This section does this by providing a historical case study from 1933 to 1945. Chapter 3 provides an analysis of how critical changes in policing during this time set policing on development trajectories and further ingrained racial inequalities. At the same time, Black faith communities offered alternative visions grounded in protecting vulnerable Americans and addressing socioeconomic inequality. This time period both exacerbated inequalities whose sources would be submerged over time, and it also constrained the ability of policing to serve as an agent for bringing socioeconomic inequality.Part 3 provides three contemporary case studies of approaches by faith communities to policing, entitled Reform, Representation and Relationships, and Resistance. I argue that all of these pathways involve Black faith communities who are working toward expansive visions of racial justice that mirror the key tenets of collective repentance. At the same, all of these approaches face significant structural and internal constraints that produce fragmentation. The Reform chapter follows a campaign by a Faith-Based Community Organization in Connecticut to automatically expunge some criminal records in Connecticut. The Representation chapter traces the role of Black faith leaders in influencing the New Haven Police Department through positions of leadership and brokerage relationships. The Resistance chapter draws on examples from around the country to analyze the role of Black faith communities during the George Floyd protest wave in 2020. I argue that, contrary to common wisdom, the Black Church has not experienced a unilateral decline in its role in mass resistance. Rather, it has experienced stability in some areas and decline in others. Specifically, I argue that the Black Church retains the most important pastoral role in mass resistance around racial justice. The prophetic role remains strong as well, but it has experienced some decline. Most significantly, the Black Church has experienced a precipitous decline in organizational strength, and this exerts a downward pressure on its prophetic capacity. Despite the obstacles in each of these pathways, the Black Church still provides a critique of American racism and a holistic vision of racial justice.The conclusion brings together the different themes from the dissertation: the historical developments, the different approaches to policing, and the difficulty of achieving socioeconomic equality. I highlight another approach that has become common since 2020: task forces to reimagine policing. Black faith leaders on these task forces connect policing to fundamental racial inequalities, but they experience resistance and fragmentation. Drawing on the whole of my research and the voices of Black churches and Christians, I describe a vision for reimagining repentance that starts from a posture of repentance, then moves into domains of entrenched inequality.

A Light in the Dark: Ultralight Dark Matter Phenomenology in Simulations

Zagorac, Jovana ProQuest Dissertations & Theses Yale University 2022 해외박사(DDOD)

Of the outstanding problems in astronomy, the nature of dark matter is certainly one of the most mysterious. Containing five times more energy density than its luminous counterpart, dark matter has been shaping the large-scale structure of our Universe for billions of years. The expansion of accessible and accurate cosmological simulations has revolutionized how we visualize the imprint of dark matter in the structure of our Universe. In my Ph.D., I contributed to this revolution through the development and implementation of a new code, chplUltra: a parallel, portable, and efficient tool for HPC simulations of a promising dark matter candidate, Fuzzy or UltraLight Dark Matter (ULDM). ULDM is a well-motivated axion-like dark matter candidate whose incredibly small mass results in naturally cored profiles, thus ameliorating many of the small-scale problems of cold dark matter (CDM) while maintaining the same robust large-scale results. When unperturbed, the lowest energy solution of the ULDM system is a spherical “soliton” structure with a known mass density profile. A ULDM dark matter halo is formed through collisions of these solitons and has two characteristic parts: a central soliton core, and an ``skirt" surrounding it. In order to investigate ULDM dynamics, I calculated the full spectrum of eigenstates for ULDM systems with approximately stationary potentials, thus allowing me to 1) link qualitative behavior of soliton cores in ULDM simulations with superpositions of specific modes and 2) decompose CHPLULTRA simulations of ULDM halos into individual eigenstates. Using this formalism, I investigated the formation of halos through soliton collisions and the dependence of the final halo product on initial parameters. Crucially, this allowed me to explore how halo cores form and explain discrepancies in the literature surrounding the core-halo mass relation: a key prediction of ULDM. I was also able to comment on the composition of the halos' skirts, including their qualitative behavior and eigenstate makeup, as a function of initial binary parameters. Finally, I sketched out some of the exciting future directions for understanding ULDM through the language of its eigenstates; these include combining my work on ULDM with my previous work on primordial black holes, which is included as part of this dissertation.

The Problem of Discretion: Defining the Power of Judges and Prosecutors

Fish, Eric Studebaker ProQuest Dissertations & Theses Yale University 2017 해외박사(DDOD)

This dissertation focuses on the problem of discretion. It explores the various ways that discretionary decisions can be structured so that they will advance the principles that animate a particular system of law. If individual actors have too much discretion. then they can substitute their own values for those of the system. If individual actors have too little discretion. then they will not be able to make decisions that preserve important system values. This dissertation explores different strategies for expanding, taming, and rationalizing such discretion. There are two main strands to this dissertation. each of which deals with the problem of discretion in a different area of law. The first two chapters focus on the American law of constitutional remedies. The remaining two chapters focus on the American criminal justice system. Chapter 1. "Choosing Constitutional Remedies," considers what judges should do in situations where there is more than one way to fix an unconstitutional statute. I argue that there are two different approaches. One approach. "Editorial Restraint," holds that judges should assume as little power to change legislation as possible. It posits a sliding scale of judicial interventions---adding language to a statute is worse than striking down language. which is worse than striking down an application. which is worse than adopting an avoidance interpretation. The other approach, 'Purpose Preservation," focuses instead on finding whatever remedy best preserves the legislature's goals. I show how the American doctrine of constitutional remedies sometimes follows the logic of Editorial Restraint, and sometimes the logic of Purpose Preservation, and I ultimately defend Purpose Preservation as the superior approach. Chapter 2. "Constitutional Avoidance as Interpretation and as Remedy," provides a new take on the avoidance canon. I argue that constitutional avoidance should be bifurcated into two different judicial tools: (I) a canon of construction, and (2) a remedy that changes the meaning of unconstitutional statutes. The latter of these avoidance as a constitutional remedy---justifies courts' power to effectively rewrite statutes through avoidance interpretations. A court that finds a statute unconstitutional can creatively 'reinterpret' that statute in a way that changes its meaning in order to fix the constitutional violation. just as a court can strike down statutory language. strike down applications, and impose other remedies that change the statutes meaning. Chapter 3. "Sentencing and lnterbranch Dialogue." considers the problem of how judges' sentencing discretion can coexist with formal sentencing guideline systems. The basic conflict is between individualization and uniformity. As a general matter. sentences decided by judges will be individualized but not uniform. and sentences decided by guideline planners will be uniform but not individualized. I argue that we should transcend this dichotomy between judicial and guideline sentencing, and design sentencing systems around the principle of dialogue between judges and guideline planners. The basic idea is that sentencing guidelines should periodically he updated to reflect judges' actual sentencing practices. while at the same time judges sentencing practices should adapt to fit the guidelines. Such dialogue can take place through a variety of institutional forms, including both advisory and presumptive guideline systems. Chapter 4. "Prosecutorial Constitutionalism," argues that prosecutors have an obligation to use their discretion to preserve defendants' constitutional rights even in situations where judicial doctrine does not require doing so. The sources of this obligation are twofold: the professional ethical duty to "do justice." and the departmentalist duty to independently interpret and enforce the Constitution. The difficult question is how to balance this obligation against prosecutors` role as adversary advocates for conviction. I argue that prosecutors should step away from their adversary role and become quasi-judicial enforcers of constitutional rights in situations where the adversary system fails defendants. This happens. for example, when prosecutors unilaterally control the relevant right (e.g., during plea bargaining negotiations or grand jury proceedings), and when judges cannot adequately enforce the relevant right because judicial remedies are retrospective and incomplete (e.g.. when exculpatory evidence is not revealed to the defendant or when defense counsel is inadequate).

Pushing the Frontiers of Non-Equilibrium Dynamics of Collisionless and Weakly Collisional Self-Gravitating Systems

Banik, Uddipan Yale University ProQuest Dissertations & Theses 2023 해외박사(DDOD)

In the ΛCDM paradigm of cosmology, structure formation occurs via gravitational encounters and mergers between self-gravitating structures like galaxies and dark matter halos. This perturbs galaxies and halos out of equilibrium. These systems are collisionless, i.e., cannot relax within the Hubble time via two-body encounters, thereby prevailing in a state of non-equilibrium or quasi-equilibrium at best. However, such perturbed collisionless systems can relax via other mechanisms such as phase-mixing, Landau damping and violent relaxation. Phase-mixing and Landau damping take several dynamical times to achieve completion. Both these processes can be described using a linear order perturbation of the collisionless Boltzmann and Poisson equations under the assumption of a sufficiently weak perturbation. Phase-mixing is the coarse-grained destruction of a coherent response to a perturbation due to an intrinsic spread in the oscillation frequencies of the field particles. Landau damping is the fine-grained damping of the response due to energy exchanges driven by gravitational interactions between the particles, which is also known as a collective effect. Unlike the linear phenomena of phase-mixing and Landau damping, violent relaxation is fundamentally a non-linear effect and is a rapid process, achieving completion within a dynamical time. Moreover, violent relaxation is self-limiting in nature, rendering an end state that may be very different from the Maxwellian velocity distribution that ensues from two-body/collisional relaxation. While a perturbed collisionless system (subject) undergoes relaxation via the above processes, the subject response simultaneously exerts a back reaction on the perturber and slowly changes its orbital dynamics, typically draining its orbital energy and angular momentum. This phenomenon is a type of secular evolution and is known as dynamical friction. It is the key process by which the relative orbital energy of interacting galaxies and halos is dumped into their internal energies, often resulting in their merger. Gravitational encounters and dynamical friction are therefore at the basis of all structure formation in the universe.Depending on how the timescale of perturbation (τP) compares to the oscillation periods (τ ) of field particles in the subject, gravitational perturbations can be impulsive (τP τ ). This dissertation investigates how gravitational encounters and collisionless relaxation occur in these three different regimes. First, we provide a general non-perturbative formalism to compute the energy change in impulsive encounters, which properly describes penetrating encounters, unlike the standard approach that only works for distant encounters. Next, we develop a comprehensive linear perturbative formalism to compute the response of a stellar disk to external perturbations. We study the cases of an infinite isothermal slab as well as a realistic disk galaxy in a non-responsive dark matter halo. The disk response phase-mixes away due to different oscillation frequencies of the stars, giving rise to local phase-space spirals. A vertically anti-symmetric (symmetric) perturbation gives rise to a bending (breathing) mode response of the disk, which triggers a one-armed (two-armed) spiral in the z − vz phase-space. Perturbations slower than the vertical oscillation period (τz), i.e., those with τP > τz, induce stronger bending modes, while faster ones trigger more pronounced breathing modes. This translates to more distant encounters with satellite galaxies causing stronger bending mode perturbations. We analyze the response of the Milky Way (MW) disk to encounters with its satellite galaxies, and find that Sagittarius (Sgr) dominates the Solar neighborhood response among all the satellites. This makes Sgr the dominant contender among the MW satellites to have triggered the Gaia phase spiral. Collisional diffusion due to the scattering of disk stars by structures like giant molecular clouds can result in a super-exponential damping of the phase spiral amplitude on a fine-grained level. The diffusion timescale in the Solar neighborhood of the MW disk turns out to be τ⊙D ∼ 0.6 − 0.7 Gyr. This sets an approximate upper limit of τ⊙D to the time elapsed since perturbation so that the resultant Solar neighborhood phase spiral survives collisional damping and is detectable. Only sufficiently impulsive perturbations can trigger phase spirals; adiabatic ones cannot. Near-resonant parts of the phase-space undergo gradual phase-mixing and do not develop phase spirals. It is the near-resonant response of the subject that exerts the maximum torque on the perturber, driving its orbital inspiral via dynamical friction.In the final chapters of this dissertation, we develop a general theory for dynamical friction on a perturber in circular orbit in a spherical host galaxy. This explains the origin of secular phenomena in N-body simulations of cored galaxies that are unexplained in the standard Chandrasekhar and resonance theories for dynamical friction: (i) corestalling, the apparent cessation of dynamical friction driven infall in the core region of galaxies with a central constant density core, (ii) super-Chandrasekhar friction, an accelerated infall phase prior to core-stalling, and (iii) dynamical buoyancy, an enhancing torque that can counteract dynamical friction and push out the perturber from inside the core region. We relax the adiabatic and secular approximations adopted in the derivation of the LBK torque in the standard resonance theory, and provide a fully selfconsistent perturbative formalism for dynamical friction. The LBK torque depends on the current orbital radius of the perturber, arises exclusively from resonances between the field particles and the perturber, and is always retarding. On the contrary, the selfconsistent torque depends on the entire infall history of the perturber (memory effect), has a significant contribution from the near-resonant orbits, and flips sign within a certain radius in the core region, becoming enhancing instead of retarding. To overcome the limitations of linear perturbation theory near the core-stalling radius, we develop a novel, non-perturbative, orbit-based treatment of dynamical friction. Here we model dynamical friction as a circular restricted three body problem, wherein we identify the near-co-rotation resonant horse-shoe, Pac-Man and tadpole orbits of field particles as the dominant contributors to dynamical friction or buoyancy. Outside the core region, all these orbits exert friction. As the perturber enters the core region, it tidally disrupts the core and the inner Lagrange points undergo a bifurcation. This drastically alters the orbital topology: the friction exerting horse-shoe orbits disappear and the Pac-Man orbits become dominant. A shallow distribution function gradient along these Pac-Man orbits gives rise to an enhancing torque or dynamical buoyancy in the core region. We argue that core-stalling occurs near the radius of Lagrange point bifurcation, which marks the transition from friction to buoyancy. Bifurcation of Lagrange points and therefore core-stalling are exclusive to a galaxy with a constant density core and are absent in one with a central NFW-like cusp. We discuss some profound astrophysical implications of core-stalling and buoyancy, e.g., the potential choking of supermassive black hole (SMBH) mergers in cored galaxies, leading to a significant population of offcenter, wandering SMBHs. This has implications for future detections of gravitational wave events due to SMBH mergers by Laser Interferometer Space Antenna (LISA).