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Strong-to-Weak Spontaneous Symmetry Breaking in Mixed Quantum States
Get PDFSymmetry in mixed quantum states can manifest in two distinct forms: strong symmetry, where each individual pure state in the quantum ensemble is symmetric with the same charge, and weak symmetry, which applies only to the entire ensemble. This paper explores a novel type of spontaneous symmetry breaking (SSB) where a strong symmetry is broken to a weak one. While the SSB of a weak symmetry is measured by the long-ranged two-point correlation function, the strong-to-weak SSB (SWSSB) is measured by the fidelity correlator. We prove that SWSSB is a universal property of mixed-state quantum phases, in the sense that the phenomenon of SWSSB is robust against symmetric low-depth local quantum channels. We also show that the symmetry breaking is “spontaneous” in the sense that the effect of a local symmetry-breaking measurement cannot be recovered locally. We argue that a thermal state at a nonzero temperature in the canonical ensemble (with fixed symmetry charge) should have spontaneously broken strong symmetry. Additionally, we study nonthermal scenarios where decoherence induces SWSSB, leading to phase transitions described by classical statistical models with bond randomness. In particular, the SWSSB transition of a decohered Ising model can be viewed as the “ungauged” version of the celebrated toric-code decodability transition. We confirm that, in the decohered Ising model, the SWSSB transition defined by the fidelity correlator is the only physical transition in terms of channel recoverability. We also comment on other (inequivalent) definitions of SWSSB, through correlation functions with higher Rényi indices
Classifying Hyperbolic Ergodic Stationary Measures on Compact Complex Surfaces with Large Automorphism Groups
Get PDFLet be a compact complex surface. Consider a finitely supported probability measure on such that is non-elementary. We do not assume that contains any parabolic elements. In this thesis, we study and classify hyperbolic, ergodic -stationary probability measures
Essays in Financial Economics
Get PDFThis dissertation consists of two chapters studying how news is priced in equity markets. Chapter 1 studies how earnings news becomes priced into stock returns. I use a demand system approach to show that this passthrough depends on investor responses to both earnings and prices and that these sensitivities are heterogeneous across investors. A key identification challenge is that earnings news is rapidly incorporated into prices; as a result, it is difficult to distinguish whether investors react to the earnings news itself or the concurrent price change. Using a two-step procedure to isolate price from earnings responses, I identify an average asset-weighted earnings elasticity of 3, i.e. for a stock that beats earnings expectations by 1\%, the average investor would increase his number of shares held by 3\% if prices were held fixed. These estimates vary across sectors, with most institutional investors more earnings elastic and price inelastic compared to the residual (``household") sector. The stock-level sensitivities implied by their ownership account for heterogeneous earnings passthroughs, as stocks with higher earnings sensitivity and lower price sensitivity see larger return responses from the same earnings surprise. Extremes of price and earnings elasticities are also closely related to misreaction: a strategy that bets on subsequent reversal (momentum) insensitive (insensitive) stocks in response to earnings news generates significant outperformance and alpha. These findings suggest that the pricing of earnings news is closely related to the ownership structure of stocks. Chapter 2 studies how inflation expectations affect stock returns, and what accounts for this relationship. I directly measure investors’ expectations using traded inflation-indexed contracts and show that, post-2000, stocks offer positive returns in response to higher expected inflation: unconditionally, a 10 basis point increase in 10-year breakeven inflation is associated with a 1.1% increase in the value-weighted stock index. Using a wide range of approaches, I show that this positive relationship is almost entirely due to aggregate variations in expected excess returns rather than changes in firm cash flows (e.g., due to higher mark-ups) or fluctuations in risk-free rates (e.g., due to expected monetary policy response). Overall, a risk premium ``proxy” mechanism appears to explain this dominant role of expected excess returns: higher long-term inflation expectations signal stronger future economic growth and reduced volatility
Too Close to Settle? The Role of Third-Party Proximity in World Trade Organization (WTO) Dispute Negotiations
Get PDFIn an era dominated by uncertain geopolitics, the World Trade Organization (WTO) offers an avenue for dispute resolution based on negotiations and an impartial litigation process through its Dispute Settlement Mechanism (DSM). Drawing on all WTO disputes from 1995 to 2016, this thesis develops a theory of proximity. It posits that increased third-party proximity increases main parties’ reputational and bargaining costs, decreases the cost of litigation and incentivizes panel ruling instead of early settlement, and employs probit regression to estimate how third‑party multilateral trade agreements (MTAs) influence early settlement probabilities. Results show marginal effects of 5 and 12 percentage points decrease in early settlement for every standard deviation increase in MTA Count and Depth, respectively, while trade volume shows mixed, insignificant results when other variables, including third-party presence and count, are held constant. These findings indicate that legal, not merely economic, proximity shapes bargaining dynamics in the WTO, suggesting that the WTO Secretariat and disputing members should prioritize monitoring institutional networks when allocating mediation resources, and that governments might strategically cultivate, or limit, their MTA portfolios to influence dispute outcomes
Stealth Authoritarianism: A Comparative Analysis of Surveillance Laws in the United States and Türkiye
No full textAgainst the backdrop of rising global authoritarianism, this study contributes to the literature on democratic backsliding by expanding Ozan Varol’s theory of stealth authoritarianism, the use of legal mechanisms with democratic credentials for anti-democratic ends, through an in-depth investigation of surveillance legislation. It develops a theoretical framework identifying three mechanisms through which surveillance practices enable stealth authoritarianism: legitimization through crisis, executive power consolidation, and civil liberties repression. To test this framework, the paper conducts a comparative case study of the United States (2001–2018) and Türkiye (1991–2017) to find similarities as both regimes’ surveillance fostered censorship and dissent prosecution; however, a divergence as Türkiye’s total consolidation of executive power, introduction of transparent practices, and rejection of domestic and global criticism indicate a turning point from democracy to non-democracy. These findings enforce the variation of surveillance mechanisms and anti-democratic outcomes to expand current scholarship’s understanding of democratic erosion within still-democratic regimes
Development of a Fundraising Resource Library for a Community-based Non-Profit Organization
Get PDFNonprofit organizations (NPOs) serve public interests through education, health, environment, and community services. Community-based NPOs like Out Our Front Door (OOFD) promote sustainability and local engagement through biking adventures while encouraging environmental awareness and cultural appreciation. To enhance its long-term impact, OOFD is revising its fundraising strategy by collaborating with the University of Chicago Alumni Relations and Development (ARD), considering the health and environmental advantages of biking. The goal of the project is to support OOFD in exploring fundraising strategies by creating a comprehensive resource library. As effective fundraising is vital to nonprofits’ survival, this project also addresses the growing need for donor-centered strategies, staff training and leadership engagement. A thematic analysis was conducted to identify patterns from both academic sources and survey responses from comparable NPOs, which serve as supplement insights from the current industry. Responses from 12 organizations reveal social media (91.7%) and email campaigns (83.3%) as the top fundraising tools, with Facebook being the most popular social media platform. The identified fundraising strategies include donor segmentation and diversified fundraising, and while online platforms provide visibility, they need to be used strategically. Additionally, personalized donor engagement and regular contact help improve retention. Emerging trends include peer-to-peer fundraising, a focus on recurring donors, and integrating volunteer engagement into donor pipelines. The shift of engagement towards mid-level donors highlights the need for relationship-based fundraising and long-term donor stewardship for sustainability. The final resource library included curated materials such as articles, webinars, platforms, and toolkits, targeting both beginner and advanced levels to help OOFD board members and volunteers improve fundraising effectiveness. Overall, the project serves as a resource center for members to access information on different fundraising strategies to improve the organization’s sustainability
Can Big Brother Travel? Chinese Surveillance Exports and Recipient Protest Activity
No full textA rich body of literature suggests that China engages in digital authoritarianism through exports of surveillance technology to illiberal states. Using data from the Global Database of Events, Language, and Tone, the Australian Strategic Policy Institute, and the United Nations Comtrade database, I challenge this prevailing viewpoint. Through a mixed methods approach, I argue that existing scholarship on this topic substantially overstates the degree to which China engages in the export of digital repression. In contrast to the prevailing theory of digital authoritarianism, I propose a theory of instrumental technological diffusion. In other words, I argue that Chinese exports of surveillance products are motivated primarily by instrumental and pragmatic goals, not ideology. China holds a comparative advantage in the manufacture of surveillance technology thanks to its repression of citizens domestically. But rather than attempting to export this model abroad, Beijing merely uses this comparative advantage as a tool to achieve other foreign policy objectives, namely closer relations with states. These recipient states, in turn, have relatively benign motives to seek out surveillance technology from China. An empirical analysis of trade flows reveals an ideologically diverse network of trade partners. Furthermore, I find only limited support for the idea that Chinese surveillance products produce declines in popular unrest. Indeed, in the short term, these exports may in fact increase, rather than decrease, protest activity. Taken together, these results suggest that counter to most intuitions, China does not engage in a coordinated campaign to foster technological illiberalism abroad, Furthermore, my findings indicate that such a campaign would be ineffective if it were to occur. These results carry important policy implications for decision makers in the West. They imply that countering China’s technological influence is not merely a matter of scaring partners about autocracy; it requires addressing the real public problems that drive them to accept Chinese solutions in the first place
Accidentally Emboldened: Industrial Workers between Democracy and Despotism on the Shop Floor in Wuhan, China (1984–1985)
Get PDFExisting scholarship on China's industrial politics in the early post-Mao era has not paid adequate attention to the tension between two seemingly contradictory tendencies: the reform drives to consolidate managerial despotism in urban public enterprises, and policy endeavors to strengthen formal institutional channels for workers to participate in their enterprises’ democratic management. Focusing on the city of Wuhan in 1984–1985, this article examines the policy logic behind these two overlapping tendencies and how workers experienced and reacted to them. It argues that, on the one hand, Wuhan's local authorities merely intended the institutional formalities of democracy to facilitate and build popular support for the inauguration of managerial despotism. On the other hand, workers’ very involvement in this façade of democracy accidentally emboldened many of them to air grievances, make subversive demands, assert agency, and even resist managerial despotism. These findings shed light on the nuanced historicity of 1980s China and contribute to a rethinking of the meaning of workplace democracy
From Biomass to Materials: Preparation of Biobased Carbon Materials and Modified Cellulose Nanocrystals
No full textIn Chapter 1, a literature review on cellulose nanocrystals (CNCs) and biobased carbon materials was conducted, which focuses on their structural properties, synthesis methods, and applications. In Chapters 2 and 3, research on utilizing MxG-CNC-COOH as a stabilizer for graphene in aqueous systems and as a binder for lithium-ion battery electrodes was presented. In Chapter 4, how grafting alkyl chains onto CNC surfaces affects the dispersion of these modified CNCs in organic solvents such as ethanol was explored. In Chapter 5, building on the findings from Chapter 4, the full dispersion of alkyl-chain-grafted CNC-COOH in DMSO was achieved, and the performance of this CNC-COOH in DMSO suspension as a substitute for the current PVDF/NMP system as a binder for lithium-ion battery cathodes in an anhydrous, NMP-free system was investigated. In Chapter 6, a method for synthesizing highly crystalline bio-graphite using biochar and iron powder as raw materials was developed. Slow cooling was found to be a critical step for the formation of high crystallinity bio-graphite product. And the bio-graphene produced from bio-graphite has shown the highest conductivity among all biobased carbon films or composites in the literature. Extending the work from Chapter 6, in Chapter 7, the influence of biomass composition on bio-graphite product was studied, and much cheaper Iron (III) nitrate was used as a precursor for the iron catalyst to convert MxG into a high-performance lithium-ion battery anode material. The relationship between the structure of bio-graphite and its anode performance was explored. In Chapter 7, one of the intermediates is a porous biochar prepared from iron (III) nitrate and MxG. In Chapter 8, this porous biochar as a support material for polyamines in direct air capture of carbon dioxide was further investigated, and synthesis methods for optimizing its pore structure were developed. Finally, in Chapter 9, all the above research was summarized, and directions for future studies were outlined
Dynamic Scheduling of Multiclass Queueing Systems in the Halfin-Whitt regime: A Computational Approach for High-Dimensional Problems
Get PDFThis dissertation studies the dynamic scheduling of high-dimensional multiclass queueing systems in the Halfin–Whitt regime, using a deep learning-based computational framework. Chapter 1 focuses on a multiclass, single server pool queueing system, while Chapter 2 generalizes the study to multiclass, parallel-server systems. In Chapter 1, we consider a multiclass queueing model of a telephone call center, in which a system manager dynamically allocates available servers to customer calls. Calls can terminate through either service completion or customer abandonment, and the manager strives to minimize the expected total of holding costs plus abandonment costs over a finite horizon. Focusing on the Halfin-Whitt heavy traffic regime, we derive an approximating diffusion control problem and building on earlier work by Beck et al. (2021) develop a simulation-based computational method for solution of such problems, one that relies heavily on deep neural network technology. Using this computational method, we propose a policy for the original (pre-limit) call center scheduling problem. Finally, the performance of this policy is assessed using test problems based on publicly available call center data. For the test problems considered so far, our policy does as well as or better than the best benchmark we could find. Moreover, our method is computationally feasible at least up to dimension 500, that is, for call centers with 500 or more distinct customer classes. In Chapter 2, we extend this framework to multiclass, parallel-server queueing systems with heterogeneous service stations, each consisting of multiple identical servers. Since not all customer classes are served by all service stations, the system forms a bipartite network. We consider a discounted-cost formulation over an infinite time horizon, in which the system manager chooses a scheduling/routing policy to minimize the expected discounted cost. We study general parallel-server systems, allowing for non-work-conserving policies and incorporating both basic and nonbasic activities. Focusing on the Halfin–Whitt regime, we derive an approximating diffusion control problem and building on the work by Han et al. (2018) we develop a simulation-based computational method that leverages deep neural networks to solve such problems. Using this method, we propose a policy for the original (pre-limit) parallel-server queueing system. Across the test problems considered so far, which are calibrated using publicly available call center data, our proposed policy performs as well as or better than the best available benchmark