VictorJuiz/thesis huggingface dataset:
Many-body spin dynamics with rydberg-dressed atoms
Keywords: Applied Physics.

A fundamental challenge of quantum science is to introduce controllable interactions in well isolated quantum systems. One approach is to excite neutral atoms to Rydberg states, thereby creating optically controlled long-range interactions. In order to take advantage of both the long-range interactions of the Rydberg states and the long spin-coherence times of ground-state atoms, we off-resonantly couple a cold dilute gas of cesium atoms to Rydberg states, using the technique of Rydberg dressing. In this thesis, I present the first experimental realization of the transverse-field Ising model with Rydberg dressing. We first demonstrate the creation of Ising interactions and characterize them via Ramsey spectroscopy. We observe one-axis twisting dynamics, a step towards creating spin-squeezed states with finite range interactions. By adding a periodic microwave drive, we are able to detect dynamical signatures of the paramagnetic-to-ferromagnetic phase transition. These results highlight the capability for locally and dynamically controlling the interaction strength. The apparatus constructed to realize these interactions additionally includes capabilities of quickly switching on and off the atomic interactions and dynamically changing the sign of the interactions. This work paves the way for many applications requiring spatiotemporal control of interactions in the fields of quantum simulation, quantum optimization, and quantum metrology
Marijuana in NYT
Keywords: marijuana
distributional semantics
word embeddings
cannabis
media
Thesis

Within the last few decades, the valence of marijuana on the stage of public
opinion has changed dramatically. As of 2020, 33 states have legalized
medical marijuana, and eleven have legalized marijuana for recreational use.
In this paper, I use word embeddings to explore changing media framing of marijuana, applying a potentially more granular methodology to see how media representations of charged topics change over time.
Market structure and dynamics
Keywords: Economics.

This thesis consists of three self-contained essays that investigate the algebraic structure of matching markets and the stabilization dynamics in decentralized markets. Chapter 2 is based on Wu and Roth (2018). It studies envy-free matchings that naturally arise from workers retiring or companies expanding. We show that the set of envy-free matchings forms a lattice that has a Conway-like join, but not a Conway-like meet. Furthermore, a job hopping process in which companies make offers to their favorite blocking workers, and workers accept their favorite offers, producing a sequence of vacancy chains, is a Tarski operator on this lattice. The fixed points of this Tarski operator correspond to the set of stable matchings; and the steady state matching starting from any given initial state is derived analytically. Chapter 3 is based on Wu (2020). The goal of this chapter, is to provide a systematic approach for analyzing entering classes in the college admissions model. When dealing with a many-to-one matching model, we often convert it into a one-to-one matching problem by assigning each seat of a college to a single student, instead of matching each college to multiple students. The preferences in this new model are significantly correlated and severely restrict the possible changes to entering classes. Through the so-called "rotations" that correspond to the join-irreducible elements in the lattice of stable matchings, we present a unified treatment for several results on entering classes, including the famous "Rural Hospital Theorem". We also show that, the least preferred student in an entering class appears to play a very interesting role. For example, each entering class can be completely characterized by its worst student. Chapter 4 is based on Gu, Roth, and Wu (2020). The motivating question is that, how come some black markets, such as the market for hitmen are well-regulated, but many others like the market for drugs are far from being under our control, even though we try very hard to eliminate them. To understand this, we build a three-dimensional discrete time Markov chain to study how black markets evolve over time, focusing on social repugnance and search frictions. We borrow tools from Markov jump processes, random walks, exponential martingales and optional sampling theory to analyze both the steady state limit and the realizations along the way. In the first part of the chapter, we identify conditions that lead to market survival or extinction. And the second part studies speed of convergence. We show that if a market is going to die eventually, then it dies exponentially fast. This further implies if a market has survived for a long time, then it is likely to survive forever
Markups to financial intermediation in foreign exchange markets
Keywords: Business.

Even in deep, liquid asset markets, financial intermediaries may have market power. To identify the effects of market power on asset prices, I study foreign exchange market arbitrages implied by deviations from covered interest rate parity. Previous literature equates these arbitrages to the shadow price of a balance sheet constraint on foreign exchange dealer banks. My work identifies cross-sectional variation in arbitrage returns that is inconsistent with the standard balance sheet constraint channel. My identification strategy relies on cross-country differences in the enforcement of capital constraints that decrease competition near quarter-end. Using a model of imperfect competition, I decompose CIP arbitrage returns into balance sheet cost and markup. Markups explain a significant portion of CIP arbitrage returns
Massive MIMO and robust modulation for high-performance wireless systems
Keywords: Electrical Engineering.

First, we consider physical layer cryptography in the context of the computational complexity associated with desired and undesired receivers decoding signals from massive MIMO arrays. We show that under proper conditions, decoding a massive MIMO signal by an eavesdropper is at least as hard as solving standard lattice problems that are conjectured to be prohibitively complex to solve even with a quantum computer. We use this result to design a wireless system where two users can reliably communicate with low overhead but decoding by an eavesdropper is prohibitively complex. Next, we study MIMO decoding when channel state information (CSI) is unknown to both the transmitter and receiver. We present an algorithm that leverages concepts of linear and mixed-integer linear programming to efficiently perform blind decoding with similar error probability as decoding under perfect CSI. Moreover, measures of the runtime of this algorithm suggest that the real-time blind decoding of MIMO signals is feasible for moderately large MIMO systems and offers several orders of magnitude increase in performance over existing techniques. Thus, our technique enables real-time blind MIMO decoding in rapidly time-varying channels with low probability of error. Finally, we present two novel modulation and detection techniques for channels that exhibit an arbitrary Doppler spread, assuming that the delay spread of the channel is low. These techniques, termed Frequency-Domain Multiplexing with a Frequency-Domain Cyclic Prefix (FDM-FDCP) and Single-Carrier Modulation with Time-Domain Equalization (SC-TDE), are able to compensate for the time variations associated with the Doppler spread. This compensation is done via a simple time-domain equalization method of comparable complexity to the frequency-domain equalization of OFDM. These modulation techniques are shown to outperform OFDM in terms of reliability and spectral efficiency in both high-mobility environments and in systems with high-carrier frequencies
Masters of the post : Northern Italy and European communications networks, 1530-1730
Keywords: History.

Masters of the Post demonstrates how the postal systems of Northern Italy contributed technology, personnel, and an ethical framework to the formation of the first global communications systems. The Tassis family and other residents of a single Alpine valley wielded disproportionate power as the agents of private and public correspondence. This dynasty of postmasters and postmistresses rose to Imperial titles as the House of Thurn und Taxis, but also served the Papacy, Venetian republic, and Spanish monarchy. Using archives in Italy, Spain, Germany and the United Kingdom, I retrace the systems that carried the correspondence of the early modern world. Scholarship on early modern communications has emphasized the technological improvements brought by postal waystations and roads. I reintroduce agents of infrastructure, exploring how the professionalization of mail carrying fit into a burgeoning bureaucracy and changing notions of public service. From diplomatic espionage to attacks on couriers, control over the mail saw the early modern state articulating new powers of surveillance, policing, and information security. Even the apparent failures of these efforts provide key insights into shifting expectations of the state in society, and the highly contingent development of a state postal system. Masters of the Post advances scholarship on the history of early modern commerce and statecraft. The postmaster was one of many quasi-state actors who traded in "intelligencing, " or the handling of politically sensitive information. While a confidante for princes, the postmaster was nonetheless frequently suspected of being a spy. Professional necessity drove the representation of state agents as impartial public servants. From the diplomatic fallout resulting from the 1556 political imprisonment of the Tassis postmaster in Rome, to the 1619 audit of the Tassis postmistress of Milan, accused of serving powerful Genoese businessmen before the state, the distinction between private and public interest was in constant negotiation. Consequently, professionalization of the postmaster adds important nuance to traditional models of bureaucratization in early modern Europe.The real and imagined worlds of long-distance communication overlapped, interacted, and diverged in literature and cartography. The public accessibility of the post raised new concerns about its potential for radical social impact. Like the mailbag, postal coaches, roads, and inns provided new settings for cross-cultural encounter. I turn to dictionaries, guidebooks, journals and other popular works to demonstrate how postal systems shaped commerce, communication, and tourism. Modern travelers and correspondent brought high expectation to postal systems as a utility that mediated between state power and commercial society. By following postal development into the eighteenth century, I demonstrate the reinvention of postal history as domestic infrastructural achievement and the Tassis as nonpartisan patrons
Mean field limit in neural network learning : autoencoders and multilayer networks
Keywords: Electrical Engineering.

A major outstanding theoretical challenge in deep learning is the understanding of the learning dynamics of neural networks. The difficulty arises from the highly nonlinear and large-scaled structure of the network architecture, usually involving a large number of neurons at each layer, and the non-convex nature of the optimization problem, typically solved by convexity-inspired gradient-based learning rules without any strong guarantees. This begs two questions: Given such complex nature, is it possible to obtain a succinct description of the network's behavior over the course of training? If so, could it be used to shed light on properties of the learning process of neural networks? We explore these questions in a scaling limit regime that gives rise to one such description: the mean field limit. In this regime, the number of neurons is taken to infinity, and yet the network's behavior under gradient descent training converges to a nontrivial and nonlinear dynamical limit. The literature of the mean field limit for neural networks is fairly recent and has focused on two-layer feedforward networks. In this thesis, we analyze the mean field limit for two other important classes of models: weight-tied two-layer autoencoders and multilayer networks. The class of autoencoders constitutes a unique example of two-layer neural networks for unsupervised learning. It is among the rare instances known till date that we can derive an explicit solution to the mean field limit. This allows us to gain in-depth understanding of what the model learns about the high-dimensional data. The derived theory offers a striking match with empirical simulations on real life data. This example also gives rise to a challenging mathematical problem that deviates from previous analyses and inspires a new proof technique, as well as an open conjecture. The class of multilayer neural networks is the main thrust behind the recent breakthrough of deep learning. Being fundamentally different from the two-layer counterpart, it requires completely new ideas and insights. We show the existence of the mean field limit for this class of models via two approaches. In the first approach, we develop a formalism with a new idea on the operational meaning of the neurons, which is a priori unobservable but allows to reason for the existence of a mean field limit. In the second approach, we develop a mathematically rigorous framework which is used to prove properties of multilayer networks under training, with a new idea on a continuum that interpolates from finiteness to infinitude. In both of these approaches, we see a complete departure from the convex paradigm and welcome new insights that are uniquely of neural networks
Mean field model for knowledge propagation and economic growth
Keywords: Mathematics.

My dissertation research is on the mathematical analysis of systems of partial differential equations that arise in modeling the equilibrium of mean filed games. I study the existence of traveling wave solutions of such systems and the large time behavior of the associated time dependent problem. Mean field models are used in optimal decision making based on stochastic games with a very large population of agents that are statistically the same. The main advantage of such models is that the overall effect of the other agents on a single one can be replaced by an averaged effect. Hence, the dynamics of a single agent can be determined as a solution of an optimal control problem that depends on the overall distribution of the agents. These models are governed by two partial differential equations, a forward Kolmogorov equation that keeps track of the distribution of agents in the model, and a backward Hamilton Jacobi Bellman (HJB) equation for the value function of the optimal stochastic control problem for each agent. An equilibrium solution to this mean field problem is a solution of the coupled system of the two equations. In my study I focus on an a mean field model for knowledge propagation and economic growth in which interaction between agents is represented by collisions and has diffusion added, in order to get a more realistic model for knowledge propagation. The equilibrium solution of such a mean field model is the solution of a Boltzmann equation for the agent distribution coupled to an HJB equation for the optimal strategy for the control problem. I have studied the existence of a BGP solution of the mean field learning model with diffusion in logarithmic variables. Such a solution can be considered as a generalization of traveling wave solutions of a system of Fisher-KPP (Fisher- Kolmogorov, Petrovsky, Piskunov) type of equation and an HJB equation. In Chapter 2 I prove that a traveling wave solution of the mean field learning model with diffusion exists and I have explored it numerically. The method that is used to construct traveling wave solutions is a variation of a well known method for the construction of traveling wave solutions of Fisher-KPP type equations. The numerical results that I have obtained in Chapter 4 support and extend the theory as many features observed numerically can be proved analytically. I have also studied analytically and numerically the forward-backward system, supplemented by an initial condition for the Fisher-KPP type of equation and a terminal condition for the HJB equation. In chapter 3 I have proved existence of solutions for a fixed terminal time T . In Chapter 4 I have tested the stability of the traveling wave numerically, by using perturbed traveling wave profiles for the initial value and I found that as time increases the solution of the time dependent problem tends to the traveling wave profiles
Measurement of the polarization of the cosmic microwave background with BICEP3 and the keck array telescopes
Keywords: Physics.

The Cosmic Microwave Background (CMB) shows the afterglow image of the Big Bang, providing a window to probe the very early Universe. The CMB encodes the information in the temperature and polarization fluctuations. BICEP3 and the Keck Array telescopes are small aperture refracting telescopes at the South Pole to measure the B-mode polarization of the CMB at the degree angular scales, which holds a key to probe inflation theory. This dissertation presents the progress of the BICEP/Keck Array telescopes on measuring the B modes and the recent test of low elevation observation with BICEP3 to expand its sky coverage at the South Pole. The BICEP/Keck Array telescopes produced the tightest constraint to the power of primordial B-modes, parameterized by the tensor-to-scalar ratio, r, to be less than 0.07 at 95% confidence with the one sigma uncertainty in r about 0.02, using polarization data up to 2015 observing season. BICEP3 was fully deployed for 2016 observing season and has been operating since. Together with the Keck Array telescopes operating at higher frequencies, we expect to achieve the one sigma uncertainty in r about 0.01 from data up to 2018 observing season. During the austral summer of 2018-19, we tested the feasibility of using BICEP3 to observe the CMB at a low elevation at the South Pole. Due to operational constraints, we had to use a flat mirror to direct the beams to the low elevation range. We obtained additional data at the end of the 2019 winter observing season. We present the temperature and polarization maps from this data set, which clearly shows the detection of the E mode polarization. This potentially opens an opportunity to cover an extended patch of the sky at the South Pole. If the primordial B-mode is detected at the main observing field, probing larger areas will reduce sample variance. Larger observing field is also important to study the non-Gaussianity and decorrelation of the foregrounds. An interesting patch in this extended region is the CMB Cold Spot, whose origin is still in question. The possibility of testing polarization anomaly deviating from the standard Gaussian fluctuation around the Cold Spot is discussed
Measuring the catalytic impact of nonresonant, pulsed radiation on reactions in the gas and solution phases
Keywords: Chemistry.

Light exists as a propagating wave of electric and magnetic fields. Exploration of the interactions between resonant light and matter has provided us with a wealth of structural and dynamical information. Largely overlooked, however, is the impact of nonresonant radiation which, when introduced into a reaction system from an intense, pulsed laser beam, may induce changes in the system through its associated strong electric field. At field strengths of 10 MV/cm, off-resonant radiation can influence the course of a reaction by interacting with the molecular system's polarizability, α, to lower an activation barrier directly. Because there is no net consumption of nonresonant photons, they behave as catalysts rather than reactants in a process referred to as "laser-field catalysis, " or "photon catalysis." In the experimental work presented in this dissertation, I investigate the impact(s) of a nonresonant IR field (1064 nm) on photoreactions in both the gas and solution phases: the photodissociation of deuterium iodide (gas), the photodissociation of phenol (gas), and the photoisomerization of cis-stilbene to trans-stilbene (solution). Two possible roles of the electric field, alignment of reagent molecules and dynamic Stark shifting of potential energy surfaces, are considered. Theoretical calculations are used to support experimental interpretation of results
Mechanics of thin film systems and the impact of external factors on underlying function
Keywords: Materials Science and Engineering.

Thin films surround us in more ways than one. From the devices in our phones to the skin on our bodies, thin films are everywhere. In my PhD work, I delved deep into the critical roles that these films play in our everyday life. First, I look at how our skin can effect our perception through tactile interactions with ourselves and the world around us. By applying cosmetic treatments, we can explore how changing biomechanical properties affect these neurological perceptions. Next, I demonstrate how thin film measurement methods used for inorganic films can be useful tools for exploring questions relevant to medicine and biomechanics. Finally, I apply similar methods to in situ characterization of novel solar absorbing films showing how applicable these thin film techniques can be to a wide range of material systems. In exploring skin mechanics, I will show how moisturizing and cleanser treatments can cause measurable changes in comfort for users. Then, I compare these results were compared to ex-vivo peak drying stress measurements and correlations of r(9) = -.88, p < .01 for moisturizers and r(6) = -.99, p < .01 for cleansers are shown. Finally, I develop a computational model was to demonstrate the transmission of SC drying stresses as strain fields to the lower receptor-laden layers of skin. These strain distributions suggest heightened mechanoreceptor activation correlated with stresses in the SC. Next, I show in different cardiovascular systems how bulge testing can be a useful tool for evaluating recovery of tissue. I demonstrate how mouse heart regeneration can be demonstrated from a functional perspective by measuring the modulus with bulge testing post infarction. Next, I am able to demonstrate key empirical evidence of heightened leaflet degradation in porcine leaflets when subjected to ex vivo testing modeling the Ross procedure. Finally, I will demonstrate the importance of thermomechanics when evaluating solar absorber behavior. Novel mechanisms for efficiency improvements are all the rage, but without proper controls, the results can often be misleading. By leveraging thin film systems developed for studying drying, Im able to show that key findings related to light induced expansion are fully explainable by thermal effects