Thesis advisor: James E. Anderson / The gravity model proved to to be one of the most successful framework for analyzing international trade flows, being referred to as the “workhorse” in the international trade literature (Head and Mayer (2014)). Microfoundations to this model has been provided in Anderson (1979) and it has often been employed to estimate the effects of a variety of trade policies (see Cipollina and Salvatici (2010) for a meta-analysis on reciprocal trade agreements, Rose (2000) for the effects of currency unions). The two chapters of this dissertation, which are independent empirical pieces, both make use of gravity equations for the estimation of trade flows, although with different purposes. The first chapter focuses on the specification of the gravity equation. In the second chapter, instead, gravity equations are employed for assessing the relationship between trade and growth: in fact, their estimation represents the first step for the creation of an instrumental variable for export flows. In the first chapter, a solo-authored work titled Scale Economies in European Trade, I show that European data support the existence of economies of scale in trade flows. The impact of trade costs on trade flows, in fact, is assumed to be constant by almost all empirical studies employing the gravity framework. Anderson et al. (2016) are the first to depart from this assumption, allowing trade costs to vary as a function of trade volumes. Their model nests the more traditional one and hence can be used to test for the existence of these scale economies, which are shown to be in place for trade between US and Canada. For my analysis I construct a comprehensive dataset for European trade in manufacturing over a long time span (from 1980 to 2013), on which I employ the same methodology. My results show that scale economies in trade costs are indeed a strong empirical fact outside of the American continent, and this holds for all the 26 manufacturing sectors considered, with an estimated average of 0.64% decrease in trade costs given by a 10% increase in trade volume. The focus on Europe allows me to test whether the EU expansion affected these economies of scale. While this is not true on average, it seems to be the case for some industries: trade with a EU partner entails scale elasticities 50% lower than trade with a non-EU member for 11 sectors out of the 26 considered. I also investigate whether scale elasticities can be rationalized by the existence of informational asymmetries. Using detailed product-level data, I do not find evidence that the degree of product homogeneity can account for the observed cross-sectoral variation. The scale coefficients are instead linked to country-specific institutional variables, such as the level of corruption: exporting to the country whose level of corruption is the lowest in the sample entails half the scale elasticity than exporting to the most corrupted one. In other words, corruption depresses trade to an higher extent on longer distances. In the second chapter, joint with Carlo Altomonte and Italo Colantone and titled Trade and Growth in the Age of Global Value Chains, we revisit the relationship between trade and income, taking into account the recent surge of global value chains (GVCs). First, we develop a new geography-based, time-varying instrument for export, exploiting the sharp increase (almost tripling) in the maximum size of container ships between 1995 and 2007. This global shock has an asymmetric impact on bilateral trade flows across countries, affecting disproportionately more countries endowed with a larger number of deep-water ports, which are needed to accommodate the new, much larger ships. We exploit this heterogeneity for identification, building up the instrument for export in a gravity framework. Our result show that export has a positive effect on GDP per capita, with a 0.6 elasticity. Evidence at the country-level shows that this effect works through capital accumulation. Exploiting the decomposition methodology by Wang et al. (2013), we show that differences in the value added composition of exports matter for trade-growth nexus. We find evidence in favor of an income premium for countries that upgrade their positioning in GVCs, whereas the degree of participation to GVCs does not seem to play a role. Consistent with this finding, we show that countries whose average level of upstreamness (a’ la Antras and Chor (2013)) increases the most over time exhibit a higher trade elasticity of income. Both papers indirectly deal with the effect of geographical distance on international trade flows. One of the strongest regularities in economics is certainly the negative role played on trade flows by the distance between origin and destination. Disdier and Head (2004), comparing 1,467 different studies, compute an average distance elasticity of trade of about -0.9. Hummels (2007) shows that the distance elasticity of trade does not seem to diminish over time, as it would do should distance be capturing only transportation costs, thanks to the technological developments witnessed in the transportation sector. Distance seems then to refer to trade costs in general, including institutional, policy and regulatory barriers that, also for historical reasons, often increase the further away countries are located. In the first paper, I show that the impact of distance on trade flows is not constant but varies with trade volumes. This corresponds with having a component of the composite friction described before, hidden in the distance term, being fixed and is consistent with micro-evidence on the export behavior obtained from firm-level data (Roberts and Tybout (1997)). It seems natural, then, to test whether some characteristics, either at the product-level or at the country-level, have a prominent role in explaining the non-linear effect that distance has on trade. My results find in level of corruption of the destination country an important determinant. In the second paper, we test whether the distance elasticity of trade varies as a function of the number of deep water ports on both the importer’s and the exporter’s shores, capturing the extent to which countries can trade via container vessels. The data support this claim for all the manufacturing sectors considered, showing that geographical distance, even though non-exclusively, captures the incidence of transportation costs on export flows. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

In this dissertation we study the dynamics of loop quantum gravity and its applications. We propose a tunneling phenomenon of a black hole-white hole transition and derive an amplitude for such transition using the spinfoam framework. We investigate a special class of kinematical states for loop quantum gravity - Bell spin networks - and show that their entanglement entropy obeys the area law. We develop a new spinfoam vertex amplitude that has the correct semi-classical limit. We then apply this new amplitude to calculate the graviton propagator and a cosmological transition amplitude. The results of these calculations show feasibility of computations with the new amplitude and its viability as a spinfoam model. Finally, we use physical principles to radically constrain ambiguities in the cosmological dynamics and derive unique Hamiltonian dynamics for Friedmann-Robertson-Walker and Bianchi I cosmologies. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Gravity measurements made during 1979 and 1980, combined with existing gravity measurements, provide data for the interpretation of upper crustal structures relevant to the assessment of the geothermal potential of south-central Oregon. West of Upper Klamath Lake, free-air gravity anomalies trend north-south and average near 35 mgals. East of Upper Klamath Lake, free-air gravity anomalies trend west to northwest, and average near ten mgals. The complete Bouguer anomaly field exhibits a regional gradient of nearly .4 mgals/km, which is attributed to the existence of a low-density upper mantle layer beneath the Basin and Range province. The large northwest-trending negative anomaly associated with the Klamath graben suggests a depth of low-density fill of up to 2300 m (7500 feet). The regional gravity field exhibits a broad regional high over the area surrounding Klamath Falls which may be caused by a shallow mantle or a large intrusive body at depth, or may simply be due to intense silicification of the area by thermal waters. The residual anomaly field exhibits broad bands of positive anomalies which enclose the negative anomaly associated with the Klamath graben. The easternmost of these broad, positive trends may correspond to the eastern flank of an anticline which may have existed prior to graben faulting. Positive anomalies west of the graben coincide with the Mount McLoughlin lineament. A large positive anomaly located south of Sprague River is interpreted to be a volcanic center and the heat source for thermal waters found in the Sprague River Valley. A two-dimensional cross section near 42°26' N. latitude suggests that step-like faults form the west side of the Klamath graben. The model indicates the presence of a high density body south of Sprague River that is interpreted to be a buried volcanic source for local extrusive volcanic rocks. Northwest-trending gravity anomalies west of Upper Klamath Lake indicate that structural trends of the Basin and Range province extend into the Cascade Mountains, and suggest that a heat source for thermal waters may exist beneath the High Cascades, rather than beneath the areas which exhibit geothermal activity. / Graduation date: 1982

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20177号 / 理博第4262号 / 新制||理||1613(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 佐々木 節, 教授 田中 貴浩, 教授 川合 光 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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This thesis is a study of classical and quantum gravity with Ashtekar variables. The Ashtekar constraints are shown to capture the essence of the constraints and constraint algebra of General Relativity in four dimensions. A classification scheme of the solution space of the Ashtekar constraints is proposed and the corresponding physics is investigated. The manifestly covariant equations of motion for the Ashtekar variables are derived. Explicit examples are discussed and new classical solutions of General Relativity are constructed by exploiting the properties of the Ashtekar variables. Non-perturbative canonical quantization of the theory is performed. The ordering of the quantum constraints as well as the formal closure of the quantum constraint algebra are explored. A detailed Becchi-Rouet-Stora-Tyutin (BRST) analysis of the theory is given. The results demonstrate explicitly that in quantum gravity, fluctuations in topology can occur and there are strong evidences of phases in the theory. There is a phase which is described by a topological quantum field theory (TQFT) of the Donaldson-Witten type and an Abelian antiinstanton phase wherein self-interactions of the gravitational fields produce symmetry breaking from SO(3) to U(1). The full theory is much richer and includes fluctuations which bring the system out of the various restricted sectors while preserving diffeomorphism invariance. Invariants of the quantum theory with are constructed through BRST descents. They provide a clear and systematic characterization of non-local observables in quantum gravity, and can yield further differential invariants of four-manifolds. / Ph. D.

Groundwater provides a fundamental resource for modern life. Throughout the world, groundwater is managed by storing (recharging) it underground in natural aquifers for future withdrawal and consumptive use. In Arizona, over 4 million people benefit from managed aquifer storage, but little effort is made to track the movement of recharged water through the subsurface. Motivated by current limitations in our ability to monitor percolation and groundwater movement at the scale of a recharge facility, an effort to collect time-lapse gravity data was carried out at the Southern Avra Valley Storage and Recovery Project (SAVSARP) operated by the City of Tucson, Arizona. In addition to collecting water-level data 12 wells, there were three primary gravity experiments: (1) five continuously-recording gravity meters (2 iGrav superconducting gravity meters and 3 gPhone gravity meters) were installed semi-permanently in control buildings adjacent to the recharge basins, (2) absolute gravity measurements were made at nine locations over a 17 month period, and (3) three relative-gravity campaigns were carried out on a network of 70 stations. This large-scale controlled experiment, with known infiltration and pumping rates, resulted in one of the most comprehensive datasets of its kind. Gravity data led to several hydrologic insights, both through direct measurement and modeling. First, the infiltration rate could be estimated accurately based on the initial rate of gravity change during infiltration, regardless of the specific yield. Using two gravity meters, the depth, and therefore speed, of the wetting front beneath a recharge basin was observed, including the time at which the water table was reached. Spatial maps of gravity change from relative gravity surveys show areas where infiltration efficiency is highest, and where groundwater accumulates; storage accumulated preferentially to the west of the recharge basins, away from pumping wells. Such information would be valuable for planning the location of pumping wells at a new facility. Gravity data were useful for calibration of a Modflow-NWT groundwater-flow model using the Unsaturated Zone Flow package to simulate recharge; the reduction in the posterior parameter distribution compared to the a priori estimate was substantial and similar to head data. In contrast to model-simulated head data, model-simulated gravity data were less sensitive to more distant model elements and more effective for calibration of a superposition-type model. Observed head data had a strong regional signal reflecting basin-scale conditions with only minor variation associated with individual recharge basins, and were therefore of limited usefulness for model calibration. Together, the methods developed by the study and interpretations they made possible suggest that gravity data are an effective way to better understand large-scale infiltration and groundwater movement.

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