15,988 research outputs found

    The integral cohomology ring of four-dimensional toric orbifolds

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    Although toric orbifolds are fundamental objects in toric topology, their cohomology rings are largely unknown except for very few special cases. The goal of this paper is to investigate the cohomology rings of 4-dimensional toric orbifolds. Let X(P,λ)X(P,\lambda) is a 4-dimensional toric orbifold associated to a polygon PP and a characteristic function λ\lambda. Assuming X(P,λ)X(P,\lambda) is locally smooth over a vertex of PP, we construct an additive basis of H(X(P,λ);Z)H^*(X(P,\lambda);\mathbb{Z}) and express the cup products of the basis elements in terms of PP and λ\lambda. Further we derive a formula for computing cup products in H(X(P,λ);R)H^*(X(P,\lambda);R), where X(P,λ)X(P,\lambda) is any general 4-dimensional toric orbifold and RR is a principal ideal domain satisfying a mild condition.Comment: 51 pages, 6 figure

    Simultaneous assimilation of Fengyun-4A and Himawari-8 aerosol optical depth retrieval to improve air quality simulations during one storm event over East Asia

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    Aerosols are the main components of air pollutants, which are closely related to haze, dust storm and air pollution. In this study, an aerosol data assimilation system was developed using Gridpoint Statistical Interpolation (GSI) system to assimilate the Aerosol Optical Depth (AOD) observations from FY4 and Himawari-8 for the first time and applied in the heavy dust case over east Asia in March 2018. Three parallel experiments assimilated AOD from FY4, Himawari-8 and both the FY4 and Himawari-8 respectively and a control experiment which did not employ DA were performed. The hourly aerosol analyses and forecasts are compared with the assimilated FY-4 AOD, Himawari-8 AOD and independent AOD from Aerosol Robotic Network (AERONET). The results showed that all forms of DA experiments improved a low Bias and the RMSE reduced about 20%. The aerosol data assimilation with observations from both the FY-4 and Himawari-8 satellites substantially improved aerosol analyses and subsequent forecasts with more abundant aerosol observation information, especially over the northwest of China. This study indicates that the new generation geostationary meteorological satellites have potential to dramatically contribute to air quality forecasting

    On p-group isomorphism: Search-to-decision, counting-to-decision, and nilpotency class reductions via tensors

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    In this paper we study some classical complexity-theoretic questions regarding Group Isomorphism (GpI). We focus on p-groups (groups of prime power order) with odd p, which are believed to be a bottleneck case for GpI, and work in the model of matrix groups over finite fields. Our main results are as follows. Although search-to-decision and counting-to-decision reductions have been known for over four decades for Graph Isomorphism (GI), they had remained open for GpI, explicitly asked by Arvind & Torán (Bull. EATCS, 2005). Extending methods from Tensor Isomorphism (Grochow & Qiao, ITCS 2021), we show moderately exponential-time such reductions within p-groups of class 2 and exponent p. Despite the widely held belief that p-groups of class 2 and exponent p are the hardest cases of GpI, there was no reduction to these groups from any larger class of groups. Again using methods from Tensor Isomorphism (ibid.), we show the first such reduction, namely from isomorphism testing of p-groups of “small” class and exponent p to those of class two and exponent p. For the first results, our main innovation is to develop linear-algebraic analogues of classical graph coloring gadgets, a key technique in studying the structural complexity of GI. Unlike the graph coloring gadgets, which support restricting to various subgroups of the symmetric group, the problems we study require restricting to various subgroups of the general linear group, which entails significantly different and more complicated gadgets. The analysis of one of our gadgets relies on a classical result from group theory regarding random generation of classical groups (Kantor & Lubotzky, Geom. Dedicata, 1990). For the nilpotency class reduction, we combine a runtime analysis of the Lazard Correspondence with Tensor Isomorphism-completeness results (Grochow & Qiao, ibid.)

    BECOMEBECOME - A TRANSDISCIPLINARY METHODOLOGY BASED ON INFORMATION ABOUT THE OBSERVER

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    ABSTRACT Andrea T. R. Traldi BECOMEBECOME A Transdisciplinary Methodology Based on Information about the Observer The present research dissertation has been developed with the intention to provide practical strategies and discover new intellectual operations which can be used to generate Transdisciplinary insight. For this reason, this thesis creates access to new knowledge at different scales. Firstly, as it pertains to the scale of new knowledge generated by those who attend Becomebecome events. The open-source nature of the Becomebecome methodology makes it possible for participants in Becomebecome workshops, training programmes and residencies to generate new insight about the specific project they are working on, which then reinforce and expand the foundational principles of the theoretical background. Secondly, as it pertains to the scale of the Becomebecome framework, which remains independent of location and moment in time. The method proposed to access Transdisciplinary knowledge constitutes new knowledge in itself because the sequence of activities, described as physical and mental procedures and listed as essential criteria, have never been found organised 6 in such a specific order before. It is indeed the order in time, i.e. the sequence of the ideas and activities proposed, which allows one to transform Disciplinary knowledge via a new Transdisciplinary frame of reference. Lastly, new knowledge about Transdisciplinarity as a field of study is created as a consequence of the heretofore listed two processes. The first part of the thesis is designated ‘Becomebecome Theory’ and focuses on the theoretical background and the intellectual operations necessary to support the creation of new Transdisciplinary knowledge. The second part of the thesis is designated ‘Becomebecome Practice’ and provides practical examples of the application of such operations. Crucially, the theoretical model described as the foundation for the Becomebecome methodology (Becomebecome Theory) is process-based and constantly checked against the insight generated through Becomebecome Practice. To this effect, ‘information about the observer’ is proposed as a key notion which binds together Transdisciplinary resources from several studies in the hard sciences and humanities. It is a concept that enables understanding about why and how information that is generated through Becomebecome Practice is considered of paramount importance for establishing the reference parameters necessary to access Transdisciplinary insight which is meaningful to a specific project, a specific person, or a specific moment in time

    Quantum Phase transitions observed in a moving frame and emergent space-time near Quantum Phase transitions

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    The important role of Lorentz transformation (LT) and invariance (LI) in relativistic quantum field theory is well appreciated and understood. At a low velocity, the LT just reduces to the Galileo transformation (GT). While many body systems in materials or cold atom systems break the LI spontaneously or explicitly, therefore are non-relativistic. Unfortunately, the possible effects of GT in these non-relativistic quantum many-body systems were poorly understood. In this work, we explore its dramatic effects, especially near quantum phase transitions (QPT) which are among the most fantastic phenomena in Nature. We show that an observer in a different inertial frame may detect new quantum phases through novel quantum phase transitions. We demonstrate this new effect by studying one of the simplest QPTs: Superfluid (SF)-Mott transitions of interacting bosons in a square lattice observed in a frame moving with a constant velocity v \vec{v} relative to the underlaying lattice. These new effects are contrasted to the Doppler shifts in a relativistic quantum field theory, Unruh effects in an accelerating observer and non-relativistic AdSd+1/CFTd AdS_{d+1}/CFT_d correspondence at a low d d .The methods can be extended to study all the quantum and topological phase transitions, even some dynamic classical phase transition in a moving frame in any dimension. an effective way not only measure various intrinsic properties of the materials, tune various quantum and topological phases through phase transitions, but also probe the new emergent space-time structure near any QPT. As a byproduct, we also comment on the GT and GI in fractional Quantum Hall systems and the associated edge states.Comment: 60 PRB pages, 12 figures, Sec.IX-A and B contains part of arXiv:cond-mat/0512480 for the sake of self-contained. We dedicate this work to celebrate the 75th birthday of Moses Chan, a world class experimentalist and 60th birthday of Subir Sachdev, a world class theoris

    Spin-orbit coupling in organic microcavities: lower polariton splitting, triplet polaritons and disorder induced dark states relaxation

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    Using an extended Tavis-Cummings model, we study the effect of the spin-orbit coupling between the singlet and the triplet molecular excitons in organic microcavities in the strong coupling regime. The model is solved in the single excitation space for polaritons, that contain the bright (permutation symmetric) singlet and triplet excitons, as well as the dark bands consisting of the non-symmetric excitons of either type. We find that the spin-orbit coupling splits the lower polariton into two branches, and also creates a novel triplet polariton when the cavity mode is in resonance with the triplet excitons. The optical absorption spectrum of the system that can reveal this splitting in experiments is presented and the effect of disorder in exciton energies and couplings is explored. An important consequence of the disorder in the spin-orbit coupling - a weak coupling between the otherwise decoupled bright and dark sectors - is explored and detailed calculations of the squared transition matrix elements between the dark bands and polaritons are presented along with derivation of some approximate yet quite accurate analytical expressions. This new relaxation channel for the dark states contains an interference between two transition paths that, for a given polariton state, suppresses the relaxation of one dark band and enhances it for the other.Comment: 16 pages, 10 figure

    A cosmopolitan international law: the authority of regional inter-governmental organisations to establish international criminal accountability mechanisms

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    The overall aim of this thesis is to investigate the potential role of regional inter-governmental organisations (RIGOs) in international criminal accountability, specifically through the establishment of criminal accountability mechanisms, and to make a case for RIGOs’ active involvement. The thesis proceeds from the assumption that international criminal justice is a cosmopolitan project that demands that a tenable conception of state sovereignty guarantees humanity’s fundamental values, specifically human dignity. Since cosmopolitanism emphasises the equality and unity of the human family, guaranteeing the dignity and humanity of the human family is therefore a common interest of humanity rather than a parochial endeavour. Accountability for international crimes is one way through which human dignity can be validated and reaffirmed where such dignity has been grossly and systematically assaulted. Therefore, while accountability for international crimes is primarily the obligation of individual sovereign states, this responsibility is ultimately residually one of humanity as a whole, exercisable through collective action. As such, the thesis advances the argument that states as collective representations of humanity have a responsibility to assist in ensuring accountability for international crimes where an individual state is either genuinely unable or unwilling by itself to do so. The thesis therefore addresses the question as to whether RIGOs, as collective representations of states and their peoples, can establish international criminal accountability mechanisms. Relying on cosmopolitanism as a theoretical underpinning, the thesis examines the exercise of what can be considered as elements of sovereign authority by RIGOs in pursuit of the cosmopolitan objective of accountability for international crimes. In so doing, the thesis interrogates whether there is a basis in international law for such engagement, and examines how such engagement can practically be undertaken, using two case studies of the European Union and the Kosovo Specialist Chambers and Specialist Prosecutor’s Office, and the African Union and the (proposed) Hybrid Court for South Sudan. The thesis concludes that general international law does not preclude RIGOs from exercising elements of sovereign authority necessary for the establishment of international criminal accountability mechanisms, and that specific legal authority to engage in this regard can then be determined by reference to the doctrine of attributed/conferred powers and the doctrine of implied powers in interpreting the legal instruments of RIGOs. Based on this conclusion, the thesis makes a normative case for an active role for RIGOs in the establishment of international criminal accountability mechanisms, and provides a practical step-by-step guide on possible legal approaches for the establishment of such mechanisms by RIGOs, as well as guidance on possible design models for these mechanisms

    Paradoxes in the Management of Timebanks in the UK’s Voluntary Sector: Discursive Bricolage and its Limits

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    This paper contributes to our understanding of volunteer management by charting some important challenges associated with the governance of one of the UK’s largest timebanking networks. While timebanking is often treated as a form of volunteering, many timebank advocates are keen to distinguish it sharply from traditional volunteering. We suggest that this tension generates a fundamental ‘performance paradox’ in the management of timebanks in the voluntary sector. We draw on political discourse theory to characterise and evaluate associated challenges, suggesting that, when viewed against a host of context-specific organisational and policy pressures, the progressive potential of timebanking cannot be realised as a distinct community economy without adequate support. Instead of taking up a position alongside more traditional forms of volunteering, timebanking is more likely to be subsumed by them

    Political thought of Friedrich von Gentz, 1800-1812

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    This thesis focuses on the political writings of Friedrich von Gentz, a German writer and political advisor, between the years 1800 and 1812. Scholarship has tended to focus on the years 1791­1801 and Gentz’s political conversion from support of to opposition to the French Revolution, his translation of Edmund Burke’s work, and his contribution to debates over international relations in the years 1800 and 1801. This thesis both reassesses his stance on international relations, presenting him as a complex thinker rather than a crude realist, and unpacks three relatively unexplored areas of his thought, those of international law, civil society and censorship. The first chapter explores Gentz’s defence of the balance of power against the theoretical objections of philosophers like Immanuel Kant and the practical threats of diplomats like Alexandre D’Hauterive. It shows that Gentz was not purely concerned with power but included a subtle and high regard for the role of domestic constitutions, culture, commerce and moral formation. The second chapter considers Gentz’s understanding of international law and, as an illustration of this, his views on the issue of neutral rights at sea. Gentz held to a dualist conception of international law that blended both natural and positive law, and he defended it against attacks from both sides. The third chapter unpacks Gentz’s changing thought on commerce and civil society amidst the instability of Napoleonic expansion. He believed that there was a causal chain that led from the rise of commerce, to the decline of civil society and on to a universal monarchy of a Montesquieuian mould. The fourth chapter considers Gentz’s writings on the press at the time of Napoleon in order to assess the claim he betrayed his 1797 defence of a free press when he supported the 1819 Karlsbad Decrees. It is shown that Gentz developed his views in light of the Napoleonic experience and did not simply sell out to the powers that be. Overall, this thesis argues for the greater richness and complexity of Gentz’s thought than hitherto realised and for the many­sided character to his conservatism, which in turns points to the many­sided nature of conservatism in general

    "Alien and Critical": The Modernist Satiric Practices of Djuna Barnes, Wyndham Lewis, and Virginia Woolf

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    This dissertation offers an extended analysis of the modernist satiric practices of authors Djuna Barnes, Wyndham Lewis, and Virginia Woolf in a selection of works spanning different genres published between 1913 and 1954. With these authors works as evidence, I suggest that satire undergoes a significant shift in the first half of the twentieth century as it departs from its premodern roots as a fixed genre or mode, instead becoming a diffuse element that intermittently shapes formal aspects and produces complex critiques. This shift partly results from new formulations of genderfrom altered understandings of masculinity and femininity to the emergence of what we now refer to as queer, nonbinary, and trans identitiesand the way in which what I call the instrumentality of satire enables a range of satiric attacks across different subject positions and a volatile political spectrum. Through a highly comparative approach, I draw upon formalist, feminist, and sociological theories to trace the different networks in which the texts of focus and their authors are embedded (networks of readers, artistic movements, political transformations, marketplaces, and discourses of gender and sexuality) to understand more thoroughly the satire that emerges from these texts. Each chapter pairs discrete investigations of works by each individual author, guided by an overarching topic (Chapter 1 explores networks of satire, Chapter 2 examines satiric method and the novel, and Chapter 3 considers satiric forms of life writing), and ends with a shorter section that compares the three authors works within a specific thematic framework (Chapter 1 with respect to the notion of authority, Chapter 2 through party scenes, and Chapter 3 concerning the portrait genre). My research reveals that the modernist satiric exchanges within these networks can be analyzed as, on the one hand, manifestations of the selected periods political dynamics and, on the other hand, cultural productions that altered how gender was discursively constructed within specific social environments of that period. In brief, the study illustrates how gender and its performance, aesthetics, and rhetoric become central to the production and function of satire in modernist art and literature
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