cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
A characterization of ramification groups of local fields with imperfect residue field
Creators: name: Saito, Takeshi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11S15

description: We give a characterization of ramification groups of local fields with imperfect residue fields, using those for local fields with perfect residue fields. As an application, we reprove an equality of ramification groups for abelian extensions defined in different ways.
description: 10 pages
Spitzer/MIPS Imaging of NGC 650: Probing the History of Mass Loss on the Asymptotic Giant Branch
Creators: name: Ueta, Toshiya
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present the far-infrared (IR) maps of a bipolar planetary nebula (PN), NGC 650, at 24, 70, and 160 micron taken with the Multiband Imaging Photometer for Spitzer (MIPS) on-board the Spitzer Space Telescope. While the two-peak emission structure seen in all MIPS bands suggests the presence of a near edge-on dusty torus, the distinct emission structure between the 24 micron map and the 70/160 micron maps indicates the presence of two distinct emission components in the central torus. Based on the spatial correlation of these two far-IR emission components with respect to various optical line emission, we conclude that the 24 micron emission is largely due to the [O IV] line at 25.9 micron arising from highly ionized regions behind the ionization front, whereas the 70 and 160 micron emission is due to dust continuum arising from low-temperature dust in the remnant asymptotic giant branch (AGB) wind shell. The far-IR nebula structure also suggests that the enhancement of mass loss at the end of the AGB phase has occurred isotropically, but has ensued only in the equatorial directions while ceasing in the polar directions. The present data also show evidence for the prolate spheroidal distribution of matter in this bipolar PN. The AGB mass loss history reconstructed in this PN is thus consistent with what has been previously proposed based on the past optical and mid-IR imaging surveys of the post-AGB shells.
description: 9 pages in the emulated ApJ format with 6 figures, to appear in ApJ
Simulating Noisy Diamond Quantum Computers
Creators: name: Mingare, Angus
Publisher: name: The Australian National University
Year: 2021
Subjects: Quantum computing
noisy quantum computer
diamond quantum computer
simulating quantum computers
tensor networks
Matrix Product States
Kraus model
control errors

description: Quantum computers have enormous promise in areas as diverse as medicine, finance, defence and information security. NV-centres in diamond are a promising platform for quantum computing due to their long coherence times at room temperature. However, current quantum computers are characterised by their noisy operation and do not provide any quantum advantage. Classical simulations can be used to provide feedback on various sources of noise to guide future engineering designs. Simulations can also be used to benchmark real quantum computers, and develop new quantum algorithms. Unfortunately, current noisy simulators are phenomenological and limited in scale. Hence they often poorly represent the general behaviour of real quantum computers, limiting their utility. In this thesis I work towards developing an accurate, efficient simulator of noisy diamond quantum computers, with results generalisable to other architectures. I first compare the performance of two state of the art simulation methods to identify which is the most efficient. By performing runtime comparisons, I demonstrate that a leading Schrodinger simulator outperforms a leading tensor network simulator when performing high fidelity simulations, at least for fewer than 30 qubits. Next, I derive and validate a noise model based on decoherence and single-qubit control errors in diamond quantum computers. By simulating single-qubit circuits, I show that a depolarising channel produces simulations with a higher fidelity than the derived model. I attribute this to the small errors in single-qubit circuits favouring the fitted depolarising channel, which would not hold for multi-qubit circuits. I conclude that while the derived model requires further developments, it still offers immediate advantages over phenomenological models.
Gravity Control by means of Electromagnetic Field through Gas or Plasma at Ultra-Low Pressure
Creators: name: De Aquino, Fran
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Physics (physics.gen-ph)
subject: FOS: Physical sciences

description: It is shown that the gravity acceleration just above a chamber filled with gas or plasma at ultra-low pressure can be strongly reduced by applying an Extra Low-Frequency (ELF) electromagnetic field across the gas or the plasma. This Gravitational Shielding Effect is related to recent discovery of quantum correlation between gravitational mass and inertial mass. According to the theory samples hung above the gas or the plasma should exhibit a weight decrease when the frequency of the electromagnetic field is decreased or when the intensity of the electromagnetic field is increased. This Gravitational Shielding Effect is unprecedented in the literature and can not be understood in the framework of the General Relativity. From the technical point of view, there are several applications for this discovery; possibly it will change the paradigms of energy generation, transportation and telecommunications.
description: 74 pages. arXiv admin note: substantial text overlap with arXiv:gr-qc/9910036, arXiv:physics/9904018
Growing community food economies in the Philippines
Creators: name: Hill, Margaret Ann
Publisher: name: The Australian National University
Year: 2018
Subjects: subject: Agriculture Economic aspects Philippines
subject: Food supply Philippines
subject: Food cooperatives Philippines
subject: Philippines Economic conditions

description: This thesis is about collective ethical economic action for a climate and resource changing world. It is a series of re-thinking economy experiments in the food arena based on my research in the Philippines. In the thesis I argue for a new mode of critical inquiry that centres on matters of anthropogenic concern: gathering and assembling economic diversity; human actancy; and human-nonhuman actancy, in order to grow post-capitalist food economies. I also argue for hybrid collective ethics and methods that cultivate new ways of being in the world leading to new economic and food futures. In the empirical chapters I show how urban neighbourhoods in Northern Mindanao and Manila are addressing food economy concerns such as malnutrition, food security, poverty and post-typhoon livelihood re-building through collective ethical economic actions. I demonstrate the importance of cultivating enabling political, social and economic environments. The strength and innovation of this thesis is that it employs a collective methodological approach to extend theoretical understanding of collective ethics. Nested in Community Economies Collective scholarship, this research grew out of an action research project on local economic development in the Philippines. The thesis research links various other Philippines-based networks in the fields of agroecology, social enterprise development, local governance and community-based disaster preparedness. My doctoral project enacted community food economies by harnessing these networks and their diverse knowledge practices in an innovative workshop event and through the formation of new hybrid collectives. These collectives include 'actors' as colourfully diverse as municipality mayors, local government workers, landless poor urban communal gardeners, NGO workers, agronomists and sanitation scientists, economic geographers, privately owned vacant land, waste-dump sites, composting toilets, human manure, vegetables, flooding rivers, super typhoons, waste tetra-packs, recycled bamboo, janitor fish and digital media tools. The hybrid collective networks that were formed during the doctoral research have continued beyond the project. For example, a network of home farmers and gardeners correspond and support one another regularly via Facebook. In times of hardship such as in the wake of Typhoon Haiyan or 'Yolanda' in the Philippines, networks like this one are a lifeline for financial and social support and continued collective practice. This thesis shows that research is a performative act with material affects. Performing hybrid collective methods and ethics offers one way to cultivate new food and economic futures in a climate and resource changing world.
Trading the System Efficiency for the Income Equality of Drivers in Rideshare
Creators: name: Xu, Yifan
name: Xu, Pan
Publisher: name: arXiv
Year: 2020
Subjects: subject: Artificial Intelligence (cs.AI)
subject: Data Structures and Algorithms (cs.DS)
subject: FOS: Computer and information sciences

description: Several scientific studies have reported the existence of the income gap among rideshare drivers based on demographic factors such as gender, age, race, etc. In this paper, we study the income inequality among rideshare drivers due to discriminative cancellations from riders, and the tradeoff between the income inequality (called fairness objective) with the system efficiency (called profit objective). We proposed an online bipartite-matching model where riders are assumed to arrive sequentially following a distribution known in advance. The highlight of our model is the concept of acceptance rate between any pair of driver-rider types, where types are defined based on demographic factors. Specially, we assume each rider can accept or cancel the driver assigned to her, each occurs with a certain probability which reflects the acceptance degree from the rider type towards the driver type. We construct a bi-objective linear program as a valid benchmark and propose two LP-based parameterized online algorithms. Rigorous online competitive ratio analysis is offered to demonstrate the flexibility and efficiency of our online algorithms in balancing the two conflicting goals, promotions of fairness and profit. Experimental results on a real-world dataset are provided as well, which confirm our theoretical predictions.
description: Accepted by IJCAI2020 (http://static.ijcai.org/2020-accepted_papers.html) and SOLE copyright holder is IJCAI (International Joint Conferences on Artificial Intelligence), all rights reserved
A stability result for the Steklov Laplacian Eigenvalue Problem with a spherical obstacle
Creators: name: Paoli, Gloria
name: Piscitelli, Gianpaolo
name: Sannipoli, Rossano
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 28A75, 35J25, 35P15

description: In this paper we study the first Steklov-Laplacian eigenvalue with an internal fixed spherichal obstacle. We prove that the spherical shell locally maximizes the first eigenvalue among nearly spherical sets when both the internal ball and the volume are fixed.
An open-access clicker question bank for numerical analysis
Creators: name: Hossain, M. Alamgir
name: Menz, Petra M.
name: Stockie, John M.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Physics Education (physics.ed-ph)
subject: Numerical Analysis (math.NA)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: 65-01, 97Nxx

description: We present a question bank consisting of over 250 multiple-choice and true-false questions covering a broad range of material typically taught in an introductory undergraduate course in numerical analysis or scientific computing. The questions are ideal for polling students during lectures by means of a student response system that uses clicker remotes or smartphones running a suitable app. We describe our experiences implementing these clicker questions in a recent class and provide evidence of their effectiveness in terms of testing students' prior knowledge, gauging understanding of new material, increasing participation, and especially improving student satisfaction. Our conclusions are supported by a mid-semester student survey as well as anecdotal observations. The question bank has been released as an open-access educational resource under a Creative Commons license (BY-NC-SA) for free use by the mathematics community.
LeMoMaF: Lensed Mock Map Facility
Creators: name: Forero-Romero, Jaime E.
name: Blaizot, Jeremy
name: Devriendt, Julien
name: Van Waerbeke, Ludovic
name: Guiderdoni, Bruno
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present the Lensed Mock Map Facility (LeMoMaF), a tool designed to perform mock weak lensing measurements on numerically simulated chunks of the universe. Coupling N-body simulations to a semi-analytical model of galaxy formation, LeMoMaF can create realistic lensed images and mock catalogues of galaxies, at wavelengths ranging from the UV to the submm. To demonstrate the power of such a tool we compute predictions of the source-lens clustering effect on the convergence statistics, and quantify the impact of weak lensing on galaxy counts in two different filters. We find that the source-lens clustering effect skews the probability density function of the convergence towards low values, with an intensity which strongly depends on the redshift distribution of galaxies. On the other hand, the degree of enhancement or depletion in galaxy counts due to weak lensing is independent of the source-lens clustering effect. We discuss the impact on the two-points shear statistics to be measured by future missions like SNAP and LSST. The source-lens clustering effect would bias the estimation of sigma_8 from two point statistics by 2% -5%. We conclude that accurate photometric redshifts for individual galaxies are necessary in order to quantify and isolate the source-lens clustering effect.
description: 14 pages, 11 figures, submitted to MNRAS
Gravi-Leptogenesis: Leptogenesis from Gravity Waves in Pseudo-scalar Driven Inflation Models
Creators: name: Alexander, S. H.
name: Peskin, M.
name: Sheikh-Jabbari, M. M.
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this talk we present a mechanism for leptogenesis which is based on gravity waves produced during inflation. We show that when inflation is driven by a pseudo-scalar field the metric perturbations generated during inflation can become birefringent, therefore giving a non-vanishing contribution to the gravitational triangle anomaly and sourcing lepton anti-lepton asymmetry. As this asymmetry is sourced by the fields which are active during inflation, it is not washed out or diluted by inflation. The amount of matter asymmetry generated in our model can be of realistic size for the parameters within the range of some inflationary scenarios and grand unified theories. This talk is based on Ref.[1] which has appeared on the arXiv as hep-th/0403069.
description: 8 pages, Presented by M.M. Sh-J. at IPM School and Conference on Lepton and Hadron Physics (IPM-LHP06), Tehran, Iran; v2: A computational error corrected
The Ryukyuan emigration program to Bolivia as a cold war policy
Creators: name: Iacobelli, Pedro D
Publisher: name: The Australian National University
Year: 2018
Subjects: subject: DS895.R98 I23 2010
subject: Ryukyu Islands History 1945-1972
subject: Okinawa Island (Japan) History 20th century
subject: Ryukyu Islands Emigration and immigration Bolivia
subject: United States Foreign relations Japan Ryukyu Islands
subject: Ryukyu Islands Foreign relations United States

description: This study deals with Cold War Okinawa and the genesis of the emigration program that was organised by the U.S. military during the 1950s. As result of the postwar agreements with Japan, the United States occupied the Ryukyu Islands and began to build a series of military complexes in the Island. The emigrational movement from Okinawa to Bolivia was part of a security policy planned by the U.S. authorities to maintain social and political stability in the Ryukyu Islands. Therefore, the study of the Okinawan emigration program in the 1950s highlights the fact that security considerations may play an important part in migration, and thus that both sender and receiver states may play a major role in international migration. The Ryukyuan emigration program is analyzed utilizing the Hegemonic Stability Theory since it can be applied to the relation between the world's hegemonic nation and international migration. The selection of Bolivia as the first hosting country is also studied since the U.S. authorities tried not only to put forward security policies in Okinawa but also assist friendly governments.
Bundle methods for regularized risk minimization with applications to robust learning
Creators: name: Teo, Choon-Hui
Publisher: name: The Australian National University
Year: 2018
Subjects: subject: Q325.5.T46 2010
subject: Supervised learning (Machine learning)
subject: Risk management
subject: Algorithms

description: Supervised learning in general and regularized risk minimization in particular is about solving optimization problem which is jointly defined by a performance measure and a set of labeled training examples. The outcome of learning, a model, is then used mainly for predicting the labels for unlabeled examples in the testing environment. In real-world scenarios: a typical learning process often involves solving a sequence of similar problems with different parameters before a final model is identified. For learning to be successful, the final model must be produced timely, and the model should be robust to (mild) irregularities in the testing environment. The purpose of this thesis is to investigate ways to speed up the learning process and improve the robustness of the learned model. We first develop a batch convex optimization solver specialized to the regularized risk minimization based on standard bundle methods. The solver inherits two main properties of the standard bundle methods. Firstly, it is capable of solving both differentiable and non-differentiable problems, hence its implementation can be reused for different tasks with minimal modification. Secondly, the optimization is easily amenable to parallel and distributed computation settings; this makes the solver highly scalable in the number of training examples. However, unlike the standard bundle methods, the solver does not have extra parameters which need careful tuning. Furthermore, we prove that the solver has faster convergence rate. In addition to that, the solver is very efficient in computing approximate regularization path and model selection. We also present a convex risk formulation for incorporating invariances and prior knowledge into the learning problem. This formulation generalizes many existing approaches for robust learning in the setting of insufficient or noisy training examples and covariate shift. Lastly, we extend a non-convex risk formulation for binary classification to structured prediction. Empirical results show that the model obtained with this risk formulation is robust to outliers in the training examples.
An optimal bound for nonlinear eigenvalues and torsional rigidity on domains with holes
Creators: name: Della Pietra, Francesco
name: Piscitelli, Gianpaolo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: In this paper we prove an optimal upper bound for the first eigenvalue of a Robin-Neumann boundary value problem for the p-Laplacian operator in domains with convex holes. An analogous estimate is obtained for the corresponding torsional rigidity problem.
Transitive Group Actions: (IM)PRIMITIVITY and Semiregular Subgroups
Creators: name: Kovacs, Istvan
name: Malnic, Aleksander
name: Marusic, Dragan
name: Miklavic, Stefko
Publisher: name: arXiv
Year: 2007
Subjects: subject: Group Theory (math.GR)
subject: Combinatorics (math.CO)
subject: FOS: Mathematics
subject: 05C25, 16W22

description: The following problem is considered: if $H$ is a semiregular abelian subgroup of a transitive permutation group $G$ acting on a finite set $X$, find conditions for (non) existence of $G$-invariant partitions of $X$. Conditions presented in this paper are derived by studying spectral properties of associated $G$-invariant digraphs. As an essential tool, irreducible complex characters of $H$ are used. Questions of this kind arise naturally when classifying combinatorial objects which enjoy a certain degree of symmetry. As an illustration, a new and short proof of an old result of Frucht, Graver and Watkins ({\it Proc. Camb. Phil. Soc.}, {\bf 70} (1971), 211-218) classifying edge-transitive generalized Petersen graphs, is given.
description: 18 pages, 0 figures
The charmed string: self-supporting loops through air drag
Creators: name: Daerr, Adrian
name: Courson, Juliette
name: Abello, Margaux
name: Toutain, Wladimir
name: Andreotti, Bruno
Publisher: name: arXiv
Year: 2020
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: The string shooter experiment uses counter-rotating pulleys to propel a closed string forward. Its steady state exhibits a transition from a gravity dominated regime at low velocity towards a high velocity regime where the string takes the form of a self-supporting loop. Here we show that this loop of light string is not suspended in the air due to inertia, but through the hydrodynamic drag exerted by the surrounding fluid, namely air. We investigate this drag experimentally and theoretically for a smooth long cylinder moving along its axis. We then derive the equations describing the shape of the string loop in the limit of vanishing string radius. The solutions present a critical point, analogous to a hydraulic jump, separating a supercritical zone where the wave velocity is smaller than the rope velocity, from a subcritical zone where waves propagate faster than the rope velocity. This property could be leveraged to create a white hole analogue similar to what has been demonstrated using surface waves on a flowing fluid. Loop solutions that are regular at the critical point are derived, discussed and compared to the experiment. In the general case, however, the critical point turns out to be the locus of a sharp turn of the string, which is modelled theoretically as a discontinuity. The hydrodynamic regularisation of this geometrical singularity, which involves non-local and added mass effects, is discussed based on dimensional analysis.
description: 10 pages, 5 figures
The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds.X. The Chamaeleon II Pre-Main Sequence Population as Observed With IRAC and MIPS
Creators: name: Alcala', Juan M.
name: Spezzi, Loredana
name: Chapman, Nicholas
name: Evans, Neal J.
name: Huard, Tracy L.
name: Jorgens, Jes K.
name: Merin, Bruno
name: Stapelfel, Karl R.
name: Covino, Elvira
name: Frasca, Antonio
name: Gandolfi, Davide
name: Oliveira, Isa
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and near infrared data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population of Cha II, in a mapped area of ~1.75 square degrees, and study the spatial distribution and properties of the cloud members and candidate pre-main sequence (PMS) objects and their circumstellar matter. From the analysis of the volume density of the PMS objects and candidates we find two tight groups of objects with volume densities higher than 25 solar masses per cubic parsec and 5-10 members each. These groups correlate well in space with the regions of high extinction. A multiplicity fraction of about 13% is observed for objects with separations between 0.8" and 6.0". Using the results of masses and ages from a companion paper, we estimate the star formation efficiency to be 1-4% significantly lower than for Cha I. This might mean that different star-formation activities in the Chamaeleon clouds reflect a different history of star formation. We also find that the Cha II cloud is turning some 6-7 solar masses into stars every Myr, which is low in comparison with the star formation rate in other c2d clouds. On the other hand, the disk fraction of 70-80% that we estimate in Cha II is much higher than in other star forming regions and indicates that the population in this cloud is dominated by objects with active accretion. Finally, the Cha II outflows are discussed, with particular regard to the discovery of a new Herbig-Haro outflow, HH 939, driven by the classical T Tauri star Sz 50.
description: 80 pages, 24 figures
Imaging the body politics : the social and symbolic spaces of citizenship in Maxwell’s History of the Irish Rebellion
Creators: name: Mewburn, Charity Elizabeth
Publisher: name: University of British Columbia
Year: 2009

description: This thesis examines a particular and highly contested representation of Irishness in relation to the national polity that circulated in mid-nineteenth century Britain and continued to enjoy currency through altered readings during the remainder of the century. The focus for this study is William Hamilton Maxwell's History of the Irish Rebellion in 1798: with Memoirs of the Union and Emmett's Insurrection in 1803. Issued in serial form beginning in 1844, with illustrations by artist and caricaturist George Cruikshank, the work was published as a bound volume in 1845. The partnership on this project of a popular writer known primarily for the publication of gentlemen's adventures and amateur histories of British military exploits in the Napoleonic Wars, together with the artist Cruikshank, the celebrated London illustrator of, among other works, Charles Dickens' Oliver Twist, suggests an unusual approach to the representation of so-called "serious" history. This thesis explores the complex set of factors that gave the History of the Irish Rebellion its particular verbal and visual form. These include: the innovative and unconventional publishing and marketing strategies associated with the initial issuing of the work as an illustrated serial; mid-century debates over predominantly Catholic Irish calls for repeal of the Union forged in 1800 between Ireland and Britain; and current anxieties about working-class agitation around issues of representation and franchise. In particular, this study focusses on Cruikshank's twenty-one illustrations for Maxwell's work, assessing their rhetorical strategies both in relation to the text's concern with Ireland, both historically and in the present, and crucially, with these images' more subtle evocations of political concerns within Britain itself in the mid-1840's. I argue that by representing the Irish Catholic peasant as historic violator of the British social body, Cruikshank's illustrations, together with the text, worked to construct a particular image of responsible citizenship, one that asserted the patriarchal and classed values deemed essential to the modern nation state.
Periapsis and gravitomagnetic precessions of stellar orbits in Kerr and Kerr-de Sitter black hole spacetimes
Creators: name: Kraniotis, G. V.
Publisher: name: arXiv
Year: 2006
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: The exact solution for the motion of a test particle in a non-spherical polar orbit around a Kerr black hole is derived. Exact novel expressions for frame dragging (Lense-Thirring effect), periapsis advance and the orbital period are produced. The resulting formulae, are expressed in terms of Appell's first hypergeometric function $F_1$, Jacobi's amplitude function, and Appell's $F_1$ and Gau$ß$ hypergeometric function respectively. The exact expression for frame dragging is applied for the calculation of the Lense-Thirring effect for the orbits of S-stars in the central arcsecond of our Galaxy assuming that the galactic centre is a Kerr black hole, for various values of the Kerr parameter including those supported by recent observations. In addition, we apply our solutions for the calculation of frame dragging and periapsis advance for stellar non-spherical polar orbits in regions of strong gravitational field close to the event horizon of the galactic black hole, e.g. for orbits in the central milliarcsecond of our galaxy. Such orbits are the target of the GRAVITY experiment. We provide examples with orbital periods in the range of 100min - 54 days. Detection of such stellar orbits will allow the possibility of measuring the relativistic effect of periapsis advance with high precision at the strong field realm of general relativity. Further, an exact expression for the orbital period of a test particle in a non-circular equatorial motion around a Kerr black hole is produced. We also derive exact expressions for the periapsis advance and the orbital period for a test particle in a non-circular equatorial motion in the Kerr field in the presence of the cosmological constant in terms of Lauricella's fourth hypergeometric function $F_D$.
description: LaTeX file, 46 pages, typos fixed, substantial changes, version published in Classical and Quantum Gravity, Vol 24 (2007) 1775-1808
Monotonicity Principle in Tomography of Nonlinear Conducting Materials
Creators: name: Esposito, Antonio Corbo
name: Faella, Luisa
name: Piscitelli, Gianpaolo
name: Prakash, Ravi
name: Tamburrino, Antonello
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35R30, 35J60

description: We treat an inverse electrical conductivity problem which deals with the reconstruction of nonlinear electrical conductivity starting from boundary measurements in steady currents operations. In this framework, a key role is played by the Monotonicity Principle, which establishes a monotonic relation connecting the unknown material property to the (measured) Dirichlet-to-Neumann operator (DtN). Monotonicity Principles are the foundation for a class of non-iterative and real-time imaging methods and algorithms. In this article, we prove that the Monotonicity Principle for the Dirichlet Energy in nonlinear problems holds under mild assumptions. Then, we show that apart from linear and $p$-Laplacian cases, it is impossible to transfer this Monotonicity result from the Dirichlet Energy to the DtN operator. To overcome this issue, we introduce a new boundary operator, identified as an Average DtN operator.
description: 28 pages, 6 figures
A nonlocal anisotropic eigenvalue problem
Creators: name: Piscitelli, Gianpaolo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35P15, 49R50

description: We determine the shape which minimizes, among domains with given measure, the first eigenvalue of the anisotropic laplacian perturbed by an integral of the unknown function. Using also some properties related to the associated \lq\lq twisted\rq\rq problem, we show that, this problem displays a \emph{saturation} phenomenon: the first eigenvalue increases with the weight up to a critical value and then remains constant.
description: 18 pages
Association schemes related to universally optimal configurations, Kerdock codes and extremal Euclidean line-sets
Creators: name: Abdukhalikov, Kanat
name: Bannai, Eiichi
name: Suda, Sho
Publisher: name: arXiv
Year: 2008
Subjects: subject: Combinatorics (math.CO)
subject: General Mathematics (math.GM)
subject: FOS: Mathematics
subject: 05E30, 94B60, 51M15, 11H06

description: H. Cohn et. al. proposed an association scheme of 64 points in R^{14} which is conjectured to be a universally optimal code. We show that this scheme has a generalization in terms of Kerdock codes, as well as in terms of maximal real mutually unbiased bases. These schemes also related to extremal line-sets in Euclidean spaces and Barnes-Wall lattices. D. de Caen and E. R. van Dam constructed two infinite series of formally dual 3-class association schemes. We explain this formal duality by constructing two dual abelian schemes related to quaternary linear Kerdock and Preparata codes.
description: 16 pages
Dispersion Relation Preserving FD Schemes and Self-Affine DG Elements
Creators: name: Williams, Christopher
Publisher: name: The Australian National University
Year: 2021

description: The two primary directions of research in computational hyperbolic PDE are resolving high-frequency wave modes and computation in complex geometries. In this thesis, we make progress in both of these directions with regard to computation and theory.\\ First, to resolve high frequencies we introduce upwind dispersion preserving differential operator pairs. We prove for complex curvilinear geometries that general summation-by-parts dual pairings are numerically stable and provide an analysis of errors for large-scale wave propagation and dynamic rupture simulations. We find that numerical dispersion errors can completely destroy the numerical solution for dynamic rupture problems when computed with odd order SBP dual pairings, some of which worsen with grid refinement. To overcome this error we construct dispersion relation preserving schemes whose maximal dispersion error is $<5\%$. This improves on existing central stencil difference operators that have a maximal relative dispersion error of $100\%$. We prove that in 3 dimensions for time-dependent PDE our stencils require $\approx 4 \%$ of the computational effort needed to resolve high-frequency waves on a given computational grid compared to traditional operators. Our newly derived operators are efficiently implemented in the large-scale wave simulation software Wave-Qlab-3D, and numerical results are provided. Second, we give the theoretical details of how to construct fractal finite elements which can be used for Discontinuous Galerkin (DG) schemes. Such elements provide a step towards the accurate simulation of wave-propagation along self-affine boundaries, contributing to simulation in complex geometries. We build off a method for approximating a non-differentiable self-affine surface with a self-affine function in a weak sense to form our scheme. We then give efficient and stable algorithms to compute the integrals of polynomials over such domains, and also compute orthonormal polynomial basis functions, which completes the theory for the interior of the element. For the element boundary, we show that the weak derivatives of refractable self-affine curves exist and can be computed efficiently. Results from geometric measure theory guarantee that the integration-by-parts formula holds for such boundaries and our elements fit within the summation-by-parts framework. Our algorithms then extend to both random fractals and graph-directed Iterated Function Systems.
Frobenius-Witt differentials and regularity
Creators: name: Saito, Takeshi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Algebraic Geometry (math.AG)
subject: Commutative Algebra (math.AC)
subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 13N05, 13H05, 14F10

description: T. Dupuy, E. Katz, J. Rabinoff, D. Zureick-Brown introduced the module of total $p$-differentials for a ring over $Z/p^2Z$. We study the same construction for a ring over $Z_{(p)}$ and prove a regularity criterion. For a local ring, the tensor product with the residue field is constructed in a different way by O. Gabber, L. Ramero. In another article arXiv:2006.00448, we use the sheaf of FW-differentials to define the cotangent bundle and the micro-support of an etale sheaf.
description: 22 pages. In v2, schemes are not used except in the last section. Earlier overlap in arXiv:2006.00448 is removed. An error in Lemma 1.3 pointed out by A. Mathew is corrected in v5
Non-symmetric spin-pumping in a multiferroic heterostructure
Creators: name: Rovillain, Pauline
name: de Oliveira, Ronei Cardoso
name: Marangolo, Massimiliano
name: Duquesne, Jean-Yves
Publisher: name: arXiv
Year: 2020
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We present spin pumping experiments in Co/Pt bilayers grown on Al2O3(0001) and on ferroelectric Y-cut LiNbO3 substrates. Spin pumping is triggered by resonant ferromagnetic resonance induced by surface acoustic waves. We observe that spin pumping efficiency varies when both the magnetization vector and the acoustic wave vector are reversed in Pt/Co/LiNbO3. This phenomenon is not observed in Pt/Co/Al2O3. We propose that the in-plane electric polarization of LiNbO3 is at the origin of the observed phenomenon. These observations open up the perspective of an electric field control of spin pumping efficiency.
Forces in Kerr spacetimes with a repulsive cosmological constant
Creators: name: Kovar, Jiri
name: Stuchlik, Zdenek
Publisher: name: arXiv
Year: 2006
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Forces defined in the framework of optical reference geometry are introduced in the case of stationary and axially symmetric Kerr black-hole and naked-singularity spacetimes with a repulsive cosmological constant. Properties of the forces acting on test particles moving along circular orbits in the equatorial plane are discussed, whereas it is shown where the gravitational force vanishes and changes its orientation and where the centrifugal force vanishes and changes its orientation independently of the velocity of test particles related to the optical geometry; the Coriolis force does not vanish for the velocity being non-zero. The spacetimes are classified according to the number of circular orbits where the gravitational and centrifugal forces vanish.
Hansenocaris undetermined
Creators: name: Olesen, Jørgen
name: Grygier, Mark J.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Maxillopoda
Hansenocarididae
Hansenocaris
Hansenocaris undetermined

description: Y-nauplius Type B
Figs 2, 7H–M
Type B – Dreyer et al. 2023a: figs 2, 5a, c, tables s1–s2.
Material examined
JAPAN – Okinawa, Sesoko I., laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 1 LSN; 1991–2005 • 3 LSN, 1 of which molted to cyprid; 2018–2019 (Tables 1 and S1).
Description
LAST-STAGE NAUPLIUS (LSN). Lecithotrophic. Body ovate in dorso-ventral view; about twice as long as wide; lateral margins tapering gradually towards caudal end with no discontinuity at posterior end of cephalic shield. Dorsum evenly curved in lateral view, with trunk axis downturned 50–55° relative to cephalic axis. Length 250–265 µm (without dorso-caudal spine), 275 µm in lateral view following body curvature; greatest width 160 µm and greatest dorso-ventral thickness 70–75 µm. Labrum weakly elevated, sub-quadrangular, approximately as long as wide; surface not divided into facets by cuticular ridges; pore pattern not examined in detail. Caudal end narrowly truncate, terminating in short (12 µm), triangular dorso-caudal spine positioned unusually far anteriorly on dorsal side and pair of longer (20 µm), narrow, sharply pointed, slightly upcurved and diverging furcal spines.
CYPRID VIEWED THROUGH CUTICLE OF LSN. Body practically unpigmented, although naupliar appendages weakly brownish. Gut-like tube packed with orange-brown yolk granules. Telson small, wider than long, significantly shorter than half of thorax length.
Identification and variation
Easily recognizable by its unusually forward-positioned dorso-caudal spine, evenly curved (in lateral view) body and broadly triangular ventral trunk region. No distinct variation was apparent among the few examined specimens.
Distribution
Japan (Sesoko Island, Okinawa).
description: Published as part of Olesen, Jørgen & Grygier, Mark J., 2024, Taxonomic diversity of marine planktonic ' y-larvae' (Crustacea: Facetotecta) from a coral reef hotspot locality (Japan, Okinawa), with a key to y-nauplii, pp. 1-90 in European Journal of Taxonomy 929 (1) on pages 20-21, DOI: 10.5852/ejt.2024.929.2479, http://zenodo.org/record/10876286
Induced differential characters on nonlinear Graßmannians
Creators: name: Diez, Tobias
name: Janssens, Bas
name: Neeb, Karl-Hermann
name: Vizman, Cornelia
Publisher: name: arXiv
Year: 2020
Subjects: subject: Differential Geometry (math.DG)
subject: Mathematical Physics (math-ph)
subject: Symplectic Geometry (math.SG)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 53D50, 53D20, 58D10, 58D05

description: Using a nonlinear version of the tautological bundle over Graßmannians, we construct a transgression map for differential characters from $M$ to the nonlinear Graßmannians $\mathrm{Gr}^S(M)$ of submanifolds of $M$ of a fixed type $S$. In particular, we obtain prequantum circle bundles of the nonlinear Graßmannian endowed with the Marsden-Weinstein symplectic form. The associated Kostant-Souriau prequantum extension yields central Lie group extensions of a group of volume-preserving diffeomorphisms integrating Lichnerowicz cocycles.
Rigidity and Flexibility of Isometric Extensions
Creators: name: Cao, Wentao
name: Inauen, Dominik
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 53B20, 53A07, 57R40, 35F60, 58B20

description: In this paper we consider the rigidity and flexibility of $C^{1, θ}$ isometric extensions and we show that the Hölder exponent $θ_0=\frac12$ is critical in the following sense: if $u\in C^{1,θ}$ is an isometric extension of a smooth isometric embedding of a codimension one submanifold $Σ$ and $θ> \frac12$, then the tangential connection agrees with the Levi-Civita connection along $Σ$. On the other hand, for any $θ<\frac12$ we can construct $C^{1,θ}$ isometric extensions via convex integration which violate such property. As a byproduct we get moreover an existence theorem for $C^{1, θ}$ isometric embeddings, $θ<\frac12$, of compact Riemannian manifolds with $C^1$ metrics and sharper amount of codimension.
description: 36 pages
Global decomposition of a Lorentzian manifold as a Generalized Robertson-Walker space
Creators: name: Gutierrez, Manuel
name: Olea, Benjamin
Publisher: name: arXiv
Year: 2007
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 53C50, 53C80

description: Generalized Robertson-Walker (GRW) spaces constitute a quite important family in Lorentzian geometry, and it is an interesting question to know whether a Lorentzian manifold can be decomposed in such a way. It is well known that the existence of a suitable vector field guaranties the local decomposition of the manifold. In this paper, we give conditions on the curvature which ensure a global decomposition and apply them to several situations where local decomposition appears naturally. We also study the uniqueness question, obtaining that the de Sitter spaces are the only non trivial complete Lorentzian manifolds with more than one GRW decomposition. Moreover, we show that the Friedmann Cosmological Models admit an unique GRW decomposition, even locally.
Spontaneous conversation; vocabulary for furniture and body parts
Creators: name: Intanai, Thongwilai
name: Thawichart, Samrij
name: Lau-Preechathammarach, Raksit Tyler
Publisher: name: California Language Archive, University of California, Berkeley
Year: 2023
Subjects: subject: kdt

description: Recorder: Zoom H4n. Microphone: internal.
Filtering, averaging and scale dependency in homogeneous variable density turbulence
Creators: name: Saenz, J. A.
name: Aslangil, D.
name: Livescu, D.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We investigate relationships between statistics obtained from filtering and from ensemble or Reynolds-averaging turbulence flow fields as a function of length scale. Generalized central moments in the filtering approach are expressed as inner products of generalized fluctuating quantities, $q'(ξ,x)=q(ξ)-\overline q(x)$, representing fluctuations of a field $q(ξ)$, at any point $ξ$, with respect to its filtered value at $x$. For positive-definite filter kernels, these expressions provide a scale-resolving framework, with statistics and realizability conditions at any length scale. In the small-scale limit, scale-resolving statistics become zero. In the large-scale limit, scale-resolving statistics and realizability conditions are the same as in the Reynolds-averaged description. Using direct numerical simulations (DNS) of homogeneous variable density turbulence, we diagnose Reynolds stresses, $\mathcal{T}_{ij}$, resolved kinetic energy, $k_r$, turbulent mass-flux velocity, $a_i$, and density-specific volume covariance, $b$, defined in the scale-resolving framework. These variables, and terms in their governing equations, vary smoothly between zero and their Reynolds-averaged definitions at the small and large scale limits, respectively. At intermediate scales, the governing equations exhibit interactions between terms that are not active in the Reynolds-averaged limit. For example, in the Reynolds-averaged limit, $b$ follows a decaying process driven by a destruction term; at intermediate length scales it is a balance between production, redistribution, destruction, and transport, where $b$ grows as the density spectrum develops, and then decays when mixing becomes strong enough. This work supports the notion of a generalized, length-scale adaptive model that converges to DNS at high resolutions, and to Reynolds-averaged statistics at coarse resolutions.
The Monotonicity Principle for Magnetic Induction Tomography
Creators: name: Tamburrino, Antonello
name: Piscitelli, Gianpaolo
name: Zhou, Zhengfang
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 34K29, 35R30, 45Q05, 47A75, 78A46

description: The inverse problem treated in this article consists in reconstructing the electrical conductivity from the free response of the system in the magneto-quasi-stationary (MQS) limit. The MQS limit corresponds to a diffusion PDE. In this framework, a key role is played by the Monotonicity Principle, that is a monotone relation connecting the unknown material property to the (measured) free-response. MP is relevant as basis of noniterative and real-time imaging methods. Monotonicity Principles have been found in many different physical problems governed by PDEs of different nature. Despite its rather general nature, each different physical/mathematical context requires to discover the proper operator showing MP. For doing this, it is necessary to develop ad-hoc mathematical approaches tailored on the specific framework. In this article, we prove a monotonic relationship between the electrical resistivity and the time constants characterizing the free-response for MQS systems. The key result is the representation of the induced current density through a modal representation. The main result is based on the analysis of an elliptic eigenvalue problem, obtained from separation of variables.
description: 25 pages, 4 figures