IA Scholar Query: A Steiner Tree Associated with Three Quarks.
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgFri, 21 Oct 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440The reaction π N →ω N in a dynamical coupled-channel approach
https://scholar.archive.org/work/7dqzxfmktvfx5kpbazns66toge
A refined investigation on light flavor meson-baryon scatterings is performed using a dynamical coupled-channel approach, the Jülich-Bonn model, that respects unitartiy and analyticity constraints. The channel space of π N, πΔ, σ N, ρ N, η N, K Λ and K Σ is extended by adding the ω N final state. The spectra of N^* and Δ resonances are extracted in terms of complex poles of the scattering amplitudes, based on the result of a global fit to a worldwide collection of data, in the energy region from the π N threshold to center-of-mass energy z=2.3 GeV. A negative value of the ω N elastic spin-averaged scattering length is extracted, questioning the existence of bound states of the ω meson in the nuclear matter.Yu-Fei Wang, Deborah Rönchen, Ulf-G. Meißner, Yu Lu, Chao-Wei Shen, Jia-Jun Wuwork_7dqzxfmktvfx5kpbazns66togeFri, 21 Oct 2022 00:00:00 GMTDetection and Evaluation of Clusters within Sequential Data
https://scholar.archive.org/work/bue3nywa3nbqffglua55yjgbd4
Motivated by theoretical advancements in dimensionality reduction techniques we use a recent model, called Block Markov Chains, to conduct a practical study of clustering in real-world sequential data. Clustering algorithms for Block Markov Chains possess theoretical optimality guarantees and can be deployed in sparse data regimes. Despite these favorable theoretical properties, a thorough evaluation of these algorithms in realistic settings has been lacking. We address this issue and investigate the suitability of these clustering algorithms in exploratory data analysis of real-world sequential data. In particular, our sequential data is derived from human DNA, written text, animal movement data and financial markets. In order to evaluate the determined clusters, and the associated Block Markov Chain model, we further develop a set of evaluation tools. These tools include benchmarking, spectral noise analysis and statistical model selection tools. An efficient implementation of the clustering algorithm and the new evaluation tools is made available together with this paper. Practical challenges associated to real-world data are encountered and discussed. It is ultimately found that the Block Markov Chain model assumption, together with the tools developed here, can indeed produce meaningful insights in exploratory data analyses despite the complexity and sparsity of real-world data.Alexander Van Werde, Albert Senen-Cerda, Gianluca Kosmella, Jaron Sanderswork_bue3nywa3nbqffglua55yjgbd4Tue, 04 Oct 2022 00:00:00 GMTElastic nucleon-pion scattering at m_π = 200 MeV from lattice QCD
https://scholar.archive.org/work/4t4nkkhs2zfsjga2wdyc5erl7m
Elastic nucleon-pion scattering amplitudes are computed using lattice QCD on a single ensemble of gauge field configurations with N_ f = 2+1 dynamical quark flavors and m_π = 200 MeV. The s-wave scattering lengths with both total isospins I=1/2 and I=3/2 are inferred from the finite-volume spectrum below the inelastic threshold together with the I=3/2 p-wave containing the Δ(1232) resonance. The amplitudes are well-described by the effective range expansion with parameters constrained by fits to the finite-volume energy levels enabling a determination of the I=3/2 scattering length with statistical errors below 5%, while the I = 1/2 is somewhat less precise. Systematic errors due to excited states and the influence of higher partial waves are controlled, providing a pathway for future computations down to the physical light quark masses with multiple lattice spacings and physical volumes.John Bulava, Andrew D. Hanlon, Ben Hörz, Colin Morningstar, Amy Nicholson, Fernando Romero-López, Sarah Skinner, Pavlos Vranas, André Walker-Loudwork_4t4nkkhs2zfsjga2wdyc5erl7mMon, 29 Aug 2022 00:00:00 GMTTetraquarks: relativistic corrections and other issues
https://scholar.archive.org/work/izcsrbwlezazdo5pkaky2kbmya
We discuss the effect of relativistic kinematics on the binding energy of multiquark states. For a given potential, the use of relativistic kinematics lowers the energy by a larger amount for the threshold made of two mesons than for a tetraquark, so that its binding is weakened. Some other issues associated with exotic hadrons are also briefly discussed.Jean Marc Richard, Alfredo Valcarce, Javier Vijandework_izcsrbwlezazdo5pkaky2kbmyaMon, 22 Aug 2022 00:00:00 GMTNeutron stars: The journey from birth to death
https://scholar.archive.org/work/tvcvq4zlqjh5pmqgfv4ybod7ba
This paper contains the synopsis of my three lectures given at the XV International Workshop on Hadron Physics.The first lecture covers introduction to the general life cycle of stars and the origin of compact objects, followed by the history of neutron stars discovery and their macroscopic features together with a survey of the latest astrophysical observation techniques. The second lecture is devoted to macroscopic and microscopic nuclear physics models of the equation of state governing the cold neutron stars. A special attention is paid to the Quark-Meson-Coupling model, an effective relativistic mean-field model in which the forces between individual baryons are self-consistently mediated by exchange of virtual mesons between the valence quarks in the baryons. In the third lecture (i) similarities and differences between dense matter created in heavy ion collisions and the cores of neutron stars, (ii) gravitational waves from binary neutron star merges and (iii) the impact of data in the multimessenger era on deeper understanding of neutron star interiors are discussed.Jirina R. Stonework_tvcvq4zlqjh5pmqgfv4ybod7baMon, 01 Aug 2022 00:00:00 GMTWhat has been learnt from the analysis of the low-energy pion-nucleon data during the past three decades?
https://scholar.archive.org/work/yk3cad5hqvdznkddw3k4td4oze
Over twenty-five years ago, two analyses of the pion-nucleon (π N) data at low energy (i.e., for pion laboratory kinetic energy T ≤ 100 MeV) reported on the departure of the extracted scattering amplitudes, corresponding to the two elastic-scattering reactions π^± p →π^± p and to the π^- p charge-exchange reaction π^- p →π^0 n, from the triangle identity, which these amplitudes fulfil if the isospin invariance holds in the hadronic part of the π N interaction. This discrepancy indicates that at least one of the following assumptions is not valid: first, that the absolute normalisation of the bulk of the low-energy π N datasets is correct; second, that any residual contributions to the corrections, which aim at the removal of the effects of electromagnetic (EM) origin from the measurements, are not significant; and third, that the isospin invariance holds in the hadronic part of the π N interaction. In view of the incompatibility of the results of the various schemes of removal of the so-called trivial EM effects at the π N threshold (T = 0 MeV), the likelihood of residual effects of EM origin in the extracted π N scattering amplitudes (from the data in the scattering region, i.e., above the π N threshold) must be reassessed. This work emphasises the importance of the development of a unified scheme for the determination of reliable EM corrections, applicable at the π N threshold and in the scattering region, in providing a resolution to the established discrepancy at low energy.Evangelos Matsinoswork_yk3cad5hqvdznkddw3k4td4ozeSun, 05 Jun 2022 00:00:00 GMTThe Strange Physics of Dark Baryons
https://scholar.archive.org/work/ihmnvje3tjdtzmfzl6ou3zvi2m
Dark sector particles at the GeV scale carrying baryon number provide an attractive framework for understanding the origin of dark matter and the matter-antimatter asymmetry of the universe. We demonstrate that dark decays of hadronic states containing strange quarks -- hyperons -- offer excellent prospects for discovering such dark baryons. Building up on novel calculations of the matrix elements relevant for hyperon dark decays, and in view of various collider, flavor, and astrophysical constraints, we determine the expected rates at hyperon factories like BESIII and LHCb. We also highlight the interesting theoretical connections of hyperon dark decays to the neutron lifetime anomaly and Mesogenesis.Gonzalo Alonso-Álvarez, Gilly Elor, Miguel Escudero, Bartosz Fornal, Benjamín Grinstein, Jorge Martin Camalichwork_ihmnvje3tjdtzmfzl6ou3zvi2mThu, 02 Jun 2022 00:00:00 GMTThe (im)materiality of Goethe's geology
https://scholar.archive.org/work/7e72oopi5bh5hd52lnkcbirv4q
My PhD project explores Goethe's writings on geology from the perspective of the interplay between materiality and immateriality. Specifically, I posit that Goethe's descriptions of mountains, mines and rocks focus in equal part on the material and immaterial characteristics of the object in question, without privileging one or the other. Drawing on Goethe's presentation of the role of the imagination in geological enquiry, his belief in the existence of generative forces within geological masses and his colour theory, inter alia, I demonstrate that Goethe's geological writings are shaped by the monist duality of (im)materiality. I explore this hypothesis with reference to Goethe's engagement with the project to reopen the mine at Ilmenau, which was a deeply formative experience for the development of his geological theories. My thesis makes a contribution to two separate fields of enquiry. Firstly, within the sphere of Goethe studies, it sheds light on Goethe's geological work in general, which has been greatly under-researched compared to his endeavours in other scientific fields. In so doing, it also seeks to being together the arguments pursued by many critics to date, who have primarily focused on either the material or the immaterial in Goethe's work, without attempting to create a synthesis of both. Secondly, it also represents a new avenue of enquiry for the burgeoning field of immateriality studies, which has primarily focused on disciplines such as anthropology and archaeology to date. In light of Goethe's explicit emphasis on holism in his studies of the natural sciences, I contend that research on his geological writings (and, indeed, on the rest of his scientific output) should approach questions of materiality and immateriality with an eye to the same holism. In so doing, this paints a detailed picture both of Goethe's engagement with the issue of (im)materiality and of his understanding of the geological world.Jennifer Caisley, Apollo-University Of Cambridge Repository, Charlotte Leework_7e72oopi5bh5hd52lnkcbirv4qWed, 01 Jun 2022 00:00:00 GMTTransverse charge and current densities in the nucleon from dispersively improved chiral effective field theory
https://scholar.archive.org/work/cf2nkte4anc5bewpq4gqtdit4e
The transverse densities ρ_1, 2(b) describe the distributions of electric charge and magnetic moment at fixed light-front time and connect the nucleon's elastic form factors with its partonic structure. The dispersive representation of the form factors F_1, 2(t) expresses the densities in terms of exchanges of hadronic states in the t-channel and permits their analysis using hadronic physics methods. Purpose: Compute the densities at peripheral distances b = 𝒪(M_π^-1), where they are generated predominantly by the two-pion states in the dispersive representation. Quantify the uncertainties. Methods: Dispersively improved chiral effective field theory (DIχEFT) is used to calculate the isovector spectral functions Im F_1, 2(t) on the two-pion cut. The method includes ππ interactions (ρ resonance) through elastic unitarity and provides realistic spectral functions up to t ≈ 1 GeV^2. Higher-mass states are parametrized by effective poles and constrained by sum rules (charges, radii, superconvergence relations). The densities ρ_1, 2(b) are obtained from their dispersive representation. Uncertainties are quantified by varying the spectral functions. The method respects analyticity and ensures the correct b →∞ asymptotic behavior of the densities. Results: Accurate densities are obtained at all distances b ≳ 0.5 fm, with correct behavior down to b → 0. The region of distances is quantified where transverse nucleon structure is governed by the two-pion state. The light-front current distributions in the polarized nucleon are computed and discussed. Conclusions: Peripheral nucleon structure can be computed from first principles using DIχEFT. The method can be extended to generalized parton distributions and other nucleon form factors.J. M. Alarcón, C. Weisswork_cf2nkte4anc5bewpq4gqtdit4eMon, 25 Apr 2022 00:00:00 GMTFinding Arcadia : ecological agriculture and the art of being in community
https://scholar.archive.org/work/caoyouwjyze2lnjhit7ahaamsm
Humanity's future is dismal as long as it continues to exist devoid of community with each other and with Nature as a whole. To better observe being-in-community, this study analyzed ecological agriculture, a practice in which the well-being of the farmer is reciprocally tied to that of the land, as analogous to the more comprehensive relationship between humans and Nature. This study used photo elicitation, a method which integrates photographs by and interviews of the five participating ecological farmers, and a phenomenological lens to discern the convivially physiological art of being-in-community: listening to all voices as equal and possessing value and contribution; making room for chaos, the unexpected; learning, from a place of not-knowing; where the inevitability of impermanence is embraced, incorporated, reconstituted as a simultaneity of what was, what is, and what will be; where the quintessence, self, reconciles paradox, crystallizing diversity into the unity of community.Walter Cheatham, University, Mywork_caoyouwjyze2lnjhit7ahaamsmThu, 31 Mar 2022 00:00:00 GMTSampling statistical distributions in physics: a machine learning approach
https://scholar.archive.org/work/7zfus7pysndkvnebdkf35or33u
This thesis presents work which uses Machine Learning techniques in a variety of sampling situations which appear in physics. In the first Chapter some background on Machine Learning will be presented which will lay the foundations required for the later Chapters. Next we will look at how a specific Machine Learning model, the Restricted Boltzmann Machine, can be trained to approximate a target distribution from data which has already been sampled from the target distribution. We estimate observables on states sampled from trained models and compare them to observables estimated directly from the training data. We present a technique for estimating the likelihood function of the model using annealed importance sampling. Finally we present a closed form expression for extracting the N-point interactions which the model learns from the data directly from the parameters of the model, a result which is useful for a range of fields which study binary data. In the next Chapter we investigate a different generative model, the normalizing flow, and investigate its efficacy of generating configurations for a lattice scalar field theory. An initial study which quantifies how the cost of training this model scales with the system size is performed. Whilst the cost of training our models is significantly less than those reported in the proof of principle study which first presented using these models for this purpose [1], we discuss how there is still an exponential scaling of the training cost with the system size which must be overcome in order for these models to be practically useful. Finally we investigate inverse problems from a Bayesian perspective. With this framework, we are faced with the task of sampling from the posterior distributions in model space given the data. An approach for sampling in model space presented by the NNPDF collaboration is examined within this formal framework. We present some statistical estimators which can be used to validate a methodology which produces a sample of models. These estimato [...]Michael Wilson, University Of Edinburgh, Luigi Del Debbio, Richard Ball, Roman Zwicky, Roger Horsleywork_7zfus7pysndkvnebdkf35or33uFri, 18 Mar 2022 00:00:00 GMTNext-to-leading order scalar contributions to μ→ e conversion
https://scholar.archive.org/work/u2s2ui5kg5bm5gymrvrcg6idi4
Within a class of models in which lepton flavor violation is induced dominantly by scalar particle exchanges, we estimate the μ→ e conversion rate in several nuclei. We include next-to-leading order (NLO) terms in the one- and two-nucleon interactions in chiral effective theory, rectifying some incorrect results in the previous literature. We provide an uncertainty budget for the conversion rates and we find that NLO contributions affect the amplitudes at the level of 10%, which could be larger than the uncertainty on the leading order couplings, dominated by the strange and non-strange nucleon sigma terms. We study the implications of our results for testing Higgs-mediated CLFV in the future by combining results from various experimental searches, such as μ→ e conversion in multiple target nuclei and μ→ e γ.Vincenzo Cirigliano, Kaori Fuyuto, Michael J. Ramsey-Musolf, Evan Rulework_u2s2ui5kg5bm5gymrvrcg6idi4Thu, 17 Mar 2022 00:00:00 GMTS-wave pion condensation in symmetric nuclear matter: to be or not to be?
https://scholar.archive.org/work/jzoh4va2xbdj5jxdafwzaqotbi
S-wave pion-nucleon interactions in the linear sigma model, and in Manohar-Georgi and Gasser-Sainio-Svarc models with finite number of terms in Lagrangians, as well as in a general phenomenological approach are reviewed. Subtleties associated with the current algebra theorems and field redefinitions are discussed. In the first and third models most likely the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities, whereas within the second model it may appear already at moderate densities. In the phenomenological approach two parameterizations of the s-wave pion-nucleon scattering amplitude and the pion polarization operator used in the literature are considered. The first parameterization employs the off-mass-shell amplitude and allows to fulfil the current algebra theorems. Using it the s-wave pion polarization operator in the isospin-symmetric matter is reconstructed within the gas approximation. With this pion polarization operator the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities. Second parameterization uses the on-mass-shell pion-nucleon scattering amplitude and does not satisfy the Adler and Weinberg conditions. With such a parameterization most likely the s-wave pion condensation in the isospin-symmetric matter may occur already at the nucleon density n≃ (1.4-2.5) n_0, where n_0 is the density of the atomic nucleus, that should result in observable effects. Both parameterizations allow to successfully describe the pion atom data.D. N. Voskresenskywork_jzoh4va2xbdj5jxdafwzaqotbiWed, 19 Jan 2022 00:00:00 GMTElastic nucleon-pion scattering at $m_{\pi} \approx 200~{\rm MeV}$ from lattice QCD
https://scholar.archive.org/work/zuehef5huvaznc4j7cm33esqci
Elastic nucleon-pion scattering amplitudes are computed using lattice QCD on a single ensemble of gauge field configurations with $N_f = 2+1$ dynamical quark flavors and $m_{\pi}$ = 200 MeV. The $s$-wave scattering lengths with both total isospins $I=1/2$ and $I=3/2$ are inferred from the finite-volume spectrum below the inelastic threshold together with the $I=3/2$ $p$-wave containing the $\Delta(1232)$ resonance. The amplitudes are well-described by the effective range expansion with parameters constrained by fits to the finite-volume energy levels enabling a determination of the $I=3/2$ scattering length with statistical errors below $5\%$, while the $I = 1/2$ is somewhat less precise. Systematic errors due to excited states and the influence of higher partial waves are controlled, providing a pathway for future computations down to the physical light quark masses with multiple lattice spacings and physical volumes.John Bulava, Andrew D. Hanlon, Ben Hörz, Colin Morningstar, Amy Nicholson, Fernando Romero-López, Sarah Skinner, Pavlos Vranas, André Walker-Loudwork_zuehef5huvaznc4j7cm33esqciA realist approach to categorizing musical works
https://scholar.archive.org/work/ro5mz5fjcndlziph3yu6nlskbu
This thesis seeks to advance our comprehension of musical ontology as it pertains to realism from a platonist vantagepoint. Similar to other areas of ontological inquiry, such as fictional and mathematical objects, musical ontology is a specific field in philosophy of art that disputes the categorical nature and identity of musical objects. Much like its fictional and mathematical counterparts, categorizing works of music has been amply discussed by realists. In order to advance our understanding in this field, I will examine the categorical nature of such objects and the consequences realists face upon application. My dissertation will be separated in two distinct parts: one developing and one applying my platonist account. The first three chapters develop a certain stripe of musical realism that has previously been unexplored in the literature. In order to achieve this aim, Chapter One lays out a taxonomy of ontologies that catalogs realists, non-realists (nominalism and anti-realism), and arealist accounts. Chapters Two and Three provide two realist accounts hitherto undiscussed in the taxonomy. What makes both accounts enticing to the musical realist is that they endorse a property theory of musical works, which stands in contrast to its popular cousin, type/token theory. In particular, Chapter Two unpacks the property theory from an aristotelian perspective, while Chapter Three does so from a platonist perspective. Chapter Three provides the account that I develop and endorse. The purpose of application—contained in the last three chapters—is meant to not only show my account's implications, but also exhibit how these can render the account advantageous. Chapter Four will explain how realists should approach and contemplate the role of the musical score. Chapter Five will provide a realist response to the role of artificial intelligence in musical composition, and Chapter Four will provide a realist's modest definition of music. My goal is to showcase my account's fruitfulness in these applications, as well [...]Cody Cantabranawork_ro5mz5fjcndlziph3yu6nlskbuReimagined curatorial practice : land, labour, and community
https://scholar.archive.org/work/vcch2znu7jebngnpedvyvmg6y4
Reimagined Curatorial Practice: Land, Labour, and Community critically examines contemporary initiatives reshaping curation that move beyond western parameters of curation to offer something else. I am asking: How are curators reimagining curatorial praxis? How are curators intentionally caring for their practices to better care for those invited to contribute and for those who constitute their communities? How do these strategies replace, intervene, or work against or in conversation with settler-colonial models to establish accessible, ethical, equitable, and anti-racist spaces of art? Through experiential and archival research, I explore select curatorial models that operate in the intermediary space between setter-established organizations and non-dominant epistemologies, ontologies, and practices. I analyse the mechanisms of these examples in relation to the intersecting pillars of land, labour, and community to consider where and how they open up space for reimagining curation. I employ a decolonial feminist methodological approach to assess and make visible the colonial and patriarchal biases present in western curatorial praxes and to extend the scholarship on feminist and decolonial curation in Canada through models that centre direct action. Finally, I locate Canadian practices within international discourses that speak to instrumental change towards equity within dominant culture spaces and demonstrate praxes that have been built predominantly through relationships that support and underscore relational and land-based pedagogies. With emphasis on the relational methodologies that shape my own practice, my study is relative to the locations and practitioners from which and with whom these ideas have evolved, and my relationship to them.Toby Katrine Lawrencework_vcch2znu7jebngnpedvyvmg6y4Tetraquarks: relativistic corrections and other issues
https://scholar.archive.org/work/ueff5cnivbd7lostbam24abwbm
We discuss the effect of relativistic kinematics on the binding energy of multiquark states. For a given potential, the use of relativistic kinematics lowers the energy by a larger amount for the threshold made of two mesons than for a tetraquark, so that its binding is weakened. Some other issues associated with exotic hadrons are also briefly discussed.Jean-Marc Richard, Alfredo Valcarce, Javier Vijandework_ueff5cnivbd7lostbam24abwbmMon, 20 Dec 2021 00:00:00 GMTExploring Contemporary Kabbalah: Divine Names, Dolphins and Sexual Magic
https://scholar.archive.org/work/oltpnwwcqng3jip3pukd3bo5la
publicerades ursprungligen i tryckt format. Från och med volym 11 (2020), har tidskriften omarbetats till en diamond open access-tidskrift, och har bytt namn till Aura: Tidsskrift for akademiske studier av nyreligiøsitetSara Møldrup Thejlswork_oltpnwwcqng3jip3pukd3bo5laMon, 29 Nov 2021 00:00:00 GMT