cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Slow light in paraffin-coated Rb vapor cells
Creators: name: Klein, M.
name: Novikova, I.
name: Phillips, D. F.
name: Walsworth, R. L.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We present preliminary results from an experimental study of slow light in anti-relaxation-coated Rb vapor cells, and describe the construction and testing of such cells. The slow ground state decoherence rate allowed by coated cell walls leads to a dual-structured electromagnetically induced transparency (EIT) spectrum with a very narrow (<100 Hz) transparency peak on top of a broad pedestal. Such dual-structure EIT permits optical probe pulses to propagate with greatly reduced group velocity on two time scales. We discuss ongoing efforts to optimize the pulse delay in such coated cell systems.
description: 6 pages, 6 figures, submitted to Journal of Modern Optics
Satisfaction of linear temporal logic specifications through recurrence tools for hybrid systems
Creators: name: Bisoffi, Andrea
name: Dimarogonas, Dimos V.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Systems and Control (eess.SY)
subject: Formal Languages and Automata Theory (cs.FL)
subject: Dynamical Systems (math.DS)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: In this work we formulate the problem of satisfying a linear temporal logic formula on a linear plant with output feedback, through a recent hybrid systems formalism. We relate this problem to the notion of recurrence introduced for the considered formalism, and we then extend Lyapunov-like conditions for recurrence of an open, unbounded set. One of the proposed relaxed conditions allows certifying recurrence of a suitable set, and this guarantees that the high-level evolution of the plant satisfies the formula, without relying on discretizations of the plant. Simulations illustrate the proposed approach.
description: To appear in IEEE Transactions on Automatic Control
Numerical-experimental estimation of the deformability of human red blood cells from rheometrical data
Creators: name: Takeishi, Naoki
name: Nishiyama, Tomohiro
name: Nagaishi, Kodai
name: Nashima, Takeshi
name: Sugihara-Seki, Masako
Publisher: name: arXiv
Year: 2024
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: The deformability of human red blood cells (RBCs), which comprise almost 99% of the cells in whole blood, is largely related not only to pathophysiological blood flow but also to the levels of intracellular compounds. Therefore, statistical estimates of the deformability of individual RBCs are of paramount importance in the clinical diagnosis of blood diseases. Although the micro-scale hydrodynamic interactions of individual RBCs lead to non-Newtonian blood rheology, there is no established method to estimate individual RBC deformability from the rheological data of RBC suspensions, and the possibility of this estimation has not been proven. To address this issue, we conducted an integrated analysis of a model of the rheology of RBC suspensions, coupled with macro-rheological data of human RBCs suspended in plasma. Assuming a non-linear curve of the relative viscosity of the suspensions as a function of the cell volume fraction, the statistical average of the membrane shear elasticity was estimated for individual intact RBCs or hardened RBCs. Both estimated values reproduced well the experimentally observed shear-thinning non-Newtonian behavior in these suspensions. We hereby conclude that our complementary approach makes it possible to estimate the statistical average of individual RBC deformability from macro-rheological data obtained with usual rheometric tests.
Modeling zero inflated count data
Creators: name: Garden, Cheryl Ellen
Publisher: name: University of British Columbia
Year: 2009

description: A natural approach to analyzing the effect of covariates on a count response variable is to use a Poisson regression model. A complication is that the counts are often more variable than can be explained by a Poisson model. This problem, referred to as overdispersion, has received a great deal of attention in recent literature and a number of variations on the Poisson regression model have been developed. As such, statistical consultants are faced with the difficult task of identifying which of these alternative models is best suited to their particular application. In this thesis, two applications where the data exhibit overdispersion are investigated. In the first application, two treatments for chronic urinary tract infections are compared. The response variable represents the number of resistant strains of bacteria cultured from rectal swabs. In the second application, the number of units sold of a product are modeled as depending on two factors representing the day of the week and the store. Two alternative models that allow for overdispersion are used in both applications. The negative binomial regression model and the zero inflated Poisson regression model so named by Lambert (Lambert, 1992) provide improved fits. Further, the zero inflated Poisson regression model performs particularly well in the situation when the overdispersion is suspected to be due to a large number of zeroes occurring in the data. The zero inflated Poisson regression model allows one to both fit the data well and make some inference regarding the nature of the overdispersion present. This little known model may prove to be valuable as there exist a number of applications where observed overdispersion in a count response variable is clearly due to an inflated number of zeroes.
title: On the use of modal derivatives for nonlinear model order reduction
Creators: name: Weeger, Oliver
name: Wever, Utz
name: Simeon, Bernd
Publisher: name: Wiley
Year: 2021

description: Modal derivative is an approach to compute a reduced basis for model order reduction of large-scale nonlinear systems that typically stem from the discretization of partial differential equations. In this way, a complex nonlinear simulation model can be integrated into an optimization problem or the design of a controller, based on the resulting small-scale state-space model. We investigate the approximation properties of modal derivatives analytically and thus lay a theoretical foundation of their use in model order reduction, which has been missing so far. Concentrating on the application field of structural mechanics and structural dynamics, we show that the concept of modal derivatives can also be applied as nonlinear extension of the Craig–Bampton family of methods for substructuring. We furthermore generalize the approach from a pure projection scheme to a novel reduced-order modeling method that replaces all nonlinear terms by quadratic expressions in the reduced state variables. This complexity reduction leads to a frequency-preserving nonlinear quadratic state-space model. Numerical examples with carefully chosen nonlinear model problems and three-dimensional nonlinear elasticity confirm the analytical properties of the modal derivative reduction and show the potential of the proposed novel complexity reduction methods, along with the current limitations.
Watjuho Walaretjä ("Vamos falar juntos")
Creators: name: Bardagil Mas, Bernat
Publisher: name: California Language Archive, University of California, Berkeley
Year: 2023
Subjects: Manoki language

description: Caderno básico para o estudo da língua mỹky na variedade dos Manoki, a partir de materiais de ensino elaborados nos encontros do Coletivo Watjuho Ja'a em 2019 e 2020. 100 cópias foram imprimidas em Tangará da Serra em junho de 2022, e distribuidas na aldeia Cravari e demais aldeias Manoki.
A basic language-learning booklet for the Manoki, created from the teaching materials developed during the meetings and schools run by the Watjuho Ja'a Collective in 2019 and 2020. One hundred copies were printed in Tangará da Serra in June of 2022 and distributed in Cravari and other Manoki villages.
Ties that unbind? Ethnic identity, social rules and electorial politics in Solomon Islands
Creators: name: Wood, Terence
Publisher: name: The Australian National University
Year: 2014

description: This is a study of ethnic identity and electoral politics in Solomon Islands. The study examines when and why Solomon Islanders vote ethnically in national elections, which ethnic identities are electorally important, and how ethnic voting is associated with broader features of the country's politics. The thesis makes use of regression analysis to show existing theories of ethnic identity and electoral politics do not fit the Solomon Islands case. It then uses electorate-level case studies to develop an alternative theory of ethnic voting. This theory is then tested with further quantitative work. The argument advanced in the thesis is that ethnic identities only play an important role in electoral politics in Solomon Islands when the groups associated with them are home to social rules (informal institutions) which enable effective electoral collective action. Such rules include: norms of obligation which may make co-ethnic candidates more likely to follow up on electoral promises; rules which enhance the loyalty of the brokers candidates use in their attempts to gain votes; and rules which enable key political actors to coordinate support behind favoured candidates. Importantly, rules have to be present within ethnic groups for ethnic voting to occur. Clans commonly possess such rules and so are often electorally important groups. Language groups do not typically possess such rules and so are rarely electorally important. In the case of churches, the presence of electorally useful social rules varies between denominations. Politics in Solomon Islands is strongly clientelist. Where voters are free to choose they typically vote for the candidate they think most likely to provide individualised or localised help. The ethnic voting which comes coupled with this does not involve blind loyalties but rather the calculations of voters and political actors. Social rules associated with ethnic identities play an important role in structuring these calculations but, except in rare instances where rules are very strong, they do not perfectly determine behaviour. As a result, other factors have a major impact on voters' choices: where they are free to choose, voters will vote for candidates who are not co-ethnics if given good cause to believe they will help. On the basis of these observations I argue clientelism, rather than ethnic voting, is the source of poor political governance in Solomon Islands. I also argue that, rather than ethnic diversity itself causing political fragmentation in Solomon Islands, the cause actually lies in the absence of larger entities (social or political movements) possessing anything analogous to the social rules found in some ethnic groups. Absent such rules, effective electoral collective action is difficult. And absent large-scale electoral collective action, clientelism appears inevitable.
Ab initio calculations of the physical properties of transition metal carbides and nitrides and possible routes to high-Tc
Creators: name: Maksimov, E. G.
name: Ebert, S. V.
name: Magnitskaya, M. V.
name: Karakozov, A. E.
name: Savrasov, S. Yu.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Ab initio linear-response calculations are reported of the phonon spectra and the electron-phonon interaction for several transition metal carbides and nitrides in a NaCl-type structure. For NbC, the kinetic, optical, and superconducting properties are calculated in detail at various pressures and the normal-pressure results are found to well agree with the experiment. Factors accounting for the relatively low critical temperatures Tc in transition metal compounds with light elements are considered and the possible ways of increasing Tc are discussed.
description: 19 pages, 7 figures
Strong vertices of doubly heavy spin-3/2--spin-1/2 baryons with light mesons in light-cone QCD sum rules
Creators: name: Aliev, T. M.
name: Şimşek, K.
Publisher: name: arXiv
Year: 2020
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: In this paper, we analyze the doubly heavy spin-3/2--spin-1/2 baryons and light meson vertices within the method of light-cone QCD sum rules. These vertices are parametrized in terms of one (three) coupling constant(s) for the pseudoscalar (vector) mesons. The said coupling constants are calculated for all possible transitions. The results presented here can serve to be useful information in experimental as well as theoretical studies of the properties of doubly heavy baryons.
description: 27 pages, 8 figures, 4 tables
Koopman Analysis of the Singularly-Perturbed van der Pol Oscillator
Creators: name: Katayama, Natsuki
name: Susuki, Yoshihiko
Publisher: name: arXiv
Year: 2024
Subjects: subject: Dynamical Systems (math.DS)
subject: Systems and Control (eess.SY)
subject: FOS: Mathematics
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: G.1.7
subject: 34C26(Primary), 37C30(Secondary)

description: The Koopman operator framework holds promise for spectral analysis of nonlinear dynamical systems based on linear operators. Eigenvalues and eigenfunctions of the Koopman operator, so-called Koopman eigenvalues and Koopman eigenfunctions, respectively, mirror global properties of the system's flow. In this paper we perform the Koopman analysis of the singularly-perturbed van der Pol system. First, we show the spectral signature depending on singular perturbation: how two Koopman {principal} eigenvalues are ordered and what distinct shapes emerge in their associated Koopman eigenfunctions. Second, we discuss the singular limit of the Koopman operator, which is derived through the concatenation of Koopman operators for the fast and slow subsystems. From the spectral properties of the Koopman operator for the {singularly}-perturbed system and the singular limit, we suggest that the Koopman eigenfunctions inherit geometric properties of the singularly-perturbed system. These results are applicable to general planar singularly-perturbed systems with stable limit cycles.
description: 21 pages, 10 figures
The Exponent Expansion: An Effective Approximation of Transition Probabilities of Diffusion Processes and Pricing Kernels of Financial Derivatives
Creators: name: Capriotti, Luca
Publisher: name: arXiv
Year: 2006
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Statistics Theory (math.ST)
subject: Computational Physics (physics.comp-ph)
subject: Statistical Finance (q-fin.ST)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: FOS: Economics and business

description: A computational technique borrowed from the physical sciences is introduced to obtain accurate closed-form approximations for the transition probability of arbitrary diffusion processes. Within the path integral framework the same technique allows one to obtain remarkably good approximations of the pricing kernels of financial derivatives. Several examples are presented, and the application of these results to increase the efficiency of numerical approaches to derivative pricing is discussed.
description: 21 pages, 5 figures, to appear in the International Journal of Theoretical and Applied Finance
Manufacturing Power: The Everyday Politics of Privilege Among the Pakistani Business Elite
Creators: name: Armytage, Rosita
Publisher: name: Canberra, ACT : The Australian National University
Year: 2016
Subjects: elites
capitalism
class
power
Pakistan

description: This thesis interrogates the operation of modern capitalism within a context of political instability and economic inequality. In doing so, it examines the relationship between power, instability, informal processes, and the accumulation of vast amounts of capital. Specifically, this thesis is about the process of acquiring, maintaining, and wielding economic power in Pakistan – an industrialising economy beset by high levels of political change and economic insecurity. Based on 13 months of ethnographic fieldwork, this thesis examines the group of families who occupy the upper-most tier of the economic and social structure, the means through which they have acquired and protected power and influence, and the challenges non-elite individuals face in attaining upward social mobility in developing countries. In contrast to studies that examine the ways in which global economic integration creates new avenues for the capture of wealth, privilege and political influence, my research demonstrates that forms of “hyper-capitalism” have not come to dominate markets globally. Rather, in many contexts, commerce remains governed by highly personalised and intimate relations determined by local cultural practices. I show that business in Pakistan has remained resiliently “local,” and dependent upon deeply rooted familial, ethnic and class structures. Localised elite business practices remain substantially independent from the “international standards” of business propagated by multinational corporations, international investors, and the international market. In this context, the resilience of local forms of business constitutes not only a site of interlinked personal, gendered and economic processes, but also a site of post-colonial assertiveness. This thesis explores the informal means through which elites navigate their social, marital and business environments to reconstitute their power in line with shifting economic and political conditions. Despite the economic transformations that have taken place in Pakistan over the past seventy years, and the shifts in social structure these changes have engendered, the Pakistani elite has routinely fortified and reconstituted the power and privilege of its members in a shared pursuit of profit and market dominance. The resilience of these modes of doing business reflect the inability of international forms of global capital to successfully re-colonise local markets and extract the nationally- generated wealth now held by domestic elites.
A Stochastic Theory of the Hierarchical Clustering I. Halo Mass Function
Creators: name: Lapi, Andrea
name: Danese, Luigi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present a new theory for the hierarchical clustering of dark matter (DM) halos based on stochastic differential equations, that constitutes a change of perspective with respect to existing frameworks (e.g., the excursion set approach); this work is specifically focused on the halo mass function. First, we present a stochastic differential equation that describes fluctuations in the mass growth of DM halos, as driven by a multiplicative white (Gaussian) noise dependent on the spherical collapse threshold and on the power spectrum of DM perturbations. We demonstrate that such a noise yields an average drift of the halo population toward larger masses, that quantitatively renders the standard hierarchical clustering. Then, we solve the Fokker-Planck equation associated to the stochastic dynamics, and obtain the Press & Schechter mass function as a (stationary) solution. Moreover, generalizing our treatment to a mass-dependent collapse threshold, we obtain an exact analytic solution capable of fitting remarkably well the N-body mass function over a wide range in mass and redshift. All in all, the new perspective offered by the theory presented here can contribute to better understand the gravitational dynamics leading to the formation, evolution and statistics of DM halos across cosmic times.
description: 12 pages, 3 figures. Accepted by ApJ
Normative Standing: De Facto State Identity and International Legitimation
Creators: name: Klich, Sebastian Tadeusz
Publisher: name: The Australian National University
Year: 2018
Subjects: De facto states, unrecognised states, unrecognized states, international relations, international relations theory, constructivism, English School, legitimacy, Iraq, Kurdistan Region of Iraq, Nagorno Karabakh, Nagorno-Karabakh, Somaliland

description: This thesis makes an original contribution to the field of de facto state studies. The robustness and durability of de facto states in the post-Cold War era has defied scholars’ earlier predictions of likely impermanence. In the de facto states literature that followed, a focus on rational choice approaches permeated the analysis of these states’ international engagement, however the concept of de facto state identity and how it shapes the relationship with international society has yet to be fully explored and analysed. A recent trend towards examining the legitimation strategies of de facto states has been restricted by an under-conceptualisation of the social system that they inhabit, restricting the explanatory utility of legitimacy as an analytical lens. Rather than an abnormality, non-recognition has been the norm in the relationship between de facto states and international society. A stasis has formed. The under-conceptualisation of the relationship has remained a partial void that has limited the understanding of a phenomenon that continues to challenge central concepts in the discipline of International Relations. The core objective of this thesis is to address that conceptual need by synthesising constructivist and English School approaches to build a conceptual framework of normative standing that enables a clearer articulation of the relationship between de facto states and international society. It employs a constructivist methodology to examine the recognition narrative of de facto states, in order to conduct constitutive analysis of their state identities, and to build the foundations of a theory of normative standing. Three case studies, with varying degrees of international engagement and parent state relationships, were selected for the examination of the application of the conceptual framework. Together, they provide for an effective generalisation across the spectrum of de facto states. The three case studies ― Nagorno Karabakh, Somaliland, and the Kurdistan Region of Iraq ― were informed by fieldwork interviews conducted in situ. The theory of normative standing proposed by this thesis proves to be a useful tool to explain de facto states' endurability, how de facto statehood has itself become a role identity in the international system, and the stasis of the relationship between de facto states and international society.
Development cost levies : an analysis of park levies on commercial floorspace (in the city of Vancouver)
Creators: name: Tully, Barbara
Publisher: name: University of British Columbia
Year: 2009

description: The use of Development Cost Levies is a relatively new mechanism by which municipalities may charge development a share of costly new infrastructure. Their use is an improvement upon the previous ad-hoc system of land use contracts. The equity of Development Cost Levies is widely disputed, but this thesis finds that their use is fair and justifiable when judged in the context of the unprecedented growth of the Lower Mainland. The paper finds that Development Cost Levies are generally passed back to the landowners, unless the market is inelastic, in which case they are passed forward to the purchaser. The thesis specifically examines Development Cost Levies for parkland acquisition in mixed-use neighbourhoods. Park acquisition levies in mixed-use neighbourhoods are currently charged only to residential development in B.C. municipalities. This thesis examines whether the usage of parks by employees warrants commercial development paying a share of the parkland acquisition levies in mixed use neighbourhoods. In order to determine if commercial development should pay a portion of the cost of park acquisition, a park survey was conducted in an existing mixed-use area to determine employee usage of parkspace. A literature search revealed no other park surveys which examined employee and resident usage of parkspace in mixed-use neighbourhoods. The survey found that employees generated 83% of the usage of parkspace in two mixed-use area neighbourhood parks. The findings of the survey indicate that commercial development should be paying a proportional share of development cost charges for parkland acquisition in mixed-use neighbourhoods. This information was then applied to a recently upzoned area of the City of Vancouver to illustrate a sample calculation of Development Cost Levies.
Varying curvature and angularity of architectural facades can influence aesthetic judgments
Creators: name: Ruta, Nicole
name: Mastandrea, Stefano
name: Lamaddalena, Stefania
name: Bove, Giuseppe
Publisher: name: F1000Research
Year: 2015

description: Several researches showed that humans prefer curved stimuli compared to angular ones (shapes, objects, interior spaces; Bar & Neta, 2006, 2007; Vartanian et al. 2013). Our aim is to extend to architectural facades the role of curves and angles in terms of preference. We produced four different versions of the same building, varying its curvature (high and medium curvature; rectilinear and angular). Twenty four participants 1) made a preference forced choice between pairs of the stimuli; 2) evaluated each stimulus on 5 point likert scales (liking, familiarity, complexity, stability and approach); 3) classified all the stimuli from the most to the least preferred. Multidimensional scaling on the forced choices showed that the high curved façade was the most preferred, followed by the medium curved, angular and rectilinear ones. Multidimensional unfolding showed that the majority expressed higher preferences for the curved facades compared to angular and rectilinear ones. A repeat measures ANOVA on liking evaluation showed that the high curvature façades was the most preferred followed by angular, medium curved and rectilinear ones. Our findings showed that curvature influences preferences also for architectural stimuli. In addition to that rectilinear stimuli were always the least preferred and not angularity as expected.
Superconducting state of Sr$_2$RuO$_4$ in the presence of longer-range Coulomb interactions
Creators: name: Rømer, Astrid T.
name: Hirschfeld, P. J.
name: Andersen, Brian M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: The symmetry of the superconducting condensate in Sr$_2$RuO$_4$ remains controversial after nuclear magnetic resonance (NMR) experiments recently overturned the dominant chiral $p$-wave paradigm. Several theoretical proposals have been put forward to account for existing experiments, including a $d+ig$-wave admixture, conjectured to be stabilized by longer-range Coulomb interactions. We perform a material-specific microscopic theoretical study of pairing by spin- and charge-fluctuations in Sr$_2$RuO$_4$, including the effects of spin-orbit coupling, and both local and longer-range Coulomb repulsion. The latter has important consequences for Sr$_2$RuO$_4$ due to the near-degeneracy of symmetry-distinct pairing states in this material. We find that both the $g$- and $d_{x^2-y^2}$-wave channels remain noncompetitive compared to leading nodal $s'$, $d_{xy}$, and helical ($p$) solutions. This suggests nodal time-reversal symmetry broken $s'+id_{xy}$ or $s'+ip$ phases, promoted by longer-range Coulomb repulsion, as the most favorable candidates for Sr$_2$RuO$_4$. We analyse the properties of these states, and show that the $s'+id_{xy}$ solution agrees with the bulk of available experimental data, including recent discoveries from NMR, muon spin relaxation ($μ$SR), and ultrasound measurements.
description: 4 pages, 2 figures + supplementary material
Time Evolution and Thermal Renormalization Group Flow in Cosmology
Creators: name: Marian, Istvan Gabor
name: Trombettoni, Andrea
name: Nandori, Istvan
Publisher: name: arXiv
Year: 2024
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Time-evolution of the Universe as described by the Friedmann equation can be coupled to equations of motion of matter fields. Quantum effects may be incorporated to improve these classical equations of motion by the renormalization group (RG) running of their couplings. Since temporal and thermal evolutions are linked to each other, astrophysical and cosmological treatments based on zero-temperature RG methods require the extension to finite-temperatures. We propose and explore a modification of the usual finite-temperature RG approach by relating the temperature parameter to the running RG scale as $T \equiv k_T = τk$ (in natural units), where $k_T$ is acting as a running cutoff for thermal fluctuations and the momentum $k$ can be used for the quantum fluctuations. In this approach, the temperature of the expanding Universe is related to the dimensionless quantity $τ$ (and not to $k_T$). We show that by this choice dimensionless RG flow equations have no explicit $k$-dependence, as it is convenient. We also discuss how this modified thermal RG is used to handle high-energy divergences of the RG running of the cosmological constant and to "solve the triviality"of the $ϕ^4$ model by a thermal phase transition in terms of $τ$ in $d=4$ Euclidean dimensions.
description: 9 pages, 2 figures, v3: final version published in Phys.Lett.B
Disks as Inhomogeneous, Anisotropic Gaussian Random Fields
Creators: name: Lee, Daeyoung
name: Gammie, Charles F.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We model astrophysical disk surface brightness fluctuations as an inhomogeneous, anisotropic, time-dependent Gaussian random field. The field locally obeys the stochastic partial differential equation of a Matérn field, which has a power spectrum that is flat at large scales and falls off as a power law at small scales. We provide a series of pedagogical examples and along the way provide a convenient parameterization for the local covariance. We then consider two applications to disks. In the first we generate a movie of a disk. In the second, by integrating over a movie of a disk, we generate synthetic light curves and show that the high frequency slope of the resulting power spectrum depends on the local covariance model. We finish with a summary and a brief discussion of other possible astrophysical applications.
description: 11 pages, 6 figures, 2 animations
Jet quenching at finite `t Hooft coupling and chemical potential from AdS/CFT
Creators: name: Armesto, Nestor
name: Edelstein, Jose D.
name: Mas, Javier
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Following the nonperturbative prescription for the jet quenching parameter recently proposed by Liu, Rajagopal and Wiedemann, we compute the first correction in the inverse `t Hooft coupling corresponding to string alpha' corrections in the dual background. We also consider the introduction of a chemical potential for the U(1)^3 gauged R-symmetry. While the former mildly diminishes the jet quenching parameter -this suggesting a smooth interpolation between the strong coupling and perturbative results-, the latter generically increases its value. We comment on the extension of this setup to quarks of finite mass.
description: 15 pages, 4 figures; v3: Error in the expansions and figures of section 4 corrected, new comment and figure on the extension to finite quark mass, cites added and typos fixed
Partition Functions of Torsion >1 Dyons in Heterotic String Theory on T^6
Creators: name: Banerjee, Shamik
name: Sen, Ashoke
name: Srivastava, Yogesh K.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The original proposal of Dijkgraaf, Verlinde and Verlinde for the quarter BPS dyon partition function in heterotic string theory on T^6 is known to correctly produce the degeneracy of dyons of torsion 1, i.e. dyons for which gcd(Q\wedge P)=1. We propose a generalization of this formula for dyons of arbitrary torsion. Our proposal satisfies the constraints coming from S-duality invariance, wall crossing formula, black hole entropy and the gauge theory limit. Furthermore using our proposal we derive a general wall crossing formula that is valid even when both the decay products are non-primitive half-BPS dyons.
description: LaTeX file, 16 pages
Signal Processing in the Retina: Interpretable Graph Classifier to Predict Ganglion Cell Responses
Creators: name: Parhizkar, Yasaman
name: Cheung, Gene
name: Eckford, Andrew W.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Machine Learning (cs.LG)
subject: Image and Video Processing (eess.IV)
subject: Neurons and Cognition (q-bio.NC)
subject: Quantitative Methods (q-bio.QM)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Biological sciences

description: It is a popular hypothesis in neuroscience that ganglion cells in the retina are activated by selectively detecting visual features in an observed scene. While ganglion cell firings can be predicted via data-trained deep neural nets, the networks remain indecipherable, thus providing little understanding of the cells' underlying operations. To extract knowledge from the cell firings, in this paper we learn an interpretable graph-based classifier from data to predict the firings of ganglion cells in response to visual stimuli. Specifically, we learn a positive semi-definite (PSD) metric matrix $\mathbf{M} \succeq 0$ that defines Mahalanobis distances between graph nodes (visual events) endowed with pre-computed feature vectors; the computed inter-node distances lead to edge weights and a combinatorial graph that is amenable to binary classification. Mathematically, we define the objective of metric matrix $\mathbf{M}$ optimization using a graph adaptation of large margin nearest neighbor (LMNN), which is rewritten as a semi-definite programming (SDP) problem. We solve it efficiently via a fast approximation called Gershgorin disc perfect alignment (GDPA) linearization. The learned metric matrix $\mathbf{M}$ provides interpretability: important features are identified along $\mathbf{M}$'s diagonal, and their mutual relationships are inferred from off-diagonal terms. Our fast metric learning framework can be applied to other biological systems with pre-chosen features that require interpretation.
SA-Net: A deep spectral analysis network for image clustering
Creators: name: Wang, Jinghua
name: Jiang, Jianmin
Publisher: name: arXiv
Year: 2020
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Although supervised deep representation learning has attracted enormous attentions across areas of pattern recognition and computer vision, little progress has been made towards unsupervised deep representation learning for image clustering. In this paper, we propose a deep spectral analysis network for unsupervised representation learning and image clustering. While spectral analysis is established with solid theoretical foundations and has been widely applied to unsupervised data mining, its essential weakness lies in the fact that it is difficult to construct a proper affinity matrix and determine the involving Laplacian matrix for a given dataset. In this paper, we propose a SA-Net to overcome these weaknesses and achieve improved image clustering by extending the spectral analysis procedure into a deep learning framework with multiple layers. The SA-Net has the capability to learn deep representations and reveal deep correlations among data samples. Compared with the existing spectral analysis, the SA-Net achieves two advantages: (i) Given the fact that one spectral analysis procedure can only deal with one subset of the given dataset, our proposed SA-Net elegantly integrates multiple parallel and consecutive spectral analysis procedures together to enable interactive learning across different units towards a coordinated clustering model; (ii) Our SA-Net can identify the local similarities among different images at patch level and hence achieves a higher level of robustness against occlusions. Extensive experiments on a number of popular datasets support that our proposed SA-Net outperforms 11 benchmarks across a number of image clustering applications.
description: arXiv admin note: text overlap with arXiv:2009.05235
Evidence of discrete energy states and cluster-glass behavior in Sr$_{2-x}$La$_x$CoNbO$_6$
Creators: name: Kumar, Ajay
name: Schwarz, B.
name: Ehrenberg, H.
name: Dhaka, R. S.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We report the detailed analysis of specific heat [C$_{\rm P}$(T)] and ac-susceptibility for magnetically frustrated Sr$_{2-x}$La$_x$CoNbO$_6$ ($x=$ 0--1) double perovskites to understand low temperature complex magnetic interactions and their evolution with $x$. Interestingly, the observed Schottky anomaly in the $x\leqslant$ 0.4 samples shifts gradually towards higher temperature with magnetic field as well as $x$, and the analysis reveal the persistence of the discrete energy states in these samples resulting from the spin-orbit coupling and octahedral distortion. Moreover, the extracted values of Landé g--factor indicate the existence of high-spin state Co$^{3+}$ ions close to non-magnetic low-spin state. The specific heat data show the $λ$-type anomaly for the $x\geqslant$ 0.6 samples due to evolution of the long range antiferromagnetic ordering. Our analysis of low temperature C$_{\rm P}$(T) data for the $x\geqslant$ 0.6 samples demonstrate the 3D isotropic Heisenberg antiferromagnetic (AFM) interactions and the temperature induced second order AFM--paramagnetic phase transition. More interestingly, we demonstrate the presence of the free Co$^{2+}$ like Kramers doublet ground state in the $x =$1 sample. Further, the ac susceptibility and time evolution of the magnetization data reveal the low temperature cluster-glass like behavior in the $x=$ 0--0.4 samples, where spin-spin correlation strength decreases with $x$.
description: accepted for publication in PRB
Geometrically-induced localization of flexural waves on thin warped physical membranes
Creators: name: Kernes, Jonathan
name: Levine, Alex J.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We consider the propagation of flexural waves across a nearly flat, thin membrane, whose stress-free state is curved. The stress-free configuration is specified by a quenched height field, whose Fourier components are drawn from a Gaussian distribution with power law variance. Gaussian curvature couples the in-plane stretching to out-of-plane bending. Integrating out the faster stretching modes yields a wave equation for undulations in the presence of an effective random potential, determined purely by geometry. We show that at long times/lengths, the undulation intensity obeys a diffusion equation. The diffusion coefficient is found to be frequency dependent and sensitive to the quenched height field distribution. Finally, we consider the effect of coherent backscattering corrections, yielding a weak localization correction that decreases the diffusion coefficient proportional to the logarithm of the system size, and induces a localization transition at large amplitude of the quenched height field. The localization transition is confirmed via a self-consistent extension to the strong disorder regime.
description: 26 pages, 13 figures, 6 tables
First-Principles Equation of State Database for Warm Dense Matter Computation
Creators: name: Militzer, Burkhard
name: Gonzalez-Cataldo, Felipe
name: Zhang, Shuai
name: Driver, Kevin P.
name: Soubiran, Francois
Publisher: name: arXiv
Year: 2020
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We put together a first-principles equation of state (FPEOS) database for matter at extreme conditions by combining results from path integral Monte Carlo and density functional molecular dynamics simulations of the elements H, He, B, C, N, O, Ne, Na, Mg, Al and Si as well as the compounds LiF, B4C, BN, CH4, CH2, C2H3, CH, C2H, MgO, and MgSiO3. For all these materials, we provide the pressure and internal energy over a density-temperature range from ~0.5 to 50 g/cc and from ~10^4 to 10^9 K, which are based on ~5000 different first-principles simulations. We compute isobars, adiabats and shock Hugoniot curves in the regime of L and K shell ionization. Invoking the linear mixing approximation, we study the properties of mixtures at high density and temperature. We derive the Hugoniot curves for water and alumina as well as for carbon-oxygen, helium-neon, and CH-silicon mixtures. We predict the maximal shock compression ratios of H2O, H2O2, Al2O3, CO, and CO2 to be 4.61, 4.64, 4.64, 4.89, and 4.83, respectively. Finally we use the FPEOS database to determine the points of maximum shock compression for all available binary mixtures. We identify mixtures that reach higher shock compression ratios than their endmembers. We discuss trends common to all mixtures in pressure-temperature and particle-shock velocity spaces. In the supplementary material, we provide all FPEOS tables as well as computer codes for interpolation, Hugoniot calculations, and plots of various thermodynamic functions.
description: 13 figures, will appear in Phys. Rev. E
Star Formation and Feedback in Smoothed Particle Hydrodynamic Simulations--I. Isolated Galaxies
Creators: name: Stinson, Greg
name: Seth, Anil
name: Katz, Neal
name: Wadsley, James
name: Governato, Fabio
name: Quinn, Tom
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present an analysis of star formation and feedback recipes appropriate for galactic smoothed particle hydrodynamics simulations. Using an isolated Milky Way-like galaxy, we constrain these recipes based on well-established observational results. Our star formation recipe is based on that of Katz (1992) with the additional inclusion of physically motivated supernova feedback recipes. We propose a new feedback recipe in which type II supernovae are modelled using an analytical treatment of blastwaves. With this feedback mechanism and a tuning of other star formation parameters, the star formation in our isolated Milky Way-like galaxy is constant and follows the slope and normalisation of the observed Schmidt law. In addition, we reproduce the low density cutoff and filamentary structure of star formation observed in disk galaxies. Our final recipe will enable better comparison of cosmological N-body simulations with observations.
description: 18 pages, 22 figures, accepted to MNRAS, full resolution figures, more data, and movies at http://hpcc.astro.washington.edu/starformation
When D-branes Break
Creators: name: Bergman, Oren
name: Lifschytz, Gilad
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We analyze the possible configurations of D-branes breaking on other D-branes. We describe these configurations in the context of a brane-antibrane effective theory in two ways. First as a tachyon configuration representing a non-trivial bundle over the sphere surrounding the end of the brane a la Polchinski, and second in terms of tachyon solitons using homotopy theory. Surprisingly, in some cases there are topologically stable configurations of broken branes.
description: 15 pages, 1 figure
Activity-induced phase transition and coarsening dynamics in dry apolar active nematics
Creators: name: Sinha, Arpan
name: Chaudhuri, Debasish
Publisher: name: arXiv
Year: 2024
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Biological Physics (physics.bio-ph)
subject: FOS: Physical sciences

description: Using the Lebwohl-Lasher interaction for reciprocal local alignment, we present a comprehensive phase diagram for a dry, apolar, active nematic system using its stochastic \new{off-lattice} dynamics. \new{The nematic-isotropic transition in this system is first-order and occurs alongside a fluctuation-dominated phase separation.} Our phase diagram identifies three distinct regions based on activity and orientational noise relative to alignment strength: a homogeneous isotropic phase, a nematic phase with giant density fluctuations, and a coexistence region. Using mean-field analysis and hydrodynamic theory, we demonstrate that reciprocal interactions lead to a density fluctuation-induced first-order transition and derive a phase boundary consistent with numerical results. Quenching from the isotropic to nematic phase reveals coarsening dynamics where nematic ordering precedes particle clustering. Both the nematic and density fields exhibit similar scaling behaviors, exhibiting dynamic exponents $z_S \approx 2.5$ and $z_ρ\approx 2.34$, consistently falling within the range of 2 and 3.
description: 11 pages, 6 figures; version accepted for publication
Stabilizing moduli with thermal matter and nonperturbative effects
Creators: name: Danos, Rebecca J.
name: Frey, Andrew R.
name: Brandenberger, Robert H.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Even with recent progress, it is still very much an open question to understand how all compactification moduli are stabilized, since there are several mechanisms. For example, it is possible to generate a scalar potential either classically or through nonperturbative effects, such as gaugino condensation. Such a potential can stabilize certain of the moduli fields, for example the dilaton. On the other hand, a background of thermal matter with moduli-dependent masses can also stabilize certain of the moduli, e.g., the radion. It is important to understand whether these two distinct mechanisms are compatible with each other, that is, that there are no interference terms that could spoil the moduli stabilization. In this paper, we study heterotic string theory on an N=1 orbifold near an enhanced symmetry point. We then consider both a nonperturbatively generated potential and a gas of strings with moduli-dependent masses to stabilize the dilaton and radial modulus, respectively. We conclude that, given certain approximations, these two moduli stabilization mechanisms are compatible.
description: 13pg, 1 fig; v2. minor clarifications & reference additions