cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Second Harmonic Generation of MoSi2N4 Layer
Creators: name: Kang, Lei
name: Lin, Zheshuai
Publisher: name: arXiv
Year: 2020
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The recently discovered two-dimensional (2D) layered semiconductor MoSi2N4 has aroused great interest due to its unique 2D material characteristics. In this Letter, we found that differences in the structural details for MoSi2N4 may lead to differences in the intensity of second harmonic generation (SHG) and its response to strain. Accordingly, SHG can be used as a simple technique to identify the structural details of this system. We further calculated the SHG effects of MoSi2N4 derivatives and investigated their strain-regulation mechanism, especially including the anomalous SHG responses under strain for MoSi2P4 and MoGe2P4, differing from other known 2D materials. The studies may have forward-looking significance for the research of nonlinear optics and optoelectronics in this novel 2D material system.
description: 7 pages, 4 figures
Layer pseudospin dynamics and genuine non-Abelian Berry phase in inhomogeneously strained moiré pattern
Creators: name: Zhai, Dawei
name: Yao, Wang
Publisher: name: arXiv
Year: 2020
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Periodicity of long wavelength moiré patterns is very often destroyed by the inhomogeneous strain introduced in fabrications of van der Waals layered structures. We present a framework to describe massive Dirac fermions in such distorted moiré pattern of transition metal dichalcogenides homobilayers, accounting for the dynamics of layer pseudospin. In decoupled bilayers, we show two causes of in-plane layer pseudospin precession: By the coupling of layer antisymmetric strain to valley magnetic moment; and by the Aharonov-Bohm effect in the SU(2) gauge potential for the case of R-type bilayer under antisymmetric strain and H-type under symmetric strain. With interlayer coupling in the moiré, its interplay with strain manifests as a non-Abelian gauge field. We show a genuine non-Abelian Aharonov-Bohm effect in such field, where the evolution operators for different loops are non-commutative. This provides an exciting platform to explore non-Abelian gauge field effects on electron, with remarkable tunability of the field by strain and interlayer bias.
description: To appear in Phys. Rev. Lett
Time evolution of the Boltzmann entropy for a nonequilibrium dilute gas
Creators: name: Garrido, P. L.
name: Goldstein, S.
name: Huse, D. A.
name: Lebowitz, J. L.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We investigate the time evolution of the Boltzmann entropy of a dilute gas of N particles, N>>1, as it undergoes a free expansion doubling its volume. The microstate of the system, a point in the 4N dimensional phase space, changes in time via Hamiltonian dynamics. Its entropy, at any time $t$, is given by the logarithm of the phase space volume of all the microstates giving rise to its macrostate at time $t$. The macrostates that we consider are defined by coarse graining the one-particle phase space into cells $Δ_α$. The initial and final macrostates of the system are equilibrium states in volumes $V$ and $2V$, with the same energy $E$ and particle number $N$. Their entropy per particle is given, for sufficiently large systems, by the thermodynamic entropy as a function of the particle and energy density, whose leading term is independent of the size of the $Δ_α$. The intermediate (non-equilibrium) entropy does however depend on the size of the cells $Δ_α$. Its change with time is due to (i) dispersal in physical space from free motion and to (ii) the collisions between particles which change their velocities. The former depends strongly on the size of the velocity coarse graining $Δv$: it produces entropy at a rate proportional to $Δv$. This dependence is investigated numerically and analytically for a dilute two-dimensional gas of hard discs. It becomes significant when the mean free path between collisions is of the same order or larger than the length scale of the initial spatial inhomogeneity. In the opposite limit, the rate of entropy production is essentially independent of $Δv$ and is given by the Boltzmann equation for the limit $Δv\rightarrow 0$. We show that when both processes are active the time dependence of the entropy has a scaling form involving the ratio of the rates of its production by the two processes.
description: (20 pages, 8 figures)
Counting BPS Operators in the Chiral Ring of N=2 Supersymmetric Gauge Theories or N=2 Braine Surgery
Creators: name: Hanany, Amihay
name: Romelsberger, Christian
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: This note is presenting the generating functions which count the BPS operators in the chiral ring of a N=2 quiver gauge theory that lives on N D3 branes probing an ALE singularity. The difficulty in this computation arises from the fact that this quiver gauge theory has a moduli space of vacua that splits into many branches -- the Higgs, the Coulomb and mixed branches. As a result there can be operators which explore those different branches and the counting gets complicated by having to deal with such operators while avoiding over or under counting. The solution to this problem turns out to be very elegant and is presented in this note. Some surprises with "surgery" of generating functions arises.
description: 24 pages LaTeX
Quantum jump photodetector for narrowband photon counting with a single atom
Creators: name: Zarraoa, Laura
name: Veyron, Romain
name: Lamich, Tomas
name: Bianchet, Lorena C.
name: Mitchell, Morgan W.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Quantum Physics (quant-ph)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: Using a single neutral 87Rb atom held in an optical trap, and "quantum jump" detection of single-photon-initiated state changes, we demonstrate a single-photon quantum jump photodetector (QJPD) with intrinsically narrow bandwidth and strong rejection of out-of-band photons, of interest for detecting weak optical signals in the presence of a strong broadband background. By analyzing fluorescence photon count distributions for the bright and dark states with and without excitation, we measure quantum efficiency of 2.9(2)$\times 10^{-3}$, a record for single-pass quantum jump production, and signal-photon-unprovoked "dark jump" rate - analogous to the dark count rate of other detectors - 3(10)$\times 10^{-3}$ jumps per second during passive accumulation plus 4.0(4)$\times 10^{-3}$ jumps per readout, orders of magnitude below those of traditional single-photon detectors. Available methods can substantially improve QJPD quantum efficiency, dark jump rate, bandwidth and tunability.
description: 7 pages, 3 figures
Childhood Encounters with Anzac, the Teaching and Dissemination of a Tradition, and the (Re) Invention of Remembrance
Creators: name: Wheatley, Rebecca
Publisher: name: The Australian National University
Year: 2018
Subjects: Anzac, History of Children, History of Youth

description: Children have always played an important role in Australia’s Anzac story. They have carried the burden of war, they have lived with the legacies of conflict, they have been compelled to learn the ‘right’ lessons of history, and they have reshaped and reinvigorated Anzac’s traditions. Yet children are largely forgotten in Anzac’s historical account and they are marginalised in the debates and discussions about its place in modern Australia. This thesis embarks on a survey of how Australian children have lived with and learned about Anzac, from their families, their communities, and in their classrooms, from the end of the First World War to the Centenary of Anzac in 2015. This study draws on a number of archival collections, such as the National Archives of Australia’s repatriation records, the papers of the RSL and the Anzac Fellowship of Women, parliamentary debates, and school papers and publications. Central to this inquiry is a persistent endeavour to find ‘traces’ of children themselves. Much of the material I have consulted has been rarely used by historians and includes boys’ diaries, photographs, and ephemera from the Young Australia League pilgrimages to the sites of the First World War; dissenting secondary school students’ publications which challenged the Vietnam War and Australia’s culture of commemoration in the 1960s and 1970s; and children’s responses to the 1995 Australia Remembers commemorations. This project has created new archives all of its own. I have undertaken interviews with secondary school students and teachers to capture their experiences of how young people encounter Anzac. This thesis aims to recover young people’s testimony, weave their experiences into the historical narrative, and position their voices more centrally to contemporary discussions about Anzac. I argue they have responded to the call to remembrance in diverse and complex ways.
The Stationary Points of the Hierarchical Three Body Problem
Creators: name: Hansen, Bradley M. S.
name: Naoz, Smadar
Publisher: name: arXiv
Year: 2020
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: We study the stationary points of the hierarchical three body problem in the planetary limit (m_2, m_3 << m_1) at both the quadrupole and octupole orders. We demonstrate that the extension to octupole order preserves the principal stationary points of the quadrupole solution in the limit of small outer eccentricity e_2 but that new families of stable fixed points occur in both prograde and retrograde cases. The most important new equilibria are those that branch off from the quadrupolar solutions and extend to large e_2. The apsidal alignment of these families is a function of mass and inner planet eccentricity, and is determined by the relative directions of precession of omega_1 and omega_2 at the quadrupole level. These new equilibria are also the most resilient to the destabilizing effects of relativistic precession. We find additional equilibria that enable libration of the inner planet argument of pericentre in the limit of radial orbits and recover the non-linear analogue of the Laplace-Lagrange solutions in the coplanar limit. Finally, we show that the chaotic diffusion and orbital flips identified with the Eccentric Kozai Lidov mechanism and its variants can be understood in terms of the stationary points discussed here.
description: 27 pages, 36 figures
Asymmetric Vortex Sheet
Creators: name: Migdal, Alexander
Publisher: name: arXiv
Year: 2021
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Pattern Formation and Solitons (nlin.PS)
subject: FOS: Physical sciences

description: We present a steady analytical solution of the incompressible Navier-Stokes equation for arbitrary viscosity in an arbitrary dimension $d$ of space. It represents a $d-1$ dimensional vortex "sheet" with an asymmetric profile of vorticity as a function of the normal coordinate $z$. This profile is related to the Hermite polynomials $H_μ(z)$ which are analytically continued to the negative fractional index $μ= -\frac{d}{d-1}$. In $d=2$ dimensions, the solution degenerates to a constant vorticity flow. In $ d \ge 3$ dimensions, the vorticity is confined to the thin layer around the hyperplane with Gaussian decay on one side of the hyperplane and the power decay on another side. One can adjust the common scale of velocity so that the dissipation will stay finite at vanishing viscosity. In this limit, the width $w$ of the viscous lawyer will shrink to zero as $ν^{\frac{3}{5}}$ for arbitrary dimension $d>3$. In $d=3$ dimensions, this power law is also accompanied by powers of the logarithm.
description: 4 pages, 2 figures
On the continuity of intertwining operators over generalized convolution algebras
Creators: name: Flores, Felipe I.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Functional Analysis (math.FA)
subject: Operator Algebras (math.OA)
subject: FOS: Mathematics
subject: Primary 43A20, Secondary 47L65, 46H40

description: Let ${\sf G}$ be a locally compact group, $\mathscr C\overset{q}{\to}{\sf G}$ a Fell bundle and $\mathfrak B=L^1({\sf G}\,\vert\,\mathscr C)$ the algebra of integrable cross-sections associated to the bundle. We give conditions that guarantee the automatic continuity of an intertwining operator $θ:\mathcal X_1\to\mathcal X_2$, where $\mathcal X_1$ is a Banach $\mathfrak B$-bimodule and $\mathcal X_2$ is a weak Banach $\mathfrak B$-bimodule, in terms of the continuity ideal of $θ$. We provide examples of algebras where this conditions are met, both in the case of derivations and algebra morphisms. In particular, we show that, if ${\sf G}$ is infinite, finitely-generated, has polynomial growth and $α$ is a free (partial) action of ${\sf G}$ on the compact space $X$, then every homomorphism of $\ell^1_α({\sf G},C(X))$ into a Banach algebra is automatically continuous.
description: 21 pages. The paper had minor corrections and a change in style. To appear in J. Math. Anal. Appl
Self-oriented perfectionism and stress-enhancement : physiological and emotional reactivity in response to an achievement-related stressor
Creators: name: Flynn, Carol Ann
Publisher: name: University of British Columbia
Year: 2009

description: Previous research has demonstrated that self-oriented perfectionism and achievement stress work together to produce maladjustment and psychopathology. Self-oriented perfectionism may influence an individual's perception of the frequency and intensity of stressors, as well as lead to maladaptive coping styles which prolong stressful experience. In this study, 130 students engaged in challenging time-restricted math and anagram tasks. We hypothesized that self-oriented perfectionists would experience a more intense stress reaction than non-perfectionists. Stress levels were evaluated using a self-report mood questionnaire, heart rate, and salivary Cortisol levels. As expected, self-oriented perfectionism was associated with lower self-satisfaction with performance, and increased stress following the achievement task. Furthermore, those who scored high on both the self-oriented perfectionism subscale and a measure of task-oriented coping continued to experience elevated heart rates more than thirty minutes following completion of the task. Results are discussed in terms of a stress-enhancement model of perfectionism.
Maximizing information obtainable by quantum sensors through the Quantum Zeno Effect
Creators: name: Ronchi, Bruno
name: Zwick, Analia
name: Alvarez, Gonzalo A.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Efficient quantum sensing technologies rely on precise control of quantum sensors, particularly two-level systems or qubits, to optimize estimation processes. We here exploit the Quantum Zeno Effect (QZE) as a tool for maximizing information obtainable by quantum sensors, with a specific focus on the level avoided crossing (LAC) phenomenon in qubit systems. While the estimation of the LAC energy splitting has been extensively studied, we emphasize the crucial role that the QZE can play in estimating the coupling strength. We introduce the concept of information amplification by the QZE for a LAC system under off-resonant conditions. The proposed approach has implications for AC magnetic field sensing and the caracterization of complex systems, including many-spin systems requiring the estimation of spin-spin couplings. Overall, our findings contribute to the advancement of quantum sensing by leveraging the QZE for improved control and information extraction.
description: 14 pages, 6 figures
The measurement of scintillation emission spectra by a coincident photon counting technique
Creators: name: McMillan, J E
name: Martoff, C J
Publisher: name: arXiv
Year: 2006
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: In the evaluation of novel scintillators, it is important to ensure that the spectrum of the light emitted by the scintillator is well matched to the response of the photomultiplier. In attempting to measure this spectrum using radioactive sources, it is found that so few photons are emitted per scintillation event that conventional spectroscopic techniques cannot easily be used. A simple photon counting technique is presented, using two photomultipliers operated in coincidence, the one viewing the scintillator directly, while the other views it through a monochromator. This system allows the spectrum to be measured without using specially cooled photomultipliers, intense radioactive sources or particle beams.
description: 9 pages, 3 figures. Submitted to Measurement Science and Technology
Genetic sequencing algorithms allow for the discovery of directed patterns in patient sharing pathways
Creators: name: Bobak, Carly
name: O'Malley, James
Publisher: name: F1000 Research Limited
Year: 2021

description: The physician-patient relationship may play an important role in patient health outcomes. In a well-managed care episode, physicians do not act as isolated actors, but collectively as groups wherein each physician contributes to the patient’s overall outcome and has the opportunity to provide or receive feedback that influences their future practice of medicine. Patient sharing networks, where bipartite networks of patients linked to physicians are projected to unipartite networks where physicians are connected by edges symbolizing the occurrence of shared patients, allow researchers to better study the way the physician ecosystem influences health outcomes. Such networks can be constructed from insurance claims such as in Medicare data, or from electronic medical records, etc.

 Traditionally, these patient sharing networks have been considered undirected, where an edge exists if two physicians share a patient and doesn't otherwise. Recently, researchers have proposed using directed patient sharing networks, where the referral pathways between physicians are summarized using more sophisticated functions to retain more information about the referral paths when forming the network. In referral paths containing just two physicians, A and B, this allows for questions such as ‘does the frequency of the referral back to Physician A from Physician B following an earlier referral to B from A associate positively with patient outcomes?’. Considering more general referral paths, we can ask questions beyond two physicians into how referral paths between groups of physicians are associated with patient outcomes, and if revisits to previously seen physicians appear associated with outcomes. Furthermore, we can compare outcomes between patients who have a revisit to Physician A between specialty visits (ABACA) as opposed to patients who directly travel through a pathway of physicians (ABC).

 In this exploratory work, we propose using genetic sequencing algorithms to identify encoded motifs in physician referral pathways. We encode physician paths where the first physician seen is labeled ‘A’, the second ‘B’, and so on. We count and define the distribution of such motifs, explore the possibility of using these motifs to cluster similar patients, and consider the implications of these results in the way we describe and analyze directed patient sharing networks.
A Toolbox for Surfacing Health Equity Harms and Biases in Large Language Models
Creators: name: Pfohl, Stephen R.
name: Cole-Lewis, Heather
name: Sayres, Rory
name: Neal, Darlene
name: Asiedu, Mercy
name: Dieng, Awa
name: Tomasev, Nenad
name: Rashid, Qazi Mamunur
name: Azizi, Shekoofeh
name: Rostamzadeh, Negar
name: McCoy, Liam G.
name: Celi, Leo Anthony
name: Liu, Yun
name: Schaekermann, Mike
name: Walton, Alanna
name: Parrish, Alicia
name: Nagpal, Chirag
name: Singh, Preeti
name: Dewitt, Akeiylah
name: Mansfield, Philip
name: Prakash, Sushant
name: Heller, Katherine
name: Karthikesalingam, Alan
name: Semturs, Christopher
name: Barral, Joelle
name: Corrado, Greg
name: Matias, Yossi
name: Smith-Loud, Jamila
name: Horn, Ivor
name: Singhal, Karan
Publisher: name: arXiv
Year: 2024
Subjects: subject: Computers and Society (cs.CY)
subject: Computation and Language (cs.CL)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Large language models (LLMs) hold promise to serve complex health information needs but also have the potential to introduce harm and exacerbate health disparities. Reliably evaluating equity-related model failures is a critical step toward developing systems that promote health equity. We present resources and methodologies for surfacing biases with potential to precipitate equity-related harms in long-form, LLM-generated answers to medical questions and conduct a large-scale empirical case study with the Med-PaLM 2 LLM. Our contributions include a multifactorial framework for human assessment of LLM-generated answers for biases, and EquityMedQA, a collection of seven datasets enriched for adversarial queries. Both our human assessment framework and dataset design process are grounded in an iterative participatory approach and review of Med-PaLM 2 answers. Through our empirical study, we find that our approach surfaces biases that may be missed via narrower evaluation approaches. Our experience underscores the importance of using diverse assessment methodologies and involving raters of varying backgrounds and expertise. While our approach is not sufficient to holistically assess whether the deployment of an AI system promotes equitable health outcomes, we hope that it can be leveraged and built upon towards a shared goal of LLMs that promote accessible and equitable healthcare.
Vacuum Energy, the Cosmological Constant and Compact Extra Dimensions: Constraints from Casimir Effect Experiments
Creators: name: Perivolaropoulos, Leandros
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We consider a universe with a compact extra dimension and a cosmological constant emerging from a suitable ultraviolet cutoff on the zero point energy of the vacuum. We derive the Casimir force between parallel conducting plates as a function of the following scales: plate separation, radius of the extra dimension and cutoff energy scale. We find that there are critical values of these scales where the Casimir force between the plates changes sign. For the cutoff energy scale required to reproduce the observed value of the cosmological constant, we find that the Casimir force changes sign and becomes repulsive for plate separations less than a critical separation $d_0=0.6mm$, assuming a zero radius of the extra dimension (no extra dimension). This prediction contradicts Casimir experiments which indicate an attractive force down to plate separations of $100nm$. For a non-zero extra dimension radius, the critical separation $d_0$ gets even larger than $0.6mm$ and remains inconsistent with Casimir force experiments. We conclude that with or without the presence of a compact extra dimension, vacuum energy with any suitable cutoff can not play the role of the cosmological constant.
description: 5 pages, 5 figures
Gauged diffeomorphisms and hidden symmetries in Kaluza-Klein theories
Creators: name: Hohm, Olaf
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We analyze the symmetries that are realized on the massive Kaluza-Klein modes in generic D-dimensional backgrounds with three non-compact directions. For this we construct the unbroken phase given by the decompactification limit, in which the higher Kaluza-Klein modes are massless. The latter admits an infinite-dimensional extension of the three-dimensional diffeomorphism group as local symmetry and, moreover, a current algebra associated to SL(D-2,R) together with the diffeomorphism algebra of the internal manifold as global symmetries. It is shown that the `broken phase' can be reconstructed by gauging a certain subgroup of the global symmetries. This deforms the three-dimensional diffeomorphisms to a gauged version, and it is shown that they can be governed by a Chern-Simons theory, which unifies the spin-2 modes with the Kaluza-Klein vectors. This provides a reformulation of D-dimensional Einstein gravity, in which the physical degrees of freedom are described by the scalars of a gauged non-linear sigma model based on SL(D-2,R)/SO(D-2), while the metric appears in a purely topological Chern-Simons form.
description: 23 pages, minor changes, v3: published version
Strangeness Chemical Equilibration in QGP at RHIC and LHC
Creators: name: Letessier, Jean
name: Rafelski, Johann
Publisher: name: arXiv
Year: 2006
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study, in the dynamically evolving QGP fireball formed in relativistic heavy ion collisions at RHIC and LHC, the growth of strangeness yield toward and beyond the chemical equilibrium. We account for the contribution of the direct strangeness production and evaluate the thermal-QCD strangeness production mechanisms. The specific yield of strangeness per entropy, s/S, is the primary target variable. We explore the effect of collision impact parameter, i.e., fireball size, on kinetic strangeness chemical equilibration in QGP. Insights gained in study the RHIC data with regard to the dynamics of the fireball are applied to the study strangeness production at the LHC. We use these results and consider the strange hadron relative particle yields at RHIC and LHC in a systematic fashion. We consider both the dependence on s/S and directly participant number dependence.
description: 21 pages, 13 figures, PRC in press. Strangeness production recomputed with K-factor K=1.7. Particle yields recomputed with SHARE 2.1
The universal functorial equivariant Lefschetz invariant
Creators: name: Weber, Julia
Publisher: name: arXiv
Year: 2006
Subjects: subject: Algebraic Topology (math.AT)
subject: FOS: Mathematics
subject: 18F30, 55M20 (Primary); 18F25, 19A99, 57R91 (Secondary)

description: We introduce the universal functorial equivariant Lefschetz invariant for endomorphisms of finite proper G-CW-complexes, where G is a discrete group. We use K_0 of the category of "phi-endomorphisms of finitely generated free RPi(G,X)-modules". We derive results about fixed points of equivariant endomorphisms of cocompact proper smooth G-manifolds.
description: 33 pages; shortened version of the author's PhD thesis, supervised by Wolfgang Lueck, Westfaelische Wilhelms-Universitaet Muenster, 2005
Non-catastrophic Encoders and Encoder Inverses for Quantum Convolutional Codes
Creators: name: Grassl, Markus
name: Roetteler, Martin
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: Information Theory (cs.IT)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: We present an algorithm to construct quantum circuits for encoding and inverse encoding of quantum convolutional codes. We show that any quantum convolutional code contains a subcode of finite index which has a non-catastrophic encoding circuit. Our work generalizes the conditions for non-catastrophic encoders derived in a paper by Ollivier and Tillich (quant-ph/0401134) which are applicable only for a restricted class of quantum convolutional codes. We also show that the encoders and their inverses constructed by our method naturally can be applied online, i.e., qubits can be sent and received with constant delay.
description: 6 pages, 1 figure, submitted to 2006 IEEE International Symposium on Information Theory
In situ mineral geochemistry as a guide to ore-forming processes
Creators: name: Tanner, Dominique
Publisher: name: Canberra, ACT : The Australian National University
Year: 2017
Subjects: subject: Ores
subject: Isotope geology
subject: Trace elements Analysis

description: Isotopic and trace element analyses are essential to our understanding ore-forming processes, but traditionally these techniques have required bulk digestion of rocks and minerals. Recent advances in in situ microanalytical techniques permit us to analyse samples on a mineral-by mineral basis and probe the chemistry of individual growth bands in minerals, providing a near-continuous record in any zoned mineral. This thesis is composed of five studies using the in situ geochemistry of 'gangue' (non-ore) minerals to elucidate cryptic ore-forming processes that are obscured using conventional analyses. The first half of this thesis presents coupled isotopic and trace element analyses in quartz and pyrite from magmatic-hydrothermal Cu-Au deposits. These studies revealed complex chemical zonation, providing a detailed record of cryptic fluid chemistry and depositional processes. A distinct isotopic signature and residual metastable silica hydrates in quartz microcrystals from the El Indio deposit, Chile provided the first evidence for silica maturation in a high-temperature environment and the first evidence for non-equilibrium isotope fractionation in quartz. The second half of this thesis focuses on the trace element chemistry of minerals from the Bellevue Core, a ~3 km drillcore intersecting the upper half of the Bushveld Complex, South Africa - the largest known repository of platinum-group elements (PGEs). These studies revealed a prospective PGE horizon and provide the first evidence for extensive equilibration of plagioclase in cumulate rocks.
Cosmic dynamics in the era of Extremely Large Telescopes
Creators: name: Liske, J.
name: Grazian, A.
name: Vanzella, E.
name: Dessauges, M.
name: Viel, M.
name: Pasquini, L.
name: Haehnelt, M.
name: Cristiani, S.
name: Pepe, F.
name: Avila, G.
name: Bonifacio, P.
name: Bouchy, F.
name: Dekker, H.
name: Delabre, B.
name: D'Odorico, S.
name: D'Odorico, V.
name: Levshakov, S.
name: Lovis, C.
name: Mayor, M.
name: Molaro, P.
name: Moscardini, L.
name: Murphy, M. T.
name: Queloz, D.
name: Shaver, P.
name: Udry, S.
name: Wiklind, T.
name: Zucker, S.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: The redshifts of all cosmologically distant sources are expected to experience a small, systematic drift as a function of time due to the evolution of the Universe's expansion rate. A measurement of this effect would represent a direct and entirely model-independent determination of the expansion history of the Universe over a redshift range that is inaccessible to other methods. Here we investigate the impact of the next generation of Extremely Large Telescopes on the feasibility of detecting and characterising the cosmological redshift drift. We consider the Lyman alpha forest in the redshift range 2 < z < 5 and other absorption lines in the spectra of high redshift QSOs as the most suitable targets for a redshift drift experiment. Assuming photon-noise limited observations and using extensive Monte Carlo simulations we determine the accuracy to which the redshift drift can be measured from the Ly alpha forest as a function of signal-to-noise and redshift. Based on this relation and using the brightness and redshift distributions of known QSOs we find that a 42-m telescope is capable of unambiguously detecting the redshift drift over a period of ~20 yr using 4000 h of observing time. Such an experiment would provide independent evidence for the existence of dark energy without assuming spatial flatness, using any other cosmological constraints or making any other astrophysical assumption.
description: Accepted for publication in MNRAS, 27 pages, 19 figures
CAPD::DynSys: a flexible C++ toolbox for rigorous numerical analysis of dynamical systems
Creators: name: Kapela, Tomasz
name: Mrozek, Marian
name: Wilczak, Daniel
name: Zgliczyński, Piotr
Publisher: name: arXiv
Year: 2020
Subjects: subject: Numerical Analysis (math.NA)
subject: Mathematical Software (cs.MS)
subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: We present the CAPD::DynSys library for rigorous numerical analysis of dynamical systems. The basic interface is described together with several interesting case studies illustrating how it can be used for computer-assisted proofs in dynamics of ODEs.
description: 25 pages, 4 figures, 11 full C++ examples
Diffusion of excitation and power-law localization in long-range-coupled strongly disordered systems
Creators: name: Kawa, Karol
name: Machnikowski, Paweł
Publisher: name: arXiv
Year: 2020
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: We investigate diffusion of excitation in one- and two-dimensional lattices with random on-site energies and deterministic long-range couplings (hopping) inversely proportional to the distance. Three regimes of diffusion are observed in strongly disordered systems: ballistic motion at short time, standard diffusion for intermediate times, and a stationary phase (saturation) at long times. We propose an analytical solution valid in the strong-coupling regime which explains the observed dynamics and relates the ballistic velocity, diffusion coefficient, and asymptotic diffusion range to the system size and disorder strength via simple formulas. We show also that in the long-time asymptotic limit of diffusion from a single site the occupations form a heavy-tailed power-law distribution.
title: Anisotropic hyperelastic constitutive models for finite deformations combining material theory and data-driven approaches with application to cubic lattice metamaterials
Creators: name: Fernández, Mauricio
name: Jamshidian, Mostafa
name: Böhlke, Thomas
name: Kersting, Kristian
name: Weeger, Oliver
Publisher: name: Springer
Year: 2021

description: This work investigates the capabilities of anisotropic theory-based, purely data-driven and hybrid approaches to model the homogenized constitutive behavior of cubic lattice metamaterials exhibiting large deformations and buckling phenomena. The effective material behavior is assumed as hyperelastic, anisotropic and finite deformations are considered. A highly flexible analytical approach proposed by Itskov (Int J Numer Methods Eng 50(8): 1777–1799, 2001) is taken into account, which ensures material objectivity and fulfillment of the material symmetry group conditions. Then, two non-intrusive data-driven approaches are proposed, which are built upon artificial neural networks and formulated such that they also fulfill the objectivity and material symmetry conditions. Finally, a hybrid approach combing the approach of Itskov (Int J Numer Methods Eng 50(8): 1777–1799, 2001) with artificial neural networks is formulated. Here, all four models are calibrated with simulation data of the homogenization of two cubic lattice metamaterials at finite deformations. The data-driven models are able to reproduce the calibration data very well and reproduce the manifestation of lattice instabilities. Furthermore, they achieve superior accuracy over the analytical model also in additional test scenarios. The introduced hyperelastic models are formulated as general as possible, such that they can not only be used for lattice structures, but for any anisotropic hyperelastic material.
Evidence for strange stars from joint observation of harmonic absorption bands and of redshift
Creators: name: Bagchi, Manjari
name: Ray, Subharthi
name: Dey, Mira
name: Dey, Jishnu
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: From recent reports on terrestrial heavy ion collision experiments it appears that one may not obtain information about the existence of asymptotic freedom (AF) and chiral symmetry restoration (CSR) for quarks of QCD at high density. This information may still be obtained from compact stars - if they are made up of strange quark matter. Very high gravitational redshift lines (GRL), seen from some compact stars, seem to suggest high ratios of mass and radius (M/R) for them. This is suggestive of strange stars (SS) and can in fact be fitted very well with SQM equation of state deduced with built in AF and CSR. In some other stars broad absorption bands appear at about ~ 0.3 keV and multiples thereof, that may fit in very well with resonance with harmonic compressional breathing mode frequencies of these SS. Emission at these frequencies are also observed in six stars. If these two features of large GRL and BAB were observed together in a single star, it would strengthen the possibility for the existence of SS in nature and would vindicate the current dogma of AF and CSR that we believe in QCD. Recently, in 4U 1700-24, both features appear to be detected, which may well be interpreted as observation of SS - although the group that analyzed the data did not observe this possibility. We predict that if the shifted lines, that has been observed, are from neon with GRL shift z = 0.4 - then the compact object emitting it is a SS of mass 1.2 M_sun and radius 7 km. In addition the fit to the spectrum leaves a residual with broad dips at 0.35 keV and multiples thereof, as in 1E1207-5209 which is again suggestive of SS.
description: 5 pages, 4 figures, accepted for publication in the MNRAS
Demonstrating Mobile Manipulation in the Wild: A Metrics-Driven Approach
Creators: name: Bajracharya, Max
name: Borders, James
name: Cheng, Richard
name: Helmick, Dan
name: Kaul, Lukas
name: Kruse, Dan
name: Leichty, John
name: Ma, Jeremy
name: Matl, Carolyn
name: Michel, Frank
name: Papazov, Chavdar
name: Petersen, Josh
name: Shankar, Krishna
name: Tjersland, Mark
Publisher: name: arXiv
Year: 2024
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: We present our general-purpose mobile manipulation system consisting of a custom robot platform and key algorithms spanning perception and planning. To extensively test the system in the wild and benchmark its performance, we choose a grocery shopping scenario in an actual, unmodified grocery store. We derive key performance metrics from detailed robot log data collected during six week-long field tests, spread across 18 months. These objective metrics, gained from complex yet repeatable tests, drive the direction of our research efforts and let us continuously improve our system's performance. We find that thorough end-to-end system-level testing of a complex mobile manipulation system can serve as a reality-check for state-of-the-art methods in robotics. This effectively grounds robotics research efforts in real world needs and challenges, which we deem highly useful for the advancement of the field. To this end, we share our key insights and takeaways to inspire and accelerate similar system-level research projects.
description: Presented at RSS 2023 [Best Demo Paper Award]
Effects of Weak Links in the Nonlinear Microwave Response of MgB2 Superconductor
Creators: name: Gallitto, A. Agliolo
name: Bonsignore, G.
name: Giunchi, G.
name: Vigni, M. Li
Publisher: name: arXiv
Year: 2006
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We report experimental results of second-harmonic (SH) response at microwave frequency in several ceramic MgB2 samples, prepared by different methods. The SH signal has been investigated as a function of the temperature and DC magnetic field. The investigation has been carried out at low magnetic fields, where nonlinear processes arising from motion of Abrikosov fluxons are ineffective. We show that the low-temperature SH emission is ascribable to processes involving weak links. Comparison among the peculiarities of the SH signal radiated by the different samples shows that the presence of weak links strongly depends on the sample preparation method, as well as the purity and morphology of the components used for the preparation.
description: 14 pages, 4 figures, 1 table; Proceedings of 9th Symposium of High Temperature Superconductors in High Frequency Fields (25-28 June 2006, Cardiff, UK)
An efficient adaptive variational quantum solver of the Schrodinger equation based on reduced density matrices
Creators: name: Liu, Jie
name: Li, Zhenyu
name: Yang, Jinlong
Publisher: name: arXiv
Year: 2020
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Recently, an adaptive variational algorithm termed Adaptive Derivative-Assembled Pseudo-Trotter ansatz Variational Quantum Eigensolver (ADAPT-VQE) has been proposed by Grimsley et al. (Nat. Commun. 10, 3007) while the number of measurements required to perform this algorithm scales O(N^8). In this work, we present an efficient adaptive variational quantum solver of the Schrodinger equation based on ADAPT-VQE together with the reduced density matrix reconstruction approach, which reduces the number of measurements from O(N^8) to O(N^4). This new algorithm is quite suitable for quantum simulations of chemical systems on near-term noisy intermediate-scale hardware due to low circuit complexity and reduced measurement. Numerical benchmark calculations for small molecules demonstrate that this new algorithm provides an accurate description of the ground-state potential energy curves. In addition, we generalize this new algorithm for excited states with the variational quantum deflation approach and achieve the same accuracy as ground-state simulations.
description: 27 pages and 5 figures
Picotesla-sensitivity microcavity optomechanical magnetometry
Creators: name: Hu, Zhi-Gang
name: Gao, Yi-Meng
name: Liu, Jian-Fei
name: Yang, Hao
name: Wang, Min
name: Lei, Yuechen
name: Zhou, Xin
name: Li, Jincheng
name: Cao, Xuening
name: Liang, Jinjing
name: Hu, Chao-Qun
name: Li, Zhilin
name: Lau, Yong-Chang
name: Cai, Jian-Wang
name: Li, Bei-Bei
Publisher: name: arXiv
Year: 2024
Subjects: subject: Optics (physics.optics)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Cavity optomechanical systems have enabled precision sensing of magnetic fields, by leveraging the optical resonance-enhanced readout and mechanical resonance-enhanced response. Previous studies have successfully achieved scalable and reproducible microcavity optomechanical magnetometry (MCOM) by incorporating Terfenol-D thin films into high-quality ($Q$) factor whispering gallery mode (WGM) microcavities. However, the sensitivity was limited to 585 pT/Hz$^{1/2}$, over 20 times inferior to those using Terfenol-D particles. In this work, we propose and demonstrate a high-sensitivity and scalable MCOM approach by sputtering a FeGaB thin film onto a high-$Q$ SiO$_2$ WGM microdisk. Theoretical studies are conducted to explore the magnetic actuation constant and noise-limited sensitivity by varying the parameters of the FeGaB film and SiO$_2$ microdisk. Multiple magnetometers with different radii are fabricated and characterized. By utilizing a microdisk with a radius of 355 $μ$m and a thickness of 1 $μ$m, along with a FeGaB film with a radius of 330 $μ$m and a thickness of 1.3 $μ$m, we have achieved a remarkable peak sensitivity of 1.68 pT/Hz$^{1/2}$ at 9.52 MHz. This represents a significant improvement of over two orders of magnitude compared with previous studies employing sputtered Terfenol-D film. Notably, the magnetometer operates without a bias magnetic field, thanks to the remarkable soft magnetic properties of the FeGaB film. Furthermore, as a proof-of-concept, we have demonstrated the real-time measurement of a pulsed magnetic field simulating the corona current in a high-voltage transmission line using our developed magnetometer. These high-sensitivity magnetometers hold great potential for various applications, such as magnetic induction tomography and corona current monitoring.
Magnetic Fields in the Aftermath of Phase Transitions
Creators: name: Vachaspati, Tanmay
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: Other Condensed Matter (cond-mat.other)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The COSLAB effort has focussed on the formation of topological defects during phase transitions. Yet there is another potentially interesting signature of cosmological phase transitions, which also deserves study in the lab. This is the generation of magnetic fields during phase transitions. In particular, cosmological phase transitions that also lead to preferential production of matter over antimatter (``baryogenesis''), are expected to produce helical (left-handed) magnetic fields. The study of analogous processes in the lab can yield important insight into the production of helical magnetic fields, and the observation of such fields in the universe can be invaluable for both particle physics and cosmology.
description: 9 pages. Contribution to the Royal Society Discussion Meeting ``Cosmology Meets Condensed Matter'', January 28-29, 2008
Dark energy and dark matter as curvature effects
Creators: name: Capozziello, S.
name: Cardone, V. F.
name: Troisi, A.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Astrophysical observations are pointing out huge amounts of dark matter and dark energy needed to explain the observed large scale structures and cosmic accelerating expansion. Up to now, no experimental evidence has been found, at fundamental level, to explain such mysterious components. The problem could be completely reversed considering dark matter and dark energy as shortcomings of General Relativity and claiming for the correct theory of gravity as that derived by matching the largest number of observational data. As a result, accelerating behavior of cosmic fluid and rotation curves of spiral galaxies are reproduced by means of curvature effects.
description: 4 pages, 1 figure, revised version