cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Lattice Monte Carlo calculations for unitary fermions in a harmonic trap
Creators: name: Endres, Michael G.
name: Kaplan, David B.
name: Lee, Jong-Wan
name: Nicholson, Amy N.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Nuclear Theory (nucl-th)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We present a new lattice Monte Carlo approach developed for studying large numbers of strongly interacting nonrelativistic fermions, and apply it to a dilute gas of unitary fermions confined to a harmonic trap. Our lattice action is highly improved, with sources of discretization and finite volume errors systematically removed; we are able to demonstrate the expected volume scaling of energy levels of two and three untrapped fermions, and to reproduce the high precision calculations published previously for the ground state energies for N = 3 unitary fermions in a box (to within our 0.3% uncertainty), and for N = 3, . . ., 6 unitary fermions in a harmonic trap (to within our ~ 1% uncertainty). We use this action to determine the ground state energies of up to 70 unpolarized fermions trapped in a harmonic potential on a lattice as large as 64^3 x 72; our approach avoids the use of importance sampling or calculation of a fermion determinant and employs a novel statistical method for estimating observables, allowing us to generate ensembles as large as 10^8 while requiring only relatively modest computational resources.
description: 48 pages, 19 figures, published version, some text revised, typos corrected, title changed in journal; previously "Unitary fermions on the lattice I: in a harmonic trap"
Protracted phonological development in Granada Spanish : a case study
Creators: name: Klassen, Josiah
Publisher: name: University of British Columbia
Year: 2017

description: This case study examines single-word productions of “Emilio”, a Spanish-speaking boy from Granada with protracted phonological development (PPD), at ages 4;8 and 7;6. Emilio was the only child in a cohort of 15 to exhibit persisting difficulties at the second time point. At time 2, he showed differences in word-initial /r/, syllable-final /ɾ/ and one polysyllabic word, hipopótamo. In an acoustic comparison of /r/ data from children aged 4 to 9 years (Carballo & Mendoza, 2000), Emilio’s /r/ attempts had higher formant frequencies (F1 and F2), less distinct occlusions and apertures, and longer duration. The current study examines Emilio’s first dataset to determine phonological factors that may have predicted persisting PPD. The analysis adopts a nonlinear phonological framework (Bernhardt & Stemberger, 1998), and evaluates his data with respect to 16 expectations about Spanish acquisition derived from research literature. His 4-year-old phonological skills are compared with those of two 4-year-old peers who had similar whole word match (WWM) scores at the first data collection (WWM is the percent of words produced that match their targets; Bernhardt et al., 2015a). For Emilio, global measures including WWM were within the expected range for 4-year-olds with PPD. Three word structure measures, however, differentiated his phonology at age 4 from his two peers: overall word shape match (WSM), WSM of words with clusters, and word-initial cluster match (accuracy) in stressed syllables. (WSM is the percent of words produced with consonant-vowel [CV] sequences matching the adult target sequences; Bernhardt et al., 2015a.) Emilio also showed more difficulty with dorsal consonants, and words with alternating coronal-labial cross-vowel sequences than Sofía and Tomás. Those particular variables may be good candidates for predicting long-term difficulty. Other measures, including liquid and fricative matches and phonological processes, were not differentiators for these 4-year-olds. These results highlight the relevance of word structure for assessment and treatment of PPD, in alignment with Bernhardt et al. (2015a) and Schretlen (2013). The relevance of two ways of measuring WSM, with or without glides in the consonant category, are discussed. Further research is needed to confirm or disprove the usefulness of these predictors.
dsmo17.pdf
Creators: name: Babaki, Behrouz
name: Van Daele, Dries
name: Weytjens, Bram
name: Guns, Tias
Publisher: name: figshare
Year: 2021
Subjects: subject: 170203 Knowledge Representation and Machine Learning
subject: FOS: Psychology
subject: 10303 Optimisation
subject: FOS: Mathematics
subject: 60102 Bioinformatics
subject: FOS: Computer and information sciences

description: "A Branch-and-Cut Algorithm for Constrained Graph Clustering" presented at the workshop "Data Science meets Optimization (DSO)", Padova, Italy (2017).
Markovian Master Equations: A Critical Study
Creators: name: Rivas, Ángel
name: Plato, A. Douglas K.
name: Huelga, Susana F.
name: Plenio, Martin B.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We derive Markovian master equations of single and interacting harmonic systems in different scenarios, including strong internal coupling. By comparing the dynamics resulting from the corresponding Markovian master equations with exact numerical simulations of the evolution of the global system, we precisely delimit their validity regimes and assess the robustness of the assumptions usually made in the process of deriving the reduced dynamics. The proposed method is sufficiently general to suggest that the conclusions made here are widely applicable to a large class of settings involving interacting chains subject to a weak interaction with an environment.
description: 40 pages, 14 figures, final version
Transverse Spin Structure of the Nucleon through Target Single Spin Asymmetry in Semi-Inclusive Deep-Inelastic $(e,e^\prime π^\pm)$ Reaction at Jefferson Lab
Creators: name: Gao, H.
name: Gamberg, L.
name: Chen, J. -P.
name: Qian, X.
name: Qiang, Y.
name: Huang, M.
name: Afanasev, A.
name: Anselmino, M.
name: Avakian, H.
name: Cates, G.
name: Chudakov, E.
name: Cisbani, E.
name: de Jager, C.
name: Garibaldi, F.
name: Hu, B. T.
name: Jiang, X.
name: Kumar, K. S.
name: Li, X. M.
name: Lu, H. J.
name: Meziani, Z. -E.
name: Ma, B. -Q.
name: Mao, Y. J.
name: Peng, J. -C.
name: Prokudin, A.
name: Schlegel, M.
name: Souder, P.
name: Xiao, Z. G.
name: Ye, Y.
name: Zhu, L.
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to perform precision studies of the transverse spin and transverse-momentum-dependent structure in the valence quark region for both the proton and the neutron. In this paper, we focus our discussion on a recently approved experiment on the neutron as an example of the precision studies planned at JLab. The new experiment will perform precision measurements of target Single Spin Asymmetries (SSA) from semi-inclusive electro-production of charged pions from a 40-cm long transversely polarized $^3$He target in Deep-Inelastic-Scattering kinematics using 11 and 8.8 GeV electron beams. This new coincidence experiment in Hall A will employ a newly proposed solenoid spectrometer (SoLID). The large acceptance spectrometer and the high polarized luminosity will provide precise 4-D ($x$, $z$, $P_T$ and $Q^2$) data on the Collins, Sivers, and pretzelocity asymmetries for the neutron through the azimuthal angular dependence. The full 2$π$ azimuthal angular coverage in the lab is essential in controlling the systematic uncertainties. The results from this experiment, when combined with the proton Collins asymmetry measurement and the Collins fragmentation function determined from the e$^+$e$^-$ collision data, will allow for a quark flavor separation in order to achieve a determination of the tensor charge of the d quark to a 10% accuracy. The extracted Sivers and pretzelocity asymmetries will provide important information to understand the correlations between the quark orbital angular momentum and the nucleon spin and between the quark spin and nucleon spin.
description: 23 pages, 13 figures, minor corrections, matches published version
Predicting and witnessing data races using CSP
Creators: name: Carril Rodriguez, Luis Manuel
name: Tichy, Walter F.
Publisher: name: Karlsruhe
Year: 2015

description: Detecting and debugging data races is a complex task due to the large number of interleavings possible in a parallel program. Most tools can find the data races reliably in an observed execution, but they miss errors in alternative reorderings of events. In this paper we describe an automated approach to generate, from a single program trace, a model in CSP with alternative interleavings. We check for data races patterns and obtain a witness that allows the reproduction of errors. Reproduction reduces the developer effort to correct the error.
Gaps tunable by electrostatic gates in strained graphene
Creators: name: Low, T.
name: Guinea, F.
name: Katsnelson, M. I.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We show that when the pseudomagnetic fields created by long wavelength deformations are appropriately coupled with a scalar electric potential, a significant energy gap can emerge due to the formation of a Haldane state. Ramifications of this physical effect are examined through the study of various strain geometries commonly seen in experiments, such as strain superlattices and wrinkled suspended graphene. Of particular technological importance, we consider setup where this gap can be tunable through electrostatic gates, allowing for the design of electronic devices not realizable with other materials.
description: See accompanying Physics Synopsis at http://physics.aps.org/synopsis-for/10.1103/PhysRevB.83.195436
Proof of the Yano-Obata Conjecture for holomorph-projective transformations
Creators: name: Matveev, Vladimir S.
name: Rosemann, Stefan
Publisher: name: arXiv
Year: 2011
Subjects: subject: Differential Geometry (math.DG)
subject: Analysis of PDEs (math.AP)
subject: Complex Variables (math.CV)
subject: FOS: Mathematics

description: We prove the classical Yano-Obata conjecture by showing that the connected component of the group of holomorph-projective transformations of a closed, connected Riemannian Kähler manifold consists of isometries unless the metric has constant positive holomorphic curvature.
description: 28 pages, 3 pictures. The (v2) version contains in addition a relation between h-projectively equivalent metrics and hamiltonian 2-forms studies in math.DG/0202280, math.DG/0401320, math.DG/0511118, math.DG/0511119. In the (v3) version, we also added an appendix with the h-projectively invariant formulation of the main equations and, as their application, an alternative proof of Lemma 7
Z-mediated charge and CP asymmetries and FCNCs in $B_{d,s}$ processes
Creators: name: Chen, Chuan-Hung
name: Geng, Chao-Qiang
name: Wang, Wei
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We show model-independently that the negative like-sign charge asymmetry $(-A^b_{s\ell})$ is less than $ 3.16\times 10^{-3}$ when the constraints from the $B_q-\bar B_q$ mixings and the time-dependent CP asymmetries (CPAs) for $B_q\to J/ΨM_q$ with $M_q=K,ϕ$ and $q=d,s$ are taken into account. Although the result is smaller than the measured value by the DØ Collaboration at Fermilab, there is still plenty of room to have new physics, which is sensitive to new CP violating effects, as the standard model (SM) prediction is $(2.3_{-0.5}^{+0.6})\times 10^{-4}$. To illustrate the potential large $|A^{b}_{s\ell}|$, we show the influence of new $SU(2)_L$ singlet exotic quarks in the vector-like quark model, where the $Z$-mediated flavor changing neutral currents (FCNCs) are generated at tree level. In particular, we demonstrate that (a) the like-sign charge asymmetry could be enhanced by a factor of two in magnitude; (b) the CPA of $\sin2β^{J/Ψϕ}_s$ could reach to $-15%$; (c) the CPA of $\sin2β_{ϕK_S}$ could be higher than $\sin2β_{J/ΨK_S}$ when $|A^b_{s\ell}|$ is larger than the SM prediction; and (d) the branching ratio for $B_s\to μ^+ μ^-$ could be as large as $0.6\times 10^{-8}$.
description: 1+19 pages, 8 figures, typos corrected and references added, version to appear in JHEP
Roadmap enhanced improvement to the VSIMM tracker via a constrained stochastic context free grammar
Creators: name: Gao, Sijia
Publisher: name: University of British Columbia
Year: 2017

description: In this thesis, we aim to improve the tracking accuracy for targets that are moving confined to a roadmap given target observations. We build a 3-level model for this roadmap constrained target tracking problem. At the first level, the roadmap is formulated as a directed, weighted graph; at the second level, the target's trajectory is characterized via an ordered sequence of intersections it traverses. The target's roadmap constrained trajectory exploits moving directions and road or intersection names and is modeled via a CSCFG (constrained stochastic context free grammar). CSCFG arises from language processing models and is more general than Markov chains and SCFGs (stochastic context free grammar). Bayesian signal processing algorithms for CSCFGs with polynomial time complexity are also derived; finally, the target's kinematics are described by the baseline VSIMM (variable structure interacting multiple model). Based on the 3-level model, we present a novel CSCFG driven sequential particle filtering algorithm that estimates the target's states. This algorithm comprises a CSCFG meta-level parsing algorithm that operates in conjunction with a base-level VSIMM tracking algorithm. Extensive numerical results using simulated ground moving target indicator (GMTI) radar measurements show substantial improvement in target tracking accuracy compared with VSIMM tracker. To further evaluate the effectiveness of CSCFG, we also illustrate two anomalous trajectories for targets moving on grid roadmap. These trajectories show suspicious intents of targets and cause attention of radar operators. Numerical examples using simulated GMTI radar measurements show that CSCFG based Viterbi tracker can significantly decrease the tracking error compared with HMM (hidden Markov model) Viterbi tracker. Future work include more flexible constructions of the roadmap graph and extensions from CSCFGs to matrix grammars to model more complicated spatio-temporal trajectories.
Universality of superconducting gaps in overdoped Ba0.3K0.7Fe2As2 observed by angle-resolved photoemission spectroscopy
Creators: name: Nakayama, K.
name: Sato, T.
name: Richard, P.
name: Xu, Y. -M.
name: Kawahara, T.
name: Umezawa, K.
name: Qian, T.
name: Neupane, M.
name: Chen, G. F.
name: Ding, H.
name: Takahashi, T.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We have performed angle-resolved photoemission spectroscopy on the overdoped Ba$_{0.3}$K$_{0.7}$Fe$_2$As$_2$ superconductor ($T_c$ = 22 K). We demonstrate that the superconducting (SC) gap on each Fermi surface (FS) is nearly isotropic whereas the gap value varies from 4.4 to 7.9 meV on different FSs. By comparing with under- and optimally-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$, we find that the gap value on each FS nearly scales with $T_c$ over a wide doping range (0.25 $\textyen leq$ $x$ $\textyen leq$ 0.7). Although the FS volume and the SC gap magnitude are strongly doping dependent, the multiple nodeless gaps can be commonly fitted by a single gap function assuming pairing up to the second-nearest-neighbor, suggesting the universality of the short-range pairing states with the $s_{\yenpm}$-wave symmetry.
description: 5 pages, 4 figures
Energy Optimization in NCFET-based Processors
Creators: name: Salamin, Sami
name: Rapp, Martin
name: Amrouch, Hussam
name: Gerstlauer, Andreas
name: Henkel, Jörg
Publisher: name: Institute of Electrical and Electronics Engineers (IEEE)
Year: 2020

description: Energy consumption is a key optimization goal for all modern processors. Negative Capacitance Field-Effect Transistors (NCFETs) are a leading emerging technology that promises outstanding performance in addition to better energy efficiency. Thickness of the additional ferroelectric layer, frequency, and voltage are the key parameters in NCFET technology that impact the power and frequency of processors. However, their joint impact on energy optimization has not been investigated yet.In this work, we are the first to demonstrate that conventional (i.e., NCFET-unaware) dynamic voltage/frequency scaling (DVFS) techniques to minimize energy are sub-optimal when applied to NCFET-based processors. We further demonstrate that state-of-the-art NCFET-aware voltage scaling for power minimization is also sub-optimal when it comes to energy. This work provides the first NCFET-aware DVFS technique that optimizes the processor's energy through optimal runtime frequency/voltage selection. In NCFETs, energy-optimal frequency and voltage are dependent on the workload and technology parameters. Our NCFET-aware DVFS technique considers these effects to perform optimal voltage/frequency selection at runtime depending on workload characteristics. Results show up to 90 % energy savings compared to conventional DVFS techniques. Compared to state-of-the-art NCFET-aware power management, our technique provides up to 72 % energy savings along with 3.7x higher performance.
Klein Tunneling and Berry Phase $π$ in Bilayer Graphene with a Band Gap
Creators: name: Park, Sunghun
name: Sim, H. -S.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Klein tunneling in gapless bilayer graphene, perfect reflection of electrons injecting normal to a pn junction, is expected to disappear in the presence of energy band gap induced by external gates. We theoretically show that the Klein effect still exists in gapped bilayer graphene, provided that the gaps in the n and p regions are balanced such that the polarization of electron pseudospin has the same normal component to the bilayer plane in the regions. We attribute the Klein effect to Berry phase $π$ (rather than the conventional value $2 π$ of bilayer graphene) and to electron-hole and time-reversal symmetries. The Klein effect and the Berry phase $π$ can be identified in an electronic Veselago lens, an important component of graphene-based electron optics.
description: Revised version; Main text (4 pages, 4 figures) + Supplemetal material (3 pages, 1 figure)
An Early Universe Model with Stiff Matter and a Cosmological Constant
Creators: name: Oliveira-Neto, G.
name: Monerat, G. A.
name: Silva, E. V. Corrêa
name: Neves, C.
name: Ferreira, L. G.
Publisher: name: arXiv
Year: 2011
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In the present work, we study the quantum cosmology description of a Friedmann-Robertson-Walker model in the presence of a stiff matter perfect fluid and a negative cosmological constant. We work in the Schutz's variational formalism and the spatial sections have constant negative curvature. We quantize the model and obtain the appropriate Wheeler-DeWitt equation. In this model the states are bounded therefore we compute the discrete energy spectrum and the corresponding eigenfunctions. In the present work, we consider only the negative eigenvalues and their corresponding eigenfunctions. This choice implies that the energy density of the perfect fluid is negative. A stiff matter perfect fluid with this property produces a model with a bouncing solution, at the classical level, free from an initial singularity. After that, we use the eigenfunctions in order to construct wave packets and evaluate the time-dependent expectation value of the scale factor. We find that it oscillates between maximum and minimum values. Since the expectation value of the scale factor never vanishes, we confirm that this model is free from an initial singularity, also, at the quantum level.
description: 12 Pages, 4 Figures. Final version. Accepted for publication in the Proceedings of the 8th Friedmann Seminar, Rio de Janeiro, 2011. We restricted our attention to treat the case where the stiff matter has negative energy eigenvalues, following the referee's suggestion
Cosmological Evolution of Vacuum and Cosmic Acceleration
Creators: name: Kaya, Ali
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: It is known that the unregularized expressions for the stress-energy tensor components corresponding to subhorizon and superhorizon vacuum fluctuations of a massless scalar field in a Friedmann-Robertson-Walker background are characterized by the equation of state parameters w=1/3 and w=-1/3, which are not sufficient to produce cosmological acceleration. However, the form of the adiabatically regularized finite stress-energy tensor turns out to be completely different. By using the fact that vacuum subhorizon modes evolve nearly adiabatically and superhorizon modes have w=-1/3, we approximately determine the regularized stress-energy tensor, whose conservation is utilized to fix the time dependence of the vacuum energy density. We then show that vacuum energy density grows from zero up to H^4 in about one Hubble time, vacuum fluctuations give positive acceleration of the order of H^4/M_p^2 and they can completely alter the cosmic evolution of the universe dominated otherwise by cosmological constant, radiation or pressureless dust. Although the magnitude of the acceleration is tiny to explain the observed value today, our findings indicate that the cosmological backreaction of vacuum fluctuations must be taken into account in early stages of cosmic evolution.
description: 22 pages, 2 figures, revtex4, v4: typos corrected
Peer Review of Inferring a Continuous Distribution of Atom Coordinates from Cryo-EM Images using VAEs
Creators: name: Wankowicz, Stephanie
name: , Iris
name: , Daniel
name: , James
Publisher: name: Zenodo
Year: 2021

description: Peer review of the paper: Inferring a Continuous Distribution of Atom Coordinates from Cryo-EM Images using VAEs
Data visualization of requests for information to support construction decision-making
Creators: name: Bhat, Achintya Sheela
Publisher: name: University of British Columbia
Year: 2017

description: The construction industry is dependent on effective communication among project team members. Construction data has varied formats and size, and are communicated through a variety of mediums over the course of the project. This often leads to potential discontinuity and delays in communication between project team members. Requests for Information (RFI) are the standard form of communication between the design team and the construction team. RFI’s are not just a means of construction communication; the fact that the RFI has been generated points out that there is something wrong, missing or unclear with the existing documents and designs. Past studies have suggested that RFI’s are an indicator of deficiency in design documentation. Current RFI management systems are not sufficient to provide project participants with a medium to analyze the problems, their cause or even to easily look for information required in these RFI documents. From past studies, we know that visualization helps humans to analyze complex and vast amounts of data easily. In this study, we develop visualizations of data in the RFI documents and investigate if it has potential benefits for construction project members. To extract and transform data from the semi-structured RFI documents, we develop a framework by employing the qualitative technique of content analysis. A case study approach was employed for this study. Approximately 1,400 RFI’s were analyzed from Project A and around 500 RFI’s were analyzed from Project B. In this framework, we identify several quantitative and qualitative dimensions including time (when), spatial context (where), actor (who), reason (why), RFI Type, Domain, Property, Attribute, Entity (what) that can be used to visualize the data for analyzing the information in the RFI’s. The RFI dashboard was developed with constant feedback from industry personnel who stated that the dashboard had promising benefits for both the consultants and the owners. The contribution of this research is the development of a framework to structure and organize the information in RFI documents, the creation of a prototype dashboard visualization of RFI data, and the assessment of the potential benefits of RFI data visualization for decision making in the construction industry.
TeV Electron Spectrum for Probing Cosmic-Ray Escape from a Supernova Remnant
Creators: name: Kawanaka, Norita
name: Ioka, Kunihito
name: Ohira, Yutaka
name: Kashiyama, Kazumi
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: One of the most essential but uncertain processes for producing cosmic-rays (CRs) and their spectra is how accelerated particles escape into the interstellar space. We propose that the CR electron spectra at >~TeV energy can provide a direct probe of the CR escape complementary to the CR nuclei and gamma-rays. We calculate the electron spectra from a young pulsar embedded in the supernova remnant (SNR), like Vela, taking into account the energy-dependent CR escape. SNRs would accelerate and hence confine particles with energy up to 10^{15.5}eV. Only energetic particles can escape first, while the lower energy particles are confined and released later. Then the observed electron spectrum should have a low energy cutoff whose position marks the age of the pulsar/SNR. The low energy cutoff is observable in the $\gtrsim {\rm TeV}$ energy window, where other contaminating sources are expected to be few due to the fast cooling of electrons. The spectrum looks similar to a dark matter annihilation line if the low energy cutoff is close to the high energy intrinsic or cooling break. The future experiments such as CALET and CTA are capable of directly detecting the CR escape features toward revealing the origin of CRs.
description: 8 pages, 5 figures, accepted for publication in ApJ
Are Proto-Planetary Nebulae Shaped by a Binary? Results of a Long-Term Radial Velocity Study
Creators: name: Hrivnak, Bruce J.
name: Lu, Wenxian
name: Wefel, Katrina Loewe
name: Bohlender, David
name: Morris, S. C.
name: Woodsworth, Andrew W.
name: Scarfe, C. D.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The shaping of the nebula is currently one of the outstanding unsolved problems in planetary nebula (PN) research. Several mechanisms have been proposed, most of which require a binary companion. However, direct evidence for a binary companion is lacking in most PNs. We have addressed this problem by obtaining precise radial velocities of seven bright proto-planetary nebulae (PPNs), objects in transition from the asymptotic giant branch to the PN phases of stellar evolution. These have F-G spectral types and have the advantage over PNs of having more and sharper spectral lines, leading to better precision. Our observations were made in two observing intervals, 1991-1995 and 2007-2010, and we have included in our analysis some additional published and unpublished data. Only one of the PPNs, IRAS 22272+5435, shows a long-term variation that might tentatively be attributed to a binary companion, with P $>$ 22 years, and from this, limiting binary parameters are calculated. Selection effects are also discussed. These results set significant restrictions on the range of possible physical and orbital properties of any binary companions: they have periods greater than 25 years or masses of brown dwarfs or super-Jupiters. While not ruling out the binary hypothesis, it seems fair to say that these results do not support it.
description: 14 pages, 3 figures, to appear Astrophys J, 734 (2011 June 10)
Structure of the core of magnetic vortices in d-wave superconductors with a subdominant triplet pairing mechanism
Creators: name: Fogelstrom, Mikael
Publisher: name: arXiv
Year: 2011
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: The quasiparticle states found in the vortex core of a high-T$_{\rm{c}}$ cuprate superconductor may be probed by scanning tunneling spectroscopy. Results of such experiments have revealed typical spectra that are quite different from what is seen in conventional low-Tc superconductors. In particular the Caroli-deGennes-Matricon state at $E\sim 0$ in the core center is not seen. Instead, in a high-T$_{\rm{c}}$ vortex core, quasiparticle states are found at energies that are at a sizable fraction of the gap energy. One explanation for this could be that a finite amplitude of a competing orderparameter stabilizes in the vortex-core center. Here I will explore the possibility of nucleating a vortex-core state that locally breaks inversion symmetry. The vortex-core orderparameter is of mixed parity, a $[d + i p]$-wave, and the quasiparticle spectra in the core center lacks the E=0 states.
description: 6 pages, 5 figures, accepted for publication as a regular article in Physical Review B
Fermionic probes of local quantum criticality in one dimension
Creators: name: Rangamani, Mukund
name: Withers, Benjamin
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We study the spectral functions of fermionic operators in 1+1 dimensional SU(N) Super Yang-Mills theory with 16 supercharges at finite density using the holographically dual D1-brane geometry. This system exhibits quasi-particle peaks indicating the existence of Fermi points about which excitations have a finite relaxation time, in contrast with the Tomonaga-Luttinger model. The finite width may be attributed to the non-trivial interactions of the probe operators with the background density matrix, modeled holographically as a charged black hole. We show that the fermionic correlators can in fact be deduced from known results for fermion probes of the charged AdS4 black hole background, owing to some remarkable coincidences in supergravity truncations.
description: 5 pages, 2 figures. v2: fixed typos and added refs. published version
Due nuovi ibridi di Ophrys per la Provincia di Livorno (Toscana)
Creators: name: Romieg Soca
Publisher: name: Zenodo
Year: 2008
Subjects: Ophrys

description: Romolini R. & Soca R., 2008. Due nuovi ibridi di Ophrys per la Provincia di Livorno (Toscana). GIROS Notizie 38: 16-18.
Long-Time Coherence in Echo Spectroscopy with $π/2$--$π$--$π/2$ Pulse Sequence
Creators: name: Goussev, Arseni
name: Jacquod, Philippe
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: Other Condensed Matter (cond-mat.other)
subject: Chaotic Dynamics (nlin.CD)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: Motivated by atom optics experiments, we investigate a new class of fidelity functions describing the reconstruction of quantum states by time-reversal operations as $M_{\mathrm{Da}}(t) = | |^2$. We show that the decay of $M_{\mathrm{Da}}$ is quartic in time at short times, and that it freezes well above the ergodic value at long times, when $H_2-H_1$ is not too large. The long-time saturation value of $M_{\mathrm{Da}}$ contains easily extractable information on the strength of decoherence in these systems.
description: 5 pages, 3 figures
Intravalley Multiple Scattering of Quasiparticles in Graphene
Creators: name: Vaishnav, J. Y.
name: Anderson, Justin Q.
name: Walls, Jamie D.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We develop a theoretical description of intravalley scattering of quasiparticles in graphene from multiple short-range scatterers of size much greater than the carbon-carbon bond length. Our theory provides a method to rapidly calculate the Green's function in graphene for arbitrary configurations of scatterers. We demonstrate that non-collinear multiple scattering trajectories generate pseudospin rotations that alter quasiparticle interference, resulting in significant modifications to the shape, intensity, and pattern of the interference fringes in the local density of states (LDOS). We illustrate these effects via theoretical calculations of the LDOS for a variety of scattering configurations in single layer graphene. A clear understanding of impurity scattering in graphene is a step towards exploiting graphene's unique properties to build future devices.
On the second parameter of an $(m, p)$-isometry
Creators: name: Hoffmann, Philipp
name: Mackey, Michael
name: Searcóid, Mícheál Ó
Publisher: name: arXiv
Year: 2011
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics

description: A bounded linear operator $T$ on a Banach space $X$ is called an $(m, p)$-isometry if it satisfies the equation \sum_{k=0}^{m}(-1)^{k} {m \choose k}\|T^{k}x\|^{p} = 0$, for all $x \in X$. In this paper we study the structure which underlies the second parameter of $(m, p)$-isometric operators. We concentrate on determining when an $(m, p)$-isometry is a $(μ, q)$-isometry for some pair ($μ, q)$. We also extend the definition of $(m, p)$-isometry, to include $p=\infty$ and study basic properties of these $(m, \infty)$-isometries.
NCFET-Aware Voltage Scaling
Creators: name: Salamin, Sami
name: Rapp, Martin
name: Amrouch, Hussam
name: Pahwa, G.
name: Chauhan, Y.
name: Henkel, Jörg
Publisher: name: Institute of Electrical and Electronics Engineers (IEEE)
Year: 2019

description: Negative Capacitance Field-Effect Transistor (NCFET) has recently attracted significant attention. In the NCFET technology with a thick ferroelectric layer, voltage reduction increases the leakage power, rather than decreases, due to the negative Drain-Induced Barrier Lowering (DIBL) effect. This work is the first to demonstrate the far-reaching consequences of such an inverse dependency w.r.t. the existing power management techniques. Moreover, this work is the first to demonstrate that state-of-the-art Dynamic Voltage Scaling (DVS) techniques are sub-optimal for NCFET. Our investigation revealed that the optimal voltage at which the total power is minimized is not necessarily at the point of the minimum voltage required to fulfill the performance constraint (as in traditional DVS). Hence, an NCFET-aware DVS is key for high energy efficiency. In this work, we therefore propose the first NCFET-aware DVS technique that selects the optimal voltage to minimize the power following the dynamics of workloads. Our experimental results of a multi-core system demonstrate that NCFET-aware DVS results in 20% on average, and up to 27% energy saving while still fulfilling the same performance constraint (i.e., no trade-offs) compared to traditional NCFET-unaware DVS techniques.
Ising Deconfinement Transition Between Feshbach-Resonant Superfluids
Creators: name: Ejima, S.
name: Bhaseen, M. J.
name: Hohenadler, M.
name: Essler, F. H. L.
name: Fehske, H.
name: Simons, B. D.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: We investigate the phase diagram of bosons interacting via Feshbach-resonant pairing interactions in a one-dimensional lattice. Using large scale density matrix renormalization group (DMRG) and field theory techniques we explore the atomic and molecular correlations in this low-dimensional setting. We provide compelling evidence for an Ising deconfinement transition occurring between distinct superfluids and extract the Ising order parameter and correlation length of this unusual superfluid transition. This is supported by results for the entanglement entropy which reveal both the location of the transition and critical Ising degrees of freedom on the phase boundary.
description: 4 pages, 4 figures
Universal Sound Absorption in Amorphous Solids: A Theory of Elastically Coupled Generic Blocks
Creators: name: Vural, Dervis C.
name: Leggett, Anthony J.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Glasses are known to exhibit quantitative universalities at low temperatures, the most striking of which is the ultrasonic attenuation coefficient 1/Q. In this work we develop a theory of coupled generic blocks with a certain randomness property to show that universality emerges essentially due to the interactions between elastic blocks, regardless of their microscopic nature.
description: (Revised) 16 pages, 2 figures. To appear in Journal of Non-Crystalline Solids
Local origins of volume fraction fluctuations in dense granular materials
Creators: name: Puckett, James G.
name: Lechenault, Frederic
name: Daniels, Karen E.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Fluctuations of the local volume fraction within granular materials have previously been observed to decrease as the system approaches jamming. We experimentally examine the role of boundary conditions and inter-particle friction $μ$ on this relationship for a dense granular material of bidisperse particles driven under either constant volume or constant pressure. Using a radical Voronoï tessellation, we find the variance of the local volume fraction $ϕ$ monotonically decreases as the system becomes more dense, independent of boundary condition and $μ$. We examine the universality and origins of this trend using experiments and the recent granocentric model \cite{Clusel-2009-GMR,Corwin-2010-MRP}, modified to draw particle locations from an arbitrary distribution ${\cal P}(s)$ of neighbor distances $s$. The mean and variance of the observed ${\cal P}(s)$ are described by a single length scale controlled by $\bar ϕ$. Through the granocentric model, we observe that diverse functional forms of ${\cal P}(s)$ all produce the trend of decreasing fluctuations, but only the experimentally-observed ${\cal P}(s)$ provides quantitative agreement with the measured $ϕ$ fluctuations. Thus, we find that both ${\cal P}(s)$ and ${\cal P}(ϕ)$ encode similar information about the ensemble of observed packings, and are connected to each other by the local granocentric model.
Anatomy of a deformed symmetry: field quantization on curved momentum space
Creators: name: Arzano, Michele
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In certain scenarios of deformed relativistic symmetries relevant for non-commutative field theories particles exhibit a momentum space described by a non-abelian group manifold. Starting with a formulation of phase space for such particles which allows for a generalization to include group valued momenta we discuss quantization of the corresponding field theory. Focusing on the particular case of kappa-deformed phase space we construct the one-particle Hilbert space and show how curvature in momentum space leads to an ambiguity in the quantization procedure reminiscent of the ambiguities one finds when quantizing fields in curved space-times. The tools gathered in the discussion on quantization allow for a clear definition of the basic deformed field mode operators and two-point function for kappa-quantum fields.
description: RevTeX, 15 pages, no figures. v2 typos corrected and minor cosmetic modifications, v3 to appear on Phys. Rev. D
Sizable electromagnetic forces in parallel-plate metallic cavity
Creators: name: Wang, S. B.
name: Ng, Jack
name: Liu, H.
name: Zheng, H. H.
name: Hang, Z. H.
name: Chan, C. T.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Using a boundary element method to calculate the electromagnetic fields and the Maxwell stress tensor method to compute the electromagnetic forces, we investigate electromagnetic wave induced forces acting on a pair of identical metal plates that forms an electromagnetic resonance cavity. Different frequency regimes are considered, from infrared frequencies with micron scale structures down to the microwave regime which involves millimeter scale structures. We found that at both length scales, the electromagnetic wave induced forces can be significantly stronger than the usual photon pressure exerted by a laser beam if the cavity is excited at resonance although the mechanisms that underlie the strong force are different at different length scales. In the infrared frequency regime, the strong force is induced by field penetration into the metal, whereas in the microwave regime, the electromagnetic force is induced by the leakage of electric field at the edges. At both frequency scales, we compare the results we obtained for Au metal plates with fictitious perfect electric conductor plates so as to understand the effect of field penetration. We also showed that a transmission line model can give simple expressions that can capture the essence of the physics. The effect of surface corrugation and surface roughness is also investigated, and we find that corrugation/roughness generally induces attraction between the plates.
description: 32 pages, 9 figures
Sustainability meets eco-spirituality : using a qualitative multi-methods approach to explore the Philippine Catholic Church’s potential for watershed governance partnership in the Angat River Basin, Bulacan, Philippines
Creators: name: O'Callaghan, Katherine
Publisher: name: University of British Columbia
Year: 2017

description: The literature of Integrated Water Resource Management argues collaborative watershed partnerships between state agencies and civil society are crucial for water governance. They bring stakeholders together to facilitate dialogue, reduce competition and negotiate on complex water related issues. However in newly independent states, like the Philippines, local state agencies are still struggling to adopt collaborative governance approaches that offer stronger stakeholder engagement, due to poorly implemented decentralizing policies, resource constraints and a lack of political will. Thus, the need to identify and explore alternative institutional arrangements that are capable and willing to support local government is the first step towards developing culturally appropriate and feasible solutions within the Philippine context. Using the Angat River Basin, located in Bulacan, Central Luzon, Philippines, as the focal area for investigation, this research presents a shift in thinking about mainstream watershed group-agency partnerships. As such, the research suggests that the Philippine Catholic Church, a key faith-based organization possesses the necessary skills, experience and trust to facilitate and support a potential partnership for the 63,000 hectare Angat River Basin. The findings from this research, which were collected using a qualitative multi-method approach, highlight how the Diocese of Malolos and the wider Philippine Catholic Church are not only actively responding to environmental advocacy and management, but that their strengths of transformational leadership, political acuity and moral authority compensate for the deficiencies of the local government.
E6 grand unified theory with three generations from heterotic string
Creators: name: Ito, Motoharu
name: Kuwakino, Shogo
name: Maekawa, Nobuhiro
name: Moriyama, Sanefumi
name: Takahashi, Keijiro
name: Takei, Kazuaki
name: Teraguchi, Shunsuke
name: Yamashita, Toshifumi
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We construct two more supersymmetric E6 grand unified models with three generations within the framework of Z12 asymmetric orbifold compactification of the heterotic string theory. Such an asymmetric orbifold is missing in the classification in the literature, which concludes that only one E6 model is possible. In both of the new models, an adjoint Higgs field is obtained in virtue of the diagonal embedding method. This method mods out the three E6 factors of an even self-dual momentum-lattice by a permutation symmetry. In order to realize the E6^3 even self-dual lattice, we utilize the lattice engineering technique. Among the eight possible orbifold actions in our setup, two lead to new E6 models. Though these models still share the unsatisfactory issues with the known one, our discovery raises hopes that excellent models that solve all the problems in the supersymmetric grand unified models will be found in this framework.
description: 5 pages, no figures, minor improvements and references added
Extreme Cosmic-Ray-Dominated-Regions: a new paradigm for high star formation density events in the Universe
Creators: name: Papadopoulos, Padeli P.
name: Thi, Wing-Fai
name: Miniati, Francesco
name: Viti, Serena
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We examine in detail the recent proposal that extreme Cosmic-Ray-Dominated-Regions (CRDRs) characterize the ISM of galaxies during events of high-density star formation, fundamentally altering its initial conditions (Papadopoulos 2010). Solving the coupled chemical and thermal state equations for dense UV-shielded gas reveals that the large cosmic ray energy densities in such systems (U_{CR} (few)x(10^3-10^4) U_{CR,Gal}) will indeed raise the minimum temperature of this phase (where the initial conditions of star formation are set) from ~10K (as in the Milky Way) to (50-100)K. Moreover in such extreme CRDRs the gas temperature remains fully decoupled from that of the dust, with T_{kin} >> T_{dust}, even at high densities (n(H_2)~10^5--10^6 cm^{-3}), quite unlike CRDRs in the Milky Way where T_k T_{dust} when n(H_2) >= 10^5 cm^{-3}. These dramatically different star formation initial conditions will: a) boost the Jeans mass of UV-shielded gas regions by factors of ~10--100 with respect to those in quiescent or less extreme star forming systems, and b) "erase" the so-called inflection point of the effective equation of state (EOS) of molecular gas. Both these effects occur across the entire density range of typical molecular clouds, and may represent {\it a new paradigm for all high-density star formation in the Universe}, with cosmic rays as the key driving mechanism, operating efficiently even in the high dust extinction environments of extreme starbursts...
description: 10 pages, 5 figures, accepted with minor modifications for publication in the MNRAS (the follow-up paper to Papadopoulos 2010, ApJ, 720, 226)