cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Experimental studies on vacancy induced ferromagnetism in undoped TiO2
Creators: name: Rumaiz, Abdul K
name: Ali, Bakhtyar
name: Ceylan, Abdullah
name: Boggs, M.
name: Beebe, T.
name: Shah, S. Ismat
Publisher: name: arXiv
Year: 2007
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Room temperature ferromagnetism is observed in undoped TiO2 films deposited on Si substrates using pulsed laser deposition (PLD). The ferromagnetic properties of the samples depend on the oxygen partial pressure during the PLD synthesis. The appearance of higher binding energy component (HBEC) in the oxygen 1s core peak from x-ray photoelectron spectroscopy (XPS) suggests the presence of oxygen vacancies in these samples. The amount of oxygen during the synthesis determines the vacancy concentration in the samples which is directly related to the magnetic behavior of the samples. The magnetic moment decreases with oxygen vacancy concentration in the samples. Valence band measurements were performed to study the electronic structure of both stoichometric and reduced TiO2. The analyses show the presence of Ti 3d band near the Fermi level in reduced TiO2 samples. These bands are otherwise empty in stoichiometric TiO2 and reside in the conduction band which makes them unobservable by XPS. The existence of this Ti 3d band near the Fermi level can possibly lead to Stoner splitting of the band.
description: 20 pages, 9 figure
Functional analytic methods for discrete approximations of subwavelength resonator systems
Creators: name: Ammari, Habib
name: Davies, Bryn
name: Hiltunen, Erik Orvehed
Publisher: name: arXiv
Year: 2021
Subjects: subject: Analysis of PDEs (math.AP)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 35J05, 35C20, 35P20, 74J20

description: We survey functional analytic methods for studying subwavelength resonator systems. In particular, rigorous discrete approximations of Helmholtz scattering problems are derived in an asymptotic subwavelength regime. This is achieved by re-framing the Helmholtz equation as a non-linear eigenvalue problem in terms of integral operators. In the subwavelength limit, resonant states are described by the eigenstates of the generalised capacitance matrix, which appears by perturbing the elements of the kernel of the limiting operator. Using this formulation, we are able to describe subwavelength resonance and related phenomena. In particular, we demonstrate large-scale effective parameters with exotic values. We also show that these systems can exhibit localised and guided waves on very small length scales. Using the concept of topologically protected edge modes, such localisation can be made robust against structural imperfections.
Experience and design : refined experience of natural context and the architectural design process
Creators: name: Hager, MaryAnn
Publisher: name: University of British Columbia
Year: 2010

description: This inquiry explores the experience of natural context, and the implications of refined awareness for the architectural design process. Firstly, it consists of the Theoria; a description of experience as generic. Secondly, it consists of the Praxis; my own experiential descriptions of natural context with concomitant design explorations. Thirdly, it consists of the Thesis; a description of design experience as generated by the refined experience of natural context. The Thesis describes the following intrinsic traits of design experience: a poignant design trigger (punctum); the inextricable co-presence of actual with potential experience; the subtle rhythm of focus with emanation; and spontaneous continuity. These traits are distinctive to a design process tempered by refined experience. This inquiry is written by a designer for the designer. The research method is direct experience, both of the natural context and of the design process. The discourse is first person descriptive. The inquiry adopts the premise that direct experience and personal discourse are valid bases for communication on an essential level. The intention is to speak to the designer through vicarious experience rather than through the acceptance of a hypothetical argument. This inquiry focusses on the early stages of design experience. In terms of the traditional design process, I have focussed on the pre-design stage, design inception and early sketch development. Further stages of the process, including the act of building, remain for further study.
Description of double beta decay within continuum-QRPA
Creators: name: Rodin, Vadim
name: Faessler, Amand
Publisher: name: arXiv
Year: 2007
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: A method to calculate the nuclear double beta decay ($2νββ$- and $0νββ$-) amplitudes within the continuum random phase approximation (cQRPA) is formulated. Calculations of the $ββ$ transition amplitudes within the cQRPA are performed for ^{76}Ge, ^{100}Mo and ^{130}Te. A rather simple nuclear Hamiltonian consisting of phenomenological mean field and zero-range residual particle-hole and particle-particle interaction is used. The calculated M^{2ν} are almost not affected when the single-particle continuum is taken into account. At the same time, a regular suppression of the $0νββ$-amplitude is found that can be associated with additional ground state correlations due to collective states in the continuum. It is expected that future inclusion of the nucleon pairing in the single-particle continuum will somewhat compensate the suppression.
description: 20 pages, 1 figure, published version
Parity symmetry as the origin of 'spin' in the quantum spin Hall effect
Creators: name: Beugeling, Wouter
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The quantum spin Hall effect arises due to band inversion in topological insulators, and has the defining characteristic that it hosts helical edge channels at zero magnetic field, leading to a finite spin Hall conductivity. The spin Hall conductivity is understood as the difference of the contributions of two spin states. In the effective four-band BHZ model, these two spin states appear as two uncoupled blocks in the Hamiltonian matrix. However, this idea breaks down if additional degrees of freedom are considered. The two blocks cannot be identified by proper spin $S_z$ or total angular momentum $J_z$, both not conserved quantum numbers. In this work, we discuss a notion of block structure for the more general k.p model, defined by a conserved quantum number that we call isoparity, a combination of parity $z\to-z$ and spin. Isoparity remains a conserved quantity under a wide range of conditions, in particular in presence of a perpendicular external magnetic field. From point-group considerations, isoparity is fundamentally defined as the action of $z\to-z$ on the spatial and spinorial degrees of freedom. Since time reversal anticommutes with isoparity, the two blocks act as Kramers partners. The combination of conductivity and isoparity defines spin conductivity. This generalized notion of spin Hall conductivity uncovers the meaning of 'spin': It is not the proper spin $S_z$, but a crystal symmetry that is realized by a spinorial representation.
description: 12 pages, 4 figures; Secs. IV-VI shortened, title changed
Universal properties of multimodal human mobility: a statistical physics point of view
Creators: name: Mizzi, Chiara
name: Fabbri, Alessandro
name: Colombini, Giulio
name: Bertini, Flavio
name: Bazzani, Armando
Publisher: name: arXiv
Year: 2021
Subjects: subject: Physics and Society (physics.soc-ph)
subject: FOS: Physical sciences

description: The statistical properties of human mobility have been studied in the framework of complex systems physics. Taking advantage from the new datasets made available by the information and communication technologies, the distributions of mobility path lengths and of trip duration have been considered to discover the fingerprints of complexity characters, but the role of the different transportation means on the statistical properties of urban mobility has not been studied in deep. In this paper we cope with the problem of pointing out the existence of universal features for different type of individual mobility: pedestrian, cycling and vehicular urban mobility. In particular, we propose the use of travel time as universal 'energy' for the mobility and we define a simple survival model that explains the travel time distribution of the different types of mobility. the analysis is performed in the metropolitan area of Bologna (Italy), where GPS datasets were available on individual trips using different transport means. Our results could suggest how to plan the different transportation networks to realize a multimodal mobility compatibly with the citizens propensities to use the different transport means.
Contrastive Out-of-Distribution Detection for Pretrained Transformers
Creators: name: Zhou, Wenxuan
name: Liu, Fangyu
name: Chen, Muhao
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computation and Language (cs.CL)
subject: FOS: Computer and information sciences

description: Pretrained Transformers achieve remarkable performance when training and test data are from the same distribution. However, in real-world scenarios, the model often faces out-of-distribution (OOD) instances that can cause severe semantic shift problems at inference time. Therefore, in practice, a reliable model should identify such instances, and then either reject them during inference or pass them over to models that handle another distribution. In this paper, we develop an unsupervised OOD detection method, in which only the in-distribution (ID) data are used in training. We propose to fine-tune the Transformers with a contrastive loss, which improves the compactness of representations, such that OOD instances can be better differentiated from ID ones. These OOD instances can then be accurately detected using the Mahalanobis distance in the model's penultimate layer. We experiment with comprehensive settings and achieve near-perfect OOD detection performance, outperforming baselines drastically. We further investigate the rationales behind the improvement, finding that more compact representations through margin-based contrastive learning bring the improvement. We release our code to the community for future research.
description: Accepted at EMNLP 2021. Code available at https://github.com/wzhouad/Contra-OOD
Heavy Magnetic Neutron Stars
Creators: name: Rather, I. A.
name: Rahaman, Usuf
name: Dexheimer, V.
name: Usmani, A. A.
name: Patra, S. K.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We systematically study the properties of pure nucleonic and hyperonic magnetic stars using a density-dependent relativistic mean field (DD-RMF) equations of state. We explore several parameter sets and hyperon coupling schemes within the DD-RMF formalism. We focus on sets that are in better agreement with nuclear and other astrophysical data, while generating heavy neutron stars. Magnetic field effects are included in the matter equation of state and in general relativity solutions, which in addition fulfill Maxwell's equations. We find that pure nucleonic matter, even without magnetic field effects, generates neutron stars that satisfy the potential GW190814 mass constraint; however, this is not the case for hyperonic matter, which instead only satisfies the more conservative 2.1 M$_{\odot}$ constraint. In the presence of strong but still somehow realistic internal magnetic fields $\approx10^{17}$ G, the stellar charged particle population re-leptonizes and de-hyperonizes. As a consequence, magnetic fields stiffen hyperonic equations of state and generate more massive neutron stars, which can satisfy the possible GW190814 mass constraint but present a large deformation with respect to spherical symmetry.
description: 13 pages, 15 figures, 6 tables: Accepted for Publication in ApJ
Bragg spectroscopy of a superfluid Bose-Hubbard gas
Creators: name: Du, X.
name: Wan, Shoupu
name: Yesilada, Emek
name: Ryu, C.
name: Heinzen, D. J.
name: Liang, Z. X.
name: Wu, Biao
Publisher: name: arXiv
Year: 2007
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: Bragg spectroscopy is used to measure excitations of a trapped, quantum-degenerate gas of 87Rb atoms in a 3-dimensional optical lattice. The measurements are carried out over a range of optical lattice depths in the superfluid phase of the Bose-Hubbard model. For fixed wavevector, the resonant frequency of the excitation is found to decrease with increasing lattice depth. A numerical calculation of the resonant frequencies based on Bogoliubov theory shows a less steep rate of decrease than the measurements.
description: 11 pages, 4 figures
Decaying Dark Matter: Simulations and Weak-Lensing Forecast
Creators: name: Hubert, Jonathan
name: Schneider, Aurel
name: Potter, Doug
name: Stadel, Joachim
name: Giri, Sambit K.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Despite evidence for the existence of dark matter (DM) from very high and low redshifts, a moderate amount of DM particle decay remains a valid possibility. This includes both models with very long-lived yet unstable particles or mixed scenarios where only a small fraction of dark matter is allowed to decay. In this paper, we investigate how DM particles decaying into radiation affect non-linear structure formation. We look at the power spectrum and its redshift evolution, varying both the decay lifetime ($τ$) and the fraction of decaying-to-total dark matter ($f$), and we propose a fitting function that reaches sub-percent precision below $k\sim10$ h/Mpc. Based on this fit, we perform a forecast analysis for a Euclid-like weak lensing (WL) survey, including both massive neutrino and baryonic feedback parameters. We find that with WL observations alone, it is possible to rule out decay lifetimes smaller than $τ=75$ Gyr (at 95 percent CL) for the case that all DM is unstable. This constraint improves to $τ=182$ Gyr if the WL data is combined with CMB priors from the Planck satellite and to $τ=275$ Gyr if we further assume baryonic feedback to be fully constrained by upcoming Sunyaev-Zeldovich or X-ray data. The latter shows a factor of 3.2 improvement compared to constraints from CMB data alone. Regarding the scenario of a strongly decaying sub-component of dark matter with $τ\sim 30$ Gyr or lower, it will be possible to rule out a decaying-to-total fraction of $f>0.49$, $f>0.21$, and $f>0.13$ (at the 95 percent CL) for the same three scenarios. We conclude that the upcoming stage-IV WL surveys will allow us to significantly improve current constraints on the stability of the dark matter sector.
description: matching accepted version
Sheaves of non-commutative smooth and holomorphic functions associated with the non-abelian two-dimensional Lie algebra
Creators: name: Aristov, Oleg
Publisher: name: arXiv
Year: 2021
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics

description: Dosi and, quite recently, the author showed that, on the character space of a nilpotent Lie algebra, there exists a sheaf of Fréchet--Arens--Michael algebras (of noncommutative holomorphic functions in the complex case and of noncommutative smooth functions in the real case). We construct similar sheaves (both versions, holomorphic and smooth) on a special space of representations for the Lie algebra of the group of affine transformations of the real line (which is the simplest nonnilpotent solvable Lie algebra).
description: version 5: English translation (by Math. Notes), version 4 and earlier in Russian, version 3: correction in Th.1.2, version 2: correction in Th.2.1
Categorical models of unstable G-global homotopy theory
Creators: name: Lenz, Tobias
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Topology (math.AT)
subject: FOS: Mathematics
subject: 55P91 (Primary), 18G55 (Secondary)

description: We prove that the category $\textbf{G-Cat}$ of small categories with $G$-action forms a model of unstable $G$-global homotopy theory for every discrete group $G$, generalizing Schwede's global model structure on $\textbf{Cat}$. As a consequence, we prove that $\textbf{G-Cat}$ models proper $G$-equivariant homotopy theory not only when we test weak equivalences on fixed points, but also when we test them on categorical homotopy fixed points.
description: Final version, incorporating suggestions by referee (several changes to exposition). 42 pages
Charge Order Superstructure with Integer Iron Valence in Fe2OBO3
Creators: name: Angst, M.
name: Khalifah, P.
name: Hermann, R. P.
name: Xiang, H. J.
name: Whangbo, M. -H.
name: Varadarajan, V.
name: Brill, J. W.
name: Sales, B. C.
name: Mandrus, D.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Solution-grown single crystals of Fe2OBO3 were characterized by specific heat, Mossbauer spectroscopy, and x-ray diffraction. A peak in the specific heat at 340 K indicates the onset of charge order. Evidence for a doubling of the unit cell at low temperature is presented. Combining structural refinement of diffraction data and Mossbauer spectra, domains with diagonal charge order are established. Bond-valence-sum analysis indicates integer valence states of the Fe ions in the charge ordered phase, suggesting Fe2OBO3 is the clearest example of ionic charge order so far.
description: 4 pages, 5 figures. Fig. 3 is available in higher resolution from the authors. PRL in print
Machine-Learned Dark Matter Subhalo Candidates in the 4FGL-DR2: Search for the Perturber of the GD-1 Stream
Creators: name: Mirabal, Nestor
name: Bonaca, Ana
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The detection of dark matter subhalos without a stellar component in the Galactic halo remains a challenge. We use supervised machine learning to identify high-latitude gamma-ray sources with dark matter-like spectra among unassociated gamma-ray sources in the 4FGL-DR2. Out of 843 4FGL-DR2 unassociated sources at $|b| \geq 10\mathrm{^\circ}$, we select 73 dark matter subhalo candidates. Of the 69 covered by the Neil Gehrels Swift Observatory (Swift), 17 show at least one X-ray source within the 95% LAT error ellipse and 52 where we identify no new sources. This latest inventory of dark subhalos candidates allows us to investigate the possible dark matter substructure responsible for the perturbation in the GD-1 stellar stream. In particular, we examine the possibility that the alleged GD-1 dark subhalo may appear as a 4FGL-DR2 gamma-ray source from dark matter annihilation into Standard Model particles.
description: 17 pages, 4 figures, 2 tables, resubmitted to JCAP, comments welcome!
Understanding Cycling Mobility: Bologna Case Study
Creators: name: Davtian, Taron
name: Bertini, Flavio
name: Sharma, Rajesh
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computers and Society (cs.CY)
subject: Social and Information Networks (cs.SI)
subject: FOS: Computer and information sciences

description: Understanding human mobility in urban environments is of the utmost importance to manage traffic and for deploying new resources and services. In recent years, the problem is exacerbated due to rapid urbanization and climate changes. In an urban context, human mobility has many facets, and cycling represents one of the most eco-friendly and efficient/effective ways to move in touristic and historical cities. The main objective of this work is to study the cycling mobility within the city of Bologna, Italy. We used six months dataset that consists of 320,118 self-reported bike trips. In particular, we performed several descriptive analysis to understand spatial and temporal patterns of bike users for understanding popular roads, and most favorite points within the city. This analysis involved several other public datasets in order to explore variables that can possibly affect the cycling activity, such as weather, pollution, and events. The main results of this study indicate that bike usage is more correlated to temperature, and precipitation and has no correlation to wind speed and pollution. In addition, we also exploited various machine learning and deep learning approaches for predicting short-term trips in the near future (that is for the following 30, and 60 minutes), that could help local governmental agencies for urban planning. Our best model achieved an R square of 0.91, a Mean Absolute Error of 5.38 and a Root Mean Squared Error of 8.12 for the 30-minutes time interval.
Comparison of Dissipative Particle Dynamics and Langevin thermostats for out-of-equilibrium simulations of polymeric systems
Creators: name: Pastorino, C.
name: Kreer, T.
name: Mueller, M.
name: Binder, K.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: In this work we compare and characterize the behavior of Langevin and Dissipative Particle Dynamics (DPD) thermostats in a broad range of non-equilibrium simulations of polymeric systems. Polymer brushes in relative sliding motion, polymeric liquids in Poiseuille and Couette flows, and brush-melt interfaces are used as model systems to analyze the efficiency and limitations of different Langevin and DPD thermostat implementations. Widely used coarse-grained bead-spring models under good and poor solvent conditions are employed to assess the effects of the thermostats. We considered equilibrium, transient, and steady state examples for testing the ability of the thermostats to maintain constant temperature and to reproduce the underlying physical phenomena in non-equilibrium situations. The common practice of switching-off the Langevin thermostat in the flow direction is also critically revisited. The efficiency of different weight functions for the DPD thermostat is quantitatively analyzed as a function of the solvent quality and the non-equilibrium situation.
description: 12 pages, introduction improved, references added, to appear in Phys. Rev. E
Muon $g-2$ in a two-Higgs-doublet model with a type-II seesaw mechanism
Creators: name: Chen, Chuan-Hung
name: Chiang, Cheng-Wei
name: Nomura, Takaaki
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We study the two-Higgs-doublet model with type-II seesaw mechanism. In view of constraints from the Higgs data, we consider the aligned two-Higgs-doublet scheme and its effects on muon anomalous magnetic dipole moment, $a_μ$, including both one-loop and two-loop Barr-Zee type diagrams. Thanks to a sizable trilinear scalar coupling, the Barr-Zee type diagrams mediated by the Higgs triplet fields have a dominant effect on $a_μ$. In particular, unlike the usual two-Higgs-doublet models that require exotic Higgs bosons light in mass, the masses of the corresponding particles in the model are of ${\cal O}(100)$~GeV. The doubly-charged Higgs boson presents a different decay pattern from the usual Higgs triplet model and thus calls for a new collider search strategy, such as multi-$τ$ searches at the LHC.
description: 36 pages, 10 figures, version accepted for publication in PRD
Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains
Creators: name: Cuppen, H. M.
name: Herbst, Eric
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Although still poorly understood, the chemistry that occurs on the surfaces of interstellar dust particles profoundly affects the growth of molecules in the interstellar medium. An important set of surface reactions produces icy mantles of many monolayers in cold and dense regions. The monolayers are dominated by water ice, but also contain CO, CO_{2}, and occasionally methanol as well as minor constituents. In this paper, the rate of production of water-ice dominated mantles is calculated for different physical conditions of interstellar clouds and for the first time images of the morphology of interstellar ices are presented. For this purpose, the continuous-time random-walk Monte Carlo simulation technique has been used. The visual extinction, density, and gas and grain temperatures are varied. It is shown that our stochastic approach can reproduce the important observation that ice mantles only grow in the denser regions.
description: 40 pages, 11 figures, 7 tables, to be published in ApJ
Harmonic sections in sphere bundles, normal neighborhoods of reduction loci, and instanton moduli spaces on definite 4-manifolds
Creators: name: Teleman, Andrei
Publisher: name: arXiv
Year: 2007
Subjects: subject: Geometric Topology (math.GT)
subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 57R57; 53C43

description: We prove an existence theorem for gauge invariant $L^2$-normal neighborhoods of the reduction loci in the space ${\cal A}_a(E)$ of oriented connections on a fixed Hermitian 2-bundle $E$. We use this to obtain results on the topology of the moduli space ${\cal B}_a(E)$ of (non-necessarily irreducible) oriented connections, and to study the Donaldson $μ$-classes globally around the reduction loci. In this part of the article we use essentially the concept of harmonic section in a sphere bundle with respect to an Euclidean connection. Second, we concentrate on moduli spaces of instantons on definite 4-manifolds with arbitrary first Betti number. We prove strong generic regularity results which imply (for bundles with "odd" first Chern class) the existence of a connected, dense open set of "good" metrics for which all the reductions in the Uhlenbeck compactification of the moduli space are simultaneously regular. These results can be used to define new Donaldson type invariants for definite 4-manifolds. The idea behind this construction is to notice that, for a good metric $g$, the geometry of the instanton moduli spaces around the reduction loci is always the same, independently of the choice of $g$. The connectedness of the space of good metrics is important, in order to prove that no wall-crossing phenomena (jumps of invariants) occur. Moreover, we notice that, for low instanton numbers, the corresponding moduli spaces are a priori compact and contain no reductions at all so, in these cases, the existence of well-defined Donaldson type invariants is obvious. The natural question is to decide whether these new Donaldson type invariants yield essentially new differential topological information on the base manifold have, or have a purely topological nature.
description: LaTeX, 45 pages
On the renormalization of the bosonized multi-flavor Schwinger model
Creators: name: Nandori, I.
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The phase structure of the bosonized multi-flavor Schwinger model is investigated by means of the differential renormalization group (RG) method. In the limit of small fermion mass the linearized RG flow is sufficient to determine the low-energy behavior of the N-flavor model, if it has been rotated by a suitable rotation in the internal space. For large fermion mass, the exact RG flow has been solved numerically. The low-energy behavior of the multi-flavor model is rather different depending on whether N=1 or N>1, where N is the number of flavors. For N>1 the reflection symmetry always suffers breakdown in both the weak and strong coupling regimes, in contrary to the N=1 case, where it remains unbroken in the strong coupling phase.
description: 13 pages, 2 figures, final version, published in Physics Letters B
Transport measurements across a tunable potential barrier in graphene
Creators: name: Huard, B.
name: Sulpizio, J. A.
name: Stander, N.
name: Todd, K.
name: Yang, B.
name: Goldhaber-Gordon, D.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The peculiar nature of electron scattering in graphene is among many exciting theoretical predictions for the physical properties of this material. To investigate electron scattering properties in a graphene plane, we have created a gate-tunable potential barrier within a single-layer graphene sheet. We report measurements of electrical transport across this structure as the tunable barrier potential is swept through a range of heights. When the barrier is sufficiently strong to form a bipolar junctions (npn or pnp) within the graphene sheet, the resistance across the barrier sharply increases. We compare these results to predictions for both diffusive and ballistic transport, as the barrier rises on a length scale comparable to the mean free path. Finally, we show how a magnetic field modifies transport across the barrier.
description: 5 pages, 5 figures
The primordial binary population II: Recovering the binary population for intermediate mass stars in Sco OB2
Creators: name: Kouwenhoven, M. B. N.
name: Brown, A. G. A.
name: Zwart, S. F. Portegies
name: Kaper, L.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We characterize the binary population in the young and nearby OB association Scorpius OB2 using available observations of visual, spectroscopic, and astrometric binaries with intermediate-mass primaries. We take into account observational biases by comparing the observations with simulated observations of model associations. The available data indicate a large binary fraction (> 70% with 3sigma confidence), with a large probability that all intermediate mass stars in Sco OB2 are part of a binary system. The binary systems have a mass ratio distribution of the form f(q) ~ q^-0.4. Sco OB2 has a semi-major axis distribution of the form f(log a) ~ constant (Opik's law), in the range 5-5e6 Rsun. The log-normal period distribution of Duquennoy & Mayor results in too few spectroscopic binaries, even if the model binary fraction is 100%. Sco OB2 is a young association with a low stellar density; its current population is expected to be very similar to the primordial population. The fact that practically all stars in Sco OB2 are part of a binary (or multiple) system demonstrates that multiplicity is a fundamental factor in the star formation process, at least for intermediate mass stars.
description: 36 pages, 11 figures, accepted by A&A
Submillimeter constraints for non-Newtonian gravity from spectroscopy
Creators: name: Lemos, A. S.
Publisher: name: arXiv
Year: 2021
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In this work, we consider the Yukawa-type and power-type non-Newtonian corrections, which induce amplification of gravitational interaction on submillimeter scales, and analytically calculate deviations produced by the atomic gravitational field on the energy levels of hydrogen-like ions. Analyzing ionic transitions between Rydberg states, we derive prospective constraints for non-Newtonian corrections. It is shown that the results also provide stronger constraints, due to the high accuracy for Rydberg transition measures into optical spectrum frequency range, than the current empirical bounds following from Casimir force measurements.
description: 14 pages, 3 figures, version published in EPL
Atom-wave diffraction between the Raman-Nath and the Bragg regime: Effective Rabi frequency, losses, and phase shifts
Creators: name: Mueller, Holger
name: Chiow, Sheng-wey
name: Chu, Steven
Publisher: name: arXiv
Year: 2007
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We present an analytic theory of the diffraction of (matter) waves by a lattice in the "quasi-Bragg" regime, by which we mean the transition region between the long-interaction Bragg and "channelling" regimes and the short-interaction Raman-Nath regime. The Schroedinger equation is solved by adiabatic expansion, using the conventional adiabatic approximation as a starting point, and re-inserting the result into the Schroedinger equation to yield a second order correction. Closed expressions for arbitrary pulse shapes and diffraction orders are obtained and the losses of the population to output states otherwise forbidden by the Bragg condition are derived. We consider the phase shift due to couplings of the desired output to these states that depends on the interaction strength and duration and show how these can be kept negligible by a choice of smooth (e.g., Gaussian) envelope functions even in situations that substantially violate the adiabaticity condition. We also give an efficient method for calculating the effective Rabi frequency (which is related to the eigenvalues of Mathieu functions) in the quasi-Bragg regime.
description: Minor additions, more concise text. To appear in Phys. Rev. A. 20 pages, 10 figures
Final Report. The International Decision Support Initiative’s experience of institutionalising evidence informed priority setting: a synthesis of four country learning reviews
Creators: name: Lloyd, Rob
name: Gleed, Greg
name: Wallach, Stefanie
name: Groom, Genevieve
name: Husain, Lewis
Publisher: name: F1000 Research Limited
Year: 2019

description: Between May and October 2018, Itad conducted Learning  Reviews of the International Decision Support Initiative’s (iDSI’s) work in China, Ghana, Indonesia and South Africa.
The purpose was to review the scope of iDSI’s  engagement at country level between 2016 and 2018 and investigate how i DSI is contributing to the institutionalisation of evidence - informed priority setting (EIPS), explore what has been working effectively and where there might be scope for course correction or refinements to iDSI’s future strategy. This report provides a synthesis of the findings from the four country Learning Reviews, distils overall lessons and provides strategic recommendations to iDSI moving forward.
PI -- Multimodal Planetary Defense
Creators: name: Lubin, Philip
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Physics and Society (physics.soc-ph)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: We present a practical and effective method of planetary defense that allows for extremely short mitigation time scales if required as well as long time scale mitigation. This one system allows for virtually any required defense mode. In general, it uses much less launch mass with vastly short required response time than classical deflection techniques The method uses an array of small hypervelocity kinetic penetrators that pulverize and disassemble an asteroid or small comet. This approach will work in extended time scale modes where there is a large warning time, as well as in short interdiction time scenarios with intercepts of minutes to days before impact. In longer time intercept scenarios, the disassembled asteroid fragments largely miss the Earth. In short intercept scenarios, the asteroid fragments of maximum $\sim$10-meter diameter allow the Earth's atmosphere to act as a "beam dump" where the fragments burn up and/or air burst, with the primary channel of energy going into spatially and temporally de-correlated shock waves. The de-correlated blast waves are the key to why PI works so well. The effectiveness of the approach depends on the intercept time and size of the asteroid but allows for effective defense against asteroids in the 20-1000m diameter class and could virtually eliminate the threat of mass destruction posed by these threats with very short warning times, though longer warning is always preferred. A 20m diameter asteroid ($\sim$0.5Mt, similar to Chelyabinsk) can be mitigated with a 100s prior to impact intercept with a 10m/s disruption. With ~1m/s internal disruption, a 5 hours prior to impact intercept of a 50m diameter asteroid ($\sim$10Mt yield, similar to Tunguska), a 1 day prior to impact intercept of 100m diameter asteroid ($\sim$100Mt yield), a 20 day prior to impact intercept of Apophis ($\sim$370m diameter, $\sim$4Gt yield) mitigates these threats.
description: 194 pages, 148 figures. Published in Advances in Space Research (ASR) 10-22; https://www.sciencedirect.com/science/article/pii/S0273117722009395
Shuffle algebras for quivers as quantum groups
Creators: name: Neguţ, Andrei
name: Sala, Francesco
name: Schiffmann, Olivier
Publisher: name: arXiv
Year: 2021
Subjects: subject: Representation Theory (math.RT)
subject: Algebraic Geometry (math.AG)
subject: Quantum Algebra (math.QA)
subject: FOS: Mathematics

description: We define a quantum loop group $\mathbf{U}^+_Q$ associated to an arbitrary quiver $Q=(I,E)$ and maximal set of deformation parameters, with generators indexed by $I \times \mathbb{Z}$ and some explicit quadratic and cubic relations. We prove that $\mathbf{U}^+_Q$ is isomorphic to the (generic, small) shuffle algebra associated to the quiver $Q$ and hence, by [Neg21a], to the localized K-theoretic Hall algebra of $Q$. For the quiver with one vertex and $g$ loops, this yields a presentation of the spherical Hall algebra of a (generic) smooth projective curve of genus $g$ (invoking the results of [SV12]). We extend the above results to the case of non-generic parameters satisfying a certain natural metric condition. As an application, we obtain a description by generators and relations of the subalgebra generated by absolutely cuspidal eigenforms of the Hall algebra of an arbitrary smooth projective curve (invoking the results of [KSV17]).
description: v4: Published version, v3: Added Section 5 (concerning special values of the parameters) and Section 7 (on the Hall algebra of an arbitrary curve)
Magnetohydrodynamic properties of incompressible Meissner fluids
Creators: name: Maeyens, A.
name: Tempere, J.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We consider a superconducting material that exists in the liquid state, more precisely, in which the Meissner-Ochsenfeld effect persists in the liquid state. First, we investigate how the shape of such a hypothetical Meissner liquid will adapt to accomodate for an applied external field. In particular, we analyse the case of a droplet of Meissner fluid, and compute the elongation of the droplet and its quadrupole frequency as a function of the applied field. Next, the influence of an applied field on the flow of the liquid is studied for the case of a surface wave. We derive the dispersion relation for surface waves on an incompressible Meissner fluid. We discuss some candidate realizations of the Meissner fluids and for the case of a superconducting colloid discuss which regime of wave lengths would be most affected by the Meissner effect.
description: 12 pages, 3 figures
A philosophical design approach for an alternative concept for the urban parking garage
Creators: name: Chow, Leung Yen
Publisher: name: University of British Columbia
Year: 2010

description: This thesis proposes an expanded conceptualization of traditional parking garages. It is of contemporary design practice to separate the activity of parking from that of adjacent buildings and places. Doing so results in parking structures being exclusive and without positive urban context. As a consequence, barren and often, hostile environs are created within these garages. The thesis identifies this practice as a contributor to a discontinuity of urban movement and activity. The thesis also identifies the contradictory nature and ineffectiveness of facade decoration. Through four propositions developed from a philosophical design approach, which draws primarily from the work of Heidegger, the thesis proposes to engage human awareness so as to supplement the utilitarian nature of the traditional garage concept. It is suggested that doing so allows a positive environmental consciousness, and that active user participation can be elicited. It is also suggested that these propositions can potentially promote an integrity of construction and detailing, and that by overcoming the barren and hostile environs, a sense of civility and security can elevate the garage to a state of integrated function. Integrating the function of garages with those of other buildings can lead to a holistic use of site by facilitating urban continuity and, an architecture for garages richer in meaning than facade decoration.
Average $p_t$ as a probe of high energy QCD dynamics
Creators: name: Jalilian-Marian, Jamal
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Experiment (nucl-ex)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Average transverse momentum of hadrons produced in high energy collisions is proposed as a diagnostic probe of high density (saturation) physics. We show that by introducing and varying a transverse momentum cutoff in the definition of the average transverse momentum, one can eliminate the uncertainty in the overall magnitude of the leading order hadron production cross section in high energy collisions, and semi-quantitatively map the different dynamical regions predicted by the saturation physics. We discuss the applications of this method to pion production at RHIC and LHC and make quantitative predictions for the average transverse momentum of produced pions in the kinematics appropriate for the RHIC and LHC experiments.
description: 8 pages, 3 figures
Theory of gravitation theories: a no-progress report
Creators: name: Sotiriou, Thomas P
name: Faraoni, Valerio
name: Liberati, Stefano
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Astrophysics (astro-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Already in the 1970s there where attempts to present a set of ground rules, sometimes referred to as a theory of gravitation theories, which theories of gravity should satisfy in order to be considered viable in principle and, therefore, interesting enough to deserve further investigation. From this perspective, an alternative title of the present paper could be ``why are we still unable to write a guide on how to propose viable alternatives to general relativity?''. Attempting to answer this question, it is argued here that earlier efforts to turn qualitative statements, such as the Einstein Equivalence Principle, into quantitative ones, such as the metric postulates, stand on rather shaky grounds -- probably contrary to popular belief -- as they appear to depend strongly on particular representations of the theory. This includes ambiguities in the identification of matter and gravitational fields, dependence of frequently used definitions, such as those of the stress-energy tensor or classical vacuum, on the choice of variables, etc. Various examples are discussed and possible approaches to this problem are pointed out. In the course of this study, several common misconceptions related to the various forms of the Equivalence Principle, the use of conformal frames and equivalence between theories are clarified.
description: Invited paper in the Gravity Research Foundation 2007 special issue to be published by Int. J. Mod. Phys. D
Black holes: interfacing the classical and the quantum
Creators: name: Kosyakov, B. P.
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The central idea advocated in this paper is that {forming the black hole horizon is attended with transition from the classical regime of evolution to the quantum one}. We justify the following criterion for discriminating between the classical and the quantum: {spontaneous creations and annihilations of particle-antiparticle pairs are impossible in the classical world but possible in the quantum world}. We show that it is sufficient to {change the overall sign of the spacetime signature in the classical picture of field propagation for it to be treated as its associated quantum picture}. To describe a self-gravitating object at the last stage of its classical evolution, we propose to use the Foldy--Wouthuysen representation of the Dirac equation in curved spacetimes, and the Gozzi classical path integral. In both approaches, maintaining the dynamics in the classical regime is controlled by supersymmetry.
description: comment: LaTeX, 12 pages
Explaining the MiniBooNE Excess Through a Mixed Model of Oscillation and Decay
Creators: name: Vergani, Stefano
name: Kamp, Nicholas W.
name: Diaz, Alejandro
name: Argüelles, Carlos A.
name: Conrad, Janet M.
name: Shaevitz, Michael H.
name: Uchida, Melissa A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: The electron-like excess observed by the MiniBooNE experiment is explained with a model comprising a new low mass state ($\mathcal{O}(1)$ eV) participating in neutrino oscillations and a new high mass state ($\mathcal{O}(100)$ MeV) that decays to $ν+γ$. Short-baseline oscillation data sets are used to predict the oscillation parameters. Fitting the MiniBooNE energy and scattering angle data, there is a narrow joint allowed region for the decay contribution at 95% CL. The result is a substantial improvement over the single sterile neutrino oscillation model, with $Δχ^2/dof$ = 19.3/2 for a decay coupling of $2.8 \times 10^{-7}$ GeV$^{-1}$, high mass state of 376 MeV, oscillation mixing angle of $7\times 10^{-4}$ and mass splitting of $1.3$ eV$^2$. This model predicts that no clear oscillation signature will be observed in the FNAL short baseline program due to the low signal-level.
description: 16 pages