cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Pairing properties from random distributions of single-particle energy levels
Creators: name: Mamun, A. A.
name: Constantinou, C.
name: Prakash, M.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Exploiting the similarity between the bunched single-particle energy levels of nuclei and of random distributions around the Fermi surface, pairing properties of the latter are calculated to establish statistically-based bounds on the basic characteristics of the pairing phenomenon. When the most probable values for the pairing gaps germane to the BCS formalism are used to calculate thermodynamic quantities, we find that while the ratio of the critical temperature Tc to the zero-temperature pairing gap is close to its BCS Fermi gas value, the ratio of the superfluid to the normal phase specific heats at Tc differs significantly from its Fermi gas counterpart. The largest deviations occur when a few levels lie closely on either side of the Fermi energy but other levels are far away from it. The influence of thermal fluctuations, expected to be large for systems of finite number of particles, were also investigated using a semiclassical treatment of fluctuations. When the average pairing gaps along with those differing by one standard deviations are used, the characteristic discontinuity of the specific heat at Tc in the BCS formalism was transformed to a shoulder-like structure indicating the suppression of a second order phase transition as experimentally observed in nano-particles and several nuclei. Contrasting semiclassical and quantum treatments of fluctuations for the random spacing model is currently underway.
description: 8 pages and 12 figures added in new sections
Projected distances to host galaxy reduce SNIa dispersion
Creators: name: Hill, R.
name: Shariff, H.
name: Trotta, R.
name: Ali-Khan, S.
name: Jiao, X.
name: Liu, Y.
name: Moon, S. K.
name: Parker, W.
name: Paulus, M.
name: van Dyk, D. A.
name: Lucy, L. B.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We use multi-band imagery data from the Sloan Digital Sky Survey (SDSS) to measure projected distances of 302 supernova type Ia (SNIa) from the centre of their host galaxies, normalized to the galaxy's brightness scale length, with a Bayesian approach. We test the hypothesis that SNIas further away from the centre of their host galaxy are less subject to dust contamination (as the dust column density in their environment is smaller) and/or come from a more homogeneous environment. Using the Mann-Whitney U test, we find a statistically significant difference in the observed colour correction distribution between SNIas that are near and those that are far from the centre of their host. The local p-value is 3 x 10^{-3}, which is significant at the 5 per cent level after look-elsewhere effect correction. We estimate the residual scatter of the two subgroups to be 0.073 +/- 0.018 for the far SNIas, compared to 0.114 +/- 0.009 for the near SNIas -- an improvement of 30 per cent, albeit with a low statistical significance of 2sigma. This confirms the importance of host galaxy properties in correctly interpreting SNIa observations for cosmological inference.
description: Major revision including new fits to the host galaxy images and checks of robustness of results. Statistical results are strengthened. Matched version accepted by MNRAS
Bayesian data analysis tools for atomic physics
Creators: name: Trassinelli, Martino
Publisher: name: arXiv
Year: 2016
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: High Energy Physics - Experiment (hep-ex)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We present an introduction to some concepts of Bayesian data analysis in the context of atomic physics. Starting from basic rules of probability, we present the Bayes' theorem and its applications. In particular we discuss about how to calculate simple and joint probability distributions and the Bayesian evidence, a model dependent quantity that allows to assign probabilities to different hypotheses from the analysis of a same data set. To give some practical examples, these methods are applied to two concrete cases. In the first example, the presence or not of a satellite line in an atomic spectrum is investigated. In the second example, we determine the most probable model among a set of possible profiles from the analysis of a statistically poor spectrum. We show also how to calculate the probability distribution of the main spectral component without having to determine uniquely the spectrum modeling. For these two studies, we implement the program Nested fit to calculate the different probability distributions and other related quantities. Nested fit is a Fortran90/Python code developed during the last years for analysis of atomic spectra. As indicated by the name, it is based on the nested algorithm, which is presented in details together with the program itself.
Supersymmetric D-term Twin Higgs
Creators: name: Badziak, Marcin
name: Harigaya, Keisuke
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We propose a new type of supersymmetric Twin Higgs model where the SU(4) invariant quartic term is provided by a D-term potential of a new U(1) gauge symmetry. In the model the 125 GeV Higgs mass can be obtained for stop masses below 1 TeV, and a tuning required to obtain the correct electroweak scale can be as low as 20 %. A stop mass of about 2 TeV is also possible with tuning of order O(10) %.
description: 27 pages, 5 figures; v2: appendix extended, matches version published in JHEP
Combination of searches for heavy resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton-proton collisions at sqrt(s) = 8 and 13 TeV
Creators: name: CMS Collaboration
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: A statistical combination of searches is presented for massive resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton-proton collision data collected by the CMS experiment at the LHC. The data are taken at centre-of-mass energies of 8 and 13 TeV, corresponding to respective integrated luminosities of 19.7 and up to 2.7 inverse femtobarns. The results are interpreted in the context of heavy vector triplet and singlet models that mimic properties of composite-Higgs models predicting W' and Z' bosons decaying to WZ, WW, WH, and ZH bosons. A model with a bulk graviton that decays into WW and ZZ is also considered. This is the first combined search for WW, WZ, WH, and ZH resonances and yields lower limits on masses at 95% confidence level for W' and Z' singlets at 2.3 TeV, and for a triplet at 2.4 TeV. The limits on the production cross section of a narrow bulk graviton resonance with the curvature scale of the warped extra dimension k = 0.5, in the mass range of 0.6 to 4.0 TeV, are the most stringent published to date.
description: Replaced with the published version. Added the journal reference and DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/B2G-16-007 (CMS Public Pages)
Performance Metrics for Systems with Soft-Decision FEC and Probabilistic Shaping
Creators: name: Yoshida, Tsuyoshi
name: Karlsson, Magnus
name: Agrell, Erik
Publisher: name: arXiv
Year: 2017
Subjects: subject: Information Theory (cs.IT)
subject: Optics (physics.optics)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: High-throughput optical communication systems utilize binary soft-decision forward error correction (SD-FEC) with bit interleaving over the bit channels. The generalized mutual information (GMI) is an achievable information rate (AIR) in such systems and is known to be a good predictor of the bit error rate after SD-FEC decoding (post-FEC BER) for uniform signaling. However, for probabilistically shaped (nonuniform) signaling, we find that the normalized AIR, defined as the AIR divided by the signal entropy, is less correlated with the post-FEC BER. We show that the information quantity based on the distribution of the single bit signal, and its asymmetric loglikelihood ratio, are better predictors of the post-FEC BER. In simulations over the Gaussian channel, we find that the prediction accuracy, quantified as the peak-to-peak deviation of the post-FEC BER within a set of different modulation formats and distributions, can be improved more than 10 times compared with the normalized AIR.
description: 4 pages, 3 figures
Presentation: Microzonation of the Earthquake Hazard as a Disaster Mitigation Effort in the Special Region of Yogyakarta
Creators: name: Riswandi, Harry
name: Ikhsan
name: Yohana Noradka Maharani
name: Wijayanto
name: Bambang Sunardi
name: Ayu Krisno Ekarsti
name: Yody Rizkianto
name: Syaifudin, Muhamad
Publisher: name: Zenodo
Year: 2022

description: This material has presented on 1st International Conference on Advanced Research in Engineering and Technology. October 25, 2022
Quantum Hall phase diagram of two-component Bose gases: Intercomponent entanglement and pseudopotentials
Creators: name: Furukawa, Shunsuke
name: Ueda, Masahito
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We study the ground-state phase diagram of two-dimensional two-component (or pseudospin-1/2) Bose gases in a high synthetic magnetic field in the space of the total filling factor and the ratio of the intercomponent coupling $g_{\uparrow\downarrow}$ to the intracomponent one $g>0$. Using exact diagonalization, we find that when the intercomponent coupling is attractive ($g_{\uparrow\downarrow}<0$), the product states of a pair of nearly uncorrelated quantum Hall states are remarkably robust and persist even when $|g_{\uparrow\downarrow}|$ is close to $g$. This contrasts with the case of an intercomponent repulsion, where a variety of spin-singlet quantum Hall states with high intercomponent entanglement emerge for $g_{\uparrow\downarrow}\approx g$. We interpret this marked dependence on the sign of $g_{\uparrow\downarrow}$ in light of pseudopotentials on a sphere, and also explain recent numerical results in two-component Bose gases in mutually antiparallel magnetic fields where a qualitatively opposite dependence on the sign of $g_{\uparrow\downarrow}$ is found. Our results thus unveil an intriguing connection between multicomponent quantum Hall systems and quantum spin Hall systems in minimal setups.
description: 13 pages, 17 figures. v2: Some changes in the result for the total filling factor 4/3
Sea Quarks Contribution to the Nucleon Magnetic Moment and Charge Radius at the Physical Point
Creators: name: Sufian, Raza Sabbir
name: Yang, Yi-Bo
name: Liang, Jian
name: Draper, Terrence
name: Liu, Keh-Fei
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We report a comprehensive analysis of the light and strange disconnected-sea quarks contribution to the nucleon magnetic moment, charge radius, and the electric and magnetic form factors. The lattice QCD calculation includes ensembles across several lattice volumes and lattice spacings with one of the ensembles at the physical pion mass. We adopt a model-independent extrapolation of the nucleon magnetic moment and the charge radius. We have performed a simultaneous chiral, infinite volume, and continuum extrapolation in a global fit to calculate results in the continuum limit. We find that the combined light and strange disconnected-sea quarks contribution to the nucleon magnetic moment is $μ_M\,(\text{DI})=-0.022(11)(09)\,μ_N$ and to the nucleon mean square charge radius is $\langle r^2\rangle_E\,\text{(DI)}=-0.019(05)(05)$ fm$^2$ which is about $1/3$ of the difference between the $\langle r_p^2\rangle_E$ of electron-proton scattering and that of muonic atom and so cannot be ignored in obtaining the proton charge radius in the lattice QCD calculation. The most important outcome of this lattice QCD calculation is that while the combined light-sea and strange quarks contribution to the nucleon magnetic moment is small at about $1\%$, a negative $2.5(9)\%$ contribution to the proton mean square charge radius and a relatively larger positive $16.3(6.1)\%$ contribution to the neutron mean square charge radius come from the sea quarks in the nucleon. For the first time, by performing global fits, we also give predictions of the light and strange disconnected-sea quarks contributions to the nucleon electric and magnetic form factors at the physical point and in the continuum and infinite volume limits in the momentum transfer range of $0\leq Q^2\leq 0.5$ GeV$^2$.
description: Published Version, 26 pages, 8 figures
Toward pole inflation and attractors in supergravity : Chiral matter field inflation
Creators: name: Kobayashi, Tatsuo
name: Seto, Osamu
name: Tatsuishi, Takuya H.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: In string-inspired supergravity theory, Kähler metric of chiral matter fields often has a pole. Such Kähler metric is interesting from the viewpoint of the framework of the pole inflation, where the scalar potential can be stretched out to be flat around the pole for a canonically normalized field and inflation can be realized. However, when Kähler metric has a pole, the scalar potential can also have a pole at the same point in supergravity theory. We study such supergravity models with the pole, and provide numerical analysis of inflationary dynamics and resultant density perturbation. In contrast with usual pole inflation models, inflation in this supergravity based model occurs not on the pole but region apart from the pole. We show that the existence of the pole in the scalar potential is crucial nevertheless. We also examine attractor behavior of our model.
description: 14 pages, 11 figures
Entanglement entropy and particle number cumulants of disordered fermions
Creators: name: Burmistrov, I. S.
name: Tikhonov, K. S.
name: Gornyi, I. V.
name: Mirlin, A. D.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: We study the entanglement entropy and particle number cumulants for a system of disordered noninteracting fermions in $d$ dimensions. We show, both analytically and numerically, that for a weak disorder the entanglement entropy and the second cumulant (particle number variance) are proportional to each other with a universal coefficient. The corresponding expressions are analogous to those in the clean case but with a logarithmic factor regularized by the mean free path rather than by the system size. We also determine the scaling of higher cumulants by analytical (weak disorder) and numerical means. Finally, we predict that the particle number variance and the entanglement entropy are nonanalytic functions of disorder at the Anderson transition.
description: 19 LaTeX pages, 4 figures, elsarticle style
Wavelength-dispersive spectroscopy in the hard x-ray regime of a heavy highly-charged ion: The 1s Lamb shift in hydrogen-like gold
Creators: name: Gassner, T.
name: Trassinelli, M.
name: Heß, R.
name: Spillmann, U.
name: Banas, D.
name: Blumenhagen, K. -H.
name: Bosch, F.
name: Brandau, C.
name: Chen, W.
name: Dimopoulou, C.
name: Förster, E.
name: Grisenti, R.
name: Gumberidze, A.
name: Hagmann, S.
name: Hillenbrand, P. -M.
name: Indelicato, P.
name: Jagodzinski, P.
name: Kämpfer, T.
name: Kozhuharov, C.
name: Lestinsky, M.
name: Liesen, D.
name: Litvinov, Y.
name: Loetzsch, R.
name: Manil, B.
name: Märtin, R.
name: Nolden, F.
name: Petridis, M.
name: Sanjari, M.
name: Schulze, K.
name: Schwemlein, M.
name: Simionovici, A.
name: Steck, M.
name: Stöhlker, T.
name: Szabo, C.
name: Trotsenko, S.
name: Uschmann, I.
name: Weber, G.
name: Wehrhan, O.
name: Winckler, N.
name: Winters, D.
name: Winters, N.
name: Ziegler, E.
name: Beyer, H.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: Accurate spectroscopy of highly charged high-Z ions in a storage ring is demonstrated to be feasible by the use of specially adapted crystal optics. The method has been applied for the measurement of the 1s Lamb shift in hydrogen-like gold (Au 78+) in a storage ring through spectroscopy of the Lyman x rays. This measurement represents the first result obtained for a high-Z element using high-resolution wavelength-dispersive spectroscopy in the hard x-ray regime, paving the way for sensitivity to higher-order QED effects.
Competing spin liquids and hidden nematic order in spin ice with frustrated transverse exchange
Creators: name: Taillefumier, Mathieu
name: Benton, Owen
name: Yan, Han
name: Jaubert, L. D. C.
name: Shannon, Nic
Publisher: name: arXiv
Year: 2017
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho2Ti2O7 and Dy2Ti2O7 exemplify this phenomenon, displaying a classical spin liquid state, with fractionalized magnetic--monopole excitations. Recently there has been great interest in closely-related "quantum spin ice" materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively-entangled, quantum, spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realise a still-richer scenario. Using a combination of classical Monte Carlo simulation, semi--classical molecular--dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three, competing forms of spin liquid, as well as a phase with hidden, spin-nematic, order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.
description: 14 pages (8 in main text), 8 figures (5 in main text). Published in Physical Review X
Relational Quantum Mechanics and Probability
Creators: name: Trassinelli, M.
Publisher: name: arXiv
Year: 2018
Subjects: subject: Quantum Physics (quant-ph)
subject: History and Philosophy of Physics (physics.hist-ph)
subject: FOS: Physical sciences

description: We present a derivation of the third postulate of Relational Quantum Mechanics (RQM) from the properties of conditional probabilities.The first two RQM postulates are based on the information that can be extracted from interaction of different systems, and the third postulate defines the properties of the probability function. Here we demonstrate that from a rigorous definition of the conditional probability for the possible outcomes of different measurements, the third postulate is unnecessary and the Born's rule naturally emerges from the first two postulates by applying the Gleason's theorem. We demonstrate in addition that the probability function is uniquely defined for classical and quantum phenomena. The presence or not of interference terms is demonstrated to be related to the precise formulation of the conditional probability where distributive property on its arguments cannot be taken for granted. In the particular case of Young's slits experiment, the two possible argument formulations correspond to the possibility or not to determine the particle passage through a particular path.
description: Foundations of Physics, Springer Verlag, 2018
CDF Transform-and-Shift: An effective way to deal with datasets of inhomogeneous cluster densities
Creators: name: Zhu, Ye
name: Ting, Kai Ming
name: Carman, Mark
name: Angelova, Maia
Publisher: name: arXiv
Year: 2018
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: The problem of inhomogeneous cluster densities has been a long-standing issue for distance-based and density-based algorithms in clustering and anomaly detection. These algorithms implicitly assume that all clusters have approximately the same density. As a result, they often exhibit a bias towards dense clusters in the presence of sparse clusters. Many remedies have been suggested; yet, we show that they are partial solutions which do not address the issue satisfactorily. To match the implicit assumption, we propose to transform a given dataset such that the transformed clusters have approximately the same density while all regions of locally low density become globally low density -- homogenising cluster density while preserving the cluster structure of the dataset. We show that this can be achieved by using a new multi-dimensional Cumulative Distribution Function in a transform-and-shift method. The method can be applied to every dataset, before the dataset is used in many existing algorithms to match their implicit assumption without algorithmic modification. We show that the proposed method performs better than existing remedies.
description: Pattern Recognition (2021)
Hierarchical clustering that takes advantage of both density-peak and density-connectivity
Creators: name: Zhu, Ye
name: Ting, Kai Ming
name: Jin, Yuan
name: Angelova, Maia
Publisher: name: arXiv
Year: 2018
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: This paper focuses on density-based clustering, particularly the Density Peak (DP) algorithm and the one based on density-connectivity DBSCAN; and proposes a new method which takes advantage of the individual strengths of these two methods to yield a density-based hierarchical clustering algorithm. Our investigation begins with formally defining the types of clusters DP and DBSCAN are designed to detect; and then identifies the kinds of distributions that DP and DBSCAN individually fail to detect all clusters in a dataset. These identified weaknesses inspire us to formally define a new kind of clusters and propose a new method called DC-HDP to overcome these weaknesses to identify clusters with arbitrary shapes and varied densities. In addition, the new method produces a richer clustering result in terms of hierarchy or dendrogram for better cluster structures understanding. Our empirical evaluation results show that DC-HDP produces the best clustering results on 14 datasets in comparison with 7 state-of-the-art clustering algorithms.
Surface structures of tellurium on Si(111)-(7x7) studied by low-energy electron diffraction and scanning tunneling microscopy
Creators: name: Lüpke, Felix
name: Doležal, Jiří
name: Cherepanov, Vasily
name: Ošt'ádal, Ivan
name: Tautz, F. Stefan
name: Voigtländer, Bert
Publisher: name: arXiv
Year: 2018
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The Te-covered Si(111) surface has received recent interest as a template for the epitaxy of van der Waals (vdW) materials, e.g. Bi$_2$Te$_3$. Here, we report the formation of a Te buffer layer on Si(111)$-$(7$\times$7) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While deposition of several monolayer (ML) of Te on the Si(111)$-$(7$\times$7) surface at room temperature results in an amorphous Te layer, increasing the substrate temperature to $770\rm\,K$ results in a weak (7$\times$7) electron diffraction pattern. Scanning tunneling microscopy of this surface shows remaining corner holes from the Si(111)$-$(7$\times$7) surface reconstruction and clusters in the faulted and unfaulted halves of the (7$\times$7) unit cells. Increasing the substrate temperature further to $920\rm\,K$ leads to a Te/Si(111)$-(2\sqrt3\times2\sqrt{3})\rm R30^{\circ}$ surface reconstruction. We find that this surface configuration has an atomically flat structure with threefold symmetry.
Geometric interpretation of the general POE model for a serial-link robot via conversion into D-H parameterization
Creators: name: Wu, Liao
name: Crawford, Ross
name: Roberts, Jonathan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: While Product of Exponentials (POE) formula has been gaining increasing popularity in modeling the kinematics of a serial-link robot, the Denavit-Hartenberg (D-H) notation is still the most widely used due to its intuitive and concise geometric interpretation of the robot. This paper has developed an analytical solution to automatically convert a POE model into a D-H model for a robot with revolute, prismatic, and helical joints, which are the complete set of three basic one degree of freedom lower pair joints for constructing a serial-link robot. The conversion algorithm developed can be used in applications such as calibration where it is necessary to convert the D-H model to the POE model for identification and then back to the D-H model for compensation. The equivalence of the two models proved in this paper also benefits the analysis of the identifiability of the kinematic parameters. It is found that the maximum number of identifiable parameters in a general POE model is 5h+4r +2t +n+6 where h, r, t, and n stand for the number of helical, revolute, prismatic, and general joints, respectively. It is also suggested that the identifiability of the base frame and the tool frame in the D-H model is restricted rather than the arbitrary six parameters as assumed previously.
description: Product of Exponentials (POE), Denavit-Hartenberg (D-H), kinematics, identifiability, ICRA2019
New classes of $C^1$ robustly transitive maps with persistent critical points
Creators: name: Lizana, Cristina
name: Ranter, Wagner
Publisher: name: arXiv
Year: 2019
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 37D30, 37D20, 08A35, 35B38

description: We exhibit a new large class of $C^1$ open examples of robustly transitive maps displaying persistent critical points in the homotopy class of expanding endomorphisms acting on the two dimensional Torus and the Klein bottle.
description: 15 pages, 5 figures
High-order quadrature-based lattice Boltzmann models for the flow of ultrarelativistic rarefied gases
Creators: name: Ambrus, Victor E.
name: Blaga, Robert
Publisher: name: arXiv
Year: 2016
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We present a systematic procedure for the construction of relativistic lattice Boltzmann models (R-SLB) appropriate for the simulation of flows of massless particles. Quadrature rules are used for the discretization of the momentum space in spherical coordinates. The models are optimized for one-dimensional flows. The applications considered in this paper are the Sod shock tube and the one-dimensional boost invariant expansion (Bjorken flow). Our models are tested against exact solutions in the inviscid and ballistic limits. At intermediate relaxation times (finite viscosity), we compare with the results obtained using the Boltzmann approach of multiparton scattering model for the Sod shock tube problem, as well as with a semi-analytic solution for the non-ideal Bjorken flow. In all cases our models give remarkably good results. We define a convergence test in order to find the quadrature order necessary to obtain convergence at a predefined accuracy. We show that, while in the hydrodynamic regime the number of velocities is comparable to that required for the more popular collision-streaming type models, as we go towards the ballistic regime, the size of the velocity set must be substantially increased in order to accurately reproduce the analytic profiles.
description: 43 pages (double column), 16 figures, 4 tables
On some geometric properties of currents and Frobenius theorem
Creators: name: Alberti, Giovanni
name: Massaccesi, Annalisa
Publisher: name: arXiv
Year: 2017
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 58A30, 49Q15, 58A25, 53C17, 46E35

description: In this note we announce some results, due to appear in [2], [3], on the structure of integral and normal currents, and their relation to Frobenius theorem. In particular we show that an integral current cannot be tangent to a distribution of planes which is nowhere involutive (Theorem 3.6), and that a normal current which is tangent to an involutive distribution of planes can be locally foliated in terms of integral currents (Theorem 4.3). This statement gives a partial answer to a question raised by Frank Morgan in [1].
description: 8 pages
Emulating Majorana fermions and their braiding by Ising spin chains
Creators: name: Backens, Stefan
name: Shnirman, Alexander
name: Makhlin, Yuriy
name: Gefen, Yuval
name: Mooij, Johan E.
name: Schön, Gerd
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We analyse the control of Majorana zero-energy states by mapping the fermionic system onto a chain of Ising spins. Although the topological protection is lost for the Ising system, the mapping provides additional insight into the nature of the quantum states. By controlling the local magnetic field, one can separate the Ising chain into ferromagnetic and paramagnetic phases, corresponding to topological and non-topological sections of the fermionic system. In this paper we propose (topologically non-protected) protocols performing the braiding operation, and in fact also more general rotations. We first consider a T-junction geometry, but we also propose a protocol for a purely one-dimensional system. Both setups rely on an extra spin-1/2 coupler. By including the extra spin in the T-junction geometry, we overcome limitations due to the 1D character of the Jordan-Wigner transformation. In the 1D geometry the coupler, which controls one of the Ising links, should be manipulated once the ferromagnetic (topological) section of the chain is moved far away. We also propose experimental implementations of our scheme. One is based on a chain of flux qubits which allows for all needed control fields. We also describe how to translate our scheme for the 1D setup to a chain of superconducting wires hosting each a pair of Majorana edge states.
description: 11 pages, 5 figures, version published in PRB
Fake proofs for identities involving products of Eisenstein series
Creators: name: Khuri-Makdisi, Kamal
Publisher: name: arXiv
Year: 2016
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11F11, 33E05

description: In the workshop of the July 2016 Building Bridges 3 conference in Sarajevo, I presented the results from a joint article with W. Raji (Mathematische Annalen 2017, preprint arXiv:1402.1854). That article gave a proof of various linear relations between products of two Eisenstein series on $Γ(N)$, including an interesting identity related to the action of a Hecke operator on such a product. The real proofs involve some care to deal with issues of convergence. In this note we give "fake" proofs for these identities, ignoring the convergence issues; some of these fake proofs appeared in the workshop lecture as an amusing side note before I sketched the real proofs. Something in these fake proofs is quite suggestive, even though the proofs themselves are clearly invalid (and even produce wrong results). It would be interesting to understand what exactly is going on here.
description: amslatex, 6 pages, 1 figure, lecture notes for talk given in BB3 workshop on automorphic forms and related topics, Sarajevo, July 2016. This version: minor changes for final submission
Adversarial Attacks on Graph Neural Networks via Meta Learning
Creators: name: Zügner, Daniel
name: Günnemann, Stephan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Machine Learning (cs.LG)
subject: Cryptography and Security (cs.CR)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: Deep learning models for graphs have advanced the state of the art on many tasks. Despite their recent success, little is known about their robustness. We investigate training time attacks on graph neural networks for node classification that perturb the discrete graph structure. Our core principle is to use meta-gradients to solve the bilevel problem underlying training-time attacks, essentially treating the graph as a hyperparameter to optimize. Our experiments show that small graph perturbations consistently lead to a strong decrease in performance for graph convolutional networks, and even transfer to unsupervised embeddings. Remarkably, the perturbations created by our algorithm can misguide the graph neural networks such that they perform worse than a simple baseline that ignores all relational information. Our attacks do not assume any knowledge about or access to the target classifiers.
description: ICLR submission
Proof of László Fejes Tóth's zone conjecture
Creators: name: Jiang, Zilin
name: Polyanskii, Alexandr
Publisher: name: arXiv
Year: 2017
Subjects: subject: Metric Geometry (math.MG)
subject: Combinatorics (math.CO)
subject: FOS: Mathematics
subject: 52C17

description: A zone of width $ω$ on the unit sphere is the set of points within spherical distance $ω/2$ of a given great circle. We show that the total width of any collection of zones covering the unit sphere is at least $π$, answering a question of Fejes Tóth from 1973.
description: 10 pages, 3 figures, this version adds some conjectures, accepted to Geom. Funct. Anal., corrections suggested by the referees have been incorporated
Modular forms constructed from moduli of elliptic curves, with applications to explicit models of modular curves
Creators: name: Khuri-Makdisi, Kamal
Publisher: name: arXiv
Year: 2016
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11F11, 14G35

description: These are the lecture notes from my portion of a mini-course for the summer school "Building Bridges 3" that was held in Sarajevo during July 2016. My lectures covered the Katz definition of modular forms, a family of forms defined from this perspective and their relation to Eisenstein series, and methods of finding explicit models of modular curves. The treatment is purely expository, and the results are mostly standard, although a few points of view may not be as widely known as they deserve to be.
description: amslatex, 16 pages, expository lecture notes from BB3 summer school on automorphic forms and related topics, Sarajevo, July 2016. This version: revised after referee's report, ready for final submission
Model-less Active Compliance for Continuum Robots using Recurrent Neural Networks
Creators: name: Jakes, David
name: Ge, Zongyuan
name: Wu, Liao
Publisher: name: arXiv
Year: 2019
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: Endowing continuum robots with compliance while it is interacting with the internal environment of the human body is essential to prevent damage to the robot and the surrounding tissues. Compared with passive compliance, active compliance has the advantages in terms of increasing the force transmission ability and improving safety with monitored force output. Previous studies have demonstrated that active compliance can be achieved based on a complex model of the mechanics combined with a traditional machine learning technique such as a support vector machine. This paper proposes a recurrent neural network based approach that avoids the complexity of modeling while capturing nonlinear factors such as hysteresis, friction and delay of the electronics that are not easy to model. The approach is tested on a 3-tendon single-segment continuum robot with force sensors on each cable. Experiments are conducted to demonstrate that the continuum robot with an RNN based feed-forward controller is capable of responding to external forces quickly and entering an unknown environment compliantly.
description: 7 pages, 13 figures, 1 table, 1 video, IROS2019, typos corrected
New candidates for active asteroids: main-belt (145) Adeona, (704) Interamnia, (779) Nina, (1474) Beira, and near-Earth (162173) Ryugu
Creators: name: Busarev, Vladimir V.
name: Makalkin, Andrei B.
name: Vilas, Faith
name: Barabanov, Sergey I.
name: Scherbina, Marina P.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: For the first time, spectral signs of subtle coma activity were observed simultaneously on four main-belt primitive asteroids (145) Adeona, (704) Interamnia, (779) Nina, and (1474) Beira around their perihelion distances in September 2012, which were interpreted as manifestations of the sublimation of H2O ice in/under the surface matter (Busarev et al., 2015a, 2015b). We confirm the phenomenon for Nina when it approached perihelion in September 2016. At the same time, based on results of spectral observations of near-Earth asteroid (162173) Ryugu (Vilas, 2008) being a target of Japan's Hayabusa 2 space mission, we suspected a periodic similar transient activity on the Cg-type asteroid. However, unlike the main-belt primitive asteroids demonstrating sublimation of ices close to their perihelion distances, the effect on Ryugu was apparently registered near aphelion. To explain the difference, we calculated the subsolar temperature depending on heliocentric distance of the asteroids, considered qualitative models of internal structure of main-belt and near-Earth primitive asteroids including ice and performed some analytical estimations. Presumed temporal sublimation/degassing activity of Ryugu points to the existence of a residual frozen core in its interior. It could be an indication of a relatively recent transition of the asteroid from the main asteroid belt to the near-Earth area.
description: 26 pages, 14 figures, 1 table; submitted to Icarus 2017
On the proof of the Thin Sandwich Conjecture in arbitrary dimensions
Creators: name: Avalos, R.
name: Dahia, F.
name: Romero, C.
name: Lira, J. H.
Publisher: name: arXiv
Year: 2017
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Differential Geometry (math.DG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: In this paper we show the validity, under certain geometric conditions, of Wheeler's thin sandwich conjecture for higher dimensional theories of gravity. We extend the results shown by R. Bartnik and G. Fodor for the 3-dimensional case in two ways. On the one hand, we show that the results obtained by the mentioned authors are valid in arbitrary dimensions, and on the other hand we show that the geometric hypotheses needed for the proofs can always be satisfied, which constitutes in itself a new result for the 3-dimensional case. In this way, we show that on any compact n-dimensional manifold, n greater or equal to 3, there is an open set in the space of all possible initial data where the thin sandwich problem is well-posed.
description: 17 pages
Improper coloring of graphs with no odd clique minor
Creators: name: Kang, Dong Yeap
name: Oum, Sang-il
Publisher: name: arXiv
Year: 2016
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics
subject: 05C15, 05C83

description: As a strengthening of Hadwiger's conjecture, Gerards and Seymour conjectured that every graph with no odd $K_t$ minor is $(t-1)$-colorable. We prove two weaker variants of this conjecture. Firstly, we show that for each $t \geq 2$, every graph with no odd $K_t$ minor has a partition of its vertex set into $6t-9$ sets $V_1, \dots, V_{6t-9}$ such that each $V_i$ induces a subgraph of bounded maximum degree. Secondly, we prove that for each $t \geq 2$, every graph with no odd $K_t$ minor has a partition of its vertex set into $10t-13$ sets $V_1, \dots, V_{10t-13}$ such that each $V_i$ induces a subgraph with components of bounded size. The second theorem improves a result of Kawarabayashi (2008), which states that the vertex set can be partitioned into $496t$ such sets.
description: 15 pages
Efficient Evaluation of Cosmological Angular Statistics
Creators: name: Assassi, Valentin
name: Simonović, Marko
name: Zaldarriaga, Matias
Publisher: name: arXiv
Year: 2017
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Angular statistics of cosmological observables are hard to compute. The main difficulty is due to the presence of highly-oscillatory Bessel functions which need to be integrated over. In this paper, we provide a simple and fast method to compute the angular power spectrum and bispectrum of any observable. The method is based on using an FFTlog algorithm to decompose the momentum-space statistics onto a basis of power-law functions. For each power law, the integrals over Bessel functions have a simple analytical solution. This allows us to efficiently evaluate these integrals, independently of the value of the multipole $\ell$. In particular, this method significantly speeds up the evaluation of the angular bispectrum compared to existing methods. To illustrate our algorithm, we compute the galaxy, lensing and CMB temperature angular power spectrum and bispectrum.
description: 31 pages, 10 figures, 2 tables. Added section on redshift space distortions. Added section on parameters and performances in appendix. Several minor modifications to match the published version in JCAP. (Title in published version changed)
Topological Protection of Coherence in a Dissipative Environment
Creators: name: Venuti, Lorenzo Campos
name: Ma, Zhengzhi
name: Saleur, Hubert
name: Haas, Stephan
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: One dimensional topological insulators are characterized by edge states with exponentially small energies. According to one generalization of topological phases to non-Hermitian systems, a finite system in a non-trivial topological phase displays surface states with exponentially long life times. In this work we explore the possibility of exploiting such non-Hermitian topological phases to enhance the quantum coherence of a fiducial qubit embedded in a dissipative environment. We first show that a network of qubits interacting with lossy cavities can be represented, in a suitable super-one-particle sector, by a non-Hermitian "Hamiltonian" of the desired form. We then study, both analytically and numerically, one-dimensional geometries with up to three sites per unit cell, and up to a topological winding number $W=2$. For finite-size systems the number of edge modes is a complicated function of $W$ and the system size $N$. However we find that there are precisely $W$ modes localized at one end of the chain. In such topological phases the quibt's coherence lifetime is exponentially large in the system size. We verify that, for $W>1$, at large times, the Lindbladian evolution is approximately a non-trivial unitary. For $W=2$ this results in Rabi-like oscillations of the qubit's coherence measure.
description: 10 pages, 10 figures
Atmospheric escape from the TRAPPIST-1 planets and implications for habitability
Creators: name: Dong, Chuanfei
name: Jin, Meng
name: Lingam, Manasvi
name: Airapetian, Vladimir S.
name: Ma, Yingjuan
name: van der Holst, Bart
Publisher: name: arXiv
Year: 2017
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: The presence of an atmosphere over sufficiently long timescales is widely perceived as one of the most prominent criteria associated with planetary surface habitability. We address the crucial question as to whether the seven Earth-sized planets transiting the recently discovered ultracool dwarf star TRAPPIST-1 are capable of retaining their atmospheres. To this effect, we carry out numerical simulations to characterize the stellar wind of TRAPPIST-1 and the atmospheric ion escape rates for all the seven planets. We also estimate the escape rates analytically and demonstrate that they are in good agreement with the numerical results. We conclude that the outer planets of the TRAPPIST-1 system are capable of retaining their atmospheres over billion-year timescales. The consequences arising from our results are also explored in the context of abiogenesis, biodiversity, and searches for future exoplanets. In light of the many unknowns and assumptions involved, we recommend that these conclusions must be interpreted with due caution.
description: 19 pages, 4 figures, 3 tables
Asymptotic behavior of a Bingham Flow in thin domains with rough boundary
Creators: name: Cardone, Giuseppe
name: Perugia, Carmen
name: Pesqueira, Manuel Villanueva
Publisher: name: arXiv
Year: 2019
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 76A05, 76A20, 76D08, 76M50, 74K10, 35B27

description: We consider an incompressible Bingham flow in a thin domain with rough boundary, under the action of given external forces and with no-slip boundary condition on the whole boundary of the domain. In mathematical terms, this problem is described by non linear variational inequalities over domains where a small parameter $ε$ denotes the thickness of the domain and the roughness periodicity of the boundary. By using an adapted linear unfolding operator we perform a detailed analysis of the asymptotic behavior of the Bingham flow when $ε$ tends to zero. We obtain the homogenized limit problem for the velocity and the pressure, which preserves the nonlinear character of the flow, and study the effects of the microstructure in the corresponding effective equations. Finally, we give the interpretation of the limit problem in terms of a non linear Darcy law.
description: 23 pages, 2 figures
On Deformations of Nodal Hypersurfaces
Creators: name: Wang, Zhenjian
Publisher: name: arXiv
Year: 2017
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: Primary 32S35, Secondary 14C30, 14D07, 32S25

description: We extend the infinitesimal Torelli theorem for smooth hypersurfaces to nodal hypersurfaces.
description: to appear in Canadian Mathematical Bulletin