cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
C58 on Au(111): A scanning tunneling microscopy study
Creators: name: Bajales, Noelia
name: Schmaus, Stefan
name: Miyamashi, Toshio
name: Wulfhekel, Wulf
name: Wilhelm, Jan
name: Walz, Michael
name: Stendel, Melanie
name: Bagrets, Alexei
name: Evers, Ferdinand
name: Ulas, Seyithan
name: Kern, Bastian
name: Böttcher, Artur
name: Kappes, Manfred M.
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 530 Physik

description: C58 fullerenes were adsorbed onto room temperature Au(111) surface by low-energy (∼6 eV) cluster ion beam deposition under ultrahigh vacuum conditions. The topographic and electronic properties of the deposits were monitored by means of scanning tunnelling microscopy (STM at 4.2 K). Topographic images reveal that at low coverages fullerene cages are pinned by point dislocation defects on the herringbone reconstructed gold terraces (as well as by step edges). At intermediate coverages, pinned monomers act as nucleation centres for the formation of oligomeric C58 chains and 2D islands. At the largest coverages studied, the surface becomes covered by 3D interlinked C58 cages. STM topographic images of pinned single adsorbates are essentially featureless. The corresponding local densities of states are consistent with strong cage-substrate interactions. Topographic images of [C58]n oligomers show a stripe-like intensity pattern oriented perpendicular to the axis connecting the cage centers. This striped pattern becomes even more pronounced in maps of the local density of states. As supported by density functional theory, DFT calculations, and also by analogous STM images previously obtained for C60 polymers [M. Nakaya, Y. Kuwahara, M. Aono, and T. Nakayama, J. Nanosci. Nanotechnol. 11, 2829 (2011)] https://doi.org/10.1166/jnn.2011.3898., we conclude that these striped orbital patterns are a fingerprint of covalent intercage bonds. For thick C58 films we have derived a bandgap of 1.2 eV from scanning tunnelling spectroscopy data confirming that the outermost C58 layer behaves as a wide band semiconductor.
Finite-Size Effects and Irrelevant Corrections to Scaling Near the Integer Quantum Hall Transition
Creators: name: Obuse, Hideaki
name: Gruzberg, Ilya A.
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2012
Subjects: subject: 530 Physik

description: We present a numerical finite-size scaling study of the localization length in long cylinders near the integer quantum Hall transition employing the Chalker-Coddington network model. Corrections to scaling that decay slowly with increasing system size make this analysis a very challenging numerical problem. In this work we develop a novel method of stability analysis that allows for a better estimate of error bars. Applying the new method we find consistent results when keeping second (or higher) order terms of the leading irrelevant scaling field. The knowledge of the associated (negative) irrelevant exponent y is crucial for a precise determination of other critical exponents, including multifractal spectra of wave functions. We estimate |y|≳0.4, which is considerably larger than most recently reported values. Within this approach we obtain the localization length exponent 2.62±0.06 confirming recent results. Our stability analysis has broad applicability to other observables at integer quantum Hall transition, as well as other critical points where corrections to scaling are present.
Signature of the Dirac cone in the properties of linear oligoacenes
Creators: name: Korytár, Richard
name: Xenioti, Dimitra
name: Schmitteckert, Peter
name: Alouani, Mébarek
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: Organic electronics offers prospects of functionality for science, industry and medicine that are new as compared with silicon technology and available at a very low material cost. Among the plethora of organic molecules available for materials design, polymers and oligomers are very promising, for example, because of their mechanical flexibility. They consist of repeated basic units, such as benzene rings, and the number of these units N determines their excitation gap, a property that is often used in proposals of organic photovoltaics. Here, we show that contrary to a widely held belief the magnitudes of excitation gaps do not always decay monotonously with N, but can oscillate due to the presence of a ‘Dirac cone’ in the band structure. With an eye on the more fundamental question how a molecular wire becomes metallic with increasing length, our research suggests that the process can exhibit incommensurate oscillations.
description: beim Verlag kostenfrei zum Download!
MPEC 2023-H247 : 2023 HA7
Creators: name: Minor Planet Center Staff
Publisher: name: The Minor Planet Center
Year: 2023
Subjects: subject: Small Solar System bodies
valueUri: http://astrothesaurus.org/uat/1469
subject: 2023 HA7

description: The Minor Planet Electronic Circulars contain information on unusual minor planets, routine data on comets and natural satellites, and occasional editorial announcements.  They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145
Creators: name: Johnson, Ryan E.
name: ZuHone, John A.
name: Jones, Christine
name: Forman, William
name: Markevitch, Maxim
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based its unique multiwavelength morphology. Our X-ray analysis confirms the core gas is undergoing "sloshing" resulting from a prior, large scale, gravitational perturbation. In combination with extensive multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M=4.8$\pm2.4 \times$ 10$^{14}$ M$_{\odot}$ has previously ($\gtrsim$0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.
description: 17 pages, 5 figures; higher resolution figures available in online ApJ version
Comprehensive and integrative analysis of the KMT2D regulome
Creators: name: Topham, James T.
Publisher: name: University of British Columbia
Year: 2017

description: Lysine (K)-specific methyltransferase 2D (KMT2D) is a critical component of epigenetic regulation through its role in mono-methylation of lysine 4 of histone H3 (H3K4me1). KMT2D is among the most frequently mutated genes in many forms of cancer, with particularly high occurrence of mutation in lymphoid malignancies. Despite being the recurrent target of somatic alteration across many cancer types, the consequences of KMT2D mutation, and their relevance to tumorigenesis, remain unclear. To expand on the current understanding of KMT2D loss, I performed comprehensive and integrative bioinformatics analyses of the epigenetic and transcriptome landscapes of isogenic KMT2D-mutant HEK293A cell lines. Analysis of ChIP-sequencing data from KMT2D-mutant cells showed genome-wide alterations in the distribution of H3K4me1, with loss of H3K4me1 occurring at active and poised enhancer regions. Interestingly, epigenetic disruption of enhancers in KMT2D-mutant cells was not sufficient for inducing transcriptional alteration of nearby genes, indicating a possible requirement for additional co-factors to be present in order to observe the consequences of KMT2D-dependent enhancer loss. Genes associated with KMT2D-dependent enhancers were enriched for members of the TGF-beta and retinoic acid (RA) signaling networks, highlighting transcriptional response to these pathways as candidate processes in which functional KMT2D-dependent enhancers may be required. Given the roles of both TGF-beta and RA signaling in cancer, identification of the convergence between the KMT2D regulome and these signaling axes provides a potential means by which KMT2D mutations may contribute to tumorigenesis.
Multiple crossing points and possible quantum criticality in the magnetoresistance of thin TiN films
Creators: name: Kronfeldner, Klaus
name: Baturina, Tatyana I.
name: Strunk, Christoph
Publisher: name: Universität Regensburg
Year: 2021
Subjects: subject: 530 Physik

description: We have measured R(T,B) of a TiN thin film very close to the disorder-driven superconductor-insulator transition but still superconducting at zero field and low temperatures. In a magnetic field we find that three distinct crossing points of the magnetoresistance isotherms occur at magnetic fields BcX in three different temperature regions. Each crossing point in R(T,B) corresponds to a plateau in R(T,BcX). We systematically study the evolution of these crossing points near the disorder-induced superconductor/insulator transition, identify the most promising candidate for a quantum phase transition, and provide estimates for the two critical exponents z and ν.
Transport properties of individual C60-molecules
Creators: name: Géranton, G.
name: Seiler, C.
name: Bagrets, A.
name: Venkataraman, L.
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2013
Subjects: subject: 530 Physik

description: Electrical and thermal transport properties of C60 molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C60 with a tendency to promote the sp2-hybridization into an sp3-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model.
Inverse Problems for deformation rings
Creators: name: Bleher, Frauke M.
name: Chinburg, Ted
name: de Smit, Bart
Publisher: name: arXiv
Year: 2010
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11F80

description: Let $\mathcal{W}$ be a complete local commutative Noetherian ring with residue field $k$ of positive characteristic $p$. We study the inverse problem for the versal deformation rings $R_{\mathcal{W}}(Γ,V)$ relative to $\mathcal{W}$ of finite dimensional representations $V$ of a profinite group $Γ$ over $k$. We show that for all $p$ and $n \ge 1$, the ring $\mathcal{W}[[t]]/(p^n t,t^2)$ arises as a universal deformation ring. This ring is not a complete intersection if $p^n\mathcal{W}\neq\{0\}$, so we obtain an answer to a question of M. Flach in all characteristics. We also study the `inverse inverse problem' for the ring $\mathcal{W}[[t]]/(p^n t,t^2)$; this is to determine all pairs $(Γ, V)$ such that $R_{\mathcal{W}}(Γ,V)$ is isomorphic to this ring.
description: 17 pages; this paper is closely related to arXiv:1003.3143. In the third version, we added a new Section 5 with further examples
Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition
Creators: name: Heo, J.
name: Chung, H. J.
name: Lee, Sung-Hoon
name: Yang, H.
name: Seo, D. H.
name: Shin, J. K.
name: Chung, U-In
name: Seo, S.
name: Hwang, E. H.
name: Sarma, S. Das
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Temperature-dependent resistivity of graphene grown by chemical vapor deposition (CVD) is investigated. We observe in low mobility CVD graphene device a strong insulating behavior at low temperatures and a metallic behavior at high temperatures manifesting a non-monotonic in the temperature dependent resistivity.This feature is strongly affected by carrier density modulation. To understand this anomalous temperature dependence, we introduce thermal activation of charge carriers in electron-hole puddles induced by randomly distributed charged impurities. Observed temperature evolution of resistivity is then understood from the competition among thermal activation of charge carriers, temperature-dependent screening and phonon scattering effects. Our results imply that the transport property of transferred CVD-grown graphene is strongly influenced by the details of the environment
description: 7 pages, 3 figures
Happy Enough to Relax? How Positive and Negative Emotions Activate Different Muscular Regions in the Back - an Explorative Study
Creators: name: Scheer, Clara
name: Kubowitsch, Simone
name: Dendorfer, Sebastian
name: Jansen, Petra
Publisher: name: Universität Regensburg
Year: 2021

description: Embodiment theories have proposed a reciprocal relationship between emotional state and bodily reactions. Besides large body postures, recent studies have found emotions to affect rather subtle bodily expressions, such as slumped or upright sitting posture. This study investigated back muscle activity as an indication of an effect of positive and negative emotions on the sitting position. The electromyography (EMG) activity of six back muscles was recorded in 31 healthy subjects during exposure to positive and negative affective pictures. A resting period was used as a control condition. Increased muscle activity patterns in the back were found during the exposure to negative emotional stimuli, which was mainly measured in the lumbar and thorax regions. The positive emotion condition caused no elevated activity. The findings show that negative emotions lead to increased differential muscle activity in the back and thus corroborate those of previous research that emotion affects subtle bodily expressions.
Size difference between Halpha and cold dust in z~2 dusty star forming galaxies
Creators: name: Chen, Chian-Chou
Publisher: name: Zenodo
Year: 2019

description: Star-formation rates (SFRs) are among the most fundamental measurements to galaxy formation models, yet there is still a lack of agreement between measurements made using different methods, expecially when it comes to accounting for dust-obscured SFRs from nebular emission lines at z~1-3, the epoch when over 80% of the cosmic SFR density is obscured by dust. Part of the problem is hinged on a lack of knowledge with regard to the spatial distributions of dust relative to star-forming regions traced by optical emission lines, which requires both near-infrared IFU and sub-arcsecond far-infrared continuum observations that are only available recently. In this talk I will present results from our ongoing program to study dusty star-forming galaxies at z~2 that are detected in Halpha by the IFU from KMOS/SINFONI, as well as in
far-infrared continuum by ALMA with a matched spatial resolution. I will present the relative spatial distributions of these two tracers of SFRs and their sizes. I will discuss the impact of our findings on galaxy formation models in general, as well as on the planning of future IFU observations by JWST and ELT.
Diffuse Galactic Gamma Rays at intermediate and high latitudes. I. Constraints on the ISM properties
Creators: name: Cholis, I.
name: Tavakoli, M.
name: Evoli, C.
name: Maccione, L.
name: Ullio, P.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study the high latitude (|b|>10) diffuse gamma-ray emission in the Galaxy in light of the recently published data from the Fermi collaboration at energies between 100 MeV and 100 GeV. The unprecedented accuracy in these measurements allows to probe and constrain the properties of sources and propagation of cosmic rays (CRs) in the Galaxy, as well as confirming conventional assumptions made on the interstellar medium (ISM). Using the publicly available DRAGON code, that has been shown to reproduce local measurements of CRs, we study assumptions made in the literature on HI and H2 gas distributions in the ISM, and non spatially uniform models of diffusion in the Galaxy. By performing a combined analysis of CR and gamma-ray spectra, we derive constraints on the properties of the ISM gas distribution and the vertical scale height of galactic CR diffusion, which may have implications also on indirect Dark Matter detection. We also discuss some of the possible interpretations of the break at ~230 GV in CR protons and helium spectra, recently observed by PAMELA and their impact on gamma-rays.
description: 28 pages, 18 figures, 2 Tables. changes in v2: added 2 appendices, 1 table and 4 figures, small revision in text, results and conclusions unchanged
Young Massive Star Clusters as Cosmic Abundance Probes
Creators: name: Davies, Ben
Publisher: name: Zenodo
Year: 2019

description: Studying a galaxy's present-day chemical abundances provides information on its star-forming history. Cosmological simulations of galaxy evolution make predictions about the relative metal contents of galaxies as a function of their stellar mass, a trend known as the mass-metallicity relation. These predictions can be tested with observations of nearby galaxies.  However, providing reliable, accurate abundance measurements at extragalactic distances is extremely challenging.  Our team has developed a technique to extract abundance information from individual red supergiant (RSG) stars at megaparsec distances, using KMOS as the workhorse instrument. We have expanded this project to study young massive star clusters containing dozens of RSGs, which allows us to study galaxies at even larger distances. This has ultimately allowed us to construct a mass-metallicity relation for nearby galaxies, which I will present here.
CP2K: An electronic structure and molecular dynamics software package - Quickstep: Efficient and accurate electronic structure calculations
Creators: name: Kühne, Thomas D.
name: Iannuzzi, Marcella
name: Del Ben, Mauro
name: Rybkin, Vladimir V.
name: Seewald, Patrick
name: Stein, Frederick
name: Laino, Teodoro
name: Khaliullin, Rustam Z.
name: Schütt, Ole
name: Schiffmann, Florian
name: Golze, Dorothea
name: Wilhelm, Jan
name: Chulkov, Sergey
name: Bani-Hashemian, Mohammad Hossein
name: Weber, Valéry
name: Borštnik, Urban
name: Taillefumier, Mathieu
name: Jakobovits, Alice Shoshana
name: Lazzaro, Alfio
name: Pabst, Hans
name: Müller, Tiziano
name: Schade, Robert
name: Guidon, Manuel
name: Andermatt, Samuel
name: Holmberg, Nico
name: Schenter, Gregory K.
name: Hehn, Anna
name: Bussy, Augustin
name: Belleflamme, Fabian
name: Tabacchi, Gloria
name: Glöß, Andreas
name: Lass, Michael
name: Bethune, Iain
name: Mundy, Christopher J.
name: Plessl, Christian
name: Watkins, Matt
name: VandeVondele, Joost
name: Krack, Matthias
name: Hutter, Jürg
Publisher: name: Universität Regensburg
Year: 2020
Subjects: subject: 530 Physik

description: CP2K is an open source electronic structure and molecular dynamics software package to perform atomistic simulations of solid-state, liquid, molecular, and biological systems. It is especially aimed at massively parallel and linear-scaling electronic structure methods and state-of-the-art ab initio molecular dynamics simulations. Excellent performance for electronic structure calculations is achieved using novel algorithms implemented for modern high-performance computing systems. This review revisits the main capabilities of CP2K to perform efficient and accurate electronic structure simulations. The emphasis is put on density functional theory and multiple post–Hartree–Fock methods using the Gaussian and plane wave approach and its augmented all-electron extension.
Resonance shifts and spill-out effects in self-consistent hydrodynamic nanoplasmonics
Creators: name: Toscano, Giuseppe
name: Straubel, Jakob
name: Kwiatkowski, Alexander
name: Rockstuhl, Carsten
name: Evers, Ferdinand
name: Xu, Hongxing
name: Asger Mortensen, N.
name: Wubs, Martijn
Publisher: name: Universität Regensburg
Year: 2015
Subjects: subject: Condensed-matter physics, Nanophotonics and plasmonics, Nanowires, Theoretical physics
subject: 530 Physik

description: The standard hydrodynamic Drude model with hard-wall boundary conditions can give accurate quantitative predictions for the optical response of noble-metal nanoparticles. However, it is less accurate for other metallic nanosystems, where surface effects due to electron density spill-out in free space cannot be neglected. Here we address the fundamental question whether the description of surface effects in plasmonics necessarily requires a fully quantum-mechanical ab initio approach. We present a self-consistent hydrodynamic model (SC-HDM), where both the ground state and the excited state properties of an inhomogeneous electron gas can be determined. With this method we are able to explain the size-dependent surface resonance shifts of Na and Ag nanowires and nanospheres. The results we obtain are in good agreement with experiments and more advanced quantum methods. The SC-HDM gives accurate results with modest computational effort, and can be applied to arbitrary nanoplasmonic systems of much larger sizes than accessible with ab initio methods.
description: beim Verlag kostenfrei zum Download!
Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob's Ladder
Creators: name: Duignan, Timothy T.
name: Schenter, Gregory K.
name: Fulton, John L.
name: Huthwelker, Thomas
name: Balasubramanian, Mahalingam
name: Galib, Mirza
name: Baer, Marcel D.
name: Wilhelm, Jan
name: Hutter, Jürg
name: Del Ben, Mauro
name: Zhao, X. S.
name: Mundy, Christopher J.
Publisher: name: Universität Regensburg
Year: 2020
Subjects: subject: 530 Physik

description: The ability to reproduce the experimental structure of water around the sodium and potassium ions is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena. Here, we simulate the Na+ and K+ ions in bulk water using three density functional theory functionals: (1) the generalized gradient approximation (GGA) based dispersion corrected revised Perdew, Burke, and Ernzerhof functional (revPBE-D3) (2) the recently developed strongly constrained and appropriately normed (SCAN) functional (3) the random phase approximation (RPA) functional for potassium. We compare with experimental X-ray diffraction (XRD) and X-ray absorption fine structure (EXAFS) measurements to demonstrate that SCAN accurately reproduces key structural details of the hydration structure around the sodium and potassium cations, whereas revPBE-D3 fails to do so. However, we show that SCAN provides a worse description of pure water in comparison with revPBE-D3. RPA also shows an improvement for K+, but slow convergence prevents rigorous comparison. Finally, we analyse cluster energetics to show SCAN and RPA have smaller fluctuations of the mean error of ion–water cluster binding energies compared with revPBE-D3.
The cosmological free-free signal from galaxy groups and clusters
Creators: name: Ponente, P. P.
name: Diego, J. M.
name: Sheth, R. K.
name: Burigana, C.
name: Knollmann, S. R.
name: Ascasibar, Y.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Using analytical models and cosmological N-body simulations, we study the free-free radio emission from ionized gas in clusters and groups of galaxies. The results obtained with the simulations are compared with analytical predictions based on the mass function and scaling relations. Earlier works based on analytical models have shown that the average free-free signal from small haloes (galaxies) during and after the reionization time could be detected with future experiments as a distortion of the CMB spectrum at low frequencies ($ν 10^{13} h^{-1} M_{\odot}$ is less than 10% the signal from the more abundant and colder smaller mass haloes. However, the individual signal from the massive haloes could be detected with future experiments opening the door for a new window to study the intracluster medium.
description: 11 pages, 7 figures
Electron-Vibration Interaction in the Presence of a Switchable Kondo Resonance Realized in a Molecular Junction
Creators: name: Rakhmilevitch, D.
name: Korytár, R.
name: Bagrets, A.
name: Evers, Ferdinand
name: Tal, O.
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: The interaction of individual electrons with vibrations has been extensively studied. However, the nature of electron-vibration interaction in the presence of many-body electron correlations such as a Kondo state has not been fully investigated. Here, we present transport measurements on a Copper-phthalocyanine molecule, suspended between two silver electrodes in a break-junction setup. Our measurements reveal both zero bias and satellite conductance peaks, which are identified as Kondo resonances with a similar Kondo temperature. The relation of the satellite peaks to electron-vibration interaction is corroborated using several independent spectroscopic indications, as well as ab initio calculations. Further analysis reveals that the contribution of vibration-induced inelastic current is significant in the presence of a Kondo resonance.
Kinetic helicity decay in linearly forced turbulence
Creators: name: Brandenburg, Axel
name: Petrosyan, Arakel
Publisher: name: arXiv
Year: 2010
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Chaotic Dynamics (nlin.CD)
subject: Atmospheric and Oceanic Physics (physics.ao-ph)
subject: Fluid Dynamics (physics.flu-dyn)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: The decay of kinetic helicity is studied in numerical models of forced turbulence using either an externally imposed forcing function as an inhomogeneous term in the equations or, alternatively, a term linear in the velocity giving rise to a linear instability. The externally imposed forcing function injects energy at the largest scales, giving rise to a turbulent inertial range with nearly constant energy flux while for linearly forced turbulence the spectral energy is maximum near the dissipation wavenumber. Kinetic helicity is injected once a statistically steady state is reached, but it is found to decay on a turbulent time scale regardless of the nature of the forcing and the value of the Reynolds number.
description: 7 pages, 8 figures, Astron. Nachr. (accepted)
Nonlinear dynamics of oscillons and transients during preheating after single field inflation
Creators: name: Jia, Tianyu
name: Sang, Yu
name: Zhang, Xue
Publisher: name: arXiv
Year: 2024
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In the single-field model, the preheating process occurs through self-resonance of inflaton field. We study the nonlinear structures generated during preheating in the $α$-attractor models and monodromy models. The potentials have a power law form $\propto\left|ϕ\right|^{2n}$ near the origin and a flat region away from bottom, which are consistent with current cosmological observations. The Floquet analysis shows that potential parameters in monodromy model have a significant influence on the region of resonance bands. Besides we investigate the formation of nonlinear structures, the equation of state and the energy transfer through the (3+1) dimensional lattice simulation. We find that all the models exhibit similar nonlinear dynamics. Furthermore, our analysis reveals that the behavior of the inflation model at small field values, which is governed by the parameter $n$, exerts a more substantial influence on the nonlinear dynamics. The behavior at large field values, controlled by the parameter $q$, has a negligible impact.
description: 15 pages, 12 figures, 2 tables; accepted version by Phys.Rev.D
Fine compactified Jacobians
Creators: name: Melo, Margarida
name: Viviani, Filippo
Publisher: name: arXiv
Year: 2010
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14H10, 14H40, 14D22

description: We study Esteves's fine compactified Jacobians for nodal curves. We give a proof of the fact that, for a one-parameter regular local smoothing of a nodal curve $X$, the relative smooth locus of a relative fine compactified Jacobian is isomorphic to the Néron model of the Jacobian of the general fiber, and thus it provides a modular compactification of it. We show that each fine compactified Jacobian of $X$ admits a stratification in terms of certain fine compactified Jacobians of partial normalizations of $X$ and, moreover, that it can be realized as a quotient of the smooth locus of a suitable fine compactified Jacobian of the total blowup of $X$. Finally, we determine when a fine compactified Jacobian is isomorphic to the corresponding Oda-Seshadri's coarse compactified Jacobian.
description: 35 pages; final version, to appear in Math. Nach
Mechanics and dynamics of multi-point threading of thin-walled oil pipes
Creators: name: Rezayi Khoshdarregi, Mohammad
Publisher: name: University of British Columbia
Year: 2017

description: The pipelines used in the offshore extraction of oil and gas are connected by threaded joints. Any geometrical error or vibration marks left on the thread surface during the machining process can lead to stress concentration and fatigue failure of the joint. Such instances in the past have led to massive oil leakage and environmental disasters. Threading is a form cutting operation resulting in wide chips with complex geometries. Multi-point inserts used in mass production can have different custom profiles on each tooth. The chip thickness as well as the effective oblique cutting angles, cutting force coefficients, and direction of local forces vary along the cutting edge. Since the tool moves one thread pitch over each spindle revolution, the vibration marks left by a tooth affect the chip thickness on the following tooth. Threading of oil pipes imposes additional complexities due to the flexural vibrations of thin-walled pipes, which lead to severe chatter instability. This thesis develops a novel and generalized model to formulate, simulate, and optimize general multi-point threading processes. A systematic semi-analytical methodology is first proposed to determine the chip geometry for custom multi-point inserts with arbitrary infeed strategies. A search algorithm is developed to systematically discretize the chip area along the cutting edge considering the chip flow direction and chip compression at the corners. The cutting force coefficients are evaluated locally for each element, and the resultant forces are summed up over the engaged teeth. Multi-mode vibrations of the tool and pipe are projected in the direction of local chip thickness, and the dynamic cutting and process damping forces are calculated locally along the cutting edge. A novel chip regeneration model for multi-point threading is developed, and stability is investigated in frequency domain using Nyquist criterion. The process is simulated by a time-marching numerical method based on semi-discretization. An optimization algorithm is developed to maximize productivity while respecting machine's limits. The proposed models have been verified experimentally through real scale experiments. The algorithms are integrated into a research software which enables the industry to optimize the process ahead of costly trials.
Properties and scaling relations of ionized gas outflows at z~2
Creators: name: Davies, Rebecca
Publisher: name: Zenodo
Year: 2019

description: Outflows are ubiquitous at the peak epoch of star formation (z~1-3), and are likely to play an important role in shaping the growth and evolution of galaxies. Near-IR integral field spectroscopy is a powerful tool to investigate the physical properties of galactic winds at this epoch because it enables us to kinematically disentangle them from gravitational motions, and to map the launch sites, extent, and geometry of outflows. I will present results from our SINFONI and KMOS outflow studies at z~1-3, focusing on properties and scaling relations of SF-driven outflows resolved on ~1-2 kpc scales. We find clear evidence for faster outflows with larger mass loading factors in regions with higher local star formation surface density. The vast majority of the outflowing material does not have sufficient velocity to escape from the galaxy halos, but will be re-accreted and contribute to the build up of stellar mass and angular momentum in these galaxies. I will discuss these results in the context of our other IFU outflow studies from the SINS/zC-SINF and KMOS^3D surveys (including AGN driven outflows).
Cosmological Constant: A Lesson from Bose-Einstein Condensates
Creators: name: Finazzi, Stefano
name: Liberati, Stefano
name: Sindoni, Lorenzo
Publisher: name: arXiv
Year: 2011
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: The cosmological constant is one of the most pressing problems in modern physics. We address this issue from an emergent gravity standpoint, by using an analogue gravity model. Indeed, the dynamics of the emergent metric in a Bose-Einstein condensate can be described by a Poisson-like equation with a vacuum source term reminiscent of a cosmological constant. The direct computation of this term shows that in emergent gravity scenarios this constant may be naturally much smaller than the naive ground-state energy of the emergent effective field theory. This suggests that a proper computation of the cosmological constant would require a detailed understanding about how Einstein equations emerge from the full microscopic quantum theory. In this light, the cosmological constant appears as a decisive test bench for any quantum or emergent gravity scenario.
description: revtex4, 5 pages, 1 figures
The MUSECuBES surveys on the circumgalactic medium
Creators: name: Muzahid, Sowgat
Publisher: name: Zenodo
Year: 2019

description: The circumgalactic medium (CGM) is a dynamic, complex, multiphase, metal-enriched gas reservoir surrounding galaxies which harbors gas and metal masses comparable to those in galaxies themselves. Using a large quantity of spectral and imaging data obtained with MUSE & UVES on the VLT and ACS & COS on-board HST, we have started a major campaign on the CGM of high-z (z > 2.9) and low-z (z < 0.9) galaxies. With nearly 350 low-z galaxies and 100 high-z Lyman alpha emitters detected in a total of 24 MUSE cubes (16 for low-z and 8 for high-z), we have built two statistically significant and by far the largest samples for which CGM absorption line (e.g. Lya, SiII, CIV, and OVI) data are available up to an impact parameter of 300 kpc. Using these data we have constructed radial profile, covering fraction, and mean flux profiles for several crucial CGM absorption lines around low-z star-forming galaxies and high-z Lya emitters. Important results of our ongoing surveys (MUSE Quasar-field Blind Emitter Surveys; MUSEQuBES) will be presented in the talk.
A suite of 19F based relaxation dispersion experiments to assess biomolecular motions
Creators: name: Overbeck, Jan H.
name: Kremer, Werner
name: Sprangers, Remco
Publisher: name: Universität Regensburg
Year: 2020
Subjects: subject: Fluorine, Large complexes, Protein folding, Relaxation dispersion, Structural dynamics
subject: 570 Biowissenschaften, Biologie

description: Proteins and nucleic acids are highly dynamic bio-molecules that can populate a variety of conformational states. NMR relaxation dispersion (RD) methods are uniquely suited to quantify the associated kinetic and thermodynamic parameters. Here, we present a consistent suite of 19F-based CPMG, on-resonance R1ρ and off-resonance R1ρ RD experiments. We validate these experiments by studying the unfolding transition of a 7.5 kDa cold shock protein. Furthermore we show that the 19F RD experiments are applicable to very large molecular machines by quantifying dynamics in the 360 kDa half-proteasome. Our approach significantly extends the timescale of chemical exchange that can be studied with 19F RD, adds robustness to the extraction of exchange parameters and can determine the absolute chemical shifts of excited states. Importantly, due to the simplicity of 19F NMR spectra, it is possible to record complete datasets within hours on samples that are of very low costs. This makes the presented experiments ideally suited to complement static structural information from cryo-EM and X-ray crystallography with insights into functionally relevant motions.
Current Patterns and Orbital Magnetism in Mesoscopic dc Transport
Creators: name: Walz, Michael
name: Wilhelm, Jan
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: We present ab initio calculations of the local current density j(r) as it arises in dc-transport measurements. We discover pronounced patterns in the local current density, ring currents (“eddies”), that go along with orbital magnetism. Importantly, the magnitude of the ring currents can exceed the (average) transport current by orders of magnitude. We find associated magnetic fields that exhibit drastic fluctuations with field gradients reaching 1 T nm−1 V−1. The relevance of our observations for spin relaxation in systems with very weak spin-orbit interaction, such as organic semiconductors, is discussed. In such systems, spin relaxation induced by bias driven orbital magnetism competes with relaxation induced by the hyperfine interaction and appears to be of similar strength. We propose a NMR-type experiment in the presence of dc-current flow to observe the spatial fluctuations of the induced magnetic fields.
Supplementary Material for "Reef Elegy: An Auditory Display of Hawaii's 2019 Coral Bleaching Data"
Creators: name: Kalonaris, S.
Publisher: name: Zenodo
Year: 2023
Subjects: Supplementary Material

description: Supplementary material for the paper "Reef Elegy: An Auditory Display of Hawaii's 2019 Coral Bleaching Data".
 To appear in: Proceedings of the 28th International Conference on Auditory Display (ICAD 2023), Norrköping, Sweden. The supmat.zip file contains the following: |_audio
 | |_ad1.wav
 | |_ad2.wav
 | |_dl2.wav
 |
 |_data
 | |_responses.csv
 |
 |_README.md
Assembling the Milky Way bulge from globular clusters: Evidence from the double red clump
Creators: name: Lee, Young-Wook
name: Lim, Dongwook
name: Hong, Seungsoo
name: Chung, Chul
Publisher: name: Zenodo
Year: 2019

description: Two red clumps (RCs) observed in the color-magnitude diagram of the Milky Way bulge are widely accepted as evidence for a giant X-shaped structure originated from the bar instability. We suggested, however, a drastically different interpretation based on the He-enhanced multiple stellar population phenomenon as is observed in globular clusters (GCs). Here we report our discovery that the stars in the two RCs show a significant (> 5.3 sigma) difference in CN-band strength, in stark contrast to that expected in the X-shaped bulge scenario. Because CN-strong stars trace a population with enhanced N, Na, and He abundances that originated in GCs, this is direct evidence that the double RC is due to the multiple population phenomenon, and that a significant population of stars in the Milky Way bulge were assembled from disrupted proto-GCs as supported
by recent cosmological simulations. Our result also calls for the major revision of the 3D structure of the MilkyWay bulge.
The Bohman-Frieze Process Near Criticality
Creators: name: Kang, Mihyun
name: Perkins, Will
name: Spencer, Joel
Publisher: name: arXiv
Year: 2011
Subjects: subject: Combinatorics (math.CO)
subject: Probability (math.PR)
subject: FOS: Mathematics

description: The Erdős-Rényi process begins with an empty graph on n vertices and edges are added randomly one at a time to a graph. A classical result of Erdős and Rényi states that the Erdős-Rényi process undergoes a phase transition, which takes place when the number of edges reaches n/2 (we say at time 1) and a giant component emerges. Since this seminal work of Erdős and Rényi, various random graph models have been introduced and studied. In this paper we study the so-called Bohman-Frieze process, a simple modification of the Erdős-Rényi process. The Bohman-Frieze process begins with an empty graph on n vertices. At each step two random edges are present and if the first edge would join two isolated vertices, it is added to a graph; otherwise the second edge is added. We present several new results on the phase transition of the Bohman-Frieze random graph process. We show that the Bohman-Frieze process has a qualitatively similar phase transition to the Erdős-Rényi process in terms of the size and structure of the components near the critical point. We prove that all components at time t_c-\eps (that is, when the number of edges are (t_c-\eps) n/2) are trees or unicyclic components and that the largest component is of size Ω(\eps^{-2} \log n). Further, at t_c + \eps, all components apart from the giant component are trees or unicyclic and the size of the second-largest component is Θ(\eps^{-2} \log n). Each of these results corresponds to an analogous well-known result for the Erdős-Rényi process. Our methods include combinatorial arguments and a combination of the differential equation method for random processes with singularity analysis of generating functions which satisfy quasi-linear partial differential equations.
Density of States in Graphene with Vacancies: Midgap Power Law and Frozen Multifractality
Creators: name: Häfner, V.
name: Schindler, J.
name: Weik, N.
name: Mayer, T.
name: Balakrishnan, S.
name: Narayanan, R.
name: Bera, S.
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2014
Subjects: subject: 530 Physik

description: The density of states ϱ(E) of graphene is investigated numerically and within the self-consistent T-matrix approximation in the presence of vacancies within the tight binding model. The focus is on compensated disorder, where the concentration of vacancies nA and nB in both sublattices is the same. Formally, this model belongs to the chiral symmetry class BDI. The nonlinear sigma model predicts for BDI a Gade-type singularity ϱ(E)∼|E|−1exp[−|log(E)|−1/x]. Our numerical data are comparable to this result in a preasymptotic regime that gives way, however, at even lower energies to ϱ(E)∼E−1|log(E)|−˜x, 1≤˜x<2. We take this finding as evidence that, similar to the case of dirty d-wave superconductors, generic bipartite random hopping models may also exhibit unconventional (strong-coupling) fixed points for certain kinds of randomly placed scatterers if these are strong enough. Our research suggests that graphene with (effective) vacancy disorder is a physical representative of such systems.
Dynamics of Disks and Warps
Creators: name: Sellwood, J. A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: This chapter reviews theoretical work on the stellar dynamics of galaxy disks. All the known collective global instabilities are identified, and their mechanisms described in terms of local wave mechanics. A detailed discussion of warps and other bending waves is also given. The structure of bars in galaxies, and their effect on galaxy evolution, is now reasonably well understood, but there is still no convincing explanation for their origin and frequency. Spiral patterns have long presented a special challenge, and ideas and recent developments are reviewed. Other topics include scattering of disk stars and the survival of thin disks.
description: Chapter accepted to appear in Planets, Stars and Stellar Systems, vol 5, ed G. Gilmore. 32 pages, 17 figures. Includes minor corrections made in proofs. Uses emulateapj.sty
"Celebrated, not just endured”: Rethinking Winter Cities
Creators: Stout, Madeleine
Collins, Damian
Stadler, Sophie L.
Soans, Ranon
Sanborn, Emma
Summers, Robert J.
Publisher: name: University of Alberta Library
Year: 2018

A winter city is any urban centre that experiences a long, dark, cold, and/or snowy winter. The Winter Cities movement is a more precise concept, referring to cities taking an active role in becoming more appealing and functional in winter, primarily through physical interventions. The movement also has a social purpose, seeking to counter reclusion and “hibernation” in winter through greater use

of the public realm. The movement is increasingly influential in policy, as part of a broader shift towards promoting livability and sustainability in cities. However, it has yet to receive sustained scholarly attention. This article brings the Winter City movement more fully into the academic sphere, describing its emergence, purpose, and key attributes, while also examining it critically for silences. Drawing

on English‐ and German‐language publications, it places particular emphasis on the range of interventions and design approaches intended to promote greater use of outdoor public spaces, and an associated problematization of quasi‐public indoor environments.
QUANTUM ESTIMATION DISCRIMINATION IN CONTINUOUS VARIABLE AND FERMIONIC SYSTEMS
Creators: name: INVERNIZZI, CARMEN
Publisher: name: Universit� degli Studi di Milano
Year: 2011

description: In this PhD thesis we address the problem of characterizing quantum states and parameters of systems that are of particular interest for quantum technologies. In the first part we consider continuous variable systems and in particular Gaussian states; we address the estimation of quantities characterizing single-mode Gaussian states as the displacement and squeezing parameter and we study the improvement in the parameter estimation by introducing a Kerr nonlinearity. Moreover, we address the discrimination of noisy channels by means of Gaussian states as probe states considering two problems: the detection of a lossy channel against the alternative hypothesis of an ideal lossless channel and the discrimination of two Gaussian noisy channels. In the last part of the thesis, we consider the one dimensional quantum Ising model in a transverse magnetic field. We exploit the recent results about the geometric approach to quantum phase transitions to derive the optimal estimator of the coupling constant of the model at zero and finite temperature in both cases of few spins and in the thermodynamic limit. We also analyze the effects of temperature and the scaling properties of the estimator of the coupling constant. Finally, we consider the discrimination problem for two ground states or two thermal states of the model.