cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Revisiting special relativity: A natural algebraic alternative to Minkowski spacetime
Creators: name: Iannella, James M. Chappell Nicolangelo
name: Iqbal, Azhar
name: Abbott, Derek
Publisher: name: arXiv
Year: 2011
Subjects: subject: Classical Physics (physics.class-ph)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: Minkowski famously introduced the concept of a space-time continuum in 1908, merging the three dimensions of space with an imaginary time dimension $ i c t $, with the unit imaginary producing the correct spacetime distance $ x^2 - c^2 t^2 $, and the results of Einstein's then recently developed theory of special relativity, thus providing an explanation for Einstein's theory in terms of the structure of space and time. As an alternative to a planar Minkowski space-time of two space dimensions and one time dimension, we replace the unit imaginary $ i = \sqrt{-1} $, with the Clifford bivector $ ι= e_1 e_2 $ for the plane that also squares to minus one, but which can be included without the addition of an extra dimension, as it is an integral part of the real Cartesian plane with the orthonormal basis $ e_1 $ and $ e_2 $. We find that with this model of planar spacetime, using a two-dimensional Clifford multivector, the spacetime metric and the Lorentz transformations follow immediately as properties of the algebra. This also leads to momentum and energy being represented as components of a multivector and we give a new efficient derivation of Compton's scattering formula, and a simple formulation of Dirac's and Maxwell's equations. Based on the mathematical structure of the multivector, we produce a semi-classical model of massive particles, which can then be viewed as the origin of the Minkowski spacetime structure and thus a deeper explanation for relativistic effects. We also find a new perspective on the nature of time, which is now given a precise mathematical definition as the bivector of the plane.
description: 29 pages, 2 figures
Relaxation on critical percolation clusters, self-avoiding random walks, and the quantum Hall effect
Creators: name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 1997
Subjects: subject: 530 Physik

description: Large contour lines in a random landscape constitute a continuum percolation problem. We consider directed walks on these lines at the percolation threshold—self-avoiding by construction—and calculate the density correlation function using a Monte Carlo simulation. It has a scaling structure where all exponents are related to the fractal dimension dh=7/4 of extended contour lines. The corresponding scaling function, however, vanishes in the limit ω→0 with a power law giving rise to another a priori independent exponent ζ. Our data indicate a Cole-Cole structure for the quantity χ|IJ(ω) averaged over extended lines only, which implies ζ=2/7, η=0 and an anomaly in the small frequency asymptotics of the diffusion coefficient D(q,ω)∝ω−ζ/q2. This anomaly is reminiscent of a similar one in the quantum Hall effect, however, with negative ζqhe. We argue that the difference is due to the decay of phase resonances in the latter which come with a broad distribution of decay times.
description: PDF gehört eigentlich nicht zu diesem Eintrag. Beachten Sie den abweichenden Titel auf dem PDF!
Holographic principle and large scale structure in the universe
Creators: name: Mongan, T. R.
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Physics (physics.gen-ph)
subject: FOS: Physical sciences

description: A reasonable representation of large scale structure, in a closed universe so large it's nearly flat, can be developed by extending the holographic principle and assuming the bits of information describing the distribution of matter density in the universe remain in thermal equilibrium with the cosmic microwave background radiation. The analysis identifies three levels of self-similar large scale structure, corresponding to superclusters, galaxies, and star clusters, between today's observable universe and stellar systems. The self-similarity arises because, according to the virial theorem, the average gravitational potential energy per unit volume in each structural level is the same and depends only on the gravitational constant. The analysis indicates stellar systems first formed at z\approx62, consistent with the findings of Naoz et al, and self-similar large scale structures began to appear at redshift z\approx4. It outlines general features of development of self-similar large scale structures at redshift z<4. The analysis is consistent with observations for angular momentum of large scale structures as a function of mass, and average speed of substructures within large scale structures. The analysis also indicates relaxation times for star clusters are generally less than the age of the universe and relaxation times for more massive structures are greater than the age of the universe.
description: Further clarification of assumptions underlying the analysis
A characterization of quasi-rational polygons
Creators: name: Bedaride, Nicolas
Publisher: name: arXiv
Year: 2010
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 37E99

description: The aim of this paper is to study quasi-rational polygons related to the outer billiard. We compare different notions introduced, and make a synthesis of those.
description: 15 pages, 9 figures
How Riemannian Manifolds Converge: A Survey
Creators: name: Sormani, Christina
Publisher: name: arXiv
Year: 2010
Subjects: subject: Differential Geometry (math.DG)
subject: Metric Geometry (math.MG)
subject: FOS: Mathematics

description: This is an intuitive survey of extrinsic and intrinsic notions of convergence of manifolds complete with pictures of key examples and a discussion of the properties associated with each notion. We begin with a description of three extrinsic notions which have been applied to study sequences of submanifolds in Euclidean space: Hausdorff convergence of sets, flat convergence of integral currents, and weak convergence of varifolds. We next describe a variety of intrinsic notions of convergence which have been applied to study sequences of compact Riemannian manifolds: Gromov-Hausdorff convergence of metric spaces, convergence of metric measure spaces, Instrinsic Flat convergence of integral current spaces, and ultralimits of metric spaces. We close with a speculative section addressing possible notions of intrinsic varifold convergence, convergence of Lorentzian manifolds and area convergence.
description: Solicited survey article for a volume of articles in honor of Cheeger's 65th Birthday. Version 2 adds additional references concerning convergence of Lorentzian manifolds and updates citations
Bayesian inverse problems with Gaussian priors
Creators: name: Knapik, B. T.
name: van der Vaart, A. W.
name: van Zanten, J. H.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: The posterior distribution in a nonparametric inverse problem is shown to contract to the true parameter at a rate that depends on the smoothness of the parameter, and the smoothness and scale of the prior. Correct combinations of these characteristics lead to the minimax rate. The frequentist coverage of credible sets is shown to depend on the combination of prior and true parameter, with smoother priors leading to zero coverage and rougher priors to conservative coverage. In the latter case credible sets are of the correct order of magnitude. The results are numerically illustrated by the problem of recovering a function from observation of a noisy version of its primitive.
description: Published in at http://dx.doi.org/10.1214/11-AOS920 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org)
Siena College Research Institute Poll: Oct-Nov 2018 Siena New York Poll
Creators: name: Siena College Research Institute
Publisher: name: Roper Center for Public Opinion Research
Year: 2019

description: Direction of New York State (1); likely to vote in General Election (1); favorable/unfavorable opinion of person or institution (6); favorable/unfavorable opinion of people in public life (6); governor vote (1); New York State Comptroller vote (1); New York State Attorney General vote (1); preferred party in control of House of Representatives (1); preferred party in control of New York State Senate (1); labor union (1).
Superconductivity and quantized anomalous Hall in rhombohedral graphene
Creators: name: Choi, Youngjoon
name: Choi, Ysun
name: Valentini, Marco
name: Patterson, Caitlin L.
name: Holleis, Ludwig F. W.
name: Sheekey, Owen I.
name: Stoyanov, Hari
name: Cheng, Xiang
name: Taniguchi, Takashi
name: Watanabe, Kenji
name: Young, Andrea F.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Inducing superconducting correlations in chiral edge states is predicted to generate topologically protected zero energy modes with exotic quantum statistics. Experimental efforts to date have focused on engineering interfaces between superconducting materials typically amorphous metals and semiconducting quantum Hall or quantum anomalous Hall (QAH) systems. However, the interfacial disorder inherent in this approach can prevent the formation of isolated topological modes. An appealing alternative is to use low-density flat band materials where the ground state can be tuned between intrinsic superconducting and quantum anomalous Hall states using only the electric field effect. However, quantized transport and superconductivity have not been simultaneously achieved. Here, we show that rhombohedral tetralayer graphene aligned to a hexagonal boron nitride substrate hosts a quantized anomalous Hall state at superlattice filling $ν=-1$ as well as a superconducting state at $ν-3.5$ at zero magnetic field. Remarkably, gate voltage can also be used to actuate nonvolatile switching of the chirality in the quantum anomalous Hall state, allowing, in principle, arbitrarily reconfigurable networks of topological edge modes in locally gated devices. Thermodynamic compressibility measurements further reveal a topologically ordered fractional Chern insulator at $ν=2/3$-also stable at zero magnetic field-enabling proximity coupling between superconductivity and fractionally charged edge modes. Finally, we show that, as in rhombohedral bi- and trilayers, integrating a transition metal dichalcogenide layer to the heterostructure nucleates a new superconducting pocket, while leaving the topology of the $ν=-1$ quantum anomalous Hall state intact. Our results pave the way for a new generation of hybrid interfaces between superconductors and topological edge states in the low-disorder limit.
Density Expansion for Transport Coefficients: Long-Wavelength versus Fermi Surface Nonanalyticities
Creators: name: Evers, Ferdinand
name: Belitz, D.
name: Park, Wansoo
Publisher: name: Universität Regensburg
Year: 1997
Subjects: subject: 530 Physik

description: The expansion of the conductivity in 2- d quantum Lorentz models in terms of the scatterer density n is considered. We show that nonanalyticities in the density expansion due to scattering processes with small and large momentum transfers, respectively, have different functional forms. Some of the latter are not logarithmic, but rather of power-law nature, in sharp contrast to the 3- d case. In a 2- d model with point-like scatterers we find that the leading nonanalytic correction to the Boltzmann conductivity, apart from the frequency dependent weak-localization term, is of order n3/2.
Selective breeding of lodgepole pine and interior spruce generates growth gains but maintains phenotypic and genomic adaptation to climate
Creators: name: MacLachlan, Ian Robert
Publisher: name: University of British Columbia
Year: 2018

description: Climate change is disrupting local adaptation in temperate and boreal tree species. As climates shift, tree breeding zones are becoming dissociated from their historical climatic optima and no longer represent optimal seed deployment zones. Assisted gene flow (AGF) policies that match reforestation seedlots with future climates require accurate knowledge of genetic variation in climatically adaptive traits in breeding populations. In this thesis I evaluate the effects of selective breeding on climatic adaptation in the two most planted species in western Canada, lodgepole pine (Pinus contorta) and interior spruce (Picea glauca, P. engelmanii and their hybrids), to inform provincial AGF prescriptions. I compared natural stand seedlots (n = 105 pine, 154 spruce) with selectively bred seedlots (n = 20 pine, 18 spruce) from across Alberta and British Columbia in common garden experiments. Phenotypic variation among breeding zones was assessed for growth, phenology and cold hardiness in relation to climate. For both species, phenotypic differences between natural and selected seedlings in growth traits were substantial. Height gains resulted from increased growth rate and delayed growth cessation, but autumn cold hardiness was not substantially reduced. Seedlings were also genotyped for ~30,000 candidate single nucleotide polymorphisms for growth and adaptive traits. Selection for growth has shifted interior spruce hybrid ancestry in some breeding populations, but these effects are not consistent across zones. A genome-wide association study of pine identified many trait-associated SNPs. Positive effect allele frequencies among pine breeding zones were strongly associated with climatic variation. Selection has resulted in small increases in the frequency of positive effect alleles in breeding populations. Associations among cold hardiness phenotypes, genotypes and climate dominated signals of local adaptation were preserved in breeding populations. Selection, breeding and progeny testing combined have produced taller pine and spruce seedlings without compromising climatic adaptation. Strong phenotype-genotype-climate associations suggest AGF will be necessary to match breeding populations with future climates, but selectively bred and natural seedlots can be safely redeployed using the same AGF prescriptions. Multi-locus genomic profiles of adaptive traits associated with climate provide an accurate, rapid method to assess climatic adaptation that is independent from long-term provenance trials.
Introducing Big Team Science Initiatives (BTSIs) to Organizational Researchers
Creators: name: , Joshua.Cogswell@Nicholls.Edu
name: Cobb, Haley R.
name: Castille, Christopher Michael
name: Kreamer, Liana
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Social and Behavioral Sciences

description: The aim of this project is to systematically review the literature on big team science initiatives (BTSIs) with the purpose of introducing this methodology to the organizational sciences.
The Cosmological Impact of Luminous TeV Blazars I: Implications of Plasma Instabilities for the Intergalactic Magnetic Field and Extragalactic Gamma-Ray Background
Creators: name: Broderick, Avery E.
name: Chang, Philip
name: Pfrommer, Christoph
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Inverse-Compton cascades initiated by energetic gamma rays (E>100 GeV) enhance the GeV emission from bright, extragalactic TeV sources. The absence of this emission from bright TeV blazars has been used to constrain the intergalactic magnetic field (IGMF), and the stringent limits placed upon the unresolved extragalactic gamma-ray background (EGRB) by Fermi has been used to argue against a large number of such objects at high redshifts. However, these are predicated upon the assumption that inverse-Compton scattering is the primary energy-loss mechanism for the ultra-relativistic pairs produced by the annihilation of the energetic gamma rays on extragalactic background light photons. Here we show that for sufficiently bright TeV sources (isotropic-equivalent luminosities >10^{42} erg/s) plasma beam instabilities, specifically the "oblique" instability, present a plausible mechanism by which the energy of these pairs can be dissipated locally, heating the intergalactic medium. Since these instabilities typically grow on timescales short in comparison to the inverse-Compton cooling rate, they necessarily suppress the inverse-Compton cascades. As a consequence, this places a severe constraint upon efforts to limit the IGMF from the lack of a discernible GeV bump in TeV sources. Similarly, it considerably weakens the Fermi limits upon the evolution of blazar populations. Specifically, we construct a TeV-blazar luminosity function from those objects presently observed and find that it is very well described by the quasar luminosity function at z~0.1, shifted to lower luminosities and number densities, suggesting that both classes of sources are regulated by similar processes. Extending this relationship to higher redshifts, we show that the magnitude and shape of the EGRB above ~10 GeV is naturally reproduced with this particular example of a rapidly evolving TeV-blazar luminosity function.
description: 23 pages, 10 figures, update that matches the final version in the ApJ
Mapping the Landscape of EEG Hyperscanning Research on Interpersonal Coordination: A Systematic Review and Meta-Analysis.
Creators: name: Xinyu Wei
name: Hu, Na
name: Yang, Meng
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Psychology
subject: FOS: Psychology
subject: Biological Psychology
subject: Social Psychology
subject: Social and Behavioral Sciences
subject: Cognitive Psychology
subject: inter-brain synchrony
subject: interpersonal coordination
subject: EEG
subject: meta-analysis
subject: social interaction
subject: hyperscanning

description: Hyperscanning is a technique that allows the simultaneous measurement of the neural activity of two or more individuals as they interact (Montague et al., 2002). Due to the following unique advantages of electroencephalography (EEG) equipment, it has been widely used in the research of hyperscanning: (1) It has high temporal resolution and can capture moment-to-moment interactions (Koike et al., 2015) ; (2) It is easier to measure more than two heads at the same time (Czeszumski et al., 2020); (3) It is relatively low cost and mobile compared to other methods like fMRI or fNIRS (Koike et al., 2015). Inter-brain synchronization (IBS), of most concern in hyperscanning studies, is an indicator of changes in functional connectivity of regional neural activity in the brain between different individuals (Nozawa et al., 2019). In EEG-based hyperscanning studies, the commonly used indicators are calculated based on phase synchronization, such as phase-locing values (PLV) and phase-lag index (PLI). From the less cognitively demanding motor synchronization task and leader-follower task (Dumas et al., 2012; Konvalinka et al., 2014), to the more cognitively demanding musical cooperation task and prisoner's dilemma task (Jahng et al., 2017; Müller et al., 2013), researchers have observed associations between IBS and consistent behaviors or coordinated interpersonal activities. However, no systematic quantitative analysis of the outcomes of EEG hyerscanning has been performed thus far, and the findings on various EEG frequency bands in the research are quite varied. The present study aims to synthesize the available findings of EEG hyperscanning in interpersonal coordination and summarize how inter-brain phase synchronization will be characterized during interpersonal coordination (compared to non-interpersonal coordination). The meta-analyses will analyze how methodological factors such as experimental setup, dyads relationships, IBS indicators, and channel selection might have contributed to variations in the effect size. As one of the first meta-analyses in the field of EEG hyperscanning, the proposed study will seek to quantify the overall findings of the current study and make some practical recommendations for studies that have not yet been conducted.
Strong Magnetoresistance Induced by Long-Range Disorder
Creators: name: Mirlin, A. D.
name: Wilke, J.
name: Evers, Ferdinand
name: Polyakov, D. G.
name: Wölfle, P.
Publisher: name: Universität Regensburg
Year: 1999
Subjects: subject: 530 Physik

description: We calculate the semiclassical magnetoresistivity ρxx(B) of noninteracting fermions in two dimensions moving in a weak and smoothly varying random potential or random magnetic field. We demonstrate that in a broad range of magnetic fields the non-Markovian character of the transport leads to a strong positive magnetoresistance. The effect is especially pronounced in the case of a random magnetic field where ρxx(B) becomes parametrically much larger than its B=0 value.
Review of AdS/CFT Integrability, Chapter IV.3: N=6 Chern-Simons and Strings on AdS4xCP3
Creators: name: Klose, Thomas
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences
subject: 81T13, 81T30, 37K10

description: We review the duality and integrability of N=6 superconformal Chern-Simons theory in three dimensions and IIA superstring theory on the background AdS4xCP3. We introduce both of these models and describe how their degrees of freedom are mapped to excitations of a long-range integrable spin-chain. Finally, we discuss the properties of the Bethe equations, the S-matrix and the algebraic curve that are special to this correspondence and differ from the case of N=4 SYM theory and strings on AdS5xS5.
description: 22 pages, see also overview article arXiv:1012.3982, v2: references to other chapters updated, v3: references added, v4: brief discussion of giant magnons added, further minor changes, published version, v5: union of v3 and v4 because changes made in v3 were accidentally lost in v4
A cross-national comparison on the relations between risk perception, conspiracy beliefs, health behavior and public health policy support: Investigating the potential individual, societal and cultural moderators
Creators: name: Siu Kit Yeung
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Social and Behavioral Sciences

description: The pre-registration is for a secondary data analysis of several datasets. Please see the pre-registration document for the full list of datasets and the full list of authors.
Quasiclassical Negative Magnetoresistance of a 2D Electron Gas: Interplay of Strong Scatterers and Smooth Disorder
Creators: name: Mirlin, A. D.
name: Polyakov, D. G.
name: Evers, Ferdinand
name: Wölfle, P.
Publisher: name: Universität Regensburg
Year: 2001
Subjects: subject: 530 Physik

description: We study the quasiclassical magnetotransport of noninteracting fermions in two dimensions moving in a random array of strong scatterers (antidots, impurities, or defects) on the background of a smooth random potential. We demonstrate that the combination of the two types of disorder induces a novel mechanism leading to a strong negative magnetoresistance, followed by the saturation of the magnetoresistivity ρxx(B) at a value determined solely by the smooth disorder. Experimental relevance to the transport in semiconductor heterostructures is discussed.
Flavored Gauge-Mediation
Creators: name: Shadmi, Yael
name: Szabo, Peter Z.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The messengers of Gauge-Mediation Models can couple to standard-model matter fields through renormalizable superpotential couplings. These matter-messenger couplings generate generation-dependent sfermion masses and are therefore usually forbidden by discrete symmetries. However, the non-trivial structure of the standard-model Yukawa couplings hints at some underlying flavor theory, which would necessarily control the sizes of the matter-messenger couplings as well. Thus for example, if the doublet messenger and the Higgs have the same properties under the flavor theory, the resulting messenger-lepton couplings are parametrically of the same order as the lepton Yukawas, so that slepton mass-splittings are similar to those of minimally-flavor-violating models and therefore satisfy bounds on flavor-violation, with, however, slepton mixings that are potentially large. Assuming that fermion masses are explained by a flavor symmetry, we construct viable and natural models with messenger-lepton couplings controlled by the flavor symmetry. The resulting slepton spectra are unusual and interesting, with slepton mass-splittings and mixings that may be probed at the LHC. In particular, since the new contributions are typically negative, and since they are often larger for the first- and second-generation sleptons, some of these examples have the selectron or the smuon as the lightest slepton, with mass splittings of a few to tens of GeV.
description: 16 pages v2: Explicit expressions (which are not needed in the analysis) for the pure Yukawa contributions removed. There was an error in some of these expressions in v1. References added
Social Dance and Movement for Mental Health: A Scoping Review
Creators: name: Buckman, Joshua Eusty Jonathan
name: Murphy, Susannah
name: Harmer, Catherine
name: Delattre, Brennan
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Recreational Therapy
subject: Social and Behavioral Sciences
subject: Social Psychology
subject: Rehabilitation and Therapy
subject: Psychology
subject: FOS: Psychology
subject: Somatic Bodywork and Related Therapeutic Practices
subject: Art Therapy
subject: Other Mental and Social Health
subject: Medicine and Health Sciences
subject: Mental and Social Health
subject: social dance
subject: social movement
subject: dance
subject: low mood
subject: depression

description: The proposed review will focus on research that investigates the mental health and mood effects of social dance or social movement in healthy and clinical populations.
KMOS in the Galactic Center
Creators: name: Feldmeier-Krause, Anja
Publisher: name: Zenodo
Year: 2019

description: The Galactic centre is a unique target to study the central region of a galaxy. At a distance of only 8 kpc from Earth, we find the main components of galaxy nuclei: a supermassive black hole, billions of stars, and a large amount of interstellar gas and dust in the central molecular zone, with ongoing star formation.  One of the challenges in observing the Galactic centre is its large extent on the sky, over about one degree in longitude. Another challenge is the high interstellar extinction, about 30 mag in the Visual.  However, extinction decreases with wavelength, down to 2.7 mag in the near-infrared K-band. KMOS combines two key properties that are necessary to efficiently observe the Galactic centre:  It is a near-infrared instrument with a large field-of-view. It was used in the Galactic centre both in mosaic mode, as well as in MOS mode.  I will present some of the studies that used KMOS observations of the Galactic centre. The flexibility of KMOS allows observations with a broad scope of scientific goals: to study stellar populations of the nuclear star cluster,  a survey of young stellar objects, HII regions, and stellar kinematics of the extended Galactic centre region.
Classical analysis of a network model of quantum Hall systems
Creators: name: Wysokiński, K. I.
name: Evers, Ferdinand
name: Brenig, W.
Publisher: name: Universität Regensburg
Year: 1996
Subjects: subject: 530 Physik

description: A version of a network model of quantum Hall systems is studied classically. We assume that randomness inherent in the problem enters the model via random heights of saddle points only. We use ideas from classical percolation theory to calculate numerically the fractal dimension df, the correlation length exponent ν, the diffusion coefficient D, the corresponding exponent k, and other parameters of interest. The width of the longitudinal conductivity peak scales with the classical localization length exponent ν. © 1996 The American Physical Society.
Harnessing the reactivity of late transition metals for the making and breaking of C-X (X = O, S, N) bonds
Creators: name: Addison, Desnoyer N.
Publisher: name: University of British Columbia
Year: 2017

description: This thesis explores the fundamental reactivity of π-complexes of rhodium and nickel, their reactivity to form well-defined 2-metallaoxetanes, as well as subsequent functionalization chemistry of these rare metallacycles. More generally, we also examine C-O and C-S bond cleavage processes. In Chapter 1, we discuss the history of 2-metallaoxetanes, as well as outline some of the fundamental organometallic chemistry of group 10 transition metal complexes. In Chapter 2, the chemistry of a well-defined 2-rhodaoxetane with unsaturated electrophiles is explored. In all cases, insertion into the Rh-O bond is observed. When electron-deficient alkynes are used as substrates, rhodadihydropyrans are formed. Reactivity studies have found these complexes to be robust. In contrast, when aldehydes are used, the product rhodaacetals are much less stable. Curiously, the aldehyde insertions were found to be reversible. Chapter 3 outlines the reactivity of low-valent nickel complexes with three-membered oxacycles. When epoxides were used, isomerization to the corresponding aldehyde was observed as the primary reaction pathway. Experiments with tetrasubstituted epoxides indicate that these reactions occur via 2-nickela(II)oxetane intermediates. Further, catalytic functionalization was achieved using HBpin or B2pin2. When using oxaziridines as the three-membered heterocycle, N-O oxidative addition was found to rapidly generate oxazanickela(II)cyclobutanes. Fragmentation of these metallacycles resulted in the formation of a mixture of imine and aldehyde products. Chapter 4 discusses the synthesis, mechanism of formation and reactivity of a family of well-defined 2-nickela(II)oxetanes. These nickelacycles are formed with retention of configuration, which had not been observed previously. Computational calculations were performed, which support an unexpected bimetallic mechanism of oxidative addition that would allow for the observed stereochemistry. Reactivity studies indicate that the nickelaoxetanes are susceptible to protonolysis, insertion and oxidatively-induced reductive elimination reactions. Chapter 5 describes the chemistry of nickel with esters and thioesters. For thioesters, Cacyl-S bond cleavage followed by decarbonylation was observed to form methyl-thiolate complexes of nickel(II). In contrast, aryl esters were found to undergo Caryl-O oxidative addition, producing aryl-acetate nickel(II) complexes. Both of these classes of compounds were found to be competent in stoichiometric Suzuki-type cross-coupling reactions, but attempts to render the reactions catalytic have so far been unsuccessful.
MIKiS: the ESO-VLT Multi-Instrument Kinematic Survey of Galactic Globular Clusters
Creators: name: Ferraro, Francesco R.
Publisher: name: Zenodo
Year: 2019

description: Here I present first results from the ESO-VLT Multi-Instrument Kinematic Survey of Galactic Globular Clusters, a survey specifically designed to provide line-of-sight velocities of hundreds individual stars over the entire radial extension of a selected sample of globulars.  The survey  allows the first kinematical exploration of the innermost regions of high- density clusters. Moreover, once combined with proper motion measurements (from multi-epoch HST observations and from Gaia), it will provide the full 3D view of the velocity space of each system.  Long lasting open issues such as the accurate shape of the velocity dispersion profiles, the existence of systemic rotation and orbital anisotropy (and thus the level of relaxation), and the controversial presence of intermediate-mass black holes in star clusters will be finally addressed, with crucial impact on our understanding of the formation and evolutionary processes of globular clusters and their interactions with the Galactic tidal field.
Dimensionality dependence of the wave-function statistics at the Anderson transition
Creators: name: Mildenberger, A.
name: Evers, Ferdinand
name: Mirlin, A. D.
Publisher: name: Universität Regensburg
Year: 2002
Subjects: subject: 530 Physik

description: The statistics of critical wave functions at the Anderson transition in three and four dimensions are studied numerically. The distribution of the inverse participation ratios (IPRs) Pq is shown to acquire a scale-invariant form in the limit of large system size. Multifractality spectra governing the scaling of the ensemble-averaged IPRs are determined. Conjectures concerning the IPR statistics and the multifractality at the Anderson transition in a high spatial dimensionality are formulated.
Density of quasiparticle states for a two-dimensional disordered system: Metallic, insulating, and critical behavior in the class-D thermal quantum Hall effect
Creators: name: Mildenberger, A.
name: Evers, Ferdinand
name: Mirlin, A. D.
name: Chalker, J. T.
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik

description: We investigate numerically the quasiparticle density of states ϱ(E) for a two-dimensional, disordered superconductor in which both time-reversal and spin-rotation symmetries are broken. As a generic single-particle description of this class of systems (symmetry class D), we use the Cho-Fisher version of the network model. This has three phases: a thermal insulator, a thermal metal, and a quantized thermal Hall conductor. In the thermal metal, we find a logarithmic divergence in ϱ(E) as E→0, as predicted from sigma model calculations. Finite-size effects lead to superimposed oscillations, as expected from random-matrix theory. In the thermal insulator and quantized thermal Hall conductor, we find that ϱ(E) is finite at E=0. At the plateau transition between these phases, ϱ(E) decreases toward zero as ∣E∣ is reduced, in line with the result ϱ(E)∼∣E∣ln(1∕∣E∣) derived from calculations for Dirac fermions with random mass.
Benchmarking the performance of a high-Q cavity qudit using random unitaries
Creators: name: Bornman, Nicholas
name: Roy, Tanay
name: Job, Joshua A.
name: Anand, Namit
name: Perdue, Gabriel N.
name: Zorzetti, Silvia
name: Alam, M. Sohaib
Publisher: name: arXiv
Year: 2024
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: High-coherence cavity resonators are excellent resources for encoding quantum information in higher-dimensional Hilbert spaces, moving beyond traditional qubit-based platforms. A natural strategy is to use the Fock basis to encode information in qudits. One can perform quantum operations on the cavity mode qudit by coupling the system to a non-linear ancillary transmon qubit. However, the performance of the cavity-transmon device is limited by the noisy transmons. It is, therefore, important to develop practical benchmarking tools for these qudit systems in an algorithm-agnostic manner. We gauge the performance of these qudit platforms using sampling tests such as the Heavy Output Generation (HOG) test as well as the linear Cross-Entropy Benchmark (XEB), by way of simulations of such a system subject to realistic dominant noise channels. We use selective number-dependent arbitrary phase and unconditional displacement gates as our universal gateset. Our results show that contemporary transmons comfortably enable controlling a few tens of Fock levels of a cavity mode. This framework allows benchmarking even higher dimensional qudits as those become accessible with improved transmons.
description: 36 pages, 8 figures
The Cosmological Impact of Luminous TeV Blazars II: Rewriting the Thermal History of the Intergalactic Medium
Creators: name: Chang, Philip
name: Broderick, Avery E.
name: Pfrommer, Christoph
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The Universe is opaque to extragalactic very high-energy gamma rays (VHEGRs, E>100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultra-relativistic pairs are assumed to lose energy through inverse Compton scattering of CMB photons. In Broderick et al. (2011, Paper I of this three paper series), we argued that instead powerful plasma instabilities in the ultra-relativistic pair beam dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating upon the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate and correct for the pointed nature of VHEGR observations using Fermi observations of high and intermediate peaked BL Lacs. Because the local extragalactic VHEGR flux is dominated by TeV blazars, we tie the TeV blazar luminosity density to the quasar luminosity density, and produce a VHEGR heating rate as a function of redshift. This heating is relatively homogeneous for z
description: 23 pages, 14 figures, update that matches the final version in the ApJ
Superalgebra Realization of the 3-algebras in N=6, 8 Chern-Simons-matter Theories
Creators: name: Chen, Fa-Min
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We use superalgebras to realize the 3-algebras used to construct N=6, 8 Chern-Simons-matter (CSM) theories. We demonstrate that the superalgebra realization of the 3-algebras provides a unified framework for classifying the gauge groups of the N \geq 5 theories based on 3-algebras. Using this realization, we rederive the ordinary Lie algebra construction of the general N=6 CSM theory from its 3-algebra counterpart, and reproduce all known examples as well. In particular, we explicitly construct the Nambu 3-bracket in terms of a double graded commutator of PSU(2|2). The N = 8 theory of Bagger, Lambert and Gustavsson (BLG) with SO(4) gauge group is constructed by using several different ways. A quantization scheme for the 3-brackets is proposed by promoting the double graded commutators as quantum mechanical double graded commutators.
description: 29 pages, minor changes, published in JMP
Kinematics of low mass galaxies at cosmic noon with KLENS and KLASS
Creators: name: Girard, Marianne
Publisher: name: Zenodo
Year: 2019

description: The KMOS Lensing Survey (KLENS) and the KMOS Lens-Amplified Spectroscopic Survey (KLASS) are exploiting gravitational lensing to study kinematics of star-forming galaxies (SFGs) between a redshift of 0.6 and 3.5 with low masses (median log(M_star/M_sun) of 9.3) and/or low star formation rates (median SFR of 6 M/yr). These SFGs are particularly interesting since they are Milky Way progenitors at high redshift. The determination of the kinematic properties of these normal SFGs around the peak of the cosmic star formation rate density, would also allow us to determine how they differ from massive galaxies which have been analyzed so far.  Using KLENS and the new observations from KLASS, we test the rotation dominated fraction dependance as a function of stellar mass, star formation rate, and offset from the main sequence.  We investigate the evolution of the intrinsic velocity dispersion as a function of the redshift and stellar mass. We also study the star-forming clumps of these galaxies using HST rest-frame UV images to better understand the origin of the high intrinsic velocity dispersion observed at high redshift.
Signatures of AGN feedback in synthetic nebular emission lines of simulated, massive galaxies
Creators: name: Hirschmann, Michaela
Publisher: name: Zenodo
Year: 2019

description: We present a detailed analysis of the effect of AGN feedback on integrated and spatially resolved synthetic optical emission lines for simulated massive galaxies at different cosmic epochs. The theoretical emission lines are derived from coupling "new-generation" nebular models, accounting for photo-ionisation due to young stars, AGN and post-AGB stellar populations, to new sets of cosmological zoom-in simulations of massive galaxies, run with and without AGN feedback. Investigating the evolution of BPT diagrams, we demonstrate that AGN feedback is crucial to reproduce the observed decrease in [OIII]/Hb  from high to low redshift, via regulating the SF in massive galaxies. We additionally highlight the multifaceted imprint of AGN feedback on projected 2D emission line maps, such as (i) central Ha deficiencies and reduced extent of Ha emission, (ii) flattened [NII]/Ha gradients, and (iii) extended low ionisation emission — overall, more consistent with recent observations. Finally, prospects will be given, to what extent our novel interface between simulations and observations will contribute to the interpretation of up-coming high-z, high-quality spectroscopic data, e.g. from JWST.
Organometallic Benzene-Vanadium Wire: A One-Dimensional Half-Metallic Ferromagnet
Creators: name: Maslyuk, Volodymyr V.
name: Bagrets, Alexei
name: Meded, Velimir
name: Arnold, Andreas
name: Evers, Ferdinand
name: Brandbyge, Mads
name: Bredow, Thomas
name: Mertig, Ingrid
Publisher: name: Universität Regensburg
Year: 2006
Subjects: subject: 530 Physik

description: Using density functional theory we perform theoretical investigations of the electronic properties of a freestanding one-dimensional organometallic vanadium-benzene wire. This system represents the limiting case of multidecker Vn(C6H6)n+1 clusters which can be synthesized with established methods. We predict that the ground state of the wire is a 100% spin-polarized ferromagnet (half-metal). Its density of states is metallic at the Fermi energy for the minority electrons and shows a semiconductor gap for the majority electrons. We find that the half-metallic behavior is conserved up to 12% longitudinal elongation of the wire. Ab initio electron transport calculations reveal that finite size vanadium-benzene clusters coupled to ferromagnetic Ni or Co electrodes will work as nearly perfect spin filters.
Revealing the driving mechanisms of AGN activity and star formation in cosmological simulations
Creators: name: Steinborn, Lisa K.
Publisher: name: Zenodo
Year: 2019

description: Scaling relations between supermassive black holes and the stellar bulges of their host galaxies reveal a tight correlation between BH growth and star formation (SF).  Using cosmological hydrodynamic simulations from the Magneticum Pathfinder simulation set as well as cosmological zoom-in simulations, I will demostrate that this coevolution can be understood as a balance between AGN feedback and gas cooling and is thus very sensitive to the underlying sub-grid models used to mimic the physics of AGN and SF within cosmological simulations. This implies not only that the coevolution is self-regulated, depending on these models, but also that AGN and SF activity must be closely correlated. Indeed, our simulated AGN light-curves and the SF history follow very similar trends. However, AGN act on much shorter time scales than SF and the two can be shifted against each other in time. In agreement with recent observations, detailed AGN light- curves also reveal that most simulated AGN are not driven by galaxy mergers, but by smooth or clumpy gas accretion, or by internal processes. This strongly challenges the traditional view, in which AGN and starbursts are mainly driven by mergers.
Conductance of molecular wires and transport calculations based on density-functional theory
Creators: name: Evers, Ferdinand
name: Weigend, F.
name: Koentopp, M.
Publisher: name: Universität Regensburg
Year: 2004
Subjects: subject: 530 Physik

description: The experimental value for the zero bias conductance of organic molecules coupled by thiol-groups to gold electrodes tends to be much smaller than the theoretical result based on density functional theory (DFT) calculations, often by orders of magnitude. To address this puzzle we have analyzed the regime within which the approximations made in these calculations are valid. Our results suggest that a standard step in DFT based transport calculations, namely approximating the exchange-correlation potential in quasistatic nonequilibrium by its standard equilibrium expression, is not justified at weak coupling. We propose, that the breakdown of this approximation is the most important source for overestimating the width of the experimentally observed conductance peak and therefore also of the zero bias conductance. We present a numerical study on the conductance of an organic molecule that has recently been studied in experiments that fully agrees with this conclusion.
A billion-source atlas of the inner Milky Way
Creators: name: Alonso-Garcia, Javier
Publisher: name: Zenodo
Year: 2019

description: Our knowledge of the innermost Milky Way is seriously hampered by the dust and gas present at low latitude lines of sight. The VVV and the VVV-X surveys can beat these difficulties by observing the Galactic Bulge and inner Disk at near-infrared wavelengths were extinction is highly diminished. In addition, the high resolution of the VVV/VVV-X images and the use of PF-fitting techniques allow us to deal with the elevated crowding at these low-latitude regions. In this contribution, I will present the billion-source catalog we have generated for these regions. I will show the near-infrared CMDs that we have built, and which allow for a more precise definition and a better characterization of the different stellar populations located in the Galactic Plane. I will also talk about the non-canonical reddening law towards these low latitude lines-of-sight, and how we can use the information provided by our color-magnitude diagrams to constrain it.
Metamaterial-based model of the Alcubierre warp drive
Creators: name: Smolyaninov, Igor I.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Electromagnetic metamaterials are capable of emulating many exotic space-time geometries, such as black holes, rotating cosmic strings, and the big bang singularity. Here we present a metamaterial-based model of the Alcubierre warp drive, and study its limitations due to available range of material parameters. It appears that the material parameter range introduces strong limitations on the achievable "warp speed", so that ordinary magnetoelectric materials cannot be used. On the other hand, newly developed "perfect" bi-anisotropic non-reciprocal magnetoelectric metamaterials should be capable of emulating the physics of warp drive gradually accelerating up to 1/4c.
description: 15 pages, 3 figures, this version is accepted for publication in Phys.Rev.B