cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Position-Based Quantum Cryptography: Impossibility and Constructions
Creators: name: Buhrman, Harry
name: Chandran, Nishanth
name: Fehr, Serge
name: Gelles, Ran
name: Goyal, Vipul
name: Ostrovsky, Rafail
name: Schaffner, Christian
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: Cryptography and Security (cs.CR)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: In this work, we study position-based cryptography in the quantum setting. The aim is to use the geographical position of a party as its only credential. On the negative side, we show that if adversaries are allowed to share an arbitrarily large entangled quantum state, no secure position-verification is possible at all. We show a distributed protocol for computing any unitary operation on a state shared between the different users, using local operations and one round of classical communication. Using this surprising result, we break any position-verification scheme of a very general form. On the positive side, we show that if adversaries do not share any entangled quantum state but can compute arbitrary quantum operations, secure position-verification is achievable. Jointly, these results suggest the interesting question whether secure position-verification is possible in case of a bounded amount of entanglement. Our positive result can be interpreted as resolving this question in the simplest case, where the bound is set to zero. In models where secure positioning is achievable, it has a number of interesting applications. For example, it enables secure communication over an insecure channel without having any pre-shared key, with the guarantee that only a party at a specific location can learn the content of the conversation. More generally, we show that in settings where secure position-verification is achievable, other position-based cryptographic schemes are possible as well, such as secure position-based authentication and position-based key agreement.
description: 27 pages, 5 figures. v4: improved proofs for the impossibility theorem and for the instantaneous computation theorem
The KLEVER survey: spatially resolved gas excitation properties and metallicity in high-z galaxies
Creators: name: Curti, Mirko
Publisher: name: Zenodo
Year: 2019

description: We will present KLEVER, an ESO Large Programme aimed at investigating dynamics, gas excitation properties and chemical abundances in high redshift galaxies, by means of near-IR spatially resolved spectroscopy. Exploiting KMOS observations in the J,H and K bands we aim to map multiple optical rest-frame nebular diagnostics in a sample of ~120 galaxies between 1.2 < z < 2.5, allowing a detailed characterisation of the properties and excitation mechanism of the ISM in these objects on a spatially resolved basis. We will focus on the analysis of the already completed observations in some of the CLASH and Frontier Fields clusters. By studying spatially resolved versions of diagnostic diagrams (such as BPTs) we discuss the nature of the physical processes responsible for the observed offset of high-z galaxies in these diagrams compared to local ones. We also infer chemical abundances from our set of diagnostic emission lines, exploiting a variety of different calibrations. This allows to study spatially resolved metallicity maps and assess shape, properties and evolution of metallicity gradients. Finally, issues related to data reduction and analysis of KLEVER data are also discussed.
Multifractality at the Quantum Hall Transition: Beyond the Parabolic Paradigm
Creators: name: Evers, Ferdinand
name: Mildenberger, A.
name: Mirlin, A. D.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: 530 Physik

description: We present an ultrahigh-precision numerical study of the spectrum of multifractal exponents Δq characterizing anomalous scaling of wave function moments ⟨|ψ|2q⟩ at the quantum Hall transition. The result reads Δq=2q(1−q)[b0+b1(q−1/2)2+⋯], with b0=0.1291±0.0002 and b1=0.0029±0.0003. The central finding is that the spectrum is not exactly parabolic: b1≠0. This rules out a class of theories of the Wess-Zumino-Witten type proposed recently as possible conformal field theories of the quantum Hall critical point.
Spin Texture in a Cold Exciton Gas
Creators: name: High, A. A.
name: Hammack, A. T.
name: Leonard, J. R.
name: Yang, Sen
name: Butov, L. V.
name: Ostatnicky, T.
name: Kavokin, A. V.
name: Gossard, A. C.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We report on the observation of a spin texture in a cold exciton gas in a GaAs/AlGaAs coupled quantum well structure. The spin texture is observed around the exciton rings. The observed phenomena include: a ring of linear polarization, a vortex of linear polarization with polarization perpendicular to the radial direction, an anisotropy in the exciton flux, a skew of the exciton fluxes in orthogonal circular polarizations and a corresponding four-leaf pattern of circular polarization, a periodic spin texture, and extended exciton coherence in the region of the polarization vortex. The data indicate a transport regime where the spin polarization is locked to the direction of particle propagation and scattering is suppressed.
description: version 2 contains updated supplementary material
The Individual Green-Washing Effect in E-Mobility: Emotional Evaluations of Electric and Gasoline Cars
Creators: name: Jansen, Petra
name: Schroter, Franziska Anna
name: Hofmann, Philipp
name: Rundberg, Ronja
Publisher: name: Universität Regensburg
Year: 2021

description: In this study, the affective explicit and implicit attitudes toward electric and gasoline cars are investigated. One hundred sixty-five participants (103 cisgender women, 62 cisgender men) completed an explicit and implicit affective rating task toward pictures of electric and gasoline cars, measurements of sustainability, future and past behaviors, and mindfulness. The results showed a positive emotional attitude for the electric cars compared with the gasoline cars only for the explicit rating but not for the implicit one. Furthermore, factors that correlated to the attitudes were investigated: explicit ratings in car owners correlated with age, degree, sustainability in general, and the expressed intention to purchase an electric car in the future. Implicit attitudes in car owners correlated with the overall score of mindfulness and the dimension of “non-reactivity.” For the non-car owners, explicit attitudes correlated with the expressed intention to purchase an electric car in the future and the mindfulness dimension of “describing”. In this group, the implicit attitude correlated negatively with the mindfulness intention of acting with awareness. This indicates that several different factors should be considered in the development of promotion campaigns for the advantage of sustainable mobility behavior.
A Matrix Hyperbolic Cosine Algorithm and Applications
Creators: name: Zouzias, Anastasios
Publisher: name: arXiv
Year: 2011
Subjects: subject: Data Structures and Algorithms (cs.DS)
subject: Discrete Mathematics (cs.DM)
subject: FOS: Computer and information sciences

description: In this paper, we generalize Spencer's hyperbolic cosine algorithm to the matrix-valued setting. We apply the proposed algorithm to several problems by analyzing its computational efficiency under two special cases of matrices; one in which the matrices have a group structure and an other in which they have rank-one. As an application of the former case, we present a deterministic algorithm that, given the multiplication table of a finite group of size $n$, it constructs an expanding Cayley graph of logarithmic degree in near-optimal O(n^2 log^3 n) time. For the latter case, we present a fast deterministic algorithm for spectral sparsification of positive semi-definite matrices, which implies an improved deterministic algorithm for spectral graph sparsification of dense graphs. In addition, we give an elementary connection between spectral sparsification of positive semi-definite matrices and element-wise matrix sparsification. As a consequence, we obtain improved element-wise sparsification algorithms for diagonally dominant-like matrices.
description: 16 pages, simplified proof and corrected acknowledging of prior work in (current) Section 4
Supplementary document for Accelerating Brillouin fiber sensing via destructive-interference-enabled precise raw data acquisition and nonredundant image denoising - 7360284.pdf
Creators: name: Li, Zonglei
name: Zhou, Yin
name: Hu, Jianqi
name: Yao, Jianping
name: Yan, Lianshan
Publisher: name: Optica Publishing Group
Year: 2025
Subjects: Uncategorized

description: Supplemental theoretical analysis and experimental results
Toward a new understanding of disk galaxy formation
Creators: name: Kassin, Susan
Publisher: name: Zenodo
Year: 2019

description: One of the most important open issues in astronomy is the assembly of galactic disks.  Over the last decade this has been addressed with large surveys of the internal kinematics of galaxies spanning the last 10 billion years of the universe, many led by KMOS.  I will discuss recent results from the field that show the kinematic assembly of disk galaxies since a redshift of 2, including recent deep 10-30 hour observations by my group with the DEIMOS spectrograph on Keck.  These results strongly challenge traditional analytic models of galaxy formation and provide an important benchmark for simulations.  Furthermore, I will discuss our plans for extending KMOS results to higher redshifts with future instruments such as the JWST's NIRSpec IFU and the E-ELT's MOSAIC and HARMONI IFUs.  From mock JWST and E-ELT observations of simulated galaxies, we are learning that interpreting these observations of galaxies in the early universe, when merging is frequent, is not necessarily straightforward.
Density Propagator for Many-Body Localization: Finite-Size Effects, Transient Subdiffusion, and Exponential Decay
Creators: name: Bera, Soumya
name: De Tomasi, Giuseppe
name: Weiner, Felix
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2017
Subjects: subject: 530 Physik

description: We investigate charge relaxation in quantum wires of spinless disordered fermions (t−V model). Our observable is the time-dependent density propagator Πϵ(x,t), calculated in windows of different energy density ϵ of the many-body Hamiltonian and at different disorder strengths W, not exceeding the critical value Wc. The width Δxϵ(t) of Πϵ(x,t) exhibits a behavior dlnΔxϵ(t)/dlnt=βϵ(t), where the exponent function βϵ(t)≲1/2 is seen to depend strongly on L at all investigated parameter combinations. (i) We confirm the existence of a region in phase space that exhibits subdiffusive dynamics in the sense that βϵ(t)<1/2 in a large window of times. However, subdiffusion might possibly be transient, only, finally giving way to a conventional diffusive behavior with βϵ=1/2. (ii) We cannot confirm the existence of many-body mobility edges even in regions of the phase diagram that have been reported to be deep in the delocalized phase. (iii) (Transient) subdiffusion 0
The Role of Entrepreneurship in Economic Development and Social Change
Creators: name: Shermila Madushani, Wickramarathne
Publisher: name: Zenodo
Year: 2025

description: This research paper examines the concept of impact entrepreneurship and its role in fostering both economic development and social change. It traces the evolution of entrepreneurship from traditional profit-driven models to modern approaches that integrate social and environmental objectives. Specifically, the paper focuses on the emergence and growth of impact entrepreneurship, which seeks to generate positive outcomes across financial, social, and environmental dimensions.

The study begins with a review of the impact entrepreneurship concept, differentiating it from traditional business models that prioritize profit maximization. It explores how impact entrepreneurs address systemic global challenges such as poverty, inequality, climate change, and lack of access to basic services like education and healthcare. Through detailed analysis, the paper emphasizes the dual objectives of impact entrepreneurship: ensuring financial sustainability while creating measurable, lasting societal and environmental impacts.

Furthermore, the paper investigates the historical roots of impact entrepreneurship, tracing its origins to the social entrepreneurship movement in the 1980s and 1990s. Key milestones such as the development of microfinance by the Grameen Bank and the rise of impact investing are highlighted to demonstrate how the field has matured and gained traction globally.

The study identifies and discusses several characteristics of impact entrepreneurs, including their mission-driven nature, innovative mindset, long-term vision, scalability, and collaborative tendencies. These qualities enable impact entrepreneurs to develop sustainable business models that not only provide economic value but also address critical social and environmental issues.

In addition, the paper explores the role of impact entrepreneurship in economic development, focusing on its contributions to job creation, poverty alleviation, and the expansion of access to essential services. It also examines the social impact of such ventures, with a focus on areas such as education, healthcare, gender equality, and community empowerment.

Despite its potential, the paper also outlines the challenges faced by impact entrepreneurs, including limited access to capital, difficulties in measuring social impact, balancing financial and social goals, and navigating regulatory barriers. The research concludes by highlighting the importance of continued support from governments, investors, and other stakeholders to scale and sustain impact entrepreneurship, ultimately contributing to a more inclusive, sustainable, and equitable global economy.
Ages and abundances of microlensed bulge stars
Creators: name: Bensby, Thomas
Publisher: name: Zenodo
Year: 2019

description: Dwarf stars in the bulge are generally too faint too observe with high-resolution spectrographs under normal observing conditions  However, during gravitational microlensing events they may brighten by factors of several hundreds. Since 2009 we have conducted an observing campaign, through a target-of-opportunity program with UVES at VLT, to catch these elusive events. The results have dramatically changed the picture of the Milky Way bulge and I will in this talk present the most recent results about the age and abundance structure of the Milky Way bulge based on microlensed dwarf and subgiant stars.
Mock weak lensing analysis of simulated galaxy clusters: bias and scatter in mass and concentration
Creators: name: Bahé, Yannick M.
name: McCarthy, Ian G.
name: King, Lindsay J.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: (Abridged) We quantify the bias and scatter in galaxy cluster masses and concentrations derived from an idealised mock weak gravitational lensing (WL) survey, and their effect on the cluster mass-concentration relation. For this, we simulate WL distortions on a population of background galaxies due to a large (~3000) sample of galaxy cluster haloes extracted from the Millennium Simulation at z~0.2. This study takes into account the influence of shape noise, cluster substructure and asphericity as well as correlated large-scale structure, but not uncorrelated large-scale structure along the line of sight and observational effects. We find a small, but non-negligble, negative median bias in both mass and concentration at a level of ~5%, the exact value depending both on cluster mass and radial survey range. Both the mass and concentration derived from WL show considerable scatter about their true values. This scatter has, even for the highest mass clusters of M200 > 10^14.8 M_sun, a level of ~30% and ~20% for concentration and mass respectively and increases strongly with decreasing cluster mass. For a typical survey analysing 30 galaxies per arcmin^2 over a radial range from 30" to 15' from the cluster centre, the derived M200-c relation has a slope and normalisation too low compared to the underlying true (3D) relation by ~40% and ~15% respectively. The scatter and bias in mass are shown to reflect a departure at large radii of the true WL shear/matter distribution of the simulated clusters from the NFW profile adopted in modelling the mock observations. Orientation of the triaxial cluster haloes dominates the concentration scatter (except at low masses, where galaxy shape noise becomes dominant), while the bias in c is mostly due to substructure within the virial radius.
description: 18 pages, 12 figures. Minor changes to match final published paper. High-resolution figures available at http://www.ast.cam.ac.uk/~ybahe/Lensing.pdf
Spectrum of non-Hermitian heavy tailed random matrices
Creators: name: Bordenave, Charles
name: Caputo, Pietro
name: Chafai, Djalil
Publisher: name: arXiv
Year: 2010
Subjects: subject: Probability (math.PR)
subject: Spectral Theory (math.SP)
subject: FOS: Mathematics

description: Let (X_{jk})_{j,k>=1} be i.i.d. complex random variables such that |X_{jk}| is in the domain of attraction of an alpha-stable law, with 0< alpha <2. Our main result is a heavy tailed counterpart of Girko's circular law. Namely, under some additional smoothness assumptions on the law of X_{jk}, we prove that there exists a deterministic sequence a_n ~ n^{1/alpha} and a probability measure mu_alpha on C depending only on alpha such that with probability one, the empirical distribution of the eigenvalues of the rescaled matrix a_n^{-1} (X_{jk})_{1<=j,k<=n} converges weakly to mu_alpha as n tends to infinity. Our approach combines Aldous & Steele's objective method with Girko's Hermitization using logarithmic potentials. The underlying limiting object is defined on a bipartized version of Aldous' Poisson Weighted Infinite Tree. Recursive relations on the tree provide some properties of mu_alpha. In contrast with the Hermitian case, we find that mu_alpha is not heavy tailed.
description: Expanded version of a paper published in Communications in Mathematical Physics 307, 513-560 (2011)
Predicting Physical Parameters of Cepheid and RR Lyrae variables
Creators: name: Bhardwaj, Anupam
name: Marconi, M.
name: Kanbur, S.
name: Bellinger, E.
name: Singh, H.P.
Publisher: name: Zenodo
Year: 2019

description: We present an application of non-linear optimization to RR Lyrae variables in the Galactic bulge to estimate their physical parameters using a comparison of theoretical and observed light curve structure at multiple wavelengths. The multiband light curves for RR Lyrae are taken from the OGLE and VVV survey and theoretical light curves are generated from the stellar pulsation models. We adopt the Fourier amplitude and phase parameters together with observed period and mean-light properties as independent variables to perform one-to-one linear regression and predict the mass-luminosity,  temperature, radius etc. from the models for the observed stars. Our results suggest a smoother grid in all the input parameters to the pulsation models can provide accurate and precise estimate of physical parameters generated from the best-fit model to the observed light curves.
Graphene with vacancies: Supernumerary zero modes
Creators: name: Weik, Norman
name: Schindler, Johannes
name: Bera, Soumya
name: Solomon, Gemma C.
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2016
Subjects: subject: 530 Physik

description: The density of states ϱ(E) of graphene is investigated within the tight-binding (Hückel) approximation in the presence of vacancies. They introduce a nonvanishing density of zero modes nzm that act as midgap states, ϱ(E)=nzmδ(E)+smooth. As is well known, the actual number of zero modes per sample can, in principle, exceed the sublattice imbalance, Nzm≥∣∣NA−NB∣∣, where NA,NB denote the number of carbon atoms in each sublattice. In this paper, we establish a stronger relation that is valid in the thermodynamic limit and that involves the concentration of zero modes, nzm>∣∣cA−cB∣∣, where cA and cB denote the concentration of vacancies per sublattice; in particular, nzm is nonvanishing even in the case of balanced disorder, NA/NB=1. Adopting terminology from benzoid graph theory, the excess modes associated with the current carrying backbone (percolation cluster) are called supernumerary. In the simplest cases, such modes can be associated with structural elements such as carbon atoms connected with a single bond, only. Our result suggests that the continuum limit of bipartite hopping models supports nontrivial “supernumerary” terms that escape the present continuum descriptions.
Incommensurate quantum-size oscillations in acene-based molecular wires—Effects of quantum fluctuations
Creators: name: Schmitteckert, Peter
name: Thomale, Ronny
name: Korytár, Richard
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2017
Subjects: subject: 530 Physik

description: Molecular wires of the acene-family can be viewed as a physical realization of a two-rung ladder Hamiltonian. For acene-ladders, closed-shell ab initio calculations and elementary zone-folding arguments predict incommensurate gap oscillations as a function of the number of repetitive ring units, NR, exhibiting a period of about ten rings. Results employing open-shell calculations and a mean-field treatment of interactions suggest anti-ferromagnetic correlations that could potentially open a large gap and wash out the gap oscillations. Within the framework of a Hubbard model with repulsive on-site interaction, U, we employ a Hartree-Fock analysis and the density matrix renormalization group to investigate the interplay of gap oscillations and interactions. We confirm the persistence of incommensurate oscillations in acene-type ladder systems for a significant fraction of parameter space spanned by U and NR.
Bulge and Globular Cluster Connection: Evolutionary Population Synthesis with Multiple Populations
Creators: name: Chung, Chul
name: Lee, Young-Wook
name: Lim, Dong-Wook
name: Hong, Seungsoo
Publisher: name: Zenodo
Year: 2019

description: Recently, Lee et al. (2018) have reported the observational evidences that Galactic bulge consists of stellar populations originated from Milky Way globular clusters (MWGCs). Motivated by this, here we present the evolutionary population synthesis (EPS) for Galactic bulge with the realistic treatment of individual variations in light elements observed in the MWGCs. We have tested our integrated absorption-indices model for the age dating of bulge GCs and the results show remarkable agreements with those derived from the isochrone-fitting in color-magnitude diagrams. We further apply our model to estimate the age of early-type galaxies (ETGs), which are considered as good analogues for the MW bulge. We find that, without the effect of our new treatments, EPS models will almost always underestimate the true age of ETGs. The implication of this result will be discussed in detail.
A light-front coupled-cluster method for the nonperturbative solution of quantum field theories
Creators: name: Chabysheva, S. S.
name: Hiller, J. R.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We propose a new method for the nonperturbative solution of quantum field theories and illustrate its use in the context of a light-front analog to the Greenberg--Schweber model. The method is based on light-front quantization and uses the exponential-operator technique of the many-body coupled-cluster method. The formulation produces an effective Hamiltonian eigenvalue problem in the valence Fock sector of the system of interest, combined with nonlinear integral equations to be solved for the functions that define the effective Hamiltonian. The method avoids the Fock-space truncations usually used in nonperturbative light-front Hamiltonian methods and, therefore, does not suffer from the spectator dependence, Fock-sector dependence, and uncanceled divergences caused by such truncations.
description: 11 pages, 4 figures, RevTeX 4.1; expanded description of method and replaced QED with simpler model for illustration
First-principles study of the structure of water layers on flat and stepped Pb electrodes
Creators: name: Lin, Xiaohang
name: Evers, Ferdinand
name: Groß, Axel
Publisher: name: Universität Regensburg
Year: 2016
Subjects: subject: density functional theory calculations; Pb surfaces; stepped surfaces; vibrational spectrum; water structure
subject: 530 Physik

description: On the basis of perodic density functional theory (DFT) calculations, we have addressed the geometric structures and electronic properties of water layers on flat and stepped Pb surfaces. In contrast to late d-band metals, on Pb(111) the energy minimum structure does not correspond to an ice-like hexagonal arrangement at a coverage of 2/3, but rather to a distorted structure at a coverage of 1 due to the larger lattice constant of Pb. At stepped Pb surfaces, the water layers are pinned at the step edge and form a complex network consisting of rectangles, pentagons and hexagons. The thermal stability of the water layers has been studied by using ab initio molecular dynamics simulations (AIMD) at a temperature of 140 K. Whereas the water layer on Pb(111) is already unstable at this temperature, the water layers on Pb(100), Pb(311), Pb(511) and Pb(711) exhibit a higher stability because of stronger water–water interactions. The vibrational spectra of the water layers at the stepped surfaces show a characteristic splitting into three modes in the O–H stretch region.
Hubble Space Telescope Imaging of Bulge Stellar Populations
Creators: name: Cohen, Roger E.
Publisher: name: Zenodo
Year: 2019

description: The photometric and astrometric precision of the Hubble Space Telescope (HST) has enabled detailed studies of stellar populations towards the Galactic bulge.  I will highlight several recent results obtained from HST imaging of the bulge, and discuss near-term future prospects using existing HST instrumentation.  These science cases will be placed in the context of both the advantages and limitations of HST as well as current and planned ground- and space-based facilities.
How to compare diffusion processes assessed by single-particle tracking and pulsed field gradient nuclear magnetic resonance
Creators: name: Bauer, Michael
name: Valiullin, Rustem
name: Radons, Günter
name: Kärger, Jörg
Publisher: name: arXiv
Year: 2010
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Heterogeneous diffusion processes occur in many different fields such as transport in living cells or diffusion in porous media. A characterization of the transport parameters of such processes can be achieved by ensemble-based methods, such as pulsed field gradient nuclear magnetic resonance (PFG NMR), or by trajectory-based methods obtained from single-particle tracking (SPT) experiments. In this paper, we study the general relationship between both methods and its application to heterogeneous systems. We derive analytical expressions for the distribution of diffusivities from SPT and further relate it to NMR spin-echo diffusion attenuation functions. To exemplify the applicability of this approach, we employ a well-established two-region exchange model, which has widely been used in the context of PFG NMR studies of multiphase systems subjected to interphase molecular exchange processes. This type of systems, which can also describe a layered liquid with layer-dependent self-diffusion coefficients, has also recently gained attention in SPT experiments. We reformulate the results of the two-region exchange model in terms of SPT-observables and compare its predictions to that obtained using the exact transformation which we derived.
description: v2: 14 pages, 6 figures, several enhancements, added references; v1: 7 pages, 3 figures
Modeling flux tunability in Josephson Traveling Wave Parametric Amplifiers with an open-source frequency-domain simulator
Creators: name: Levochkina, A.
name: Chatterjee, I.
name: Darvehi, P.
name: Ahmad, H. G.
name: Mastrovito, P.
name: Massarotti, D.
name: Montemurro, D.
name: Tafuri, F.
name: Pepe, G. P.
name: O'Brien, Kevin P.
name: Esposito, M.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Josephson Traveling Wave Parametric Amplifiers (JTWPAs) are integral parts of many experiments carried out in quantum technologies. Being composed of hundreds of Josephson junction-based unit cells, such devices exhibit complex nonlinear behavior that typically cannot be fully explained with simple analytical models, thus necessitating the use of numerical simulators. A very useful characteristic of JTWPAs is the possibility of being biased by an external magnetic flux, allowing insitu control of the nonlinearity. It is therefore very desirable for numerical simulators to support this feature. Open-source numerical tools that allow to model JTWPA flux biasing, such as WRSPICE or PSCAN2, are based on time-domain approaches,which typically require long simulation times to get accurate results. In this work, we model the gain performance in a prototypical flux-tunable JTWPA by using JosephsonCircuits.jl,a recently developed frequency-domain open-source numerical simulator, which has the benefit of simulation times about 10,000 faster than time-domain methods. By comparing the numerical and experimental results, we validate this approach for modeling the flux dependent behavior of JTWPAs.
Random groups and Property (T): Żuk's theorem revisited
Creators: name: Kotowski, Marcin
name: Kotowski, Michal
Publisher: name: arXiv
Year: 2011
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 20F65

description: We provide a full and rigorous proof of a theorem attributed to Żuk, stating that random groups in the Gromov density model for d > 1/3 have property (T) with high probability. The original paper had numerous gaps, in particular, crucial steps involving passing between different models of random groups were not described. We fix the gaps using combinatorial arguments and a recent result concerning perfect matchings in random hypergraphs. We also provide an alternative proof, avoiding combinatorial difficulties and relying solely on spectral properties of random graphs in G(n, p) model.
description: v2: minor corrections
title: Ovarian pseudotorsion: pelvic adhesions as an unusual cause of ovarian infarction
Creators: name: Zaki-Metias, Kaitlin
Publisher: name: EURORAD
Year: 2021
Subjects: subject: Genital (female) imaging
subject: Genital / Reproductive system female
subject: Ultrasound
subject: Ultrasound-Colour Doppler
subject: Ultrasound-Spectral Doppler
subject: Surgery
subject: Ischaemia / Infarction
subject: Pathology
subject: Clinical Cases

description: Clinical History: A 30-year-old female with a thirteen-year history of end-stage renal disease on peritoneal dialysis presented to the emergency department with acute onset left lower quadrant abdominal pain that morning. She denied fever, chills, nausea, vomiting, or diarrhoea. Physical examination revealed tenderness to deep palpation of the left adnexa without a palpable mass. Urine pregnancy test was negative and a complete blood count was unremarkable.

description: 30 years, female
Exponential growth of torsion in Abelian coverings
Creators: name: Raimbault, Jean
Publisher: name: arXiv
Year: 2010
Subjects: subject: Geometric Topology (math.GT)
subject: FOS: Mathematics

description: We study the growth of the order of torsion subgroups of the homology in a tower of finite abelian coverings. In particular, we prove that it is exponential for when the tower converges to the maximal free abelian cover of a link complement when the first nonzero Alexander polynomial has positive logarithmic Mahler measure.
description: 42 pages, to appear in AGT. Various minor mistakes corrected and exposition changed
$L^p$ Error Estimates for Approximation by Sobolev Splines and Wendland Functions on $\mathbb{R}^d$
Creators: name: Ward, John Paul
Publisher: name: arXiv
Year: 2011
Subjects: subject: Classical Analysis and ODEs (math.CA)
subject: FOS: Mathematics

description: It is known that a Green's function-type condition may be used to derive rates for approximation by radial basis functions (RBFs). In this paper, we introduce a method for obtaining rates for approximation by functions which can be convolved with a finite Borel measure to form a Green's function. Following a description of the method, rates will be found for two classes of RBFs. Specifically, rates will be found for the Sobolev splines, which are Green's functions, and the perturbation technique will then be employed to determine rates for approximation by Wendland functions.
Functional renormalization group approach to electronic structure calculations for systems without translational symmetry
Creators: name: Seiler, Christian
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2016
Subjects: subject: 530 Physik

description: A formalism for electronic-structure calculations is presented that is based on the functional renormalization group (FRG). The traditional FRG has been formulated for systems that exhibit a translational symmetry with an associated Fermi surface, which can provide the organization principle for the renormalization group (RG) procedure. We here advance an alternative formulation, where the RG flow is organized in the energy-domain rather than in k space. This has the advantage that it can also be applied to inhomogeneous matter lacking a band structure, such as disordered metals or molecules. The energy-domain FRG (εFRG) presented here accounts for Fermi-liquid corrections to quasiparticle energies and particle-hole excitations. It goes beyond the state of the art GW-BSE, because in εFRG the Bethe-Salpeter equation (BSE) is solved in a self-consistent manner. An efficient implementation of the approach that has been tested against exact diagonalization calculations and calculations based on the density matrix renormalization group is presented. Similar to the conventional FRG, also the εFRG is able to signalize the vicinity of an instability of the Fermi-liquid fixed point via runaway flow of the corresponding interaction vertex. Embarking upon this fact, in an application of εFRG to the spinless disordered Hubbard model we calculate its phase boundary in the plane spanned by the interaction and disorder strength. Finally, an extension of the approach to finite temperatures and spin S=1/2 is also given.
Self-consistent-field ensembles of disordered Hamiltonians: Efficient solver and application to superconducting films
Creators: name: Stosiek, Matthias
name: Lang, Bruno
name: Evers, Ferdinand
Publisher: name: Universität Regensburg
Year: 2020
Subjects: subject: 530 Physik

description: Our general interest is in self-consistent-field (scf) theories of disordered fermions. They generate physically relevant subensembles (“scf ensembles”) within a given Altland-Zirnbauer class. We are motivated to investigate such ensembles (i) by the possibility to discover new fixed points due to (long-range) interactions; (ii) by analytical scf theories that rely on partial self-consistency approximations awaiting a numerical validation; and (iii) by the overall importance of scf theories for the understanding of complex interaction-mediated phenomena in terms of effective single-particle pictures. In this paper we present an efficient, parallelized implementation solving scf problems with spatially local fields by applying a kernel-polynomial approach. Our first application is the Boguliubov-deGennes theory of the attractive-U Hubbard model in the presence of on-site disorder; the sc fields are the particle density n(r) and the gap function Δ(r). For this case, we reach system sizes unprecedented in earlier work. They allow us to study phenomena emerging at scales substantially larger than the lattice constant, such as the interplay of multifractality and interactions or the formation of superconducting islands. For example, we observe that the coherence length exhibits a nonmonotonic behavior with increasing disorder strength already at moderate U. With respect to methodology our results are important because we establish that partial self-consistency (“energy-only”) schemes as typically employed in analytical approaches tend to miss qualitative physics such as island formation.
The Law of Observation: A Unified Framework for Quantum Mechanics, Consciousness, and Spacetime
Creators: name: Sambey, Stanley Everett
Publisher: name: Zenodo
Year: 2025

description: The Law of Observation presents a novel theoretical frameworkthat unifies quantum mechanics, consciousness, and spacetimethrough the central role of the observer. The theory proposes that re-ality is shaped by observation, where the act of observing refinesa probabilistic quantum substrate, influencing the emergence of space-time, gravity, and time as observer-dependent phenomena. Conscious-ness is modeled as a spectrum influencing the Data Substrate (ψn(x)),with the observer’s role central in shaping physical laws. This frame-work presents testable hypotheses, including predictions on gravi-tational wave dispersion and the collapse of consciousness atdeath, opening avenues for empirical investigation.
Multiplicity of atomic reconfigurations in an electrochemical Pb single-atom transistor
Creators: name: Xie, F.-Q.
name: Lin, X.-H.
name: Gross, A.
name: Evers, Ferdinand
name: Pauly, F.
name: Schimmel, Th.
Publisher: name: Universität Regensburg
Year: 2017
Subjects: subject: 530 Physik

description: One focus of nanoelectronics research is to exploit the physical limits in size and energy efficiency. Here, we demonstrate a device in the form of a fully metallic atomic-scale transistor based on a lead (Pb) single-atom quantum point contact. The atomic configuration of the point contact determines the conductance of the Pb atomic-scale transistor. The conductance multiplicity of the Pb single-atom transistor has been confirmed by performing switching between an electrically nonconducting “off-state” and conducting “on-states” at 1G0(G0=2e2/h, where e is the electron charge, and h Planck's constant), 2.0G0, 3.0G0, 1.5G0, 2.4G0, 2.7G0, 2.8G0, and 5.4G0, respectively. Our density-functional calculations for various ideal Pb single-atom contacts explain the atomic-configuration-related conductance multiplicity of the Pb single-atom transistor. The performance of the Pb single-atom transistors indicates that both the signatures of atomic valence and conductance quantization play roles in electron transport and bistable reconfiguration. The bistable reconfiguration of the electrode tips is an underlying mechanism in the switching of the Pb atomic-scale transistors. The absolute value of the electrochemical potential applied to the gate electrode is less than 30 mV. This merit suggests Pb [besides silver (Ag)] atomic-scale transistors as potential candidates for the development of electronic circuits with low power consumption. The dimension of the switching unit in the Pb single-atom transistor is in the range of 1 nm, which is much smaller than the projected scaling limit of the gate lengths in silicon transistors (5 nm). Therefore, the metallic single-atom transistors may provide perspectives for electronic applications beyond silicon.
The Law of Observation: A Unified Framework for Quantum Mechanics, Consciousness, and Spacetime
Creators: name: Sambey, Stanley Everett
Publisher: name: Zenodo
Year: 2025

description: The Law of Observation provides a novel framework for under-standing the relationship between consciousness, observation, and thequantum substrate of reality. This paper explores the central tenetsof the Law of Observation and introduces the M¨obius strip analogy asa key metaphor for explaining the recursive, self-referential, and non-linear nature of reality. By examining how the observer and observedare intricately linked, this paper offers a deeper insight into the inter-dependent roles of observation and consciousness in shaping quantumphenomena. The following sections build upon this central concept,offering both theoretical analysis and expanded analogy to clarify theimplications of the Law of Observation.
Shape of LOSVDs in Barred Disks: Implications for Future IFU Surveys
Creators: name: Li, Zhao-Yu
name: Shen, Juntai
name: Bureau, Martin
name: Zhou, Yingying
Publisher: name: Zenodo
Year: 2019

description: The shape of line-of-sight velocity distributions (LOSVDs) carries important information about the internal dynamics of galaxies. The skewness of LOSVDs represents their asymmetric deviation from a Gaussian profile. Correlations between the skewness parameter (h 3) and the mean velocity (\overline{V}) of a Gauss–Hermite series reflect the underlying stellar orbital configurations of different morphological components. Using two self-consistent N-body simulations of disk galaxies with different bar strengths, we investigate {h}3-\overline{V} correlations at different inclination angles.
Similar to previous studies, we find anticorrelations in the disk area, and positive correlations in the bar area when viewed edge-on. However, at intermediate inclinations, the outer parts of bars exhibit anticorrelations, while the core areas dominated by the boxy/peanut-shaped (B/PS) bulges still maintain weak positive correlations. When viewed edge-on, particles in the foreground/background disk (the wing region) in the bar area constitute the main velocity peak, whereas the particles in the bar contribute to the high-velocity tail, generating the {h}3-\overline{V} correlation. If we remove the wing particles, the LOSVDs of the particles in the outer part of the bar only exhibit a low-velocity tail, resulting in a negative {h}3-\overline{V} correlation, whereas the core areas in the central region still show weakly positive correlations. We discuss implications for IFU observations on bars, and show that the variation of the {h}3-\overline{V} correlation in the disk galaxy may be used as a kinematic indicator of the bar and the B/PS bulge.
Numerical Computation of Dynamically Important Excited States of Many-Body Systems
Creators: name: Lacki, Mateusz
name: Delande, Dominique
name: Zakrzewski, Jakub
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We present an extension of the time-dependent Density Matrix Renormalization Group (t-DMRG), also known as Time Evolving Block Decimation algorithm (TEBD), allowing for the computation of dynamically important excited states of one-dimensional many-body systems. We show its practical use for analyzing the dynamical properties and excitations of the Bose-Hubbard model describing ultracold atoms loaded in an optical lattice from a Bose-Einstein condensate. This allows for a deeper understanding of nonadiabaticity in experimental realizations of insulating phases.
description: Expanded version (12pp. 13 figures)
Asymptotic entanglement in 1D quantum walks with a time-dependent coined
Creators: name: Salimi, S.
name: Yosefjani, R.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: Discrete-time quantum walk evolve by a unitary operator which involves two operators a conditional shift in position space and a coin operator. This operator entangles the coin and position degrees of freedom of the walker. In this paper, we investigate the asymptotic behavior of the coin position entanglement (CPE) for an inhomogeneous quantum walk which determined by two orthogonal matrices in one-dimensional lattice. Free parameters of coin operator together provide many conditions under which a measurement perform on the coin state yield the value of entanglement on the resulting position quantum state. We study the problem analytically for all values that two free parameters of coin operator can take and the conditions under which entanglement becomes maximal are sought.
description: 23 pages, 4 figures, accepted for publication in IJMPB. arXiv admin note: text overlap with arXiv:1001.5326 by other authors
On weak mixing, minimality and weak disjointness of all iterates
Creators: name: Kwietniak, Dominik
name: Oprocha, Piotr
Publisher: name: arXiv
Year: 2010
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: Primary 37B05, Secondary 37B10

description: The article addresses some open questions about the relations between the topological weak mixing property and the transitivity of the map $f\times f^2 \times...\times f^m$, where $f\colon X\ra X$ is a topological dynamical system on a compact metric space. The theorem stating that a weakly mixing and strongly transitive system is $Δ$-transitive is extended to a non-invertible case with a simple proof. Two examples are constructed, answering the questions posed by Moothathu [Colloq. Math. 120 (2010), no. 1, 127--138]. The first one is a multi-transitive non weakly mixing system, and the second one is a weakly mixing non multi-transitive system. The examples are special spacing shifts. The later shows that the assumption of minimality in the Multiple Recurrence Theorem can not be replaced by weak mixing.
description: 10 pages, to appear in Ergodic Theory and Dynamical Systems
Mobility spectrum analysis on three-dimensional topological insulator BiSbTeSe2
Creators: name: Wang, Jimin
name: Kurzendorfer, Alexander
name: Chen, Lin
name: Wang, Zhiwei
name: Ando, Yoichi
name: Xu, Yang
name: Miotkowski, Ireneusz
name: Chen, Yong P.
name: Weiss, Dieter
Publisher: name: Universität Regensburg
Year: 2021
Subjects: subject: 530 Physik

description: We conducted mobility spectrum analysis on a high quality three dimensional topological insulator film of BiSbTeSe2 to extract mobility μ and carrier density n. Top and bottom gates were applied to tune the carrier density on top and bottom surfaces independently. At 1.5 K, when the conduction is entirely dominated by the Dirac surface states, we always find two dominant conduction channels (top and bottom surfaces), with μ=500–3000 cm2/(V s) and n on the order of 1012 cm−2. However, at sufficiently high temperature (T=85 K), when the bulk contributes, a third channel with maximum mobility μ ∼ 400 cm2/(V s) and n on the order of 1011–1013 cm−2 opens. Our data show the feasibility of the method to analyze the different conduction channels in a topological insulator, being also promising for other similar material systems.