cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
The galaxy-wide stellar initial mass function in the presence of cluster-to-cluster IMF variations
Creators: name: Dib, Sami
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We calculate the integrated galactic initial stellar mass function (IGIMF) in the presence of IMF variations in clusters. IMF Variations for a population of clusters are taken into account in the form of Gaussian distributions of the IMF parameters. For the tapered power law function used here, these are the slopes at the high and low mass ends, $Γ$ and $γ$, and the characteristic mass $M_{ch}$. Variations are modeled by varying the width of the Gaussian distributions. The reference values are the standard deviations of the parameters observed for young clusters in the present-day Milky Way $σ_Γ=0.6$, $σ_γ=0.25$, and $σ_{M_{ch}}=0.27$ M$_{\odot}$. Increasing the dispersions of $γ$ and $Γ$ moderately flattens the IGIMF at the low and high mass ends. Increasing $σ_{M_{ch}}$ shifts the peak of the IGIMF to lower masses, rendering the IGIMF more bottom heavy. This can explain the bottom heavy stellar mass function of Early-type galaxies as they are the result of the merger of disk galaxies where the physical conditions of the star forming gas vary significantly both in time and space. The effect of IMF variations is compared to that due to other effects such as variations in the shape of the initial cluster mass function, metallicity, and galactic SFR. We find that the effect of IMF variations is a dominant factor that always affects the characteristic mass of the IGIMF. We compare our results to a sample of ultra-faint dwarf satellite galaxies (UFDs). Their present-day stellar mass function is an analog to their IGIMF at the time their stellar populations have formed. We show that the slope of the IGIMF of the UFDs can only be reproduced when IMF variations of the same order as those measured in the present-day Milky Way are included. (Abridged)
description: Accepted to A&A. Additional Figures. Figure 7 and 8 are updated, but conclusions are unchanged
A streamlined molecular-dynamics workflow for computing solubilities of molecular and ionic crystals
Creators: name: Reinhardt, Aleks
name: Chew, Pin Yu
name: Cheng, Bingqing
Publisher: name: arXiv
Year: 2023
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Chemical Physics (physics.chem-ph)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Computing the solubility of crystals in a solvent using atomistic simulations is notoriously challenging due to the complexities and convergence issues associated with free-energy methods, as well as the slow equilibration in direct-coexistence simulations. This paper introduces a molecular-dynamics workflow that simplifies and robustly computes the solubility of molecular or ionic crystals. This method is considerably more straightforward than the state-of-the-art, as we have streamlined and optimised each step of the process. Specifically, we calculate the chemical potential of the crystal using the gas-phase molecule as a reference state, and employ the S0 method to determine the concentration dependence of the chemical potential of the solute. We use this workflow to predict the solubilities of sodium chloride in water, urea polymorphs in water, and paracetamol polymorphs in both water and ethanol. Our findings indicate that the predicted solubility is sensitive to the chosen potential energy surface. Furthermore, we note that the harmonic approximation often fails for both molecular crystals and gas molecules at or above room temperature, and that the assumption of an ideal solution becomes less valid for highly soluble substances.
Influence of electromagnetic fields on the evolution of initially homogeneous and isotropic universe
Creators: name: Alekseev, G. A.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Simple exact solutions presented here describe the universes which spatial geometries are asymptotically homogeneous and isotropic near the initial singularity, but which evolution goes under the influence of primordial magnetic fields. In all these "deformed" Friedmann models (spatially flat, open or closed), the initial magnetic fields are concentrated near some axis of symmetry and their lines are the circles -- the lines of the azimuthal coordinate $φ$. Caused by the expansion of the universe, the time-dependence of a magnetic field induces (in accordance with the Faraday law) the emergence of source-free electric fields. In comparison with the Friedmann models, the cosmological expansion goes with acceleration in spatial directions across the magnetic field, and with deceleration along the magnetic lines, so that in flat and open models, in fluid comoving coordinates, the lengths of $φ$-circles of large enough radius or for late enough times decrease and vanish for $t\to\infty$. This means that in flat and open models, we have a partial dynamical closure of space-time at large distances from the axis, i.e. from the regions where the electromagnetic fields in our solutions are concentrated. To get simple exact solutions of the Einstein-Maxwell and perfect fluid equations, we assume for the perfect fluid (which supports the isotropic and homogeneous "background" Friedmann geometries) rather exotic, stiff matter equation of state $\varepsilon=p$. However, it seems reasonable to expect that similar effects might take place in the mutual dynamics of geometry and strong electromagnetic fields in the universes with more realistic matter equations of state.
description: 14 pages, 1 figure
The metallicity evolution of low mass galaxies: New constraints at intermediate redshift
Creators: name: Henry, Alaina
name: Martin, Crystal L.
name: Finlator, Kristian
name: Dressler, Alan
Publisher: name: arXiv
Year: 2013
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present abundance measurements from 26 emission-line selected galaxies at z~0.6-0.7. By reaching stellar masses as low as 10^8 M_{\sun}, these observations provide the first measurement of the intermediate redshift mass-metallicity (MZ) relation below 10^9 M_{\sun} For the portion of our sample above M > 10^9 M_{\sun} (8/26 galaxies), we find good agreement with previous measurements of the intermediate redshift MZ relation. Compared to the local relation, we measure an evolution that corresponds to a 0.12 dex decrease in oxygen abundances at intermediate redshifts. This result confirms the trend that metallicity evolution becomes more significant towards lower stellar masses, in keeping with a downsizing scenario where low mass galaxies evolve onto the local MZ relation at later cosmic times. We show that these galaxies follow the local fundamental metallicity relation, where objects with higher specific (mass-normalized) star formation rates (SFRs) have lower metallicities. Furthermore, we show that the galaxies in our sample lie on an extrapolation of the SFR-M_{*} relation (the star-forming main sequence). Leveraging the MZ relation and star-forming main sequence (and combining our data with higher mass measurements from the literature), we test models that assume an equilibrium between mass inflow, outflow and star formation. We find that outflows are required to describe the data. By comparing different outflow prescriptions, we show that momentum driven winds can describe the MZ relation; however, this model under-predicts the amount of star formation in low mass galaxies. This disagreement may indicate that preventive feedback from gas-heating has been overestimated, or it may signify a more fundamental deviation from the equilibrium assumption.
description: Accepted for publication in ApJ
Enhanced chiral edge currents and orbital magnetic moment in chiral $d$-wave superconductors from mesoscopic finite-size effects
Creators: name: Holmvall, Patric
name: Black-Schaffer, Annica M.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Chiral superconductors spontaneously break time-reversal symmetry and host topologically protected edge modes, supposedly generating chiral edge currents which are typically taken as a characteristic fingerprint of chiral superconductivity. However, recent studies have shown that the total edge current in two dimensions (2D) often vanishes for all chiral superconductors except for chiral $p$-wave, especially at low temperatures, thus severely impeding potential experimental verification and characterization of these superconductors. In this work, we use quasiclassical theory of superconductivity to study mesoscopic disc-schaped chiral $d$-wave superconductors. We find that mesoscopic finite-size effects cause a dramatic enhancement of the total charge current and orbital magnetic moment (OMM), even at low temperatures. We study how these quantities scale with temperature, spontaneous Meissner screening, and system radius $\mathcal{R} \in [5,200]ξ_0$ with superconducting coherence length $ξ_0$. We find a general $1/\mathcal{R}$ scaling in the total charge current and OMM for sufficiently large systems, but this breaks down in small systems, instead producing a local maximum at $\mathcal{R} \approx 10{\text{--}}20ξ_0$ due to mesoscopic finite-size effects. These effects also cause a spontaneous charge-current reversal opposite to the chirality below $\mathcal{R} < 10ξ_0$. Our work highlights mesoscopic systems as a route to experimentally verify chiral $d$-wave superconductivity, measurable with magnetometry.
description: 23 pages, 14 figures
General Time-Dependent Configuration-Interaction Singles I: The Molecular Case
Creators: name: Carlström, Stefanos
name: Spanner, Michael
name: Patchkovskii, Serguei
Publisher: name: arXiv
Year: 2022
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We present a grid-based implementation of the time-dependent configuration-interaction singles method suitable for computing the strong-field ionization of small gas-phase molecules. After outlining the general equations of motion used in our treatment of this method, we present example calculations of strong-field ionization of helium, lithium hydride, water, and ethylene that demonstrate the utility of our implementation. The following companion paper specializes to the case of spherical symmetry, which is applied to various atoms.
On the number of minimal models of a log smooth threefold
Creators: name: Cascini, Paolo
name: Lazić, Vladimir
Publisher: name: arXiv
Year: 2013
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14E30

description: We give a topological bound on the number of minimal models of a class of three dimensional log smooth pairs of general type.
Multiplicity-free Kronecker Products of characters of the alternating groups
Creators: name: Homma, Adrian
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2022
Subjects: subject: Symmetrische Gruppen
subject: Alternierende Gruppen
subject: Darstellungstheorie
subject: Dewey Decimal Classification::500 | Naturwissenschaften::510 | Mathematik

description: In this work we classify the multiplicity-free Kronecker products of irreducible characters of the alternating groups.
Antiferromagnetic order in Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$ observed by $^{75}$As NMR
Creators: name: Zhou, T.
name: Koutroulakis, G.
name: Lodico, J.
name: Ni, Ni
name: Thompson, J. D.
name: Cava, R. J.
name: Brown, S. E.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: $^{75}$As nuclear magnetic resonance (NMR) measurements carried out on underdoped, non-superconducting Ca$_{10}$(Pt$_3$As$_8$)(Fe$_2$As$_2$)$_5$ reveal physical properties that are similar but not identical to the 122 superconductor parent compounds such as BaFe$_2$As$_2$. Results from the single crystal study indicate a phase transition to an antiferromagnetic (AF) state on cooling through T~100K, albeit nonuniformly. Specifically, the NMR lineshape reflects the presence of staggered hyperfine fields on the As sites associated with a striped AF order. The variation of the internal hyperfine field with temperature suggests that the phase transition to the AF state is discontinuous, and therefore likely coincident with the structural transition inferred from transport experiments.
description: 5 pages, 3 figures
Additional file 4 of H2 generated by fermentation in the human gut microbiome influences metabolism and competitive fitness of gut butyrate producers
Creators: name: Campbell, Austin
name: Gdanetz, Kristi
name: Schmidt, Alexander W.
name: Schmidt, Thomas M.
Publisher: name: figshare
Year: 2023
Subjects: subject: Biochemistry
subject: Microbiology
subject: FOS: Biological sciences
subject: Genetics
subject: Physiology
subject: Pharmacology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: Immunology
subject: FOS: Clinical medicine
subject: 69999 Biological Sciences not elsewhere classified
subject: Cancer

description: Additional file 4: Table S3.
Quantum Otto engine driven by quantum fields
Creators: name: Gallock-Yoshimura, Kensuke
name: Thakur, Vaishant
name: Mann, Robert B.
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We consider a quantum Otto engine using an Unruh-DeWitt particle detector model which interacts with a quantum scalar field in curved spacetime. We express a generic condition for extracting positive work in terms of the effective temperature of the detector. This condition reduces to the well-known positive work condition in the literature under the circumstances where the detector reaches thermal equilibrium with the field. We then evaluate the amount of work extracted by the detector in two scenarios: an inertial detector in a thermal bath and a circulating detector in the Minkowski vacuum, which is inspired by the Unruh quantum Otto engine.
description: 21 pages, 7 figures; (v2) Made some small corrections
SYK model with an extra diagonal perturbation: phase transition in the eigenvalue spectrum
Creators: name: Wu, Shuang
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mathematical Physics (math-ph)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: High Energy Physics - Theory (hep-th)
subject: Combinatorics (math.CO)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We study the SYK model with an extra constant source, i.e. a constant matrix or equivalently a diagonal matrix with only one non-zero entry $λ_1$. By using methods from analytic combinatorics, we find exact expressions for the moments of this model. We further prove that the spectrum of this model can have a gap when $λ_1>λ^c_1$, thus exhibiting a phase transition in $λ_1$. In this case, a single isolated eigenvalue splits off from SYK's eigenvalues distribution. We located this single eigenvalue by analyzing the singular behavior of a supercritical functional composition scheme. In certain limit our results recover the ones of random matrices with non-zero mean entries.
description: 22 pages (1 appendix and with references included), 7 figures
Water mediated pot, atom, and step economic (PASE) synthesis of pyrimido[4,5-d]pyrimidines using ultrasound and microwave irradiation approaches
Creators: name: Trivedi, Harsh D.
name: Joshi, Vidhi B.
name: Patel, Bonny Y.
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Biophysics
subject: Biochemistry
subject: Medicine
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Sociology
subject: FOS: Sociology
subject: 69999 Biological Sciences not elsewhere classified
subject: FOS: Biological sciences
subject: Plant Biology
subject: 60506 Virology

description: The functioning, Pot, Atom, and Step Economic (PASE) green chemistry proposition has been approached for the synthesis of pyrimido[4,5-d]pyrimidines by the multicomponent reaction (MCR) of barbituric acid, guanidine, and aldehyde derivatives using water solvent and iodine catalyst through ultrasound and microwave irradiation methods. Reaction optimization was performed by varying solvents, reaction time, the concentration of catalyst, and reaction methods. Microwave irradiation approach using water solvent and iodine catalyst (8 mol%) with 5 min led to offer the highest yield. EWG substituted compound 4 g (4-NO2, guanidine) [87% (U.S.), 93% (M.W.)] was found to be the highest yielded compound in this study. The greenness of the reaction was estimated by calculating some green chemistry metrics. The metrics approved the proposed protocol as an ideal, green, and sustainable approach.
Experimentelle und theoretische Untersuchung asymptotischer molekularer Zustände am Beispie Na2
Creators: name: Elbs, Michael
Publisher: name: Hannover : Universität
Year: 1998
Subjects: subject: Long-range interactions
subject: scattering length
subject: Na2
subject: Dewey Decimal Classification::500 | Naturwissenschaften::530 | Physik

description: [no abstract]
Gravitational Lensing in Modified Gravity: A case study for Fast Radio Bursts
Creators: name: Kalita, Surajit
name: Bhatporia, Shruti
name: Weltman, Amanda
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Over the last few decades, a plethora of modifications to general relativity have been proposed to solve a host of cosmological and astrophysical problems. Many modified gravity models are now ruled out with further astrophysical observations; some theories are still viable, with, at best, bounds on their parameters set by observations to date. More recently, observations of Fast Radio Bursts have proven to be remarkably powerful tools to constrain cosmology and fundamental physics. In this work, we consider a generic modified gravity theory and consider the implications for gravitational lensing with Fast Radio Bursts. We use a set of Fast Radio Burst observations to constrain the fraction of dark matter made up of primordial black holes in such a theory. We further show that modified gravity adds a screening effect on gravitational lensing similar to the case when there is plasma in the path of the light ray acting as a scattering screen.
description: 16 pages with 4 figures; version accepted for publication in JCAP
General Time-Dependent Configuration-Interaction Singles II: The Atomic Case
Creators: name: Carlström, Stefanos
name: Bertolino, Mattias
name: Dahlström, Jan Marcus
name: Patchkovskii, Serguei
Publisher: name: arXiv
Year: 2022
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We present a specialization of the grid-based implementation of the time-dependent configuration-interaction singles described in the preceding paper (arXiv:2204.09966) to the case of spherical symmetry. We describe the intricate time propagator in detail, and conclude with a few example calculations. Among these, of note are high-resolution photoelectron spectra in the vicinity of the Fano resonances in photoionization of neon, and spin-polarized photoelectrons from xenon, in agreement with recent experiments.
The COS/UVES Absorption Survey of the Magellanic Stream: I. One-Tenth Solar Abundances along the Body of the Stream
Creators: name: Fox, Andrew J.
name: Richter, Philipp
name: Wakker, Bart P.
name: Lehner, Nicolas
name: Howk, J. Christopher
name: Bekhti, Nadya Ben
name: Bland-Hawthorn, Joss
name: Lucas, Stephen
Publisher: name: arXiv
Year: 2013
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The Magellanic Stream (MS) is a massive and extended tail of multi-phase gas stripped out of the Magellanic Clouds and interacting with the Galactic halo. In this first paper of an ongoing program to study the Stream in absorption, we present a chemical abundance analysis based on HST/COS and VLT/UVES spectra of four AGN (RBS 144, NGC 7714, PHL 2525, and HE 0056-3622) lying behind the MS. Two of these sightlines yield good MS metallicity measurements: toward RBS 144 we measure a low MS metallicity of [S/H]=[S II/H I]=-1.13+/-0.16 while toward NGC 7714 we measure [O/H]=[O I/H I]=-1.24+/-0.20. Taken together with the published MS metallicity toward NGC 7469, these measurements indicate a uniform abundance of ~0.1 solar along the main body of the Stream. This provides strong support to a scenario in which most of the Stream was tidally stripped from the SMC ~1.5--2.5 Gyr ago (a time at which the SMC had a metallicity of ~0.1 solar), as predicted by several N-body simulations. However, in Paper II of this series (Richter et al. 2013), we report a much higher metallicity (S/H=0.5 solar) in the inner Stream toward Fairall 9, a direction sampling a filament of the MS that Nidever et al. (2008) claim can be traced kinematically to the LMC, not the SMC. This shows that the bifurcation of the Stream is evident in its metal enrichment. Finally we measure a similar low metallicity [O/H]=[O I/H I]=-1.03+/-0.18 in the v_LSR=150 km/s cloud toward HE 0056--3622, which belongs to a population of anomalous velocity clouds near the South Galactic Pole. This suggests these clouds are associated with the Stream or more distant structures (possibly the Sculptor Group, which lies in this direction at the same velocity), rather than tracing foreground Galactic material.
description: Accepted by ApJ; 17 pages, 11 figures
Resistive instabilities in sinusoidal shear flows with a streamwise magnetic field
Creators: name: Fraser, Adrian E.
name: Cresswell, Imogen G.
name: Garaud, Pascale
Publisher: name: arXiv
Year: 2022
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: We investigate the linear stability of a sinusoidal shear flow with an initially uniform streamwise magnetic field in the framework of incompressible magnetohydrodynamics (MHD) with finite resistivity and viscosity. This flow is known to be unstable to the Kelvin-Helmholtz instability in the hydrodynamic case. The same is true in ideal MHD, where dissipation is neglected, provided the magnetic field strength does not exceed a critical threshold beyond which magnetic tension stabilizes the flow. Here, we demonstrate that including viscosity and resistivity introduces two new modes of instability. One of these modes, which we call a resistively-unstable Alfvén wave due to its connection to shear Alfvén waves, exists for any nonzero magnetic field strength as long as the magnetic Prandtl number $Pm < 1$. We present a reduced model for this instability that reveals its excitation mechanism to be the negative eddy viscosity of periodic shear flows described by Dubrulle & Frisch (1991). Finally, we demonstrate numerically that this mode saturates in a quasi-stationary state dominated by counter-propagating solitons.
description: 23 pages, 10 figures, submitted to JFM
Organic selective contacts for crystalline silicon solar cells
Creators: name: Halbich, Marc-Uwe
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2021
Subjects: subject: silicon solar cell
subject: selective contact
subject: PEDOT:PSS/c-Si heterojunction
subject: Siliziumsolarzelle
subject: Selektiver Kontakt
subject: PEDOT:PSS/c-si Heteroübergang
subject: Dewey Decimal Classification::500 | Naturwissenschaften::530 | Physik

description: The hole-conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) [PEDOT:PSS] is known to effectively passivate crystalline silicon surfaces and to simultaneously provide a low contact resistance for holes. PEDOT: PSS can therefore be applied as a hole-selective, passivating contact layer in silicon solar cells. In this thesis, PEDOT:PSS/c-Si solar cells with phosphorusdiffused front and PEDOT:PSS/c-Si heterojunction at the rear (‘BackPEDOT’ solar cells) are manufactured and the selectivity of PEDOT:PSS on crystalline silicon is examined. On random-pyramid-textured silicon surfaces covered with PEDOT:PSS we observe for the first time an additional thin organic layer, which has an increased sulfur content in comparison to the bulk PEDOT:PSS and which is responsible for the passivation of the silicon surface. The maximum shortcircuit current density increases with decreasing PEDOT:PSS layer thickness. In order to further reduce the parasitic absorption, the impact of additives to the PEDOT:PSS dispersion is investigated. We hereby demonstrate for the first time, that the admixture of sorbitol not only reduces the parasitic absorption in PEDOT: PSS, but also improves the passivation quality of PEDOT:PSS on silicon. A maximum energy conversion efficiency of 20.6% of a BackPEDOT solar cell was achieved for PEDOT:PSS with sorbitol admixture. This is the highest efficiency achieved so far for a c-Si solar cell with an organic selective contact. Furthermore, the band bending within the silicon bulk of the PEDOT:PSS/c-Si junction is examined by a newly introduced methodology based on the Depletion Region Modulation (DRM) effect. For the first time we demonstrate that admixture of sorbitol to the PEDOT:PSS dispersion improves the chemical interface passivation, but the band bending within the silicon bulk towards the PEDOT:PSS/c-Si interface remains unaffected.
Simulating spin measurement with a finite heat bath model for the environment
Creators: name: Dittrich, Thomas
name: guez, Óscar Rodrí
name: Viviescas, Carlos
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Spin measurement is studied as a unitary time evolution of the spin coupled to an environment representing the meter and the apparatus. Modelling the environment as a heat bath comprising only a finite number of boson modes and represented in a basis of coherent states, following the Davydov ansatz, it can be fully included in the quantum time evolution of the total system. We perform numerical simulations of projective measurements of the polarization, with the spins prepared initially in a neutral pure state. The likewise pure initial state of the environment is constructed as a product of coherent states of the boson modes with a random distribution of their centroids around the origin of phase space. Switching the self-energy of the spin and the coupling to the heat bath on and off by a time-dependent modulation, we observe the outcome of the measurement in terms of the long-time behaviour of the spin. Interacting with the heat bath, the spins get entangled with it and lose coherence, thus reproduce the "collapse of the wavefunction". The expected quantum randomness in the final state is manifest in our simulations as a tendency of the spin to approach either one of the two eigenstates of the measured spin operator, recovering an almost pure state. The unitary time evolution allows us to reproducibly relate these random final states to the respective initial states of the environment and to monitor the exchange of information between the two subsystems in terms of their purity and mutual entropy.
description: 13 pages, 9 figures
Entanglement For Atom Interferometers
Creators: name: Idel, Alexander
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2021
Subjects: subject: entanglement
subject: atom optic
subject: atom interferometry
subject: Verschränkung
subject: Atomoptik
subject: Atominterferometrie
subject: Dewey Decimal Classification::500 | Naturwissenschaften::530 | Physik

description: Quantum Sensors, like atom interferometers (AI), can be employed for high-precision measurements of inertial forces, including their application as gravimeters, gradiometers, accelerometers, and gyroscopes. Their measurement principle relies on ultracold atoms that are prepared in quantum-mechanical superposition states in external degrees of freedom. These states can be prepared by a momentum transfer of a Raman laser. Then the superposition state senses the effect of an inertial force, which induce a corresponding relative phase. The phase is read out by a final coupling which converts the interferometric phase into a atom number difference between the two states. The difference provides an estimate of the interferometric phase and the corresponding quantity of interest. The quantum mechanical noise of the atomic ensemble cause a fundamental uncertainty of this estimation, which I analyze for generic AIs. For small atomic densities, the quantum phase noise of the ensemble limits the interferometric sensitivity. For large densities, quantum number fluctuations generate density fluctuations, which generates phase noise. I show that these two competing effects result in an optimal atom number with a maximal interferometer resolution. Squeezed atomic samples allow for a reduction of the quantum noise of one quantity at the expense of an increased noise along of a conjugate quantity. Phase and number are such quantities which obey to a variant of Heisenberg’s uncertainty principle. Neither phase nor number squeezing can improve the maximal interferometer resolution. As one main result of this thesis, I show how an optimal squeezing in between number and phase squeezing, allows for a fundamental improvement. I evaluate possible experimental paths to implement the proposed protocol. Concepts for a squeezing-enhanced operation of external-degree AIs have not yet been demonstrated. I propose and implement an atomic gravimeter, which is designed to accept spin-squeezed atomic states as input states. The interferometer is designed such that the interferometer couplings are performed in spin space, while the phase accumulation is performed in momentum states. For this interferometer, the squeezed input can be directly obtained from spin dynamics in spinor Bose-Einstein condensates. The main noise contributions in the experiment are analyzed, which results in a factor of 84 above the relevant quantum limit, preventing a squeezing enhancement so far. I outline a suppression of the main noise source, uncontrolled AC Stark shift on the squeezed mode and propose future important applications, including test of spontaneous collapse theories and an improvement of large-scale, high-precision gradiometers.
Evolution and excitation conditions of outflows in high-mass star-forming regions
Creators: name: Sanchez-Monge, A.
name: Lopez-Sepulcre, A.
name: Cesaroni, R.
name: Walmsley, C. M.
name: Codella, C.
name: Beltran, M. T.
name: Pestalozzi, M.
name: Molinari, S.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Theoretical models suggest that massive stars form via disk-mediated accretion, with bipolar outflows playing a fundamental role. A recent study toward massive molecular outflows has revealed a decrease of the SiO line intensity as the object evolves. The present study aims at characterizing the variation of the molecular outflow properties with time, and at studying the SiO excitation conditions in outflows associated with massive YSOs. We used the IRAM30m telescope to map 14 massive star-forming regions in the SiO(2-1), SiO(5-4) and HCO+(1-0) outflow lines, and in several dense gas and hot core tracers. Hi-GAL data was used to improve the spectral energy distributions and the L/M ratio, which is believed to be a good indicator of the evolutionary stage of the YSO. We detect SiO and HCO+ outflow emission in all the sources, and bipolar structures in six of them. The outflow parameters are similar to those found toward other massive YSOs. We find an increase of the HCO+ outflow energetics as the object evolve, and a decrease of the SiO abundance with time, from 10^(-8) to 10^(-9). The SiO(5-4) to (2-1) line ratio is found to be low at the ambient gas velocity, and increases as we move to high velocities, indicating that the excitation conditions of the SiO change with the velocity of the gas (with larger densities and/or temperatures for the high-velocity gas component). The properties of the SiO and HCO+ outflow emission suggest a scenario in which SiO is largely enhanced in the first evolutionary stages, probably due to strong shocks produced by the protostellar jet. As the object evolves, the power of the jet would decrease and so does the SiO abundance. During this process, however, the material surrounding the protostar would have been been swept up by the jet, and the outflow activity, traced by entrained molecular material (HCO+), would increase with time.
description: 31 pages, 10 figures and 5 tables (plus 2 figures and 3 tables in the appendix). Accepted for publication in A&A. [Abstract modified to fit the arXiv requirements.]
A singularity problem for interacting massive vectors
Creators: name: Mou, Zong-Gang
name: Zhang, Hong-Yi
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: Interacting massive spin-1 fields have been widely used in cosmology and particle physics. We obtain a new condition on the validity of the classical limit of these theories related to the non-trivial constraints that exist for vector field components. A violation of this consistency condition causes a singularity in the time derivative of the auxiliary component and could impact, for example, the field's cosmic history and superradiance around black holes. Such a condition is expected to exist generically in many other non-trivially constrained systems.
description: 4 pages, 3 figures
Marginalised Normal Regression: Unbiased curve fitting in the presence of x-errors
Creators: name: Bartlett, Deaglan
name: Desmond, Harry
Publisher: name: arXiv
Year: 2023
Subjects: subject: Methodology (stat.ME)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: The history of the seemingly simple problem of straight line fitting in the presence of both $x$ and $y$ errors has been fraught with misadventure, with statistically ad hoc and poorly tested methods abounding in the literature. The problem stems from the emergence of latent variables describing the "true" values of the independent variables, the priors on which have a significant impact on the regression result. By analytic calculation of maximum a posteriori values and biases, and comprehensive numerical mock tests, we assess the quality of possible priors. In the presence of intrinsic scatter, the only prior that we find to give reliably unbiased results in general is a mixture of one or more Gaussians with means and variances determined as part of the inference. We find that a single Gaussian is typically sufficient and dub this model Marginalised Normal Regression (MNR). We illustrate the necessity for MNR by comparing it to alternative methods on an important linear relation in cosmology, and extend it to nonlinear regression and an arbitrary covariance matrix linking $x$ and $y$. We publicly release a Python/Jax implementation of MNR and its Gaussian mixture model extension that is coupled to Hamiltonian Monte Carlo for efficient sampling, which we call ROXY (Regression and Optimisation with X and Y errors).
description: 14+6 pages, 9 figures; minor revision to match Open J. of Astrophysics accepted version
Conformal $r$-matrix-Nijenhuis structures, symplectic-Nijenhuis structures and $\mathcal{O} N$-structures
Creators: name: Liu, Jiefeng
name: Zhou, Sihan
name: Yuan, Lamei
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Algebra (math.QA)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 17A30, 17B69, 17B62

description: In this paper, we first study infinitesimal deformations of a Lie conformal algebra and a Lie conformal algebra with a module (called an $\mathsf{LCMod}$ pair), which lead to the notions of Nijenhuis operator on the Lie conformal algebra and Nijenhuis structure on the $\mathsf{LCMod}$ pair, respectively. Then by adding compatibility conditions between Nijenhuis structures and $\mathcal{O}$-operators, we introduce the notion of an $\mathcal{O} N$-structure on an $\mathsf{LCMod}$ pair and show that an $\mathcal{O} N$-structure gives rise to a hierarchy of pairwise compatible $\mathcal{O}$-operators. In particular, we show that compatible $\mathcal{O}$-operators on a Lie conformal algebra can be characterized by Nijenhuis operators on Lie conformal algebras. Finally, we introduce the notions of conformal $r$-matrix-Nijenhuis structure and symplectic-Nijenhuis structure on the Lie conformal algebra and study their relations.
description: 26 pages
Thin-shell mixing in radiative wind-shocks and the Lx-Lbol scaling of O-star X-rays
Creators: name: Owocki, Stanley P.
name: Sundqvist, Jon O.
name: Cohen, David H.
name: Gayley, Kenneth G.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: X-ray satellites since Einstein have empirically established that the X-ray luminosity from single O-stars scales linearly with bolometric luminosity, Lx ~ 10^{-7} Lbol. But straightforward forms of the most favored model, in which X-rays arise from instability-generated shocks embedded in the stellar wind, predict a steeper scaling, either with mass loss rate Lx ~ Mdot ~ Lbol^{1.7} if the shocks are radiative, or with Lx ~ Mdot^{2} ~ Lbol^{3.4} if they are adiabatic. This paper presents a generalized formalism that bridges these radiative vs. adiabatic limits in terms of the ratio of the shock cooling length to the local radius. Noting that the thin-shell instability of radiative shocks should lead to extensive mixing of hot and cool material, we propose that the associated softening and weakening of the X-ray emission can be parametrized as scaling with the cooling length ratio raised to a power m$, the "mixing exponent". For physically reasonable values m ~= 0.4, this leads to an X-ray luminosity Lx ~ Mdot^{0.6} ~ Lbol that matches the empirical scaling. To fit observed X-ray line profiles, we find such radiative-shock-mixing models require the number of shocks to drop sharply above the initial shock onset radius. This in turn implies that the X-ray luminosity should saturate and even decrease for optically thick winds with very high mass-loss rates. In the opposite limit of adiabatic shocks in low-density winds (e.g., from B-stars), the X-ray luminosity should drop steeply with Mdot^2. Future numerical simulation studies will be needed to test the general thin-shell mixing ansatz for X-ray emission.
description: 12 pages, 4 figures, accepted for publication in MNRAS
Entwicklung von faseroptischen Fluoreszenzsensoren für die Analyse von Biofilmen und deren Mikroumgebung
Creators: name: Schlaugat, Jana
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2019
Subjects: subject: Biofilmanalyse
subject: Fluoreszenzsensor
subject: biogene Fluorophore
subject: pH-Sensor
subject: pO2-Sensor
subject: Dewey Decimal Classification::600 | Technik::660 | Technische Chemie

description: Das Wachstum von Mikroorganismen auf Oberflächen und Grenzflächen im Biofilm ist sehr verbreitet und spielt eine wichtige Rolle in verschiedenen Bereichen wie unter ande-rem den Materialwissenschaften, der Biomedizin und der Abwasseraufbereitung. Auf-grund der inhomogenen Struktur und der Varianz in den Konsortien der Mikroorganis-men stellt die Analyse von Biofilmen allerdings eine große Herausforderung dar. Um eine nicht-invasive online Analyse von Biofilmen zu ermöglichen, wurde ein Fluoreszenz-sensor für die Messung der wichtigsten biologischen Fluorophore (Proteine, NADH und Flavin) in Biofilmen entwickelt. Der Sensor bietet die Möglichkeit, kontinuierlich den Stoffwechselzustand des Biofilms zu analysieren. Besonders hervorzuheben ist die Mess-spitze des Sensors, welche einen Durchmesser von 1 mm aufweist und eine Messung auf der Biofilmoberfläche sowie in der Biofilmstruktur ermöglicht. In dieser Arbeit konnten der Messbereich des Sensors und die Langzeitstabilität bestimmt und die Systemtauglich-keit bestätigt werden. Die Anwendung des Sensors in einem Biofilm wurde schrittweise angenähert. Zunächst wurde der Sensor in Zellsuspensionen und in biofilmähnlichen Strukturen eingesetzt. Abschließend wurde die Bildung eines abwasserbasierten Biofilms mit dem entwickelten Sensor analysiert. Als Proof-of-Principle-Experiment bestätigt dies die Funktionalität des Sensors für den Einsatz in der Biofilmanalyse. Zusätzlich zum Fluoreszenzsensor wurde ein kommerziell erhältliches pH- sowie pO2-Sensorsystem auf die Anwendung in Biofilmen übertragen. Hierzu wurde das System in einer biofilmähnlichen Struktur aus Alginat und anschließend in einer mikrobiellen Brennstoffzelle getestet. Beide Sensorsysteme eignen sich für die Anwendung in Bio-filmkultivierungen. Es hat sich allerdings gezeigt, dass die Messungen in einer biofil-mähnlichen Struktur maßgeblich von der Diffusionslimitierung beeinflusst werden. In Kombination bieten die Sensoren die Möglichkeit, nicht-invasive Biofilmanalysen durchzuführen und so Rückschlüsse auf den Zellzustand und die Prozessumgebung zu erhalten. Ein möglicher Einsatzbereich der Sensoren kann die mikrobielle Brennstoffzelle sein, deren Effizienz maßgeblich durch Sauerstoff und den metabolischen Zustand des Biofilms beeinflusst wird.
Negative sign free formulations of generalized Kitaev models with higher symmetries
Creators: name: Sato, Toshihiro
name: Assaad, Fakher F.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We provide a negative-sign-free formulation of the auxiliary field quantum Monte Carlo algorithm for generalized Kitaev models with higher symmetries. Our formulation is based on the Abrikosov fermion representation of the spin-1/2 degree of freedom and the phase pinning approach [Phys. Rev. B 104, L081106 (2021)]. Enhancing the number of fermion flavors or orbitals from one to $N$ allows one to generalize the inherent $Z_2$ global symmetry to Z$_2$$\times$SU($N$)$_o$. Using this general approach, we study the Z$_2$$\times$SU(2)$_o$ Kitaev-Heisenberg model reflecting the competition between the isotropic Heisenberg exchange and Kitaev-type bond-directional exchange interactions. We show that the symmetry enhancement provides a path to escape frustration and that the spin liquid phases in the original Z$_2$ symmetric model are not present in this model. Nevertheless, the ground-state phase diagram is extremely rich and has points with higher global and local continuous symmetries as well as de-confined quantum critical points.
description: 8 pages, 5 figures
Weyl law for contractive maps
Creators: name: Spina, María E.
name: Rivas, Alejandro M. F.
name: Carlo, Gabriel G.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Quantum Physics (quant-ph)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: We find the Weyl law followed by the eigenvalues of contractive maps. An important property is that it is mainly insensitive to the dimension of the corresponding invariant classical set, the strange attractor. The usual explanation for the fractal Weyl law emergence in scattering systems (i.e., having a projective opening) is based on classical phase space distributions evolved up to the quantum to classical correspondence (Ehrenfest) time. In the contractive case this reasoning fails to describe it. Instead, we conjecture that the support for this behavior is essentially given by the strong non-orthogonality of the eigenvectors of the contractive superoperator.
description: (6 pages, 4 figures)
Einfluss einer Nährstoffkombination mit rot fermentiertem Reis auf die Cholesterolwerte sowie die Homocystein-Konzentration
Creators: name: Heinz, Tina
Publisher: name: Hannover : Gottfried Wilhelm Leibniz Universität Hannover
Year: 2017
Subjects: subject: LDL-Cholesterol
subject: Monacolin K
subject: Homocystein
subject: homocysteine
subject: Dewey Decimal Classification::600 | Technik::610 | Medizin, Gesundheit

description: [no abstract]
Classification of Angle-Symmetric 6R Linkage
Creators: name: Li, Zijia
name: Schicho, Josef
Publisher: name: arXiv
Year: 2013
Subjects: subject: Algebraic Geometry (math.AG)
subject: Robotics (cs.RO)
subject: Symbolic Computation (cs.SC)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: In this paper, we consider a special kind of overconstrained 6R closed linkages which we call angle-symmetric 6R linkages. These are linkages with the property that the rotation angles are equal for each of the three pairs of opposite joints. We give a classification of these linkages. It turns that there are three types. First, we have the linkages with line symmetry. The second type is new. The third type is related to cubic motion polynomials.
Unveiling the double-peak structure of quantum oscillations in the specific heat
Creators: name: Yang, Zhuo
name: Fauque, Benoit
name: Nomura, Toshihiro
name: Shitaokoshi, Takashi
name: Kim, Sunghoon
name: Chowdhury, Debanjan
name: Pribulova, Zuzana
name: Kacmarcik, Jozef
name: Pourret, Alexandre
name: Knebel, Georg
name: Aoki, Dai
name: Klein, Thierry
name: Maude, Duncan K.
name: Marcenat, Christophe
name: Kohama, Yoshimitsu
Publisher: name: arXiv
Year: 2023
Subjects: subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Quantum oscillation phenomenon is an essential tool to understand the electronic structure of quantum matter. Here we report a systematic study of quantum oscillations in the electronic specific heat $C_{el}$ in natural graphite. We show that the crossing of a single spin Landau level and the Fermi energy give rise to a double-peak structure, in striking contrast to the single peak expected from Lifshitz-Kosevich theory. Intriguingly, the double-peak structure is predicted by the kernel term for $C_{el}/T$ in the free electron theory. The $C_{el}/T$ represents a spectroscopic tuning fork of width 4.8 $k_B T$ which can be tuned at will to resonance. Using a coincidence method, the double-peak structure can be used to accurately determine the Lande $g$-factor of quantum materials. More generally, the tuning fork can be used to reveal any peak in fermionic density of states tuned by magnetic field, such as Lifshitz transition in heavy-fermion compounds.
description: 22 pages, 5 figures, Accepted in Nature Communications