cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Directions for model building from asymptotic safety
Creators: name: Bond, Andrew D.
name: Hiller, Gudrun
name: Kowalska, Kamila
name: Litim, Daniel F.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Building on recent advances in the understanding of gauge-Yukawa theories we explore possibilities to UV-complete the Standard Model in an asymptotically safe manner. Minimal extensions are based on a large flavor sector of additional fermions coupled to a scalar singlet matrix field. We find that asymptotic safety requires fermions in higher representations of $SU(3)_C\times SU(2)_L$. Possible signatures at colliders are worked out and include $R$-hadron searches, diboson signatures and the evolution of the strong and weak coupling constants.
description: 52 pages, 23 figures, 7 tables, published version. v2: clarifications and results (weak sector, Fig 18) added, some plots updated post-Moriond 2017, typos removed
Parameter Distributions of Binary Black Hole Mergers Near Supermassive Black Holes as Seen by Advanced Gravitational Wave Detectors
Creators: name: Gondán, László
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The environment surrounding supermassive black holes (SMBHs) in galactic nuclei (GNs) is expected to harbour stellar-mass binary black hole (BBH) populations. These binaries were suggested to form a hierarchical triple system with the SMBH, and gravitational perturbations from the SMBH can enhance the mergers of BBHs through Lidov-Kozai (LK) oscillations. Previous studies determined the expected binary parameter distribution for this merger channel in single GNs. Here we account for the different spatial distribution and mass distribution models of BBHs around SMBHs and perform direct high-precision regularized N-body simulations, including Post-Newtonian (PN) terms up to order PN2.5, to model merging BBH populations in single GNs. We use a full inspiral-merger-ringdown waveform model of BBHs with nonzero eccentricities and take into account the observational selection effect to determine the parameter distributions of LK-induced BBHs detected with a single advanced gravitational-wave (GW) detector from all GNs in the Universe. We find that the detected mergers' total binary mass distribution is tilted towards lower masses, and the mass ratio distribution is roughly uniform. The redshift distribution peaks between ~0.15-0.55, and the vast majority of binaries merge within redshift ~1.1. The fraction of binaries entering the LIGO/Virgo/KAGRA band with residual eccentricities >0.1 is below ~10%. We identify a negative correlation between residual eccentricity and mass parameters and a negative correlation between residual eccentricity and source distance. Our results for the parameter distributions and correlations among binary parameters may make it possible to disentangle this merger channel from other BBH merger channels statistically.
description: 16 pages, 2 figures, 3 tables, accepted by MNRAS
Gravitational form factors of the baryon octet with flavor SU(3) symmetry breaking
Creators: name: Won, Ho-Yeon
name: Kim, June-Young
name: Kim, Hyun-Chul
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We investigate the gravitational form factors of the baryon octet within the framework of the SU(3) chiral quark-soliton model, considering the effects of flavor SU(3) symmetry breaking, and the corresponding energy-momentum tensor distributions. We examine the effects of flavor SU(3) symmetry breaking to the mass, angular momentum, pressure, and shear force distributions of the baryon octet. We first find that a heavier baryon is energetically more compact than a lighter one. For the spin distributions of the baryon octet, they are properly normalized to their spins and are decomposed into the flavor-singlet axial charge and the orbital angular momentum even when the flavor SU(3) symmetry is broken. While the effects of the flavor SU(3) symmetry breaking differently contribute to the angular momentum distributions for the octet baryons, they are found to be rather small. The spin and orbital angular momentum almost equally contribute to the angular momentum distributions for the octet baryons. We also estimate the effects of the flavor SU(3) symmetry breaking to the pressure and shear force distributions. Interestingly, even if we include the effects of the SU(3) flavor symmetry breaking, the shear force distributions are kept to be positive over $r$. It indicates that the Polyakov & Schweitzer local stability condition is kept to be intact with the flavor SU(3) symmetry broken. Lastly, we discuss how much the gravitational form factors vary with the effects of flavor SU(3) symmetry breaking considered.
description: 27 pages, 8 figures
title: The story of Sc in bauxite residues and its journey from ore to waste to value
Creators: name: Gentzmann, Marie C.
name: Adam, Christian
Publisher: name: Deutsche Geologische Gesellschaft - Geologische Vereinigung e.V. (DGGV)
Year: 2022

description:
Bauxite residue (BR) is a massive waste stream generated worldwide from Alumina production that is intensely studied for its potential reuse and as a secondary resource for various metals. More recently the recovery of the technology metal Scandium (Sc), which can be enriched in BRs, has attracted the interest of research and industry. Sc enrichment in BR was discovered more than 25 years ago, however there is a lack of comprehensive knowledge about its association and distribution. Geochemical and mineralogical insights that provide a connection between the Sc occurrence in the primary bauxite ore and the BR are scarce.

In this study, we present the results of detailed mineralogical investigations on BRs of different geological backgrounds and on the Sc behavior during the recovery process by leaching. The results were determined by combining wet chemical, microtextural and structural analyses with statistical design of experiments. They provide an understanding of how the Sc association changes from ore to waste depending on the primary bauxite and the chosen leaching conditions. The primary bauxite and the atmospheric conditions during bauxitization determine how Sc is distributed in the BR. BRs derived from karstic bauxites formed under partly reducing conditions are hence more prone to contain higher mass fractions of easily leachable Sc than BRs derived from lateritic bauxites. The recovery achieved by leaching therefore depends on the Sc distribution and will furthermore determine the viability of Sc recovery from BR. The research was funded by the EU's H2020 SCALE program under GA No. 730105.
Correlation induced electron-hole asymmetry in quasi-2D iridates
Creators: name: Pärschke, Ekaterina M.
name: Wohlfeld, Krzysztof
name: Foyevtsova, Kateryna
name: Brink, Jeroen van den
Publisher: name: arXiv
Year: 2017
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We determine the motion of a charge (hole or electron) added to the Mott insulating, antiferromagnetic (AF) ground-state of quasi-2D iridates such as Ba 2 IrO 4 or Sr 2 IrO 4 . We show that correlation effects, calculated within the self-consistent Born approximation, render the hole and electron case very different. An added electron forms a spin-polaron, which closely resembles the well-known cuprates, but the situation of a removed electron is far more complex. Many-body 5d 4 configurations form which can be singlet and triplets of total angular momentum J and strongly affect the hole motion between AF sublattices. This not only has important ramifications for the interpretation of (inverse-)photoemission experiments of quasi-2D iridates but also demonstrates that the correlation physics in electron- and hole-doped iridates is fundamentally different.
description: 11 pages main text, 11 pages supplementary, 10 figures
Quantum propagation across cosmological singularities
Creators: name: Gielen, Steffen
name: Turok, Neil
Publisher: name: arXiv
Year: 2016
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The initial singularity is the most troubling feature of the standard cosmology, which quantum effects are hoped to resolve. In this paper, we study quantum cosmology with conformal (Weyl) invariant matter. We show it is natural to extend the scale factor to negative values, allowing a large, collapsing Universe to evolve across a quantum "bounce" into an expanding Universe like ours. We compute the Feynman propagator for Friedmann-Robertson-Walker backgrounds exactly, identifying curious pathologies in the case of curved (open or closed) universes. We then include anisotropies, fixing the operator ordering of the quantum Hamiltonian by imposing covariance under field redefinitions and again finding exact solutions. We show how complex classical solutions allow one to circumvent the singularity while maintaining the validity of the semiclassical approximation. The simplest isotropic universes sit on a critical boundary, beyond which there is qualitatively different behavior, with potential for instability. Additional scalars improve the theory's stability. Finally, we study the semiclassical propagation of inhomogeneous perturbations about the flat, isotropic case, at linear and nonlinear order, showing that, at least at this level, there is no particle production across the bounce. These results form the basis for a promising new approach to quantum cosmology and the resolution of the big bang singularity.
description: 27 pages, 7 figures, APS style, ancillary files include calculations presented in sections IV and VI; v2: minor changes to match published version
An astrometric mass estimate for asteroid (223) Rosa
Creators: name: Kretlow, M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: Outer main belt asteroid (223) Rosa is a possible flyby target of opportunity for ESA's (European Space Agency) JUpiter ICy moons Explorer (JUICE) mission when passing the asteroid belt on the way to Jupiter. The very low albedo and the featureless red spectra indicate a P-type asteroid in the Tholen taxonomy, though the yet known bulk density did not match very well this classification. Aim of this work was to derive new estimates for the mass and for the bulk density for (223) Rosa. The mass of Rosa was derived by analyzing the gravitational deflection of small `test' asteroids which had a close encounter with Rosa in the past. To find such events suitable for the mass determination, an encounter search with about 900,000 asteroids over the time span $1980-2030$ was performed. Three encounters were identified from which two independent mass estimates for Rosa were derived: $M = (5.32 \pm 2.17) \times 10^{17}$ kg and $M = (3.15 \pm 1.14) \times 10^{17}$ kg, respectively. The weighted mean is $M = (3.62 \pm 1.25) \times 10^{17}$ kg. This yields to a bulk density of $ρ= 1.2 \pm 0.5 \mathrm{\,g\,cm^{-3}}$, when adopting an effective diameter of $D = 83 \pm 8$ km. This bulk density estimate is consistent with typical densities for Tholen taxonomy P-type asteroids.
description: 6 pages, 4 figures, accepted for publication in A&A
A possible 250-second X-ray quasi-periodicity in the fast blue optical transient AT2018cow
Creators: name: Zhang, Wenjie
name: Shu, Xinwen
name: Chen, Jin-Hong
name: Sun, Luming
name: Shen, Rong-Feng
name: Tao, Lian
name: Chen, Chun
name: Jiang, Ning
name: Dou, LiMing
name: Qin, Ying
name: Zhang, Xue-Guang
name: Zhang, Liang
name: Qu, Jinlu
name: Wang, Tinggui
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The fast blue optical transients (FBOTs) are a new population of extragalactic transients of unclear physical origin. A variety of mechanisms have been proposed including failed supernova explosion, shock interaction with a dense medium, young magnetar, accretion onto a compact object, and stellar tidal disruption event, but none is conclusive. Here we report the discovery of a possible X-ray quasi-periodicity signal with a period of $\sim$250 second (at a significance level of 99.76%) in the brightest FBOT AT2018cow through the analysis of XMM-Newton/PN data. The signal is independently detected at the same frequency in the average power density spectrum from data taken from the Swift telescope, with observations covering from 6 to 37 days after the optical discovery, though the significance level is lower (94.26%). This suggests that the QPO frequency may be stable over at least 1.1$\times$ 10$^{4}$ cycles. Assuming the $\sim$250 second QPO to be a scaled-down analogue of that typically seen in stellar mass black holes, a black hole mass of $\sim10^{3}-10^{5}$ solar masses could be inferred. The overall X-ray luminosity evolution could be modeled with the stellar tidal disruption by a black hole of $\sim10^4$ solar masses, providing a viable mechanism to produce AT2018cow. Our findings suggest that other bright FBOTs may also harbor intermediate-mass black holes.
description: 18 pages, 10 figures. Accepted for publication in Research in Astronomy and Astrophysics
Connecting the first galaxies with ultra faint dwarfs in the Local Group: chemical signatures of Population~III stars
Creators: name: Jeon, Myoungwon
name: Besla, Gurtina
name: Bromm, Volker
Publisher: name: arXiv
Year: 2017
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We investigate the star formation history and chemical evolution of isolated analogues of Local Group (LG) ultra faint dwarf galaxies (UFDs; stellar mass range of 10^2 solar mass < M_star <10^5 solar mass) and gas rich, low mass dwarfs (Leo P analogs; stellar mass range of 10^5 solar mass < M_star <10^6 solar mass). We perform a suite of cosmological hydrodynamic zoom-in simulations to follow their evolution from the era of the first generation of stars down to z=0. We confirm that reionization, combined with supernova (SN) feedback, is primarily responsible for the truncated star formation in UFDs. Specifically, haloes with a virial mass of M_vir < 2 x 10^9 solar mass form> 90\% of stars prior to reionization. Our work further demonstrates the importance of Population~III (Pop~III) stars, with their intrinsically high $\rm [C/Fe]$ yields, and the associated external metal-enrichment, in producing low-metallicity stars ($\rm [Fe/H]\lesssim-4$) and carbon-enhanced metal-poor (CEMP) stars. We find that UFDs are composite systems, assembled from multiple progenitor haloes, some of which hosted only Population~II (Pop~II) stars formed in environments externally enriched by SNe in neighboring haloes, naturally producing, extremely low-metallicity Pop~II stars. We illustrate how the simulated chemical enrichment may be used to constrain the star formation histories (SFHs) of true observed UFDs. We find that Leo P analogs can form in haloes with M_vir ~ 4 x 10^9 solar mass (z=0). Such systems are less affected by reionization and continue to form stars until z=0, causing higher metallicity tails. Finally, we predict the existence of extremely low-metallicity stars in LG UFD galaxies that preserve the pure chemical signatures of Pop~III nucleosynthesis.
description: 22 pages, 13 figures, Accepted for publication in ApJ
Rhombic Grids Reduce the Number of Voxels in Fast Pulse-Echo Ultrasound Imaging
Creators: name: Schiffner, Martin F.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Medical Physics (physics.med-ph)
subject: Image and Video Processing (eess.IV)
subject: Signal Processing (eess.SP)
subject: FOS: Physical sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Ultrafast imaging modes, such as coherent plane-wave compounding (CPWC), capture a large field of view in a single pulse-echo measurement using parallel receive focusing. The number of foci or, equivalently, the number of volume elements (voxels) in the image determines the computational costs and the memory consumption of the image formation. Herein, 120° rhombic grids are proposed to specify the voxel positions and reduce the number of voxels in comparison to orthogonal grids. The proposed grids derive from the bivariate sampling theorem and the spectral properties of the images formed by the delay-and-sum algorithm in CPWC. A phantom experiment validated the proposed grids and showed reductions in the number of voxels by 81.4 % and 14.7 % in comparison to the usual and optimal orthogonal grids, respectively. Mean structural similarity indices above 96.6 % and relative root mean-squared errors below 6.8 % confirmed the visual equivalence of all images after interpolations to the usual orthogonal grid.
description: 5 pages, 4 figures, 1 table; added journal reference, no other changes
The relation between globular cluster systems and supermassive black holes in spiral galaxies III. The link to the $M_\bullet-M_\ast$ correlation
Creators: name: González-Lópezlira, Rosa A.
name: Lomelí-Núñez, Luis
name: Ordenes-Briceño, Yasna
name: Loinard, Laurent
name: Gwyn, Stephen
name: Alamo-Martínez, Karla
name: Bruzual, Gustavo
name: Lançon, Ariane
name: Puzia, Thomas H.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We continue to explore the relationship between globular cluster total number, $N_{\rm GC}$, and central black hole mass, $M_\bullet$, in spiral galaxies. We present here results for the Sab galaxies NGC 3368, NGC 4736 (M 94) and NGC 4826 (M 64), and the Sm galaxy NGC 4395. The globular cluster (GC) candidate selection is based on the ($u^*$ - $i^\prime$) versus ($i^\prime$ - $K_s$) color-color diagram, and $i^\prime$-band shape parameters. We determine the $M_\bullet$ versus $N_{\rm GC}$ correlation for these spirals, plus NGC 4258, NGC 253, M 104, M 81, M 31, and the Milky Way. We also redetermine the correlation for the elliptical sample in Harris, Poole, & Harris (2014), with updated galaxy types from Sahu et al. 2019b. Additionally, we derive total stellar galaxy mass, $M_\ast$, from its two-slope correlation with $N_{\rm GC}$ (Hudson, Harris, & Harris 2014), and fit $M_\bullet$ versus $M_\ast$ for both spirals and ellipticals. We obtain log $M_\bullet \propto$ (1.01 $\pm$ 0.13) log $N_{\rm GC}$ for ellipticals, and log $M_\bullet \propto$ (1.64 $\pm$ 0.24) log $N_{\rm GC}$ for late type galaxies (LTG). The linear $M_\bullet$ versus $N_{\rm GC}$ correlation in ellipticals could be due to statistical convergence through mergers, but not the much steeper correlation for LTG. However, in the $M_\bullet$ versus total stellar mass ($M_\ast$) parameter space, with $M_\ast$ derived from its correlation with $N_{\rm GC}$, $M_\bullet \propto$ (1.48 $\pm$ 0.18) log $M_\ast$ for ellipticals, and $M_\bullet \propto$ (1.21 $\pm$ 0.16) log $M_\ast$ for LTG. The observed agreement between ellipticals and LTG in this parameter space may imply that black holes and galaxies co-evolve through "calm" accretion, AGN feedback, and other secular processes.
description: 38 pages, 18 figures, 19 tables; accepted for publication in The Astrophysical Journal. arXiv admin note: text overlap with arXiv:1612.05655
Topological superconductivity from doping a triplet quantum spin liquid in a flat band system
Creators: name: López, Manuel Fernández
name: Powell, Ben J.
name: Merino, Jaime
Publisher: name: arXiv
Year: 2022
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We explore superconductivity in strongly interacting electrons on a decorated honeycomb lattice (DHL). An easy-plane ferromagnetic interaction arises from spin-orbit coupling in the Mott insulating phase, which favors a triplet resonance valence bond spin liquid state. Hole doping leads to partial occupation of a flat band and to triplet superconductivity. The order parameter is highly sensitive to the doping level and the interaction parameters, with $p+ip$, $f$ and $p+f$ superconductivity found, as the flat band leads to instabilities in multiple channels. Typically, first order transitions separate different superconducting phases, but a second order transition separates two time reversal symmetry breaking $p+ip$ phases with different Chern numbers ($ν=0$ and 1). The Majorana edge modes in the topological ($ν=1$) superconductor are almost localized due to the strong electronic correlations in a system with a flat band at the Fermi level. This suggests that these modes could be useful for topological quantum computing. The `hybrid' $p+f$ state does not require two phase transitions as temperature is lowered. This is because the symmetry of the model is lowered in the $p$-wave phase, allowing arbitrary admixtures of $f$-wave basis functions as overtones. We show that the multiple sites per unit cell of the DHL, and hence multiple bands near the Fermi energy, lead to very different nodal structures in real and reciprocal space. We emphasize that this should be a generic feature of multi-site/multi-band superconductors.
description: 18 pages, 16 figures
Momentum coupling in non-Markovian Quantum Brownian motion
Creators: name: Ferialdi, Luca
name: Smirne, Andrea
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We consider a model of non-Markovian Quantum Brownian motion that consists of an harmonic oscillator bilinearly coupled to a thermal bath, both via its position and momentum operators. We derive the master equation for such a model and we solve the equations of motion for a generic Gaussian system state. We then investigate the resulting evolution of the first and second moments for both an Ohmic and a super-Ohmic spectral density. In particular, we show that, irrespective of the specific form of the spectral density, the coupling with the momentum enhances the dissipation experienced by the system, accelerating its relaxation to the equilibrium, as well as modifying the asymptotic state of the dynamics. Eventually, we characterize explicitly the non-Markovianity of the evolution, using a general criterion which relies on the positivity of the master equation coefficients.
KIC 7955301: a hierarchical triple system with eclipse timing variations and an oscillating red giant
Creators: name: Gaulme, P.
name: Borkovits, T.
name: Appourchaux, T.
name: Pavlovski, K.
name: Spada, F.
name: Gehan, C.
name: Ong, J.
name: Miglio, A.
name: Tkachenko, A.
name: Mosser, B.
name: Vrard, M.
name: Benbakoura, M.
name: Chojnowski, S. D.
name: Perkins, J.
name: Hedlund, A.
name: Jackiewicz, J.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: KIC 7955301 is a hierarchical triple system with eclipse timing and depth variations discovered by the Kepler mission. It is composed of a non-eclipsing primary star at the bottom of the red giant branch on a 209-day orbit with a K/G-type main-sequence inner eclipsing binary, orbiting in 15.3 days. This system was noted for the large amplitude of its eclipse timing variations (4 hours), and the clear solar-like oscillations of the red-giant component, including p-modes of degree up to l=3 and mixed l=1 modes. The system is a single-lined spectroscopic triple. We perform a dynamical model by combining the Kepler photometric data, eclipse timing variations, and radial-velocity data obtained at Apache Point (ARCES) and Haute Provence (SOPHIE) observatories. The dynamical mass of the red-giant is determined with a 2% precision at 1.30 (+0.03,-0.02) solar mass. We perform asteroseismic modeling based on the global seismic parameters and on the individual frequencies. Both methods lead to a mass of the red giant that matches the dynamical mass within the uncertainties. Asteroseismology also reveals the rotation rate of the core (15 days), the envelope (150 days), and the inclination (75 deg) of the red giant. Three different approaches lead to an age between 3.3 and 5.8 Gyr, which highlights the difficulty of determining stellar ages despite the exceptional wealth of available information. On short timescales, the inner binary exhibits eclipses with varying depths during a 7.3-year long interval, and no eclipses during the consecutive 11.9 years. This is why Kepler could detect its eclipses, TESS will not, and the future ESA PLATO mission should. Over the long term, the system owes its evolution to the evolution of its individual components. It could end its current smooth evolution by merging by the end of the red giant or the asymptotic giant branch of the primary star.
description: Accepted in A&A, 25 pages, 17 figures, 7 tables
Heavy tailed approximate identities and $σ$-stable Markov kernels
Creators: name: Aimar, Hugo
name: Gómez, Ivana
name: Morana, Federico
Publisher: name: arXiv
Year: 2017
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 42B25, 60G52, 28C99

description: The aim of this paper is to present some results relating the properties of stability, concentration and approximation to the identity of convolution through not necessarily mollification type families of heavy tailed Markov kernels. A particular case is provided by the kernels $K_t$ obtained as the $t$ mollification of $L^{σ(t)}$ selected from the family $\mathcal{L}=\{L^σ: \widehat{L^σ}(ξ)=e^{-|ξ|^σ},0
description: 20 pages, minor typos corrected, this the final version, to appear in Potential Analysis
Ironing the folds: The phase space chevrons of a GSE-like merger as a dark matter subhalo detector
Creators: name: Davies, Elliot Y.
name: Vasiliev, Eugene
name: Belokurov, Vasily
name: Evans, N. Wyn
name: Dillamore, Adam M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Recent work uncovered features in the phase space of the Milky Way's stellar halo which may be attributed to the last major merger. When stellar material from a satellite is accreted onto its host, it phase mixes and appears finely substructured in phase space. For a high-eccentricity merger, this substructure most clearly manifests as numerous wrapping chevrons in $(v_r, r)$ space, corresponding to stripes in $(E, θ_r)$ space. We introduce the idea of using this substructure as an alternative subhalo detector to cold stellar streams. We simulate an N-body merger akin to the GSE and assess the impact of subhaloes on these chevrons. We examine how their deformation depends on the mass, pericentre, and number of subhaloes. To quantify the impact of perturbers, we utilise the appearance of chevrons in $(E, θ_r)$ space to introduce a new quantity -- the ironing parameter. We show that: (1) a single flyby of a massive ($\sim 10^{10}$ M$_{\odot}$) subhalo with pericentre comparable to, or within, the shell's apocentre smooths out the substructure, (2) a single flyby of a low mass ($\lesssim 10^8$ M$_{\odot}$) has negligible effect, (3) multiple flybys of subhalos derived from a subhalo mass function between $10^7-10^{10}$ M$_{\odot}$ cause significant damage if deep within the potential, (4) the effects of known perturbers (e.g. Sagittarius) should be detectable and offer constraints on their initial mass. The sensitivity to the populations of subhaloes suggests that we should be able to place an upper limit on the Milky Way's subhalo mass function.
description: 18 pages, 20 figures, accepted by MNRAS
Value Function Decomposition in Markov Recommendation Process
Creators: name: Wang, Xiaobei
name: Liu, Shuchang
name: Cai, Qingpeng
name: Li, Xiang
name: Hu, Lantao
name: li, Han
name: Xie, Guangming
Publisher: name: arXiv
Year: 2025
Subjects: subject: Information Retrieval (cs.IR)
subject: FOS: Computer and information sciences
subject: H.3.3

description: Recent advances in recommender systems have shown that user-system interaction essentially formulates long-term optimization problems, and online reinforcement learning can be adopted to improve recommendation performance. The general solution framework incorporates a value function that estimates the user's expected cumulative rewards in the future and guides the training of the recommendation policy. To avoid local maxima, the policy may explore potential high-quality actions during inference to increase the chance of finding better future rewards. To accommodate the stepwise recommendation process, one widely adopted approach to learning the value function is learning from the difference between the values of two consecutive states of a user. However, we argue that this paradigm involves a challenge of Mixing Random Factors: there exist two random factors from the stochastic policy and the uncertain user environment, but they are not separately modeled in the standard temporal difference (TD) learning, which may result in a suboptimal estimation of the long-term rewards and less effective action exploration. As a solution, we show that these two factors can be separately approximated by decomposing the original temporal difference loss. The disentangled learning framework can achieve a more accurate estimation with faster learning and improved robustness against action exploration. As an empirical verification of our proposed method, we conduct offline experiments with simulated online environments built on the basis of public datasets.
description: 12 pages, 9 figures
T-Branes at the Limits of Geometry
Creators: name: Anderson, Lara B.
name: Heckman, Jonathan J.
name: Katz, Sheldon
name: Schaposnik, Laura P.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Algebraic Geometry (math.AG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: Singular limits of 6D F-theory compactifications are often captured by T-branes, namely a non-abelian configuration of intersecting 7-branes with a nilpotent matrix of normal deformations. The long distance approximation of such 7-branes is a Hitchin-like system in which simple and irregular poles emerge at marked points of the geometry. When multiple matter fields localize at the same point in the geometry, the associated Higgs field can exhibit irregular behavior, namely poles of order greater than one. This provides a geometric mechanism to engineer wild Higgs bundles. Physical constraints such as anomaly cancellation and consistent coupling to gravity also limit the order of such poles. Using this geometric formulation, we unify seemingly different wild Hitchin systems in a single framework in which orders of poles become adjustable parameters dictated by tuning gauge singlet moduli of the F-theory model.
description: v2: 65 pages, 6 figures, clarifications added
Renormalization group flows of Hamiltonians using tensor networks
Creators: name: Bal, Matthias
name: Mariën, Michaël
name: Haegeman, Jutho
name: Verstraete, Frank
Publisher: name: arXiv
Year: 2017
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: High Energy Physics - Lattice (hep-lat)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: A renormalization group flow of Hamiltonians for two-dimensional classical partition functions is constructed using tensor networks. Similar to tensor network renormalization ([G. Evenbly and G. Vidal, Phys. Rev. Lett. 115, 180405 (2015)], [S. Yang, Z.-C. Gu, and X.-G Wen, Phys. Rev. Lett. 118, 110504 (2017)]) we obtain approximate fixed point tensor networks at criticality. Our formalism however preserves positivity of the tensors at every step and hence yields an interpretation in terms of Hamiltonian flows. We emphasize that the key difference between tensor network approaches and Kadanoff's spin blocking method can be understood in terms of a change of local basis at every decimation step, a property which is crucial to overcome the area law of mutual information. We derive algebraic relations for fixed point tensors, calculate critical exponents, and benchmark our method on the Ising model and the six-vertex model.
description: accepted version for Phys. Rev. Lett, main text: 5 pages, 3 figures, appendices: 9 pages, 1 figure
Dark-Photon Search using Data from CRESST-II Phase 2
Creators: name: Angloher, G.
name: Bauer, P.
name: Bento, A.
name: Bucci, C.
name: Canonica, L.
name: Defay, X.
name: Erb, A.
name: Feilitzsch, F. v.
name: Iachellini, N. Ferreiro
name: Gorla, P.
name: Gütlein, A.
name: Hauff, D.
name: Jochum, J.
name: Kiefer, M.
name: Kluck, H.
name: Kraus, H.
name: Lanfranchi, J. C.
name: Loebell, J.
name: Mancuso, M.
name: Münster, A.
name: Pagliarone, C.
name: Petricca, F.
name: Potzel, W.
name: Pröbst, F.
name: Puig, R.
name: Reindl, F.
name: Schäffner, K.
name: Schieck, J.
name: Schönert, S.
name: Seidel, W.
name: Stodolsky, L.
name: Strandhagen, C.
name: Strauss, R.
name: Tanzke, A.
name: Thi, H. H. Trinh
name: Türkoǧlu, C.
name: Uffinger, M.
name: Ulrich, A.
name: Usherov, I.
name: Wawoczny, S.
name: Willers, M.
name: Wüstrich, M.
name: Zöller, A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: Identifying the nature and origin of dark matter is one of the major challenges for modern astro and particle physics. Direct dark-matter searches aim at an observation of dark-matter particles interacting within detectors. The focus of several such searches is on interactions with nuclei as provided e.g. by Weakly Interacting Massive Particles. However, there is a variety of dark-matter candidates favoring interactions with electrons rather than with nuclei. One example are dark photons, i.e., long-lived vector particles with a kinetic mixing to standard-model photons. In this work we present constraints on this kinetic mixing based on data from CRESST-II Phase 2 corresponding to an exposure before cuts of 52\,kg-days. These constraints improve the existing ones for dark-photon masses between 0.3 and 0.7\,keV/c$^2$.
description: submitted EPJ C
title: Optimized sequential extraction for chromium from laterite deposits
Creators: name: Delina, Ruth Esther G.
name: Perez, Jeffrey Paulo H.
name: Stammeier, Jessica A.
name: Blukis, Roberts
name: Benning, Liane G.
Publisher: name: Deutsche Geologische Gesellschaft - Geologische Vereinigung e.V. (DGGV)
Year: 2022

description:
Chromium is naturally enriched in nickel laterite deposits, the world’s main source of nickel. Both of its main redox species (III and VI) are important, but Cr(VI) is the more mobile, toxic and carcinogenic pollutant species. It is often leached from nickel laterites, potentially contaminating ground- and drinking waters. Thus, it is crucial to quantify the partitioning for chromium in the laterite host phases because these associations dictate the potential mobility, bioavailability and toxicity of chromium. Although such assessments are usually evaluated through sequential extraction procedures (SEP), so far, no SEP has been designed, tested and validated for chromium partitioning from laterites that are typically dominated by iron (oxyhydr)oxides.

Here we evaluated existing SEPs and optimized and validated a new scheme. For our optimized SEP, we tested the efficiency of various extractants on Cr- and Fe-bearing phases (e.g., goethite, chromite) commonly present in nickel laterites. We then applied our SEP on nickel laterites from the Philippines. Our results revealed that Cr recovery was up to 10x higher compared to non-Ni laterite optimized standard SEPs. The developed SEP efficiently dissolved crystalline Fe phases recovering 25-34% of the total chromium. Existing SEP schemes only recovered 2-18% because they only partially dissolved the host goethite and hematite. Our SEP also prevented the overestimation of organic matter bound Cr. It could also quantify strongly adsorbed chromium oxyanions. These improvements provide a better quantification of different chromium hosts and thus improve our understanding of the potential environmental impacts of chromium in mining-impacted lateritic areas.
Discovery of a probable very fast extragalactic nova in a symbiotic binary
Creators: name: Modiano, David
name: Wijnands, Rudy
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Very fast novae are novae which evolve exceptionally quickly (on timescales of only days). Due to their rapid evolution, very fast novae are challenging to detect and study, especially at early times. Here we report the discovery, which was made as part of our Transient UV Objects project, of a probable very fast nova in the nearby spiral galaxy NGC 300. We detected the rise to the peak (which is rarely observed for very fast novae) in the near-ultraviolet (NUV), with the first detection just ~2 hours after the eruption started. The peak and early stages of the decay were also observed in UV and optical bands. The source rapidly decayed by 2 NUV magnitudes within 3.5 days, making it one of the fastest novae known. In addition, a likely quiescent counterpart was found in archival near-infrared Spitzer and VIRCAM images but not in any deep optical and UV observations, indicating a very red spectral shape in quiescence. The outburst and quiescence properties suggest that the system is likely a symbiotic binary. We discuss this new transient in the context of very fast novae in general and specifically as a promising supernova Type Ia progenitor candidate, due to its very high inferred WD mass (~1.35 Ms; determined by comparing this source to other very fast novae).
description: 10 pages, 6 figures. Accepted for publication in Astronomy & Astrophysics
Post-Newtonian parameter $γ$ and the deflection of light in ghost-free massive bimetric gravity
Creators: name: Hohmann, Manuel
Publisher: name: arXiv
Year: 2017
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We consider the parametrized post-Newtonian (PPN) limit of ghost-free massive bimetric gravity with two mutually non-interacting matter sectors coupled to the two metrics. Making use of a gauge-invariant differential decomposition of the metric perturbations, we solve the field equations up to the linear PPN order for a static, point-like mass source. From the result we derive the PPN parameter $γ$ for spherically symmetric systems, which describes the gravitational deflection of light by visible matter. By a comparison to its value measured in the solar system we obtain bounds on the parameters of the theory. We further discuss the deflection of light by dark matter and find an agreement with the observed light deflection by galaxies. We finally speculate about a possible explanation for the observed distribution of dark matter in galactic mergers such as Abell 520 and Abell 3827.
description: 36 pages, 1 figure; journal version
Program of a Conference held at New York University's Center for Media, Culture, and History, New York City, N.Y., 2001
Publisher: name: Columbia University
Year: 2020
Subjects: Investigative reporting
Congresses and conventions

description: Program of the Conference on "Tibetan Dispatches: Reporting on the Roof of the World" held by New York University's Center for Media, Culture, and History.
A relative tensor product of subfactors over a modular tensor category
Creators: name: Kawahigashi, Yasuyuki
Publisher: name: arXiv
Year: 2016
Subjects: subject: Operator Algebras (math.OA)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We define and study a certain relative tensor product of subfactors over a modular tensor category. This gives a relative tensor product of two completely rational heterotic full local conformal nets with trivial superselection structures over a common chiral representation category. In particular, we have a new realization of fusion rules of modular invariants. This also gives a mathematical definition of a composition of two gapped domain walls between topological phases.
description: 9 pages
Nearly Critical Holographic Superfluids
Creators: name: Donos, Aristomenis
name: Kailidis, Polydoros
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the nearly critical behaviour of holographic superfluids at finite temperature and chemical potential in their probe limit. This allows us to examine the coupled dynamics of the full complex order parameter with the charge density of the system. We derive an effective theory for the long wavelength limit of the gapless and pseudo-gapped modes by using analytic techniques in the bulk. We match our construction with Model F in the classification of Hohenberg and Halperin and compute the complex dissipative kinetic transport coefficient in terms of thermodynamics and black hole horizon data. We carry out an analysis of the corresponding modes and argue that at finite density the dispersion relations are discontinuous between the normal and the broken phase. We compare and contrast our results with earlier numerical work.
description: 39 pages, 4 figures, Typos fixed, Version to appear at JHEP
Quantum mechanical look at the radioactive-like decay of metastable dark energy
Creators: name: Szydlowski, Marek
name: Stachowski, Aleksander
name: Urbanowski, Krzysztof
Publisher: name: arXiv
Year: 2017
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We derive the Shafieloo, Hazra, Sahni and Starobinsky (SHSS) phenomenological formula for the radioactive-like decay of metastable dark energy directly from the quantum mechanics principles. For this aim we use the Fock-Krylov theory of quantum unstable states. We obtain deeper insight on the decay process as having three basic phases: the phase of radioactive decay, the next phase of damping oscillations, and finally the phase of power law decaying. We consider the cosmological model with matter and dark energy in the form of decaying metastable dark energy and study its dynamics in the framework of non-conservative cosmology with an interacting term determined by the running cosmological parameter. We study cosmological implications of metastable dark energy and estimate the characteristic time of ending of the radioactive-like decay epoch as 22296 of the present age of the Universe. We also confront the model with astronomical data which show that the model is in good agreement with the observations. Our general conclusion is that we are living in the epoch of the radioactive-like decay of metastable dark energy which is a relict of the quantum age of the Universe.
description: v2: 14 pages, 7 figures, change of title, new discussion of crossover time and new result on characteristic time of ending of radioactive-like decay epoch
Optimising the H$α$ index for the identification of activity signals in FGK stars. Improvement of the correlation between H$α$ and CaII H&K
Creators: name: da Silva, J. Gomes
name: Bensabat, A.
name: Monteiro, T.
name: Santos, N. C.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: In this work we investigate the effect of the H$α$ bandpass width in the correlation between the CaII H&K and H$α$ indices with the aim of improving the H$α$ index to better identify and model the signals coming from activity variability. We used a sample of 152 FGK dwarfs observed with HARPS for more than 13 years with enough cadence to be able to detect rotational modulations and cycles in activity proxies. We calculated the CaII H&K and H$α$ activity indices using a range of bandwidths for H$α$ between 0.1 and 2.0 Ang. We studied the correlation between the indices time series at long and short timescales and analysed the impact of stellar parameters, activity level and variability on the correlations. The correlation between CaII H&K and H$α$ both at short and long timespans is maximised when using narrow H$α$ bandwidths, with a maximum at 0.6 Ang. For some inactive stars, as the activity level increases, the flux in the H$α$ line core increases while the flux in the line wings decreases as the line becomes shallower and broader. The balance between these fluxes can cause stars to show the negative correlations observed in the literature when using a wide bandwidth on H$α$. These anti-correlations may become positive correlations if using the 0.6 Ang bandwidth. Calculating the H$α$ index using a bandpass of 0.6 Ang maximises the correlation between CaII H&K and H$α$ both at short and long timescales. On the other hand, the use of the broader 1.6 Ang, generally used in exoplanet detection to identify stellar activity signals, degrades the signal by including the flux in the line wings. In face to these results we strongly recommend the use of a 0.6 Ang bandwidth when computing the H$α$ index for the identification of activity rotational modulation and magnetic cycle signals in solar-type stars. (Abridged)
description: 25 pages, 14 figures, 3 tables, accepted for publication in A&A
Propagating charge carrier plasmon in Sr2RuO4
Creators: name: Knupfer, Martin
name: Jerzembeck, Fabian
name: Kikugawa, Naoki
name: Roth, Friedrich
name: Fink, Joerg
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We report on studies of charge carrier plasmon excitations in Sr2RuO4 by transmission Electron Energy-Loss Spectroscopy. In particular, we present results on the plasmon dispersion and its width as a function of momentum transfer. The dispersion can be qualitatively explained in the framework of RPA calculations, using an unrenormalized tight-binding band structure. The constant long-wavelength width of the plasmon indicates, that it is caused by a decay into inter-band transition and not by quantum critical fluctuations. The results from these studies on a prototypical bad metal system show that the long-wavelength plasmon excitations near 1 eV are caused by resilient quasiparticles and are not influenced by correlation effects.
description: 6 pages, 3 figures