cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Light rings and shadows of static black holes in effective quantum gravity
Creators: name: Liu, Wentao
name: Wu, Di
name: Wang, Jieci
Publisher: name: arXiv
Year: 2024
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Recently, two types of static black hole models that retain general covariance have been proposed within the Hamiltonian constraint approach to effective quantum gravity (EQG). We have studied the light rings and shadows of these black holes using the topological method and the backward ray-tracing method, respectively. We demonstrate that these light rings in both types of static black holes are standard and unstable according to the classification of light rings. Subsequently, we checked the position of the light rings using the photon trajectory equation. We found that although the quantum parameters do not affect the light rings of these two types of black holes, they do reduce the size of the first type of static black hole in EQG, making it smaller. However, for the second type of static black hole in EQG, we cannot distinguish it from a Schwarzschild black hole based on the shadow alone. Fortunately, the quantum parameters shrink the lensing rings of both types of black holes in EQG, causing the black hole shadow to occupy a larger proportion within the ring. This can serve as a basis for distinguishing whether the black hole is in EQG or general relativity (GR).
description: 10 pages, 8 figures, 1 table, match with the published version in PLB
A Low-Power, Low-Latency, Dual-Channel Serializer ASIC for Detector Front-End Readout
Creators: name: Xiaoa, Le
name: Gong, Datao
name: Liu, Tiankuan
name: Chen, Jinghong
name: Fan, Qingjun
name: Feng, Yulang
name: Guo, Di
name: He, Huiqin
name: Hou, Suen
name: Huang, Guangming
name: Lig, Xiaoting
name: Liu, Chonghan
name: Sun, Quan
name: Sun, Xiangming
name: Teng, Ping-Kun
name: Wang, Jian
name: Xiang, Annie C.
name: Yang, Dongxu
name: Ye, Jingbo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: In this paper, we present a dual-channel serializer ASIC, LOCx2, and its pin-compatible backup, LOCx2-130, for detector front-end readout. LOCx2 is fabricated in a 0.25-um Silicon-on-Sapphire CMOS process and each channel operates at 5.12 Gbps, while LOCx2-130 is fabricated in a 130-nm bulk CMOS process and each channel operates at 4.8 Gbps. The power consumption and the transmission latency are 900 mW and 27 ns for LOCx2 and the corresponding simulation result of LOCx2-130 are 386 mW and 38 ns, respectively.
description: 8 pages, 10 figures
Symmetric construction of reference-frame-free qudits
Creators: name: Suzuki, Jun
name: Tabia, Gelo Noel Macuja
name: Englert, Berthold-Georg
Publisher: name: arXiv
Year: 2008
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: By exploiting a symmetric scheme for coupling $N$ spin-1/2 constituents (the physical qubits) to states with total angular momentum $N/2-1$, we construct rotationally invariant logical qudits of dimension $d=N-1$. One can encode all qudit states, and realize all qudit measurements, by this construction. The rotational invariance of all relevant objects enables one to transmit quantum information without having aligned reference frames between the parties that exchange the qudits. We illustrate the method by explicit constructions of reference-frame-free qubits and qutrits and, for the qubit case, comment on possible experimental implementations.
description: 5 pages, typos corrected
Broadband quantum-dot frequency-modulated comb laser
Creators: name: Dong, Bozhang
name: Dumont, Mario
name: Terra, Osama
name: Wang, Heming
name: Netherton, Andrew
name: Bowers, John E.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optics (physics.optics)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Frequency-modulated (FM) laser combs, which offer a periodic quasi-continuous-wave output and a flat-topped optical spectrum, are emerging as a promising solution for wavelength-division multiplexing applications, precision metrology, and ultrafast optical ranging. The generation of FM combs relies on spatial hole burning, group velocity dispersion (GVD), Kerr nonlinearity, and four-wave mixing (FWM). While FM combs have been widely observed in quantum cascade Fabry-Perot (FP) lasers, the requirement for a low-dispersion FP cavity can be a challenge in platforms where the waveguide dispersion is mainly determined by the material. Here we report a 60 GHz quantum-dot (QD) mode-locked laser in which both the amplitude-modulated (AM) and the FM comb can be generated independently. The high FWM efficiency of -5 dB allows the QD laser to generate an FM comb efficiently. We also demonstrate that the Kerr nonlinearity can be practically engineered to improve the FM comb bandwidth without the need for GVD engineering. The maximum 3-dB bandwidth that our QD platform can deliver is as large as 2.2 THz. This study gives novel insights into the improvement of FM combs and paves the way for small-footprint, electrically-pumped, and energy-efficient frequency combs for silicon photonic integrated circuits (PICs).
Controlling soliton excitations in Heisenberg spin chain through magic angle
Creators: name: Lu, Jing
name: Zhou, Lan
name: Kuang, Le-Man
name: Sun, C. P.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study the nonlinear dynamics of collective excitation in a $N$-site $XXZ$ quantum spin chain, which is manipulated by an oblique magnetic field. We show that, when the tilted field is applied along the magic angle $θ_{0} =\pm\arccos \sqrt{1/3}$, the anisotropic Heisenberg spin chain becomes isotropic and thus an free propagating spin wave is stimulated. And in the regime of the tilted angle larger and smaller then the magic angle, two types of nonlinear excitations appear, which are bright soliton and dark soliton.
description: 7 pages 4 figures
Permanent magnet systems to study the interaction between magnetic nanoparticles and cells in microslide channels
Creators: name: Abelmann, Leon
name: Gwag, Eunheui
name: Sung, Baeckkyoung
Publisher: name: arXiv
Year: 2023
Subjects: subject: Biological Physics (physics.bio-ph)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: We optimized designs of permanent magnet systems to study the effect of magnetic nanoparticles on cell cultures in microslide channels. This produced two designs, one of which is based on a large cylindrical magnet that applies a uniform force density of 6 MN/m$^3$ on soft magnetic iron-oxide spherical nanoparticles at a field strength of over 300 mT. We achieved a force uniformity of better than 14% over the channel area leading to a concentration variation that was below our measurement resolution. The second design was aimed at maximizing the force by using a Halbach array. We indeed increased the force by more than one order of magnitude at force density values over 400 MN/m$^3$, but at the cost of uniformity. However, the latter system can be used to trap magnetic nanoparticles efficiently and to create concentration gradients. We demonstrated both designs by analyzing the effect of magnetic forces on the cell viability of human hepatoma HepG2 cells in the presence of bare Fe$_2$O$_3$ and cross-linked dextran iron-oxide cluster-type particles (MicroMod). Python scripts for magnetic force calculations and particle trajectory modeling as well as source files for 3D prints have been made available so these designs can be easily adapted and optimized for other geometries.
description: 14 pages, 15 figures
Parity-Dependent Moiré Superlattices in Graphene/h-BN Heterostructures: A Route to Mechanomutable Metamaterials
Creators: name: Ouyang, Wengen
name: Hod, Oded
name: Urbakh, Michael
Publisher: name: arXiv
Year: 2020
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The superlattice of alternating graphene/h-BN few-layered heterostructures is found to exhibit strong dependence on the parity of the number of layers within the stack. Odd-parity systems show a unique flamingo-like pattern, whereas their even-parity counterparts exhibit regular hexagonal or rectangular superlattices. When the alternating stack consists of seven layers or more, the flamingo pattern becomes favorable, regardless of parity. Notably, the out-of-plane corrugation of the system strongly depends on the shape of the superstructure resulting in significant parity dependence of its mechanical properties. The predicted phenomenon originates in an intricate competition between moiré patterns developing at the interface of consecutive layers. This mechanism is of general nature and is expected to occur in other alternating stacks of closely matched rigid layered materials as demonstrated for homogeneous alternating junctions of twisted graphene and h-BN. Our findings thus allow for the rational design of mechanomutable metamaterials based on Van der Waals heterostructures.
description: 31 pages, 17 figures
Cross section for supernova axion observation in neutrino water Cherenkov detectors
Creators: name: Carenza, Pierluca
name: Co', Giampaolo
name: Giannotti, Maurizio
name: Lella, Alessandro
name: Lucente, Giuseppe
name: Mirizzi, Alessandro
name: Rauscher, Thomas
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Axions coupled to nucleons might be copiously emitted from core-collapse supernovae (SNe). If the axion-nucleon coupling is strong enough, axions would be emitted from the SN as a burst and, reaching Earth, may excite the oxygen nuclei in water Cherenkov detectors (${}^{16}{\rm O} + a \to {}^{16}{\rm O}^{*}$). This process will be followed by decay(s) of the excited state resulting in an emission of photons and thus providing a possibility for a direct detection of axions from a Galactic SN in large underground neutrino Cherenkov detectors. Motivated by this possibility, we present an updated calculation of axion-oxygen cross section obtained by using self-consistent continuum Random Phase Approximation. We calculate the branching ratio of the oxygen nucleus de-excitation into gamma-rays, neutrons, protons and $α$-particles and also consider photon emission from secondary nuclei to compute a total $γ$ spectrum created when axions excite ${}^{16}{\rm O}$. These results are used to revisit the detectability of axions from SN 1987A in Kamiokande-II.
description: 22 pages, 9 figures. Matches the version published on PRC. Changes: we employed different benchmark SN model with respect to the previous version, accounting for a 1D treatment of convection
Investigation of unsupervised and supervised hyperspectral anomaly detection
Creators: name: Hossain, Mazharul
name: Robinson, Aaron
name: Wang, Lan
name: Preza, Chrysanthe
Publisher: name: arXiv
Year: 2024
Subjects: subject: Image and Video Processing (eess.IV)
subject: Machine Learning (cs.LG)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences

description: Hyperspectral sensing is a valuable tool for detecting anomalies and distinguishing between materials in a scene. Hyperspectral anomaly detection (HS-AD) helps characterize the captured scenes and separates them into anomaly and background classes. It is vital in agriculture, environment, and military applications such as RSTA (reconnaissance, surveillance, and target acquisition) missions. We previously designed an equal voting ensemble of hyperspectral unmixing and three unsupervised HS-AD algorithms. We later utilized a supervised classifier to determine the weights of a voting ensemble, creating a hybrid of heterogeneous unsupervised HS-AD algorithms with a supervised classifier in a model stacking, which improved detection accuracy. However, supervised classification methods usually fail to detect novel or unknown patterns that substantially deviate from those seen previously. In this work, we evaluate our technique and other supervised and unsupervised methods using general hyperspectral data to provide new insights.
Spectroscopy of orbital ordering in La0.5Sr1.5MnO4 : A many-body cluster calculation
Creators: name: Mirone, Alessandro
name: Dhesi, S. S.
name: van der Laan, G.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We have studied the orbital ordering (OO) in La0.5Sr1.5MnO4 and its soft x-ray resonant diffraction spectroscopic signature at the Mn L2, L3 edges. We have modelled the system in second quantization as a small planar cluster consisting of a central Mn atom, with the first neighbouring shells of oxygen and Mn atoms. For the effective Hamiltonian we consider Slater-Koster parameters, charge transfer and electron correlation energies obtained from previous measurements on manganites. We calculate the OO as a function of oxygen distortion and spin correlation used as adjustable parameters. Their contribution as a function of temperature is clearly distinguished with a good spectroscopic agreement.
description: 5 pages 3 figures
Hybrid cavity-antenna architecture for strong and tunable sideband-selective molecular Raman scattering enhancement
Creators: name: Shlesinger, Ilan
name: Vandersmissen, Jente
name: Oksenberg, Eitan
name: Verhagen, Ewold
name: Koenderink, A. Femius
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optics (physics.optics)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Plasmon resonances at the surface of plasmonic antennas allow for extremely strong enhancement of Raman scattering. Intrinsic to plasmonics, however, is that extreme field confinement lacks precise spectral control, which would hold great promise in shaping the optomechanical interaction between light and molecular vibrations at will. We demonstrate an experimental platform composed of a plasmonic nanocube-on-mirror antenna coupled to an open, tunable Fabry-Perot microcavity for selective addressing of individual vibrational lines of molecules with strong Raman scattering enhancement. Multiple narrow and intense optical resonances arising from the hybridization of the cavity modes and the plasmonic broad resonance are used to simultaneously enhance the laser pump and the local density of optical states (LDOS) and are characterized using rigorous modal analysis. The versatile bottom-up fabrication approach permits quantitative comparison with the bare nanocube-on-mirror system, both theoretically and experimentally. This shows that the hybrid system allows for similar SERS enhancement ratios with narrow optical modes, paving the way for dynamical back action effects in molecular optomechanics.
Social Closure, Surnames and Crime
Creators: name: Buonanno, Paolo
name: Vanin, Paolo
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2015
Subjects: SECS-P/01 Economia politica

description: This paper studies the effect of social closure on crime and tax evasion rates using disaggregated data for Italian municipalities. It measures the degree of social openness of a community by the diversity of its surname distribution, which reflects the history of migration and inbreeding. It shows that, all else equal, communities with a history of social closure have lower crime rates and higher tax evasion rates than more open communities. The effect of social closure is likely to be causal, it is relevant in magnitude, statistically significant, and robust to changes in the set of included controls, in the specific measures of dependent and independent variables, in the specification of the regression equation, and in the possible sample splits. Our findings are consistent with the idea that social closure strengthens social sancions and social control, thus leading to more cooperative outcomes in local interactions, but it reduces cooperation on a larger scale.
Squares of Menger-bounded groups
Creators: name: Machura, Michal
name: Shelah, Saharon
name: Tsaban, Boaz
Publisher: name: arXiv
Year: 2006
Subjects: subject: General Topology (math.GN)
subject: Logic (math.LO)
subject: FOS: Mathematics

description: Using the Continuum Hyporthesis, we prove that there is a Menger-bounded (also called o-bounded) subgroup of the Baer-Specker group Z^N, whose square is not Menger-bounded. This settles a major open problem concerning boundedness notions for groups, and implies that Menger-bounded groups need not be Scheepers-bounded. This also answers some questions of Banakh, Nickolas, and Sanchis.
Imaging strain-controlled magnetic reversal in thin CrSBr
Creators: name: Bagani, Kousik
name: Vervelaki, Andriani
name: Jetter, Daniel
name: Devarakonda, Aravind
name: Tschudin, Märta A.
name: Gross, Boris
name: Chica, Daniel G.
name: Broadway, David A.
name: Dean, Cory R.
name: Roy, Xavier
name: Maletinsky, Patrick
name: Poggio, Martino
Publisher: name: arXiv
Year: 2024
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Two-dimensional materials are extraordinarily sensitive to external stimuli, making them ideal for studying fundamental properties and for engineering devices with new functionalities. One such stimulus, strain, affects the magnetic properties of the layered magnetic semiconductor CrSBr to such a degree that it can induce a reversible antiferromagnetic-to-ferromagnetic phase transition. Given the pervasiveness of non-uniform strain in exfoliated two-dimensional magnets, it is crucial to understand its impact on their magnetic behavior. Using scanning SQUID-on-lever microscopy, we directly image the effects of spatially inhomogeneous strain on the magnetization of layered CrSBr as it is polarized by a field applied along its easy axis. The evolution of this magnetization and the formation of domains is reproduced by a micromagnetic model, which incorporates the spatially varying strain and the corresponding changes in the local interlayer exchange stiffness. The observed sensitivity to small strain gradients along with similar images of a nominally unstrained CrSBr sample suggest that unintentional strain inhomogeneity influences the magnetic behavior of exfoliated samples and must be considered in the design of future devices.
description: 15 pages, 4 figures, 1 supplementary section
On the Observational Equivalence of Unilateral Delegation Contracts in Duopoly
Creators: name: Lambertini, Luca
name: Delbono, Flavio
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2015
Subjects: SECS-P/01 Economia politica

description: In a Cournot duopoly, if only one firm hires a manager while the other remains entrepreneurial, the Cournot-Stackelberg equilibrium emerges, with the managerial firm as the leader. This happens under at least three different delegation schemes. We illustrate the different meachanisms driving this outcome through the analysis of the map of best replies at the market stage.
Autonomous Learning of Features for Control: Experiments with Embodied and Situated Agents
Creators: name: Milano, Nicola
name: Nolfi, Stefano
Publisher: name: arXiv
Year: 2020
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: As discussed in previous studies, the efficacy of evolutionary or reinforcement learning algorithms for continuous control optimization can be enhanced by including a neural module dedicated to feature extraction trained through self-supervised methods. In this paper we report additional experiments supporting this hypothesis and we demonstrate how the advantage provided by feature extraction is not limited to problems that benefit from dimensionality reduction or that involve agents operating on the basis of allocentric perception. We introduce a method that permits to continue the training of the feature-extraction module during the training of the policy network and that increases the efficacy of feature extraction. Finally, we compare alternative feature-extracting methods and we show that sequence-to-sequence learning yields better results than the methods considered in previous studies.
Converging sequences in the ab initio no-core shell model
Creators: name: Forssén, C.
name: Vary, J. P.
name: Caurier, E.
name: Navrátil, P.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We demonstrate the existence of multiple converging sequences in the ab initio no-core shell model. By examining the underlying theory of effective operators, we expose the physical foundations for the alternative pathways to convergence. This leads us to propose a revised strategy for evaluating effective interactions for $A$-body calculations in restricted model spaces. We suggest that this strategy is particularly useful for applications to nuclear processes in which states of both parities are used simultaneously, such as for transition rates. We demonstrate the utility of our strategy with large-scale calculations in light nuclei.
TIAM -- A Metric for Evaluating Alignment in Text-to-Image Generation
Creators: name: Grimal, Paul
name: Borgne, Hervé Le
name: Ferret, Olivier
name: Tourille, Julien
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Artificial Intelligence (cs.AI)
subject: Computation and Language (cs.CL)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: The progress in the generation of synthetic images has made it crucial to assess their quality. While several metrics have been proposed to assess the rendering of images, it is crucial for Text-to-Image (T2I) models, which generate images based on a prompt, to consider additional aspects such as to which extent the generated image matches the important content of the prompt. Moreover, although the generated images usually result from a random starting point, the influence of this one is generally not considered. In this article, we propose a new metric based on prompt templates to study the alignment between the content specified in the prompt and the corresponding generated images. It allows us to better characterize the alignment in terms of the type of the specified objects, their number, and their color. We conducted a study on several recent T2I models about various aspects. An additional interesting result we obtained with our approach is that image quality can vary drastically depending on the noise used as a seed for the images. We also quantify the influence of the number of concepts in the prompt, their order as well as their (color) attributes. Finally, our method allows us to identify some seeds that produce better images than others, opening novel directions of research on this understudied topic.
Exploring Quantum Speed-up Through Cluster-state Computers
Creators: name: Annovi, Filippo <1986>
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2015
Subjects: M-FIL/02 Logica e filosofia della scienza

description: The aim of this thesis is to investigate the nature of quantum computation and the question of the quantum speed-up over classical computation by comparing two different quantum computational frameworks, the traditional quantum circuit model and the cluster-state quantum computer. After an introductory survey of the theoretical and epistemological questions concerning quantum computation, the first part of this thesis provides a presentation of cluster-state computation suitable for a philosophical audience. In spite of the computational equivalence between the two frameworks, their differences can be considered as structural. Entanglement is shown to play a fundamental role in both quantum circuits and cluster-state computers; this supports, from a new perspective, the argument that entanglement can reasonably explain the quantum speed-up over classical computation. However, quantum circuits and cluster-state computers diverge with regard to one of the explanations of quantum computation that actually accords a central role to entanglement, i.e. the Everett interpretation. It is argued that, while cluster-state quantum computation does not show an Everettian failure in accounting for the computational processes, it threatens that interpretation of being not-explanatory. This analysis presented here should be integrated in a more general work in order to include also further frameworks of quantum computation, e.g. topological quantum computation. However, what is revealed by this work is that the speed-up question does not capture all that is at stake: both quantum circuits and cluster-state computers achieve the speed-up, but the challenges that they posit go besides that specific question. Then, the existence of alternative equivalent quantum computational models suggests that the ultimate question should be moved from the speed-up to a sort of “representation theorem” for quantum computation, to be meant as the general goal of identifying the physical features underlying these alternative frameworks that allow for labelling those frameworks as “quantum computation”.
Discrete Riemann Surfaces
Creators: name: Mercat, Christian
Publisher: name: arXiv
Year: 2008
Subjects: subject: Complex Variables (math.CV)
subject: Mathematical Physics (math-ph)
subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 37K25 (30G25)

description: We detail the theory of Discrete Riemann Surfaces. It takes place on a cellular decomposition of a surface, together with its Poincaré dual, equipped with a discrete conformal structure. A lot of theorems of the continuous theory follow through to the discrete case, we define the discrete analogs of period matrices, Riemann's bilinear relations, exponential of constant argument and series. We present the notion of criticality and its relationship with integrability.
Gendered voices: the Liebesfrühling Lieder of Robert and Clara Schumann
Creators: name: Boyd, Melinda Jean
Publisher: name: University of British Columbia
Year: 2009

description: In 1841, Robert and Clara Schumann collaborated on a setting of twelve poems from Friedrich Ruckert's Liebesfhihling. Although these songs were popular in the composers' lifetime, today they are sadly neglected. Rufus Hallmark's 1990 article, "The Riickert Lieder of Robert and Clara Schumann" (19th-century Music, 14:1), draws on manuscript and diary sources, examining the cycle from various points of view, among which gender issues are touched upon from the perspective of performance practice. Taking Hallmark's article as a starting point, this thesis employs more recent feminist and cultural theories to scrutinize the Lieder, as well as the creative partnership, from a gender perspective. Chapter One concentrates on the influence of Western cultural attitudes and the role of gender in the genesis of the Lieder, followed by a detailed inquiry into the choice of texts, and the chronology of the subsequent compositions, confirming the extent of the collaboration. Chapter Two provides a close reading of the gender ambiguity inherent in the imagery and ideological content of Ruckert's poems. Chapter Three proceeds to the musical settings, examining form, harmonic language, melody, rhythm and motivic usage, and how these musical materials interact with the gender ambiguity in the texts. Chapter Four draws on the analysis of the previous two chapters in an attempt to read the Liebesfhihling Lieder as a "song cycle." The thesis concludes with an evaluation of the songs and the creative partnership, laying the foundation for a renewed interest in this unique collection of Lieder.
Magnetoelastic properties of a spin-1/2 Ising-Heisenberg diamond chain in vicinity of a triple coexistence point
Creators: name: Ferreira, N.
name: Torrico, J.
name: de Souza, S. M.
name: Rojas, O.
name: Strečka, J.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We study magnetoelastic properties of a spin-1/2 Ising-Heisenberg diamond chain, whose elementary unit cell consists of two decorating Heisenberg spins and one nodal Ising spin. It is assumed that each couple of the decorating atoms including the Heisenberg spins harmonically vibrates perpendicularly to the chain axis, while the nodal atoms involving the Ising spins are placed at rigid positions when ignoring their lattice vibrations. An effect of the magnetoelastic coupling on a ground state and finite-temperature properties is particularly investigated close to a triple coexistence point depending on a spring-stiffness constant ascribed to the Heisenberg interaction. The magnetoelastic nature of the Heisenberg dimers is reflected through a non-null plateau of the entropy emergent in a low-temperature region, whereas the specific heat displays an anomalous peak slightly below the temperature region corresponding to the entropy plateau. The magnetization also exhibits a plateau in the same temperature region at almost saturated value before it gradually tends to zero upon increasing of temperature. The magnetic susceptibility displays within the plateau region an inverse temperature dependence, which slightly drops above this plateau, whereas an inverse temperature dependence is repeatedly recovered at high enough temperatures.
description: 12 pages, 5 figures
Roles of electric field/time-dependent Wilson line in toroidal compactification with or without magnetic fluxes
Creators: name: Abe, Hiroyuki
name: Yamada, Yusuke
Publisher: name: arXiv
Year: 2024
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We discuss the effects of electric fields along compact directions within (supersymmetric) gauge theory in $\mathbb{R}^{1,3}\times{\mathbb T}^2 (\times{\mathbb T}^2\times{\mathbb T}^2)$. The electric field along compact directions is equivalent to time-dependent homogeneous configuration of Wilson line moduli, which would be relevant to physics in the early universe. In particular, we consider models with and without background magnetic fluxes, which lead to completely different effects of the electric field due to the difference in the Kaluza-Klein (KK) level structure. We show that, in the case without magnetic fluxes, the deceleration of KK momenta may cause non-perturbative KK particle production dubbed as the KK Schwinger effect, whereas in the case with magnetic flux such KK particle production does not take place but flavor structure of low energy effective theory may be affected.
description: 24+20 pages, 6 figures, v2:typos corrected, comments added
Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
Creators: name: Gotz, D.
name: Mereghetti, S.
name: Tiengo, A.
name: Esposito, P.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index Gamma=3.1+/-0.5 and flux 1.5E-11 erg/cmsq/s. Contrary to SGR 1806-20, the only other soft gamma-ray repeater for which persistent emission above 20 keV was reported, SGR 1900+14 has been detected in the hard X-ray range while it was in a quiescent state (the last bursts from this source were observed in 2002). By comparing the broad band spectra (1-100 keV) of all the magnetars detected by INTEGRAL (the two SGRs and three anomalous X-ray pulsars) we find evidence for a different spectral behaviour of these two classes of sources.
description: 5 pages, 2 figures, submitted to A&A Letters
Raman scattering from high frequency phonons in supported n-graphene layer films
Creators: name: Gupta, Awnish
name: Chen, Gugang
name: Joshi, P.
name: Tadigadapa, S.
name: Eklund, P. C.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: Results of room temperature Raman scattering studies of ultrathin graphitic films supported on Si (111)/SiO2 substrates are reported. The results are significantly different from those known for graphite. Spectra were collected using 514 nm radiation on films containing from n=1 to 20 graphene layers, as determined by atomic force microscopy. Both the 1st and 2nd order Raman spectra show unique signatures of the number of layers in the film. The nGL film analog of the Raman G-band in graphite exhibits a Lorentzian lineshape whose center frequency shifts linearly relative to graphite as ~1/n (for n=1 G-band frequency ~1588 cm-1). Three weak bands, identified with disorder-induced 1st order scattering, are observed at ~ 1350, 1450 and 1500 cm-1. The 1500 cm-1 band is weak but relatively sharp and exhibits an interesting n-dependence. In general, the intensity of these D-bands decreases dramatically with increasing n. Three 2nd order bands are also observed (~2450, ~2700 and 3248 cm-1). They are analogs to those observed in graphite. However, the ~2700 cm-1 band exhibits an interesting and dramatic change of shape with n. Interestingly, for n<5 this 2nd order band is more intense than the G-band.
description: 10 pages, 7 fig's
Charm mesons at FAIR
Creators: name: Tolos, Laura
name: Ramos, Angels
name: Mizutani, Tetsuro
Publisher: name: arXiv
Year: 2008
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The in-medium properties of charm mesons ($D$ and $\bar D$) in a hot and dense matter are studied. A self-consistent coupled-channel approach is driven by a broken SU(4) s-wave Tomozawa-Weinberg interaction supplemented by an attractive isoscalar-scalar term. As medium effects, we include Pauli blocking, baryon mean-field bindings, and $π$ and open-charm meson self-energies. The dynamically generated $\tildeΛ_c$ and $\tildeΣ_c$ resonances in the $DN$ sector remain close to their free space position but acquire large widths. The resultant $D$ meson spectral function, which shows a single pronounced quasiparticle peak close to the free mass that broadens with increasing density, also has a long low energy tail associated with smeared $\tildeΛ_c N^{-1}$, $\tildeΣ_c N^{-1}$ configurations. The low-density approximation for the $\bar D N$ is questionable already at subsaturation densities. We touch upon the implication of our study for $J/Ψ$ suppression at FAIR.
description: 4 pages, 3 figures, contribution to the proceedings of Chiral07, RCNP, Osaka, Japan, November 13-16, 2007
Initialization-Free Multistate Memristor: Synergy of Spin-Orbit Torque and Magnetic Fields
Creators: name: Posti, Raghvendra
name: Kalouni, Chirag
name: Tiwari, Dhananjay K
name: Roy, Debangsu
Publisher: name: arXiv
Year: 2024
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Spin-orbit torque (SOT)-based perpendicularly magnetized memory devices with multistate memory have garnered significant interest due to their applicability in low-power in-memory analog computing. However, current methods are hindered by initialization problems such as prolonged writing duration, and limitations on the number of magnetic states. Consequently, a universal method for achieving multistate in PMA-based stacks remains elusive. Here, we propose a general experimental method for achieving multistate without any initialization step in SOT-driven magnetization switching by integrating an external out-of-plane magnetic field. Motivated by macrospin calculations coupled with micromagnetic simulations, which demonstrate the plausibility of magnetization state changes due to out-of-plane field integration, we experimentally verify multistate behavior in Pt/Co/Pt and W/Pt/Co/AlOx stacks. The occurrence of multistate behavior is attributed to intermediate domain states with Néel domain walls. We achieve repeatable 18 multistate configurations with a minimal reduction in retentivity through energy barrier measurements, paving the way for efficient analog computing.
Scalable spray-coated graphene-based electrodes for high-power electrochemical double-layer capacitors operating over a wide range of temperature
Creators: name: Garakani, Mohammad Akbari
name: Bellani, Sebastiano
name: Pellegrini, Vittorio
name: Oropesa-Nuñez, Reinier
name: Del RioCastillo, Antonio Esau
name: Abouali, Sara
name: Najafi, Leyla
name: Martín-García, Beatriz
name: Ansaldo, Alberto
name: Bondavalli, Paolo
name: Demirci, Cansunur
name: Romano, Valentino
name: Mantero, Elisa
name: Marasco, Luigi
name: Prato, Mirko
name: Bracciale, Gaetan
name: Bonaccorso, Francesco
Publisher: name: arXiv
Year: 2020
Subjects: subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Advancements in electrochemical double-layer capacitor (EDLC) technology require the concomitant use of novel efficient electrode materials and viable electrode manufacturing methods. Cost-effectiveness, scalability and sustainability are key-drivers for fulfilling product development chain accepted by worldwide legislations. Herein, we report a scalable and sprayable "green" electrode material-based ink based on activated carbon and single-/few-layer graphene (SLG/FLG) flakes. We show that, contrary to commercial reduced graphene oxide, defect-free and flat SLG/FLG flakes reduce the friction of ions over the electrode films, while spray coating deposition of our ink maximises the electrolyte accessibility to the electrode surface area. Sprayed SLG/FLG flakes-based EDLCs display superior rate capability performance (e.g., specific energies of 31.5, 23.7 and 12.5 Wh kg-1 at specific powers of 150, 7500 and 30000 W kg-1, respectively) compared to both SLG/FLG flakes-free devices and commercial-like EDLCs produced by slurry-coating method. The use of SLG/FLG flakes enables our sprayed EDLCs to operate in a wide range of temperature (-40/+100°C) compatible with ionic liquid/organic solvent-based electrolytes, overcoming the specific power limits of AC-based EDLCs. A prototype EDLCs stack consisting of multiple large-area EDLCs, each one displaying a capacitance of 25 F, demonstrates the industrial potential of our technology.
In situ AC-hysteresis measurements of SPD-processed Cu20(Fe15Co85)80
Creators: name: Stückler, Martin
name: Wurster, Stefan
name: Pippan, Reinhard
name: Bachmaier, Andrea
Publisher: name: arXiv
Year: 2021
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: The changes of magnetic properties upon heat treatment of a metastable supersaturated solid solution processed by severe plastic deformation are investigated by in-situ AC-hysteresis measurements. Data are analyzed in the framework of dynamic loss theory, with correlative investigations of the microstructural properties. The evolution of hysteresis upon annealing points out that the single-phase supersaturated solid solution remains stable up to 400°C, then hindering of domain wall motion sets in at this temperature. At 600°C, a multi phase microstructure is present, causing a significant increase in coercivity.
description: 6 pages, 6 figures
title: Book of abstracts – VLIZ Marine Science Day, Online event 3 March 2021
Creators: name: Mees, Jan
name: Seys, Jan
Publisher: name: Flanders Marine Institute
Year: 2021

description: Title : VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950 Volume : 85 Issue : Pagination : vi, 128
Can Helium-detonation Model Explain the Observed Diversity of Type Ia Supernovae?
Creators: name: Li, Wenxiong
name: Wang, Xiaofeng
name: Bulla, Mattia
name: Pan, Yen-Chen
name: Wang, Lifan
name: Mo, Jun
name: Zhang, Jujia
name: Wu, Chengyuan
name: Zhang, Jicheng
name: Zhang, Tianmeng
name: Xiang, Danfeng
name: Lin, Han
name: Sai, Hanna
name: Zhang, Xinghan
name: Chen, Zhihao
name: Yan, Shengyu
Publisher: name: arXiv
Year: 2020
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We study a sample of 16 Type Ia supernovae (SNe Ia) having both spectroscopic and photometric observations within 2 $-$ 3 days after the first light. The early $B-V$ colors of such a sample tends to show a continuous distribution. For objects with normal ejecta velocity (NV), the C~II $λ$6580 feature is always visible in the early spectra while it is absent or very weak in the high-velocity (HV) counterpart. Moreover, the velocities of the detached high-velocity features (HVFs) of Ca~II NIR triplet (CaIR3) above the photosphere are found to be much higher in HV objects than in NV objects, with typical values exceeding 30,000 km~s$^{-1}$ at 2 $-$ 3 days. We further analyze the relation between %velocities of Si~II~$λ$6355 at maximum, $v_{\rm Si,max}$, the velocity shift of late-time [Fe~II] lines ($v_{\rm [Fe~II]}$) and host galaxy mass. We find that all HV objects have redshifted $v_{\rm [Fe~II]}$ while NV objects have both blue- and redshifted $v_{\rm [Fe~II]}$. It is interesting to point out that the objects with redshifted $v_{\rm [Fe~II]}$ are all located in massive galaxies, implying that HV and a portion of NV objects may have similar progenitor metallicities and explosion mechanisms. We propose that, with a geometric/projected effect, the He-detonation model may account for the similarity in birthplace environment and the differences seen in some SNe Ia, including $B-V$ colors, C~II feature, CaIR3 HVFs at early time and $v_{\rm [Fe~II]}$ in the nebular phase. Nevertheless, some features predicted by He-detonation simulation, such as the rapidly decreasing light curve, deviate from the observations, and some NV objects with blueshifted nebular $v_{\rm [Fe~II]}$ may involve other explosion mechanisms.
description: accepted by the ApJ
Matrix Tensor Product Approach to the Equivalence of Multipartite States under Local Unitary Transformations
Creators: name: Gao, X. H.
name: Alberverio, S.
name: Fei, S. M.
name: Wang, Z. X.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The equivalence of multipartite quantum mixed states under local unitary transformations is studied. A criterion for the equivalence of non-degenerate mixed multipartite quantum states under local unitary transformations is presented.
description: 7 pages
A multiple criteria decision process : the case study of rapid transit in Greater Vancouver
Creators: name: Oyhenart, Gregory John Peter
Publisher: name: University of British Columbia
Year: 2009

description: One of the most fundamental issues in the field of planning revolves around evaluation within the decision making process. What determines how governments, or government agencies, allocate public resources? What social, economic, environmental, and political considerations are taken into account? Who is involved in this process? The purpose of this thesis is to examine evaluation methodology using the case study of the decision on the next phase of rapid transit within the Greater Vancouver area. The thesis begins by reviewing the major evaluation methodologies available for the decision: Cost-Benefit Analysis, Planning Balance Sheet, Goals Achievement Matrix, Multiple Criteria Analysis, Multiple Accounts, and the Delphi Process. An analysis of each model's strengths, weaknesses, and historical applications shows that no one is adequate for our decision. The emphasis of evaluation is typically to produce an answer for decision makers. The purpose of the literature review is to see what opportunities exist within these various models to include a process for decision making. The emphasis is not on identifying the best route, but how to decide which would be the best route. The focus is on what factors should be accounted for, and who should be involved in the process. Rapid Transit options have been reviewed and evaluated by two government agencies, the Greater Vancouver Regional District (GVRD) and BC Transit, with conflicting results. The GVRD's evaluation used a quasi-Multiple Accounts, and the BC Transit review was a combination of Multiple Accounts and Multiple Criteria Analysis. The two studies, like the theoretical models they are based on, suffered practical shortcomings. Prominent in both was a lack of public participation in the7 final decision-making process. After reviewing the various methodologies and practical problems with the case study, the thesis offers a model based on simple Multiple Criteria Analysis, Multiple Accounts, and the Delphi Process. The hybrid model is sufficiently comprehensive to account for all of the relevant economic, social, and environmental factors and sufficiently robust to include public input to the decision making process. The aim of the thesis is not to radically change the scope of evaluation methodology, but to set it in a broader socioeconomic context.
Detecting solar g-modes with ASTROD
Creators: name: Burston, R.
name: Gizon, L.
name: Appourchaux, T.
name: Ni, W. T.
name: team, ASTROD I ESA cosmic vision 2015-2025
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present an up-to-date estimate for the prospect of using the Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) for an unambiguous detection of solar g modes (f < 400 micro Hertz) through their gravitational signature. There are currently two major efforts to detect low-frequency gravitational effects, ASTROD and the Laser Interferometer Space Antenna (LISA). Using the most recent g mode surface amplitude estimates, both observational and theoretical, it is unclear whether LISA will be capable of successfully detecting these modes. The ASTROD project may be better suited for detection as its sensitivity curve is shifted towards lower frequencies with the best sensitivity occurring in the range 100-300 micro Hertz.
description: HELAS II international conference "Helioseismology, asteroseismology and MHD connections", 20-24 August 2007, Goettingen, Germany
Efficient likelihood estimation in state space models
Creators: name: Fuh, Cheng-Der
Publisher: name: arXiv
Year: 2006
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: Motivated by studying asymptotic properties of the maximum likelihood estimator (MLE) in stochastic volatility (SV) models, in this paper we investigate likelihood estimation in state space models. We first prove, under some regularity conditions, there is a consistent sequence of roots of the likelihood equation that is asymptotically normal with the inverse of the Fisher information as its variance. With an extra assumption that the likelihood equation has a unique root for each $n$, then there is a consistent sequence of estimators of the unknown parameters. If, in addition, the supremum of the log likelihood function is integrable, the MLE exists and is strongly consistent. Edgeworth expansion of the approximate solution of likelihood equation is also established. Several examples, including Markov switching models, ARMA models, (G)ARCH models and stochastic volatility (SV) models, are given for illustration.
description: With the comments by Jens Ledet Jensen and reply to the comments. Published at http://dx.doi.org/10.1214/009053606000000614; http://dx.doi.org/10.1214/09-AOS748A; http://dx.doi.org/10.1214/09-AOS748B in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org)