cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Role of the effective range in the density-induced BEC-BCS crossover
Creators: name: Tajima, Hiroyuki
name: Liang, Haozhao
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Superconductivity (cond-mat.supr-con)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We elucidate the role of the effective range in the Bose-Einstein-condensate (BEC) to Bardeen-Cooper-Schrieffer (BCS) crossover regime of two-component fermions in three dimensions. In contrast to ultracold Fermi gases near the broad Feshbach resonance, where the interaction can be characterized by the contact-type interaction, the interaction range in general becomes important in the density-induced BEC-BCS crossover discussed in the context of condensed-matter and nuclear systems. Characterizing the non-local interaction in terms of the low-energy constants such as scattering length $a$ and effective range $r$, we show how the crossover phenomena are affected by nonzero effective ranges. In particular, we show that the superfluid order parameter is strongly suppressed in the high-density regime and the sound velocity exhibits a non-monotonic behavior reflecting mechanical stability of the system. Moreover, we point out that the high-momentum tail associated with the contact parameter can be visible when the magnitude of momentum $k$ is much less than $1/r$.
description: 31 pages, 11 figures, In this version, several mistakes and typos have been corrected. The Appendix C for the dilute BEC limit and the molecule-molecule repulsion has been added. The discussion about the nuclear contact has been updated
Symmetry-controlled temporal structure of high-harmonic carrier fields from a bulk crystal
Creators: name: Langer, Fabian
name: Hohenleutner, Matthias
name: Huttner, U.
name: Koch, S. W.
name: Kira, M.
name: Huber, Rupert
Publisher: name: Universität Regensburg
Year: 2017
Subjects: subject: 530 Physik

description: High-harmonic (HH) generation in crystalline solids1, 2, 3, 4, 5, 6 marks an exciting development, with potential applications in high-efficiency attosecond sources7, all-optical bandstructure reconstruction8, 9 and quasiparticle collisions10, 11. Although the spectral1, 2, 3, 4 and temporal shape5 of the HH intensity has been described microscopically1, 2, 3, 4, 5, 6, 12, the properties of the underlying HH carrier wave have remained elusive. Here, we analyse the train of HH waveforms generated in a crystalline solid by consecutive half cycles of the same driving pulse. Extending the concept of frequency combs13, 14, 15 to optical clock rates, we show how the polarization and carrier-envelope phase (CEP) of HH pulses can be controlled by the crystal symmetry. For certain crystal directions, we can separate two orthogonally polarized HH combs mutually offset by the driving frequency to form a comb of even and odd harmonic orders. The corresponding CEP of successive pulses is constant or offset by π, depending on the polarization. In the context of a quantum description of solids, we identify novel capabilities for polarization- and phase-shaping of HH waveforms that cannot be accessed with gaseous sources.
Conformal Gravity and Extensions of Critical Gravity
Creators: name: Lu, H.
name: Pang, Yi
name: Pope, C. N.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Higher-order curvature corrections involving the conformally-invariant Weyl-squared action have played a role in two recent investigations of four-dimensional gravity; in critical gravity, where it is added to the standard cosmological Einstein-Hilbert action with a coefficient tuned to make the massive ghostlike spin-2 excitations massless, and in a pure Weyl-squared action considered by Maldacena, where the massive spin-2 modes are removed by the imposition of boundary conditions. We exhibit the connections between the two approaches, and we also generalise critical gravity to a wider class of Weyl-squared modifications to cosmological Einstein gravity where one can eliminate the massive ghostlike spin-2 modes by means of boundary conditions. The cosmological constant plays a crucial role in the discussion, since there is then a "window" of negative mass-squared spin-2 modes around AdS_4 that are not tachyonic. We also construct analogous conformal and non-conformal gravities in six dimensions.
description: Latex, 20 pages, typos in (4.21) and (A.7) were corrected
Big Bang Nucleosynthesis constraints on varying electron mass solution to the Hubble tension
Creators: name: Seto, Osamu
name: Toda, Yo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: A cosmological model with a time-varying mass of electrons seems a promising solution for the so-called Hubble tension. We examine the big bang nucleosynthesis (BBN) constraints on the time-varying electron mass model, because a larger electron mass gives rise to the smaller neutron decay rate which could affect the light element abundance. Additionally, different inferred cosmological parameters, primarily baryon asymmetry, to keep the cosmic background power spectrum unchanged could affect the abundance of light element. We find that the predicted helium fraction becomes larger and the deuterium abundance becomes smaller as the electron mass at the BBN time becomes larger. Thus, we conclude that an acceptable electron mass at the BBN time would be only approximately 1% greater than the current electron mass.
description: version published in Phys. Rev. D, 11pages, 2figures
Far field subwavelength imaging and focusing using a wire medium based resonant metalens
Creators: name: Lemoult, Fabrice
name: Lerosey, Geoffroy
name: Fink, Mathias
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: This is the second article in a series of two dealing with the concept of "resonant metalens" we introduced recently [Phys. Rev. Lett. 104, 203901 (2010)]. It is a new type of lens capable of coding in time and radiating efficiently in the far field region sub-diffraction information of an object. A proof of concept of such a lens is performed in the microwave range, using a medium made out of a square lattice of parallel conducting wires with finite length. We investigate a sub-wavelength focusing scheme with time reversal and demonstrate experimentally spots with focal widths of λ/25. Through a cross-correlation based imaging procedure we show an image reconstruction with a resolution of λ/80. Eventually we discuss the limitations of such a lens which reside essentially in losses.
Dark Matter perspective of Left-Right symmetric gauge model
Creators: name: Bhattacharyya, Sanchari
name: Datta, Anindya
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We consider an incarnation of left-right symmetric model with a local gauge symmetry of $SU(3)_C \otimes SU(2)_L \otimes U(1)_L \otimes SU(2)_R \otimes U(1)_R$. Heavy scalars and fermions present in the {\bf 27} of $E_6$ are included in the matter sector along with the Standard Model fermions. Two such colour singlet fermions, $N$ and $l_S$, transforming as bi-doublet and singlet under $SU(2)$s respectively, can be potential candidates for Dark Matter (DM). Assignment of $U(1)$ charges for the matter fields restricts some of the exotic fermions to interact with the SM fermions. We study in some details the prospect of such fermionic dark matters by calculating relic densities and direct detection cross-sections by treating these particles as stand alone relic particles in turn. $N$, when treated as relic particle, would produce a direct-detection cross-section very high compared to the experimental upper limits. However, the interaction rate of $N$ can be controlled by introducing a dimension-6 operator involving two $N$ fields and two SM fermions and appropriately choosing the coupling constant. This in turn, makes the interaction rate of $N$ very high and yields a small relic density. On the other hand, $l_S$ for some chosen mass window, can give us right amount of relic, but its direct detection cross-section is too small. Keeping these in mind, we propose two-component model of DM, where both $N$ and $l_S$ contribute to the relic density, albeit with unequal proportion while the direct detection cross-section limits can be satisfied mainly by $N$ in presence of an extra dimension-6 interaction. We derive limits on such an interaction from XENON experiment.
description: 19 pages, 8 figures, 3 tables, to be appeared on NPB
Characteristics of the existing building with district heating grid, using as the demo site A and C, and its climate conditions
Creators: name: Köll, Rebekka
Publisher: name: Zenodo
Year: 2019
Subjects: SCORES project
district heating grid
building energy system
compact hybrid storage technologies
renewable energy
energy grid

description: This deliverable gives the main characteristics of the combined office and terraced houses complex, selected as demonstration building for Demo A and C of the SCORES project. Exchanges are coordinated with the technical partners of the consortium and with the owner of the demonstration site. It also includes an outlook for the preliminary system design and the SCORES future building.
Electric properties of the Beryllium-11 system in Halo EFT
Creators: name: Hammer, H. -W.
name: Phillips, D. R.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Nuclear Theory (nucl-th)
subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: We compute E1 transitions and electric radii in the Beryllium-11 nucleus using an effective field theory that exploits the separation of scales in this halo system. We fix the leading-order parameters of the EFT from measured data on the 1/2+ and 1/2- levels in Be-11 and the B(E1) strength for the transition between them. We then obtain predictions for the B(E1) strength for Coulomb dissociation of the Be-11 nucleus to the continuum. We also compute the charge radii of the 1/2+ and 1/2- states. Agreement with experiment within the expected accuracy of a leading-order computation in this EFT is obtained. We also discuss how next-to-leading-order (NLO) corrections involving both s-wave and p-wave neutron-Be-10 interactions affect our results, and display the NLO predictions for quantities which are free of additional short-distance operators at this order. Information on neutron-Be-10 scattering in the relevant channels is inferred.
description: 27 pages, 8 figures, final version
Non-contraction of heat flow on Minkowski spaces
Creators: name: Ohta, Shin-ichi
name: Sturm, Karl-Theodor
Publisher: name: arXiv
Year: 2010
Subjects: subject: Analysis of PDEs (math.AP)
subject: Differential Geometry (math.DG)
subject: Probability (math.PR)
subject: FOS: Mathematics

description: We study contractivity properties of gradient flows for functions on normed spaces or, more generally, on Finsler manifolds. Contractivity of the flows turns out to be equivalent to a new notion of convexity for the functions. This is different from the usual convexity along geodesics in non-Riemannian Finsler manifolds. As an application, we show that the heat flow on Minkowski normed spaces other than inner product spaces is not contractive with respect to the quadratic Wasserstein distance.
description: 26 pages; minor revisions, to appear in Arch. Ration. Mech. Anal
Democratic actions for type II supergravities
Creators: name: Mkrtchyan, Karapet
name: Valach, Fridrich
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We present a universal democratic Lagrangian for the bosonic sector of ten-dimensional type II supergravities, treating "electric" and "magnetic" potentials of all RR fields on equal footing. For type IIB, this includes the five-form whose self-duality equation is derived from the Lagrangian. We also present an alternative form of the action for type IIB, with manifest $SL(2,\mb R)$ symmetry.
description: 4+2 pages (modified title, minor improvements, published version)
A distributed control strategy for reactive power compensation in smart microgrids
Creators: name: Bolognani, Saverio
name: Zampieri, Sandro
Publisher: name: arXiv
Year: 2011
Subjects: subject: Optimization and Control (math.OC)
subject: Systems and Control (eess.SY)
subject: FOS: Mathematics
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: We consider the problem of optimal reactive power compensation for the minimization of power distribution losses in a smart microgrid. We first propose an approximate model for the power distribution network, which allows us to cast the problem into the class of convex quadratic, linearly constrained, optimization problems. We then consider the specific problem of commanding the microgenerators connected to the microgrid, in order to achieve the optimal injection of reactive power. For this task, we design a randomized, gossip-like optimization algorithm. We show how a distributed approach is possible, where microgenerators need to have only a partial knowledge of the problem parameters and of the state, and can perform only local measurements. For the proposed algorithm, we provide conditions for convergence together with an analytic characterization of the convergence speed. The analysis shows that, in radial networks, the best performance can be achieved when we command cooperation among units that are neighbors in the electric topology. Numerical simulations are included to validate the proposed model and to confirm the analytic results about the performance of the proposed algorithm.
Collaborative Landmark Mining with a Gamification Approach
Creators: name: Bockes, Florian
name: Edel, Laura
name: Ferstl, Matthias
name: Schmid, Andreas
Publisher: name: Universität Regensburg
Year: 2015
Subjects: subject: crowdsourcing, gamification, landmarks
subject: 004 Informatik
subject: 020 Bibliotheks- und Informationswissenschaft

description: In the field of pedestrian navigation some systems use prominent identifying features, so called landmarks. Attributes of high-quality landmarks are recognizability, actuality, uniqueness and noticeability. One of the challenges of this kind of navigation systems is to collect and evaluate landmarks with consistent quality. The system we developed solves these struggles with a crowdsourcing approach. We combine this with gamification elements in order to reach many users and to assure long-term motivation. Our system shows images of existing landmarks to the player, which he is afterwards asked to assign to a map of the university. Depending on the distance of his guess to the real position the player earns points. The application strives to encourage users to upload and rate pictures of existing landmarks. A multiplayer mode which allows challenging other users keeps them involved. In contrast to other products, our system does not rely on localization via GPS. Another goal was to implement a self-running system with a minimal amount of dedicated administration needed. Therefore the users with the highest scores are rating the submitted content.
description: veröffentlicht in: Proceedings of the 14th International Conference on Mobile and Ubiquitous Multimedia Pages 364-367. Linz, Austria — November 30 - December 02, 2015 ISBN: 978-1-4503-3605-5
Probing spin helical surfaces states in topological HgTe nanowires
Creators: name: Ziegler, Johannes
name: Kozlovsky, Raphael
name: Gorini, Cosimo
name: Liu, Ming-Hao
name: Weishäupl, Sabine Josefine
name: Maier, Hubert
name: Fischer, Ralf
name: Kozlov, D. A.
name: Kvon, Z. D.
name: Mikhailov, N.
name: Dvoretsky, S. A.
name: Richter, Klaus
name: Weiss, Dieter
Publisher: name: Universität Regensburg
Year: 2018
Subjects: subject: 530 Physik

description: Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5μm when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h/e-periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.
Humanities discourse in games classroom: research through design with Games4Impact
Creators: name: Tece Bayrak, Aslı
Publisher: name: Media Design School
Year: 2024
Subjects: classificationCode: 390102
subject: Curriculum and pedagogy theory and development
classificationCode: 390101
subject: Creative arts, media and communication curriculum and pedagogy
classificationCode: 360502
subject: Computer gaming and animation

description: Abstract: Game development education is commonly considered to focus on game production with branching areas of game design, game programming or game art; nonetheless, developing games include more than what these three disciplines—design, software development, art— bring to the table. Acknowledging the transdisciplinary nature of games, we present a classroom approach that explores the social, cultural and humanistic identity of games via research through design while also encouraging students to leverage the expressive power of games. The merit of this approach is using game making as a space to ignite inquiry on socio-cultural contexts and facilitate an exploration for complex topics in a playful manner. This paper presents a reflective practice, methods of inquiry, and case examples to effectively apply design research in a project-based classroom environment. Case examples demonstrate strengths of the application for student learning and for the actualisation of design research in the classroom.
Dirac Equation at Finite Temperature
Creators: name: Wu, Xiang-Yao
name: Zhang, Bo-Jun
name: Liu, Xiao-Jing
name: Ba, Nuo
name: Wu, Yi-Heng
name: Zhang, Si-Qi
name: Wang, Jing
name: Li, Chun-Hong
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Physics (physics.gen-ph)
subject: FOS: Physical sciences

description: In this paper, we propose finite temperature Dirac equation, which can describe the quantum systems in an arbitrary temperature for a relativistic particle of spin-1/2. When the temperature T=0, it become Dirac equation. With the equation, we can study the relativistic quantum systems in an arbitrary temperature.
description: arXiv admin note: text overlap with arXiv:1005.2751, arXiv:hep-ph/0004125, arXiv:hep-ph/0005272 by other authors
Integrable equations associated with the finite-temperature deformation of the discrete Bessel point process
Creators: name: Cafasso, Mattia
name: Ruzza, Giulio
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mathematical Physics (math-ph)
subject: Probability (math.PR)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We study the finite-temperature deformation of the discrete Bessel point process. We show that its largest particle distribution satisfies a reduction of the 2D Toda equation, as well as a discrete version of the integro-differential Painlevé II equation of Amir-Corwin-Quastel, and we compute initial conditions for the Poissonization parameter equal to 0. As proved by Betea and Bouttier, in a suitable continuum limit the last particle distribution converges to that of the finite-temperature Airy point process. We show that the reduction of the 2D Toda equation reduces to the Korteweg-de Vries equation, as well as the discrete integro-differential Painlevé II equation reduces to its continuous version. Our approach is based on the discrete analogue of Its-Izergin-Korepin-Slavnov theory of integrable operators developed by Borodin and Deift.
description: 28 pages. V2: minor corrections
Diagram spaces and symmetric spectra
Creators: name: Sagave, Steffen
name: Schlichtkrull, Christian
Publisher: name: arXiv
Year: 2011
Subjects: subject: Algebraic Topology (math.AT)
subject: FOS: Mathematics

description: We present a general homotopical analysis of structured diagram spaces and discuss the relation to symmetric spectra. The main motivating examples are the I-spaces, which are diagrams indexed by finite sets and injections, and J-spaces, which are diagrams indexed by the Grayson-Quillen construction on the category of finite sets and bijections. We show that the category of I-spaces provides a convenient model for the homotopy category of spaces in which every E-infinity space can be rectified to a strictly commutative monoid. Similarly, the commutative monoids in the category of J-spaces model graded E-infinity spaces. Using the theory of J-spaces we introduce the graded units of a symmetric ring spectrum. The graded units detect periodicity phenomena in stable homotopy and we show how this can be applied to the theory of topological logarithmic structures.
description: v2: 70 pages. Minor revisions, to appear in Adv. Math
Circulating Marangoni flows within droplets in smectic films
Creators: name: Pikina, E. S.
name: Shishkin, M. A.
name: Kolegov, K. S.
name: Ostrovskii, B. I.
name: Pikin, S. A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We present theoretical study and numerical simulation of Marangoni convection within ellipsoidal isotropic droplets embedded in free standing smectic films (FSSF). The thermocapillary flows are analyzed for both isotropic droplets spontaneously formed in FSSF overheated above the bulk smectic-isotropic transition, and oil lenses deposited on the surface of the smectic film. The realistic model, for which the upper drop interface is free from the smectic layers, while at the lower drop surface the smectic layering still persists is considered in detail. For isotropic droplets and oil lenses this leads effectively to a sticking of fluid motion at the border with a smectic shell. The above mentioned asymmetric configuration is realized experimentally when the temperature of the upper side of the film is higher than at the lower one. The full set of stationary solutions for Stokes stream functions describing the Marangoni convection flows within the ellipsoidal drops were derived analytically. The temperature distribution in the ellipsoidal drop and the surrounding air was determined in the frames of the perturbation theory. As a result the analytical solutions for the stationary thermocapillary convection were derived for different droplet ellipticity ratios and the heat conductivity of the liquid crystal and air. In parallel, the numerical hydrodynamic calculations of the thermocapillary motion in the drops were performed. Both the analytical and numerical simulations predict the axially-symmetric circulatory convection motion determined by the Marangoni effect at the droplet free surface. Due to a curvature of the drop interface a temperature gradient along its free surface always persists. Thus, the thermocapillary convection within the ellipsoidal droplets in overheated FSSF is possible for the arbitrarily small Marangoni numbers.
Contextual and temporal variability in large-scale functional network interactions underlying attention
Creators: name: Dixon, Matthew Luke
Publisher: name: University of British Columbia
Year: 2017

description: Attentional mechanisms filter and constrain the flow of information processing so that only the most relevant interoceptive and exteroceptive signals are highlighted for further processing. A variety of brain networks play a role in different facets of attention, including the default network, dorsal attention network, salience network, and frontoparietal control network. The present research used functional magnetic resonance imaging (fMRI) and graph theoretic analyses to examine the extent to which interactions between these large-scale brain networks vary across time and different contexts. We addressed the following questions: (i) is there a fundamental competition between networks involved in attending to perceptual versus conceptual information? (ii) is the frontoparietal control network―the key network implicated in the deliberate control of attention―a domain general system, or does it exhibit a finer level of organization related to perceptual versus conceptual attention? and (iii) how does network configuration vary during different modes of internally-directed attention characterized by conceptual elaboration versus interoceptive awareness? Our findings provide novel insights into these fundamental questions, and provide evidence that network organization dynamically changes across time and context. These findings caution against using resting state data to make general inferences about brain organization.
The Random Integral Representation Conjecture: a quarter of a century later
Creators: name: Jurek, Zbigniew J.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Probability (math.PR)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: Primary 60F05, 60E07, 60B11, Secondary 60H05, 60B10

description: In Jurek 1985 and 1988 the random integral representations conjecture was stated. It claims that (some) limit laws can be written as probability distributions of random integrals of the form $\int_{(a,b]}h(t)dY_ν(r(t))$, for some deterministic functions $h$, $r$ and a Lévy process $Y_ν(t),t\ge 0$. Here we review situations where a such claim holds true. Each theorem is followed by a remark which gives references to other related papers, results as well as some historical comments. Moreover, some open questions are stated.
Simultaneous Control of Bandfilling and Bandwidth in Electric Double-Layer Transistor Based on Organic Mott Insulator $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl
Creators: name: Kawasugi, Yoshitaka
name: Yamamoto, Hiroshi M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The physics of quantum many-body systems have been studied using bulk correlated materials, and recently, moiré superlattices formed by atomic bilayers have appeared as a novel platform in which the carrier concentration and the band structures are highly tunable. In this brief review, we introduce an intermediate platform between those systems, namely, a band-filling- and bandwidth-tunable electric double-layer transistor based on a real organic Mott insulator $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl. In the proximity of the bandwidth-control Mott transition at half filling, both electron and hole doping induced superconductivity (with almost identical transition temperatures) in the same sample. The normal state under electric double-layer doping exhibited non-Fermi liquid behaviors as in many correlated materials. The doping levels for the superconductivity and the non-Fermi liquid behaviors were highly doping-asymmetric. Model calculations based on the anisotropic triangular lattice explained many phenomena and the doping asymmetry, implying the importance of the noninteracting band structure (particularly the flat part of the band).
description: 15 pages, 12 figures
Exceptional Sequences on Rational C*-Surfaces
Creators: name: Hochenegger, Andreas
name: Ilten, Nathan Owen
Publisher: name: arXiv
Year: 2011
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: Primary: 14M25, 14F05, Secondary: 14D06

description: Inspired by Bondal's conjecture, we study the behavior of exceptional sequences of line bundles on rational C*-surfaces under homogeneous degenerations. In particular, we provide a sufficient criterion for such a sequence to remain exceptional under a given degeneration. We apply our results to show that, for toric surfaces of Picard rank 3 or 4, all full exceptional sequences of line bundles may be constructed via augmentation. We also discuss how our techniques may be used to construct noncommutative deformations of derived categories.
description: 30 pages, 11 figures. Some parts of this preprint originally appeared in arXiv:0906.4292v2 but have been revised and expanded upon. Minor changes, to appear in Manuscripta Mathematica
On data-driven chance constraint learning for mixed-integer optimization problems
Creators: name: Alcántara, Antonio
name: Ruiz, Carlos
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optimization and Control (math.OC)
subject: Machine Learning (stat.ML)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: When dealing with real-world optimization problems, decision-makers usually face high levels of uncertainty associated with partial information, unknown parameters, or complex relationships between these and the problem decision variables. In this work, we develop a novel Chance Constraint Learning (CCL) methodology with a focus on mixed-integer linear optimization problems which combines ideas from the chance constraint and constraint learning literature. Chance constraints set a probabilistic confidence level for a single or a set of constraints to be fulfilled, whereas the constraint learning methodology aims to model the functional relationship between the problem variables through predictive models. One of the main issues when establishing a learned constraint arises when we need to set further bounds for its response variable: the fulfillment of these is directly related to the accuracy of the predictive model and its probabilistic behaviour. In this sense, CCL makes use of linearizable machine learning models to estimate conditional quantiles of the learned variables, providing a data-driven solution for chance constraints. An open-access software has been developed to be used by practitioners. Furthermore, benefits from CCL have been tested in two real-world case studies, proving how robustness is added to optimal solutions when probabilistic bounds are set for learned constraints.
Making Internal Software Startups Work: How to Innovate Like a Venture Builder?
Creators: name: Tkalich, Anastasiia
name: Moe, Nils Brede
name: Ulfsnes, Rasmus
Publisher: name: arXiv
Year: 2022
Subjects: subject: Software Engineering (cs.SE)
subject: FOS: Computer and information sciences

description: With the increasing availability of software usage and the influence of the Lean Startup mindset, more and more companies choose to innovate through internal software startups. Such startups aim at developing new business models while at the same time relying on the resources from the companies where they emerged. The evidence from both researchers and practitioners indicates that driving internal software startups is challenging. This paper seeks to address this problem by asking the research question: how to make internal software startups work? We examined a unique case of a venture builder, a company primarily focusing on building internal software startups and launching them as independent companies. Applying a Grounded Theory approach, we analyzed data on four internal software startups at the case company. The results suggest that four strategies drive the examined startups, cultural, financial, personnel, and venture arrangement. We interpret our results by drawing on earlier literature on intrapreneurship and internal ventures and suggest four recommendations to succeed with internal software startups 1 establish shared arenas for the employees, 2 provide necessary resources for experimentation in the initial phase and increase them incrementally, 3 build up in-house product management competence through coaching, and 4 harness employees own motivation to develop their own ideas.
description: International Conference on Software Business
PyMAF-X: Towards Well-aligned Full-body Model Regression from Monocular Images
Creators: name: Zhang, Hongwen
name: Tian, Yating
name: Zhang, Yuxiang
name: Li, Mengcheng
name: An, Liang
name: Sun, Zhenan
name: Liu, Yebin
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: We present PyMAF-X, a regression-based approach to recovering parametric full-body models from monocular images. This task is very challenging since minor parametric deviation may lead to noticeable misalignment between the estimated mesh and the input image. Moreover, when integrating part-specific estimations into the full-body model, existing solutions tend to either degrade the alignment or produce unnatural wrist poses. To address these issues, we propose a Pyramidal Mesh Alignment Feedback (PyMAF) loop in our regression network for well-aligned human mesh recovery and extend it as PyMAF-X for the recovery of expressive full-body models. The core idea of PyMAF is to leverage a feature pyramid and rectify the predicted parameters explicitly based on the mesh-image alignment status. Specifically, given the currently predicted parameters, mesh-aligned evidence will be extracted from finer-resolution features accordingly and fed back for parameter rectification. To enhance the alignment perception, an auxiliary dense supervision is employed to provide mesh-image correspondence guidance while spatial alignment attention is introduced to enable the awareness of the global contexts for our network. When extending PyMAF for full-body mesh recovery, an adaptive integration strategy is proposed in PyMAF-X to produce natural wrist poses while maintaining the well-aligned performance of the part-specific estimations. The efficacy of our approach is validated on several benchmark datasets for body, hand, face, and full-body mesh recovery, where PyMAF and PyMAF-X effectively improve the mesh-image alignment and achieve new state-of-the-art results. The project page with code and video results can be found at https://www.liuyebin.com/pymaf-x.
description: Accepted to IEEE TPAMI, Project page: https://www.liuyebin.com/pymaf-x, An eXpressive extension of PyMAF [arXiv:2103.16507] for monocular human/hand/face/full-body mesh recovery
Axion-Photon Interaction from Nonminimal Dimension-5 Lorentz-Violating Operators
Creators: name: Carvalho, A. J. G.
name: Dias, A. G.
name: Ferrari, A. F.
name: Mariz, T.
name: Nascimento, J. R.
name: Petrov, A. Yu.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this paper, we discuss various possible schemes for the perturbative generation of the axion-photon interaction term in different Lorentz-breaking extensions of QED, involving operators with mass dimensions up to 5. We demonstrate explicitly that there are only a few schemes allowing to generate a finite axion-photon interaction term from one-loop radiative corrections, and within all these schemes, the generated term turns out to be ambiguous.
description: 18 pages, version accepted to PRD
Inferring the Energy and Distance Distributions of Fast Radio Bursts using the First CHIME/FRB Catalog
Creators: name: Shin, Kaitlyn
name: Masui, Kiyoshi W.
name: Bhardwaj, Mohit
name: Cassanelli, Tomas
name: Chawla, Pragya
name: Dobbs, Matt
name: Dong, Fengqiu Adam
name: Fonseca, Emmanuel
name: Gaensler, B. M.
name: Herrera-Martín, Antonio
name: Kaczmarek, Jane
name: Kaspi, Victoria
name: Leung, Calvin
name: Merryfield, Marcus
name: Michilli, Daniele
name: Münchmeyer, Moritz
name: Pearlman, Aaron B.
name: Rafiei-Ravandi, Masoud
name: Smith, Kendrick
name: Stairs, Ingrid
name: Tendulkar, Shriharsh P.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Fast radio bursts (FRBs) are brief, energetic, extragalactic flashes of radio emission whose progenitors are largely unknown. Although studying the FRB population is essential for understanding how these astrophysical phenomena occur, such studies have been difficult to conduct without large numbers of FRBs and characterizable observational biases. Using the recently released catalog of 536 FRBs published by the Canadian Hydrogen Intensity Mapping Experiment/Fast Radio Burst (CHIME/FRB) collaboration, we present a study of the FRB population that also calibrates for selection effects. Assuming a Schechter luminosity function, we infer a characteristic energy cut-off of $E_\mathrm{char} =$ $2.38^{+5.35}_{-1.64} \times 10^{41}$ erg and a differential power-law index of $γ=$ $-1.3^{+0.7}_{-0.4}$. Simultaneously, we infer a volumetric rate of [$7.3^{+8.8}_{-3.8}$(stat.)$^{+2.0}_{-1.8}$(sys.)]$\times 10^4$ Gpc$^{-3}$ year$^{-1}$ above a pivot energy of 10$^{39}$ erg and below a scattering timescale of 10 ms at 600 MHz, and find we cannot significantly constrain the cosmic evolution of the FRB population with star formation rate. Modeling the host dispersion measure (DM) contribution as a log-normal distribution and assuming a total Galactic contribution of 80 pc cm$^{-3}$, we find a median value of $\mathrm{DM}_\mathrm{host} =$ $84^{+69}_{-49}$ pc cm$^{-3}$, comparable with values typically used in the literature. Proposed models for FRB progenitors should be consistent with the energetics and abundances of the full FRB population predicted by our results. Finally, we infer the redshift distribution of FRBs detected with CHIME, which will be tested with the localizations and redshifts enabled by the upcoming CHIME/FRB Outriggers project.
description: Revised to reflect published version
COMET: Clustering Observables Modelled by Emulated perturbation Theory
Creators: name: Eggemeier, Alexander
name: Camacho-Quevedo, Benjamin
name: Pezzotta, Andrea
name: Crocce, Martin
name: Scoccimarro, Román
name: Sánchez, Ariel G.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: In this paper we present COMET, a Gaussian process emulator of the galaxy power spectrum multipoles in redshift-space. The model predictions are based on one-loop perturbation theory and we consider two alternative descriptions of redshift-space distortions: one that performs a full expansion of the real- to redshift-space mapping, as in recent effective field theory models, and another that preserves the non-perturbative impact of small-scale velocities by means of an effective damping function. The outputs of COMET can be obtained at arbitrary redshifts (up to $z \sim 3$), for arbitrary fiducial background cosmologies, and for a large parameter space that covers the shape parameters $ω_c$, $ω_b$, and $n_s$, as well as the evolution parameters $h$, $A_s$, $Ω_K$, $w_0$, and $w_a$. This flexibility does not impair COMET's accuracy, since we exploit an exact degeneracy between the evolution parameters that allows us to train the emulator on a significantly reduced parameter space. While the predictions are sped up by at least two orders of magnitude, validation tests reveal an accuracy of $0.1\,\%$ for the monopole and quadrupole ($0.3\,\%$ for the hexadecapole), or alternatively, better than $0.25\,σ$ for all three multipoles in comparison to statistical uncertainties expected for the Euclid survey with a tenfold increase in volume. We show that these differences translate into shifts in mean posterior values that are at most of the same size, meaning that COMET can be used with the same confidence as the exact underlying models. COMET is a publicly available Python package that also provides the tree-level bispectrum multipoles in redshift-space and Gaussian covariance matrices.
description: 19 pages, 11 figures; for the COMET Python package, see https://gitlab.com/aegge/comet-emu; v2: added discussion on binning and discreteness effects, minor improvements to match published version
Longitudinal and transverse modes of temperature modulated inclined layer convection
Creators: name: Singh, Jitender
Publisher: name: arXiv
Year: 2022
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Numerical Analysis (math.NA)
subject: Computational Physics (physics.comp-ph)
subject: Geophysics (physics.geo-ph)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: 76E06, 76D55

description: A parametric instability of an incompressible, viscous, and Boussinesq fluid layer bounded between two parallel planes is investigated numerically. The layer is assumed to be inclined at an angle with horizontal. The planes bounding the layer are subjected to a time-periodic heating. Above a threshold value, the temperature gradient across the layer leads to an instability of an initially quiescent state or a parallel flow, depending upon the angle of inclination. The Floquet analysis of the underlying system reveals that under modulation, the instability sets in as a convective roll pattern executing harmonic or subharmonic oscillations, depending upon the modulation, the angle of inclination, and Prandtl number of the fluid. Under modulation, the value of the angle of inclination for the codimension-2 point is found to be a nonconstant function of the amplitude and the frequency of modulation. Further, the instability response in the fluid layer as a longitudinal mode is always harmonic whereas the instability response as a transverse mode is harmonic, or subharmonic, or bicritical depending upon the modulation. The temperature modulation offers a good control of time-periodic heat and mass transfer in the inclined layer convection.
description: 24 Pages
Effects of inhomogeneities on apparent cosmological observables: "fake" evolving dark energy
Creators: name: Romano, Antonio Enea
name: Sasaki, Misao
name: Starobinsky, Alexei A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Using the exact Lemaitre-Bondi-Tolman solution with a non-vanishing cosmological constant $Λ$, we investigate how the presence of a local spherically-symmetric inhomogeneity can affect apparent cosmological observables, such as the deceleration parameter or the effective equation of state of dark energy (DE), derived from the luminosity distance under the assumption that the real space-time is exactly homogeneous and isotropic. The presence of a local underdensity is found to produce apparent phantom behavior of DE, while a locally overdense region leads to apparent quintessence behavior. We consider relatively small large scale inhomogeneities which today are not linear and could be seeded by primordial curvature perturbations compatible with CMB bounds. Our study shows how observations in an inhomogeneous $Λ$CDM universe with initial conditions compatible with the inflationary beginning, if interpreted under the wrong assumption of homogeneity, can lead to the wrong conclusion about the presence of "fake" evolving dark energy instead of $Λ$.
description: 22 pages, 19 figures,Final version to appear in European Physical Journal C
Stability of Hairy Black Holes in Shift-Symmetric Scalar-Tensor Theories via the Effective Field Theory Approach
Creators: name: Khoury, Justin
name: Noumi, Toshifumi
name: Trodden, Mark
name: Wong, Sam S. C.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Shift-symmetric Horndeski theories admit an interesting class of Schwarzschild-de Sitter black hole solutions exhibiting time-dependent scalar hair. The properties of these solutions may be studied via a bottom-up effective field theory (EFT) based on the background symmetries. This is in part possible by making use of a convenient coordinate choice -- Lemaître-type coordinates -- in which the profile of the Horndeski scalar field is linear in the relevant time coordinate. We construct this EFT, and use it to understand the stability of hairy black holes in shift-symmetric Horndeski theories, providing a set of constraints that the otherwise-free functions appearing in the Horndeski Lagrangian must satisfy in order to admit stable black hole solutions. The EFT is analyzed in the decoupling limit to understand potential sources of instability. We also perform a complete analysis of the EFT with odd-parity linear perturbations around general spherically symmetric space-time.
description: 25 pages, JCAP version
Frequency-dependent Phonon-mediated Unidirectional Magnetoresistance in a Metal on an Insulator with Highly Nonequilibrium Magnons
Creators: name: Sullivan, Sean E.
name: Lee, Hwijong
name: Weathers, Annie
name: Shi, Li
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Heavy metal (HM)/magnet bilayers host many magnetoresistances (MR) and spin caloritronic effects. Here we show that the spin Peltier effect and electron-phonon scattering produce much larger unidirectional MR of an HM on a magnetic insulator than existing theories that neglect the interplay between MR and spin caloritronic effects. By accounting for local nonequilibrium in both the magnon chemical potential and temperature, our analytical model attributes the observed frequency dependence of the spin Peltier MR and the spin Seebeck effect to the reduction of the thermal penetration depth, which approaches the 1 micron scale magnon spin diffusion length at high frequencies.
description: SES and HL contributed equally. Main paper: 13 pages, 4 figures; supplemental: 44 pages, 16 figures