Luiza Angheluta-Bauer

• Singh, Aditya; Rønning, Jonas; Liu, Chien-Chia; Angheluta, Luiza; Concha, Andres & Bandi, Mahesh M. (2026). Topology made visible through standing waves in a spinning fluid. Communications Physics. 9(1). doi: 10.1038/s42005-026-02603-w. Fulltekst i vitenarkiv Vis sammendrag

  Wave-topology interactions underlie phenomena across physics, from condensed matter to cosmology, with the Aharonov-Bohm (AB) effect providing a paradigmatic example. Classical analogues in fluid dynamics have shown that travelling surface waves scattered off vortices develop wavefront dislocations, with topological effects studied close to the vortex core. Here, we demonstrate that standing surface waves scattered by a single vortex give rise to global nodal structures – lines of zero wave amplitude – whose number is quantized, and may oscillate in time. This behaviour reveals a non-local topological response, in contrast with previously reported, spatially confined interactions. Our findings establish hydrodynamics as a versatile platform for exploring wave-topology interplay and quantum interference phenomena, such as AB caging and topological localization, with potential implications for photonic, acoustic, and quantum metamaterials.

• Øvereng, Vebjørn; Baggaley, Andrew & Angheluta, Luiza (2025). Topological interactions in vortex-wave collisions in Bose-Einstein condensates. http://www.arxiv.org/physics. doi: 10.48550/ARXIV.2510.01973. Fulltekst i vitenarkiv
• Donno, Marcello De; Angheluta, Luiza & Salvalaglio, Marco (2025). Modeling dislocations in quasicrystals through amplitude equations. Computer Methods in Applied Mechanics and Engineering. ISSN 0045-7825. 446. doi: 10.1016/j.cma.2025.118324. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Ho, Richard David Jun-Geet & Angheluta, Luiza (2025). Emergent cell migration from cell shape deformations and T1 transitions. Physical Review Research (PRResearch). 7(3). doi: 10.1103/d6qj-775d. Fulltekst i vitenarkiv Vis sammendrag

  T1 transitions—cell neighbor exchanges—are key drivers of tissue remodeling and fluidization in epithelial monolayers. Using a multiphase field (MPF) model that accounts for dynamic cell shapes, alongside an active elastic solid model lacking cell shape degrees of freedom, we study the spatiotemporal organization of T1 transitions. While individual T1 transitions occur as a Poisson process in time, their spatial distribution is strongly influenced by local cell shape deformations. We identify a dual mechanical response: cells losing neighbors tend to relax their shape isotropically, whereas cells gaining neighbors undergo anisotropic elongation. By analyzing successive T1 events in the MPF model, we find asymmetric spatial patterns that depend on whether a cell gains or loses neighbors. These asymmetries lead to persistent, localized directional motion, even in the absence of external cues. Our results suggest an intrinsic mechanism for directed cell migration driven by local topological rearrangements mediated by cell shape dynamics—a process potentially relevant for epithelial flows during development, morphogenesis, and wound healing.

• Birnir, Björn & Angheluta, Luiza (2025). Scaling of Lagrangian structure functions. Physical Review Research (PRResearch). 7(2). doi: 10.1103/physrevresearch.7.023225. Fulltekst i vitenarkiv Vis sammendrag

  We use stochastic closure theory and generalized Green-Kubo relations to show that the velocity structure functions have two distinct scaling regimes connected by a passover. Initially, after a brief ballistic (Batchelor) scaling, the structure functions exhibit a Lagrangian scaling regime with no intermittency, and then pass over to a regime with Eulerian scaling, with intermittency. This transition time for the passover region is controlled by the second structure function, through a generalization of Green-Kubo-Obukhov relations. The ultimate time interval of decay seems to be controlled by the scaling of free eddies, analogous to the scaling in the buffer layer of boundary layer turbulence [B. Birnir, L. Angheluta, J. Kaminsky, and X. Chen, Spectral link of the Generalized Townsend-Perry constants in turbulent boundary layers, ]. The dip observed in the log-derivatives of the structure function [L. Biferale, E. Bodenschatz, M. Cencini, A. S. Lanotte, N. T. Ouellette, F. Toschi, and H. Xu, Lagrangian structure functions in turbulence: A quantitative comparison between experiment and direct numerical simulation, ], with respect to the second structure function S 2 , is caused only by the time scales probed by S 2 . It seems better to take the log-derivative with respect to t , instead of S 2 , to fully understand the different scaling regimes of Lagrangian turbulence.

• Angheluta, Luiza; Lång, Anna Ulrika; Lång, Emma & Bøe, Stig Ove (2025). Full-Integer Topological Defects in Polar Active Matter: From Collective Migration to Tissue Patterning. Annual Review of Condensed Matter Physics. 17, s. 305–325. doi: 10.1146/annurev-conmatphys-031620-105420. Fulltekst i vitenarkiv Vis sammendrag

  Polar active matter—including animal herds, aggregates of motile cells, and active colloids—often forms coordinated migration patterns, such as flocking. This orderly motion can be disrupted by full-integer topological defects representing localized disturbances in which directional alignment is lost. Such polar defects can serve as key organizing centers across scales, sustaining collective behavior such as swirling motion and other large-scale coherent states. Although significant progress has been made in understanding active matter principles in recent years, a quantitative understanding of how topological defects influence active polar matter is still needed. We present a brief overview of recent experimental observations in synthetic active colloids and various biological systems. We describe how polar defects mediate dynamical transitions and contribute to the spontaneous emergence of large-scale coherent states. We also discuss theoretical advances in the physical modeling of coupled processes involving polar defects and collective behavior in active polar matter.

• Angheluta, Luiza; Lång, Anna Ulrika; Lång, Emma & Bøe, Stig Ove (2025). Full-Integer Topological Defects in Polar Active Matter: From Collective Migration to Tissue Patterning. Annual Review of Condensed Matter Physics. doi: 10.1146/annurev-conmatphys-031620-105420. Fulltekst i vitenarkiv Vis sammendrag

  Polar active matter—including animal herds, aggregates of motile cells, and active colloids—often forms coordinated migration patterns, such as flocking. This orderly motion can be disrupted by full-integer topological defects representing localized disturbances in which directional alignment is lost. Such polar defects can serve as key organizing centers across scales, sustaining collective behavior such as swirling motion and other large-scale coherent states. Although significant progress has been made in understanding active matter principles in recent years, a quantitative understanding of how topological defects influence active polar matter is still needed. We present a brief overview of recent experimental observations in synthetic active colloids and various biological systems. We describe how polar defects mediate dynamical transitions and contribute to the spontaneous emergence of large-scale coherent states. We also discuss theoretical advances in the physical modeling of coupled processes involving polar defects and collective behavior in active polar matter.

• Alford, Patrick W.; Angheluta-Bauer, Luiza & Viñals, Jorge (2025). Biomechanics of orientationally ordered epithelial tissue. Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. ISSN 1364-5021. 481(2321). doi: 10.1098/rspa.2025.0364. Fulltekst i vitenarkiv
• Ho, Richard David Jun-Geet; Mossige, Joachim; Ponomartcev, Sergei; Natalia, Smirnova,; Sunny, Dai, Keqing & Hu, Xian [Vis alle 9 forfattere av denne artikkelen] (2025). [2509.08929] Spontaneous elongation of 3D gastruloids from local cell polarity alignment. arXiv. doi: https:/arxiv.org/abs/2509.08929. Fulltekst i vitenarkiv Vis sammendrag

  Gastruloids are 3D stem cell aggregate models for early embryogenesis that provide a unique platform to study how collective cell dynamics drive tissue symmetry breaking and axial elongation. Using 3D light sheet imaging, we show that a pulse of Chiron, a Wnt activator, induces coherent alignment of cell polarity during elongation. While nuclear elongation occurs with or without treatment, only Chiron-treated gastruloids exhibit quasi-long-range alignment of nuclear axes, linking cell polarity coherence to tissue-scale remodeling. A minimal physical model of polarized cells, incorporating alignment-dependent torques and polarity-mediated adhesion, reproduces symmetry breaking and elongation, demonstrating that local cell polarity alignment alone can drive tissue-scale convergence-extension flows.

• Myers, Lucas; Swift, Carter; Rønning, Jonas; Angheluta, Luiza & Viñals, Jorge (2024). A computational study of nematic core structure and disclination interactions in elastically anisotropic nematics. Soft Matter. ISSN 1744-683X. doi: 10.1039/d3sm01616a. Fulltekst i vitenarkiv
• Ho, Richard David Jun-Geet; Bøe, Stig Ove; Dysthe, Dag Kristian & Angheluta, Luiza (2024). Role of tissue fluidization and topological defects in epithelial tubulogenesis. Physical Review Research (PRResearch). 6(2), s. 1–10. doi: 10.1103/PhysRevResearch.6.023315. Fulltekst i vitenarkiv Vis sammendrag

  Cellular rearrangements, as primary sources of tissue fluidization, facilitate topological transitions during tissue morphogenesis. We study the role of intrinsic cell properties such as cell polarity and cell-cell adhesion in shaping epithelial tissues using a minimal model of interacting polarized cells. The presence of a vortex in the cell polarization poses the topological constraint that induces an inwards migration with the formation of a conical shape. Local rearrangements at the tip of the cone lead to the onset of tube formation. Switching between collective migration and structural rearrangements is key for balancing the contrasting tendencies, such as the tissue rigidity needed to preserve shape and the tissue fluidity allowing for topological transitions during tissue morphogenesis.

• Jain, Harish Pruthviraj; Voigt, Axel & Angheluta-Bauer, Luiza (2024). From cell intercalation to flow, the importance of T1 transitions. Physical Review Research (PRResearch). 6(3). doi: 10.1103/PhysRevResearch.6.033176. Fulltekst i vitenarkiv Vis sammendrag

  T1 transitions, also called cell intercalations, are important sources of fluidization of epithelial cell monolayers. We use a multiphase field model to quantify this tissue fluidization in terms of the relative dispersion of cells and characterize the T1 flow profile. We show that the ensemble-averaged flow profile of a T1 transition has a saddle-point pattern accompanied by a localized burst in cell speed. Although the temporal evolution of the relative dispersion of cells depends on specific model details, the different dispersion curves collapse robustly onto a linear function of the number of T1 transitions, implying an important connection between T1 transitions and mixing in dense systems.

• Donno, Marcello De; Angheluta, Luiza; Elder, Ken R. & Salvalaglio, Marco (2024). Mesoscale field theory for quasicrystals. Physical Review Research (PRResearch). 6(4). doi: 10.1103/PhysRevResearch.6.043285. Fulltekst i vitenarkiv Vis sammendrag

  We present a mesoscale field theory unifying the modeling of growth, elasticity, and dislocations in quasicrystals. The theory is based on the amplitudes entering their density-wave representation. We introduce a free energy functional for complex amplitudes and assume nonconserved dissipative dynamics to describe their evolution. Elasticity, including phononic and phasonic deformations, along with defect nucleation and motion, emerges self-consistently by prescribing only the symmetry of quasicrystals. Predictions on the formation of semicoherent interfaces and dislocation kinematics are given.

• Andersen, Benjamin H.; Renaud, Julian; Rønning, Jonas; Angheluta, Luiza & Doostmohammadi, Amin (2023). Symmetry-restoring crossover from defect-free to defect-laden turbulence in polar active matter. Physical Review Fluids. 8(6). doi: 10.1103/PhysRevFluids.8.063101. Fulltekst i vitenarkiv Vis sammendrag

  Coherent flows of self-propelled particles are characterized by vortices and jets that sustain chaotic flows, referred to as active turbulence. Here, we reveal a crossover between defect-free active turbulence and active turbulence laden with topological defects. Interestingly, we show that concurrent to the crossover from defect-free to defect-laden active turbulence is the restoration of the previously broken SO(2) symmetry signaled by the fast decay of the two-point correlations. By stability analyses of the topological charge density field, we provide theoretical insights on the criterion for the crossover to the defect-laden active turbulent state. Despite the distinct symmetry features between these two active turbulence regimes, the flow fluctuations exhibit universal statistical scaling behaviors at large scales, while the spectrum of polarity fluctuations decays exponentially at small length scales compared to the active energy injection length. These findings reveal a dynamical crossover between distinct spatiotemporal organization patterns in polar active matter.

• Rønning, Jonas; Renaud, Julian; Doostmohammadi, Amin & Angheluta, Luiza (2023). Spontaneous flows and dynamics of full-integer topological defects in polar active matter. Soft Matter. ISSN 1744-683X. doi: 10.1039/d3sm00316g. Fulltekst i vitenarkiv Vis sammendrag

  Polar active matter of self-propelled particles sustain spontaneous flows through the full-integer topological defects. We study theoretically the incompressible flow profiles around ±1 defects induced by polar and dipolar active forces. We show that dipolar forces induce vortical flows around the +1 defect, while the flow around the −1 defect has an 8-fold rotational symmetry. The vortical flow changes its chirality near the +1 defect core in the absence of the friction with a substrate. We show analytically that the flow induced by polar active forces is vortical near the +1 defect and is 4-fold symmetric near the −1 defect, while it becomes uniform in the far-field. For a pair of oppositely charged defects, this polar flow contributes to a mutual interaction force that depends only on the orientation of the defect pair relative to the background polarization, and that enhances defect pair annihilation. This is in contradiction with the effect of dipolar active forces which decay inversely proportional with the defect separation distance. As such, our analyses reveals a long-ranged mechanism for the pairwise interaction between topological defects in polar active matter.

• Skogvoll, Vidar; Rønning, Jonas; Salvalaglio, Marco & Angheluta, Luiza (2023). A unified field theory of topological defects and non-linear local excitations. npj Computational Materials. 9(1), s. 1–13. doi: 10.1038/s41524-023-01077-6. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Topological defects and smooth excitations determine the properties of systems showing collective order. We introduce a generic non-singular field theory that comprehensively describes defects and excitations in systems with O ( n ) broken rotational symmetry. Within this formalism, we explore fast events, such as defect nucleation/annihilation and dynamical phase transitions where the interplay between topological defects and non-linear excitations is particularly important. To highlight its versatility, we apply this formalism in the context of Bose-Einstein condensates, active nematics, and crystal lattices.

• Rønning, Jonas & Angheluta, Luiza (2023). Precursory patterns to vortex nucleation in stirred Bose-Einstein condensates. Physical Review Research (PRResearch). 5(2). doi: 10.1103/PhysRevResearch.5.023108. Fulltekst i vitenarkiv Vis sammendrag

  Within the Gross-Pitaevskii theory, we study precursory pattern formations to the nucleation of vortex dipoles in a two-dimensional Bose-Einstein condensate stirred by a Gaussian potential. We introduce a smooth superfluid vorticity field and its conservative current, which capture very well the gradual process of vortex nucleation as a mechanism of topological singularities acquiring smooth cores. This is characterized by the localization of the superfluid vorticity into core regions which harbor the phase slips. For more impenetrable obstacles, we find that there are additional phase slips that do not acquire cores, thus remaining pinned as ghost vortices to the potential. We show that the vortex kinematics is slaved to the superfluid vorticity current, which determines not only the onset of nucleation but also the shedding dynamics.

• Rønning, Jonas; Marchetti, M. Cristina & Angheluta, Luiza (2023). Defect self-propulsion in active nematic films with spatially varying activity. Royal Society Open Science. 10(2). doi: 10.1098/rsos.221229. Fulltekst i vitenarkiv Vis sammendrag

  We study the dynamics of topological defects in active nematic films with spatially varying activity and consider two set-ups: (i) a constant activity gradient and (ii) a sharp jump in activity. A constant gradient of extensile (contractile) activity endows the comet-like +1/2 defect with a finite vorticity that drives the defect to align its nose in the direction of decreasing (increasing) gradient. A constant gradient does not, however, affect the known self-propulsion of the +1/2 defect and has no effect on the −1/2 that remains a non-motile particle. A sharp jump in activity acts like a wall that traps the defects, affecting the translational and rotational motion of both charges. The +1/2 defect slows down as it approaches the interface and the net vorticity tends to reorient the defect polarization so that it becomes perpendicular to the interface. The −1/2 defect acquires a self-propulsion towards the activity interface, while the vorticity-induced active torque tends to align the defect to a preferred orientation. This effective attraction of the negative defects to the wall is consistent with the observation of an accumulation of negative topological charge at both active/passive interfaces and physical boundaries.

• Jain, Harish Pruthviraj; Voigt, Axel & Angheluta-Bauer, Luiza (2023). Robust statistical properties of T1 transitions in a multi-phase field model of cell monolayers. Scientific Reports. 13. doi: 10.1038/s41598-023-37064-6. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Large-scale tissue deformation which is fundamental to tissue development hinges on local cellular rearrangements, such as T1 transitions. In the realm of the multi-phase field model, we analyse the statistical and dynamical properties of T1 transitions in a confluent monolayer. We identify an energy profile that is robust to changes in several model parameters. It is characterized by an asymmetric profile with a fast increase in energy before the T1 transition and a sudden drop after the T1 transition, followed by a slow relaxation. The latter being a signature of the fluidity of the cell monolayer. We show that T1 transitions are sources of localised large deformation of the cells undergoing the neighbour exchange, and they induce other T1 transitions in the nearby cells leading to a chaining of events that propagate local cell deformation to large scale tissue flows.

• Skogvoll, Vidar; Salvalaglio, Marco & Angheluta, Luiza (2022). Hydrodynamic phase field crystal approach to interfaces, dislocations, and multi-grain networks. Modelling and Simulation in Materials Science and Engineering. ISSN 0965-0393. 30(8). doi: 10.1088/1361-651X/ac9493. Fulltekst i vitenarkiv
• Moen, Emily Qing Zang; Olsen, Kristian Stølevik; Rønning, Jonas & Angheluta, Luiza (2022). Trapping of active Brownian and run-and-tumble particles: A first-passage time approach. Physical Review Research (PRResearch). 4(4), s. 1–8. doi: 10.1103/PhysRevResearch.4.043012. Fulltekst i vitenarkiv Vis sammendrag

  We use a first-passage time approach to study the statistics of the trapping times induced by persistent motion of active particles colliding with flat boundaries. The angular first-passage time distribution and mean first-passage time are calculated exactly for active Brownian and run-and-tumble particles, and the results of the two prototypes of active particles are contrasted. Theoretical predictions are in excellent agreement with Langevin simulations of active particle dynamics. Our results shed further light on how active particles with different dynamics may have equivalent statistical properties in the bulk yet behave differently near boundaries or obstacles.

• Linga, Gaute; Angheluta, Luiza & Mathiesen, Joachim (2022). Onset of turbulence in channel flows with scale-invariant roughness. Physical Review Research (PRResearch). 4(3). doi: 10.1103/PhysRevResearch.4.033086. Fulltekst i vitenarkiv Vis sammendrag

  Using 3D direct numerical simulations of the Navier–Stokes equations, we study the effect of a self-affine wall roughness on the onset of turbulence in channel flow. We quantify the dependence of the turbulent intensity (proportional to the mean-squared velocity fluctuations) on the Reynolds number Re for different roughness amplitudes A. We find that for sufficiently high amplitudes, A>Ab, the transition changes its nature from being subcritical (as is known at A=0) to supercritical, i.e., the boundary roughness renders the flow unstable for Re>Rel, where the critical Rel decays nontrivially with increasing A. The dependence of the friction factor on Re is found to follow a generalized Forchheimer law, which interpolates between the laminar and inertial asymptotes. The transition between these two asymptotes occurs at a second critical Rec which is comparable in magnitude to Rel. This implies that transitional flow is an integral part of flow in open fractures when Re is sufficiently high, and should be accounted for in effective modeling approaches.

• Skogvoll, Vidar; Angheluta, Luiza; Skaugen, Audun; Salvalaglio, Marco & Viñals, Jorge (2022). A phase field crystal theory of the kinematics of dislocation lines. Journal of the Mechanics and Physics of Solids. ISSN 0022-5096. 166, s. 1–19. doi: 10.1016/j.jmps.2022.104932. Fulltekst i vitenarkiv Vis sammendrag

  We introduce a dislocation density tensor and derive its kinematic evolution law from a phase field description of crystal deformations in three dimensions. The phase field crystal (PFC) model is used to define the lattice distortion, including topological singularities, and the associated configurational stresses. We derive an exact expression for the velocity of dislocation line determined by the phase field evolution, and show that dislocation motion in the PFC is driven by a Peach–Koehler force. As is well known from earlier PFC model studies, the configurational stress is not divergence free for a general field configuration. Therefore, we also present a method (PFCMEq) to constrain the diffusive dynamics to mechanical equilibrium by adding an independent and integrable distortion so that the total resulting stress is divergence free. In the PFCMEq model, the far-field stress agrees very well with the predictions from continuum elasticity, while the near-field stress around the dislocation core is regularized by the smooth nature of the phase-field. We apply this framework to study the rate of shrinkage of an dislocation loop seeded in its glide plane.

• Pokawanvit, Supavit; Chen, Zhitao; You, Zhihong; Angheluta, Luiza; Marchetti, M. Cristina & Bowick, Mark J. (2022). Active nematic defects in compressible and incompressible flows. Physical Review E (PRE). ISSN 2470-0045. 106(5). doi: 10.1103/PhysRevE.106.054610. Fulltekst i vitenarkiv Vis sammendrag

  We study the dynamics of active nematic films on a substrate driven by active flows with or without the incompressible constraint. Through simulations and theoretical analysis, we show that arch patterns are stable in the compressible case, while they become unstable under the incompressibility constraint. For compressible flows at high enough activity, stable arches organize themselves into a smecticlike pattern, which induce an associated global polar ordering of +1/2 nematic defects. By contrast, divergence-free flows give rise to a local nematic order of the +1/2 defects, consisting of antialigned pairs of neighboring defects, as established in previous studies.

• Olsen, Kristian Stølevik; Angheluta, Luiza & Flekkøy, Eirik Grude (2022). Collective states of active matter with stochastic reversals: Emergent chiral states and spontaneous current switching. Physical Review Research (PRResearch). 4(4). doi: 10.1103/PhysRevResearch.4.043017. Fulltekst i vitenarkiv
• Rønning, Jonas; Marchetti, Cristina M.; Bowick, Mark J. & Angheluta, Luiza (2022). Flow around topological defects in active nematic films. Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. ISSN 1364-5021. 478(2257). doi: 10.1098/rspa.2021.0879. Fulltekst i vitenarkiv Vis sammendrag

  We study the active flow around isolated defects and the self-propulsion velocity of +1/2 defects in an active nematic film with both viscous dissipation (with viscosity η) and frictional damping Γ with a substrate. The interplay between these two dissipation mechanisms is controlled by the hydrodynamic dissipation length ℓd=η/Γ−−−√ that screens the flows. For an isolated defect, in the absence of screening from other defects, the size of the shear vorticity around the defect is controlled by the system size R. In the presence of friction that leads to a finite value of ℓd, the vorticity field decays to zero on the lengthscales larger than ℓd. We show that the self-propulsion velocity of +1/2 defects grows with R in small systems where R<ℓd, while in the infinite system limit or when R≫ℓd, it approaches a constant value determined by ℓd.

• Acharya, Amit; Angheluta, Luiza & Viñals, Jorge (2022). Elasticity versus phase field driven motion in the phase field crystal model. Modelling and Simulation in Materials Science and Engineering. ISSN 0965-0393. 30(6). doi: 10.1088/1361-651X/ac860b. Fulltekst i vitenarkiv
• Skogvoll, Vidar; Skaugen, Audun; Angheluta, Luiza & Viñals, Jorge (2021). Dislocation nucleation in the phase-field crystal model. Physical review B (PRB). ISSN 2469-9950. 103(1), s. 014107-1–014107-8. doi: 10.1103/PhysRevB.103.014107. Fulltekst i vitenarkiv Vis sammendrag

  We use the phase-field crystal model to study nucleation of edge dislocations in two dimensions under an applied stress field. A dislocation dipole nucleates under the applied stress, consistent with Burgers vector conservation. The phase field correctly accounts for elastic energy storage prior to nucleation and for dissipative relaxation during the nucleation event. We show that a lattice incompatibility field is a sensitive diagnostic of the location of the nucleation event and of the Burgers vector and slip direction of the dislocations that will be nucleated above threshold. A direct calculation of the phase-field energy accurately correlates with the nucleation event, as signaled by the lattice incompatibility field. We show that a Schmid-like criterion concerning the resolved stress at the nucleation site correctly predicts the critical nucleation stress. Finally, we present preliminary results for a three-dimensional, bcc lattice. The phase field allows direct computation of the lattice incompatibility tensor for both dislocation lines and loops.

• Angheluta, Luiza; Chen, Zhitao; Marchetti, Cristina & Bowick, Mark (2021). The role of fluid flow in the dynamics of active nematic defects. New Journal of Physics. 23. doi: 10.1088/1367-2630/abe8a8. Fulltekst i vitenarkiv Vis sammendrag

  Abstract We adapt the Halperin–Mazenko formalism to analyze two-dimensional active nematics coupled to a generic fluid flow. The governing hydrodynamic equations lead to evolution laws for nematic topological defects and their corresponding density fields. We find that ±1/2 defects are propelled by the local fluid flow and by the nematic orientation coupled with the flow shear rate. In the overdamped and compressible limit, we recover the previously obtained active self-propulsion of the +1/2 defects. Non-local hydrodynamic effects are primarily significant for incompressible flows, for which it is not possible to eliminate the fluid velocity in favor of the local defect polarization alone. For the case of two defects with opposite charge, the non-local hydrodynamic interaction is mediated by non-reciprocal pressure-gradient forces. Finally, we derive continuum equations for a defect gas coupled to an arbitrary (compressible or incompressible) fluid flow.

• Olsen, Kristian Stølevik; Angheluta, Luiza & Flekkøy, Eirik Grude (2021). Active Brownian particles moving through disordered landscapes. Soft Matter. ISSN 1744-683X. doi: 10.1039/d0sm01942a. Fulltekst i vitenarkiv
• Birnir, Björn; Angheluta, Luiza; Kaminsky, John & Chen, Xi (2021). Spectral link of the generalized Townsend-Perry constants in turbulent boundary layers. Physical Review Research (PRResearch). 3(4). doi: 10.1103/PhysRevResearch.3.043054. Fulltekst i vitenarkiv Vis sammendrag

  We propose a first minimal theory for boundary layer turbulence that captures very well the profile of the mean-square velocity fluctuations in the streamwise direction and give a quantitative prediction of the Townsend-Perry constants. Our theory is based on connecting all moments of velocity fluctuations as a function of the distance to the wall with the turbulent energy spectrum. A similar spectral theory was proposed in G. Gioia and P. Chakraborty [Phys. Rev. Lett. 96, 044502 (2006)] to explain the friction factor and the von Kármán law in G. Gioia, N. Guttenberg, N. Goldenfeld, and P. Chakraborty [Phys. Rev. Lett. 105, 184501 (2010)]. We generalized it by including fluctuations in the wall-shear stress and the streamwise velocity. The theoretical predictions for the mean velocity and mean-square fluctuations reproduce the shape of the velocity profiles in the buffer and inertial layer obtained from wind tunnel experiments.

• Skogvoll, Vidar; Skaugen, Audun & Angheluta, Luiza (2021). Stress in ordered systems: Ginzburg-Landau-type density field theory. Physical review B (PRB). ISSN 2469-9950. 103(22). doi: 10.1103/PhysRevB.103.224107. Fulltekst i vitenarkiv Vis sammendrag

  We present a theoretical method for deriving the stress tensor and elastic response of ordered systems within a Ginzburg-Landau-type density field theory in the linear regime. This is based on spatially coarse graining the microscopic stress which is determined by the variation of a free energy with respect to mass displacements. We find simple expressions for the stress tensor for phase field crystal models for different crystal symmetries in two and three dimensions. Using tetradic product sums of reciprocal lattice vectors, we calculate elastic constants and show that they are directly related to the symmetries of the reciprocal lattices. We also show that except for bcc lattices there are regions of model parameters for which the elastic response is isotropic. The predicted elastic stress-strain curves are verified by numerical strain-controlled bulk and shear deformations. Since the method is independent of a reference state, it extends also to defected crystals. We exemplify this by considering an edge and screw dislocation in the simple cubic lattice.

• Olsen, Kristian Stølevik; Angheluta, Luiza & Flekkøy, Eirik Grude (2020). Escape problem for active particles confined to a disk. Physical Review Research (PRResearch). 2(4). doi: 10.1103/PhysRevResearch.2.043314. Fulltekst i vitenarkiv Vis sammendrag

  We study the escape problem for interacting, self-propelled particles confined to a disk, where particles can exit through one open slot on the circumference. Within a minimal two-dimensional Vicsek model, we numerically study the statistics of escape events when the self-propelled particles can be in a flocking state. We show that while an exponential survival probability is characteristic for noninteracting self-propelled particles at all times, the interacting particles have an initial exponential phase crossing over to a subexponential late-time behavior. We use a phenomenological model based on nonstationary Poisson processes which includes the Allee effect to explain this subexponential trend and perform numerical simulations for various noise intensities.

• Rønning, Jonas; Skaugen, Audun; Hernández-García, Emilio; López, Cristóbal & Angheluta, Luiza (2020). Classical analogies for the force acting on an impurity in a Bose-Einstein condensate. New Journal of Physics. 22. doi: 10.1088/1367-2630/ab95de. Fulltekst i vitenarkiv Vis sammendrag

  We study the hydrodynamic forces acting on a small impurity moving in a two-dimensional Bose–Einstein condensate at non-zero temperature. The condensate is modelled by the damped-Gross Pitaevskii (dGPE) equation and the impurity by a Gaussian repulsive potential coupled to the condensate. For weak coupling, we obtain analytical expressions for the forces acting on the impurity, and compare them with those computed through direct numerical simulations of the dGPE and with the corresponding expressions for classical forces. For non-steady flows, there is a time-dependent force dominated by inertial effects and which has a correspondence in the Maxey–Riley theory for particles in classical fluids. In the steady-state regime, the force is dominated by a self-induced drag. Unlike at zero temperature, where the drag force vanishes below a critical velocity, at low temperatures the impurity experiences a net drag even at small velocities, as a consequence of the energy dissipation through interactions of the condensate with the thermal cloud. This dissipative force due to thermal drag is similar to the classical Stokes' drag. There is still a critical velocity above which steady-state drag is dominated by acoustic excitations and behaves non-monotonically with impurity's speed.

• Vollestad, Petter; Angheluta, Luiza & Jensen, Atle (2020). Experimental study of secondary flows above rough and flat interfaces in horizontal gas-liquid pipe flow. International Journal of Multiphase Flow. ISSN 0301-9322. 125. doi: 10.1016/j.ijmultiphaseflow.2020.103235. Fulltekst i vitenarkiv
• Salvalaglio, Marco; Angheluta, Luiza; Huang, Zhi-Feng; Voigt, Alex; Elder, Ken & Vinals, Jorge (2020). A coarse-grained phase-field crystal model of plastic motion. Journal of the Mechanics and Physics of Solids. ISSN 0022-5096. 137. doi: 10.1016/j.jmps.2019.103856. Fulltekst i vitenarkiv Vis sammendrag

  The phase-field crystal model in an amplitude equation approximation is shown to provide an accurate description of the deformation field in defected crystalline structures, as well as of dislocation motion. We analyze in detail stress regularization at a dislocation core given by the model, and show how the Burgers vector density can be directly computed from the topological singularities of the phase-field amplitudes. Distortions arising from these amplitudes are then supplemented with non-singular displacements to enforce mechanical equilibrium. This allows for a consistent separation of plastic and elastic time scales in this framework. A finite element method is introduced to solve the combined amplitude and elasticity equations, which is applied to a few prototypical configurations in two spatial dimensions for a crystal of triangular lattice symmetry: i) the stress field induced by an edge dislocation with an analysis of how the amplitude equation regularizes stresses near the dislocation core, ii) the motion of a dislocation dipole as a result of its internal interaction, and iii) the shrinkage of a rotated grain. We compare our results with those given by other extensions of classical elasticity theory, such as strain-gradient elasticity and methods based on the smoothing of Burgers vector densities near defect cores.

• Olsen, Kristian Stølevik; Flekkøy, Eirik Grude; Angheluta, Luiza; Campbell, James; Måløy, Knut Jørgen & Sandnes, Bjørnar (2019). Geometric universality and anomalous diffusion in frictional fingers. New Journal of Physics. 21(6). doi: 10.1088/1367-2630/ab25bf. Fulltekst i vitenarkiv Vis sammendrag

  Frictional finger trees are patterns emerging from non-equilibrium processes in particle-fluid systems. Their formation share several properties with growth algorithms for minimum spanning trees(MSTs) in random energy landscapes. We propose that the frictional finger trees are indeed in the same geometric universality class as the MSTs, which is checked using updated numerical simulation algorithms for frictional fingers. We also propose a theoretical model for anomalous diffusion in these patterns, and discuss the role of diffusion as a tool to classify geometry.

• Vollestad, Petter; Ayati, Anis Awal; Angheluta, Luiza; Lacasce, Joseph Henry & Jensen, Atle (2019). Experimental investigation of airflow above waves in a horizontal pipe. International Journal of Multiphase Flow. ISSN 0301-9322. 110, s. 37–49. doi: 10.1016/j.ijmultiphaseflow.2018.08.008. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the effect of waves on the airflow in horizontal two-phase pipe flow. Velocity fields in the gaseous phase were acquired by particle image velocimetry (PIV), while interfacial elevation was measured with conductance wave probes. The velocity fields were sampled on a wave-following coordinate system which allows for a decomposition of the velocity field into a mean, wave-coherent and fluctuating component by means of a three-component Reynolds decomposition. Additionally, coherent vortical structures were identified by the swirling strength criterion, and their distribution along the waves is investigated. Results suggest that the interaction between turbulent airflow and propagating waves in a pipe has a number of features reminiscent of wind-wave interaction in open systems. Above waves generated by sufficiently high gas flow rates, there is a distinct region of sheltered airflow, and a lifting of the critical layer on the leeward side of the crest. Streamlines of the phase-averaged flow field show a cat’s eye structure located close to the crest in this region. Above waves of moderate steepness, we observe a shear layer that remains adjacent to the wave surface. Above steeper waves and higher gas flow rate, this layer detaches from the surface just downstream of the crest. Shear layer separation above waves is traditionally linked to the onset of wave breaking, and it is interesting to note that the case where we observe a separated shear layer in the phase-averaged vorticity field is in a regime of amplitude saturation. The swirling strength criterion reveals that vortical structures are shed from the interface and populate the detached shear layer above the trough. Below the detached shear layer, there is a region populated by counter-rotating vortices. The critical height coincides with the border between these two regions.

• Skaugen, Audun; Angheluta, Luiza & Vinals, Jorge (2018). Separation of Elastic and Plastic Timescales in a Phase Field Crystal Model. Physical Review Letters. ISSN 0031-9007. 121(25), s. 255501-01–255501-05. doi: 10.1103/PhysRevLett.121.255501. Fulltekst i vitenarkiv Vis sammendrag

  A consistent small-scale description of plasticity and dislocation motion in a crystalline solid is presented based on the phase field crystal description. By allowing for independent mass motion and lattice distortion, the crystal can maintain elastic equilibrium on the timescale of plastic motion. We show that the singular (incompatible) strains are determined by the phase field crystal density, while the smooth distortions are constrained to satisfy elastic equilibrium. A numerical implementation of the model is presented and used to study a benchmark problem: the motion of an edge dislocation dipole in a triangular lattice. The time dependence of the dipole separation agrees with continuum elasticity with no adjustable parameters.

• Aupart, Claire Olga Maryse; Dunkel, Kristina G; Angheluta, Luiza; Austrheim, Håkon Olaf; Ildefonse, Beniot & Malthe-Sørenssen, Anders [Vis alle 7 forfattere av denne artikkelen] (2018). Olivine Grain Size Distributions in Faults and Shear Zones: Evidence for Nonsteady State Deformation. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 123(9), s. 7421–7443. doi: 10.1029/2018JB015836. Fulltekst i vitenarkiv Vis sammendrag

  The grain size distribution of deformed rocks may provide valuable information about their deformation history and the associated mechanisms. Here we present a unique set of olivine grain size distributions from ultramafic rocks deformed under a wide range of stress and strain rate conditions. Both experimentally deformed and naturally deformed samples are included. We observe a surprisingly uniform behavior, and most samples show power law grain size distributions. Convincing lognormal distributions across all scales were only observed for samples experimentally deformed at high temperature (1200 °C) and for some mantle‐deformed natural samples. Single power law distributions were observed for natural samples deformed by brittle mechanisms and by samples deformed experimentally in the regime of low‐temperature plasticity. Most natural samples show a crossover in power law scaling behavior near the median grain size from a steep slope for the larger grain fraction to a more gentle slope for the smaller grains. The small grain fraction shows a good data collapse when normalized to the crossover length scale. The associated power law slope indicates a common grain size controlling process. We propose a model that explains how such a scaling behavior may arise in the dislocation creep regime from the competition between the rate involved in the dislocation dynamics and the imposed strain rate. The common departure from lognormal distributions suggests that naturally deformed samples often have a deformation history that is far from a steady state scenario and probably reflects deformation under highly variable stress and strain rates. ©2018. American Geophysical Union. All Rights Reserved.

• Skaugen, Audun; Angheluta, Luiza & Vinals, Jorge (2018). Dislocation dynamics and crystal plasticity in the phase-field crystal model. Physical review B (PRB). ISSN 2469-9950. 97(5). doi: 10.1103/PhysRevB.97.054113. Fulltekst i vitenarkiv Vis sammendrag

  A phase-field model of a crystalline material is introduced to develop the necessary theoretical framework to study plastic flow due to dislocation motion. We first obtain the elastic stress from the phase-field crystal free energy under weak distortion and show that it obeys the stress-strain relation of linear elasticity. We focus next on dislocations in a two-dimensional hexagonal lattice. They are composite topological defects in the weakly nonlinear amplitude equation expansion of the phase field, with topological charges given by the standard Burgers vector. This allows us to introduce a formal relation between the dislocation velocity and the evolution of the slowly varying amplitudes of the phase field. Standard dissipative dynamics of the phase-field crystal model is shown to determine the velocity of the dislocations. When the amplitude expansion is valid and under additional simplifications, we find that the dislocation velocity is determined by the Peach-Koehler force. As an application, we compute the defect velocity for a dislocation dipole in two setups, pure glide and pure climb, and compare it with the analytical predictions. © 2018 American Physical Society

• Santucci, Stephane; Tallakstad, Ken Tore; Angheluta, Luiza; Laurson, Lasse; Toussaint, Renaud & Måløy, Knut Jørgen (2018). Avalanches and extreme value statistics in interfacial crackling dynamics. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 377(2136), s. 1–15. doi: 10.1098/rsta.2017.0394. Fulltekst i vitenarkiv
• Dumazer, Guillaume Henri; Flekkøy, Eirik Grude; Renard, Francois & Angheluta, Luiza (2017). Transient anomalous diffusion regimes in reversible adsorbing systems. Physical Review E (PRE). ISSN 2470-0045. 96(4). doi: 10.1103/PhysRevE.96.042106. Fulltekst i vitenarkiv
• Skaugen, Audun & Angheluta, Luiza (2017). Origin of the inverse energy cascade in two-dimensional quantum turbulence. Physical Review E (PRE). ISSN 2470-0045. 95(5). doi: 10.1103/PhysRevE.95.052144. Fulltekst i vitenarkiv Vis sammendrag

  We establish a statistical relationship between the inverse energy cascade and the spatial correlations of clustered vortices in two-dimensional quantum turbulence. The Kolmogorov spectrum k− 5 / 3 on inertial scales r corresponds to a pair correlation function between the vortices with different signs that decays as a power law with the pair distance given as r− 4 / 3 . To test these scaling relations, we propose a forced and dissipative point vortex model that captures the turbulent dynamics of quantized vortices by the emergent clustering of same-sign vortices. The inverse energy cascade developing in a statistically neutral system originates from this vortex clustering that evolves with time.

• Skaugen, Audun & Angheluta, Luiza (2016). Vortex clustering and universal scaling laws in two-dimensional quantum turbulence. Physical Review E (PRE). ISSN 2470-0045. 93(3). doi: 10.1103/PhysRevE.93.032106. Fulltekst i vitenarkiv
• Hawkins, Christopher; Angheluta, Luiza; Krotkiewski, Marcin & Jamtveit, Bjørn (2016). Reynolds-number dependence of the longitudinal dispersion in turbulent pipe flow. Physical Review E (PRE). ISSN 2470-0045. 93(4). doi: 10.1103/PhysRevE.93.043119. Fulltekst i vitenarkiv
• Skaugen, Audun & Angheluta, Luiza (2016). Velocity statistics for nonuniform configurations of point vortices. Physical Review E (PRE). ISSN 2470-0045. 93(4). doi: 10.1103/PhysRevE.93.042137. Fulltekst i vitenarkiv
• Tarp, Jens M.; Angheluta, Luiza; Mathiesen, Joachim & Goldenfeld, Nigel (2014). Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model. Physical Review Letters. ISSN 0031-9007. 113(26). doi: 10.1103/PhysRevLett.113.265503. Fulltekst i vitenarkiv
• Mathiesen, Joachim; Angheluta, Luiza & Jensen, M. H. (2014). Statistics of co-occurring keywords in confined text messages on Twitter. The European Physical Journal Special Topics (EPJ - Special Topics (EPJ ST)). ISSN 1951-6355. 223(9), s. 1849–1858. doi: 10.1140/epjst/e2014-02230-y. Fulltekst i vitenarkiv
• Jamtveit, Bjørn; Krotkiewski, Marcin; Kobchenko, Maya; Renard, Francois Marie Paul L & Angheluta, Luiza (2014). Pore-space distribution and transport properties of an andesitic intrusion. Earth and Planetary Science Letters. ISSN 0012-821X. 400, s. 123–129. doi: 10.1016/j.epsl.2014.05.042. Fulltekst i vitenarkiv
• Hawkins, Christopher; Angheluta, Luiza & Jamtveit, Bjørn (2014). Hydrodynamic shadowing effect during precipitation of dendrites in channel flow. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 89(2). doi: 10.1103/PhysRevE.89.022402. Fulltekst i vitenarkiv Vis sammendrag

  A supersaturated fluid flowing over a reactive, rough surface leads to complex precipitation patterns. We study the growth and interaction between discrete precipitates along a reactive wall in a nonlaminar channel flow. We show that the competition between advective transport, diffusion, and mixing strongly influences the downstream precipitates morphology and the typical correlation length between different precipitates. © 2014 American Physical Society

• LeBlanc, Michael; Angheluta, Luiza; Dahmen, Karin & Goldenfeld, Nigel (2013). Universal fluctuations and extreme statistics of avalanches near the depinning transition. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 87(2). doi: 10.1103/PhysRevE.87.022126. Fulltekst i vitenarkiv
• Hawkins, Christopher; Angheluta, Luiza; Hammer, Øyvind & Jamtveit, Bjørn (2013). Precipitation dendrites in channel flow. Europhysics letters. ISSN 0295-5075. 102(5). doi: 10.1209/0295-5075/102/54001. Fulltekst i vitenarkiv
• Mathiesen, Joachim; Angheluta, Luiza; Ahlgren, Peter T.H. & Jensen, Mogens H. (2013). Excitable human dynamics driven by extrinsic events in massive communities. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 110(43), s. 17259–17262. doi: 10.1073/pnas.1304179110. Fulltekst i vitenarkiv
• Bjerre, Mathias; Tarp, Jens; Angheluta, Luiza & Mathiesen, Joachim (2013). Rotation-induced grain growth and stagnation in phase-field crystal models. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 88(2). doi: 10.1103/PhysRevE.88.020401. Fulltekst i vitenarkiv
• Jafarpour, Farshid; Angheluta, Luiza & Goldenfeld, Nigel (2013). Velocity statistics for interacting edge dislocations in one dimension from Dyson's Coulomb gas model. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 88(4). doi: 10.1103/PhysRevE.88.042123. Fulltekst i vitenarkiv
• Assaf, Michael; Angheluta, Luiza & Goldenfeld, Nigel (2012). Effect of Weak Rotation on Large-Scale Circulation Cessations in Turbulent Convection. Physical Review Letters. ISSN 0031-9007. 109(7). doi: 10.1103/PhysRevLett.109.074502. Fulltekst i vitenarkiv
• LeBlanc, Michael; Angheluta, Luiza; Dahmen, Karin & Goldenfeld, Nigel (2012). Distribution of Maximum Velocities in Avalanches Near the Depinning Transition. Physical Review Letters. ISSN 0031-9007. 109(10). doi: 10.1103/PhysRevLett.109.105702. Fulltekst i vitenarkiv
• Angheluta, Luiza; Mathiesen, Joachim & Aharonov, Einat (2012). Compaction of porous rock by dissolution on discrete stylolites: A one-dimensional model. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 117. doi: 10.1029/2012JB009245. Fulltekst i vitenarkiv
• Angheluta, Luiza; Jeraldo, Patricio & Goldenfeld, Nigel (2012). Anisotropic velocity statistics of topological defects under shear flow. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 85(1). doi: 10.1103/PhysRevE.85.011153. Fulltekst i vitenarkiv
• Assaf, Michael; Angheluta, Luiza & Goldenfeld, Nigel (2011). Rare Fluctuations and Large-Scale Circulation Cessations in Turbulent Convection. Physical Review Letters. ISSN 0031-9007. 107(4). doi: 10.1103/PhysRevLett.107.044502. Fulltekst i vitenarkiv
• Angheluta, Luiza; Candela, Thibault; Mathiesen, Joachim & Renard, Francois Marie Paul L (2011). Effect of Surface Morphology on the Dissipation During Shear and Slip Along a Rock-Rock Interface that Contains a Visco-elastic Core. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. 168(12), s. 2335–2344. doi: 10.1007/s00024-011-0272-8. Fulltekst i vitenarkiv
• Angheluta, Luiza; Mathiesen, Joachim; Misbah, C & Renard, Francois Marie Paul L (2010). Morphological instabilities of stressed and reactive geological interfaces. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 115. doi: 10.1029/2009JB006880. Fulltekst i vitenarkiv
• Angheluta, Luiza; Jettestuen, Espen & Mathiesen, Joachim (2009). Thermodynamics and roughening of solid-solid interfaces. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 79(3). doi: 10.1103/PhysRevE.79.031601. Fulltekst i vitenarkiv
• Angheluta, Luiza & Mathiesen, Joachim (2009). Thermodynamics of stressed solids: Slow deformation and roughening of material interfaces. The European Physical Journal Special Topics (EPJ - Special Topics (EPJ ST)). ISSN 1951-6355. 178(1), s. 123–132. doi: 10.1140/epjst/e2010-01185-3. Fulltekst i vitenarkiv
• Angheluta, Luiza; Jettestuen, Espen; Mathiesen, Joachim; Renard, Francois Marie Paul L & Jamtveit, Bjørn (2008). Stress-driven phase transformation and the roughening of solid-solid interfaces. Physical Review Letters. ISSN 0031-9007. 1. doi: 10.1103/PhysRevLett.100.096105. Fulltekst i vitenarkiv
• Angheluta, Luiza; Jettestuen, Espen; Mathiesen, Joachim; Renard, Francois & Jamtveit, Bjørn (2008). Stress driven stress transformation and the roughening of solid-solid interfaces. Physical Review Letters. ISSN 0031-9007. 100. Fulltekst i vitenarkiv
• Jensen, Mogens H.; Sneppen, Kim & Angheluta, Luiza (2008). Kolmogorov scaling from random fields. Europhysics letters. ISSN 0295-5075. 97(1). Fulltekst i vitenarkiv
• Angheluta, Luiza; Benzi, Roberto; Biferale, Luca; Procaccia, Itamar & Toschi, Frederico (2006). On the anomalous scaling exponents in nonlinear models of turbulence. Physical Review Letters. ISSN 0031-9007. 97(160601). Fulltekst i vitenarkiv

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• Angheluta, Luiza (2025). Analytical methods in physics. Springer. ISBN 9783031770524. 227 s. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2024). Active Reorganisation in Tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2024). Active Reorganisation in Tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Active Reorganisation in Tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Active Reorganisation in Tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Energy profiles and statistics of spontaneous T1 transitions in confluent tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Robust statistical properties of T1 transitions in confluent tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Active Reorganisation in Tissues. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2023). Active Reorganisation in Tissues: Phase Transition of Ideas from Physics to Biology. Fulltekst i vitenarkiv
• Vogt, Yngve; Krauss, Stefan Johannes Karl; Mossige, Joachim; Dysthe, Dag Kristian; Angheluta, Luiza & Jensenius, Alexander Refsum (2023). Bereder grunnen for kunstige organer. [Journal]. Apollon. Fulltekst i vitenarkiv
• Jain, Harish Pruthviraj; Angheluta, Luiza & Voigt, Axel (2022). Phasefield Model of Active Interacting Cells that Grow and Divide. Fulltekst i vitenarkiv Vis sammendrag

  Contact inhibition limits migration and proliferation of cells in cell colonies. We consider a multiphase field model to investigate the growth dynamics of a cell colony, composed of proliferating cells. The model takes into account the mechanism of contact inhibition of proliferation by local mechanical interactions. We compare nonmigrating and migrating cells, in order to provide a quantitative characterization of the dynamics and analyze the velocity of the colony boundary for both cases. Additionally, we measure single cell velocities, number of neighbor distributions, as well as the influence of stress and age on positions of the cells and with respect to each other.

• Angheluta, Luiza & Rønning, Jonas (2022). Dynamics of topological defects in active nematic films. Fulltekst i vitenarkiv
• Angheluta, Luiza (2021). How fluid flows influence defect dynamics in active nematic films. Fulltekst i vitenarkiv
• Angheluta, Luiza (2021). Dynamics of topological defects in active nematic films. Fulltekst i vitenarkiv
• Aupart, Claire Olga Maryse; Dunkel, Kristina Grete; Angheluta-Bauer, Luiza; Austrheim, Håkon; Ildefonse, Benoit & Malthe-Sørenssen, Anders [Vis alle 7 forfattere av denne artikkelen] (2017). Grain size distribution evolution in shear zones: a study case in the Leka Ophiolite Complex (LOC). Fulltekst i vitenarkiv
• Myhra, Kristin Sæterdal & Angheluta, Luiza (2011). How do crystals melt: the role of dislocations and grain boundaries. Fulltekst i vitenarkiv
• Angheluta, Luiza & Mathiesen, Joachim (2007). Energy consideration of elastic interfaces: some insights on stylolites. Fulltekst i vitenarkiv
• Angheluta, Luiza; Jettestuen, Espen; Mathiesen, Joachim; Renard, Francois Marie Paul L & Jamtveit, Bjørn (2007). Solid-solid phase transformation: roughening of stylolites. Fulltekst i vitenarkiv
• Angheluta, Luiza (2007). Physical mechanisms in the formation and dynamics of stylolitic surfaces. Fulltekst i vitenarkiv
• Myhra, Kristin Sæterdal & Angheluta, Luiza (2011). A Phase Field Crystal Study of Freezing and Melting. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Though melting is a common phase transition in nature, the small scale details of the crystal breakdown in two dimensions are not yet fully understood. We present a numerical investigation of melting and freezing in two dimensions through the phase field crystal model. We start out by discussing phase transitions by means of disorder-order transitions through the phase field method. The method is suitable of describing phase transitions in heterogeneous and isotropic systems and is an important tool for modeling micro structural evolution. We continue by deriving the phase field crystal method. That is a method in which the isotropic approximation is relaxed and the free energy functional is constructed to ensure a periodic structure in the equilibrium state. By this approach, important features such as crystal orientation, defects and deformations are naturally incorporated in the model. Hence, this method provides a suitable method for describing the process of crystal growth as well as the breakdown of the crystalline structure, that is the processes of freezing and melting respectively. Additionally, a set of amplitude equations are presented for the study of the dynamical evolution in the crystalline phase. Thereafter, we discuss the process of melting and the role of dimensionality and dislocations in the phase transition. We limit our work to two dimensional systems and investigate the evolution of melting numerically with a particular focus on the role of defects in the phase transition. The simulated melting is induced by two different protocols, that is uniform heating and applied shear stress, and we evaluate our numerical results relative to the theory of dislocation mediated melting. As a closure we summarize our results, elaborate upon the challenges in the search for the melting mechanism and propose ideas for future work which can be carried through with the phase field crystal method.

• Angheluta, Luiza (2009). Instabilities in Reactive and Deformable Two Phase Media. Universitetet i Oslo. Fulltekst i vitenarkiv

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