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Physics Physics

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Monday 15 December

Atomic Physics · Cross-listed from astro-ph.SR

High Resolution Overtone Spectroscopy of HNC$^+$ and HCN$^+$

Miguel Jiménez-Redondo, Chiara Schleif, Julianna Palotás et al. (+5 more)

Rotationally resolved spectra of the HNC$^+$ and HCN$^+$ molecular ions have been recorded in the spectral range between 6200 and 6800 \rcm\ using a cryogenic ion trap instrument. The rovibrational transitions were probed using two different action spectroscopy schemes, namely laser-induced reaction (LIR) and leak-out spectroscopy (LOS). Various vibrational bands of HNC$^+$ and HCN$^+$ were measured with high resolution for the first time. For HNC$^+$, the $\text{X}~^2\Sigma^+~(20^00)-(00^00)$ overtone band was recorded using LIR, while LOS was used to probe the $\text{X}~^2\Pi~(000)^1-(210)^0\mu$ combination band and the $\text{X}~^2\Pi~(000)^1-\text{A}~^2\Sigma^+~(10^00)$ vibronic band of HCN$^+$. Spectroscopic constants, band origins and radiative lifetimes for the observed states have been determined. The effective fit for the HCN$^+$ spectra revealed the presence of strong vibrational couplings leading to perturbations of the rovibrational levels of the excited states. The two action spectroscopy schemes are compared and their potential use to explore ion-molecule interactions is discussed.
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All authors Miguel Jiménez-Redondo, Chiara Schleif, Julianna Palotás, János Sarka, Hayley Bunn, Petr Dohnal, Paola Caselli, Pavol Jusko

History and Philosophy of Physics

Einstein Was Not a Flat Physicalist: Principle Theories, Constructive Theories, and the Direction of Constraint

Galina Weinstein

Einstein's distinction between principle theories and constructive theories is methodological rather than metaphysical. Principle theories such as thermodynamics and relativity articulate empirically distilled constraints that delimit admissible microphysical models, while constructive theories remain provisional and revisable. This paper reconstructs Einstein's framework from primary sources and argues that recent appeals to it by Meir Hemmo and Orly Shenker (under the banner of "Flat Physicalism") invert its functional hierarchy. What is presented as an Einsteinian template instead supports a reductionist metaphysics foreign to Einstein's methodology and increasingly misaligned with the structural commitments of contemporary physics.
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Physics and Society

Climate change impacts on net load under technological uncertainty in European power systems

Luna Bloin-Wibe, Erich Fischer, Leonard Göke et al. (+3 more)

Renewable energy sources play a major role in future net-zero energy systems. However, achieving energy system resilience remains challenging, since renewables depend on weather fluctuations, and future energy systems are subject to major design uncertainty. Existing literature mostly treats these types of uncertainty separately. Therefore, the assessment of uncertainties surrounding climate change and energy system design, and particularly their interactions, is insufficiently understood. To close this gap, we evaluate net load to assess energy system stress without relying on perfect foresight, while maintaining temporal and spatial correlations of the climate system. Net load is calculated from hourly historical and future climate model data translated to energy variables. To scope the extent of plausible energy systems, we consider eight different design scenarios inspired by the European Ten-Year Network Development Plan (TYNDP) and different levels of transmission expansion. We find that climate change impacts on net load are highly sensitive to the energy system design, implying that energy systems can be designed so that they are either hindered or helped by climate change. Furthermore, within a system scenario, climate change can change the frequency and seasonality of high net load events and their technological and meteorological composition. Wind-dominated systems with currently electrified heating levels, for instance, feature a 30% increase of high net load events under climate change, mostly in summer and fall, while fully electrified net zero systems are impacted by high net load events in winter and spring, which decrease by 50% with climate change. Our work thus calls for a wider perspective on energy-climate stress that captures the non-linear interactions of climate change and system design uncertainty, thereby overcoming the current focus on cold Dunkelflauten.
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All authors Luna Bloin-Wibe, Erich Fischer, Leonard Göke, Reto Knutti, Francesco de Marco, Jan Wohland

Fluid Dynamics

On the conservation of physical properties in operator interpolation of parameterized hydrodynamic systems

Yuto Nakamura, Shintaro Sato and Naofumi Ohnishi

Reduced-order models (ROMs) that capture changes in fluid systems due to variations in parameters, such as the Reynolds number or the shape of a stationary body placed in the flow, are attracting increasing attention in engineering applications. In this study, we identify linear operators that characterize the behavior of fluid systems across a wide parameter range by using flow field datasets at several representative parameter values. We then comprehensively assess the applicability of ROMs constructed through the interpolation of these operators. Specifically, we consider two intrusive operator-based ROMs: one derived from Galerkin projection and the other based on operator inference using dynamic mode decomposition (DMD). The performance of these ROMs is evaluated for flows around circular and elliptical cylinders over a range of Reynolds numbers and aspect ratios. The Galerkin-based ROM successfully predicts only the eigenvalue and eigenmode corresponding to the fundamental frequency of the Kármán vortex shedding, while other frequencies are not captured and show a decaying behavior. In contrast, the DMD-based ROM accurately predicts both the fundamental frequency and its higher harmonics. Furthermore, visualization of the linear operator matrix elements reveals that interpolation fails when the subspace includes bases contaminated by numerical errors. However, by carefully selecting the subspace dimension and reference conditions, it is possible to accurately predict eigenvalues and corresponding modes even under conditions where multiple low-frequency modes exist outside the harmonic structure of the fundamental frequency. These findings underscore the robustness of the DMD-based parametric operator ROM approach.
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Chemical Physics

Phase Space Electronic Structure Theory: From Diatomic Lambda-Doubling to Macroscopic Einstein-de Haas

Linqing Peng, Tian Qiu, Nadine Bradbury et al. (+5 more)

$\Lambda$-doubling of diatomic molecules is a subtle microscopic phenomenon that has long attracted the attention of experimental groups, insofar as rotation of molecular $\textit{nuclei}$ induces small energetic changes in the (degenerate) $\textit{electronic}$ state. A direct description of such a phenomenon clearly requires going beyond the Born-Oppenheimer approximation. Here we show that a phase space theory previously developed to capture electronic momentum and model vibrational circular dichroism – and which we have postulated should also describe the Einstein-de Haas effect, a macroscopic manifestation of angular momentum conservation – is also able to recover the $\Lambda$-doubling energy splitting (or $\Lambda$-splitting) of the NO molecule nearly quantitatively. The key observation is that, by parameterizing the electronic Hamiltonian in terms of both nuclear position ($\mathbf{X}$) and nuclear momentum ($\mathbf{P}$), a phase space method yields potential energy surfaces that explicitly include the electron-rotation coupling and correctly conserve angular momentum (which we show is essential to capture $\Lambda-$doubling). The data presented in this manuscript offers another small glimpse into the rich physics that one can learn from investigating phase space potential energy surfaces $E_{PS}(\mathbf{X},\mathbf{P})$ as a function of both nuclear position and momentum, all at a computational cost comparable to standard Born-Oppenheimer electronic structure calculations.
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All authors Linqing Peng, Tian Qiu, Nadine Bradbury, Xuezhi Bian, Mansi Bhati, Robert Littlejohn, Nathanael M. Kidwell, Joseph E. Subotnik

Applied Physics

Lithographically Defined Si$_3$N$_4$ Torsional Pendulum

Thomas Bsaibes, Charles Condos, Jack Manley et al. (+3 more)

Torsion pendulums provide an opportunity to trap large masses in a potential weak enough to explore two-body gravitation. Cooled to, and then released from a ground state, weak quantum effects, including those from gravity, might reveal themselves in the evolving decoherence of a torsion pendulum, if its baseline dissipation were sufficiently dilute for quantum coherent oscillation. Monolithic ribbon-like, or multi-filar suspension geometries provide a key to such dilution in torsion, but are challenging to make. As a solution, we introduce a lithographically defined silicon nitride (Si$_3$N$_4$) ribbon suspension in a wafer-scale approach to pendulum fabrication that is conducive to such 2-D geometries, making extreme aspect ratios, and even multi-filar designs, a possibility. A monofilar, monolithic, centimeter scale torsion pendulum is fabricated and released in a first proof of concept. Mounted in vacuum, it is optically excited and cooled using measurement based feedback. Though only 37 mg, the device displays a fundamental frequency of 162 mHz and an undiluted Q of 12000, demonstrating a foundational step towards ultra-coherent, ultra-low frequency torsion pendulums.
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All authors Thomas Bsaibes, Charles Condos, Jack Manley, Jon Pratt, Dalziel J. Wilson, Jacob Taylor

Optics

Spatiotemporally decoupled super-oscillatory microscopy enables label-free reconstruction of human ciliary waveforms

Ning Xu, Sarah E. Bohndiek, Graham Spicer et al. (+5 more)

Imaging native motile cilia requires label-free contrast, sub-diffraction spatial discrimination, and millisecond temporal sampling. We introduce Super-Oscillatory Label-free Inertia-free Scanning (SOLIS) microscopy, in which a static multilevel diffractive optical element generates compressed super-oscillatory probes and a high-speed digital micromirror device addresses the probes without translated-stage motion. A complete 25-position scan produces one acquisition-window-averaged map every 3.58 ms, corresponding to 279 reconstructed fps. On nanofabricated line-pair targets, SOLIS retained measurable label-free contrast at a 253 nm period and resolved representative modulation at 270 nm. In differentiated primary human nasal epithelial cultures, SOLIS distinguished adjacent ciliary maxima separated by 346 nm, below the 431 nm Rayleigh reference, and acquired 14-16 reconstructed samples per observed beat cycle. Tip-centroid tracking recovered closed, asymmetric two-dimensional trajectories with a median cycle-to-cycle localisation precision of 63.5 nm across 20 cilia. In a proof-of-principle perturbation, Dynarrestin reduced culture-level ciliary beat frequency from 19.2 to 6.6 Hz and projected stroke amplitude from 4.8 to 2.3 um. By separating spatial compression from temporal addressing, SOLIS extends super-oscillatory microscopy to label-free, millisecond-scale analysis of human ciliary kinematics.
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All authors Ning Xu, Sarah E. Bohndiek, Graham Spicer, Mingjun Jiang, Qixia Wang, Baoping Xu, Qiaofeng Tan, Calum Williams

2512.13432 · 15 Dec · Substantially revised and expanded version. The manuscript has been reframed around label-free millisecond-scale reconstruction of human ciliary kinematics, with new optical metrology, dynamic validation, primary human ciliary experiments, population analysis, and pharmacological perturbation data. 36 pages,6 figures

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Applied Physics · Cross-listed from cond-mat.soft

Towards Animate Droplets: Active, Adaptive, and Autonomous

Joe Forth, Robert Malinowski and Giorgio Volpe

Droplets, sub-millilitre liquid volumes with at least one interface, have traditionally served as compartments for storing, transporting, and delivering materials. Beyond familiar applications in food, coatings, and consumer goods, they find cutting-edge use in energy storage, sensing, and tissue engineering. The next frontier is their integration into animate matter, emerging materials defined by their levels of activity, adaptiveness, and autonomy. Easy to produce and dispense or print into complex structures, and with enormous chemical versatility, droplets are ideal building blocks for animate matter. In this Perspective, we outline a roadmap for advancing animacy in droplets and call for a more concerted effort to integrate novel mechanisms for motility, sensing, and decision-making into droplet design. Although research on active droplets spans more than a century, achieving true autonomy, where droplets process multiple stimuli and respond without external control, remains a central challenge. We hope to inspire interdisciplinary collaboration towards applications in consumer goods, microfluidics, adaptive optics, tissue engineering, and soft robotics.
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Physics and Society · Cross-listed from eess.SP

From Nodes to Edges: Edge-Based Laplacians for Brain Signal Processing

Andrea Santoro, Marco Nurisso and Giovanni Petri

Traditional graph signal processing (GSP) methods applied to brain networks focus on signals defined on the nodes. Thus, they are unable to capture potentially important dynamics occurring on the edges. In this work, we adopt an edge-centric GSP approach to analyze edge signals constructed from 100 unrelated subjects of the Human Connectome Project. Specifically, we describe structural connectivity through the lens of the 1-dimensional Hodge Laplacian, processing signals defined on edges to capture co-fluctuation information between brain regions. We demonstrate that edge-based approaches achieve superior task decoding accuracy in static and dynamic scenarios compared to conventional node-based techniques, thereby unveiling unique aspects of brain functional organization. These findings underscore the promise of edge-focused GSP strategies for deepening our understanding of brain connectivity and functional dynamics.
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Computational Physics · Cross-listed from cond-mat.dis-nn

Large Deviation Properties of Minimum Spanning Trees for Random Graphs

Mahdi Sarikhani and Alexander K. Hartmann

We study the large-deviation properties of minimum spanning trees for two ensembles of random graphs with $N$ nodes. First, we consider complete graphs. Second, we study Erdős-Rényi (ER) random graphs with edge probability $p=c/N$ conditioned to be connected. By using large-deviation Markov chain sampling, we are able to obtain the distribution $P(W)$ of the spanning-tree weight $W$ down to probability densities as small as $10^{-300}$. For the complete graph, we confirm analytical predictions with respect to the expectation value. For both ensembles, the large deviation principle is fulfilled. For the connected ER graphs, we observe a remarkable change of the distributions at the value of $c=1$, which is the percolation threshold for the original ER ensemble.
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Fluid Dynamics · Cross-listed from astro-ph.HE

Three-dimensional numerical simulations of neutron star cores in the two-fluid MHD approximation: simple configurations

Andrei Igoshev, Nicolás A. Moraga, Andreas Reisenegger et al. (+2 more)

Magnetic field evolution in neutron star cores is not fully understood. We describe the field evolution both for one barotropic fluid as well as two collisionally coupled barotropic fluids with different density profiles using the anelastic approximation and the Navier-Stokes equations to simulate the evolution in three dimensions. In the one-fluid case, a single fluid describes the motion of the charged particles. In the two-fluid model, the neutral fluid is coupled to the electrically conductive fluid by collisions, the latter being dragged by the magnetic field. In this model, both fluids have distinct density profiles. This forces them to move at slightly different velocities, resulting in a relative motion between the two barotropic fluids – ambipolar diffusion. We develop a code based on Dedalus and study the evolution of simple poloidal dipolar and toroidal magnetic fields. Previous 2D studies found that poloidal magnetic fields evolve towards a stable Grad-Shafranov equilibrium. In our 3D simulations we find an instability of the two-fluid system similar to the one in the barotropic fluid system. After the instability saturates, a highly non-linear Lorentz force introduces small-scale fluid motion that leads to turbulence, development of a cascade and significant, non-axially symmetric changes in the magnetic field configuration. Fluid viscosity plays an essential role in regularizing the small-scale fluid motion, providing an energy drain.
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All authors Andrei Igoshev, Nicolás A. Moraga, Andreas Reisenegger, Calum S. Skene, Rainer Hollerbach

Physics and Society · Cross-listed from astro-ph.SR

Citizen CATE 2024: Extending Totality During the 8 April 2024 Total Solar Eclipse with a Distributed Network of Community Participants

Sarah A. Kovac, Amir Caspi, Daniel B. Seaton et al. (+240 more)

The Citizen CATE 2024 next-generation experiment placed 43 identical telescope and camera setups along the path of totality during the total solar eclipse (TSE) on 8 April 2024 to capture a 60-minute movie of the inner and middle solar corona in polarized visible light. The 2024 TSE path covered a large geographic swath of North America and we recruited and trained 36 teams of community participants ("citizen scientists") representative of the various communities along the path of totality. Afterwards, these teams retained the equipment in their communities for ongoing education and public engagement activities. Participants ranged from students (K12, undergraduate, and graduate), educators, and adult learners to amateur and professional astronomers. In addition to equipment for their communities, CATE 2024 teams received hands-on telescope training, educational and learning materials, and instruction on data analysis techniques. CATE 2024 used high-cadence, high-dynamic-range (HDR) polarimetric observations of the solar corona to characterize the physical processes that shape its heating, structure, and evolution at scales and sensitivities that cannot be studied outside of a TSE. Conventional eclipse observations do not span sufficient time to capture changing coronal topology, but the extended observation from CATE 2024 does. Analysis of the fully calibrated dataset will provide deeper insight and understanding into these critical physical processes. We present an overview of the CATE 2024 project, including how we engaged local communities along the path of totality, and the first look at CATE 2024 data products from the 2024 TSE.
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All authors Sarah A. Kovac, Amir Caspi, Daniel B. Seaton, Paul Bryans, Joan R. Burkepile, Sarah J. Davis, Craig E. DeForest, David Elmore, Sanjay Gosain, Rebecca Haacker, Marcus Hughes, Jason Jackiewicz, Viliam Klein, Derek Lamb, Valentin Martinez Pillet, Evy McUmber, Ritesh Patel, Kevin Reardon, Willow Reed, Anna Tosolini, Andrei E. Ursache, John K. Williams, Padma A. Yanamandra-Fisher, Daniel W. Zietlow, John Carini, Charles H. Gardner, Shawn Laatsch, Patricia H. Reiff, Nikita Saini, Rachael L. Weir, Kira F. Baasch, Jacquelyn Bellefontaine, Timothy D. Collins, Ryan J. Ferko, Leticia Ferrer, Margaret Hill, Jonathan M. Kessler, Jeremy A. Lusk, Jennifer Miller-Ray, Catarino Morales III, Brian W. Murphy, Kayla L. Olson, Mark J. Percy, Gwen Perry, Andrea A. Rivera, Aarran W. Shaw, Erik Stinnett, Eden L. Thompson, Hazel S. Wilkins, Yue Zhang, Angel Allison, John J. Alves, Angelica A. Alvis, Lucinda J. Alvis, Alvin J.G. Angeles, Aalasia Batchelor, Robert Benedict, Amelia Bettati, Abbie Bevill, Katherine Bibee Wolfson, Christina Raye Bingham, Bradley A. Bolton, Iris P. Borunda, Mario F. Borunda, Adam Bowen, Daniel L. Brookshier, MerRick Brown, Fred Bruenjes, Lisa Bunselmeier, Brian E. Burke, Bo Chen, Chi-Jui Chen, Zhean Chen, Marcia Chenevey Long, Nathaniel D. Cook, Tommy Copeland, Adrian J. Corter, Lawson L. Corter, Michael J. Corter, Theresa N. Costilow, Lori E. Cypert, Derrion Crouch-Bond, Beata Csatho, Clayton C. Cundiff, Stella S. Cundiff, Darrell DeMotta, Judy Dickey, Hannah L. Dirlam, Nathan Dodson, Donovan Driver, Jennifer Dudley-Winter, Justin Dulyanunt, Jordan R. Duncan, Scarlett C. Dyer, Lizabeth D. Eason, Timothy E. Eason, Jerry L. Edwards, Jaylynn N. Eisenhour, Ogheneovo N. Erho, Elijah J. Fleming, Andrew J. Fritsch III, Stephanie D. Frosch, Sahir Gagan, Joshua Gamble, Caitlyn L. Geisheimer, Ashleyahna George, Treva D. Gough, Jo Lin Gowing, Robert Greeson, Julie D. Griffin, Justin L. Grover, Simon L. Grover, Annie Hadley, Austin S. Hailey, Katrina B. Halasa, Jacob Harrison, Rachael Heltz Herman, Melissa Hentnik, Robert Hentnik, Mark Herman, Brenda G. Henderson, David T. Henderson, J. Michael Henthorn II, Thomas Hogue, Billy J. House, Toni Ray Howe, Brianna N. Isola, Mark A. Iwen, Jordyn Johnson, Richard O. Johnson III, Sophia P. Jones, Hanieh Karimi, Katy R. Kiser, Michael K. Koomson Jr., Morgan M. Koss, Ryan P. Kovacs, Carol A. Kovalak Martin, Kassidy Lange, Kyle Lawrence Leathers, Michael H. Lee, Kevin W. Lehman, Garret R. Leopold, Hsiao-Chun Lin, Heather Liptak, Logan Liptak, Michael A. Liptak, Alonso Lopez, Evan L. Lopez, Don Loving, April Luehmann, Kristen M. Lusk, Tia L. MacDonald, Ian A. Mannings, Priscilla Marin, Christopher J. Martin, Jamie Martin, Alejandra Olivia Martinez, Terah L. Martinez, Elizabeth S. Mays, Seth McGowan, Edward M. McHenry III, Kaz Meszaros, Tyler J. Metivier, Quinn W. Miller, Adam V. Miranda, Carlos Miranda, Pranvera Miranda, David M. W. Mitchell, Lydia N. Montgomery, Christopher P. Morse, Lillie B. Moore, Ira S. Morse, Raman Mukundan, Patrick T. Murphy, Nicarao J. Narvaez, Ahmed Nasreldin, Thomas Neel, Travis A. Nelson, Ellianna Nestlerode, Adam Z. Neuville, Brian A. Neuville, Allison Newberg, Jeremy L. Nicholson, Makenna F. Nickens, Sining Niu, Jedidiah O'Brien, Luis A. Otero, Jacob A. Ott, Joel A. Ott, Justin M. Ott, Michael E. Ott, Shekhar Pant, Ivan Parmuzin, Eric J. Parr, Sagar P. Paudel, Courtney M. Payne, Hayden B. Phillips, Elizabeth R. Prinkey, Kwesi A. Quagraine, Wesley J. Reddish, Azariah Rhodes, Stephen Kyle Rimler, Carlyn S. Rocazella, Tiska E. Rodgers, Devalyn Rogers, Oren R. Ross, Benjamin D. Roth, Melissa Rummel, John F. Rusho, Michael W. Sampson, Sophia Saucerman, James Scoville, Martin Wayne Seifert, Michael H. Seile Sr., Thomas G. Skirko, Asad Shahab, David C. Smith, Emily R. Snode-Brenneman, Cassandra Spaulding, Neha Srivastava, Amy L. Strecker, Aidan Sweets, Morghan Taylor, Deborah S. Teuscher, Owen Totten, Stephen Totten, Stephanie Totten, Andrew Totten, Corina R. Ursache, Susan V. Benedict, Yolanda Vasquez, R. Anthony Vincent, Alan Webb, Walter Webb, Roderick M. Weinschenk, Sedrick Weinschenk, Cash A. Wendel, Elisabeth Wheeler, Bethany A. Whitehouse, Gabriel J. Whitehouse, David A. Wiesner, Philip J. Williams, John A. Zakelj

Plasma Physics · Cross-listed from astro-ph.SR

The Maximum Particle Energy Gain During Magnetic Reconnection

Zhiyu Yin, Harry Arnold, James F Drake et al. (+1 more)

The factors that control the maximum energy attained by protons and electrons during magnetic reconnection are investigated analytically and using large-scale simulations with the kglobal model. Previous work revealed that a strong ambient guide field strongly impacts particle energy gain during reconnection, suppressing energy gain from Fermi reflection by increasing the radius of curvature of reconnected field lines. However, previous simulations have also shown that the maximum energy gain increases with the system size. The physical basis for this result has not been explored. We perform simulations that vary the effective system size over a large range to isolate the processes determining the maximum energy gain. The maximum energy $W_{max}$ is regulated by the number of magnetic-island mergers that occur, as multiple flux ropes that form at early time repeatedly merge until the largest approaches the system scale. Fermi reflection in these repeated mergers dominates particle energy gain. The number of mergers is linked to the effective system size – larger systems produce a larger number of flux ropes and more mergers. That $W_{max}$ is linked to the number of flux rope mergers has implications for understanding why particle-in-cell simulations only produce powerlaw distributions of energetic particles with a limited range in energy.
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All authors Zhiyu Yin, Harry Arnold, James F Drake, Marc Swisdak

Optics

Silicon photonic paper-clip spiral delay lines with ultra-low delay loss of 0.5 dB/ns

Batoul Hashemi, Manuel Arturo Méndez-Rosales, Parimal Edke et al. (+4 more)

In this work, we demonstrate compact paper-clip spiral silicon photonic waveguides with ultra-low delay loss. We characterize the optical loss and group delay of single-mode and multi-mode silicon waveguides across the telecom O-, S-, C-, and L-bands. For spiral devices with 2.0-{\mu}m-wide waveguides, we measure propagation losses of 0.11 and 0.06 dB/cm at 1310 and 1550 nm, representing 10- and 20-times improvements, respectively, compared to the singlemode waveguides. Additionally, we observe a group delay of 1163 ps for a 9.5 cm-long waveguide with a compact device footprint of (0.30 {\times} 3.00) mm2, yielding a delay loss of 0.5 dB/ns. These results are highly promising for large-scale silicon photonic integration, delay lines, and on-chip programmable systems.
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All authors Batoul Hashemi, Manuel Arturo Méndez-Rosales, Parimal Edke, Mohammad Rezaul Islam, Ranjan Das, Andrew P. Knights, Jonathan D. B. Bradley

Optics

Emergent learning: neuromorphic photonic computing with accelerated training

Sara Peña-Gutiérrez, Giorgio Gosti, Hongsheng Chen et al. (+2 more)

Emergent learning transforms a disordered optical medium into a photonic device capable of storage, recognition, and classification of arbitrary memory patterns. First, we show that the intensity at the output of a multiply scattering system can be described by a dyadic matrix, the optical-synaptic matrix, exhibiting the same form as a Hebbian synaptic matrix containing a single memory. Then, we employ emergent learning - an approach inspired by neuroscience - to exploit the vast dictionary of raw memories inherently available within a disordered optical structure, thereby engineering the optical-synaptic matrix to store a user-defined attractor, or tailored memory. Importantly these photonic structures also works as an optical comparators providing an intensity-based measure of the degree of similitude between a query pattern and the stored pattern, realizing an hardware co-localization between memory and optical operator. Our system has an almost infinite hardware capacity of tailored memories/ operators ($\mathcal{M} \sim 10^{60557}$), thus these tailored memories can be then employed as examples to build a classifier hardware based on intensity comparison without the need of additional digital transformation layers. Remarkably, this Photonic Emergent Learning platform is not only flexible and fabrication-free, but also relies primarily on analog processes, thus shifting the computational burden of training from the digital layers to the optical domain reducing the computational cost and enhancing performance.
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All authors Sara Peña-Gutiérrez, Giorgio Gosti, Hongsheng Chen, Giancarlo Ruocco, Marco Leonetti

Fluid Dynamics

Sheared stratified turbulence driven by Kolmogorov flow

Alessandro Sozza and Andrea Maffioli

We investigate three-dimensional turbulence in a stably stratified fluid driven by a vertically sheared Kolmogorov flow using direct numerical simulations of the Boussinesq equations. As stratification increases, mean profiles evolve toward piecewise-linear shapes while layered density structures emerge, with sharp interfaces separating well-mixed bulk layers. These highly stable interfaces form in the low-shear regions of the mean velocity profile and tend to promote flow relaminarisation, while shear-generated turbulence persists in the bulk layers. We analyse turbulent fluctuations, buoyancy transport and its spatial organisation, and flow stability via profiles of the gradient Richardson number $Ri_g$. The Richardson number in the bulk layers remains of order unity or less, $Ri_g \lesssim 1$, so that efficient turbulent shear production can take place there. Mixing efficiency analysis shows that the Nusselt number scales with the buoyancy Reynolds number $Re_b$ as $Nu = 1 + \Gamma Re_b$ (with $\Gamma = \epsilon_p / \epsilon$), with the data collapsing onto a robust master curve and roughly following a power-law $Nu \sim Re_b^{0.8}$. Further increase of stratification leads to a temporally intermittent turbulent regime, characterised by quasi-periodic bursts. We propose that the transition from stationary turbulence to this temporally intermittent regime is controlled by the buoyancy Reynolds number and highlight the mechanisms disrupting the turbulence and layered structures.
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Fluid Dynamics

On the complex interplay of temperature, phase change and natural convection in self-pressurization-an investigation using segregated modeling

David Barreiro-Villaverde, Antonio Cantiani and Miguel A. Mendez

Accurate prediction of self-pressurization in cryogenic tanks requires resolving the coupled effects of heat ingress, natural convection, and phase change. This work introduces a segregated numerical framework in which the liquid and vapor phases are treated with incompressible and compressible solvers, respectively, and the liquid-vapor interface is modeled as a sharp boundary subject to energy-jump conditions derived from first principles, without accommodation or tuning coefficients. Conjugate heat transfer through the tank walls is accounted for by solving the heat-conduction equation in the solid domain rather than prescribing external heat-flux conditions. The framework is validated against laboratory-scale LN2 and large-scale LH2 experiments, reproducing the spatio-temporal evolution of pressure and temperature without adjustable parameters. In both settings, the simulations identify two distinct regimes in self-pressurization: an initial heating-driven phase that establishes a self-similar temperature profile in the vapor, followed by an evaporation-driven phase in which the pressure rise is governed by the saturation relation. The comparison between these largely different scales motivated a revised scaling for self-pressurization, based on ullage thermodynamics. Finally, the influence of buoyancy was examined by reducing the strength of the gravitational body force, which revealed that natural convection modifies the duration of the transient heating phase but has a limited impact on the long-term pressurization rate. This analysis also clarifies the mechanism controlling the development of thermal stratification in the liquid. Overall, the segregated approach provides a predictive, parameter-free tool for analyzing cryogenic storage and offers a physically grounded basis for scaling self-pressurization across fluids, geometries, and heat-flux conditions.
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Instrumentation and Detectors

Influence of Radiation and AC Coupling on Time Performance of Analog Pixels Test Structures in 65 nm CMOS technology

Gianluca Aglieri Rinella, Luca Aglietta, Matias Antonelli et al. (+44 more)

Monolithic Active Pixel Sensors (MAPS) in advanced CMOS imaging technologies are key to next-generation tracking systems for high-energy physics, where radiation hardness and precise vertex reconstruction are essential. As part of the ALICE ITS3 R&D program in synergy with the CERN R&D, we evaluated the performance of the Analog Pixel Test Structures (APTS) fabricated in the TPSCo 65 nm CMOS imaging process. The prototypes employ 10 um pitch pixels with a fast operational amplifier-based buffering stage at the output, enabling direct characterization of intrinsic sensor response. Beam tests with minimum ionizing particles assessed the timing and charge collection of DC- and AC-coupled designs, including devices exposed to 10^14 NIEL and 10^15 NIEL non ioninsing energy loss. DC-coupled sensors demonstrated stable performance, maintaining time resolution lower than 70 ps and >99% detection efficiency up to 10^15 NIEL. AC-coupled sensors demonstrated a wide operational margin, with efficiencies above 99% for clusterization thresholds below 150 electrons. Even though the AC coupling allows higher reverse bias than DC-coupled sensors, the reduced signal amplitude lowers the signal-to-noise ratio, increasing the jitter contribution. At high reverse bias, the AC-coupled sensors achieve time resolutions comparable to the DC-coupled version, demonstrating the viability of both approaches. These results also suggest that combining the low capacitance of DC-coupled designs with the high-bias capability of AC coupling could further enhance time resolution. These results confirm the suitability of 65 nm MAPS for future collider detectors requiring high radiation tolerance, efficiency, and timing precision.
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All authors Gianluca Aglieri Rinella, Luca Aglietta, Matias Antonelli, Francesco Barile, Franco Benotto, Stefania Maria Beole, Elena Botta, Giuseppe Eugenio Bruno, Domenico Colella, Angelo Colelli, Giacomo Contin, Giuseppe De Robertis, Floarea Dumitrache, Domenico Elia, Chiara Ferrero, Martin Fransen, Alessandro Grelli, Hartmut Hillemanns, Isis Hobus, Alex Kluge, Shyam Kumar, Corentin Lemoine, Francesco Licciulli, Bong-Hwi Lim, Flavio Loddo, Esther Mwetaminwa M Bilo, Magnus Mager, Davide Marras, Paolo Martinengo, Cosimo Pastore, Rajendra Nath Patra, Stefania Perciballi, Francesco Piro, Francesco Prino, Luciano Ramello, Felix Reidt, Roberto Russo, Valerio Sarritzu, Umberto Savino, Serhiy Senyukov, Mario Sitta, Walter Snoeys, Jory Sonneveld, Miljenko Suljic, Triloki Triloki, Gianluca Usai, Haakan Wennlof

Space Physics · Cross-listed from astro-ph.SR

Evidence for in situ particle energization during the May-2024 event based on ASPEX instrument on board Aditya-L1

Shivam Parashar, Dibyendu Chakrabarty, Prashant Kumar et al. (+26 more)

The interaction between interplanetary Coronal Mass Ejection (ICME) structures can alter the geo-effectiveness of the ICME events in myriad ways. Many aspects of these interaction processes are not well-understood till date. Using the energy spectra measured in two mutually orthogonal top hat analyzers (THA 1 and 2), which are part of the Solar Wind Ion Spectrometer (SWIS) subsystem of the Aditya Solar Wind Particle EXperiment (ASPEX) on board India's Aditya L1 mission, we gain insights into intricate features of ICME ICME interactions during May 2024 solar event. We report here an unprecedented two-orthogonal-plane perspective of ICME ICME interactions for the first time from the L1 point. The investigation reveals a special interaction region formed by the propagation of the forward shock driven by complex ejecta in the preceding ICME. The interaction causes the formation of a downstream region spanning over 13 hours, which propagates in the interplanetary medium. The observations reveal that this region serves as a site for proton and alpha particle energization, and the particles within this region get distributed from one plane to the other. The presence of forward shock and particle energization is confirmed by the energetic particle flux measurements by the SupraThermal and Energetic Particle Spectrometer (STEPS) of ASPEX. These observations provide an unprecedented perspective on how solar wind ions become energized and distributed in an ICME-ICME interaction region.
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All authors Shivam Parashar, Dibyendu Chakrabarty, Prashant Kumar, Abhishek Kumar, Bhas Bapat, Aveek Sarkar, P. Janardhan, Anil Bhardwaj, Santosh V. Vadawale, Manan S. Shah, Hiteshkumar L. Adalja, Arpit R. Patel, Pranav R. Adhyaru, M. Shanmugam, Swarop B. Banerjee, K. P. Subramanian, Tinkal Ladia, Jacob Sebastian, Bijoy Dalal, Aakash Gupta, Shiv Kumar Goyal, Neeraj Kumar Tiwari, Aaditya Sarda, Sushil Kumar, Nishant Singh, Deepak Kumar Painkra, Piyush Sharma, Abhishek J. Verma, M. B. Dadhania

Optics

A precision apparatus for high harmonic spectroscopy in bulk solids

S. Mandal, P. Kumar, Z. Pi et al. (+3 more)

High harmonic generation (HHG) in solids has emerged as a powerful spectroscopic method for resolving ultrafast electron dynamics and band structure properties across a wide range of materials. However, quantitative HHG studies require instrumentation capable of delivering stable driving fields, precise crystal alignment, and broadband detection spanning the UV to the extreme ultraviolet (EUV). Here we present an integrated apparatus engineered specifically for high-accuracy, field-strength and orientation-dependent HHG measurements in bulk solids. The system incorporates dispersion-neutral intensity-control for few-cycle pulses, a vacuum HHG module with sub-micrometer and sub-degree sample positioning, and an imaging assembly that stabilizes the focal spot position and enables spatial filtering of the emitted harmonics. A synchronized dual-spectrometer scheme provides simultaneous UV/VUV and EUV radiation detection, while absolute electric field calibration is achieved through gas-phase attosecond streaking. Together, these capabilities establish a versatile and quantitatively reliable platform for solid-state HHG spectroscopy. The methodology is broadly adaptable to various laser sources and material classes, and supports future efforts aimed at reconstructing valence-electron potentials, tracking strong-field dynamics, and mapping electronic structure with sub-cycle temporal resolution.
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All authors S. Mandal, P. Kumar, Z. Pi, H. Y. Kim, M. Zhan, E. Goulielmakis

Applied Physics · Cross-listed from cs.CE

On the impact of geometric variance on the performance of formed parts: A probabilistic approach on the example of airbag pressure bins

Lukas Schnelle, Niklas Fehlemann, Ali O.M. Kilicsoy et al. (+6 more)

Scatter in properties resulting from manufacturing is a great challenge in lightweight design, requiring consideration of not only the average mechanical performance but also the variance which is done e.g., by conservative safety factors. One contributor to this variance is the inherent geometric variability in the formed part. To isolate and quantify this effect, we present a probabilistic numerical study, aiming to assess the impact of geometric variance on the resulting part performance. By modelling geometric deviations stochastically, we aim to establish a correlation between the variance in geometry with the resulting variance in performance. The study is done on the example of an airbag pressure bin, where a better understanding of this correlation is crucial, as it allows for the design of a lighter part without changing the manufacturing process. Instead, we aim to implement more targeted and effective quality assurance, informed by the performance impact of geometric deviations.
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All authors Lukas Schnelle, Niklas Fehlemann, Ali O.M. Kilicsoy, Niklas Bechler, Marcos A. Valdebenito, Yannis P. Korkolis, Matthias G.R. Faes, Sebastian Münstermann, Kai-Uwe Schröder

Physics and Society

Determining social mechanisms for sequential decision-making in a virtual pedestrian route choice experiment

Anna Sigalou, Yunhe Tong, Charlie Pilgrim et al. (+2 more)

Moving groups are routinely faced with a choice of different routes as part of their daily lives, such as choosing between exits from a building. Differences in moving speeds and environmental constraints often lead to individuals being able to observe the choices of others ahead. This social information can inform their decision-making, but exactly how this is being used remains an open question. Previous theoretical studies on animal groups have demonstrated that simple heuristics are plausible and accurate mechanisms, with some further predicting that more recent decisions are more heavily weighted. Experiments with fish corroborate the importance of more recent decisions; however, experimental work is limited. Here, we conduct an online survey with human participants to identify which social decision-making mechanism individuals follow. Contrary to previous experimental work, we find little indication that recent decisions are weighted more heavily; instead, our results suggest that following the majority of previous decisions is the dominant behaviour. Furthermore, self-reported decision-making mechanisms correlate with our experimental findings despite their variability, suggesting that on average individuals can recognize their behavioural tendencies. Our findings give insight into social sequential decision-making, and provide an empirical foundation for integrating realistic social decision mechanisms into pedestrian movement models.
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All authors Anna Sigalou, Yunhe Tong, Charlie Pilgrim, Richard P. Mann, Nikolai W.F. Bode

Atomic Physics · Cross-listed from cond-mat.quant-gas

Observation of a supersolid stripe state in two-dimensional dipolar gases

Yifei He, Haoting Zhen, Mithilesh K. Parit et al. (+5 more)

Fluctuations typically destroy long-range order in two-dimensional (2D) systems, posing a fundamental challenge to the existence of exotic states like supersolids, which paradoxically combine solid-like structure with frictionless superfluid flow. While long-predicted, the definitive observation of a 2D supersolid has remained an outstanding experimental goal. Here, we report the observation of a supersolid stripe phase in a strongly dipolar quantum gas of erbium atoms confined to 2D. We directly image the periodic density modulation, confirming its global phase coherence through matter-wave interference and demonstrating its phase rigidity relevant to the low-energy Goldstone mode, consistent with numerical calculations. Through collective excitation measurements, we demonstrate the hydrodynamic behavior of the supersolid. This work highlights a novel mechanism for supersolid formation in low dimensions, and opens the door for future research on the intricate interplay between temperature, supersolidity, and dimensionality.
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All authors Yifei He, Haoting Zhen, Mithilesh K. Parit, Mingchen Huang, Nicolò Defenu, Jordi Boronat, Juan Sánchez-Baena, Gyu-Boong Jo

History and Philosophy of Physics · Cross-listed from astro-ph.SR

Challenging historical novae: AT Cnc (1645), Te-11 (483), and M22 (BC 48) revisited

D.L. Neuhäuser, R. Neuhäuser, V. Hambaryan et al. (+2 more)

Connections between novae with shells and historical observations are crucial for astrophysical understanding of long-term evolution of shells and cataclysmic variables. Three of five previously considered links are revisited here: extended features in M22 in BC48, Te-11 in 483, and AT Cnc in 1645. We aim to develop a procedure to check whether these links are credible. Literal translations of the Chinese texts, historically based arguments, and close readings are combined with astrophysics, (peak brightness, decay time estimate, shell age expansion model calculation, etc.). (a) Nandou's second star, near which the BC48 `guest star' was reported, is identified as tau Sgr, not lambda Sgr, far from the M22 location. A nova in M22 would peak at only m=6.4 \pm 1.4 mag, and thus a description as a `blue-white' `melon' does not fit; it was likely a comet. (b) The imprecise position (`Shen['s] east') of the `guest star' in 483, its extended (dipper-like) radiance, and the context speak for a bolide. Considering the new (larger) Gaia distance and small extinction towards Te-11 (outside a cloud), its bi-polar morphology and current expansion velocity point to a planetary nebula; as a nova, the shell expansion age is 1100-2000 yr from detailed supersonic expansion calculations. (c) Most certainly, Mars was meant when the source for 1645 reported `a large star entered Yugui'; the verb implies motion. AT Cnc lies neither in Yugui's asterism box nor in the eponymous lunar mansion range. The fluid drag expansion age of AT Cancri's ejecta is 128-631 yr. All three exact ages are unsubstantiated. True novae or nova shells can be connected to historical records only if the position and object type are plausible. Duration, brightness (light curve), and color (evolution) should fit and could provide more astrophysical insight ...
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All authors D.L. Neuhäuser, R. Neuhäuser, V. Hambaryan, J. Chapman, M. Della Valle

Fluid Dynamics

Lagrangian Heterogeneous Multiscale Method (LHMM) for Simulating Polymer Solutions/Melts Behavior under Complex Flows using DPD-SPH

Edgar A. Patiño-Nariño, Nicolas Moreno and Marco Ellero

We present a Lagrangian Heterogeneous Multiscale Method (LHMM) for simulating the non-Newtonian rheology of polymer melts in complex two-dimensional flows. The method couples Dissipative Particle Dynamics (DPD) at the microscale with a GENERIC-compliant Smoothed Particle Hydrodynamics (SPH) at the macroscale, in a concurrent framework, overcoming the limitations of traditional Eulerian-based methods in capturing long-memory and history-dependent effects. At the microscale, DPD serves as a virtual rheometer, employing FENE (Finitely Extensible Nonlinear Elastic) bead-spring polymer chains. This approach provides key rheological properties, including shear-thinning and zero-shear-rate viscosities, relaxation times, and viscoelastic dynamics, which are quantified via Carreau-Yasuda fitting and spectral analysis. The LHMM couples SPH-derived strain rates with microscopic stress responses using the Irving-Kirkwood formalism. This approach enables a concurrent interaction between macroscopic strain rates and microscopic stress tensors, ensuring a consistent viscoelastic response across scales. The method is validated against benchmark flows, including Reverse Poiseuille Flow and flow through a Periodic Array of Cylinders, across Weissenberg numbers $0.5 < \text{Wi} < 30$ and low Reynolds numbers ($\text{Re} < 1$). A final demonstration of flow in a 2D porous medium highlights LHMM's capability to handle highly heterogeneous geometries. The LHMM is implemented in LAMMPS, making it suitable for integrating multiple models to describe microscales. In contrast, large-scale simulations efficiently utilize GPU and CPU resources, managing multiple coupling and time-scaling levels to maintain numerical stability and accuracy. The framework offers a predictive, constitutive-free tool that links microscopic polymer dynamics to macroscopic flow behavior, making it suitable for multiscale applications.
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Optics · Cross-listed from quant-ph

High-purity frequency-degenerate photon pair generation via cascaded SFG/SPDC in thin film lithium niobate

Olivia Hefti, Marco Clementi, Enrico Melani et al. (+12 more)

Frequency-degenerate photon pairs generated using nonlinear photonic integrated devices are a crucial resource for scalable quantum information processing and metrology. However, their realization is hindered by unwanted parametric processes occurring within the same phase matching band, which degrade the signal-to-noise ratio and reduce the purity of the associated quantum states. Here, we propose a dual-pump scheme to produce frequency-degenerate photon pairs, based on cascaded sum-frequency generation and spontaneous parametric down-conversion occurring within a single waveguide, while strongly suppressing parasitic photon pair generation from single-pump processes. This approach significantly simplifies the design compared to microresonator-based methods and enables both pumping and collection of photon pairs entirely in the telecom band. We experimentally validate the concept in a layer-poled thin film lithium niobate waveguide, achieving frequency-degenerate photon pair generation with a brightness of \SI{1.0(3)e5}{\hertz \per \nm \per \square \milli \watt } and a 40 dB suppression of unwanted single-pump processes.
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All authors Olivia Hefti, Marco Clementi, Enrico Melani, Jean-Etienne Tremblay, Andrea Volpini, Yesim Koyaz, Homa Zarebidaki, Ivan Prieto, Olivier Dubochet, Daniele Bajoni, Charles Caër, Hamed Sattari, Camille-Sophie Brès, Matteo Galli, Davide Grassani

Applied Physics · Cross-listed from eess.SY

Measurement of Material Volume Fractions in a Microwave Resonant Cavity Sensor Using Convolutional Neural Network

Mojtaba Joodaki and Idriz Pelaj

A non-destructive, real-time method for estimating the volume fraction of a dielectric mixture inside a resonant cavity is presented. A convolutional neural network (CNN)-based approach is used to estimate the fractional composition of two-phase dielectric mixtures inside a resonant cavity using scattering parameter (S-parameter) measurements. A rectangular cavity sensor with a strip feed structure is characterized using a vector network analyzer (VNA) from 0.01–20~GHz. The CNN is trained using both simulated and experimentally measured S-parameters and achieves high predictive accuracy even without de-embedding or filtering, demonstrating robustness to measurement imperfections. The simulation results achieve a coefficient of determination ($R^2$)=0.99 using $k$-fold cross-validation, while the experimental model using raw data achieves an $R^2=0.94$ with a mean absolute error (MAE) below 6%. Data augmentation further improves the accuracy of the experimental prediction to above $R^2=0.998$ (MAE$<$0.72%). The proposed method enables rapid, non-destructive, accurate, low-cost, and real-time estimation of material fractions, illustrating strong potential for sensing applications in microwave material characterization.
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Biological Physics

Mechanical Heterogeneity and the Nuclear Mechanome: Towards an Omics-Level Understanding of Nuclear Function

Lucia Benito-Barca, Carlos del Pozo-Rojas, Sandra Montalvo-Quiros et al. (+4 more)

The cell nucleus is increasingly recognized as a mechanosensitive organelle whose mesoscale mechanical heterogeneity (100 nm 10 um) is inseparable from genome regulation yet remains weakly integrated into systems biology and omics frameworks. Here we synthesize experimental and theoretical advances that define a nuclear mechanome: a multidimensional state of mechanical observables spanning lamins, chromatin, nucleoplasm and condensates, and varying across space, time, and cells. We review how intranuclear gradients, chromatin domains and phase-separated bodies generate viscoelastic, poroelastic and plastic niches that shape transcription, replication, DNA repair, epigenetic metabolism, and clonal selection, with particular emphasis on cancer, laminopathies and ageing. We survey invasive, optical and high throughput mechanophenotyping techniques, together with continuum, shell polymer, mesoscopic and non-equilibrium models, as a toolkit for mechanomic mapping. Finally, we outline a research agenda towards standardized mechanical descriptors, tissue-level mechano multi omic atlases and mechanotherapeutic strategies that explicitly target nuclear mechanotypes as potential biomarkers that can define cellular identity, explain plasticity, and help predict pathological states or the evolution of several diseases.
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All authors Lucia Benito-Barca, Carlos del Pozo-Rojas, Sandra Montalvo-Quiros, Ramiro Perezzan Rodriguez, Irene Alferez, Jorge Barcenilla, Diego Herraez-Aguilar

Chemical Physics

Combining Molecular Dynamics and Experimental Methods for the Parametrization of Binary Carbonate-Based Electrolytes

Lukas Lehnert, Martin Lorenz, Maria Fernanda Juarez et al. (+4 more)

Modelling the ionic transport in battery cells requires precise parametrization of the involved electrolytes. For carbonate-based electrolytes, however, the evaluation of their parameters suffers from interphase effects between the bulk electrolyte and the Li metal electrode, commonly present in the usual electrochemical polarization experiments. In this work, we combine measurements on conductivity and concentration cells with molecular dynamic simulations, avoiding these difficulties and thus, allowing for a more accurate determination of the parameters. We determine the conductivity, the transference number, the thermodynamic factor and the salt diffusion coefficient for three different electrolytes, i.e mixtures of ethylene carbonate (EC), ethyl methyl carbonate (EMC), methyl propionate (MP), dimethyl carbonate (DMC) and propylene carbonate (PC), containing LiPF$_6$ at various concentrations and temperatures. In order to validate the simulated transference numbers, we employ electrophoretic Nuclear Magnetic Resonance spectroscopy (eNMR).
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All authors Lukas Lehnert, Martin Lorenz, Maria Fernanda Juarez, Max Schammer, Maryam Nojabaee, Monika Schönhoff, Birger Horstmann

Fluid Dynamics · Cross-listed from cond-mat.soft

Self-assembled filament layers in drying sessile droplets: from morphology to electrical conductivity

Johannes Schöttner, Qingguang Xie, Gaurav Nath et al. (+1 more)

Controlling the deposition of filaments, such as nanowires and nanotubes, from evaporating droplets is critical for the performance of emerging technologies like flexible sensors and printed electronics. The final deposit morphology strongly governs functional properties, such as electrical conductivity, yet remains challenging to control. In this work, we numerically investigate how filament length, stiffness, and concentration affect deposition patterns during the drying process. We compare reaction-limited and diffusion-limited evaporation regimes, demonstrating that their distinct velocity fields and flow magnitudes fundamentally alter filament arrangement. While diffusion-limited evaporation drives the “coffee-ring effect", compromising network uniformity, reaction-limited evaporation suppresses edge accumulation, promoting centered conductive deposits. We map out the spatial variation of filament alignment - tangential at the contact line, radial in the intermediate region, and random near the center. Longer filaments tend to favour more tangential alignment overall and suppress edge accumulation. We find that by tuning the evaporation regime, filament deposition can lead to significantly lower percolation thresholds and significantly higher conductivity exponents. These results quantify the link between evaporation kinetics and microstructure, providing guidelines for optimizing conductive network formation in printed electronics.
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All authors Johannes Schöttner, Qingguang Xie, Gaurav Nath, Jens Harting