@article{12790, abstract = {Motivated by the recent discoveries of superconductivity in bilayer and trilayer graphene, we theoretically investigate superconductivity and other interaction-driven phases in multilayer graphene stacks. To this end, we study the density of states of multilayer graphene with up to four layers at the single-particle band structure level in the presence of a transverse electric field. Among the considered structures, tetralayer graphene with rhombohedral (ABCA) stacking reaches the highest density of states. We study the phases that can arise in ABCA graphene by tuning the carrier density and transverse electric field. For a broad region of the tuning parameters, the presence of strong Coulomb repulsion leads to a spontaneous spin and valley symmetry breaking via Stoner transitions. Using a model that incorporates the spontaneous spin and valley polarization, we explore the Kohn-Luttinger mechanism for superconductivity driven by repulsive Coulomb interactions. We find that the strongest superconducting instability is in the p-wave channel, and occurs in proximity to the onset of Stoner transitions. Interestingly, we find a range of densities and transverse electric fields where superconductivity develops out of a strongly corrugated, singly connected Fermi surface in each valley, leading to a topologically nontrivial chiral p+ip superconducting state with an even number of copropagating chiral Majorana edge modes. Our work establishes ABCA-stacked tetralayer graphene as a promising platform for observing strongly correlated physics and topological superconductivity.}, author = {Ghazaryan, Areg and Holder, Tobias and Berg, Erez and Serbyn, Maksym}, issn = {2469-9969}, journal = {Physical Review B}, number = {10}, publisher = {American Physical Society}, title = {{Multilayer graphenes as a platform for interaction-driven physics and topological superconductivity}}, doi = {10.1103/PhysRevB.107.104502}, volume = {107}, year = {2023}, } @article{12791, abstract = {We investigate the capabilities of Physics-Informed Neural Networks (PINNs) to reconstruct turbulent Rayleigh–Bénard flows using only temperature information. We perform a quantitative analysis of the quality of the reconstructions at various amounts of low-passed-filtered information and turbulent intensities. We compare our results with those obtained via nudging, a classical equation-informed data assimilation technique. At low Rayleigh numbers, PINNs are able to reconstruct with high precision, comparable to the one achieved with nudging. At high Rayleigh numbers, PINNs outperform nudging and are able to achieve satisfactory reconstruction of the velocity fields only when data for temperature is provided with high spatial and temporal density. When data becomes sparse, the PINNs performance worsens, not only in a point-to-point error sense but also, and contrary to nudging, in a statistical sense, as can be seen in the probability density functions and energy spectra.}, author = {Clark Di Leoni, Patricio and Agasthya, Lokahith N and Buzzicotti, Michele and Biferale, Luca}, issn = {1292-895X}, journal = {The European Physical Journal E}, number = {3}, publisher = {Springer Nature}, title = {{Reconstructing Rayleigh–Bénard flows out of temperature-only measurements using Physics-Informed Neural Networks}}, doi = {10.1140/epje/s10189-023-00276-9}, volume = {46}, year = {2023}, } @article{12792, abstract = {In the physics literature the spectral form factor (SFF), the squared Fourier transform of the empirical eigenvalue density, is the most common tool to test universality for disordered quantum systems, yet previous mathematical results have been restricted only to two exactly solvable models (Forrester in J Stat Phys 183:33, 2021. https://doi.org/10.1007/s10955-021-02767-5, Commun Math Phys 387:215–235, 2021. https://doi.org/10.1007/s00220-021-04193-w). We rigorously prove the physics prediction on SFF up to an intermediate time scale for a large class of random matrices using a robust method, the multi-resolvent local laws. Beyond Wigner matrices we also consider the monoparametric ensemble and prove that universality of SFF can already be triggered by a single random parameter, supplementing the recently proven Wigner–Dyson universality (Cipolloni et al. in Probab Theory Relat Fields, 2021. https://doi.org/10.1007/s00440-022-01156-7) to larger spectral scales. Remarkably, extensive numerics indicates that our formulas correctly predict the SFF in the entire slope-dip-ramp regime, as customarily called in physics.}, author = {Cipolloni, Giorgio and Erdös, László and Schröder, Dominik J}, issn = {1432-0916}, journal = {Communications in Mathematical Physics}, pages = {1665--1700}, publisher = {Springer Nature}, title = {{On the spectral form factor for random matrices}}, doi = {10.1007/s00220-023-04692-y}, volume = {401}, year = {2023}, } @article{12818, abstract = {The multicellular organization of diverse systems, including embryos, intestines, and tumors relies on coordinated cell migration in curved environments. In these settings, cells establish supracellular patterns of motion, including collective rotation and invasion. While such collective modes have been studied extensively in flat systems, the consequences of geometrical and topological constraints on collective migration in curved systems are largely unknown. Here, we discover a collective mode of cell migration in rotating spherical tissues manifesting as a propagating single-wavelength velocity wave. This wave is accompanied by an apparently incompressible supracellular flow pattern featuring topological defects as dictated by the spherical topology. Using a minimal active particle model, we reveal that this collective mode arises from the effect of curvature on the active flocking behavior of a cell layer confined to a spherical surface. Our results thus identify curvature-induced velocity waves as a mode of collective cell migration, impacting the dynamical organization of 3D curved tissues.}, author = {Brandstätter, Tom and Brückner, David and Han, Yu Long and Alert, Ricard and Guo, Ming and Broedersz, Chase P.}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Curvature induces active velocity waves in rotating spherical tissues}}, doi = {10.1038/s41467-023-37054-2}, volume = {14}, year = {2023}, } @article{12819, abstract = {Reaching a high cavity population with a coherent pump in the strong-coupling regime of a single-atom laser is impossible due to the photon blockade effect. In this Letter, we experimentally demonstrate that in a single-atom maser based on a transmon strongly coupled to two resonators, it is possible to pump over a dozen photons into the system. The first high-quality resonator plays the role of a usual lasing cavity, and the second one presents a controlled dissipation channel, bolstering population inversion, and modifies the energy-level structure to lift the blockade. As confirmation of the lasing action, we observe conventional laser features such as a narrowing of the emission linewidth and external signal amplification. Additionally, we report unique single-atom features: self-quenching and several lasing thresholds.}, author = {Sokolova, Alesya and Kalacheva, D. A. and Fedorov, G. P. and Astafiev, O. V.}, issn = {2469-9934}, journal = {Physical Review A}, number = {3}, publisher = {American Physical Society}, title = {{Overcoming photon blockade in a circuit-QED single-atom maser with engineered metastability and strong coupling}}, doi = {10.1103/PhysRevA.107.L031701}, volume = {107}, year = {2023}, } @misc{12820, abstract = {Disulfide bond formation is fundamentally important for protein structure, and constitutes a key mechanism by which cells regulate the intracellular oxidation state. Peroxiredoxins (PRDXs) eliminate reactive oxygen species such as hydrogen peroxide through a catalytic cycle of Cys oxidation and reduction. Additionally, upon Cys oxidation PRDXs undergo extensive conformational rearrangements that may underlie their presently structurally poorly defined functions as molecular chaperones. Rearrangements include high molecular-weight oligomerization, the dynamics of which are, however, poorly understood, as is the impact of disulfide bond formation on these properties. Here we show that formation of disulfide bonds along the catalytic cycle induces extensive microsecond time scale dynamics, as monitored by magic-angle spinning NMR of the 216 kDa-large Tsa1 decameric assembly and solution-NMR of a designed dimeric mutant. We ascribe the conformational dynamics to structural frustration, resulting from conflicts between the disulfide-constrained reduction of mobility and the desire to fulfil other favorable contacts. This data repository contains NMR data presented in the associated manuscript}, author = {Schanda, Paul}, publisher = {Institute of Science and Technology Austria}, title = {{Research data of the publication "Disulfide-bond-induced structural frustration and dynamic disorder in a peroxiredoxin from MAS NMR"}}, doi = {10.15479/AT:ISTA:12820}, year = {2023}, } @article{12822, abstract = {Gears and cogwheels are elemental components of machines. They restrain degrees of freedom and channel power into a specified motion. Building and powering small-scale cogwheels are key steps toward feasible micro and nanomachinery. Assembly, energy injection, and control are, however, a challenge at the microscale. In contrast with passive gears, whose function is to transmit torques from one to another, interlocking and untethered active gears have the potential to unveil dynamics and functions untapped by externally driven mechanisms. Here, it is shown the assembly and control of a family of self-spinning cogwheels with varying teeth numbers and study the interlocking of multiple cogwheels. The teeth are formed by colloidal microswimmers that power the structure. The cogwheels are autonomous and active, showing persistent rotation. Leveraging the angular momentum of optical vortices, we control the direction of rotation of the cogwheels. The pairs of interlocking and active cogwheels that roll over each other in a random walk and have curvature-dependent mobility are studied. This behavior is leveraged to self-position parts and program microbots, demonstrating the ability to pick up, direct, and release a load. The work constitutes a step toward autonomous machinery with external control as well as (re)programmable microbots and matter.}, author = {Martinet, Quentin and Aubret, Antoine and Palacci, Jérémie A}, issn = {2640-4567}, journal = {Advanced Intelligent Systems}, number = {1}, publisher = {Wiley}, title = {{Rotation control, interlocking, and self‐positioning of active cogwheels}}, doi = {10.1002/aisy.202200129}, volume = {5}, year = {2023}, } @article{12829, abstract = {The deployment of direct formate fuel cells (DFFCs) relies on the development of active and stable catalysts for the formate oxidation reaction (FOR). Palladium, providing effective full oxidation of formate to CO2, has been widely used as FOR catalyst, but it suffers from low stability, moderate activity, and high cost. Herein, we detail a colloidal synthesis route for the incorporation of P on Pd2Sn nanoparticles. These nanoparticles are dispersed on carbon black and the obtained composite is used as electrocatalytic material for the FOR. The Pd2Sn0.8P-based electrodes present outstanding catalytic activities with record mass current densities up to 10.0 A mgPd-1, well above those of Pd1.6Sn/C reference electrode. These high current densities are further enhanced by increasing the temperature from 25 °C to 40 °C. The Pd2Sn0.8P electrode also allows for slowing down the rapid current decay that generally happens during operation and can be rapidly re-activated through potential cycling. The excellent catalytic performance obtained is rationalized using density functional theory (DFT) calculations.}, author = {Montaña-Mora, Guillem and Qi, Xueqiang and Wang, Xiang and Chacón-Borrero, Jesus and Martinez-Alanis, Paulina R. and Yu, Xiaoting and Li, Junshan and Xue, Qian and Arbiol, Jordi and Ibáñez, Maria and Cabot, Andreu}, issn = {1572-6657}, journal = {Journal of Electroanalytical Chemistry}, publisher = {Elsevier}, title = {{Phosphorous incorporation into palladium tin nanoparticles for the electrocatalytic formate oxidation reaction}}, doi = {10.1016/j.jelechem.2023.117369}, volume = {936}, year = {2023}, } @article{12830, abstract = {Interstitial fluid (IF) accumulation between embryonic cells is thought to be important for embryo patterning and morphogenesis. Here, we identify a positive mechanical feedback loop between cell migration and IF relocalization and find that it promotes embryonic axis formation during zebrafish gastrulation. We show that anterior axial mesendoderm (prechordal plate [ppl]) cells, moving in between the yolk cell and deep cell tissue to extend the embryonic axis, compress the overlying deep cell layer, thereby causing IF to flow from the deep cell layer to the boundary between the yolk cell and the deep cell layer, directly ahead of the advancing ppl. This IF relocalization, in turn, facilitates ppl cell protrusion formation and migration by opening up the space into which the ppl moves and, thereby, the ability of the ppl to trigger IF relocalization by pushing against the overlying deep cell layer. Thus, embryonic axis formation relies on a hydraulic feedback loop between cell migration and IF relocalization.}, author = {Huljev, Karla and Shamipour, Shayan and Nunes Pinheiro, Diana C and Preusser, Friedrich and Steccari, Irene and Sommer, Christoph M and Naik, Suyash and Heisenberg, Carl-Philipp J}, issn = {1878-1551}, journal = {Developmental Cell}, number = {7}, pages = {582--596.e7}, publisher = {Elsevier}, title = {{A hydraulic feedback loop between mesendoderm cell migration and interstitial fluid relocalization promotes embryonic axis formation in zebrafish}}, doi = {10.1016/j.devcel.2023.02.016}, volume = {58}, year = {2023}, } @article{12831, abstract = {The angulon, a quasiparticle formed by a quantum rotor dressed by the excitations of a many-body bath, can be used to describe an impurity rotating in a fluid or solid environment. Here, we propose a coherent state ansatz in the co-rotating frame, which provides a comprehensive theoretical description of angulons. We reveal the quasiparticle properties, such as energies, quasiparticle weights, and spectral functions, and show that our ansatz yields a persistent decrease in the impurity’s rotational constant due to many-body dressing, which is consistent with experimental observations. From our study, a picture of the angulon emerges as an effective spin interacting with a magnetic field that is self-consistently generated by the molecule’s rotation. Moreover, we discuss rotational spectroscopy, which focuses on the response of rotating molecules to a laser perturbation in the linear response regime. Importantly, we take into account initial-state interactions that have been neglected in prior studies and reveal their impact on the excitation spectrum. To examine the angulon instability regime, we use a single-excitation ansatz and obtain results consistent with experiments, in which a broadening of spectral lines is observed while phonon wings remain highly suppressed due to initial-state interactions.}, author = {Zeng, Zhongda and Yakaboylu, Enderalp and Lemeshko, Mikhail and Shi, Tao and Schmidt, Richard}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {13}, publisher = {American Institute of Physics}, title = {{Variational theory of angulons and their rotational spectroscopy}}, doi = {10.1063/5.0135893}, volume = {158}, year = {2023}, } @article{12832, abstract = {The development of cost-effective, high-activity and stable bifunctional catalysts for the oxygen reduction and evolution reactions (ORR/OER) is essential for zinc–air batteries (ZABs) to reach the market. Such catalysts must contain multiple adsorption/reaction sites to cope with the high demands of reversible oxygen electrodes. Herein, we propose a high entropy alloy (HEA) based on relatively abundant elements as a bifunctional ORR/OER catalyst. More specifically, we detail the synthesis of a CrMnFeCoNi HEA through a low-temperature solution-based approach. Such HEA displays superior OER performance with an overpotential of 265 mV at a current density of 10 mA/cm2, and a 37.9 mV/dec Tafel slope, well above the properties of a standard commercial catalyst based on RuO2. This high performance is partially explained by the presence of twinned defects, the incidence of large lattice distortions, and the electronic synergy between the different components, being Cr key to decreasing the energy barrier of the OER rate-determining step. CrMnFeCoNi also displays superior ORR performance with a half-potential of 0.78 V and an onset potential of 0.88 V, comparable with commercial Pt/C. The potential gap (Egap) between the OER overpotential and the ORR half-potential of CrMnFeCoNi is just 0.734 V. Taking advantage of these outstanding properties, ZABs are assembled using the CrMnFeCoNi HEA as air cathode and a zinc foil as the anode. The assembled cells provide an open-circuit voltage of 1.489 V, i.e. 90% of its theoretical limit (1.66 V), a peak power density of 116.5 mW/cm2, and a specific capacity of 836 mAh/g that stays stable for more than 10 days of continuous cycling, i.e. 720 cycles @ 8 mA/cm2 and 16.6 days of continuous cycling, i.e. 1200 cycles @ 5 mA/cm2.}, author = {He, Ren and Yang, Linlin and Zhang, Yu and Wang, Xiang and Lee, Seungho and Zhang, Ting and Li, Lingxiao and Liang, Zhifu and Chen, Jingwei and Li, Junshan and Ostovari Moghaddam, Ahmad and Llorca, Jordi and Ibáñez, Maria and Arbiol, Jordi and Xu, Ying and Cabot, Andreu}, issn = {2405-8297}, journal = {Energy Storage Materials}, number = {4}, pages = {287--298}, publisher = {Elsevier}, title = {{A CrMnFeCoNi high entropy alloy boosting oxygen evolution/reduction reactions and zinc-air battery performance}}, doi = {10.1016/j.ensm.2023.03.022}, volume = {58}, year = {2023}, } @article{12833, abstract = {The input to the token swapping problem is a graph with vertices v1, v2, . . . , vn, and n tokens with labels 1,2, . . . , n, one on each vertex. The goal is to get token i to vertex vi for all i= 1, . . . , n using a minimum number of swaps, where a swap exchanges the tokens on the endpoints of an edge.Token swapping on a tree, also known as “sorting with a transposition tree,” is not known to be in P nor NP-complete. We present some partial results: 1. An optimum swap sequence may need to perform a swap on a leaf vertex that has the correct token (a “happy leaf”), disproving a conjecture of Vaughan. 2. Any algorithm that fixes happy leaves—as all known approximation algorithms for the problem do—has approximation factor at least 4/3. Furthermore, the two best-known 2-approximation algorithms have approximation factor exactly 2. 3. A generalized problem—weighted coloured token swapping—is NP-complete on trees, but solvable in polynomial time on paths and stars. In this version, tokens and vertices have colours, and colours have weights. The goal is to get every token to a vertex of the same colour, and the cost of a swap is the sum of the weights of the two tokens involved.}, author = {Biniaz, Ahmad and Jain, Kshitij and Lubiw, Anna and Masárová, Zuzana and Miltzow, Tillmann and Mondal, Debajyoti and Naredla, Anurag Murty and Tkadlec, Josef and Turcotte, Alexi}, issn = {1365-8050}, journal = {Discrete Mathematics and Theoretical Computer Science}, number = {2}, publisher = {EPI Sciences}, title = {{Token swapping on trees}}, doi = {10.46298/DMTCS.8383}, volume = {24}, year = {2023}, } @article{12836, abstract = {Coherent control and manipulation of quantum degrees of freedom such as spins forms the basis of emerging quantum technologies. In this context, the robust valley degree of freedom and the associated valley pseudospin found in two-dimensional transition metal dichalcogenides is a highly attractive platform. Valley polarization and coherent superposition of valley states have been observed in these systems even up to room temperature. Control of valley coherence is an important building block for the implementation of valley qubit. Large magnetic fields or high-power lasers have been used in the past to demonstrate the control (initialization and rotation) of the valley coherent states. Here, the control of layer–valley coherence via strong coupling of valley excitons in bilayer WS2 to microcavity photons is demonstrated by exploiting the pseudomagnetic field arising in optical cavities owing to the transverse electric–transverse magnetic (TE–TM)mode splitting. The use of photonic structures to generate pseudomagnetic fields which can be used to manipulate exciton-polaritons presents an attractive approach to control optical responses without the need for large magnets or high-intensity optical pump powers.}, author = {Khatoniar, Mandeep and Yama, Nicholas and Ghazaryan, Areg and Guddala, Sriram and Ghaemi, Pouyan and Majumdar, Kausik and Menon, Vinod}, issn = {2195-1071}, journal = {Advanced Optical Materials}, number = {13}, publisher = {Wiley}, title = {{Optical manipulation of Layer–Valley coherence via strong exciton–photon coupling in microcavities}}, doi = {10.1002/adom.202202631}, volume = {11}, year = {2023}, } @article{12838, abstract = {We study the problem of high-dimensional multiple packing in Euclidean space. Multiple packing is a natural generalization of sphere packing and is defined as follows. Let N > 0 and L ∈ Z ≽2 . A multiple packing is a set C of points in R n such that any point in R n lies in the intersection of at most L – 1 balls of radius √ nN around points in C . Given a well-known connection with coding theory, multiple packings can be viewed as the Euclidean analog of list-decodable codes, which are well-studied for finite fields. In this paper, we derive the best known lower bounds on the optimal density of list-decodable infinite constellations for constant L under a stronger notion called average-radius multiple packing. To this end, we apply tools from high-dimensional geometry and large deviation theory.}, author = {Zhang, Yihan and Vatedka, Shashank}, issn = {1557-9654}, journal = {IEEE Transactions on Information Theory}, number = {7}, pages = {4513--4527}, publisher = {IEEE}, title = {{Multiple packing: Lower bounds via infinite constellations}}, doi = {10.1109/TIT.2023.3260950}, volume = {69}, year = {2023}, } @article{12839, abstract = {Universal nonequilibrium properties of isolated quantum systems are typically probed by studying transport of conserved quantities, such as charge or spin, while transport of energy has received considerably less attention. Here, we study infinite-temperature energy transport in the kinetically constrained PXP model describing Rydberg atom quantum simulators. Our state-of-the-art numerical simulations, including exact diagonalization and time-evolving block decimation methods, reveal the existence of two distinct transport regimes. At moderate times, the energy-energy correlation function displays periodic oscillations due to families of eigenstates forming different su(2) representations hidden within the spectrum. These families of eigenstates generalize the quantum many-body scarred states found in previous works and leave an imprint on the infinite-temperature energy transport. At later times, we observe a long-lived superdiffusive transport regime that we attribute to the proximity of a nearby integrable point. While generic strong deformations of the PXP model indeed restore diffusive transport, adding a strong chemical potential intriguingly gives rise to a well-converged superdiffusive exponent z≈3/2. Our results suggest constrained models to be potential hosts of novel transport regimes and call for developing an analytic understanding of their energy transport.}, author = {Ljubotina, Marko and Desaules, Jean Yves and Serbyn, Maksym and Papić, Zlatko}, issn = {2160-3308}, journal = {Physical Review X}, number = {1}, publisher = {American Physical Society}, title = {{Superdiffusive energy transport in kinetically constrained models}}, doi = {10.1103/PhysRevX.13.011033}, volume = {13}, year = {2023}, } @inproceedings{12854, abstract = {The main idea behind BUBAAK is to run multiple program analyses in parallel and use runtime monitoring and enforcement to observe and control their progress in real time. The analyses send information about (un)explored states of the program and discovered invariants to a monitor. The monitor processes the received data and can force an analysis to stop the search of certain program parts (which have already been analyzed by other analyses), or to make it utilize a program invariant found by another analysis. At SV-COMP 2023, the implementation of data exchange between the monitor and the analyses was not yet completed, which is why BUBAAK only ran several analyses in parallel, without any coordination. Still, BUBAAK won the meta-category FalsificationOverall and placed very well in several other (sub)-categories of the competition.}, author = {Chalupa, Marek and Henzinger, Thomas A}, booktitle = {Tools and Algorithms for the Construction and Analysis of Systems}, isbn = {9783031308192}, issn = {1611-3349}, location = {Paris, France}, pages = {535--540}, publisher = {Springer Nature}, title = {{Bubaak: Runtime monitoring of program verifiers}}, doi = {10.1007/978-3-031-30820-8_32}, volume = {13994}, year = {2023}, } @inproceedings{12856, abstract = {As the complexity and criticality of software increase every year, so does the importance of run-time monitoring. Third-party monitoring, with limited knowledge of the monitored software, and best-effort monitoring, which keeps pace with the monitored software, are especially valuable, yet underexplored areas of run-time monitoring. Most existing monitoring frameworks do not support their combination because they either require access to the monitored code for instrumentation purposes or the processing of all observed events, or both. We present a middleware framework, VAMOS, for the run-time monitoring of software which is explicitly designed to support third-party and best-effort scenarios. The design goals of VAMOS are (i) efficiency (keeping pace at low overhead), (ii) flexibility (the ability to monitor black-box code through a variety of different event channels, and the connectability to monitors written in different specification languages), and (iii) ease-of-use. To achieve its goals, VAMOS combines aspects of event broker and event recognition systems with aspects of stream processing systems. We implemented a prototype toolchain for VAMOS and conducted experiments including a case study of monitoring for data races. The results indicate that VAMOS enables writing useful yet efficient monitors, is compatible with a variety of event sources and monitor specifications, and simplifies key aspects of setting up a monitoring system from scratch.}, author = {Chalupa, Marek and Mühlböck, Fabian and Muroya Lei, Stefanie and Henzinger, Thomas A}, booktitle = {Fundamental Approaches to Software Engineering}, isbn = {9783031308253}, issn = {1611-3349}, location = {Paris, France}, pages = {260--281}, publisher = {Springer Nature}, title = {{Vamos: Middleware for best-effort third-party monitoring}}, doi = {10.1007/978-3-031-30826-0_15}, volume = {13991}, year = {2023}, } @inproceedings{12859, abstract = {Machine learning models are vulnerable to adversarial perturbations, and a thought-provoking paper by Bubeck and Sellke has analyzed this phenomenon through the lens of over-parameterization: interpolating smoothly the data requires significantly more parameters than simply memorizing it. However, this "universal" law provides only a necessary condition for robustness, and it is unable to discriminate between models. In this paper, we address these gaps by focusing on empirical risk minimization in two prototypical settings, namely, random features and the neural tangent kernel (NTK). We prove that, for random features, the model is not robust for any degree of over-parameterization, even when the necessary condition coming from the universal law of robustness is satisfied. In contrast, for even activations, the NTK model meets the universal lower bound, and it is robust as soon as the necessary condition on over-parameterization is fulfilled. This also addresses a conjecture in prior work by Bubeck, Li and Nagaraj. Our analysis decouples the effect of the kernel of the model from an "interaction matrix", which describes the interaction with the test data and captures the effect of the activation. Our theoretical results are corroborated by numerical evidence on both synthetic and standard datasets (MNIST, CIFAR-10).}, author = {Bombari, Simone and Kiyani, Shayan and Mondelli, Marco}, booktitle = {Proceedings of the 40th International Conference on Machine Learning}, location = {Honolulu, HI, United States}, pages = {2738--2776}, publisher = {ML Research Press}, title = {{Beyond the universal law of robustness: Sharper laws for random features and neural tangent kernels}}, volume = {202}, year = {2023}, } @article{12861, abstract = {The field of indirect reciprocity investigates how social norms can foster cooperation when individuals continuously monitor and assess each other’s social interactions. By adhering to certain social norms, cooperating individuals can improve their reputation and, in turn, receive benefits from others. Eight social norms, known as the “leading eight," have been shown to effectively promote the evolution of cooperation as long as information is public and reliable. These norms categorize group members as either ’good’ or ’bad’. In this study, we examine a scenario where individuals instead assign nuanced reputation scores to each other, and only cooperate with those whose reputation exceeds a certain threshold. We find both analytically and through simulations that such quantitative assessments are error-correcting, thus facilitating cooperation in situations where information is private and unreliable. Moreover, our results identify four specific norms that are robust to such conditions, and may be relevant for helping to sustain cooperation in natural populations.}, author = {Schmid, Laura and Ekbatani, Farbod and Hilbe, Christian and Chatterjee, Krishnendu}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Quantitative assessment can stabilize indirect reciprocity under imperfect information}}, doi = {10.1038/s41467-023-37817-x}, volume = {14}, year = {2023}, } @article{12862, abstract = {Despite the considerable progress of in vivo neural recording techniques, inferring the biophysical mechanisms underlying large scale coordination of brain activity from neural data remains challenging. One obstacle is the difficulty to link high dimensional functional connectivity measures to mechanistic models of network activity. We address this issue by investigating spike-field coupling (SFC) measurements, which quantify the synchronization between, on the one hand, the action potentials produced by neurons, and on the other hand mesoscopic “field” signals, reflecting subthreshold activities at possibly multiple recording sites. As the number of recording sites gets large, the amount of pairwise SFC measurements becomes overwhelmingly challenging to interpret. We develop Generalized Phase Locking Analysis (GPLA) as an interpretable dimensionality reduction of this multivariate SFC. GPLA describes the dominant coupling between field activity and neural ensembles across space and frequencies. We show that GPLA features are biophysically interpretable when used in conjunction with appropriate network models, such that we can identify the influence of underlying circuit properties on these features. We demonstrate the statistical benefits and interpretability of this approach in various computational models and Utah array recordings. The results suggest that GPLA, used jointly with biophysical modeling, can help uncover the contribution of recurrent microcircuits to the spatio-temporal dynamics observed in multi-channel experimental recordings.}, author = {Safavi, Shervin and Panagiotaropoulos, Theofanis I. and Kapoor, Vishal and Ramirez Villegas, Juan F and Logothetis, Nikos K. and Besserve, Michel}, issn = {1553-7358}, journal = {PLoS Computational Biology}, number = {4}, publisher = {Public Library of Science}, title = {{Uncovering the organization of neural circuits with Generalized Phase Locking Analysis}}, doi = {10.1371/journal.pcbi.1010983}, volume = {19}, year = {2023}, }