@article{17922, abstract = {Gold–thiol contacts are ubiquitous across the physical and biological sciences in connecting organic molecules to surfaces. When thiols bind to gold in self-assembled monolayers (SAMs) the fate of the hydrogen remains a subject of profound debate—with implications for our understanding of their physical properties, spectroscopic features and formation mechanism(s). Exploiting measurements of the transmission through a molecular junction, which is highly sensitive to the nature of the molecule–electrode contact, we demonstrate here that the nature of the gold–sulfur bond in SAMs can be probed via single-molecule conductance measurements. Critically, we find that SAM measurements of dithiol-terminated molecular junctions yield a significantly lower conductance than solution measurements of the same molecule. Through numerous control experiments, conductance noise analysis and transport calculations based on density functional theory, we show that the gold–sulfur bond in SAMs prepared from the solution deposition of dithiols does not have chemisorbed character, which strongly suggests that under these widely used preparation conditions the hydrogen is retained.}, author = {Inkpen, Michael S. and Liu, Zhen–Fei and Li, Haixing and Campos, Luis M. and Neaton, Jeffrey B. and Venkataraman, Latha}, issn = {1755-4349}, journal = {Nature Chemistry}, number = {4}, pages = {351--358}, publisher = {Springer Nature}, title = {{Non-chemisorbed gold–sulfur binding prevails in self-assembled monolayers}}, doi = {10.1038/s41557-019-0216-y}, volume = {11}, year = {2019}, } @article{17924, abstract = {We demonstrate that imidazole based π–π stacked dimers form strong and efficient conductance pathways in single-molecule junctions using the scanning-tunneling microscope-break junction (STM-BJ) technique and density functional theory-based calculations. We first characterize an imidazole-gold contact by measuring the conductance of imidazolyl-terminated alkanes (im-N-im, N = 3–6). We show that the conductance of these alkanes decays exponentially with increasing length, indicating that the mechanism for electron transport is through tunneling or super-exchange. We also reveal that π–π stacked dimers can be formed between imidazoles and have better coupling than through-bond tunneling. These experimental results are rationalized by calculations of molecular junction transmission using non-equilibrium Green's function formalism. This study verifies the capability of imidazole as a Au-binding ligand to form stable single- and π-stacked molecule junctions at room temperature.}, author = {Fu, Tianren and Smith, Shanelle and Camarasa-Gómez, María and Yu, Xiaofang and Xue, Jiayi and Nuckolls, Colin and Evers, Ferdinand and Venkataraman, Latha and Wei, Sujun}, issn = {2041-6539}, journal = {Chemical Science}, number = {43}, pages = {9998--10002}, publisher = {Royal Society of Chemistry}, title = {{Enhanced coupling through π-stacking in imidazole-based molecular junctions}}, doi = {10.1039/c9sc03760h}, volume = {10}, year = {2019}, } @article{17925, abstract = {Recent years have seen tremendous progress towards understanding the relation between the molecular structure and function of organic field effect transistors. The metrics for organic field effect transistors, which are characterized by mobility and the on/off ratio, are known to be enhanced when the intermolecular interaction is strong and the intramolecular reorganization energy is low. While these requirements are adequate when describing organic field effect transistors with simple and planar aromatic molecular components, they are insufficient for complex building blocks, which have the potential to localize a carrier on the molecule. Here, we show that intramolecular conductivity can play a role in controlling device characteristics of organic field effect transistors made with macrocycle building blocks. We use two isomeric macrocyclic semiconductors that consist of perylene diimides linked with bithiophenes and find that the trans-linked macrocycle has a higher mobility than the cis-based device. Through a combination of single molecule junction conductance measurements of the components of the macrocycles, control experiments with acyclic counterparts to the macrocycles, and analyses of each of the materials using spectroscopy, electrochemistry, and density functional theory, we attribute the difference in electron mobility of the OFETs created with the two isomers to the difference in intramolecular conductivity of the two macrocycles.}, author = {Ball, Melissa L. and Zhang, Boyuan and Fu, Tianren and Schattman, Ayden M. and Paley, Daniel W. and Ng, Fay and Venkataraman, Latha and Nuckolls, Colin and Steigerwald, Michael L.}, issn = {2041-6539}, journal = {Chemical Science}, number = {40}, pages = {9339--9344}, publisher = {Royal Society of Chemistry}, title = {{The importance of intramolecular conductivity in three dimensional molecular solids}}, doi = {10.1039/c9sc03144h}, volume = {10}, year = {2019}, } @article{17926, abstract = {N-heterocyclic carbenes (NHCs) bind very strongly to transition metals due to their unique electronic structure featuring a divalent carbon atom with a lone pair in a highly directional sp2-hybridized orbital. As such, they can be assembled into monolayers on metal surfaces that have enhanced stability compared to their thiol-based counterparts. The utility of NHCs to form such robust self-assembled monolayers (SAMs) was only recently recognized and many fundamental questions remain. Here we investigate the structure and geometry of a series of NHCs on Au(111) using high-resolution X-ray photoelectron spectroscopy and density functional theory calculations. We find that the N-substituents on the NHC ring strongly affect the molecule–metal interaction and steer the orientation of molecules in the surface layer. In contrast to previous reports, our experimental and theoretical results provide unequivocal evidence that NHCs with N-methyl substituents bind to undercoordinated adatoms to form flat-lying complexes. In these SAMs, the donor–acceptor interaction between the NHC lone pair and the undercoordinated Au adatom is primarily responsible for the strong bonding of the molecules to the surface. NHCs with bulkier N-substituents prevent the formation of such complexes by forcing the molecules into an upright orientation. Our work provides unique insights into the bonding and geometry of NHC monolayers; more generally, it charts a clear path to manipulating the interaction between NHCs and metal surfaces using traditional coordination chemistry synthetic strategies.}, author = {Lovat, Giacomo and Doud, Evan A. and Lu, Deyu and Kladnik, Gregor and Inkpen, Michael S. and Steigerwald, Michael L. and Cvetko, Dean and Hybertsen, Mark S. and Morgante, Alberto and Roy, Xavier and Venkataraman, Latha}, issn = {2041-6539}, journal = {Chemical Science}, number = {3}, pages = {930--935}, publisher = {Royal Society of Chemistry}, title = {{Determination of the structure and geometry of N-heterocyclic carbenes on Au(111) using high-resolution spectroscopy}}, doi = {10.1039/c8sc03502d}, volume = {10}, year = {2019}, } @article{18195, abstract = {Phase transitions are driven by collective fluctuations of a system’s constituents that emerge at a critical point1. This mechanism has been extensively explored for classical and quantum systems in equilibrium, whose critical behaviour is described by the general theory of phase transitions. Recently, however, fundamentally distinct phase transitions have been discovered for out-of-equilibrium quantum systems, which can exhibit critical behaviour that defies this description and is not well understood1. A paradigmatic example is the many-body localization (MBL) transition, which marks the breakdown of thermalization in an isolated quantum many-body system as its disorder increases beyond a critical value2,3,4,5,6,7,8,9,10,11. Characterizing quantum critical behaviour in an MBL system requires probing its entanglement over space and time4,5,7, which has proved experimentally challenging owing to stringent requirements on quantum state preparation and system isolation. Here we observe quantum critical behaviour at the MBL transition in a disordered Bose–Hubbard system and characterize its entanglement via its multi-point quantum correlations. We observe the emergence of strong correlations, accompanied by the onset of anomalous diffusive transport throughout the system, and verify their critical nature by measuring their dependence on the system size. The correlations extend to high orders in the quantum critical regime and appear to form via a sparse network of many-body resonances that spans the entire system12,13. Our results connect the macroscopic phenomenology of the transition to the system’s microscopic structure of quantum correlations, and they provide an essential step towards understanding criticality and universality in non-equilibrium systems1,7,13.}, author = {Rispoli, Matthew and Lukin, Alexander and Schittko, Robert and Kim, Sooshin and Tai, M. Eric and Leonard, Julian and Greiner, Markus}, issn = {1476-4687}, journal = {Nature}, number = {7774}, pages = {385--389}, publisher = {Springer Nature}, title = {{Quantum critical behaviour at the many-body localization transition}}, doi = {10.1038/s41586-019-1527-2}, volume = {573}, year = {2019}, } @article{18196, abstract = {An interacting quantum system that is subject to disorder may cease to thermalize owing to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to understanding this phenomenon lies in the system’s entanglement, which is experimentally challenging to measure. We realize such a many-body–localized system in a disordered Bose-Hubbard chain and characterize its entanglement properties through particle fluctuations and correlations. We observe that the particles become localized, suppressing transport and preventing the thermalization of subsystems. Notably, we measure the development of nonlocal correlations, whose evolution is consistent with a logarithmic growth of entanglement entropy, the hallmark of many-body localization. Our work experimentally establishes many-body localization as a qualitatively distinct phenomenon from localization in noninteracting, disordered systems.}, author = {Lukin, Alexander and Rispoli, Matthew and Schittko, Robert and Tai, M. Eric and Kaufman, Adam M. and Choi, Soonwon and Khemani, Vedika and Leonard, Julian and Greiner, Markus}, issn = {1095-9203}, journal = {Science}, number = {6437}, pages = {256--260}, publisher = {American Association for the Advancement of Science}, title = {{Probing entanglement in a many-body–localized system}}, doi = {10.1126/science.aau0818}, volume = {364}, year = {2019}, } @inproceedings{18256, abstract = {"Beauty is in the eye of the beholder." This maxim, emphasizing the subjectivity of the perception of beauty, has enjoyed a wide consensus since ancient times. In the digital era, data-driven methods have been shown to be able to predict human-assigned beauty scores for facial images. In this work, we augment this ability and train a generative model that generates faces conditioned on a requested beauty score. In addition, we show how this trained generator can be used to "beautify" an input face image. By doing so, we achieve an unsupervised beautification model, in the sense that it relies on no ground truth target images. Our implementation is available on: https://github.com/beholdergan/Beholder-GAN.}, author = {Diamant, Nir and Zadok, Dean and Baskin, Chaim and Schwartz, Eli and Bronstein, Alexander}, booktitle = {2019 IEEE International Conference on Image Processing (ICIP)}, isbn = {9781538662502}, issn = {2381-8549}, location = {Taipei, Taiwan}, publisher = {IEEE}, title = {{Beholder-Gan: Generation and beautification of facial images with conditioning on their beauty level}}, doi = {10.1109/icip.2019.8803807}, year = {2019}, } @inproceedings{18257, abstract = {We consider the problem of localizing relevant subsets of non-rigid geometric shapes given only a partial 3D query as the input. Such problems arise in several challenging tasks in 3D vision and graphics, including partial shape similarity, retrieval, and non-rigid correspondence. We phrase the problem as one of alignment between short sequences of eigenvalues of basic differential operators, which are constructed upon a scalar function defined on the 3D surfaces. Our method therefore seeks for a scalar function that entails this alignment. Differently from existing approaches, we do not require solving for a correspondence between the query and the target, therefore greatly simplifying the optimization process; our core technique is also descriptor-free, as it is driven by the geometry of the two objects as encoded in their operator spectra. We further show that our spectral alignment algorithm provides a remarkably simple alternative to the recent shape-from-spectrum reconstruction approaches. For both applications, we demonstrate improvement over the state-of-the-art either in terms of accuracy or computational cost.}, author = {Rampini, Arianna and Tallini, Irene and Ovsjanikov, Maks and Bronstein, Alexander and Rodola, Emanuele}, booktitle = {2019 International Conference on 3D Vision (3DV)}, isbn = {9781728131320}, issn = {2475-7888}, location = {Quebec City, QC, Canada}, publisher = {IEEE}, title = {{Correspondence-free region localization for partial shape similarity via Hamiltonian spectrum alignment}}, doi = {10.1109/3dv.2019.00014}, year = {2019}, } @inproceedings{18261, author = {Tsitsulin, Anton and Mottin, Davide and Karras, Panagiotis and Bronstein, Alexander and Müller, Emmanuel}, booktitle = {Companion Proceedings of The 2019 World Wide Web Conference}, isbn = {9781450366755}, location = {San Francisco, CA, United States}, pages = {308 -- 309}, publisher = {ACM}, title = {{Spectral graph complexity}}, doi = {10.1145/3308560.3316589}, year = {2019}, } @inproceedings{18262, abstract = {This paper explores a fully unsupervised deep learning approach for computing distance-preserving maps that generate low-dimensional embeddings for a certain class of manifolds. We use the Siamese configuration to train a neural network to solve the problem of least squares multidimensional scaling for generating maps that approximately preserve geodesic distances. By training with only a few landmarks, we show a significantly improved local and nonlocal generalization of the isometric mapping as compared to analogous non-parametric counterparts. Importantly, the combination of a deep-learning framework with a multidimensional scaling objective enables a numerical analysis of network architectures to aid in understanding their representation power. This provides a geometric perspective to the generalizability of deep learning.}, author = {Pai, Gautam and Talmon, Ronen and Bronstein, Alexander and Kimmel, Ron}, booktitle = {2019 IEEE Winter Conference on Applications of Computer Vision (WACV)}, isbn = {9781728119762}, location = {Waikoloa, HI, United States}, publisher = {IEEE}, title = {{DIMAL: Deep isometric manifold learning using sparse geodesic sampling}}, doi = {10.1109/wacv.2019.00092}, year = {2019}, } @article{18263, abstract = {We consider the tasks of representing, analysing and manipulating maps between shapes. We model maps as densities over the product manifold of the input shapes; these densities can be treated as scalar functions and therefore are manipulable using the language of signal processing on manifolds. Being a manifold itself, the product space endows the set of maps with a geometry of its own, which we exploit to define map operations in the spectral domain; we also derive relationships with other existing representations (soft maps and functional maps). To apply these ideas in practice, we discretize product manifolds and their Laplace–Beltrami operators, and we introduce localized spectral analysis of the product manifold as a novel tool for map processing. Our framework applies to maps defined between and across 2D and 3D shapes without requiring special adjustment, and it can be implemented efficiently with simple operations on sparse matrices.}, author = {Rodolà, E. and Lähner, Z. and Bronstein, Alexander and Bronstein, M. M. and Solomon, J.}, issn = {1467-8659}, journal = {Computer Graphics Forum}, number = {1}, pages = {678--689}, publisher = {Wiley}, title = {{Functional maps representation on product manifolds}}, doi = {10.1111/cgf.13598}, volume = {38}, year = {2019}, } @article{18264, abstract = {We present DeepISP, a full end-to-end deep neural model of the camera image signal processing pipeline. Our model learns a mapping from the raw low-light mosaiced image to the final visually compelling image and encompasses low-level tasks, such as demosaicing and denoising, as well as higher-level tasks, such as color correction and image adjustment. The training and evaluation of the pipeline were performed on a dedicated data set containing pairs of low-light and well-lit images captured by a Samsung S7 smartphone camera in both raw and processed JPEG formats. The proposed solution achieves the state-of-the-art performance in objective evaluation of peak signal-to-noise ratio on the subtask of joint denoising and demosaicing. For the full end-to-end pipeline, it achieves better visual quality compared to the manufacturer ISP, in both a subjective human assessment and when rated by a deep model trained for assessing image quality.}, author = {Schwartz, Eli and Giryes, Raja and Bronstein, Alexander}, issn = {1057-7149}, journal = {IEEE Transactions on Image Processing}, number = {2}, pages = {912--923}, publisher = {Institute of Electrical and Electronics Engineers}, title = {{DeepISP: Toward learning an end-to-end image processing pipeline}}, doi = {10.1109/tip.2018.2872858}, volume = {28}, year = {2019}, } @inproceedings{18268, abstract = {The registration of surfaces with non-rigid deformation, especially non-isometric deformations, is a challenging problem. When applying such techniques to real scans, the problem is compounded by topological and geometric inconsistencies between shapes. In this paper, we capture a benchmark dataset of scanned 3D shapes undergoing various controlled deformations (articulating, bending, stretching and topologically changing), along with ground truth correspondences. With the aid of this tiered benchmark of increasingly challenging real scans, we explore this problem and investigate how robust current state-of- the-art methods perform in different challenging registration and correspondence scenarios. We discover that changes in topology is a challenging problem for some methods and that machine learning-based approaches prove to be more capable of handling non-isometric deformations on shapes that are moderately similar to the training set.}, author = {Dyke, R.M. and Stride, C. and Lai, Y.-K. and Rosin, P.L. and Aubry, M. and Boyarski, A. and Bronstein, Alexander and Bronstein, M.M. and Cremers, D. and Fisher, M. and Groueix, T. and Guo, D. and Kim, V.G. and Kimmel, R. and Lähner, Z. and Li, K. and Litany, O. and Remez, T. and Rodola, E. and Russell, B.C. and Sahillioglu, Y. and Slossberg, R. and Tam, G.K.L. and Vestner, M. and Wu, Z. and Yang, J.}, booktitle = {Eurographics Workshop on 3D Object Retrieval}, issn = {1997-0471}, publisher = {The Eurographics Association}, title = {{Shape correspondence with isometric and non-isometric deformations}}, doi = {10.2312/3DOR.20191069}, year = {2019}, } @inproceedings{18269, abstract = {In the past few years, deep learning-based methods have demonstrated enormous success for solving inverse problems in medical imaging. In this work, we address the following question: Given a set of measurements obtained from real imaging experiments, what is the best way to use a learnable model and the physics of the modality to solve the inverse problem and reconstruct the latent image? Standard supervised learning based methods approach this problem by collecting data sets of known latent images and their corresponding measurements. However, these methods are often impractical due to the lack of availability of appropriately sized training sets, and, more generally, due to the inherent difficulty in measuring the “groundtruth” latent image. In light of this, we propose a self-supervised approach to training inverse models in medical imaging in the absence of aligned data. Our method only requiring access to the measurements and the forward model at training. We showcase its effectiveness on inverse problems arising in accelerated magnetic resonance imaging (MRI). }, author = {Senouf, Ortal and Vedula, Sanketh and Weiss, Tomer and Bronstein, Alexander and Michailovich, Oleg and Zibulevsky, Michael}, booktitle = {First MICCAI Workshop, DART 2019, and First International Workshop, MIL3ID 2019}, isbn = {9783030333904}, issn = {1611-3349}, location = {Shenzhen, China}, pages = {111 -- 119}, publisher = {Springer International Publishing}, title = {{Self-supervised learning of inverse problem solvers in medical imaging}}, doi = {10.1007/978-3-030-33391-1_13}, volume = {11795}, year = {2019}, } @article{22048, abstract = {We prove symplectic non-squeezing for the cubic nonlinear Schrödinger equation on the line via finite-dimensional approximation.}, author = {Killip, Rowan and Visan, Monica and Zhang, Xiaoyi}, issn = {1687-0247}, journal = {International Mathematics Research Notices}, number = {5}, pages = {1312--1332}, publisher = {Oxford University Press}, title = {{Symplectic non-squeezing for the cubic NLS on the line}}, doi = {10.1093/imrn/rnx152}, volume = {2019}, year = {2019}, } @article{22066, abstract = {We prove almost sure global existence and scattering for the energy-critical nonlinear Schrödinger equation with randomized spherically symmetric initial data in 𝐻𝑠⁡(ℝ4) with 5/6<𝑠<1. We were inspired to consider this problem by the recent work of Dodson–Lührmann–Mendelson, which treated the analogous problem for the energy-critical wave equation.}, author = {Killip, Rowan and Murphy, Jason and Visan, Monica}, issn = {1532-4133}, journal = {Communications in Partial Differential Equations}, number = {1}, pages = {51--71}, publisher = {Informa UK Limited}, title = {{Almost sure scattering for the energy-critical NLS with radial data below H1(R4)}}, doi = {10.1080/03605302.2018.1541904}, volume = {44}, year = {2019}, } @article{22077, abstract = {We prove inverse Strichartz theorems at L^2 regularity for a family of Schrödinger evolutions in one space dimension. Prior results rely on spacetime Fourier analysis and are limited to the translation-invariant equation i∂ t​ u=−1/2 Δu. Motivated by applications to the mass-critical Schrödinger equation with external potentials (such as the harmonic oscillator), we use a physical space approach.}, author = {Jao, Casey and Killip, Rowan and Visan, Monica}, issn = {2235-0616}, journal = {Revista Matemática Iberoamericana}, number = {3}, pages = {703--730}, publisher = {European Mathematical Society Press}, title = {{Mass-critical inverse Strichartz theorems for 1d Schrödinger operators}}, doi = {10.4171/rmi/1067}, volume = {35}, year = {2019}, } @article{10879, abstract = {We study effects of a bounded and compactly supported perturbation on multidimensional continuum random Schrödinger operators in the region of complete localisation. Our main emphasis is on Anderson orthogonality for random Schrödinger operators. Among others, we prove that Anderson orthogonality does occur for Fermi energies in the region of complete localisation with a non-zero probability. This partially confirms recent non-rigorous findings [V. Khemani et al., Nature Phys. 11 (2015), 560–565]. The spectral shift function plays an important role in our analysis of Anderson orthogonality. We identify it with the index of the corresponding pair of spectral projections and explore the consequences thereof. All our results rely on the main technical estimate of this paper which guarantees separate exponential decay of the disorder-averaged Schatten p-norm of χa(f(H)−f(Hτ))χb in a and b. Here, Hτ is a perturbation of the random Schrödinger operator H, χa is the multiplication operator corresponding to the indicator function of a unit cube centred about a∈Rd, and f is in a suitable class of functions of bounded variation with distributional derivative supported in the region of complete localisation for H.}, author = {Dietlein, Adrian M and Gebert, Martin and Müller, Peter}, issn = {1664-039X}, journal = {Journal of Spectral Theory}, keywords = {Random Schrödinger operators, spectral shift function, Anderson orthogonality}, number = {3}, pages = {921--965}, publisher = {EMS Press}, title = {{Perturbations of continuum random Schrödinger operators with applications to Anderson orthogonality and the spectral shift function}}, doi = {10.4171/jst/267}, volume = {9}, year = {2019}, } @article{439, abstract = {We count points over a finite field on wild character varieties,of Riemann surfaces for singularities with regular semisimple leading term. The new feature in our counting formulas is the appearance of characters of Yokonuma–Hecke algebras. Our result leads to the conjecture that the mixed Hodge polynomials of these character varieties agree with previously conjectured perverse Hodge polynomials of certain twisted parabolic Higgs moduli spaces, indicating the possibility of a P = W conjecture for a suitable wild Hitchin system.}, author = {Hausel, Tamas and Mereb, Martin and Wong, Michael}, issn = {1435-9855}, journal = {Journal of the European Mathematical Society}, number = {10}, pages = {2995--3052}, publisher = {EMS Press}, title = {{Arithmetic and representation theory of wild character varieties}}, doi = {10.4171/JEMS/896}, volume = {21}, year = {2019}, } @misc{9726, abstract = {A detailed description of the two stochastic models, table of parameters, supplementary data for Figures 4 and 5, parameter dependence of the results, and an analysis on motors with different force–velocity functions (PDF)}, author = {Ucar, Mehmet C and Lipowsky, Reinhard}, publisher = {American Chemical Society}, title = {{Supplementary information - Collective force generation by molecular motors is determined by strain-induced unbinding}}, doi = {10.1021/acs.nanolett.9b04445.s001}, year = {2019}, }