@article{994, abstract = {The formation of vortices is usually considered to be the main mechanism of angular momentum disposal in superfluids. Recently, it was predicted that a superfluid can acquire angular momentum via an alternative, microscopic route -- namely, through interaction with rotating impurities, forming so-called `angulon quasiparticles' [Phys. Rev. Lett. 114, 203001 (2015)]. The angulon instabilities correspond to transfer of a small number of angular momentum quanta from the impurity to the superfluid, as opposed to vortex instabilities, where angular momentum is quantized in units of ℏ per atom. Furthermore, since conventional impurities (such as molecules) represent three-dimensional (3D) rotors, the angular momentum transferred is intrinsically 3D as well, as opposed to a merely planar rotation which is inherent to vortices. Herein we show that the angulon theory can explain the anomalous broadening of the spectroscopic lines observed for CH 3 and NH 3 molecules in superfluid helium nanodroplets, thereby providing a fingerprint of the emerging angulon instabilities in experiment.}, author = {Cherepanov, Igor and Lemeshko, Mikhail}, journal = {Physical Review Materials}, number = {3}, publisher = {American Physical Society}, title = {{Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules}}, doi = {10.1103/PhysRevMaterials.1.035602}, volume = {1}, year = {2017}, } @article{995, abstract = {Recently it was shown that an impurity exchanging orbital angular momentum with a surrounding bath can be described in terms of the angulon quasiparticle [Phys. Rev. Lett. 118, 095301 (2017)]. The angulon consists of a quantum rotor dressed by a many-particle field of boson excitations, and can be formed out of, for example, a molecule or a nonspherical atom in superfluid helium, or out of an electron coupled to lattice phonons or a Bose condensate. Here we develop an approach to the angulon based on the path-integral formalism, which sets the ground for a systematic, perturbative treatment of the angulon problem. The resulting perturbation series can be interpreted in terms of Feynman diagrams, from which, in turn, one can derive a set of diagrammatic rules. These rules extend the machinery of the graphical theory of angular momentum - well known from theoretical atomic spectroscopy - to the case where an environment with an infinite number of degrees of freedom is present. In particular, we show that each diagram can be interpreted as a 'skeleton', which enforces angular momentum conservation, dressed by an additional many-body contribution. This connection between the angulon theory and the graphical theory of angular momentum is particularly important as it allows to systematically and substantially simplify the analytical representation of each diagram. In order to exemplify the technique, we calculate the 1- and 2-loop contributions to the angulon self-energy, the spectral function, and the quasiparticle weight. The diagrammatic theory we develop paves the way to investigate next-to-leading order quantities in a more compact way compared to the variational approaches.}, author = {Bighin, Giacomo and Lemeshko, Mikhail}, issn = {2469-9950}, journal = {Physical Review B - Condensed Matter and Materials Physics}, number = {8}, publisher = {American Physical Society}, title = {{Diagrammatic approach to orbital quantum impurities interacting with a many-particle environment}}, doi = {10.1103/PhysRevB.96.085410}, volume = {96}, year = {2017}, } @article{996, abstract = {Iodine (I 2 ) molecules embedded in He nanodroplets are aligned by a 160 ps long laser pulse. The highest degree of alignment, occurring at the peak of the pulse and quantified by ⟨cos 2 θ 2D ⟩ , is measured as a function of the laser intensity. The results are well described by ⟨cos 2 θ 2D ⟩ calculated for a gas of isolated molecules each with an effective rotational constant of 0.6 times the gas-phase value, and at a temperature of 0.4 K. Theoretical analysis using the angulon quasiparticle to describe rotating molecules in superfluid helium rationalizes why the alignment mechanism is similar to that of isolated molecules with an effective rotational constant. A major advantage of molecules in He droplets is that their 0.4 K temperature leads to stronger alignment than what can generally be achieved for gas phase molecules -- here demonstrated by a direct comparison of the droplet results to measurements on a ∼ 1 K supersonic beam of isolated molecules. This point is further illustrated for more complex system by measurements on 1,4-diiodobenzene and 1,4-dibromobenzene. For all three molecular species studied the highest values of ⟨cos 2 θ 2D ⟩ achieved in He droplets exceed 0.96. }, author = {Shepperson, Benjamin and Chatterley, Adam and Søndergaard, Anders and Christiansen, Lars and Lemeshko, Mikhail and Stapelfeldt, Henrik}, issn = {0021-9606}, journal = {The Journal of Chemical Physics}, number = {1}, publisher = {AIP Publishing}, title = {{Strongly aligned molecules inside helium droplets in the near-adiabatic regime}}, doi = {10.1063/1.4983703}, volume = {147}, year = {2017}, } @article{997, abstract = {Recently it was shown that molecules rotating in superfluid helium can be described in terms of the angulon quasiparticles (Phys. Rev. Lett. 118, 095301 (2017)). Here we demonstrate that in the experimentally realized regime the angulon can be seen as a point charge on a 2-sphere interacting with a gauge field of a non-abelian magnetic monopole. Unlike in several other settings, the gauge fields of the angulon problem emerge in the real coordinate space, as opposed to the momentum space or some effective parameter space. Furthermore, we find a topological transition associated with making the monopole abelian, which takes place in the vicinity of the previously reported angulon instabilities. These results pave the way for studying topological phenomena in experiments on molecules trapped in superfluid helium nanodroplets, as well as on other realizations of orbital impurity problems.}, author = {Yakaboylu, Enderalp and Deuchert, Andreas and Lemeshko, Mikhail}, issn = {0031-9007}, journal = {Physical Review Letters}, number = {23}, publisher = {American Physical Society}, title = {{Emergence of non-abelian magnetic monopoles in a quantum impurity problem}}, doi = {10.1103/PhysRevLett.119.235301}, volume = {119}, year = {2017}, } @inproceedings{998, abstract = {A major open problem on the road to artificial intelligence is the development of incrementally learning systems that learn about more and more concepts over time from a stream of data. In this work, we introduce a new training strategy, iCaRL, that allows learning in such a class-incremental way: only the training data for a small number of classes has to be present at the same time and new classes can be added progressively. iCaRL learns strong classifiers and a data representation simultaneously. This distinguishes it from earlier works that were fundamentally limited to fixed data representations and therefore incompatible with deep learning architectures. We show by experiments on CIFAR-100 and ImageNet ILSVRC 2012 data that iCaRL can learn many classes incrementally over a long period of time where other strategies quickly fail. }, author = {Rebuffi, Sylvestre Alvise and Kolesnikov, Alexander and Sperl, Georg and Lampert, Christoph}, isbn = {978-153860457-1}, location = {Honolulu, HA, United States}, pages = {5533 -- 5542}, publisher = {IEEE}, title = {{iCaRL: Incremental classifier and representation learning}}, doi = {10.1109/CVPR.2017.587}, volume = {2017}, year = {2017}, } @inproceedings{999, abstract = {In multi-task learning, a learner is given a collection of prediction tasks and needs to solve all of them. In contrast to previous work, which required that annotated training data must be available for all tasks, we consider a new setting, in which for some tasks, potentially most of them, only unlabeled training data is provided. Consequently, to solve all tasks, information must be transferred between tasks with labels and tasks without labels. Focusing on an instance-based transfer method we analyze two variants of this setting: when the set of labeled tasks is fixed, and when it can be actively selected by the learner. We state and prove a generalization bound that covers both scenarios and derive from it an algorithm for making the choice of labeled tasks (in the active case) and for transferring information between the tasks in a principled way. We also illustrate the effectiveness of the algorithm on synthetic and real data. }, author = {Pentina, Anastasia and Lampert, Christoph}, isbn = {9781510855144}, location = {Sydney, Australia}, pages = {2807 -- 2816}, publisher = {ML Research Press}, title = {{Multi-task learning with labeled and unlabeled tasks}}, volume = {70}, year = {2017}, } @inbook{424, abstract = {We show that very weak topological assumptions are enough to ensure the existence of a Helly-type theorem. More precisely, we show that for any non-negative integers b and d there exists an integer h(b, d) such that the following holds. If F is a finite family of subsets of Rd such that βi(∩G)≤b for any G⊊F and every 0 ≤ i ≤ [d/2]-1 then F has Helly number at most h(b, d). Here βi denotes the reduced Z2-Betti numbers (with singular homology). These topological conditions are sharp: not controlling any of these [d/2] first Betti numbers allow for families with unbounded Helly number. Our proofs combine homological non-embeddability results with a Ramsey-based approach to build, given an arbitrary simplicial complex K, some well-behaved chain map C*(K)→C*(Rd).}, author = {Goaoc, Xavier and Paták, Pavel and Patakova, Zuzana and Tancer, Martin and Wagner, Uli}, booktitle = {A Journey through Discrete Mathematics: A Tribute to Jiri Matousek}, editor = {Loebl, Martin and Nešetřil, Jaroslav and Thomas, Robin}, isbn = {978-331944479-6}, pages = {407 -- 447}, publisher = {Springer}, title = {{Bounding helly numbers via betti numbers}}, doi = {10.1007/978-3-319-44479-6_17}, year = {2017}, } @inproceedings{431, abstract = {Parallel implementations of stochastic gradient descent (SGD) have received significant research attention, thanks to its excellent scalability properties. A fundamental barrier when parallelizing SGD is the high bandwidth cost of communicating gradient updates between nodes; consequently, several lossy compresion heuristics have been proposed, by which nodes only communicate quantized gradients. Although effective in practice, these heuristics do not always converge. In this paper, we propose Quantized SGD (QSGD), a family of compression schemes with convergence guarantees and good practical performance. QSGD allows the user to smoothly trade off communication bandwidth and convergence time: nodes can adjust the number of bits sent per iteration, at the cost of possibly higher variance. We show that this trade-off is inherent, in the sense that improving it past some threshold would violate information-theoretic lower bounds. QSGD guarantees convergence for convex and non-convex objectives, under asynchrony, and can be extended to stochastic variance-reduced techniques. When applied to training deep neural networks for image classification and automated speech recognition, QSGD leads to significant reductions in end-to-end training time. For instance, on 16GPUs, we can train the ResNet-152 network to full accuracy on ImageNet 1.8 × faster than the full-precision variant. }, author = {Alistarh, Dan-Adrian and Grubic, Demjan and Li, Jerry and Tomioka, Ryota and Vojnović, Milan}, issn = {1049-5258}, location = {Long Beach, CA, United States}, pages = {1710--1721}, publisher = {Neural Information Processing Systems Foundation}, title = {{QSGD: Communication-efficient SGD via gradient quantization and encoding}}, volume = {2017}, year = {2017}, } @inproceedings{432, abstract = {Recently there has been significant interest in training machine-learning models at low precision: by reducing precision, one can reduce computation and communication by one order of magnitude. We examine training at reduced precision, both from a theoretical and practical perspective, and ask: is it possible to train models at end-to-end low precision with provable guarantees? Can this lead to consistent order-of-magnitude speedups? We mainly focus on linear models, and the answer is yes for linear models. We develop a simple framework called ZipML based on one simple but novel strategy called double sampling. Our ZipML framework is able to execute training at low precision with no bias, guaranteeing convergence, whereas naive quanti- zation would introduce significant bias. We val- idate our framework across a range of applica- tions, and show that it enables an FPGA proto- type that is up to 6.5 × faster than an implemen- tation using full 32-bit precision. We further de- velop a variance-optimal stochastic quantization strategy and show that it can make a significant difference in a variety of settings. When applied to linear models together with double sampling, we save up to another 1.7 × in data movement compared with uniform quantization. When training deep networks with quantized models, we achieve higher accuracy than the state-of-the- art XNOR-Net. }, author = {Zhang, Hantian and Li, Jerry and Kara, Kaan and Alistarh, Dan-Adrian and Liu, Ji and Zhang, Ce}, booktitle = {Proceedings of Machine Learning Research}, isbn = {978-151085514-4}, location = {Sydney, Australia}, pages = {4035 -- 4043}, publisher = {ML Research Press}, title = {{ZipML: Training linear models with end-to-end low precision, and a little bit of deep learning}}, volume = { 70}, year = {2017}, } @inbook{444, abstract = {Complex I (NADH:ubiquinone oxidoreductase) plays a central role in cellular energy generation, contributing to the proton motive force used to produce ATP. It couples the transfer of two electrons between NADH and quinone to translocation of four protons across the membrane. It is the largest protein assembly of bacterial and mitochondrial respiratory chains, composed, in mammals, of up to 45 subunits with a total molecular weight of ∼1 MDa. Bacterial enzyme is about half the size, providing the important “minimal” model of complex I. The l-shaped complex consists of a hydrophilic arm, where electron transfer occurs, and a membrane arm, where proton translocation takes place. Previously, we have solved the crystal structures of the hydrophilic domain of complex I from Thermus thermophilus and of the membrane domain from Escherichia coli, followed by the atomic structure of intact, entire complex I from T. thermophilus. Recently, we have solved by cryo-EM a first complete atomic structure of mammalian (ovine) mitochondrial complex I. Core subunits are well conserved from the bacterial version, whilst supernumerary subunits form an interlinked, stabilizing shell around the core. Subunits containing additional cofactors, including Zn ion, NADPH and phosphopantetheine, probably have regulatory roles. Dysfunction of mitochondrial complex I is implicated in many human neurodegenerative diseases. The structure of mammalian enzyme provides many insights into complex I mechanism, assembly, maturation and dysfunction, allowing detailed molecular analysis of disease-causing mutations.}, author = {Sazanov, Leonid A}, booktitle = {Mechanisms of primary energy transduction in biology }, editor = {Wikström, Mårten}, isbn = {978-1-78262-865-1}, pages = {25 -- 59}, publisher = {Royal Society of Chemistry}, title = {{Structure of respiratory complex I: “Minimal” bacterial and “de luxe” mammalian versions}}, doi = {10.1039/9781788010405-00025}, year = {2017}, } @article{447, abstract = {We consider last passage percolation (LPP) models with exponentially distributed random variables, which are linked to the totally asymmetric simple exclusion process (TASEP). The competition interface for LPP was introduced and studied in Ferrari and Pimentel (2005a) for cases where the corresponding exclusion process had a rarefaction fan. Here we consider situations with a shock and determine the law of the fluctuations of the competition interface around its deter- ministic law of large number position. We also study the multipoint distribution of the LPP around the shock, extending our one-point result of Ferrari and Nejjar (2015).}, author = {Ferrari, Patrik and Nejjar, Peter}, journal = {Revista Latino-Americana de Probabilidade e Estatística}, pages = {299 -- 325}, publisher = {Instituto Nacional de Matematica Pura e Aplicada}, title = {{Fluctuations of the competition interface in presence of shocks}}, doi = {10.30757/ALEA.v14-17}, volume = {9}, year = {2017}, } @article{452, abstract = {Spinning tops and yo-yos have long fascinated cultures around the world with their unexpected, graceful motions that seemingly elude gravity. Yet, due to the exceeding difficulty of creating stably spinning objects of asymmetric shape in a manual trial-and-error process, there has been little departure from rotationally symmetric designs. With modern 3D printing technologies, however, we can manufacture shapes of almost unbounded complexity at the press of a button, shifting this design complexity toward computation. In this article, we describe an algorithm to generate designs for spinning objects by optimizing their mass distribution: as input, the user provides a solid 3D model and a desired axis of rotation. Our approach then modifies the interior mass distribution such that the principal directions of the moment of inertia align with the target rotation frame. To create voids inside the model, we represent its volume with an adaptive multiresolution voxelization and optimize the discrete voxel fill values using a continuous, nonlinear formulation. We further optimize for rotational stability by maximizing the dominant principal moment. Our method is well-suited for a variety of 3D printed models, ranging from characters to abstract shapes. We demonstrate tops and yo-yos that spin surprisingly stably despite their asymmetric appearance.}, author = {Bächer, Moritz and Bickel, Bernd and Whiting, Emily and Sorkine Hornung, Olga}, journal = {Communications of the ACM}, number = {8}, pages = {92 -- 99}, publisher = {ACM}, title = {{Spin it: Optimizing moment of inertia for spinnable objects}}, doi = {10.1145/3068766}, volume = {60}, year = {2017}, } @article{453, abstract = {Most kinesin motors move in only one direction along microtubules. Members of the kinesin-5 subfamily were initially described as unidirectional plus-end-directed motors and shown to produce piconewton forces. However, some fungal kinesin-5 motors are bidirectional. The force production of a bidirectional kinesin-5 has not yet been measured. Therefore, it remains unknown whether the mechanism of the unconventional minus-end-directed motility differs fundamentally from that of plus-end-directed stepping. Using force spectroscopy, we have measured here the forces that ensembles of purified budding yeast kinesin-5 Cin8 produce in microtubule gliding assays in both plus- and minus-end direction. Correlation analysis of pause forces demonstrated that individual Cin8 molecules produce additive forces in both directions of movement. In ensembles, Cin8 motors were able to produce single-motor forces up to a magnitude of ∼1.5 pN. Hence, these properties appear to be conserved within the kinesin-5 subfamily. Force production was largely independent of the directionality of movement, indicating similarities between the motility mechanisms for both directions. These results provide constraints for the development of models for the bidirectional motility mechanism of fission yeast kinesin-5 and provide insight into the function of this mitotic motor.}, author = {Fallesen, Todd and Roostalu, Johanna and Düllberg, Christian F and Pruessner, Gunnar and Surrey, Thomas}, issn = {1542-0086}, journal = {Biophysical Journal}, number = {9}, pages = {2055 -- 2067}, publisher = {Biophysical Society}, title = {{Ensembles of bidirectional kinesin Cin8 produce additive forces in both directions of movement}}, doi = {10.1016/j.bpj.2017.09.006}, volume = {113}, year = {2017}, } @article{459, abstract = {The social insects bees, wasps, ants, and termites are species-rich, occur in many habitats, and often constitute a large part of the biomass. Many are also invasive, including species of termites, the red imported fire ant, and the Argentine ant. While invasive social insects have been a problem in Southern Europe for some time, Central Europa was free of invasive ant species until recently because most ants are adapted to warmer climates. Only in the 1990s, did Lasius neglectus, a close relative of the common black garden ant, arrive in Germany. First described in 1990 based on individuals collected in Budapest, the species has since been detected for example in France, Germany, Spain, England, and Kyrgyzstan. The species is spread with soil during construction work or plantings, and L. neglectus therefore is often found in parks and botanical gardens. Another invasive ant now spreading in southern Germany is Formica fuscocinerea, which occurs along rivers, including in the sandy floodplains of the river Isar. As is typical of pioneer species, F. fuscocinerea quickly becomes extremely abundant and therefore causes problems for example on playgrounds in Munich. All invasive ant species are characterized by cooperation across nests, leading to strongly interconnected, very large super-colonies. The resulting dominance results in the extinction of native ant species as well as other arthropod species and thus in the reduction of biodiversity.}, author = {Cremer, Sylvia}, issn = {2366-2875}, journal = {Rundgespräche Forum Ökologie}, pages = {105 -- 116}, publisher = {Verlag Dr. Friedrich Pfeil}, title = {{Invasive Ameisen in Europa: Wie sie sich ausbreiten und die heimische Fauna verändern}}, volume = {46}, year = {2017}, } @article{12193, abstract = {DNA methylation regulates eukaryotic gene expression and is extensively reprogrammed during animal development. However, whether developmental methylation reprogramming during the sporophytic life cycle of flowering plants regulates genes is presently unknown. Here we report a distinctive gene-targeted RNA-directed DNA methylation (RdDM) activity in the Arabidopsis thaliana male sexual lineage that regulates gene expression in meiocytes. Loss of sexual-lineage-specific RdDM causes mis-splicing of the MPS1 gene (also known as PRD2), thereby disrupting meiosis. Our results establish a regulatory paradigm in which de novo methylation creates a cell-lineage-specific epigenetic signature that controls gene expression and contributes to cellular function in flowering plants.}, author = {Walker, James and Gao, Hongbo and Zhang, Jingyi and Aldridge, Billy and Vickers, Martin and Higgins, James D. and Feng, Xiaoqi}, issn = {1546-1718}, journal = {Nature Genetics}, keywords = {Genetics}, number = {1}, pages = {130--137}, publisher = {Nature Research}, title = {{Sexual-lineage-specific DNA methylation regulates meiosis in Arabidopsis}}, doi = {10.1038/s41588-017-0008-5}, volume = {50}, year = {2017}, } @proceedings{638, abstract = {This book constitutes the refereed proceedings of the 9th InternationalWorkshop on Numerical Software Verification, NSV 2016, held in Toronto, ON, Canada in July 2011 - colocated with CAV 2016, the 28th International Conference on Computer Aided Verification. The NSV workshop is dedicated to the development of logical and mathematical techniques for the reasoning about programmability and reliability.}, editor = {Bogomolov, Sergiy and Martel, Matthieu and Prabhakar, Pavithra}, issn = {0302-9743}, location = {Toronto, ON, Canada}, publisher = {Springer}, title = {{Numerical Software Verification}}, doi = {10.1007/978-3-319-54292-8}, volume = {10152}, year = {2017}, } @inproceedings{1194, abstract = {Termination is one of the basic liveness properties, and we study the termination problem for probabilistic programs with real-valued variables. Previous works focused on the qualitative problem that asks whether an input program terminates with probability~1 (almost-sure termination). A powerful approach for this qualitative problem is the notion of ranking supermartingales with respect to a given set of invariants. The quantitative problem (probabilistic termination) asks for bounds on the termination probability. A fundamental and conceptual drawback of the existing approaches to address probabilistic termination is that even though the supermartingales consider the probabilistic behavior of the programs, the invariants are obtained completely ignoring the probabilistic aspect. In this work we address the probabilistic termination problem for linear-arithmetic probabilistic programs with nondeterminism. We define the notion of {\em stochastic invariants}, which are constraints along with a probability bound that the constraints hold. We introduce a concept of {\em repulsing supermartingales}. First, we show that repulsing supermartingales can be used to obtain bounds on the probability of the stochastic invariants. Second, we show the effectiveness of repulsing supermartingales in the following three ways: (1)~With a combination of ranking and repulsing supermartingales we can compute lower bounds on the probability of termination; (2)~repulsing supermartingales provide witnesses for refutation of almost-sure termination; and (3)~with a combination of ranking and repulsing supermartingales we can establish persistence properties of probabilistic programs. We also present results on related computational problems and an experimental evaluation of our approach on academic examples. }, author = {Chatterjee, Krishnendu and Novotny, Petr and Zikelic, Djordje}, issn = {0730-8566}, location = {Paris, France}, number = {1}, pages = {145 -- 160}, publisher = {ACM}, title = {{Stochastic invariants for probabilistic termination}}, doi = {10.1145/3009837.3009873}, volume = {52}, year = {2017}, } @inproceedings{637, abstract = {For many cryptographic primitives, it is relatively easy to achieve selective security (where the adversary commits a-priori to some of the choices to be made later in the attack) but appears difficult to achieve the more natural notion of adaptive security (where the adversary can make all choices on the go as the attack progresses). A series of several recent works shows how to cleverly achieve adaptive security in several such scenarios including generalized selective decryption (Panjwani, TCC ’07 and Fuchsbauer et al., CRYPTO ’15), constrained PRFs (Fuchsbauer et al., ASIACRYPT ’14), and Yao garbled circuits (Jafargholi and Wichs, TCC ’16b). Although the above works expressed vague intuition that they share a common technique, the connection was never made precise. In this work we present a new framework that connects all of these works and allows us to present them in a unified and simplified fashion. Moreover, we use the framework to derive a new result for adaptively secure secret sharing over access structures defined via monotone circuits. We envision that further applications will follow in the future. Underlying our framework is the following simple idea. It is well known that selective security, where the adversary commits to n-bits of information about his future choices, automatically implies adaptive security at the cost of amplifying the adversary’s advantage by a factor of up to 2n. However, in some cases the proof of selective security proceeds via a sequence of hybrids, where each pair of adjacent hybrids locally only requires some smaller partial information consisting of m ≪ n bits. The partial information needed might be completely different between different pairs of hybrids, and if we look across all the hybrids we might rely on the entire n-bit commitment. Nevertheless, the above is sufficient to prove adaptive security, at the cost of amplifying the adversary’s advantage by a factor of only 2m ≪ 2n. In all of our examples using the above framework, the different hybrids are captured by some sort of a graph pebbling game and the amount of information that the adversary needs to commit to in each pair of hybrids is bounded by the maximum number of pebbles in play at any point in time. Therefore, coming up with better strategies for proving adaptive security translates to various pebbling strategies for different types of graphs.}, author = {Jafargholi, Zahra and Kamath Hosdurg, Chethan and Klein, Karen and Komargodski, Ilan and Pietrzak, Krzysztof Z and Wichs, Daniel}, editor = {Katz, Jonathan and Shacham, Hovav}, isbn = {978-331963687-0}, location = {Santa Barbara, CA, United States}, pages = {133 -- 163}, publisher = {Springer}, title = {{Be adaptive avoid overcommitting}}, doi = {10.1007/978-3-319-63688-7_5}, volume = {10401}, year = {2017}, } @inproceedings{1001, abstract = {We present a computational approach for designing CurveUps, curvy shells that form from an initially flat state. They consist of small rigid tiles that are tightly held together by two pre-stretched elastic sheets attached to them. Our method allows the realization of smooth, doubly curved surfaces that can be fabricated as a flat piece. Once released, the restoring forces of the pre-stretched sheets support the object to take shape in 3D. CurveUps are structurally stable in their target configuration. The design process starts with a target surface. Our method generates a tile layout in 2D and optimizes the distribution, shape, and attachment areas of the tiles to obtain a configuration that is fabricable and in which the curved up state closely matches the target. Our approach is based on an efficient approximate model and a local optimization strategy for an otherwise intractable nonlinear optimization problem. We demonstrate the effectiveness of our approach for a wide range of shapes, all realized as physical prototypes.}, author = {Guseinov, Ruslan and Miguel, Eder and Bickel, Bernd}, location = {Los Angeles, CA, United States}, number = {4}, publisher = {ACM}, title = {{CurveUps: Shaping objects from flat plates with tension-actuated curvature}}, doi = {10.1145/3072959.3073709}, volume = {36}, year = {2017}, } @article{1120, abstract = {The existence of a self-localization transition in the polaron problem has been under an active debate ever since Landau suggested it 83 years ago. Here we reveal the self-localization transition for the rotational analogue of the polaron -- the angulon quasiparticle. We show that, unlike for the polarons, self-localization of angulons occurs at finite impurity-bath coupling already at the mean-field level. The transition is accompanied by the spherical-symmetry breaking of the angulon ground state and a discontinuity in the first derivative of the ground-state energy. Moreover, the type of the symmetry breaking is dictated by the symmetry of the microscopic impurity-bath interaction, which leads to a number of distinct self-localized states. The predicted effects can potentially be addressed in experiments on cold molecules trapped in superfluid helium droplets and ultracold quantum gases, as well as on electronic excitations in solids and Bose-Einstein condensates. }, author = {Li, Xiang and Seiringer, Robert and Lemeshko, Mikhail}, issn = {2469-9926}, journal = {Physical Review A}, number = {3}, publisher = {American Physical Society}, title = {{Angular self-localization of impurities rotating in a bosonic bath}}, doi = {10.1103/PhysRevA.95.033608}, volume = {95}, year = {2017}, }