@inproceedings{11794, abstract = {We study individual rational, Pareto optimal, and incentive compatible mechanisms for auctions with heterogeneous items and budget limits. For multi-dimensional valuations we show that there can be no deterministic mechanism with these properties for divisible items. We use this to show that there can also be no randomized mechanism that achieves this for either divisible or indivisible items. For single-dimensional valuations we show that there can be no deterministic mechanism with these properties for indivisible items, but that there is a randomized mechanism that achieves this for either divisible or indivisible items. The impossibility results hold for public budgets, while the mechanism allows private budgets, which is in both cases the harder variant to show. While all positive results are polynomial-time algorithms, all negative results hold independent of complexity considerations.}, author = {Dütting, Paul and Henzinger, Monika H and Starnberger, Martin}, booktitle = {8th International Workshop on Internet and Network Economics}, isbn = {9783642353109}, issn = {1611-3349}, location = {Liverpool, United Kingdom}, pages = {44–57}, publisher = {Springer Nature}, title = {{Auctions with heterogeneous items and budget limits}}, doi = {10.1007/978-3-642-35311-6_4}, volume = {7695}, year = {2012}, } @article{808, abstract = {Using correlated live-cell imaging and electron tomography we found that actin branch junctions in protruding and treadmilling lamellipodia are not concentrated at the front as previously supposed, but link actin filament subsets in which there is a continuum of distances from a junction to the filament plus ends, for up to at least 1 mm. When branch sites were observed closely spaced on the same filament their separation was commonly a multiple of the actin helical repeat of 36 nm. Image averaging of branch junctions in the tomograms yielded a model for the in vivo branch at 2.9 nm resolution, which was comparable with that derived for the in vitro actin- Arp2/3 complex. Lamellipodium initiation was monitored in an intracellular wound-healing model and was found to involve branching from the sides of actin filaments oriented parallel to the plasmalemma. Many filament plus ends, presumably capped, terminated behind the lamellipodium tip and localized on the dorsal and ventral surfaces of the actin network. These findings reveal how branching events initiate and maintain a network of actin filaments of variable length, and provide the first structural model of the branch junction in vivo. A possible role of filament capping in generating the lamellipodium leaflet is discussed and a mathematical model of protrusion is also presented.}, author = {Vinzenz, Marlene and Nemethova, Maria and Schur, Florian and Mueller, Jan and Narita, Akihiro and Urban, Edit and Winkler, Christoph and Schmeiser, Christian and Koestler, Stefan and Rottner, Klemens and Resch, Guenter and Maéda, Yuichiro and Small, John}, journal = {Journal of Cell Science}, number = {11}, pages = {2775 -- 2785}, publisher = {Company of Biologists}, title = {{Actin branching in the initiation and maintenance of lamellipodia}}, doi = {10.1242/jcs.107623}, volume = {125}, year = {2012}, } @article{171, abstract = {For given non-zero integers a, b, q we investigate the density of solutions (x, y) ∈ ℤ2 to the binary cubic congruence ax2 + by3 ≡ 0 mod q, and use it to establish the Manin conjecture for a singular del Pezzo surface of degree 2 defined over ℚ.}, author = {Timothy Browning and Baier, Stephan}, journal = {Journal fur die Reine und Angewandte Mathematik}, number = {680}, pages = {1 -- 65}, publisher = {Walter de Gruyter}, title = {{Inhomogeneous cubic congruences and rational points on del Pezzo surfaces}}, doi = {https://doi.org/10.1515/crelle.2012.039}, volume = {2013}, year = {2012}, } @article{1756, abstract = {We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control of the relevant transport mechanisms was achieved by means of local electrostatic gating and temperature-dependent measurements. The roles of the source/drain contacts and of the silicon channel could be independently evaluated and tuned. Wrap gates surrounding the silicide-silicon contact interfaces were proved to be effective in inducing a full suppression of the contact Schottky barriers, thereby enabling carrier injection down to liquid helium temperature. By independently tuning the effective Schottky barrier heights, a variety of reconfigurable device functionalities could be obtained. In particular, the same nanowire device could be configured to work as a Schottky barrier transistor, a Schottky diode, or a p-n diode with tunable polarities. This versatility was eventually exploited to realize a NAND logic gate with gain well above one.}, author = {Mongillo, Massimo and Spathis, Panayotis N and Georgios Katsaros and Gentile, Pascal and De Franceschi, Silvano}, journal = {Nano Letters}, number = {6}, pages = {3074 -- 3079}, publisher = {American Chemical Society}, title = {{Multifunctional devices and logic gates with undoped silicon nanowires}}, doi = {10.1021/nl300930m}, volume = {12}, year = {2012}, } @article{1757, abstract = {Self-assembled Ge wires with a height of only 3 unit cells and a length of up to 2 micrometers were grown on Si(001) by means of a catalyst-free method based on molecular beam epitaxy. The wires grow horizontally along either the [100] or the [010] direction. On atomically flat surfaces, they exhibit a highly uniform, triangular cross section. A simple thermodynamic model accounts for the existence of a preferential base width for longitudinal expansion, in quantitative agreement with the experimental findings. Despite the absence of intentional doping, the first transistor-type devices made from single wires show low-resistive electrical contacts and single-hole transport at sub-Kelvin temperatures. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.}, author = {Zhang, Jianjun and Georgios Katsaros and Montalenti, Francesco and Scopece, Daniele and Rezaev, Roman O and Mickel, Christine H and Rellinghaus, Bernd and Miglio, Leo P and De Franceschi, Silvano and Rastelli, Armando and Schmidt, Oliver G}, journal = {Physical Review Letters}, number = {8}, publisher = {American Physical Society}, title = {{Monolithic growth of ultrathin Ge nanowires on Si(001) }}, doi = {10.1103/PhysRevLett.109.085502}, volume = {109}, year = {2012}, } @article{1758, abstract = {We studied the low-energy states of spin-1/2 quantum dots defined in InAs/InP nanowires and coupled to aluminum superconducting leads. By varying the superconducting gap Δ with a magnetic field B we investigated the transition from strong coupling Δ≪T K to weak-coupling Δ≫T K, where T K is the Kondo temperature. Below the critical field, we observe a persisting zero-bias Kondo resonance that vanishes only for low B or higher temperatures, leaving the room to more robust subgap structures at bias voltages between Δ and 2Δ. For strong and approximately symmetric tunnel couplings, a Josephson supercurrent is observed in addition to the Kondo peak. We ascribe the coexistence of a Kondo resonance and a superconducting gap to a significant density of intragap quasiparticle states, and the finite-bias subgap structures to tunneling through Shiba states. Our results, supported by numerical calculations, own relevance also in relation to tunnel-spectroscopy experiments aiming at the observation of Majorana fermions in hybrid nanostructures.}, author = {Lee, Eduardo J and Jiang, Xiaocheng and Aguado, Ramón and Georgios Katsaros and Lieber, Charles M and De Franceschi, Silvano}, journal = {Physical Review Letters}, number = {18}, publisher = {American Physical Society}, title = {{Zero-bias anomaly in a nanowire quantum dot coupled to superconductors}}, doi = {10.1103/PhysRevLett.109.186802}, volume = {109}, year = {2012}, } @article{1782, abstract = {Steering a quantum harmonic oscillator state along cyclic trajectories leads to a path-dependent geometric phase. Here we describe its experimental observation in an electronic harmonic oscillator. We use a superconducting qubit as a nonlinear probe of the phase, which is otherwise unobservable due to the linearity of the oscillator. We show that the geometric phase is, for a variety of cyclic paths, proportional to the area enclosed in the quadrature plane. At the transition to the nonadiabatic regime, we study corrections to the phase and dephasing of the qubit caused by qubit-resonator entanglement. In particular, we identify parameters for which this dephasing mechanism is negligible even in the nonadiabatic regime. The demonstrated controllability makes our system a versatile tool to study geometric phases in open quantum systems and to investigate their potential for quantum information processing.}, author = {Pechal, M and Berger, Stefan T and Abdumalikov, Abdufarrukh A and Johannes Fink and Mlynek, Jonas A and Steffen, L. Kraig and Wallraff, Andreas and Filipp, Stefan}, journal = {Physical Review Letters}, number = {17}, publisher = {American Physical Society}, title = {{Geometric phase and nonadiabatic effects in an electronic harmonic oscillator}}, doi = {10.1103/PhysRevLett.108.170401}, volume = {108}, year = {2012}, } @article{1783, abstract = {Nonlinearity and entanglement are two important properties by which physical systems can be identified as nonclassical. We study the dynamics of the resonant interaction of up to N=3 two-level systems and a single mode of the electromagnetic field sharing a single excitation dynamically. We observe coherent vacuum Rabi oscillations and their nonlinear √N speedup by tracking the populations of all qubits and the resonator in time. We use quantum state tomography to show explicitly that the dynamics generates maximally entangled states of the W class in a time limited only by the collective interaction rate. We use an entanglement witness and the 3-tangle to characterize the state whose fidelity F=78% is limited in our experiments by crosstalk arising during the simultaneous qubit manipulations which is absent in a sequential approach with F=91%.}, author = {Mlynek, Jonas A and Abdumalikov, Abdufarrukh A and Johannes Fink and Steffen, L. Kraig and Baur, Matthias P and Lang, C and Van Loo, Arjan F and Wallraff, Andreas}, journal = {Physical Review A - Atomic, Molecular, and Optical Physics}, number = {5}, publisher = {American Physical Society}, title = {{Demonstrating W-type entanglement of Dicke states in resonant cavity quantum electrodynamics}}, doi = {10.1103/PhysRevA.86.053838}, volume = {86}, year = {2012}, } @inproceedings{2048, abstract = {Leakage resilient cryptography attempts to incorporate side-channel leakage into the black-box security model and designs cryptographic schemes that are provably secure within it. Informally, a scheme is leakage-resilient if it remains secure even if an adversary learns a bounded amount of arbitrary information about the schemes internal state. Unfortunately, most leakage resilient schemes are unnecessarily complicated in order to achieve strong provable security guarantees. As advocated by Yu et al. [CCS’10], this mostly is an artefact of the security proof and in practice much simpler construction may already suffice to protect against realistic side-channel attacks. In this paper, we show that indeed for simpler constructions leakage-resilience can be obtained when we aim for relaxed security notions where the leakage-functions and/or the inputs to the primitive are chosen non-adaptively. For example, we show that a three round Feistel network instantiated with a leakage resilient PRF yields a leakage resilient PRP if the inputs are chosen non-adaptively (This complements the result of Dodis and Pietrzak [CRYPTO’10] who show that if a adaptive queries are allowed, a superlogarithmic number of rounds is necessary.) We also show that a minor variation of the classical GGM construction gives a leakage resilient PRF if both, the leakage-function and the inputs, are chosen non-adaptively.}, author = {Faust, Sebastian and Pietrzak, Krzysztof Z and Schipper, Joachim}, booktitle = { Conference proceedings CHES 2012}, location = {Leuven, Belgium}, pages = {213 -- 232}, publisher = {Springer}, title = {{Practical leakage-resilient symmetric cryptography}}, doi = {10.1007/978-3-642-33027-8_13}, volume = {7428}, year = {2012}, } @inproceedings{2049, abstract = {We propose a new authentication protocol that is provably secure based on a ring variant of the learning parity with noise (LPN) problem. The protocol follows the design principle of the LPN-based protocol from Eurocrypt’11 (Kiltz et al.), and like it, is a two round protocol secure against active attacks. Moreover, our protocol has small communication complexity and a very small footprint which makes it applicable in scenarios that involve low-cost, resource-constrained devices. Performance-wise, our protocol is more efficient than previous LPN-based schemes, such as the many variants of the Hopper-Blum (HB) protocol and the aforementioned protocol from Eurocrypt’11. Our implementation results show that it is even comparable to the standard challenge-and-response protocols based on the AES block-cipher. Our basic protocol is roughly 20 times slower than AES, but with the advantage of having 10 times smaller code size. Furthermore, if a few hundred bytes of non-volatile memory are available to allow the storage of some off-line pre-computations, then the online phase of our protocols is only twice as slow as AES. }, author = {Heyse, Stefan and Kiltz, Eike and Lyubashevsky, Vadim and Paar, Christof and Pietrzak, Krzysztof Z}, booktitle = { Conference proceedings FSE 2012}, location = {Washington, DC, USA}, pages = {346 -- 365}, publisher = {Springer}, title = {{Lapin: An efficient authentication protocol based on ring-LPN}}, doi = {10.1007/978-3-642-34047-5_20}, volume = {7549}, year = {2012}, } @article{2125, abstract = {We consider a class of stochastic PDEs of Burgers type in spatial dimension 1, driven by space–time white noise. Even though it is well known that these equations are well posed, it turns out that if one performs a spatial discretization of the nonlinearity in the “wrong” way, then the sequence of approximate equations does converge to a limit, but this limit exhibits an additional correction term. This correction term is proportional to the local quadratic cross-variation (in space) of the gradient of the conserved quantity with the solution itself. This can be understood as a consequence of the fact that for any fixed time, the law of the solution is locally equivalent to Wiener measure, where space plays the role of time. In this sense, the correction term is similar to the usual Itô–Stratonovich correction term that arises when one considers different temporal discretizations of stochastic ODEs.}, author = {Hairer, Martin M and Jan Maas}, journal = {Annals of Probability}, number = {4}, pages = {1675 -- 1714}, publisher = {Institute of Mathematical Statistics}, title = {{A spatial version of the Itô-Stratonovich correction}}, doi = {10.1214/11-AOP662}, volume = {40}, year = {2012}, } @article{2127, abstract = {We study a new notion of Ricci curvature that applies to Markov chains on discrete spaces. This notion relies on geodesic convexity of the entropy and is analogous to the one introduced by Lott, Sturm, and Villani for geodesic measure spaces. In order to apply to the discrete setting, the role of the Wasserstein metric is taken over by a different metric, having the property that continuous time Markov chains are gradient flows of the entropy. Using this notion of Ricci curvature we prove discrete analogues of fundamental results by Bakry–Émery and Otto–Villani. Further, we show that Ricci curvature bounds are preserved under tensorisation. As a special case we obtain the sharp Ricci curvature lower bound for the discrete hypercube.}, author = {Erbar, Matthias and Jan Maas}, journal = {Archive for Rational Mechanics and Analysis}, number = {3}, pages = {997 -- 1038}, publisher = {Springer}, title = {{Ricci curvature of finite Markov chains via convexity of the entropy}}, doi = {10.1007/s00205-012-0554-z}, volume = {206}, year = {2012}, } @article{2128, abstract = {We introduce a technique for handling Whitney decompositions in Gaussian harmonic analysis and apply it to the study of Gaussian analogues of the classical tent spaces T 1,q of Coifman–Meyer–Stein.}, author = {Jan Maas and van Neerven, Jan M and Portal, Pierre}, journal = {Arkiv för Matematik}, number = {2}, pages = {379 -- 395}, publisher = {Springer}, title = {{Whitney coverings and the tent spaces T 1,q (γ) for the Gaussian measure}}, doi = {10.1007/s11512-010-0143-z}, volume = {50}, year = {2012}, } @article{2201, abstract = {We study the growth dynamics of ordered structures of strongly interacting polar molecules in optical lattices. Using a dipole blockade of microwave excitations, we map the system onto an interacting spin-1/2 model possessing ground states with crystalline order, and describe a way to prepare these states by nonadiabatically driving the transitions between molecular rotational levels. The proposed technique bypasses the need to cross a phase transition and allows for the creation of ordered domains of considerably larger size compared to approaches relying on adiabatic preparation.}, author = {Lemeshko, Mikhail and Krems, Roman and Weimer, Hendrik}, journal = {Physical Review Letters}, number = {3}, publisher = {American Physical Society}, title = {{Nonadiabatic preparation of spin crystals with ultracold polar molecules}}, doi = {10.1103/PhysRevLett.109.035301}, volume = {109}, year = {2012}, } @article{2202, abstract = {We propose a method for sensitive parallel detection of low-frequency electromagnetic fields based on the fine structure interactions in paramagnetic polar molecules. Compared to the recently implemented scheme employing ultracold 87Rb atoms by Böhi, the technique based on molecules offers a 100-fold higher sensitivity, the possibility to measure both the electric and magnetic field components, and a probe of a wide range of frequencies from the dc limit to the THz regime.}, author = {Alyabyshev, Sergey V and Mikhail Lemeshko and Krems, Roman V}, journal = {Physical Review A - Atomic, Molecular, and Optical Physics}, number = {1}, publisher = {American Physical Society}, title = {{Sensitive imaging of electromagnetic fields with paramagnetic polar molecules}}, doi = {10.1103/PhysRevA.86.013409}, volume = {86}, year = {2012}, } @article{2203, abstract = {We show that the electric dipole-dipole interaction between a pair of polar molecules undergoes an all-out transformation when superimposed by a far-off-resonant optical field. The combined interaction potential becomes tunable by variation of wavelength, polarisation and intensity of the optical field and its dependence on the intermolecular separation exhibits a crossover from an inverse-power to an oscillating behaviour. The ability thereby offered to control molecular interactions opens up avenues toward the creation and manipulation of novel phases of ultracold polar gases among whose characteristics is a long-range entanglement of the dipoles' mutual orientation. We devised an accurate analytic model of such optical-field-dressed dipole-dipole interaction potentials, which enables a straightforward access to the optical-field parameters required for the design of intermolecular interactions in the laboratory.}, author = {Mikhail Lemeshko and Friedrich, Břetislav}, journal = {Molecular Physics}, number = {15-16}, pages = {1873 -- 1881}, publisher = {Taylor & Francis}, title = {{Interaction between polar molecules subject to a far-off-resonant optical field: Entangled dipoles up- or down-holding each other}}, doi = {10.1080/00268976.2012.689868}, volume = {110}, year = {2012}, } @article{2263, abstract = {Nestin-cre transgenic mice have been widely used to direct recombination to neural stem cells (NSCs) and intermediate neural progenitor cells (NPCs). Here we report that a readily utilized, and the only commercially available, Nestin-cre line is insufficient for directing recombination in early embryonic NSCs and NPCs. Analysis of recombination efficiency in multiple cre-dependent reporters and a genetic mosaic line revealed consistent temporal and spatial patterns of recombination in NSCs and NPCs. For comparison we utilized a knock-in Emx1cre line and found robust recombination in NSCs and NPCs in ventricular and subventricular zones of the cerebral cortices as early as embryonic day 12.5. In addition we found that the rate of Nestin-cre driven recombination only reaches sufficiently high levels in NSCs and NPCs during late embryonic and early postnatal periods. These findings are important when commercially available cre lines are considered for directing recombination to embryonic NSCs and NPCs.}, author = {Liang, Huixuan and Hippenmeyer, Simon and Ghashghaei, H.}, journal = {Biology open}, number = {12}, pages = {1200 -- 1203}, publisher = {The Company of Biologists}, title = {{A Nestin-cre transgenic mouse is insufficient for recombination in early embryonic neural progenitors}}, doi = {10.1242/bio.20122287}, volume = {1}, year = {2012}, } @inproceedings{2267, abstract = {Capturing real-world objects with laser-scanning technology has become an everyday task. Recently, the acquisition of dynamic scenes at interactive frame rates has become feasible. A high-quality visualization of the resulting point cloud stream would require a per-frame reconstruction of object surfaces. Unfortunately, reconstruction computations are still too time-consuming to be applied interactively. In this paper we present a local surface reconstruction and visualization technique that provides interactive feedback for reasonably sized point clouds, while achieving high image quality. Our method is performed entirely on the GPU and in screen pace, exploiting the efficiency of the common rasterization pipeline. The approach is very general, as no assumption is made about point connectivity or sampling density. This naturally allows combining the outputs of multiple scanners in a single visualization, which is useful for many virtual and augmented reality applications. }, author = {Preiner, Reinhold and Jeschke, Stefan and Wimmer, Michael}, location = {Calgari, Italy}, pages = {139 -- 148}, publisher = {Eurographics Association}, title = {{Auto splats: Dynamic point cloud visualization on the GPU}}, doi = {10.2312/EGPGV/EGPGV12/139-148}, year = {2012}, } @inproceedings{2268, abstract = {This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyhedra. Our framework allows the exact evaluation of the convolution integral with a linear function defined on the polytopes. The filter is a spherically symmetric polynomial of any order, supporting approximations to refined variants such as the Mitchell-Netravali filter family. This enables high-quality rasterization of triangles and tetrahedra with linearly interpolated vertex values to regular and non-regular grids. A closed form solution of the convolution is presented and an efficient implementation on the GPU using DirectX and CUDA C is described. }, author = {Thomas Auzinger and Guthe, Michael and Stefan Jeschke}, number = {121}, pages = {335 -- 344}, publisher = {Wiley-Blackwell}, title = {{Analytic anti-aliasing of linear functions on polytopes}}, doi = {http://dx.doi.org/10.1111/j.1467-8659.2012.03012.x}, volume = {31}, year = {2012}, } @inproceedings{2316, abstract = {We summarize our recent results on the ground state energy of multi-polaron systems. In particular, we discuss stability and existence of the thermodynamic limit, and we discuss the absence of binding in the case of large Coulomb repulsion and the corresponding binding-unbinding transition. We also consider the Pekar-Tomasevich approximation to the ground state energy and we study radial symmetry of the ground state density. }, author = {Frank, Rupert L and Lieb, Élliott H and Robert Seiringer and Thomas, Lawrence E}, pages = {477 -- 485}, publisher = {World Scientific Publishing}, title = {{Ground state properties of multi-polaron systems}}, doi = {10.1142/9789814449243_0045}, year = {2012}, }