TY - JOUR
AB - Photorealistic editing of head portraits is a challenging task as humans are very sensitive to inconsistencies in faces. We present an approach for high-quality intuitive editing of the camera viewpoint and scene illumination (parameterised with an environment map) in a portrait image. This requires our method to capture and control the full reflectance field of the person in the image. Most editing approaches rely on supervised learning using training data captured with setups such as light and camera stages. Such datasets are expensive to acquire, not readily available and do not capture all the rich variations of in-the-wild portrait images. In addition, most supervised approaches only focus on relighting, and do not allow camera viewpoint editing. Thus, they only capture and control a subset of the reflectance field. Recently, portrait editing has been demonstrated by operating in the generative model space of StyleGAN. While such approaches do not require direct supervision, there is a significant loss of quality when compared to the supervised approaches. In this paper, we present a method which learns from limited supervised training data. The training images only include people in a fixed neutral expression with eyes closed, without much hair or background variations. Each person is captured under 150 one-light-at-a-time conditions and under 8 camera poses. Instead of training directly in the image space, we design a supervised problem which learns transformations in the latent space of StyleGAN. This combines the best of supervised learning and generative adversarial modeling. We show that the StyleGAN prior allows for generalisation to different expressions, hairstyles and backgrounds. This produces high-quality photorealistic results for in-the-wild images and significantly outperforms existing methods. Our approach can edit the illumination and pose simultaneously, and runs at interactive rates.
AU - Mallikarjun, B. R.
AU - Tewari, Ayush
AU - Dib, Abdallah
AU - Weyrich, Tim
AU - Bickel, Bernd
AU - Seidel, Hans Peter
AU - Pfister, Hanspeter
AU - Matusik, Wojciech
AU - Chevallier, Louis
AU - Elgharib, Mohamed A.
AU - Theobalt, Christian
ID - 9819
IS - 4
JF - ACM Transactions on Graphics
SN - 07300301
TI - PhotoApp: Photorealistic appearance editing of head portraits
VL - 40
ER -
TY - JOUR
AB - Aims: Mass antigen testing programs have been challenged because of an alleged insufficient specificity, leading to a large number of false positives. The objective of this study is to derive a lower bound of the specificity of the SD Biosensor Standard Q Ag-Test in large scale practical use.
Methods: Based on county data from the nationwide tests for SARS-CoV-2 in Slovakia between 31.10.–1.11. 2020 we calculate a lower confidence bound for the specificity. As positive test results were not systematically verified by PCR tests, we base the lower bound on a worst case assumption, assuming all positives to be false positives.
Results: 3,625,332 persons from 79 counties were tested. The lowest positivity rate was observed in the county of Rožňava where 100 out of 34307 (0.29%) tests were positive. This implies a test specificity of at least 99.6% (97.5% one-sided lower confidence bound, adjusted for multiplicity).
Conclusion: The obtained lower bound suggests a higher specificity compared to earlier studies in spite of the underlying worst case assumption and the application in a mass testing setting. The actual specificity is expected to exceed 99.6% if the prevalence in the respective regions was non-negligible at the time of testing. To our knowledge, this estimate constitutes the first bound obtained from large scale practical use of an antigen test.
AU - Hledik, Michal
AU - Polechova, Jitka
AU - Beiglböck, Mathias
AU - Herdina, Anna Nele
AU - Strassl, Robert
AU - Posch, Martin
ID - 9816
IS - 7
JF - PLoS ONE
TI - Analysis of the specificity of a COVID-19 antigen test in the Slovak mass testing program
VL - 16
ER -
TY - JOUR
AB - We study an effective one-dimensional quantum model that includes friction and spin-orbit coupling (SOC), and show that the model exhibits spin polarization when both terms are finite. Most important, strong spin polarization can be observed even for moderate SOC, provided that the friction is strong. Our findings might help to explain the pronounced effect of chirality on spin distribution and transport in chiral molecules. In particular, our model implies static magnetic properties of a chiral molecule, which lead to Shiba-like states when a molecule is placed on a superconductor, in accordance with recent experimental data.
AU - Volosniev, Artem
AU - Alpern, Hen
AU - Paltiel, Yossi
AU - Millo, Oded
AU - Lemeshko, Mikhail
AU - Ghazaryan, Areg
ID - 9770
IS - 2
JF - Physical Review B
SN - 2469-9950
TI - Interplay between friction and spin-orbit coupling as a source of spin polarization
VL - 104
ER -
TY - JOUR
AB - We extend the notion of the minimal volume ellipsoid containing a convex body in Rd to the setting of logarithmically concave functions. We consider a vast class of logarithmically concave functions whose superlevel sets are concentric ellipsoids. For a fixed function from this class, we consider the set of all its “affine” positions. For any log-concave function f on Rd, we consider functions belonging to this set of “affine” positions, and find the one with the minimal integral under the condition that it is pointwise greater than or equal to f. We study the properties of existence and uniqueness of the solution to this problem. For any s∈[0,+∞), we consider the construction dual to the recently defined John s-function (Ivanov and Naszódi in Functional John ellipsoids. arXiv preprint: arXiv:2006.09934, 2020). We prove that such a construction determines a unique function and call it the Löwner s-function of f. We study the Löwner s-functions as s tends to zero and to infinity. Finally, extending the notion of the outer volume ratio, we define the outer integral ratio of a log-concave function and give an asymptotically tight bound on it.
AU - Ivanov, Grigory
AU - Tsiutsiurupa, Igor
ID - 9548
JF - Journal of Geometric Analysis
SN - 10506926
TI - Functional Löwner ellipsoids
ER -
TY - JOUR
AB - We show that turbulent dynamics that arise in simulations of the three-dimensional Navier--Stokes equations in a triply-periodic domain under sinusoidal forcing can be described as transient visits to the neighborhoods of unstable time-periodic solutions. Based on this description, we reduce the original system with more than 10^5 degrees of freedom to a 17-node Markov chain where each node corresponds to the neighborhood of a periodic orbit. The model accurately reproduces long-term averages of the system's observables as weighted sums over the periodic orbits.
AU - Yalniz, Gökhan
AU - Hof, Björn
AU - Budanur, Nazmi B
ID - 9558
IS - 24
JF - Physical Review Letters
SN - 0031-9007
TI - Coarse graining the state space of a turbulent flow using periodic orbits
VL - 126
ER -
TY - JOUR
AB - Sound propagation is a macroscopic manifestation of the interplay between the equilibrium thermodynamics and the dynamical transport properties of fluids. Here, for a two-dimensional system of ultracold fermions, we calculate the first and second sound velocities across the whole BCS-BEC crossover, and we analyze the system response to an external perturbation. In the low-temperature regime we reproduce the recent measurements [Phys. Rev. Lett. 124, 240403 (2020)] of the first sound velocity, which, due to the decoupling of density and entropy fluctuations, is the sole mode excited by a density probe. Conversely, a heat perturbation excites only the second sound, which, being sensitive to the superfluid depletion, vanishes in the deep BCS regime and jumps discontinuously to zero at the Berezinskii-Kosterlitz-Thouless superfluid transition. A mixing between the modes occurs only in the finite-temperature BEC regime, where our theory converges to the purely bosonic results.
AU - Tononi, A.
AU - Cappellaro, Alberto
AU - Bighin, Giacomo
AU - Salasnich, L.
ID - 9606
IS - 6
JF - Physical Review A
SN - 24699926
TI - Propagation of first and second sound in a two-dimensional Fermi superfluid
VL - 103
ER -
TY - JOUR
AB - We present conductance-matrix measurements in long, three-terminal hybrid superconductor-semiconductor nanowires, and compare with theoretical predictions of a magnetic-field-driven, topological quantum phase transition. By examining the nonlocal conductance, we identify the closure of the excitation gap in the bulk of the semiconductor before the emergence of zero-bias peaks, ruling out spurious gap-closure signatures from localized states. We observe that after the gap closes, nonlocal signals and zero-bias peaks fluctuate strongly at both ends, inconsistent with a simple picture of clean topological superconductivity.
AU - Puglia, Denise
AU - Martinez, E. A.
AU - Ménard, G. C.
AU - Pöschl, A.
AU - Gronin, S.
AU - Gardner, G. C.
AU - Kallaher, R.
AU - Manfra, M. J.
AU - Marcus, C. M.
AU - Higginbotham, Andrew P
AU - Casparis, L.
ID - 9570
IS - 23
JF - Physical Review B
SN - 24699950
TI - Closing of the induced gap in a hybrid superconductor-semiconductor nanowire
VL - 103
ER -
TY - JOUR
AB - The quantum bits (qubits) on which superconducting quantum computers are based have energy scales corresponding to photons with GHz frequencies. The energy of photons in the gigahertz domain is too low to allow transmission through the noisy room-temperature environment, where the signal would be lost in thermal noise. Optical photons, on the other hand, have much higher energies, and signals can be detected using highly efficient single-photon detectors. Transduction from microwave to optical frequencies is therefore a potential enabling technology for quantum devices. However, in such a device the optical pump can be a source of thermal noise and thus degrade the fidelity; the similarity of input microwave state to the output optical state. In order to investigate the magnitude of this effect we model the sub-Kelvin thermal behavior of an electro-optic transducer based on a lithium niobate whispering gallery mode resonator. We find that there is an optimum power level for a continuous pump, whilst pulsed operation of the pump increases the fidelity of the conversion.
AU - Mobassem, Sonia
AU - Lambert, Nicholas J.
AU - Rueda Sanchez, Alfredo R
AU - Fink, Johannes M
AU - Leuchs, Gerd
AU - Schwefel, Harald G.L.
ID - 9815
IS - 4
JF - Quantum Science and Technology
TI - Thermal noise in electro-optic devices at cryogenic temperatures
VL - 6
ER -
TY - GEN
AB - We introduce a hierachy of equivalence relations on the set of separated nets of a given Euclidean space, indexed by concave increasing functions ϕ:(0,∞)→(0,∞). Two separated nets are called ϕ-displacement equivalent if, roughly speaking, there is a bijection between them which, for large radii R, displaces points of norm at most R by something of order at most ϕ(R). We show that the spectrum of ϕ-displacement equivalence spans from the established notion of bounded displacement equivalence, which corresponds to bounded ϕ, to the indiscrete equivalence relation, coresponding to ϕ(R)∈Ω(R), in which all separated nets are equivalent. In between the two ends of this spectrum, the notions of ϕ-displacement equivalence are shown to be pairwise distinct with respect to the asymptotic classes of ϕ(R) for R→∞. We further undertake a comparison of our notion of ϕ-displacement equivalence with previously studied relations on separated nets. Particular attention is given to the interaction of the notions of ϕ-displacement equivalence with that of bilipschitz equivalence.
AU - Dymond, Michael
AU - Kaluza, Vojtech
ID - 9651
T2 - arXiv
TI - Divergence of separated nets with respect to displacement equivalence
ER -
TY - JOUR
AB - A few years ago, flow equations were introduced as a technique for calculating the ground-state energies of cold Bose gases with and without impurities. In this paper, we extend this approach to compute observables other than the energy. As an example, we calculate the densities, and phase fluctuations of one-dimensional Bose gases with one and two impurities. For a single mobile impurity, we use flow equations to validate the mean-field results obtained upon the Lee-Low-Pines transformation. We show that the mean-field approximation is accurate for all values of the boson-impurity interaction strength as long as the phase coherence length is much larger than the healing length of the condensate. For two static impurities, we calculate impurity-impurity interactions induced by the Bose gas. We find that leading order perturbation theory fails when boson-impurity interactions are stronger than boson-boson interactions. The mean-field approximation reproduces the flow equation results for all values of the boson-impurity interaction strength as long as boson-boson interactions are weak.
AU - Brauneis, Fabian
AU - Hammer, Hans-Werner
AU - Lemeshko, Mikhail
AU - Volosniev, Artem
ID - 9769
IS - 1
JF - SciPost Physics
TI - Impurities in a one-dimensional Bose gas: The flow equation approach
VL - 11
ER -