Keep it SMPL: Automatic Estimation of 3D Human Pose and Shape from a Single Image

We describe the first method to automatically estimate the 3D pose of the human body as well as its 3D shape from a single unconstrained image. We estimate a full 3D mesh and show that 2D joints alone carry a surprising amount of information about body shape. The problem is challenging because of the complexity of the human body, articulation, occlusion, clothing, lighting, and the inherent ambiguity in inferring 3D from 2D. To solve this, we first use a recently published CNN-based method, DeepCut, to predict (bottom-up) the 2D body joint locations. We then fit (top-down) a recently published statistical body shape model, called SMPL, to the 2D joints. We do so by minimizing an objective function that penalizes the error between the projected 3D model joints and detected 2D joints. Because SMPL captures correlations in human shape across the population, we are able to robustly fit it to very little data. We further leverage the 3D model to prevent solutions that cause interpenetration. We evaluate our method, SMPLify, on the Leeds Sports, HumanEva, and Human3.6M datasets, showing superior pose accuracy with respect to the state of the art.Comment: To appear in ECCV 201

Multiwavelength observations of Mkn 501 during the 1997 high state

During the observation period 1997, the nearby Blazar Mkn 501 showed extremely strong emission and high variability. We examine multiwavelength aspects of this event using radio, optical, soft and hard X-ray and TeV data. We concentrate on the medium-timescale variability of the broadband spectra, averaged over weekly intervals. We confirm the previously found correlation between soft and hard X-ray emission and the emission at TeV energies, while the source shows only minor variability at radio and optical wavelengths. The non-linear correlation between hard X-ray and TeV fluxes is consistent with a simple analytic estimate based on an SSC model in which Klein-Nishina effects are important for the highest-energy electrons in the jet, and flux variations are caused by variations of the electron density and/or the spectral index of the electron injection spectrum. The time-averaged spectra are fitted with a Synchrotron Self-Compton (SSC) dominated leptonic jet model, using the full Klein-Nishina cross section and following the self-consistent evolution of relativistic particles along the jet, accounting for gamma-gamma absorption and pair production within the source as well as due to the intergalactic infrared background radiation. The contribution from external inverse-Compton scattering is tightly constrained by the low maximum EGRET flux and found to be negligible at TeV energies. We find that high levels of the X-ray and TeV fluxes can be explained by a hardening of the energy spectra of electrons injected at the base of the jet, in remarkable contrast to the trend found for gamma-ray flares of the flat-spectrum radio quasar PKS 0528+134.Comment: accepted for publication in ApJ, 31 pages, 11 figure

Neutrinos produced by ultrahigh-energy photons at high red shift

Some of the proposed explanations for the origin of ultrahigh-energy cosmic rays invoke new sources of energetic photons (e.g., topological defects, relic particles, etc.). At high red shift, when the cosmic microwave background has a higher temperature but the radio background is low, the ultrahigh-energy photons can generate neutrinos through pair-production of muons and pions. Neutrinos produced at high red shift by slowly evolving sources can be detected. Rapidly evolving sources of photons can be ruled out based on the existing upper limit on the neutrino flux.Comment: 4 pages, revtex; to appear in Phys. Rev. Let

Monocular Expressive Body Regression through Body-Driven Attention

To understand how people look, interact, or perform tasks, we need to quickly and accurately capture their 3D body, face, and hands together from an RGB image. Most existing methods focus only on parts of the body. A few recent approaches reconstruct full expressive 3D humans from images using 3D body models that include the face and hands. These methods are optimization-based and thus slow, prone to local optima, and require 2D keypoints as input. We address these limitations by introducing ExPose (EXpressive POse and Shape rEgression), which directly regresses the body, face, and hands, in SMPL-X format, from an RGB image. This is a hard problem due to the high dimensionality of the body and the lack of expressive training data. Additionally, hands and faces are much smaller than the body, occupying very few image pixels. This makes hand and face estimation hard when body images are downscaled for neural networks. We make three main contributions. First, we account for the lack of training data by curating a dataset of SMPL-X fits on in-the-wild images. Second, we observe that body estimation localizes the face and hands reasonably well. We introduce body-driven attention for face and hand regions in the original image to extract higher-resolution crops that are fed to dedicated refinement modules. Third, these modules exploit part-specific knowledge from existing face- and hand-only datasets. ExPose estimates expressive 3D humans more accurately than existing optimization methods at a small fraction of the computational cost. Our data, model and code are available for research at https://expose.is.tue.mpg.de .Comment: Accepted in ECCV'20. Project page: http://expose.is.tue.mpg.d

Ultra-High Energy Gamma Rays in Geomagnetic Field and Atmosphere

The nature and origin of ultra-high energy (UHE: reffering to > 10^19 eV) cosmic rays are great mysteries in modern astrophysics. The current theories for their explanation include the so-called "top-down" decay scenarios whose main signature is a large ratio of UHE gamma rays to protons. Important step in determining the primary composition at ultra-high energies is the study of air shower development. UHE gamma ray induced showers are affected by the Landau-Pomeranchuk-Migdal (LPM) effect and the geomagnetic cascading process. In this work extensive simulations have been carried out to study the characteristics of air showers from UHE gamma rays. At energies above several times 10^19 eV the shower is affected by geomagnetic cascading rather than by the LPM effect. The properties of the longitudinal development such as average depth of the shower maximum or its fluctuations depend strongly on both primary energy and incident direction. This feature may provide a possible evidence of the UHE gamma ray presence by fluorescence detectors.Comment: 27 pages, 12 figures, submitted to Phys.Rev.

Inclusive J/ψ production at mid-rapidity in pp collisions at √s = 5.02 TeV

Inclusive J/ψ production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of s = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity (|y| < 0.9) in the dielectron decay channel down to zero transverse momentum pT, using a data sample corresponding to an integrated luminosity of Lint = 19.4 ± 0.4 nb−1. The measured pT-integrated inclusive J/ψ production cross sec- tion is dσ/dy = 5.64 ± 0.22(stat.) ± 0.33(syst.) ± 0.12(lumi.) μb. The pT-differential cross section d2σ/dpTdy is measured in the pT range 0–10 GeV/c and compared with state-of- the-art QCD calculations. The J/ψ 〈pT〉 and 〈pT2〉 are extracted and compared with results obtained at other collision energies. [Figure not available: see fulltext.]

Measurement of Λ (1520) production in pp collisions at √s=7TeV and p–Pb collisions at √sNN=5.02TeV

The production of the Λ (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s=7TeV and in p–Pb collisions at sNN=5.02TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ (1520) → pK - and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, KS0, p, Λ) describes the shape of the Λ (1520) transverse momentum distribution up to 3.5GeV/c in p–Pb collisions. In the framework of this model, this observation suggests that the Λ (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ (1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the Λ (1520) yield

Measurement of charged jet cross section in pp collisions at s =5.02 TeV

The cross section of jets reconstructed from charged particles is measured in the transverse momentum range of