TrajectoryFormer: 3D Object Tracking Transformer with Predictive Trajectory Hypotheses

3D multi-object tracking (MOT) is vital for many applications including autonomous driving vehicles and service robots. With the commonly used tracking-by-detection paradigm, 3D MOT has made important progress in recent years. However, these methods only use the detection boxes of the current frame to obtain trajectory-box association results, which makes it impossible for the tracker to recover objects missed by the detector. In this paper, we present TrajectoryFormer, a novel point-cloud-based 3D MOT framework. To recover the missed object by detector, we generates multiple trajectory hypotheses with hybrid candidate boxes, including temporally predicted boxes and current-frame detection boxes, for trajectory-box association. The predicted boxes can propagate object's history trajectory information to the current frame and thus the network can tolerate short-term miss detection of the tracked objects. We combine long-term object motion feature and short-term object appearance feature to create per-hypothesis feature embedding, which reduces the computational overhead for spatial-temporal encoding. Additionally, we introduce a Global-Local Interaction Module to conduct information interaction among all hypotheses and models their spatial relations, leading to accurate estimation of hypotheses. Our TrajectoryFormer achieves state-of-the-art performance on the Waymo 3D MOT benchmarks.Comment: 10 pages, 3 figure

Neutrons and antiprotons in ultrahigh energy cosmic rays

The neutron fraction in the very high energy cosmic rays near the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy is analyzed by taking into account the time dilation effect of the neutron decays and also the pion photoproduction behaviors above the GZK cutoff. We predict a non-trivial neutron fraction above the GZK cutoff and a negligibly small neutron fraction below. However, there should be a large antiproton fraction in the high energy cosmic rays below the GZK cutoff in several existing models for the observed cosmic-ray events above and near the GZK cutoff. Such a large antiproton fraction can manifest itself by the muon charge ratio $\mu^+/\mu^-$ in the collisions of the primary nucleon cosmic rays with the atmosphere, if there is no neutron contribution. We suggest to use the muon charge ratio as one of the information to detect the composition of the primary cosmic rays near or below the GZK cutoff.Comment: 5 LaTex page

The cos 2 phi asymmetry of Drell-Yan and J/psi production in unpolarized ppbar scattering

We investigate the cos 2 phi azimuthal asymmetry in Drell--Yan and J/psi production from unpolarized ppbar scattering at GSI-HESR energies. The contribution to this asymmetry arising from the leading-twist Boer-Mulders function h_1^perp(x, k_T^2), which describes a correlation between the transverse momentum and the transverse spin of quarks in an unpolarized hadron, is explicitly evaluated, and predictions for the GSI-HESR kinematic regime are presented. We show that the cos 2 phi asymmetry is quite sizable both on the J/psi peak and in the Drell-Yan continuum region. Therefore these processes may offer an experimentally viable access to the Boer-Mulders function in the early unpolarized stage of GSI experiments.Comment: 5 pages, 3 figures, to be published in Eur. Phys.

Spectrum sharing on interference channels with a cognitive relay

\u3cp\u3eWe consider a cognitive spectrum sharing system on an interference channel with a cognitive relay (IFC-CR) assisting both the primary and secondary users in forwarding their messages to the respective destination nodes. The CR uses a successive interference cancelation scheme to decode the primary and secondary messages after a first transmission phase. The CR performs power allocation and in the second transmission phase, forwards a linear weighted combination of the decoded primary and secondary messages. We demonstrate that with a properly designed power allocation, secondary spectrum sharing is achieved and at the same time a better performance can be achieved for the primary user than the case without spectrum sharing. The proposed spectrum sharing scheme further does not require any non-causal knowledge of the primary message at the secondary user or at the CR.\u3c/p\u3