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We study the spin alignment of neutral rho mesons in a pion gas using spin kinetic or Boltzmann equations. The $\rho\pi\pi$ coupling is given by the chiral effective theory. The collision terms at the leading and next-to-leading order in spin Boltzmann equations are derived. The evolution of the spin density matrix of the neutral rho meson is simulated with different initial conditions. The numerical results show that the interaction of pions and neutral rho mesons creates very small spin alignment in the central rapidity region if there is no rho meson in the system at the initial time. Such a small spin alignment in the central rapidity region will decay rapidly toward zero in later time. If there are rho mesons with a sizable spin alignment at the initial time the spin alignment will also decrease rapidly. We also considered the effect on $\rho_{00}$ from the elliptic flow of pions in the blast wave model. With vanishing spin alignment at the initial time, the deviation of $\rho_{00}$ from 1/3 is positive but very small., Comment: RevTex 4, 17 pages, 12 figures

We give a brief overview on global polarization and spin alignment in heavy ion collisions. The current theoretical understandings on global polarization of hyperons and the global spin alignment of vector mesons are summarized., Comment: 10 pages, 2 figures, Proceeding for SPIN 2023

We present a calculation of the spin alignment for unflavored vector mesons in thermalized quark-gluon plasma based on the Kubo formula in linear response theory. This is achieved by expanding the system to the first order of the coupling constant and the spatial gradient. The effect strongly relies on the vector meson's spectral functions which are determined by the interaction and medium properties. The spectral functions are calculated for the one-quark-loop self-energy with meson-quark interaction. The numerical results show that the correction to the spin alignment from the thermal shear tensor is of the order $10^{-4}\sim10^{-5}$ for the chosen values of quark-meson coupling constant, if the magnitude of thermal shear tensor is $10^{-2}$., Comment: 22 pages, 5 figures

Deep learning based video frame interpolation (VIF) method, aiming to synthesis the intermediate frames to enhance video quality, have been highly developed in the past few years. This paper investigates the adversarial robustness of VIF models. We apply adversarial attacks to VIF models and find that the VIF models are very vulnerable to adversarial examples. To improve attack efficiency, we suggest to make full use of the property of video frame interpolation task. The intuition is that the gap between adjacent frames would be small, leading to the corresponding adversarial perturbations being similar as well. Then we propose a novel attack method named Inter-frame Accelerate Attack (IAA) that initializes the perturbation as the perturbation for the previous adjacent frame and reduces the number of attack iterations. It is shown that our method can improve attack efficiency greatly while achieving comparable attack performance with traditional methods. Besides, we also extend our method to video recognition models which are higher level vision tasks and achieves great attack efficiency.

We derive the spin Boltzmann equations for spin-1/2 fermions in a non-relativistic model with four-fermion contact interaction which conserves spin degrees of freedom. A great advantage of the model is that the spin matrix elements in collision terms can be completely worked out and be put into such a compact form that one can clearly see how spins are coupled in particle scatterings. A semi-classical expansion in the Planck constant has been made and the on-shell part of the spin Boltzmann equation up to the next-to-leading order is derived. At the leading order the equilibrium spin distribution can be obtained from the vanishing of the collision term for the spin density. The spin chemical potential emerges as a natural consequence of spin conservation. The off-shell part of the spin Boltzmann equation is also discussed. The work can be extended to more sophisticated interaction such as nuclear force in order to apply to spin polarization phenomena in heavy-ion collisions at low energies., Comment: RevTex 4, 15 pages, 1 figure

We revisit Minkowski's lost legacy on relativistic electromagnetism in order to resolve long-standing puzzles over the charge distribution of relativistic systems like hadrons. Hadrons are unique relativistic electromagnetic systems characterized by their comparable size and Compton wavelength $r_h \sim \lambda_C$. As such, it was recently realized that the traditional Sachs definition of the charge distribution based on a non-relativistic formula is invalid. We explain that this is the same problem pursued by Lorentz, Einstein and others, on the electromagnetism of a moving body. We show how various charge distributions proposed in hadronic physics naturally emerge as the multipole moment densities in the macroscopic theory of relativistic electromagnetism., Comment: 7 pages, 2 figures; published on Physics Letters B

Previous studies have shown that for the Supernova Legacy Survey three-year (SNLS3) data there is strong evidence for the redshift-evolution of color-luminosity parameter $\beta$ of type Ia supernovae (SN Ia). In this paper, we explore the effects of varying $\beta$ on the cosmological constraints of holographic dark energy (HDE) model. In addition to the SNLS3 data, we also use Planck distance prior data of cosmic microwave background (CMB), as well as galaxy clustering (GC) data extracted from Sloan Digital Sky Survey (SDSS) data release 7 and Baryon Oscillation Spectroscopic Survey (BOSS). We find that, for the both cases of using SN data alone and using SN+CMB+GC data, involving an additional parameter of $\beta$ can reduce $\chi^2$ by $\sim$ 36; this shows that $\beta$ deviates from a constant at 6$\sigma$ confidence levels. Adopting SN+CMB+GC data, we find that compared to the constant $\beta$ case, varying $\beta$ yields a larger fractional matter density $\Omega_{m0}$ and a smaller reduced Hubble constant $h$; moreover, varying $\beta$ significantly increases the value of HDE model parameter $c$, leading to $c\approx 0.8$, consistent with the constraint results obtained before Planck. These results indicate that the evolution of $\beta$ should be taken into account seriously in the cosmological fits. In addition, we find that relative to the differences between the constant $\beta$ and varying $\beta(z)$ cases, the effects of different light-curve fitters on parameter estimation are very small., Comment: 12 pages, 8 figures. arXiv admin note: substantial text overlap with arXiv:1310.6109; and text overlap with arXiv:1109.3172 by other authors