Chiral phase transition and meson spectrum in improved soft-wall AdS/QCD

We investigate in detail the chiral thermal transition of QCD in an improved soft-wall AdS/QCD model with a simply modified 5D conformal mass of the bulk scalar field. We also present a calculation in this model for the light meson spectra and other low-energy characteristic quantities including the pion form factor, the pi-rho coupling constant and the decay constants of pi, rho, a_1, which are shown to result in a good agreement with experimental data except for the pion decay constant. The thermal behavior of chiral condensate is studied. It is found that such a simply improved soft-wall model incorporates the crossover behavior of chiral thermal transition indicated by lattice simulations. The expected chiral transition temperature can be obtained

Nearly Optimal Stochastic Approximation for Online Principal Subspace Estimation

Processing streaming data as they arrive is often necessary for high dimensional data analysis. In this paper, we analyse the convergence of a subspace online PCA iteration, as a followup of the recent work of Li, Wang, Liu, and Zhang [Math. Program., Ser. B, DOI 10.1007/s10107-017-1182-z] who considered the case for the most significant principal component only, i.e., a single vector. Under the sub-Gaussian assumption, we obtain a finite-sample error bound that closely matches the minimax information lower bound of Vu and Lei [Ann. Statist. 41:6 (2013), 2905-2947].Comment: 37 page

A consistent analysis on QCD phase diagram and meson spectra in the improved soft-wall AdS/QCD

We present a consistent analysis on QCD phase diagram and meson spectra based on the improved soft-wall AdS/QCD. The equations of motion for the octet pseudoscalar, vector and axial-vector mesons with $2+1$ flavors are derived to calculate the octet meson spectra and relevant decay constants, by which the model parameters are determined. The chemical potential effects on chiral thermal transition are investigated, which enables us to obtain the QCD phase diagram in the $\mu-T$ plane. It is shown that the critical end point (CEP) linking the crossover transition with the first-order phase transition still exists and locates at $(\mu_B, T_c) \simeq (390 MeV, 145 MeV)$. The crossover line and the location of CEP resulted from the model agree with both the lattice result and the experimental analysis from relativistic heavy-ion collisions. We find that the improved soft-wall AdS/QCD model can provide a consistent description for both the chiral phase diagram and the main properties of low-energy hadron physics in the $2+1$ flavor case

Adaptive Sparse Pairwise Loss for Object Re-Identification

Object re-identification (ReID) aims to find instances with the same identity as the given probe from a large gallery. Pairwise losses play an important role in training a strong ReID network. Existing pairwise losses densely exploit each instance as an anchor and sample its triplets in a mini-batch. This dense sampling mechanism inevitably introduces positive pairs that share few visual similarities, which can be harmful to the training. To address this problem, we propose a novel loss paradigm termed Sparse Pairwise (SP) loss that only leverages few appropriate pairs for each class in a mini-batch, and empirically demonstrate that it is sufficient for the ReID tasks. Based on the proposed loss framework, we propose an adaptive positive mining strategy that can dynamically adapt to diverse intra-class variations. Extensive experiments show that SP loss and its adaptive variant AdaSP loss outperform other pairwise losses, and achieve state-of-the-art performance across several ReID benchmarks. Code is available at https://github.com/Astaxanthin/AdaSP.Comment: Accepted by CVPR 202