Holographic Butterfly Effect at Quantum Critical Points

When the Lyapunov exponent $\lambda_L$ in a quantum chaotic system saturates the bound $\lambda_L\leqslant 2\pi k_BT$, it is proposed that this system has a holographic dual described by a gravity theory. In particular, the butterfly effect as a prominent phenomenon of chaos can ubiquitously exist in a black hole system characterized by a shockwave solution near the horizon. In this paper we propose that the butterfly velocity can be used to diagnose quantum phase transition (QPT) in holographic theories. We provide evidences for this proposal with an anisotropic holographic model exhibiting metal-insulator transitions (MIT), in which the derivatives of the butterfly velocity with respect to system parameters characterizes quantum critical points (QCP) with local extremes in zero temperature limit. We also point out that this proposal can be tested by experiments in the light of recent progress on the measurement of out-of-time-order correlation function (OTOC).Comment: 7 figures, 15 page

A novel scalable manufacturing platform for T-cell activation and expansion in adoptive T-cell therapy

Adoptive T cell therapy (ACT) is growing rapidly, representing the revolution in cancer treatment. However, the current manufacturing platforms are largely based on magnetic microbeads surface coated with agonist antibodies to T-cell receptors CD3 and CD28. These manufacturing platforms use expensive reagents including the viral transduction vectors, and also require multiple discrete stages and open processes with significant human interaction, contributing to the high-cost for cGMP manufacturing of these therapies. We developed a single-use, beads-free bioreactor system (Figure 1a), which provides a closed-loop T-cell activation and expansion. The perfusion-based platform also facilitates the development of the bioreactor system into a fully automated, turn-key system used in both centralized and decentralized (e.g., hospitals) manufacturing settings. The bioreactor has a unique internal structure (Figure 1b), formed by a large number of interconnected hollow spheres tightly packed in a 3D space, which yields large surface areas to increase the reactivity between the bioreactor and the T cells flowing through the bioreactor. The surfaces of the bioreactor are coated with anti-CD3 and CD28 antibodies to mimic the antigens for T activation and expansion. The feasibility of using the perfusion-based bioreactor for T-cell activation and expansion is demonstrated in Figure 2. Briefly, 20x106 PBMCs were seeded into the bioreactor system and perfused for two days during the T-cell activation phase, with the medium containing no cytokine IL2. After two-day of activation, human IL-2 was added to the system so that the total IL-2 concentration was 20 IU/mL. Then the T-cell expansion phase was carried out for three-days. On Day 5, T cells were achieved a three-time expansion after activation, which is similar to the magnetic beads-based system. However, the perfusion based bioreactor has the potential to offer multiple advantages over the current beads-based system as discussed above

Holographic Metal-Insulator Transition in Higher Derivative Gravity

We introduce a Weyl term into the Einstein-Maxwell-Axion theory in four dimensional spacetime. Up to the first order of the Weyl coupling parameter $\gamma$, we construct charged black brane solutions without translational invariance in a perturbative manner. Among all the holographic frameworks involving higher derivative gravity, we are the first to obtain metal-insulator transitions (MIT) when varying the system parameters at zero temperature. Furthermore, we study the holographic entanglement entropy (HEE) of strip geometry in this model and find that the second order derivative of HEE with respect to the axion parameter exhibits maximization behavior near quantum critical points (QCPs) of MIT. It testifies the conjecture in 1502.03661 and 1604.04857 that HEE itself or its derivatives can be used to diagnose quantum phase transition (QPT).Comment: 20 pages, 4 figures; typo corrected, added 3 references; minor revisio