Quasinormal Modes and Hidden Conformal Symmetry of Warped dS3_3 Black Hole

In this paper, we analytically calculate the quasinormal modes of scalar, vector, tensor, and spinor perturbations of the warped dS$_3$ black hole. There are two horizons for the warped dS$_3$ black hole, namely, the black hole horizon $r_b$ and the cosmological horizon $r_c$. In the calculation, we impose the ingoing boundary condition at the black hole horizon and the outgoing boundary condition at the cosmological horizon. We also investigate the hidden conformal symmetry of the warped dS$_3$ black hole in the region between the black hole horizon and the cosmological horizon $r_b<r<r_c$. We use the hidden conformal symmetry to construct the quasinormal modes in an algebraic way and find that the results agree with the analytically ones. It turns out that the frequencies of the quasinormal modes could be identified with the poles in the thermal boundary-boundary correlators.Comment: 26 pages, references added, published versio

The Use of Cellulose Nanofibers in Polymer Matrix Composites via 3D Printing

Filament fused fabrication (FFF) is an extrusion-based 3D printing technology for manufacturing thermoplastic polymers. A major obstacle of 3D printed thermoplastic is the limited crystallinity resulting from a fast quench while material leaving the hot nozzle and solidifying quickly at the low-temperature platform. As a result, the mechanical performances of 3D printed thermoplastic is normally inadequate in comparison with conventionally manufactured ones (e.g., from injection molding). In this work, we developed two strategies for reinforcing and functionalizing 3D printed thermoplastic composites using cellulose nanofibers (CNFs) as nanofillers. Firstly, L-lactide monomers were grafted onto CNFs via ring-opening polymerization. The synthesized poly(lactic acid) grafted cellulose nanofibers (PLA-g-CNFs) compounded with Poly(lactic acid) (PLA) pellets improved storage modulus of the composite in both glassy state (low temperature) and rubbery state (high temperature). Dynamic mechanical analysis, including temperature ramp, frequency sweep, and creep-recovery, confirmed the enhancement of annealed composites to viscoelastic factors. Secondly, we converted CNFs into carbonized CNFs (CCNFs) through pyrolysis. When integrated with carbon black (CB) and polycaprolactone (PCL) matrix, the CCNF-CB-PCL conductive composites found applications for reinforcing, conducting, electromagnetic interference shielding, and deformation sensing. CCNFs also have superior dielectric properties. When irradiating CCNF-PLA composites with microwave, high dielectric loss CCNFs selectively absorbed microwave energy and generated localized heat in the surrounding regions. Such heat transferred to the adjacent PLA, triggering PLA chains to repack and form crystallites, and as a result, enhancing crystallinity as well as mechanical