Different critical points of chiral and deconfinement phase transitions in (2+1)-dimensional fermion-gauge interacting model

Based on the truncated Dyson-Schwinger equations for fermion and massive boson propagators in QED$_3$, the fermion chiral condensate and the mass singularities of the fermion propagator via the Schwinger function are investigated. It is shown that the critical point of chiral phase transition is apparently different from that of deconfinement phase transition and in Nambu phase the fermion is confined only for small gauge boson mass.Comment: 5 Pages and 3 figure

Zoom data analysis in an introductory course in mechanical engineering

[EN] This investigation studies various data extracted from Zoom meetings which are used in teaching an introductory course in mechanical engineering online. The effect of using Chat tool is discussed by extracting and analyzing the data in chat report. The parameters, such as number of chatting students, chatting participation rate, as well as average numer of chats per student, can show students activeness from different perspectives. Participcation in polling and polling performance are also studied by extracting data from polling reports. Non-graded polling activities are found to be effective of increase attendance of students. The using of breakout room doesn’t show its effectiveness in online learning of this introductory course.Tao, H.; Feng, B. (2021). Zoom data analysis in an introductory course in mechanical engineering. En 7th International Conference on Higher Education Advances (HEAd'21). Editorial Universitat Politècnica de València. 855-862. https://doi.org/10.4995/HEAd21.2021.12823OCS85586

Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors

The strongly correlated electron fluids in high temperature cuprate superconductors demonstrate an anomalous linear temperature ($T$) dependent resistivity behavior, which persists to a wide temperature range without exhibiting saturation. As cooling down, those electron fluids lose the resistivity and condense into the superfluid. However, the origin of the linear-$T$ resistivity behavior and its relationship to the strongly correlated superconductivity remain a mystery. Here we report a universal relation $d\rho/dT=(\mu_0k_B/\hbar)\lambda^2_L$, which bridges the slope of the linear-$T$-dependent resistivity ($d\rho/dT$) to the London penetration depth $\lambda_L$ at zero temperature among cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and heavy fermion superconductors CeCoIn$_5$, where $\mu_0$ is vacuum permeability, $k_B$ is the Boltzmann constant and $\hbar$ is the reduced Planck constant. We extend this scaling relation to different systems and found that it holds for other cuprate, pnictide and heavy fermion superconductors as well, regardless of the significant differences in the strength of electronic correlations, transport directions, and doping levels. Our analysis suggests that the scaling relation in strongly correlated superconductors could be described as a hydrodynamic diffusive transport, with the diffusion coefficient ($D$) approaching the quantum limit $D\sim\hbar/m^*$, where $m^*$ is the quasi-particle effective mass.Comment: 8 pages, 2 figures, 1 tabl