Near-horizon geometries of supersymmetric AdS(5) black holes

We provide a classification of near-horizon geometries of supersymmetric, asymptotically anti-de Sitter, black holes of five-dimensional U(1)^3-gauged supergravity which admit two rotational symmetries. We find three possibilities: a topologically spherical horizon, an S^1 \times S^2 horizon and a toroidal horizon. The near-horizon geometry of the topologically spherical case turns out to be that of the most general known supersymmetric, asymptotically anti-de Sitter, black hole of U(1)^3-gauged supergravity. The other two cases have constant scalars and only exist in particular regions of this moduli space -- in particular they do not exist within minimal gauged supergravity. We also find a solution corresponding to the near-horizon geometry of a three-charge supersymmetric black ring held in equilibrium by a conical singularity; when lifted to type IIB supergravity this solution can be made regular, resulting in a discrete family of warped AdS(3) geometries. Analogous results are presented in U(1)^n gauged supergravity.Comment: Latex, 29 pages. v2: minor improvements, references adde

Two-flux Colliding Plane Waves in String Theory

We construct the two-flux colliding plane wave solutions in higher dimensional gravity theory with dilaton, and two complementary fluxes. Two kinds of solutions has been obtained: Bell-Szekeres(BS) type and homogeneous type. After imposing the junction condition, we find that only Bell-Szekeres type solution is physically well-defined. Furthermore, we show that the future curvature singularity is always developed for our solutions.Comment: 16 pages, Latex; typoes corrected; references added, minor modification

Teaching Case: Teaching Business Students Logistic Regression in R With the Aid of ChatGPT

Data Analytics has emerged as an essential skill for business students, and several tools are available to support their learning in this area. Due to the students’ lack of programming skills and the perceived complexity of R, many business analytics courses employ no-code analytical software like IBM SPSS Modeler. Nonetheless, generative Artificial Intelligence (AI) services such as ChatGPT can bridge the gap for students lacking programming skills. This teaching case demonstrates how students can use ChatGPT to generate R code for logistic regression analysis of a telecommunication company’s customer churn based on the Cross-Industry Standard Process Data Mining approach. ChatGPT enables students to implement the analysis method in R with a focus on building business solutions, freeing them from technical details. Teaching business students to use ChatGPT to implement data analysis is effective in helping them understand data, analytics models, and data interpretation. Moreover, this teaching case provides an opportunity for students to understand how to work with Artificial Intelligence in Data Analytics tasks

Teaching Tip: What You Need to Know about Gamification Process of Cybersecurity Hands-on Lab Exercises: Lessons and Challenges

Cybersecurity education is becoming increasingly important in modern society, and hands-on practice is an essential element. Although instructors provide hands-on labs in their cybersecurity courses, traditional lab exercises often fail to effectively motivate students. Hence, many instructors desire to incorporate gamification in hands-on training to engage and motivate cybersecurity students, especially beginner learners. Given the dearth of guiding examples, this paper aims to describe the holistic process of converting traditional cybersecurity hands-on lab exercises to gamified lab exercises in an undergraduate network security course. We find that the gamified cybersecurity lab promotes students’ engagement, learning experience, and learning outcomes. The results show the positive acceptance of gamification by students as well as instructors. While gamification has been used in competitions and training, the success in the classroom and students’ desire for more gamification show that further investment in gamification will be more important in the classroom. We expect this paper to help instructors who are interested in gamification 1) convert traditional lab exercises to gamified labs; 2) estimate the extra workload and potential benefits; and 3) plan resources for implementation. This process is applicable to any cybersecurity courses with hands-on assignments

Optimal unstirred state of a passive scalar

This work was supported by Leverhulme Trust grant PRG-2017-169.Given a passive tracer distribution, what is the simplest unstirred pattern that may be reached under incompressible advection? This question is partially motivated by recent studies of three-dimensional (3-D) magnetic reconnection, in which the patterns of a topological invariant called the field line helicity greatly simplify until reaching a relaxed state. We test two approaches: a variational method with minimal constraints, and a magnetic relaxation scheme where the velocity is determined explicitly by the pattern of. Both methods achieve similar convergence for simple test cases. However, the magnetic relaxation method guarantees a monotonic decrease in the Dirichlet seminorm of, and is numerically more robust. We therefore apply the latter method to two complex mixed patterns modelled on the field line helicity of 3-D magnetic braids. The unstirring separates into a small number of large-scale regions determined by the initial topology, which is well preserved during the computation. Interestingly, the velocity field is found to have the same large-scale topology as. Similarity to the simplification found empirically in 3-D magnetic reconnection simulations supports the idea that advection is an important principle for field line helicity evolution.Publisher PDFPeer reviewe

Impression Creep Behavior of Sn-3.5Ag-0.7Cu/Cu Brazed

AbstractBrazing, as one of the major connection technology, has been widely used in different areas such as aviation, aerospace, electronics and chemical industries etc. Sometimes creep fracture can be found in the brazed joints when they are used at high temperature. The conventional characterized method for creep properties cannot be used to study the brazed joints due to their small size. The impression technology has the potential to be used to study the creep properties of brazed joints, since no special requirements are needed for the size and shape of to-be-measured materials. In this investigation, Sn-3.5Ag-0.7Cu/Cu brazed joint is created and its creep properties is measured by impression creep testing. The effect of punching stress and temperature is studied on the impressing depth, which change from 70 to 100MPa and 80-130 oC, respectively. The microstructure of Sn-3.5Ag-0.7Cu/Cu is examined by Optical Microscope (OM), Scanning Electron Microscope (SEM) and Energy Dispersive Spectra (EDS). The results show that the impressing creep depth increases with the rise of temperature and punching stress. Creep resistance of the diffusion region has obvious effect on the creep resistance of the weld. The experimental results can provide the basis for the structural integrity analysis of brazed joints

Metamaterials proposed as perfect magnetoelectrics

Magnetoelectric susceptibility of a metamaterial built from split ring resonators have been investigated both experimentally and within an equivalent circuit model. The absolute values have been shown to exceed by two orders of magnitude that of classical magnetoelectric materials. The metamaterial investigated reaches the theoretically predicted value of the magnetoelectric susceptibility which is equal to the geometric average of the electric and magnetic susceptibilities.Comment: 5 pages, 3 figure

Qcompiler: quantum compilation with CSD method

In this paper, we present a general quantum computation compiler, which maps any given quantum algorithm to a quantum circuit consisting a sequential set of elementary quantum logic gates based on recursive cosine-sine decomposition. The resulting quantum circuit diagram is provided by directly linking the package output written in LaTex to Qcircuit.tex $$. We illustrate the use of the Qcompiler package through various examples with full details of the derived quantum circuits. Besides its generality and simplicity, Qcompiler produces quantum circuits which reflect the symmetry of the systems under study

Roper Resonance and S_{11}(1535) from Lattice QCD

Using the constrained curve fitting method and overlap fermions with the lowest pion mass at $180 {\rm MeV}$, we observe that the masses of the first positive and negative parity excited states of the nucleon tend to cross over as the quark masses are taken to the chiral limit. Both results at the physical pion mass agree with the experimental values of the Roper resonance ($N^{1/2+}(1440)$) and $S_{11}$ ($N^{1/2-}(1535)$). This is seen for the first time in a lattice QCD calculation. These results are obtained on a quenched Iwasaki $16^3 \times 28$ lattice with $a = 0.2 {\rm fm}$. We also extract the ghost $\eta' N$ states (a quenched artifact) which are shown to decouple from the nucleon interpolation field above $m_{\pi} \sim 300 {\rm MeV}$. From the quark mass dependence of these states in the chiral region, we conclude that spontaneously broken chiral symmetry dictates the dynamics of light quarks in the nucleon.Comment: 10 pages, 5 figures, revised version to appear in PL