On non-Abelian T-duality for non-semisimple groups

We revisit non-Abelian T-duality for non-semisimple groups, where it is well-known that a mixed gravitational-gauge anomaly leads to $\sigma$-models that are scale, but not Weyl-invariant. Taking into account the variation of a non-local anomalous term in the T-dual $\sigma$-model of Elitzer, Giveon, Rabinovici, Schwimmer \& Veneziano, we show that the equations of motion of generalized supergravity follow from the $\sigma$-model once the Killing vector $I$ is identified with the trace of the structure constants. As a result, non-Abelian T-duals with respect to non-semisimple groups are solutions to generalized supergravity. We illustrate our findings with Bianchi spacetimes.Comment: 20 pages; v2 show equations of motion of generalized supergravity follow from EGRSV sigma-mode

Fuzzy searching and routing in unstructured mobile peer-to-peer networks

© 2017, Springer Science+Business Media New York. Peer-to-Peer (P2P) networks offer a scalable solution for efficient query searching and sharing across the unstructured networks. With an increased overhead due to large amount of object searching and routing in unstructured P2P networks, it is a challenge to continue QoS routing among different mobile peers. Most existing mobile P2P protocols focus on inflexible techniques to route queries and discover objects of interest. Such common techniques incur a relatively high search time due to remarkable network traffic and duplication of query messages. The correlation between routing and mobility is crucial to efficiently search and route the query object in an overlay to avoid unnecessary consumption of network resources. Our previous fuzzy search controller model (Shah and Kim in 12th IEEE international conference on dependable, autonomic and secure computing (DASC), 2014) reduced the search time query processing in P2P networks, but it caused low hit rate and a high overhead due to peer mobility. Thus, this article proposes a scalable fuzzy controller based on probabilistic walk for unstructured mobile P2P networks to reduce the search time with controlled mobility. The search time is reduced by jumping a query walker to a 2-hop away ultrapeer, selected through a fuzzy scheme. Furthermore, each mobile ultrapeer shares its pong cache with its directly connected ultrapeer in order to increase the hit rate and reduce the network overhead. Simulations show that the fuzzy search controller gives better performance than the competing protocols in terms time 10% reduction in response time and 15% increase in hit rate in different mobility scenarios

A Facile Fabrication and Transfer Method of Vertically Aligned Carbon Nanotubes on a Mo/Ni Bilayer for Wearable Energy Devices

Carbon nanotubes are a promising material for flexible/wearable electrochemical device due to their mechanical softness, chemical stability, and high conductivity. Furthermore, the vertically aligned form of carbon nanotubes (VACNTs) have a large surface area due to their unique three-dimensional (3D) nanostructure. Thus, VACNTs are particularly useful for wearable electrochemical sensors and/or energy devices. However, VACNTs are generally grown via a high-temperature chemical vapor deposition process, which requires a rigid substrate. As a flexible/wearable device platform, therefore, VACNTs should be transferred from rigid substrates to soft substrates. Here, a facile fabrication and transfer method of a unique 3D nanostructure, that is, VACNTs on the Mo/Ni bilayer, for high performance flexible/wearable devices is reported. After growth of VACNTs on a Mo/Ni bilayer, VACNTs with the Mo/Ni bilayer can be easily peeled-off from the SiO2 wafer by using weak adhesion of Ni to SiO2 for transfer printing onto polymeric/elastomeric substrates. Moreover, the Mo layer helps facile growth of VACNTs, and the Mo/Ni bilayer underneath VACNTs maximizes the lateral current flow. The proposed 3D nanostructure (VACNTs on the Mo/Ni bilayer) is successfully applied as flexible electrodes for high-performance wearable asymmetric supercapacitors.

Ultrafast Intramolecular Proton Transfer Reaction of 1,2- Dihydroxyanthraquinone in the Excited State

1,2-Dihydroxyanthraquinone (alizarin) shows an ultrafast intramolecular proton transfer in the excited states between the adjacent hydroxyl and carbonyl groups. Due to the ground and electronic structure of locally excited and proton-transferred tautomers, alizarin shows dual emission bands with strong Stokes shifts. The energy barriers between the locally excited (LE) and proton-transferred (PT) tautomers in the excited state are strongly dependent on the solvent polarity and thus alizarin shows complicated photophysical properties including solvent and excitation dependences. The excited-state intramolecular proton transfer (ESIPT) of alizarin was monitored in time-resolved stimulated Raman spectroscopic investigation, where the instantaneous structural changes of anthraquinone backbone in 70~80 fs were captured. Two major vibrational modes of alizarin, ν(C=C) and ν(C=O) represent the proton transfer reaction in the excited state, which then leads to the vibrational relaxation of the product and the restructuring of solvent molecules. Ultrafast changes in solvent vibrational modes of dimethyl sulfoxide (DMSO) were also investigated for the solvation dynamics including hydrogen bond breaking and reformation

Simulating neutron stars with a flexible enthalpy-based equation of state parametrization in SpECTRE

Numerical simulations of neutron star mergers represent an essential step toward interpreting the full complexity of multimessenger observations and constraining the properties of supranuclear matter. Currently, simulations are limited by an array of factors, including computational performance and input physics uncertainties, such as the neutron star equation of state. In this work, we expand the range of nuclear phenomenology efficiently available to simulations by introducing a new analytic parametrization of cold, beta-equilibrated matter that is based on the relativistic enthalpy. We show that the new $\textit{enthalpy parametrization}$ can capture a range of nuclear behavior, including strong phase transitions. We implement the enthalpy parametrization in the $\texttt{SpECTRE}$, code, simulate isolated neutron stars, and compare performance to the commonly used spectral and polytropic parametrizations. We find comparable computational performance for nuclear models that are well represented by either parametrization, such as simple hadronic EoSs. We show that the enthalpy parametrization further allows us to simulate more complicated hadronic models or models with phase transitions that are inaccessible to current parametrizations.Comment: 20 pages, 14 figures, submitted to PRD, additional information on software including input files available at https://github.com/sxs-collaboration/paper-2023-spectre-enthalpy-eo

The Impact of Project-Based Learning on Teacher Self-Efficacy

The expansion of project-based learning has been advocated for as a solution and reform measure to the problem of rote learning-based teaching practices in Korean schools, deemed unfit for the development of diverse skills needed in the 21st century. While the ultimate goal of initiating project-based learning is to affect students in positive ways, it is important to analyze how conducting project-based learning affects teachers, as they are the direct implementers of teaching practices and are bound to have immense influence on the overall learning experience of students. By using the OECD TALIS database, we show that conducting project-based learning is strongly and positively associated with teacher self efficacy. Such results are in line with an analysis using data obtained from a field experiment on teacher training of project-based learning conducted on Daegu city middle schools