A note on the integral equation for the Wilson loop in N = 2 D=4 superconformal Yang-Mills theory

We propose an alternative method to study the saddle point equation in the strong coupling limit for the Wilson loop in $\mathcal{N}=2$ D=4 super Yang-Mills with an SU(N) gauge group and 2N hypermultiplets. This method is based on an approximation of the integral equation kernel which allows to solve the simplified problem exactly. To determine the accuracy of this approximation, we compare our results to those obtained recently by Passerini and Zarembo. Although less precise, this simpler approach provides an explicit expression for the density of eigenvalues that is used to derive the planar free energy.Comment: 12 pages, v2: section 2.5 (Free Energy) amended and reference added, to appear in J. Phys.

Lithium Batteries and the Solid Electrolyte Interphase (SEI)—Progress and Outlook

Interfacial dynamics within chemical systems such as electron and ion transport processes have relevance in the rational optimization of electrochemical energy storage materials and devices. Evolving the understanding of fundamental electrochemistry at interfaces would also help in the understanding of relevant phenomena in biological, microbial, pharmaceutical, electronic, and photonic systems. In lithium-ion batteries, the electrochemical instability of the electrolyte and its ensuing reactive decomposition proceeds at the anode surface within the Helmholtz double layer resulting in a buildup of the reductive products, forming the solid electrolyte interphase (SEI). This review summarizes relevant aspects of the SEI including formation, composition, dynamic structure, and reaction mechanisms, focusing primarily on the graphite anode with insights into the lithium metal anode. Furthermore, the influence of the electrolyte and electrode materials on SEI structure and properties is discussed. An update is also presented on state-of-the-art approaches to quantitatively characterize the structure and changing properties of the SEI. Lastly, a framework evaluating the standing problems and future research directions including feasible computational, machine learning, and experimental approaches are outlined

Effect of Electrolyte Additives on the LiNi0.5_{0.5}Mn0.3_{0.3}Co0.2_{0.2}O2_{2} Surface Film Formation with Lithium and Graphite Negative Electrodes

The effect of various electrolyte additives (fluoroethylene carbonate (FEC), vinylene carbonate (VC), and propane sultone (PS)) on the performance of LiNi0.5Mn0.3Co0.2O2 (NMC532) electrodes in combination with lithium (half‐cell) and graphite (full‐cell) negative electrodes, is herein reported. The cathode/electrolyte interface (CEI) layer formed on the NMC532 electrode cycled up to 4.5 V versus Li+/Li is investigated by X‐ray photoelectron spectroscopy and scanning electron microscopy. This allows correlating the electrochemical performance of the electrodes to the CEI chemical composition, thickness, and morphology. All the investigated electrolyte additives exhibit beneficial effects in half‐ and full‐cell systems, confirming the effective passivation layer formation protecting the electrolyte from further decomposition at high voltages. It is found that the thickness of the CEI layer forming on the NMC532 electrodes in half‐ and full‐cell configuration is different. VC and PS are found to be the best additives to enhance the performance mainly due to their positive contribution to the CEI formation. The solid/electrolyte interphase (SEI) formed on the graphite electrode is also investigated and compared to the CEI layer formed on the cathode. The detection of typical SEI reduction products on the positive electrode surface confirms the occurrence of cross‐talking between the two electrodes

Graph Neural Networks for temporal graphs: State of the art, open challenges, and opportunities

Graph Neural Networks (GNNs) have become the leading paradigm for learning on (static) graph-structured data. However, many real-world systems are dynamic in nature, since the graph and node/edge attributes change over time. In recent years, GNN-based models for temporal graphs have emerged as a promising area of research to extend the capabilities of GNNs. In this work, we provide the first comprehensive overview of the current stateof-the-art of temporal GNN, introducing a rigorous formalization of learning settings and tasks and a novel taxonomy categorizing existing approaches in terms of how the temporal aspect is represented and processed. We conclude the survey with a discussion of the most relevant open challenges for the field, from both research and application perspectives

Reactive Metals as Energy Storage and Carrier Media: Use of Aluminum for Power Generation in Fuel Cell-Based Power Plants

In recent years, the energy production sector has experienced a growing interest in new energy vectors enabling energy storage and, at the same time, intersectoral energy applications among users. Hydrogen is one of the most promising energy storage and carrier media featuring a very high gravimetric energy density, but a rather low volumetric energy density. To this regard, this study focuses on the use of aluminum as energy storage and carrier medium, offering high volumetric energy density (23.5 kWh L$^{-1}$), ease to transport and stock (e.g., as ingots), and is neither toxic nor dangerous when stored. In addition, mature production and recycling technologies exist for aluminum. Herein, the performance of power systems driven by aluminum powder in terms of electrical efficiency (η$_{(I)}$) and round‐trip efficiency (RTE) is analyzed. Along with the additional advantages relating to high volumetric energy density, and safety and management aspects, the aluminum‐based technology appears to outperform the power‐to‐power systems based on hydrogen and liquid fuels

Some remarks on D-branes and defects in Liouville and Toda field theories

In this paper we analyze the Cardy-Lewellen equation in general diagonal model. We show that in these models it takes simple form due to some general properties of conformal field theories, like pentagon equations and OPE associativity. This implies, that the Cardy-Lewellen equation has simple form also in non-rational diagonal models. We specialize our finding to the Liouville and Toda field theories. In particular we prove, that conjectured recently defects in Toda field theory indeed satisfy the cluster equation. We also derive the Cardy-Lewellen equation in all $sl(n)$ Toda field theories and prove that the forms of boundary states found recently in $sl(3)$ Toda field theory hold in all $sl(n)$ theories as well.Comment: 30 pages, some comments, explanations and references adde

Tragacanth gum as green binder for sustainable water-processable electrochemical capacitor

9Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here we focus on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon-based for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)-based electrodes are thoroughly investigated and compared with another water-soluble binder largely used in this field, i.e. sodium-carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibits a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacts on the electrochemical performances resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC-based supercapacitor shows a superior thermal stability than CMC with a capacity retention of about 80 % after 10.000 cycles at 70 °C.partially_openopenScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, AndreaScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, Andre

Tragacanth Gum as Green Binder for Sustainable Water-Processable Electrochemical Capacitor

Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here, the focus was on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon‐based materials for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)‐based electrodes was thoroughly investigated and compared with another water‐soluble binder largely used in this field, sodium‐carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibited a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacted the electrochemical performance, resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC‐based supercapacitor showed a superior thermal stability compared with CMC, with a capacity retention of about 80 % after 10000 cycles at 70 °C