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A bstract The Cachazo-Strominger subleading soft graviton theorem for a positive helicity soft graviton is equivalent to the Ward identities for SL 2 ℂ ¯ currents. This naturally gives rise to a SL 2 ℂ ¯ current algebra living on the celestial sphere. The generators of the SL 2 ℂ ¯ current algebra and the supertranslations, coming from a positive helicity leading soft graviton, form a closed algebra. We find that the OPE of two graviton primaries in the Celestial CFT, extracted from MHV amplitudes, is completely determined in terms of this algebra. To be more precise, 1) The subleading terms in the OPE are determined in terms of the leading OPE coefficient if we demand that both sides of the OPE transform in the same way under this local symmetry algebra. 2) Positive helicity gravitons have null states under this local algebra whose decoupling leads to differential equations for MHV amplitudes. An n point MHV amplitude satisfies two systems of ( n − 2) linear first order PDEs corresponding to ( n − 2) positive helicity gravitons. We have checked, using Hodges’ formula, that one system of differential equations is satisfied by any MHV amplitude, whereas the other system has been checked up to six graviton MHV amplitude. 3) One can determine the leading OPE coefficients from these differential equations. This points to the existence of an autonomous sector of the Celestial CFT which holographically computes the MHV graviton scattering amplitudes and is completely defined by this local symmetry algebra. The MHV-sector of the Celestial CFT is like a minimal model of 2-D CFT.

A bstract In this paper we continue our study of the tree level MHV graviton scattering amplitudes from the point of view of celestial holography. In arXiv:2008.04330 we showed that the celestial OPE of two gravitons in the MHV sector can be written as a linear combination of SL 2 ℂ ¯ current algebra and supertranslation descendants. In this note we show that the OPE is in fact manifestly invariant under the infinite dimensional Virasoro algebra as is expected for a 2-D CFT. This is consistent with the conjecture that the holographic dual in 4-D asymptotically flat space time is a 2-D CFT. Since we get only one copy of the Virasoro algebra we can conclude that the holographic dual theory which computes the MHV amplitudes is a chiral CFT with a host of other infinite dimensional global symmetries including SL 2 ℂ ¯ current algebra, supertranslations and subsubleading soft graviton symmetry. We also discuss some puzzles related to the appearance of the Virasoro symmetry.

A bstract In this paper we study the tree-level OPE between two positive helicity outgoing gluons in the celestial CFT for the Yang-Mills theory chirally coupled to a massive scalar background. This theory breaks the translation as well as scale invariance. We compute the subleading terms in the OPE expansion and show that they are same as the subleading terms of the OPE expansions in the MHV sector. As a result the amplitudes of this theory also satisfy the set of differential equations obtained previously for MHV amplitudes in pure YM theory. This is not surprising because the symmetries coming from the leading and subleading soft gluon theorems do not change in the presence of a massive scalar background.

A bstract We study aspects of entanglement and extremal surfaces in various families of spacetimes exhibiting cosmological, Big-Crunch, singularities, in particular isotropic AdS Kasner. The classical extremal surface dips into the bulk radial and time directions. Explicitly analysing the extremization equations in the semiclassical region far from the singularity, we find the surface bends in the direction away from the singularity. In the 2-dim cosmologies obtained by dimensional reduction of these and other singularities, we have studied quantum extremal surfaces by extremizing the generalized entropy. The resulting extremization shows the quantum extremal surfaces to always be driven to the semiclassical region far from the singularity. We give some comments and speculations on our analysis.

Abstract In this note we determine the graviton-graviton OPE and the null states in any w 1+∞ symmetric theory on the celestial sphere. Our analysis shows that there exists a discrete infinite family of such theories. The MHV-sector and the quantum self dual gravity are two members of this infinite family. Although the Bulk Lagrangian description of this family of theories is not currently known to us, the graviton scattering amplitudes in these theories are heavily constrained due to the existence of null states. Presumably they are exactly solvable in the same way as the minimal models of 2-D CFT.

A bstract In this paper, we study the four-point celestial leaf amplitudes of massless scalar and MHV gluon scattering. These leaf amplitudes are non-distributional decompositions of the celestial amplitudes associated with a hyperbolic foliation of the Klein spacetime. Bulk scale invariance imposes constraints on the total conformal weights of the massless scalars or gluons. Using this constraint we show that the four-point leaf amplitudes have a simple pole singularity at z = z ¯ , where, z, z ¯ are two real independent conformal cross ratios. The distributional nature of the four-point celestial amplitudes is recovered by adding the leaf amplitudes in the timelike and spacelike wedges of the spacetime. We also verify that the MHV gluon leaf amplitudes satisfy a set of differential equations previously obtained for celestial MHV gluon amplitudes by considering the soft gluon theorems and the subleading terms in the OPE expansion between two positive helicity gluons.

Metal anodes hold considerable promise for high-energy-density batteries but are fundamentally limited by electrochemical irreversibility caused by uneven metal deposition and dendrite formation, which compromise battery lifespan and safety. The chaotic ion flow (or ion flux vortex) near the electrode surface, driving these instabilities, has remained elusive due to limitations in conventional techniques such as scanning electron and atomic force microscopies, which are invasive and incapable of probing internal structures of deposits. Here, we employ in-situ X-ray computed tomography (CT) to non-destructively visualize Zn deposition on LAPONITE-coated Zn anodes, thereby revealing the internal structural evolution and deposition orientation. Combined with computational fluid dynamics simulations, we demonstrate that the LAPONITE coating, with its separated positive and negative charge centers, suppresses ionic vortex formation, guiding uniform, dense, and vertically aligned Zn growth along (100) plane, thereby significantly mitigating dendrite growth. This translates into a 3.17-Ah Zn-MnO 2 pouch cell with stable performance over 100 cycles, offering a viable path toward scalable, high-performance metal-anode batteries. Uneven zinc growth limits the reversibility of zinc metal batteries. Here, authors use in situ X-ray computed tomography and fluid dynamics simulations to reveal how synthetic clay coating suppresses chaotic ion flow, enabling uniform zinc growth and stable cycling in a large-scale pouch cell.

A bstract We study Big-Bang or -Crunch cosmological singularities in 2-dimensional dilaton-gravity-scalar theories, in general obtained by dimensional reduction of higher dimensional theories. The dilaton potential encodes information about the asymptotic data defining the theories, and encompasses various families such as flat space, AdS, conformally AdS as arising from nonconformal branes, and more general nonrelativistic theories. We find a kind of universal near singularity behaviour independent of the dilaton potential, giving universal interrelations between the exponents defining the time behaviour near the cosmological singularity. More detailed analysis using a scaling ansatz enables finding various classes of cosmological backgrounds, recovering known examples such as the AdS Kasner singularity as well finding as new ones. We give some comments on the dual field theory from this point of view.

Rainfall and its interaction with soil, rock, and environmental factors such as soil moisture content, temperature variations, groundwater levels, and vegetation cover are critical determinants of slope stability in geotechnical engineering. This study introduces an innovative AI-driven system designed to predict the geotech- nical properties of slopes post-monsoon season. Utilizing a comprehensive dataset collected before and after the monsoon, the system targets the prediction of es- sential properties including unit weight, cohesion, and friction angle—parameters significantly influenced by monsoon rains. To quantify these impacts, the system calculates the percentage changes in these properties. A robust Exploratory Data Analysis (EDA) was conducted to elucidate the distributions of pre-monsoon and post-monsoon properties and uncover interrela- tionships among them. Machine learning models, encompassing Linear Regression, Random Forest Regression, Gradient Boosting Regressors, Support Vector Regres- sors, and Ensemble Models, were employed to predict post-monsoon properties based on pre-monsoon data and calculated changes. The models’ accuracies were evaluated using metrics such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), R-squared (R 2 ), Mean Bias Deviation (MBD), and Willmott’s Index of Agreement (d). Furthermore, the study explores transforming the regression task into a binary classification problem, categorizing slopes as stable or unstable based on predicted post-monsoon properties. Classification performance was assessed using Receiver Operating Characteristic (ROC) curves and the Area Under the Curve (AUC) metric. Feature importance and sensitivity analyses were performed using SHAP (SHapley Additive exPlanations) to identify the most influential factors affecting slope stability predictions. To enhance model robustness and generalizability, synthetic data was generated using Generative Adversarial Networks (GANs), augmenting the original dataset and ensuring a diverse range of conditions. The AI system demonstrated excep- tional capabilities in accurately predicting geotechnical property changes, thereby enabling engineers to proactively manage risks and improve slope stability assess- ments. This project underscores the significant potential of integrating advanced machine learning techniques with traditional geotechnical practices, particularly in regions experiencing heavy rainfall, to foster safer and more efficient engineering solutions.