Classical Level Research Articles

Screening outstanding mechanical properties and low lattice thermal conductivity using global attention graph neural network

Mechanical and thermal properties of materials are extremely important for various engineering and scientific fields such as energy conversion and energy storage. However, the characterization of these properties via high throughput screening at the quantum level, although highly accurate, is inefficient and very time- and resource-consuming. In contrast, prediction at the classical level is highly efficient but less accurate. We deploy scalable global attention graph neural network for accurate prediction of mechanical properties which bridge the gap between the accuracy at the quantum level and efficiency at the classical level. Using 10,158 elastic constants as training data, we trained the models on 5 mechanical properties, namely bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness. With the trained model, we predicted 775,947 data in search of materials with ultrahigh hardness. We further verify the recommended ultrahigh hardness materials by high precision first principles calculations, and we finally identify 20 structures with extreme hardness close to diamond, the hardest material in nature. Among those, two super hard materials are completely new and have not been reported in literature so far. We further recommend potential materials from bulk modulus prediction to search low lattice thermal conductivity, and we verify the thermal conductivity of 338 structures with first principles. Our results demonstrate that one can find materials with extreme mechanical properties recommended by graph neural network and low thermal conductivity material from bulk modulus prediction with minimal first principles calculations of the structures (only 0.04%) in the large-scale materials pool.

Effective actions in supersymmetric gauge theories: heat kernels for non-minimal operators

We study the quantum dynamics of a system of n Abelian mathcal{N} = 1 vector multiplets coupled to frac{1}{2}nleft(n+1right) chiral multiplets which parametrise the Hermitian symmetric space Sp(2n, ℝ)/U(n). In the presence of supergravity, this model is super-Weyl invariant and possesses the maximal non-compact duality group Sp(2n, ℝ) at the classical level. These symmetries should be respected by the logarithmically divergent term (the “induced action”) of the effective action obtained by integrating out the vector multiplets. In computing the effective action, one has to deal with non-minimal operators for which the known heat kernel techniques are not directly applicable, even in flat (super)space. In this paper we develop a method to compute the induced action in Minkowski superspace. The induced action is derived in closed form and has a simple structure. It is a higher-derivative superconformal sigma model on Sp(2n, ℝ)/U(n). The obtained mathcal{N} = 1 results are generalised to the case of mathcal{N} = 2 local supersymmetry: a system of n Abelian mathcal{N} = 2 vector multiplets coupled to mathcal{N} = 2 chiral multiplets XI parametrising Sp(2n, ℝ)/U(n). The induced action is shown to be proportional to int {textrm{d}}^4x{textrm{d}}^4theta {textrm{d}}^4overline{theta}Emathfrak{K}left(X,overline{X}right) , where mathfrak{K}left(X,overline{X}right) is the Kähler potential for Sp(2n, ℝ)/U(n). We also apply our method to compute DeWitt’s a2 coefficients in some non-supersymmetric theories with non-minimal operators.

Quantum avoidance of Gödel’s closed timelike curves

In a large class of nonlocal as well as local higher derivative theories minimally coupled to the matter sector, we investigate the exactness of two different classes of homogeneous Gödel-type solutions, which may or may not allow closed time-like curves (CTC). Our analysis is limited to spacetimes solving the Einstein’s EoM, thus we can not exclude the presence of other Gödel-type solutions solving the EoM of local and nonlocal higher derivative theories but not the Einstein’s EoM. It turns out that the homogeneous Gödel spacetimes without CTC are basically exact solutions for all theories, while the metrics with CTC are not exact solutions of (super-)renormalizable local or nonlocal gravitational theories. Hence, the quantum renormalizability property excludes theories suffering of the Gödel’s causality violation. We also comment about nonlocal gravity non-minimally coupled to matter. In this class of theories, all the Gödel’s spacetimes, with or without CTC, are exact solutions at classical level. However, the quantum corrections, although perturbative, very likely spoil the exactness of such solutions. Therefore, we can state that the Gödel’s Universes with CTC and the super-renormalizability are mutually exclusive.

Analysis of unit level models for small area estimation in crop statistics assisted with satellite auxiliary information

Crop statistics for a small area, such as the community development block, are an increasingly important topic in agricultural statistics. Under normality assumptions, the classic Empirical Best Linear Unbiased Prediction (EBLUP) technique is effective for predicting small area means, however the Small Area Estimation (SAE) model can be heavily affected by the incidence of outliers or deviations from the expected distribution. The purpose of this study was to estimate variance, predict block-level wheat crop yield in the Hisar and Sirsa district of Haryana by classical SAE method and a robust random-effect predictor using a slight generalization of Huber’s Proposal 2. In the case of Sirsa district, the results of classical and robust unit level SAE were very close, but not in the case of Hisar district. This could be due to the influential observation found in the Hisar data set. More accurate EBLUP wheat yield estimates are obtained when the Huber-type M-estimation method is initialized by the least square regression estimator.

A mass-preserving level set method for simulating 2D/3D fluid flows with deformed interface

This research paper focuses on the development of a novel interface-capturing solver for predicting two-phase flow in 2D/3D Cartesian meshes within the framework of Eulerian approaches. The primary objective is to ensure mass conservation and accurate capture of interface topology. To achieve this, a mass-preserving level set advection equation formulated as a scalar sign-distance function is proposed. The key innovation of the Eulerian solver lies in the incorporation of a scalar speed function for robust reconstruction of the classical level set equation. The effectiveness and reliability of the proposed flow solver in solving incompressible two-phase viscous flow equations are demonstrated through several benchmark problems.

Emergent Diffeomorphism Invariance in Toy Models

AbstractConceptual difficulties in semiclassical and quantum gravity arise from diffeomorphism invariance of classical general relativity. With a motivation to shed some light on these difficulties, a class of toy models for which one‐dimensional diffeomorphism invariance, namely time‐reparametrization invariance, emerges at the classical level from energy conservation are studied. An attempt to quantize the models while taking the invariance seriously leads to toy versions of the problem of time in quantum gravity, of the cosmological constant problem, and of the black hole firewall problem. Nevertheless, all these problems are easily resolved by taking into account that the invariance emerges only at the classical level, while the fundamental theory that needs to be quantized is not diffeomorphism invariant.

Galilean fermions: Classical and quantum aspects

We study the classical and quantum "properties" of Galilean fermions in 3+1 dimensions. We have taken the case of massless Galilean fermions minimally coupled to the scalar field. At the classical level, the Lagrangian is obtained by null reducing the relativistic theory in one higher dimension. The resulting theory is found to be invariant under infinite Galilean conformal symmetries. Using Noether's procedure, we construct the corresponding infinite conserved charges. Path integral techniques are then employed to probe the quantum "properties" of the theory. The theory is found to be renormalizable. A novel feature of the theory is the emergence of mass scale at the first order of quantum correction. The conformal symmetry of the theory breaks at the quantum level. We confirm this by constructing the beta function of the theory.

Quantum physics and biology: the local wavefunction approach

Is there a single linearly evolving Wave Function of the Universe that is able to lead to all the nonlinearities we see around us? This proposal seems a priori highly implausible. I claim that instead, in the real Universe, generically only local wave functions exist. Non-local wave functions occur for carefully engineered contexts such as Bell experiments, but there is no single wave function for a cat or macroscopic object such as a brain, let alone for the Universe as a whole. Contextual wave function collapse leads to a defensible version of the Copenhagen interpretation of quantum theory, where classical macro levels provide the context for quantum events and biological emergence. Complexity arises via multiscale adaptive modular hierarchical structures that enable logical branching to emerge from the underlying linear physics. Each emergent level is causally effective because of the meshing of upwards and downwards causation that takes place consistently with that physics. Quantum chemistry approaches in biological contexts fit this local wavefunction picture.

Supervised Laser-speckle Image Sampling of Skin Tissue to Detect Very Early Stage of Diabetes by Its Effects on Skin Subcellular Properties

Objective: This paper investigates the effectiveness of a multi-disciplinary system based on laser speckle image sampling, image texture analysis, and artificial intelligence (AI), applied to the early detection of diabetes disease. The main objective is to develop an optimized unified technique to exploit the cellular form of skin structure and its low-level interaction with a specific laser light at critical wavelength which generates laser speckle effect to characterize sub-skin subtle cellular changes. This goal is achieved by the classification process which leads to detecting the presence of diabetes non-invasively from skin properties. Methods: With the latest developments in AI, laser-optics and laser speckle imaging technologies, it could be possible to optimize laser light parameters such as its wavelength, energy level, and its laser speckle image texture measures to achieve this goal. In the proposed work, such interdisciplinary techniques were demonstrated, which normally would not be possible by earlier conventional methods due to the lack of such optimized combinations. Results: Through the optimization of system parameters in laser-optic components, AI utilities, and texture analysis methods, it is possible to obtain up to 90% classification accuracy to identify normal and diabetes affected skin groups. Conclusion: The new approach is potentially more effective than the classical skin glucose level observation because of its optimized combination of laser physics and AI techniques. Additionally, it allows non-expert individuals to perform more frequent skin tissue tests for an early detection of diabetes. Cost effectiveness, which is another target for the proposed system, has also been justified by using low-cost system components, such as a very low-power laser source and normal digital camera.

Quantum pseudointegrable Hamiltonian impact system.

Quantization of a toy model of a pseudointegrable Hamiltonian impact system is introduced, including Einstein-Brillouin-Keller quantization conditions, a verification of Weyl's law, the study of their wave functions, and a study of their energy levels properties. It is demonstrated that the energy level statistics are similar to those of pseudointegrable billiards. Yet, here, the density of wave functions which concentrate on projections of classical level sets to the configuration space does not disappear at large energies, suggesting that there is no equidistribution in the configuration space in the large energy limit; this is shown analytically for some limit symmetric cases and is demonstrated numerically for some nonsymmetric cases.

Nonlinear scattering of classical gravitons

The nonlinear classical graviton solution of the Einstein equations is given to second order in the null surface formulation (NSF). We solve the NSF field equations in a perturbative scheme that gives geometrical and finite results at each order of the expansion obtaining the main variables of the formalism to second order. Then, using an algebraic relationship with the NSF variables, we obtain the metric components and the nonlinear scattering of incoming gravitons. We also analyze the relevance of this result at a classical and quantum level.

Elucidating the toxic effect and disease mechanisms associated with Lyso-Gb3 in Fabry disease.

Fabry disease stems from a deficiency of alpha-galactosidase and results in the accumulation of globotriaosylceramide (Gb3). However, the production of its deacylated form globotriaosylsphingosine (lyso-Gb3) is also observed and its plasma levels have closer association with disease severity. Studies have shown that lyso-Gb3 directly affects podocytes and causes sensitisation of peripheral nociceptive neurons. However, little is understood of the mechanisms of this cytotoxicity. To study the effect on neuronal cells, we incubated SH-Sy5y cells with lyso-Gb3 at low (20ng/mL) and high (200ng/mL) levels, to mimic mild and classical FD serum levels. We used glucosylsphingosine as a positive control to determine specific effects of lyso-Gb3. Proteomic analyses revealed that cellular systems affected by lyso-Gb3 included cell signalling particularly protein ubiquitination and protein translation. To confirm ER/proteasome perturbations, we performed an immune enrichment of ubiquitinated proteins and demonstrated specific increased protein ubiquitination at both doses. The most ubiquitinated proteins observed included the chaperone/heat shock proteins, cytoskeletal proteins and synthesis/translation proteins. To detect proteins that interact directly with lyso-Gb3, we immobilised lyso-lipids, then incubated them with neuronal cellular extracts and identified bound proteins using mass spectrometry. Proteins that specifically bound were chaperones and included HSP90, HSP60 and the TRiC complex. In conclusion, lyso-Gb3 exposure affects pathways involved in protein translation and folding. This response is observed as increased ubiquitination and changes in signalling proteins which may explain the multiple biological processes, particularly cellular remodelling, often associated with FD.

PENERAPAN MODEL PEMBELAJARAN PJBL UNTUK MENINGKATKAN PEMAHAMAN KONSEP PEMBELAJARAN MATEMATIKA MATERI MEMBANDINGKAN DAN MENGURUTKAN BILANGAN CACAH

Improving the learning outcomes of Class 1A students of SDN 2 Girimoyo in Mathematics subjects on sorting and comparing numbers 1-20 by using the PJBL learning model. The Classroom Action Research method is carried out collaboratively between researchers as learning innovators and learning implementers. Student learning outcomes improved. Both from the attitude and skill aspects. And summative learning outcomes or knowledge also increased, from Pre-Cycle the classical level of completeness was only 45% in Cycle I increased to 64% and in Cycle I increased to 82%. The use of the PJBL Learning model in Mathematics subjects on sorting and comparing small numbers 1-20 in Class 1A SDN 2 Girimoyo experienced a significant increase in completeness. Thus the PTK carried out can be declared successful in improving student learning outcomes

Training Data Generation for U-Net Based MRI Image Segmentation using Level-Set Methods

Image segmentation has been a well-addressed problem in pattern recognition for the last few decades. As a sub-problem of image segmentation, the background separation in biomedical images generated by magnetic resonance imaging (MRI) has also been of interest in the applied mathematics literature. Level set evolution of active contours idea can successfully be applied to MRI images to extract the region of interest (ROI) as a crucial preprocessing step for medical image analysis. In this study, we use the classical level set solution to create binary masks of various brain MRI images in which black color implies background and white color implies the ROI. We further used the MRI image and mask image pairs to train a deep neural network (DNN) architecture called U-Net, which has been proven to be a successful model for biomedical image segmentation. Our experiments have shown that a properly trained U-Net can achieve a matching performance of the level set method. Hence we were able to train a U-Net by using automatically generated input and label data successfully. The trained network can detect ROI in MRI images faster than the level-set method and can be used as a preprocessing tool for more enhanced medical image analysis studies.

Classical double copy of spinning worldline quantum field theory

We study the classical double copy of massive spinning objects in the worldline quantum field theories (WQFT) formalism. We couple the mathcal{N} = 1 supersymmetric model to a Yang-Mills background to describe the propagation of a spin-half particle interacting with gluons. At the classical level, this model captures physical effects up to linear order in spin. We propose a double copy relation to map the spin tensors to the gravitation side. Enforcing R-symmetry and supersymmetry (SUSY) on the double copy integrands, we find that the gravitational theory is the mathcal{N} = 2 particle coupled to dilaton-gravity (DG). We check the double copy prescription for the eikonal phase up to next-to-leading order and for radiation at leading order in coupling constants, finding that the Grassmann nature of the spin tensor in WQFT plays a crucial role in finding full agreement with direct calculation in the mathcal{N} = 2 model. We show how to deform the SUSY charges of the free theory to include DG. Since the constraints algebra is first class, the worldline model can be quantized, describing the propagation of a massive vector field coupled to DG, in agreement with the literature. In addition, we investigate the double copy without preserving SUSY and R-symmetry, finding that the B-field also couples to the worldline.

An underwater small target boundary segmentation method in forward-looking sonar images

Underwater target boundary segmentation is integral to forward-looking sonar image processing. However, small target boundary segmentation is always challenging due to the low resolution, low signal-to-noise ratio, and inhomogeneity of intensity of forward-looking sonar images. This paper proposes an improved level set segmentation method to accurately obtain the contour of small targets in the forward-looking sonar images: morphological reconstruction combined with the level set method (MRLSM). Compared with the classical level set and the level set method combined with the morphological method, MRLSM improves the accuracy and stability for forward-looking sonar image segmentation. Furthermore, the fuzzy C-means, Markov random field, and MRLSM are applied to the numerical simulations and experimental data for comparison. The deep learning methods are also used to compare the performances. The results demonstrated that the proposed method is more accurate, robust, and considerable for underwater small target boundary segmentation.

Optical Channeling of Low Energy Antiprotons in Thin Crystal Targets

A relevant aspect of the interactions between charged fermions and crystal targets is coherence, which can exist at both classical and quantum levels. In the case of antiprotons crossing crystal targets, there are theories and measurements of classical-level coherence effects, in particular, channeling effects. For the present study, we assume the existence of a low-energy regime where the electrostatic interactions between an antiproton and the crystal atoms lead to a local loss in the beam flux as their leading effect. We expect this assumption to be well-justified for antiproton (p¯) energies below 100 eV, with a progressive transition to a standard “Rutherford regime” in the energy range 100–1000 eV. Under these conditions, the target can be treated as an optical absorber with a periodical structure, which can be simplified by considering a multi-layer planar structure only. As in standard optics, wave absorption is accompanied by interference and diffraction. Assuming sub-nanometer ranges for the relevant parameters and a realistic angular spread for the antiproton beam, we find narrow-angle focusing effects that reproduce the classical channeling effect at a qualitative level. We also find that diffraction dominates over interference, although this may strongly depend on the target details.

Towards a theory of surface orbital magnetization

The theory of bulk orbital magnetization has been formulated both in reciprocal space based on Berry curvature and related quantities, and in real space in terms of the spatial average of a quantum mechanical local marker. Here we consider a three-dimensional antiferromagnetic material having a vanishing bulk but a nonzero surface orbital magnetization. We ask whether the surface-normal component of the surface magnetization is well defined, and if so, how to compute it. As the physical observable corresponding to this quantity, we identify the macroscopic current running along a hinge shared by two facets. However, the hinge current only constrains the difference of the surface magnetizations on the adjoined facets, leaving a potential ambiguity. By performing a symmetry analysis, we find that only crystals exhibiting a pseudoscalar symmetry admit well-defined magnetizations at their surfaces at the classical level. We then explore the possibility of computing surface magnetization via a coarse-graining procedure applied to a quantum local marker. We show that multiple expressions for the local marker exist, and apply constraints to filter out potentially meaningful candidates. Using several tight-binding models as our theoretical test bed and several potential markers, we compute surface magnetizations for slab geometries and compare their predictions with explicit calculations of the macroscopic hinge currents of rod geometries. We find that only a particular form of the marker consistently predicts the correct hinge currents.

Nonperturbative gedanken experiments in Einstein-dilaton-Gauss-Bonnet gravity: Nonlinear transitions and tests of the cosmic censorship beyond general relativity

As the only gravity theory with quadratic curvature terms and second-order field equations, Einstein-dilaton-Gauss-Bonnet gravity is a natural testbed to probe the high-curvature regime beyond General Relativity in a fully nonperturbative way. Due to nonperturbative effects of the dilatonic coupling, black holes in this theory have a minimum mass which separates a stable branch from an unstable one. The minimum mass solution is a double point in the phase diagram of the theory, wherein the critical black hole and a wormhole solution coexist. We perform extensive nonlinear simulations of the spherical collapse onto black holes with scalar hair in this theory, especially focusing on the region near the minimum mass. We study the nonlinear transition from the unstable to the stable branch and assess the nonlinear stability of the latter. Furthermore, motivated by modeling the mass loss induced by Hawking radiation near the minimum mass at the classical level, we study the collapse of a phantom field onto the black hole. When the black-hole mass decreases past the critical value, the apparent horizon shrinks significantly, eventually unveiling a high-curvature elliptic region. We argue that evaporation in this theory is bound to either violate the weak cosmic censorship or produce horizonless remnants. Addressing the end-state might require a different evolution scheme.

What Is the Fate of Hawking Evaporation in Gravity Theories with Higher Curvature Terms?

During the final stages of black hole evaporation, ultraviolet deviations from general relativity eventually become dramatic, potentially affecting the end state. We explore this problem by performing nonlinear simulations of wave packets in Einstein-dilaton-Gauss-Bonnet gravity, the only gravity theory with quadratic curvature terms which can be studied at a fully nonperturbative level. Black holes in this theory have a minimum mass but also a nonvanishing temperature. This poses a puzzle concerning the final fate of Hawking evaporation in the presence of high-curvature nonperturbative effects. By simulating the mass loss induced by evaporation at the classical level using an auxiliary phantom field, we study the nonlinear evolution of black holes past the minimum mass. We observe a runaway shrink of the horizon (a nonperturbative effect forbidden in general relativity) which eventually unveils a high-curvature elliptic region. While this might hint to the formation of a naked singularity (and hence to a violation of the weak cosmic censorship) or of a pathological spacetime region, a different numerical formulation of the initial-value problem in this theory might be required to rule out other possibilities, including the transition from the critical black hole to a stable horizonless remnant. Our Letter is relevant in the context of the information-loss paradox, dark-matter remnants, and for constraints on microscopic primordial black holes.