Hasil untuk "Nuclear and particle physics. Atomic energy. Radioactivity"

Alvin Garcia, Sydney Liu, Xiaodi Du et al.

The Imaging Neutral Particle Analyzer (INPA) at DIII-D is a diagnostic system used to accurately resolve the energy and spatial distributions of fast ions in fusion plasmas. A novel artificial intelligence (AI) technique named INPA-net is based on Reservoir Computing Networks and developed here to predict active and passive signals produced by charge-exchange reactions from injected and edge-cold neutrals, respectively, in magnetically confined fusion plasmas. This model is trained using a set of 21 time domain signals between 0 s to 3.35 s that includes injected beam and thermal plasma information, and 6444 real 2D experimental images of the INPA in 12 plasma discharges at DIII-D. The trained neural network is able to forecast experimental images in real-time. The model achieves an R -squared value of 0.91, which is higher than the 0.83 value achieved by a simple linear regression model. This improvement highlights the model’s enhanced predictive accuracy for measured images from the validation set. This AI approach is valuable due to its rapid response times and potential for integration into real-time plasma control systems. A version of this model capable of generating syntehic images would be useful for the real-time monitoring of fast-ion transport. A comprehensive sensitivity study reveals that INPA-net maintains high performance even with variations in the input parameters, indicating the model’s robustness and reliability. While developed for the INPA, the underlying architecture is adaptable and may be applied to various 2D imaging diagnostics in fusion research.

Jingqin Xue, Han Zhang, Hongfang Shen et al.

Abstract We present a PyTorch-based framework for forward folded reactor neutrino spectrum fitting that accelerates the two main bottlenecks: IBD mapping and detector response, using (i) result caching, (ii) banded sparse matrices, and (iii) blocked construction of the response. On an Intel Xeon Gold 6338 CPU, these techniques reduce per-fit walltime by $$\approx 7\times $$ ≈ 7 × (median over 5 runs) relative to a dense, unoptimized implementation, with $$<10^{-6}$$ < 10 - 6 relative spectral error versus a double-precision baseline. The framework has been applied to reactor-neutrino oscillation analyses and is reusable in other neutrino experiments that rely on forward-folded energy spectra, enabling practical Feldman–Cousins coverage studies and large parameter scans at substantially lower computational cost.

Debasmita Mohanty, Moreshwar Tayde, P.K. Sahoo

This study explores the possibility of gravastar solutions in the context of f(R,Lm,T) gravity, a variation that incorporates the Ricci scalar R, trace of the energy-momentum tensor T and the matter Lagrangian Lm with particular coupling strengths α and β. Also, we explore the interior of a gravastar within a framework motivated by non-commutative geometry, providing a physical justification for this choice. The thin shell is modeled as stiff matter, and two distinct exterior space-times, namely Reissner-Nordstrom and Bardeen metrics, are employed to construct the gravastar model. We examine the physical characteristics of these models, including proper length, entropy, energy, and the equation of state. We analyze the thin shell's effective pressure, energy density, and potential by utilizing the Israel junction conditions. Additionally, we discuss the stability of the thin shell and investigate the deflection angle it causes, which could be probed with future radio telescopes such as the Event Horizon Telescope (EHT). Finally, the surface redshift of the gravastar is evaluated, highlighting its relevance for potential observational detection.

Animesh Sah, Mohamed Rameez, Subir Sarkar et al.

Abstract We employ maximum likelihood estimators to examine the Pantheon+ catalogue of Type Ia supernovae for large scale anisotropies in the expansion rate of the Universe. The analyses are carried out in the heliocentric frame, the CMB frame, as well as the Local Group frame. In all frames, the Hubble expansion rate in the redshift range $$0.023< z < 0.15$$ 0.023 < z < 0.15 is found to have a statistically significant dipolar variation exceeding 1.5 km s $$^{-1}$$ - 1  Mpc $$^{-1}$$ - 1 , i.e. bigger than the claimed 1% uncertainty in the SH0ES measurement of the Hubble parameter $$H_0$$ H 0 . The deceleration parameter too has a redshift-dependent dipolar modulation at $$>5\sigma $$ > 5 σ significance, consistent with previous findings using the SDSSII/SNLS3 Joint Lightcurve Analysis catalogue. The inferred cosmic acceleration cannot therefore be due to a cosmological constant, but is likely a general relativistic effect due to the anomalous bulk flow in our local Universe.

Minoru Eto, Yu Hamada, Ryusuke Jinno et al.

Abstract We examine neutrino zeromode solutions on the electroweak Z-string and their effect on the stability of the string in the standard model and its extensions. We propose using topological invariants constructed from the momentum (and real) space topology of Green’s functions, often used for investigating edge modes in condensed matter physics. We analyze the standard model and then examine type-I and type-II extensions of the neutrino sector as well as their hybrid. Based on this analysis, we also comment on proposals in the literature to stabilize the Z-string.

XIANG Huawei1, 2, , , RONG Hua1, 2, 3, FAN Xinglang2, GENG Yan1, BAI Linhong4

For concrete, the strain tends to grow when the stress is kept at a constant level. This phenomenon is usually referred to as creep. Creep is an important physical property of concrete. For a prestressed concrete containment, creep could lead to prestress losses, stress redistribution, additional displacements, and even cracking. In general, the stress-strain relation of creep is nonlinear, but the principal stresses of concrete remain within the service stress range which is below 40% to 50% of the uniaxial strength. Therefore, the superposition principle can be utilized in linear elasticity, which works with the current values of stress and strain. Based on the theory of linear viscoelasticity, the principle of superposition can be used to characterize creep at a constant stress and the compliance function is used to describe the concrete creep mathematically, which facilitates numerical calculations. However, when the exponential algorithm is used to solve the creep effect of concrete, it is necessary to express the concrete creep compliance function by Dirichlet series and the calculation of the Dirichlet series corresponding to the compliance function is the key to implementing the exponential algorithm. The Weeks method for the inverse Laplace transform was used to approximate the Dirichlet series based on the continuous retardation spectrum method. The problem of approximating the concrete creep compliance function by the Weeks method was examined. First, the process of using the Weeks method to solve the continuous retardation spectrum was introduced. By taking the CEB MC90 creep model commonly used in engineering as an example, the equations for solving the concrete creep compliance function were derived by the Weeks method. The idea for improving the performance of the Weeks method was proposed. Based on this idea, the ranges of the various parameters that play a role in this solution were proposed. The numerical integration formula for the time-dependent term in the compliance function was derived. The results show that the calculation relative error with this method is no larger than ±1% when the duration is larger than 10 days. The validity of the algorithm was checked by comparing the numerical algorithm with the exact solution. This method is well suited for calculating the concrete creep compliance function for a long-term duration. The solution based on the Weeks method only requires the first-order derivative of the concrete creep compliance function to obtain the explicit function in the time domain, avoiding the complex computations of high-order derivatives and the low computational efficiency. Finally, the efficient Weeks method developed for the concrete creep model of CEB MC90 can also be extended and applied to other concrete creep models such as ACI 209R-92, JSCE, and GL2000.

Robert Edwards, Colin Egerer, Joseph Karpie et al.

Abstract The non-singlet helicity quark parton distribution functions (PDFs) of the nucleon are determined from lattice QCD, by jointly leveraging pseudo-distributions and the distillation spatial smearing paradigm. A Lorentz decomposition of appropriately isolated space-like matrix elements reveals pseudo-distributions that contain information on the leading-twist helicity PDFs, as well as an invariant amplitude that induces an additional z 2 contamination of the leading-twist signal. An analysis of the short-distance behavior of the space-like matrix elements using matching coefficients computed to next-to-leading order (NLO) exposes the desired PDF up to this additional z 2 contamination. Due to the non-conservation of the axial current, we elect to isolate the helicity PDFs normalized by the nucleon axial charge at the same scale μ 2. The leading-twist helicity PDFs as well as several sources of systematic error, including higher-twist effects, discretization errors, and the aforementioned z 2 contaminating amplitude are jointly determined by characterizing the computed pseudo-distribution in a basis of Jacobi polynomials. The Akaike Information Criterion is exploited to effectively average over distinct model parameterizations and cuts on the pseudo-distribution. Encouraging agreement is observed with recent global analyses of each non-singlet quark helicity PDF, notably a rather small non-singlet anti-quark helicity PDF for all quark momentum fractions.

LI Ming;XU Lijun;MAO Naqing;YE Hongsheng;LUO Rui;LIN Min

In order to meet the needs of on-site calibration of tritium monitor, the on-site calibration technology of tritium monitor is studied. According to the calibration method recommended by international standards, a portable calibration device was established, and the reference tritium gas for calibration was diluted and prepared by mass flow method. In order to solve the influence of on-site environment and other factors on the calibration process, a reference ionization chamber is introduced into the calibration circuit to calibrate and test the on-site tritium monitor. On the portable calibration device, reference tritium gas with different activity concentrations can be prepared for the calibration of different ranges of tritium monitors. After calibration, the calibration factor of M347 tritium monitor is 1.09 and the relative expanded uncertainty is 6% (k=2). The portable calibration device for on-site calibration can prepare tritium gas with three activity concentrations of different orders by using a tritium standard source with known concentration. The calibration of tritium monitor has good operability, easy popularization, and high accuracy.

Stefano Baiguera, Troels Harmark, Yang Lei

Abstract We consider limits of N $$ \mathcal{N} $$ = 4 super-Yang-Mills (SYM) theory that approach BPS bounds. These limits result in non-relativistic theories that describe the effective dynamics near the BPS bounds and upon quantization are known as Spin Matrix Theories. The near-BPS theories can be obtained by reducing N $$ \mathcal{N} $$ = 4 SYM on a three-sphere and integrating out the fields that become non-dynamical in the limits. In the previous works [1–3] we have considered various SU(1,1) and SU(1,2) types of subsectors in this limit. In the current work, we will construct the remaining Spin Matrix Theories defined near the 1 8 $$ \frac{1}{8} $$ -BPS subsectors, which include the PSU(1,1|2) and SU(2|3) cases. We derive the Hamiltonians by applying the spherical reduction algorithm and show that they match with the spin chain result, coming from the loop corrections to the dilatation operator. In the PSU(1,1|2) case, we prove the positivity of the spectrum by constructing cubic supercharges using the enhanced PSU(1|1)2 symmetry and show that they close to the interacting Hamiltonian. We finally analyse the symmetry structure of the sectors in view of an interpretation of the interactions in terms of fundamental blocks.

Duncan Farrah, Andreas Efstathiou, Jose Afonso et al.

We examine the origin of molecular gas heating in a sample of 42 infrared-luminous galaxies at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>z</mi><mo><</mo><mn>0.3</mn></mrow></semantics></math></inline-formula> by combining two sets of archival data: first, integrated CO line luminosities in the 1–0 and 5–4 through 13–12 transitions; second, results from radiative transfer modelling that decompose their bolometric emission into starburst, AGN, and host galaxy components. We find that the CO 1–0 and 5–4 through 9–8 lines primarily arise via radiative heating in the starburst and the host galaxy. In contrast, the CO 10–9 through 13–12 lines may arise primarily in the starburst and AGN, with an increasing contribution from mechanical heating and shocks. For the sample as a whole, we find no evidence that AGN luminosity affects the heating of molecular gas by star formation. However, for starbursts with low initial optical depths, a more luminous AGN may reduce the efficiency of starburst heating of the CO 5–4 and above lines, consistent with negative AGN feedback.

Sergey Frolov, Alessandro Sfondrini

Abstract The worldsheet S matrix of strings on the AdS 3 × S 3 × T 4 background is almost entirely fixed by symmetries, up to five functions — the dressing factors. These must satisfy several consistency conditions, in particular a set of crossing equations. We find that the existing proposal for the dressing factors, while crossing invariant, violates some of these consistency conditions. We put forward a new set of dressing factors and discuss in detail their analytic properties in the string and mirror region, as well as under bound-state fusion.

Shiraz Khan, S. A. Mardan, M. A. Rehman

Abstract In the present paper, we will incorporate three very useful aspects of astrophysics, generalized polytropes, Karmarkar condition and complexity factor to study the compact objects. For this purpose a charged anisotropic fluid distribution is used under static spherical symmetry. We develop a framework for class I generalized charged Lane–Emden equations for non-isothermal and isothermal regimes. Generalized polytropic equation of state with its two cases, mass density and energy density along with complexity factor lead us to the systems of differential equations and these systems are solved numerically. Finally, solutions of these systems are discussed graphically.

Ashis Saha, Sunandan Gangopadhyay, Jyoti Prasad Saha

Abstract The role played by the mutual information of subsystems on the Page curve is explored in this paper. With the total system consisting of the black hole and radiation, together with the inclusion of island, we observe that the vanishing of mutual information between $$B_+$$ B + and $$B_-$$ B - which in turn means the disconnected phase of the entanglement wedge corresponding to $$B_+\cup B_-$$ B + ∪ B - , yields a time scale of the order of scrambling time. This results in a time independent expression for the fine grained entropy of Hawking radiation consistent with the correct Page curve. We also find corrections to this entropy and Page time which are logarithmic and inverse power law in form.

Laurent Freidel, Daniele Pranzetti, Ana-Maria Raclariu

Abstract We identify in Einstein gravity an asymptotic spin-2 charge aspect whose conservation equation gives rise, after quantization, to the sub-subleading soft theorem. Our treatment reveals that this spin-2 charge generates a non-local spacetime symmetry represented at null infinity by pseudo-vector fields. Moreover, we demonstrate that the non-linear nature of Einstein’s equations is reflected in the Ward identity through collinear corrections to the sub-subleading soft theorem. Our analysis also provides a unified treatment of the universal soft theorems as conservation equations for the spin-0,-1,-2 canonical generators, while highlighting the important role played by the dual mass.

Roberto Casadio

Abstract We present a simple quantum description of the gravitational collapse of a ball of dust which excludes those states whose width is arbitrarily smaller than the gravitational radius of the matter source and supports the conclusion that black holes are macroscopic extended objects. We also comment briefly on the relevance of this result for the ultraviolet self-completion of gravity and the connection with the corpuscular picture of black holes.

Б.К. Рахадилов, Р.С. Кожанова, П. Ковалевский et al.

The work presents the results of a comparative study of volumetric and surface heat treatment impact on the structural-phase states, hardness, and wear resistance of steel 30HGSA. Surface hardening was conducted by the electrolyte-plasma method. Bulk quenching of the samples was carried out by heating to a temperature of 900 °C, followed by cooling in water and oil, and some of the samples after quenching were annealed at a temperature of 510 °C. The structural-phase states of 30HGSA steel samples were studied by metallographic and X-ray structural analysis. There were carried out the microhardness measurements, tribological tests according to the ball-disk scheme, as well as was determined the resistance of the samples to abrasive wear. It was determined that after electrolytic-plasma hardening, fine-acicular martensite with a small content of cementite is formed on the basis of metallographic and X-ray structural analyzes, and coarse-acicular martensite is formed after volume quenching in water and oil. It was determined that the microhardness increased to 400-460 HV after volume quenching, and subsequent annealing leads to a decrease in hardness to 330-360 HV. It was revealed that the electrolyte-plasma surface hardening leads to an increase in microhardness up to 2 times due to the formation of fine-acicular martensite.

Carlos Alberto Brayner Oliveira Lira, Pedro Paulo Dantas Souza Paiva

The Very High Temperature Reactor is a thermal, graphite moderated and helium cooled nuclear reactor. The purpose of this work is to study the behavior of the VHTR by means of parametric analysis, altering the energy generation profile in the fuel blocks and the influence of modifications in the geometry itself. The coolant flow through the coolant channels and by-pass channels were analyzed in a 1/12th section of a fuel block column. Geometry was used with by-pass channels of different dimensions, besides one that had only the cooling channels, without by-pass channel. It has been found that the existence of a by-pass flow induces an increase in the temperature gradient in the fuel block. Comparative studies were performed between the results obtained in simulations carried out with different profiles of thermal energy generation (uniform and sinusoidal) in the fuel channels. It was verified that when there is the same total thermal energy generation in the fuel block, the maximum temperature observed in each of the materials is smaller for the generation with sinusoidal profile. Computer simulations were performed using a geometry with a central channel with the same diameter as the others to verify the hypothesis that the existence of a temperature gradient in the fuel block, with the highest temperature at the center and the lowest temperature being at the periphery of this block, is due to the smaller dimension of the coolant channel located in the center of this block. The results obtained confirm the hypothesis

Keita Nii

Abstract We generalize the Giveon-Kutasov duality by adding possible Chern-Simons interactions for the U(N) gauge group. Some of the generalized dualities are known in the literature and many others are new to the best of our knowledge. The dualities are connected to the non-supersymmetric bosonization duality via mass deformations. For N = 1, there are an infinite number of magnetic-dual theories.

Vasilis Niarchos, Constantinos Papageorgakis, Elli Pomoni

Abstract We study type-B conformal anomalies associated with 1 2 $$ \frac{1}{2} $$ -BPS Coulomb-branch operators in 4D N $$ \mathcal{N} $$ = 2 superconformal field theories. When the vacuum preserves the conformal symmetry these anomalies coincide with the two-point function coefficients in the Coulomb-branch chiral ring. They are non-trivial functions of exactly-marginal couplings that can be determined from the S 4 partition function. In this paper, we examine the fate of these anomalies in vacua of the Higgs-branch moduli space, where conformal symmetry is spontaneously broken. We argue non-perturbatively that these anomalies are covariantly constant on conformal manifolds. In some cases, this can be used to show that they match in the broken and unbroken phases. Thus, we uncover a new class of data on the Higgs branch of 4D N $$ \mathcal{N} $$ = 2 conformal field theories that are exactly computable. An interesting application of this matching occurs in N $$ \mathcal{N} $$ = 2 circular quivers that deconstruct the 6D (2,0) theory on a torus. In that context, we argue that 4D supersymmetric localisation can be used to calculate non-trivial data involving 1 2 $$ \frac{1}{2} $$ -BPS operators of the 6D theory as exact functions of the complex structure of the torus.

J. Anthony