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Corrigendum to: Agronomic performance of sweet corn yield and quality due to colchicine application
No full textDFT study on geometries, electronic structures, and electronic absorption of naphthalene
No full textThis study introduces a novel quantum computational approach using Density Functional Theory (DFT) with multiple basis sets (particularly 6-31G) to examine naphthalene’s structural and electronic characteristics. Key theoretical investigations include Frontier molecular orbitals (HOMO–LUMO), Electronic band gap (E9), density of states (DOS), UV absorption spectra, Natural Bond Orbital (NBO) analysis, thermochemical properties under standard conditions, and optical properties, including direct/indirect transition band gaps. Employing DFT/6-31G with a fixed HOMO–LUMO gap of 4.75 eV, our results demonstrate strong consistency with recent DFT studies reporting gap values of 4.71, 4.873, and 4.74 eV, respectively. The geometric, electronic, and optical properties—including polarizabilities and hyperpolarizabilities—of naphthalene, is investigated using Density Functional Theory (DFT) with the B3LYP hybrid functional. Additionally, the Ultraviolet–Visible (UV–Vis) spectra were analyzed using a time-dependent (TD) DFT approach (TDSCF-DFT/B3LYP), which incorporates many-body effects and dynamic interactions under time-dependent potentials. The electronic absorption features in the visible and near-UV regions were computed, plotted, and assigned based on TD-DFT calculations
Dilaton coupling to
No full textWe explore a supergravity model based on the modified Kähler potential ,where is a chiral superfield containing the dilaton and is the chiral curvature superfield. The quartic term ensures stabilization of the curvature sector, in line with recent proposals in modified supergravity, while the linear term yields a dilaton-modulated contribution to the effective coefficient. As clarified via the superfield Legendre transform, the model is equivalent to Einstein supergravity coupled to three chiral superfields (, S, T), yielding six physical scalars. Full stability requires both the curvature–sector stabilization (via ) and a non-vanishing dilaton VEV. When the extra scalars are stabilized and , the kinetic mixing is exponentially suppressed during inflation (), reducing the dynamics to an effectively single-field Starobinsky model. Thus, cosmological viability is inherited conditionally from the established success of Starobinsky inflation. To the best of our knowledge, this represents the first explicit realization of dilaton-coupled modified supergravity, where a physical scalar (the dilaton) directly influences the curvature sector through the Kähler geometry. While chiral matter couplings to modified supergravity have been studied in the literature, the explicit coupling of the dilaton remains unexplored. The framework is presented as a phenomenological ansatz for exploring scalar–curvature unification in supersymmetry, with the understanding that a UV completion remains an open challenge
Advanced control strategies for stochastic systems using PDF optimisation
No full textThis paper presents an innovative probabilistic control framework for continuous-time stochastic systems. Unlike traditional control approaches that optimise deterministic control strategies, our framework directly optimises the probability density function (PDF) of the control signal, allowing for a more adaptable and robust response to stochastic variations. By integrating stochastic differential equations with the Hamilton–Jacobi–Bellman equation and utilising the Fokker–Planck dynamics, our method offers a precise and dynamic approach to managing uncertainty. The framework minimises the Kullback–Leibler divergence to align the system’s joint state and control distribution with a desired joint target distribution, ensuring effective control even in unpredictable environments. A novel algorithm iteratively refines the control PDF based on real-time feedback, further enhancing the system’s alignment with the target behaviour. The proposed method is demonstrated on an Ornstein–Uhlenbeck process, showcasing its effectiveness in steering the system’s state distribution toward desired outcomes and underscoring its broad applicability to stochastic systems
How elevated sources can cause local increases of sound pressure levels in the upwind domain
No full textWhile increased sound levels near the ground in downwind conditions are a well-studied topic, comparatively little attention has been given in the literature to increased sound pressure levels in upwind propagation. This increase, however, typically occurs only under specific conditions, including an elevated source location, a non-linear (e.g., logarithmic) wind or temperature profile, and a focus on particular distances within the upwind domain. These conditions are known to be responsible for the formation of caustics. Simultaneously, the sound level enhancement may be disturbed by diffraction, ground reflection, and its characteristics depend on the source structure, being most readily derivable for point sources. Consequently, investigations using models and comparisons with observations are challenging. This work uses two fundamentally different modelling approaches in their ability to capture such phenomena. The goal is to provide an intuitive understanding of the complex interactions involved in sound propagation under real atmospheric conditions, thereby supporting the interpretation of acoustic simulation and measurements in applied contexts
Rebrightenings of gamma-ray burst afterglows from an increasing magnetic inclination angle of a nascent magnetar
No full textContext. A nascent magnetar, accompanying a gamma-ray burst (GRB) explosion, releases enormous rotational energy via magnetic dipole radiation. The energy loss rate of the magnetar is determined by the strength of the magnetic field at the pole.
Aims. We investigated the effect of the magnetic inclination angle on the energy loss rate. The released energy is injected into the GRB jet and shapes the light curves of GRB afterglow. Different evolutionary approaches lead to different curves shapes.
Methods. A shallow decay phase in GRB X-ray afterglow may result from energy injection from a magnetar with a fixed inclination angle. A two-plateau phase may result from a decreasing inclination angle scenario. In this study, we considered an increasing inclination angle scenario. The energy loss rate of the magnetar increases as the magnetic inclination angle grows.
Results. Our analysis reveals that as the lost rotational energy injected into the GRB jet increases, rebrightening phases occur in the GRB afterglows. The rebrightening features are slight and short-lived.
Conclusions. The observed afterglow rebrightening of GRB 170822A and GRB 230414B can be well explained within our framework. Some GRB X-ray afterglows that exhibit slight and early rebrightenings may result from an increasing magnetic inclination angle of a nascent magnetar
A wide-field X-ray search for the Geminga pulsar halo with SRG/ART-XC
No full textSearches for the putative large-scale X-ray halo around the Geminga pulsar have been extensively performed using various narrow field-of-view X-ray telescopes. In this paper, we present wide-field scanning observation of Geminga with SRG/ART-XC. Our X-ray analysis provides, for the first time, direct imaging of a 3.5° ×3.5° region in the 4−12 keV energy band, comparable in extent to the expected Geminga emission. The ART-XC observation provides a highly uniform sky coverage without strong vignetting effects. The synchrotron X-ray halo flux was predicted using a physical model based on particle injection, diffusion, and cooling over the pulsar’s lifetime, as well as the spectral and spatial properties of the synchrotron X-ray and inverse-Compton gamma-ray emissions. The model is tuned to reproduce existing multiwavelength data from X-ray upper limits and GeV to TeV gamma-ray observations. After accounting for the high particle background and its uncertainties, no significant emission is found in the assumed source region, and X-ray flux upper limits are derived. These limits are less constraining by up to a factor of three with respect to existing results obtained with narrow field-of-view telescopes and longer exposure times. Nonetheless, we place direct and independent constraints on Geminga’s ambient magnetic field strength, which are compatible with other studies. Our methodology, including simulation for longer observation times, is applied for the first time to the wide field-of-view search for pulsar halos. Using extensive simulations, we also show that a 68% probability of detecting the Geminga pulsar halo can be achieved with a 20-day SRG/ART-XC exposure for a 3 μG magnetic field
The environment of TeV halo progenitors
No full textContext. TeV haloes are extended sources of very-high-energy gamma rays found around some middle-aged pulsars. The emission spanning several tens of parsecs suggests an efficient confinement of the ultra-relativistic lepton pairs produced by pulsars in their vicinity. The physical mechanism responsible for this suppressed transport has not yet been identified. In some scenarios, pair confinement may be linked to the medium the pulsars are located in.
Aims. We aim at understanding the type of medium pulsars probe over their lifetime.
Methods. We developed a model for the environment probed by moving pulsars, from their birth in core-collapse explosions – where they receive a natal kick – until their entry into the interstellar medium. The model involves: (i) a Monte-Carlo sampling of the properties of the massive-star progenitors of pulsars; (ii) a calculation of the structure of the surrounding medium shaped by these progenitors for the two cases of isolated stars and star clusters; and (iii) a computation of the evolution of supernova remnants in these parent environments. Ultimately, from a distribution of neutron star kick velocities, we assess the medium in which pulsars are located as a function of time. We first derived the statistical properties of a fully synthetic Galactic population and then applied the model to a selection of known pulsars to assess the likely nature of their environment.
Results. We show that pulsars escape into the interstellar medium at around 300 kyr, significantly later than assumed in the literature. Given our assumptions, all known pulsars with a confirmed TeV halo have high probabilities of still being in their parent environment, which suggests that efficient pair confinement is connected to the region influenced by progenitor stars. To test this, we provide the probability that known pulsars still reside in their parent environment for a list of known pulsars
The SPIRou Legacy Survey
No full textContext. M dwarfs are prime targets in the search for exoplanets because of their prevalence and because low-mass planets can be better detected with radial velocity (RV) methods. In particular, the near-infrared (NIR) spectral domain offers an increased RV sensitivity and potentially reduced stellar activity signals. Precise NIR RV measurements are strongly affected by telluric absorption lines from the Earth’s atmosphere, however.
Aims. We searched for planets orbiting Gl 725 B, a nearby late-M dwarf located at 3.5 pc, using high-precision SPIRou RV observations. We also assessed the effect of telluric contamination on these measurements and evaluated the performance of the weighted principal component analysis reconstruction (wapit
A one-parameter two-zone leptonic model for the blazar sequence
No full textBlazars, a subclass of radio-loud active galactic nuclei with relativistic jets aligned close to our line of sight, emit highly variable nonthermal radiation across the electromagnetic spectrum. The physical origin of their emission and the blazar sequence remain open questions. We present a self-consistent two-zone leptonic model in which relativistic electrons accelerate in a compact region, losing energy via synchrotron and inverse Compton processes, and escape into a larger zone permeated by an external photon field associated with magnetohydrodynamic winds from the accretion disk. By varying only the mass accretion rate onto the central black hole, the model naturally reproduces the blazar sequence, including Compton dominance, γ-ray spectral indices, and the positions of synchrotron and inverse Compton peaks, while variations in the secondary parameters account for the observed spread in the data. Flat-spectrum radio quasars exhibit strong external Compton emission from the extended zone, whereas BL Lac objects are dominated by synchrotron and synchrotron self-Compton emission from the compact acceleration region. This framework highlights the key role of accretion rate and spatially structured emission zones in shaping blazar spectra and provides a unified interpretation of their diverse phenomenology