An effect of extra compactified dimensions of space in the molecule $$\hbox {NO}_{{2}}$$

The theory of large extra compactified dimensions of space (ADD-model) predicts that gravity may become strong in a compactification space of the size of a molecule and may affect the vibrational motion of a molecule. In triatomic molecules like $$\hbox {NO}_{{2}}$$ NO 2 nuclear dynamics is strongly coupled to electronic dynamics at the intersection of electronic states (conical intersection). We discuss experimental results on $$\hbox {NO}_{{2}}$$ NO 2 which reveal that the collision-free molecule optically excited into a symmetric stretch vibration mode of an electronic state with conical intersection undergoes an irreversible non-radiative transition into an asymmetric stretch vibration mode in combination with a change of the electronic state. We suggest ascribing this irreversible non-radiative transition to a gravitational perturbation on the vibrational motion in $$\hbox {NO}_{{2}}$$ NO 2 . This gravitational perturbation deactivates the upper state of the optical transition. The width of the absorption line is given by the characteristic time of the gravitational perturbation and not by the radiative lifetime of the excited molecular state. Graphical abstract

Extended analytical formulae for the perturbed Keplerian motion under low-thrust acceleration and orbital perturbations

This paper presents a collection of analytical formulae that can be used in the long-term propagation of the motion of a spacecraft subject to low-thrust acceleration and orbital perturbations. The paper considers accelerations due to: a low-thrust profile following an inverse square law, gravity perturbations due to the central body gravity field and the third-body gravitational perturbation. The analytical formulae are expressed in terms of non-singular equinoctial elements. The formulae for the third-body gravitational perturbation have been obtained starting from equations for the third-body potential already available in the literature. However, the final analytical formulae for the variation of the equinoctial orbital elements are a novel derivation. The results are validated, for different orbital regimes, using high-precision numerical orbit propagators.

On the orbital evolution of 2020 AV2, the first asteroid ever observed to go around the Sun inside the orbit of Venus

ABSTRACT The innermost section of the Solar system has not been extensively studied because minor bodies moving inside Earth’s orbit tend to spend most of their sidereal orbital periods at very low solar elongation, well away from the areas more frequently observed by programs searching for near-Earth objects. The survey carried out from the Zwicky Transient Facility (ZTF) is the first one that has been able to detect multiple asteroids well detached from the direct gravitational perturbation of the Earth–Moon system. ZTF discoveries include 2019 AQ3 and 2019 LF6, two Atiras with the shortest periods among known asteroids. Here, we perform an assessment of the orbital evolution of 2020 AV2, an Atira found by ZTF with a similarly short period but following a path contained entirely within the orbit of Venus. This property makes it the first known member of the elusive Vatira population. Genuine Vatiras, those long-term dynamically stable, are thought to be subjected to the so-called von Zeipel–Lidov–Kozai oscillation that protects them against close encounters with both Mercury and Venus. However, 2020 AV2 appears to be a former Atira that entered the Vatira orbital domain relatively recently. It displays an anticoupled oscillation of the values of eccentricity and inclination, but the value of the argument of perihelion may circulate. Simulations show that 2020 AV2 might reach a 3:2 resonant orbit with Venus in the future, activating the von Zeipel–Lidov–Kozai mechanism, which in turn opens the possibility to the existence of a long-term stable population of Vatiras trapped in this configuration.

Multi-wavelength observations of protoplanetary discs as a proxy for the gas disc mass

Recent observations of protoplanetary discs reveal disc substructures potentially caused by embedded planets. We investigate how the gas surface density in discs changes the observed morphology in scattered light and dust continuum emission. Assuming that disc substructures are due to embedded protoplanets, we combine hydrodynamical modelling with radiative transfer simulations of dusty protoplanetary discs hosting planets. The response of different dust species to the gravitational perturbation induced by a planet depends on the drag stopping time — a function of the generally unknown local gas density. Small dust grains, being stuck to the gas, show spirals. Larger grains decouple, showing progressively more axisymmetric (ring-like) substructure as decoupling increases with grain size or with the inverse of the gas disc mass. We show that simultaneous modelling of scattered light and dust continuum emission is able to constrain the Stokes number, St. Hence, if the dust properties are known, this constrains the local gas surface density, Σgas, at the location of the structure, and hence the total gas mass. In particular, we found that observing ring-like structures in mm-emitting grains requires St ≳ 0.4 and therefore Σgas ≲ 0.4 g/cm2. We apply this idea to observed protoplanetary discs showing substructures both in scattered light and in the dust continuum.

Reconstruction of f(T) gravity in the context of standard Chaplygin gas as tachyon scalar field and study of the stability against gravitational perturbation

The present paper reports a study on the [Formula: see text] gravity reconstruction scheme in the context of considering standard Chaplygin gas as tachyon scalar field model of dark energy. The solution for reconstructed [Formula: see text] gravity has been obtained from reconstructed potential and scalar field of tachyon based on the standard Chaplygin gas. It has been observed that the equation of state parameter due to the reconstructed torsion contribution to the density and pressure behaves like quintom and is consistent with the observational value of the equation of state parameter for the current universe. The reconstructed [Formula: see text] has then been tested for gravitational perturbation by deriving the frictional term, the effective mass and the sound speed parameter for the gravitational potential and it has been found to be stable against gravitational perturbations through positive value of the squared speed of sound. Finally, statefinder diagnostics has been carried out and the reconstructed [Formula: see text] gravity is found to interpolate between dust and [Formula: see text]CDM phases of the universe.