Intervening and intrinsic absorbers leave characteristic signatures on a quasar spectrum because each system removes light at wavelengths set by its own redshift and internal physical conditions. These differences reflect variations in cosmological distance, peculiar velocity, temperature and ionisation state of the absorbing gas. In this study, the spectrum of the high-redshift quasar Q1422+23 (RA 14:24:38.1, DEC +22:56:01), situated close to the bright star Arcturus, is examined with the goal of identifying and analysing triply ionised carbon (C IV) absorption systems along the line of sight. The emission redshift of the quasar is estimated to be about 3.62, placing it at a distance where metal-enriched gas associated with early galaxy formation can be probed in detail. The focus is on the C IV doublet at rest wavelengths 1548.204 Å and 1550.774 Å, a widely used tracer of highly ionised gas in both the intergalactic medium and the circumgalactic regions of galaxies. These lines provide a reliable measure of the ionisation structure and chemical content of the intervening systems. To extract accurate physical parameters, each detected feature is modelled with a Voigt profile that combines Gaussian broadening, caused by thermal motions and small-scale turbulence, with Lorentzian wings arising from natural line broadening. This approach allows a consistent determination of absorber redshift, line-of-sight velocity, cosmological distance, Doppler parameter and the relative contributions of thermal and non-thermal motions. Column densities are also derived to quantify the amount of ionised carbon in each component. The analysis reveals clear variations in redshift, velocity, width and column density among the identified absorption systems. These differences point to a diverse population of ionised structures enriched by earlier episodes of star formation and feedback. The results contribute to a better understanding of how metals are distributed and transported through the high-redshift universe and how the ionised gas evolves over cosmic time.

This study investigates the effects of adding the area and curvature terms to the volume term in the quark and gluon density of states on the transition temperature, at which the deconfinement phase transition occurs. The analysis begins with the computation of the partition function of both the Hadronic Gas (HG) and the Quark–Gluon Plasma (QGP) projected onto the SU(3) color-singlet representation, using the projection method, within the quark and gluon density of states given by the Multiple Reflexion Expansion (MRE) approximation. We consider the transition between a Hadronic Gas (HG) phase, consisting of massive pions, and a Quark–Gluon Plasma (QGP) phase, which includes gluons, massless up and down quarks, and massive strange quarks along with their antiquarks, in the framework of the Bag model and the phase coexistence model. We then examine the variations in the pressure of both the Hadronic Gas (HG) and the Quark–Gluon Plasma (QGP) phases, with the aim of determining the transition temperature in different cases of contributing terms in the quark and gluon density of states: considering the contributions of the volume term only, volume and area terms, volume and curvature terms, and the combination of the three volume, area and curvature terms.

In this study, we present an alternative framework for understanding the dynamics of late-time cosmic acceleration. Central to our research is a specific methodology for modeling the expansion history of the universe and the nature of dark energy by a logarithmic parametrization of the deceleration parameter q(z). This specific form facilitates a model-independent reconstruction of the expansion history, allowing the cosmic evolution to be determined empirically, yet it remains fully consistent with scalar-field-driven dark energy models within the framework of General Relativity.

Our theoretical structure is built upon Scalar Field Cosmology, where cosmic dynamics are governed by a minimally coupled scalar field (ϕ) possessing a generalized potential V(ϕ). This potential is meticulously designed to coherently reproduce the observed late-time acceleration phase of the universe. The logarithmic form of q(z) allows for the reconstruction of all fundamental dynamic quantities in a closed analytical form. This analytical tractability is crucial for theoretical analysis and direct comparison with observations.

To constrain the model’s free parameters, we utilized a robust and extensive set of observational data. This includes Cosmic Chronometers (CCs), high-precision Standard Candle (SC) observations from Type Ia Supernovae (specifically the Pantheon+ sample), Baryon Acoustic Oscillation (BAO) data, and the strong constraint provided by the R19 local Hubble constant prior. All datasets were meticulously combined and analyzed through a combined χ^2 minimization procedure, ensuring the maximization of the model’s observational consistency and statistical power.

The results unequivocally demonstrate a clear evolutionary transition from a past decelerating phase to the current accelerating phase. The reconstructed transition redshift (z_t) is found to lie within the interval z_t ≈ 0.70–0.90, which is remarkably consistent with modern cosmological findings. The high degree of consistency between our model and the observational data proves that the logarithmic deceleration mechanism can provide a successful explanation for the universe's evolution.

One of the unsolved mysteries in the particle physics is the "neutron decay puzzle". Discrepancies between the neutron lifetime measured in beam and bottle experiments suggest that exotic decay channels and/or the involvement of dark matter may be in play. The proposed dark decay of the neutron may explain the existence of a wide range of objects produced from the mixing of neutron stars with dark matter, , including objects with small masses and radii, as well as those in the mass gap region. This hypothesis can more generally explain the existence of other compact objects with both small masses and radii that are to the left of and below the classical MR diagrams. In particular, we consider the case of neutron decay into a dark particle of mass m_x=939 MeV according to the hypothesis formulated by Grinstein. We consider this dark matter to interact both with itself and with neutrons, thus defining the equation of state of the neutron and dark matter mixture. In this study, we found that with the appropriate combination of interaction parameters, both masses larger than 2 solar masses can be simultaneously predicted, and at the same time, the compact objects XTE and HESS can be reproduced in a self-consistent way.

The large body of observational data accumulated to date records significant discrepancies between early and late cosmological measurements. Among the most discussed cosmological parameters with existing deviations in measurements, at early and late times, for example, are the Hubble constant, H0_, and parameter S8, which characterizes the measure of growth of cosmic structure. One of the possible modifications of ΛCDM, capable of resolving the tensions H0 and S8, is associated with the development of dark energy (DE) models, in which the equation of state parameter w can influence the growth rate of the cosmological structure. Models with this property include, for example, the gas of thin tubes of a massless scalar field (TToMSF), since the parameter of its equation of state $w$ depends on the density of the gas, namely, for rarefied gas TToMSF w→-1 and for compressed gas w→1. In this case, changes in the density of the TToMSF gas, which may be associated, for example, with its gravitational interaction with non-uniformly distributed baryonic matter, during the period of baryon acoustic oscillations (BAOs), should lead to the implementation of local equations of state with different values and different laws of change of parameter w.

In this work, we investigated how the trajectories of a test null string change as it moves in the evolving gravitational field of a thin tube of a massless scalar field, and how these trajectories can influence the accelerated expansion of the TToMSF gas.

We explore the potential resolution of the so-called dark universe conundrum via the unification of the cosmological dark components, namely, dark matter (DM) and dark energy (DE), from a semi-classical fluid description of a Bose–Einstein condensate (BEC) of light bosons. Specifically, such a unification, which implies the same fundamental origin of DM and DE, has indeed been shown to be accountable from the BEC energy density, identified with the corresponding probability density, whereas the associated (Bohmian) quantum potential can account for the DE density semi-classically. The ‘macroscopic’ BEC wave-function can be chosen such that the BEC energy density resembles that of a CDM. Nevertheless, as illustrated in some of our earlier works, neither the BEC density equals the total effective CDM density, nor the quantum potential equals the total DE density, as the entire bulk of the universe contents (including the visible baryons) back-reacts on the metric structure of space–time due to the quantum-corrected Raychaudhuri–Friedmann equations. Such a quantum back-reaction crucially constrains the BEC mass, wherefrom one can infer that the BEC acts almost as an axion-like scalar field DE, rather than as a DM! However, in those works the inhomogeneous part of the BEC density has been ignored, at large scales, taking the view that it would not affect the background cosmological evolution. Examining the effect of this inhomogeneous part on large-scale cosmology of course requires standard techniques of averaging of inhomogeneities over a suitably chosen domain. The latter may conceivably be much lesser than the spread of a Gaussian, which can serve as the BEC wave-function, as shown in the earlier works. We carry out the averaging here and show that, despite having corrections to the cosmological solution obtained earlier, the BEC mass bound from the quantum back-reaction remains intact, and so does the above inference.

Background: Neutron star outer cores contain superfluid neutrons and superconducting protons. Their mutual interaction, mediated by vortex–flux-tube dynamics, affects both the rotational and magnetic evolution of the star. Understanding the structure and energetics of these topological defects is therefore relevant for models of glitch dynamics and magnetic field evolution.

Methods: We model the neutron–proton system with a two-component Ginzburg–Landau framework, treating neutrons as a neutral condensate and protons as a charged one. By solving the coupled Ginzburg–Landau equations, we obtain the modified core profiles of vortices and flux tubes and quantify how inter-species coupling alters their structure. The corresponding interaction energies are computed to characterise mixed configurations.

Results: The numerical calculations identify regimes in which vortices and flux tubes attract (i.e., display pinning behaviour) or repel, depending on the coupling parameters of the two condensates. Furthermore, we identify constraints on the choice of coupling parameters required to achieve stable configurations for this system.

Conclusions: A microscopically calibrated two-component Ginzburg–Landau model can reproduce key mesoscopic features of vortex–flux-tube interactions in the outer core. While our model is phenomenological, it shows that the resulting forces may be of sufficient magnitude to influence glitch dynamics as well as the coupled rotational–magnetic evolution of neutron stars.

Assertion of the nature and stability of solutions of field equations recast in terms of an autonomous set of variables in a so-called phase space is a crucial requirement for all dynamical systems including the cosmological
ones, particularly those which lead to an effective dark universe picture, i.e., with dark energy (DE) and dark matter
(DM), and plausible interactions thereof. The latter can be perceived naturally in the equivalent scalar-tensor
(ST) formulations of various modified gravity theories, under conformal transformations. Viable cosmologies are
indeed shown to emerge from the ST formulations for exponential type scalar field potentials in the conformal
(Einstein) frame. Keeping our attention on these potentials, we carry out a rigorous phase space analysis from
the perspective of generic exponents as well as in a specific case-by-case manner, by working out the autonomous
first-order coupled differential equations from the ST cosmological equations in the Einstein frame, after defining
suitable phase space variables. Thesecase studies turn out to be significant not only in working out numerical
solutions of the autonomous equations for the physically relevant parametric ranges (which we assert by inspection)
and in identifying the attractors in the resulting phase portraits, but also in determining which of the equilibrium
solutions change their roles to the stable ones (sink or spiral) in various sub-domains of such parametric ranges.
Finally, we demonstrate the robustness of the analysis from a precise match of the stable solutions with the exact
analytic ones, as well as from a comparison with the dynamics of the effectively non-interacting cosmological
systems, in the respective cases of fixed exponents in the scalar field potential. On the whole we make a concrete
step towards establishing stable solutions in the phase space of autonomous variables for a fairly generic scalar-
tensor cosmological system which culminates to an interacting cosmic dark sector.

Future lepton colliders provide a uniquely clean and high-precision environment to probe charged lepton flavor violation (cLFV) at energy scales far beyond the reach of current experiments. Such facilities are particularly well suited to explore flavor-violating interactions with suppressed Standard Model backgrounds and well-controlled systematic uncertainties. In this work, we investigate a broad class of LFV operators in the Standard Model Effective Field Theory (SMEFT) framework across multiple collider configurations, focusing on multi-TeV electron–positron and muon machines envisioned for the next generation of high-energy lepton programs. Our analysis incorporates realistic assumptions about detector performance, particle identification, and beam polarization, enabling an accurate characterization of both the signal and the dominant Standard Model backgrounds. We explore the interplay between center-of-mass energy, integrated luminosity, and polarization configurations in enhancing LFV sensitivity, demonstrating how different collider setups provide complementary access to operator structures and chiral couplings. In addition to a traditional cut-based approach, we evaluate the impact of multivariate techniques and optimal observable strategies in extracting maximal information from kinematic distributions. Preliminary projections indicate that next-generation lepton colliders can improve sensitivity to LFV interactions relative to indirect limits derived from rare tauon decays. These results highlight the decisive role of future lepton collider programs in establishing a comprehensive global effort to uncover new sources of lepton flavor violation and in mapping the SMEFT flavor landscape with unprecedented precision.

The increasing diversity and precision of gravitational-wave (GW) observations provide unprecedented opportunities to perform stringent tests of general relativity (GR). Although several conceptual and observational challenges motivate the development of modified theories of gravity, a crucial prerequisite is a complete understanding of all phenomena allowed within GR itself. A key result in this context is the no-hair theorem, whose classical formulation relies on the assumption of asymptotic flatness. When this assumption is relaxed, GR already admits a much richer space of solutions with additional “charges.”

In this work, we investigate asymptotically non-flat black-hole spacetimes within GR, focusing on the full Plebanski–Demianski (PD) class of algebraic type D solutions. This general family of metrics is characterized by up to seven independent parameters: mass, spin, electric charge, magnetic charge, acceleration, cosmological constant, and NUT charge. Our objective is to compute the quasi-normal modes (QNMs) of these black holes in their most general form.

Two notable subclasses—Kerr–de Sitter black holes and accelerating (C-metric) black holes—have previously been shown to yield Teukolsky equations that reduce to the general Heun equation with four regular singular points. Such equations can now be solved efficiently using Mathematica’s Heun function framework, allowing high-precision computation of QNM frequencies within seconds. Heun functions are generalizations of hypergeometric functions; they are the solutions to the general Heun equation.

We extend these results by demonstrating that the Teukolsky equation for the full PD metric also maps to the general Heun equation. Consequently, we obtain a unified method to compute QNM spectra across the entire seven-parameter family and investigate how each parameter influences the oscillation and damping frequencies.

This generalization significantly broadens the landscape of GR-consistent QNM predictions and should be taken into account when interpreting future GW observations and formulating robust tests of GR.