Deep radio continuum surveys provide fundamental constraints on galaxy evolution, but source confusion limits sensitivity to the faintest sources. We present a complete framework for producing high-fidelity deblended radio catalogs from the confused MIGHTEE maps using the probabilistic deblending framework XID+ and prior positions from deep multi-wavelength data in the COSMOS field. To assess performance, we construct MIGHTEE-like simulations based on the Tiered Radio Extragalactic Continuum Simulation (T-RECS) radio source population, ensuring a realistic distribution of star-forming galaxies and active galactic nuclei (AGN) for validation. Through these simulations, we show that prior catalog purity is the dominant factor controlling deblending accuracy: a high-purity prior, containing only sources with a high likelihood of radio detection, recovers accurate flux densities and reproduces input source counts down to $\sim 3σ$ (where $σ= $ thermal noise). On the other hand, a complete prior overestimates the source counts due to spurious detections. Our optimal strategy combines the high-purity prior with a mask that removes sources detected above $50~μ$Jy. Applied to the $\sim$1.3\,deg$^2$ area of the MIGHTEE-COSMOS field defined by overlapping multi-wavelength data, this procedure yields a deblended catalog of 89,562 sources. The derived 1.4\,GHz source counts agree with independent P(D) analyses and indicate that we resolve the radio background to $\sim 4.8\,μ$Jy. We also define a recommended high-fidelity sample of 20,757 sources, based on detection significance, flux density, and goodness-of-fit, which provides reliable flux densities for individual sources in the confusion-limited regime.

We present the characterization of the TOI-6041 system, a bright ($V = 9.84 \pm 0.03$) G7-type star hosting at least two planets. The inner planet, TOI-6041b, is a warm Neptune with a radius of $4.55^{+0.18}_{-0.17}\,R_\oplus$, initially identified as a single-transit event in \textit{TESS} photometry. Subsequent observations with \textit{TESS} and \textit{CHEOPS} revealed additional transits, enabling the determination of its $26.04945^{+0.00033}_{-0.00034}$~d orbital period and the detection of significant transit timing variations (TTVs), exhibiting a peak-to-peak amplitude of about 1~hour. Radial velocity (RV) measurements obtained with the APF spectrographs allow us to place a $3σ$ upper mass limit of $28.9\,M_\oplus$ on TOI-6041b. In addition, the RV data reveal a second companion, TOI-6041c, on an 88~d orbit, with a minimum mass of $0.25\,M_{\mathrm{Jup}}$. A preliminary TTV analysis suggests that the observed variations could be caused by gravitational perturbations from planet c; however, reproducing the observed amplitudes requires a relatively high eccentricity of about 0.3 for planet c. Our dynamical stability analysis indicates that such a configuration is dynamically viable and places a $1σ$ upper limit on the mass of TOI-6041c at $0.8\,M_{\mathrm{Jup}}$. An alternative is the presence of a third, low-mass planet located between planets b and c, or on an inner orbit relative to planet b -- particularly near a mean-motion resonance with planet b -- which could account for the observed variations. These findings remain tentative, and further RV and photometric observations are essential to better constrain the mass of planet b and to refine the TTV modeling, thereby improving our understanding of the system's dynamical architecture.

This study investigates ion kinetic effects during the parametric decay instability (PDI) of parallel-propagating Alfvén waves under plasma conditions characteristic of the Earth's ionosphere. By using a series of hybrid particle-in-cell simulations, we examine the evolution of ion velocity distribution functions (VDFs) in ultra-low-beta plasmas. Our numerical campaign systematically explores the dependence on key parameters (plasma beta, pump-wave amplitude and polarization, and ion composition). To emphasize the role of kinetic effects, we choose to trigger the PDI with a dispersive mother wave with wavelength comparable to the ion characteristic inertial length. Our results reveal pronounced nonthermal VDF modifications, including parallel heating and the formation of secondary ion beams, linked to the nonlinear evolution of parametric decay instability. By varying the plasma beta and the pump-wave amplitude, we identify a critical regime where rapid and complete broadening of the velocity distribution function is observed, triggering bidirectional ion acceleration. Notably, simulations modeling realistic ionospheric conditions demonstrate that even low-amplitude Alfvénic perturbations can induce significant VDF spreading and ion beam generation, with hydrogen ions exhibiting stronger effects than oxygen. These nonthermal microscopic processes offer a plausible mechanism for particle precipitation in space weather events. This work represents the first comprehensive study with hybrid simulations of PDI-driven ion kinetics in ultra-low-beta plasmas, providing quantitative estimates for the time delay between electromagnetic wave impact and ion VDF modification and new insights into wave-particle interactions that may contribute to ion acceleration, precipitation processes and space plasma dynamics.

We develop an accurate and computationally efficient emulator to model the gravitational lensing magnification probability distribution function (PDF), enabling robust cosmological inference of point sources such as supernovae and gravitational-wave observations. We construct a pipeline utilizing cosmological $N$-body simulations, creating past light cones to compute convergence and shear maps. Principal Component Analysis (PCA) is employed for dimensionality reduction, followed by an eXtreme Gradient Boosting (XGBoost) machine learning model to interpolate magnification PDFs across a broad cosmological parameter space ($Ω_m$, $σ_8$, $w$, $h$) and redshift range ($0.2 \le z \le 6$). We identify the optimal number of PCA components to balance accuracy and stability. Our emulator, publicly released as ace_lensing, accurately reproduces lensing PDFs with a median Kullback-Leibler divergence of $0.007$. Validation on the test set confirmed that the model reliably reproduces the detailed shapes and statistical properties of the PDFs across the explored parameter range, showing no significant degradation for specific parameter combinations or redshifts. Future work will focus on incorporating baryonic physics through hydrodynamical simulations and expanding the training set to further enhance model accuracy and generalizability.

We quantify galaxy correlations using two distinct three-dimensional samples from the first data release of the Dark Energy Spectroscopic Instrument (DESI): the Bright Galaxy Sample (BGS) and the Luminous Red Galaxy Sample (LRGS). Specifically, we measure the conditional average density, defined as the average density of galaxies observed around a typical galaxy in the sample. To minimize boundary effects, we adopt a conservative criterion: only galaxies for which a spherical volume of radius $r$, centered on them, is fully contained within the survey footprint are included in the computation. For the BGS, we construct four volume-limited subsamples in order to eliminate biases arising from luminosity-dependent selection effects. By contrast, the LRGS is approximately volume-limited by design. The resulting samples span different depths, providing an opportunity to test the stability of statistical measurements across survey volumes of increasing size. Our results show that the conditional average density follows a power-law decay, $\langle n(r) \rangle \propto r^{-0.8}$, without exhibiting any transition to homogeneity within the survey volume. The large statistics of the DESI samples also allow us to demonstrate that finite-size effects become significant as $r$ approaches the boundaries of the sample volumes. Consistently, we find that the distribution of density fluctuations follows a Gumbel distribution - characteristic of extreme-value statistics - rather than a Gaussian distribution, which would be expected for a spatially homogeneous field. These findings confirm and extend the trends previously observed in smaller redshift surveys, supporting the conclusion that the galaxy distribution does not undergo a transition to spatial homogeneity within the probed scales, up to $r \sim 400$~\text{Mpc}/$h$.

We introduce a novel analytical approach for studying free-fermion (XX) chains with smoothly varying, site-dependent hoppings and magnetic fields. Building on a discrete WKB-like approximation applied directly to the recurrence relation for the single-particle eigenfunctions, we derive a closed-form expression for the local fermion density profile as a function of the Fermi energy, which is valid for arbitrary fillings, hopping amplitudes and magnetic fields. This formula reproduces the depletion and saturation effects observed in previous studies of inhomogeneous free-fermion chains, and provides a theoretical framework to understand entanglement entropy suppression in these models. We demonstrate the accuracy of our asymptotic formula in several chains with different hopping and magnetic field profiles. Our findings are thus the first step towards an analytical treatment of entanglement in free-fermion chains beyond the reach of conventional field-theoretic techniques.

This work analyses vacuum magnetic field topology in Wendelstein 7-X (W7-X) with respect to changes in the current in the superconducting coils. We develop a fast automated scheme to locate fixed points (such as X- and O-points) and calculate the trace of the Jacobian of the field line map for them (Tr(M)), which represents several important properties of the fixed point. We perform two sets of coil current scans: (1) scans where each coil current is varied individually, using the "standard", "high iota" and "low iota" configurations as starting points; (2) a scan of over 200,000 magnetic configurations in which the coil currents are randomly sampled. In both cases we constrain the coil currents to the normal range of W7-X. We verify the principal roles of the non-planar, planar and control coils: the non-planar coils establish island chains with a certain phase; the planar coils modify the location of the island chain by both controlling the iota profile and shifting the configuration "inward" and "outward"; the control coil affects the island size and phase. We also find that |Tr(M)-2| (a quantity closely related to the magnitude of the Greene's residue) tends to increase with the minor radius of the fixed points, and that Tr(M) for X- and O-points can be very differently affected by the control coil current. Finally, we show that |Tr(M)-2| serves as a proxy for island size for internal island chains, which may help identification of suitable experimental candidates.

Classical Cepheids are among the most important distance calibrators thanks to the correlation between their period and luminosity, and play a crucial role in the calibration as the first rung of the extragalactic distance ladder. Given their typical age, they also constitute an optimal tracer of the young population in the Galactic disc. We performed a complete spectroscopic analysis of 136 spectra obtained from three different high-resolution spectrographs, for a total of 60 DCEPs. More than half have pulsational periods longer than 15 days, up to 70 days, doubling the number of stars in our sample with P>15d. We derived radial velocities, atmospheric parameters, and chemical abundances for up to 33 different species. We present an updated list of trusted spectroscopic lines for the detection and estimation of chemical abundances. We used this new set to revisit the abundances already published in the context of the C-MetaLL survey and increase the number of available chemical species. For the first time (to our knowledge), we present the estimation of abundances for Cepheids for dysprosium, as well as a systematic estimation of erbium, lutetium, and thorium abundances. We calculated a galactic radial gradient for [Fe/H] with a slope of -0.064 pm 0.002 dex kpc-1, in good agreement with recent literature estimation. The other elements also exhibit a clear negative radial trend, with this effect diminishing and eventually disappearing for heavier neutron-capture elements. Depending on the proposed spiral arms model present in several literature sources, our most external stars agree on tracing either the Perseus, the Norma-Outer, or both the Outer and the association Outer-Scutum-Centaurus arms.

Modelling of large-scale structure is increasingly concerned with galaxy assembly bias (GAB), the dependence of galaxy clustering on quantities other than halo mass. We investigate how baryonic physics affects the strength and redshift evolution of GAB using the largest runs of two state-of-the-art cosmological hydrodynamical simulations: SIMBA and IllustrisTNG. We quantify GAB by comparing the clustering of stellar-mass-selected galaxies to that of shuffled samples, where galaxies are randomly reassigned to haloes of similar mass. We find that GAB in both simulations increases from approximately zero at $z=5$ to a $\sim\,5\%$ change in clustering amplitude at $z=2$. After this epoch, the trends diverge: GAB in TNG continues to increase, reaching $\sim\,10\%$ at $z=0$, while in SIMBA it decreases to nearly zero. By further shuffling galaxies within bins of halo mass and cosmic environment -- characterised by smoothed matter overdensity ($δ_5$) and tidal anisotropy ($α_5$) -- we show that most of the GAB in both simulations can be attributed to the overdensity, while tidal anisotropy contributes negligibly in both simulations. Exploring this effect from the point of view of the halo occupation distribution (HOD), we find that numbers of central and satellite galaxies vary with overdensity -- but only near the respective turn-on masses for these two constituents: the galaxy contents of high-mass haloes are very nearly independent of environment. We present a simple parameterisation that allows the HOD modelling to be modified to reflect this form of density-dependent GAB.

We present a stack of data from the second season of the CO Mapping Array Project (COMAP) Pathfinder on the positions of quasars from eBOSS and DESI. COMAP is a Line Intensity Mapping (LIM) experiment targeting dense molecular gas via CO(1--0) emission at $z\sim3$. COMAP's Season 2 represents a $3\times$ increase in map-level sensitivity over the previous Early Science data release. We do not detect any CO emission in the stack, instead finding an upper limit of $10.0\times 10^{10}\ \mathrm{K\ km\ s^{-1}\ pc^2}$ at 95\% confidence within an $\sim 18\ \mathrm{cMpc}$ box. We compare this upper limit to models of the CO emission stacked on quasars and find a tentative ($\sim 3 σ$) tension between the limit and the brightest stack models after accounting for a suite of additional sources of experimental attenuation and uncertainty, including quasar velocity uncertainty, pipeline signal loss, cosmic variance, and interloper emission in the LIM data. The COMAP-eBOSS/DESI stack is primarily a measurement of the CO luminosity in the quasars' wider environment and is therefore potentially subject to environmental effects such as feedback. With our current simple models of the galaxy-halo connection, we are thus unable to confidently rule out any models of cosmic CO with the stack alone. Conversely, the stack's sensitivity to these large-scale environmental effects has the potential to make it a powerful tool for galaxy formation science, once we are able to constrain the average CO luminosity via the auto power spectrum (a key goal of COMAP).

Hubble constant tension, together with the recent indications of dynamical dark energy proposed from the Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation (BAO) measurements, poses significant challenges to the standard cosmological model. We investigate the possible redshift evolution of dark energy and the Hubble constant through a data-driven approach, and assess whether such evolution can alleviate the Hubble constant tension. We perform a model-independent reconstruction of the dark-energy equation of state $w(z)$, jointly with an evolving Hubble constant $H_0(z)$. The analysis combines the DESI DR2 BAO dataset with multiple Type Ia supernova samples and evaluates the statistical preference for the reconstructed model using Bayesian evidence. The reconstructed $w(z)$ varies with redshift and exhibits two potential phantom crossings at $z\sim0.5$ and $z\sim1.5$. Meanwhile, $H_0$ decreases continually from local to high redshift, alleviating the Hubble constant tension effectively. The joint $w(z)$-$H_0(z)$ model is favored over the $w$CDM ($Λ$CDM) framework, with a logarithmic Bayes factor $\ln \boldsymbol{\mathcal B}= 5.04~(8.53)$. The results remain stable under different prior choices and dataset combinations. Our data-driven reconstructions suggest redshift evolution in both $w(z)$ and $H_0(z)$, offering a potential route to mitigate the Hubble constant tension. Future BAO measurements from Euclid and next-generation CMB experiments will provide critical tests of these results and bring deeper insights into the nature of dark energy and the evolution of cosmic expansion.

Cosmological models where dark matter interacts with dark energy via a pure momentum transfer and with no energy exchange (i.e. elastic) provide compelling scenarios for addressing the apparent lack of structures at low redshift. In particular, it has been shown that measurements of $S_8$ may show a statistically significant preference for the presence of elastic interactions. In this work we implement a specific realisation of these scenarios into an $N$-body code to explore the non-linear regime. We include two populations of particles to describe the interacting dark matter and the non-interacting baryons respectively. On linear scales we recover the suppression of structures obtained from Boltzmann codes, while non-linear scales exhibit an enhancement of the matter power. We find that fewer massive halos are formed at low redshift as a consequence of the elastic interaction and that dark matter halos are more compact than in the standard model. Furthermore, the ratio of dark matter and baryons density profiles is not constant. Finally, we corroborate that baryons efficiently cluster around dark matter halos so they provide good tracers of the dark matter velocity field despite the presence of the interaction. This shows that the interaction is not sufficiently strong as to disrupt virialised structures.

Gas giant planets orbiting low-mass stars are uncommon outcomes of planet formation. Increasing the sample of well-characterised giants around early M dwarfs will enable population-level studies of their properties, offering valuable insights into their formation and evolutionary histories. We aim to characterise giant exoplanets transiting M dwarfs identified by TESS. High-resolution spectroscopic data are obtained in the optical and nIR, combining HARPS and NIRPS. We derive RVs via the cross-correlation function and implement a novel post-processing procedure to further mitigate telluric contamination in the nIR. The resulting RVs are jointly fit with TESS and ground-based photometry to derive the orbital and physical parameters of the systems. We confirm two gas giants transiting the low-mass stars TOI-3288 A (K9V) and TOI-4666 (M2.5V). TOI-3288 A hosts a Hot Jupiter with a mass of $2.11\pm0.08~M_{\rm Jup}$ and a radius of $1.00 \pm 0.03~R_{\rm Jup}$, with an orbital period of 1.43 days ($T_{\rm eq} = 1059 \pm 20~{\rm K}$). TOI-4666 hosts a $0.70_{-0.06}^{+0.05}~M_{\rm Jup}$ warm Jupiter ($T_{\rm eq} = 713 \pm 14~{\rm K}$) with a radius of $1.11 \pm 0.04~R_{\rm Jup}$, and an orbital period of 2.91 days. We identify a decrease in planetary mass with spectral type, where late M dwarfs host less massive giant planets than early M dwarfs. More massive gas giants that deviate from this trend are preferentially hosted by more metal-rich stars. Furthermore, we find an increased binarity fraction among low-mass stars hosting gas giants, which may play a role in enhancing giant planet formation around low-mass stars. The observed population trends agree with theoretical expectations, where higher metallicity can compensate for lower disk masses, and wide binary systems may influence planet formation and migration through Kozai-Lidov cycles or disk instabilities.

K2-18b lies near the radius valley that separates super-Earths and sub-Neptunes, marking a key transitional regime in planetary and atmospheric composition. The system offers a valuable opportunity to study how M-dwarf high-energy stellar radiation influences atmospheric stability and the potential for sustaining volatile species, especially important in the context of the upcoming ELT and its ANDES spectrograph. This study characterizes the high-energy environment of K2-18 with X-ray observations from eROSITA, the soft X-ray instrument on the Spectrum-Roentgen-Gamma (SRG) mission, Chandra, and XMM-Newton. We derive a representative 0.2-2 keV X-ray flux with an APEC thermal plasma model fitted with the Bayesian X-ray Analysis (BXA). With the observed X-ray flux from the exoplanet host star, we estimate the photoevaporative mass loss of exoplanet K2-18b using the energy-limited model. In addition, we examine the thermal structure of the system based on a hydrodynamic model. In 100 ks XMM-Newton observation we identified K2-18 as a very faint X-ray source with $\mathrm{F_X = 10^{-15}\ erg\,s^{-1}\,cm^{-2}}$, with an activity level of (Lx/Lbol) $\sim 10^{-5}$. A small flare has been detected during the observation. The planet is irradiated by an X-ray flux of $\mathrm{F_{pl,X} = 12\pm3\ erg\,s^{-1}\,cm^{-2}}$. The X-ray flux measurement of K2-18 gives important limitations for atmospheric escape and photochemical modeling of its exoplanets. Despite its near orbit around an M-dwarf star, K2-18b's low activity level environment suggests that it can retain an atmosphere, supporting recent tentative detections of atmospheres.

The Little Red Dot (LRD) paradigm comprises three main unknowns that are intrinsically connected: (1) What is the nature of these sources? (2) How do they form? (3) How do they evolve? Larger spectroscopic samples and high-resolution data are needed to delve deeper into the mechanisms ruling these sources. Understanding their formation and evolution requires identifying the rise and fall of the key features that characterize these systems, such as their compactness and ''V''-shaped spectral energy distributions. In this work, we present a galaxy system nicknamed The Stingray that was identified in the Canadian NIRISS Unbiased Cluster Survey (CANUCS). This group contains three sources at $z_{\mathrm{spec}} = 5.12$, including an active galactic nucleus (AGN), a Balmer break galaxy, and a star-forming satellite. The latter resembles a Building Block System in which interactions boost stellar mass and black hole mass growth beyond what is expected from secular processes alone. The AGN in this system exhibits features indicative of a transitional object, bridging a normal AGN and an LRD phase. These are a blue rest-frame ultraviolet slope, compact size, and a broad H$α$ line (all of which are characteristic of LRDs), but a flatter rest-frame optical slope compared to that observed in LRDs. The features in this source point to the emergence or fading of an LRD, potentially triggered by environmental effects.

We use Pauli Path simulation to variationally obtain parametrized circuits for preparing ground states of various quantum many-body Hamiltonians. These include the quantum Ising model in one dimension, in two dimensions on square and heavy-hex lattices, and the Kitaev honeycomb model, all at system sizes of one hundred qubits or more -- sizes at which generic quantum circuits are beyond the reach of exact state-vector simulation -- thereby reaching utility scale. We benchmark the Pauli Path simulation results against exact ground-state energies when available, and against density-matrix renormalization group calculations otherwise, finding strong agreement. To further assess the quality of the variational states, we evaluate the magnetization in the x and z directions for the quantum Ising models and compute the topological entanglement entropy for the Kitaev honeycomb model. Finally, we prepare approximate ground states of the Kitaev honeycomb model with 48 qubits, in both the gapped and gapless regimes, on Quantinuum's System Model H2 quantum computer using parametrized circuits obtained from Pauli Path simulation. We achieve a relative energy error of approximately $5\%$ without error mitigation and demonstrate the braiding of Abelian anyons on the quantum device beyond fixed-point models.

We present a search for $z\simeq7$ Lyman-break galaxies using the $1.72 \, \rm{deg}^2$ near-infrared UltraVISTA survey in the COSMOS field, reaching $5\,σ$ depths in $Y$ of 26.2. We incorporate deep optical and Spitzer imaging for a full spectral energy distribution (SED) fitting analysis. We find 289 candidate galaxies at $6.5\leq z \leq 7.5$ covering $-22.6 \leq M_{\rm UV} \leq -20.2$, faint enough to overlap with Hubble Space Telescope studies. We conduct a separate selection by including complementary Euclid performance verification imaging (reaching $5\,σ$ depths of $26.3$), yielding 140 galaxies in $0.65 \, \rm{deg}^2$, with 38 sources unique to this sample. We compute the rest-frame UV luminosity function (UV LF) from our samples, extending below the knee ($M^*=-21.14^{+0.28}_{-0.25}$). We find that the shape of the UV LF is consistent with both a Schechter function and double-power law (DPL) at the magnitudes probed by this sample, with a DPL preferred at $M_{\rm UV}<-22.5$ when bright-end results are included. The UltraVISTA+Euclid sample provides a clean measurement of the LF due to the overlapping near-infrared filters identifying molecular absorption features in the SEDs of ultra-cool dwarf interlopers, and additional faint galaxies are recovered. A comparison with JWST LFs at $z>7$ suggests a gentle evolution in the bright-end slope, although this is limited by a lack of robust bright-end measurements at $z>9$. We forecast that in the Euclid Deep Fields, the removal of contaminant ultra-cool dwarfs as point sources will be possible at $J_{\rm E} < 24.5$. Finally, we present a high-equivalent-width Lyman-$α$ emitter candidate identified by combining HSC, VISTA, and Euclid broadband photometry, highlighting the synergistic power these instruments will have in the Euclid Auxiliary Fields for identifying extreme sources in the Epoch of Reionisation.

The black hole in the Galactic Center, Sgr A*, is prototypical for ultra-low-fed galactic nuclei. The discovery of a hand-full of gas clumps in the realm of a few Earth masses in its immediate vicinity provides a gas reservoir sufficient to power Sgr A*. In particular, the gas cloud G2 is of interest due to its extreme orbit, on which it passed at a pericenter distance of around 100 AU and notably lost kinetic energy during the fly-by due to the interaction with the black hole accretion flow. 13 years prior to G2, a resembling gas cloud called G1, passed Sgr A* on a similar orbit. The origin of G2 remained a topic of discussion, with models including a central (stellar) source still proposed as alternatives to pure gaseous clouds. Here, we report the orbit of a third gas clump moving again along (almost) the same orbital trace. Since the probability of finding three stars on close orbits is very small, this strongly argues against stellar-based source models. Instead, we show that the gas streamer G1-2-3 plausibly originates from the stellar wind of the massive binary star IRS16SW. This claim is substantiated by the fact that the small differences between the three orbits - the orientations of the orbital ellipses in their common plane as a function of time - are consistent with the orbital motion of IRS 16SW.

SymBoltz is a new Julia package for solving the linear Einstein-Boltzmann equations in cosmology. It features a symbolic-numeric interface for specifying equations, is free of approximation switching schemes, and is compatible with automatic differentiation. Cosmological models are built from replaceable physical components in a way that scales well to extended models, or alternatively written as one compact system of equations. The modeler provides their equations, and SymBoltz solves them while reducing friction in the modeling process. Symbolic knowledge enables powerful automation of tasks, such as separating computational stages (e.g., background and perturbations), generating analytical and sparse Jacobian matrices, and interpolating arbitrary variables from the solution. Implicit solvers integrate the full stiff equations at all times without approximations, which greatly simplifies the code. Performance remains comparable to existing approximation-based codes due to efficient high-order implicit methods, fast generated code, optimal handling of the Jacobian, and sparse matrix methods. Automatic differentiation gives exact derivatives of any output with respect to any input, which is important for gradient-based Markov chain Monte Carlo (MCMC) sampling in large parameter spaces, Fisher forecasting, emulator training, and sensitivity analyses. The main features form a synergy that reinforces the design of the code. Output spectra agree with established codes up to 0.1% with standard precision levels. More work is needed to implement additional features and for fast reverse-mode automatic differentiation of scalar loss functions. SymBoltz is publicly available with single-command installation and extensive documentation. We welcome all contributions to the code from the community.

GRAVITY+ improves by orders of magnitude the sensitivity, sky-coverage and contrast of the Very Large Telescope Interferometer (VLTI). A central part of this project is the development of Gravity Plus Adaptive Optics (GPAO), a dedicated high-order and laser-guide star Adaptive Optics (AO) system for VLTI. GPAO consists of four state-of-the-art AO systems equipping all 8m-class Unit Telescopes (UTs) for the wavefront correction of the VLTI instruments. It offers both visible and infrared Natural Guide Star (NGS) and Laser Guide Star (LGS) operations. The paper presents the design, operations and performances of GPAO. We illustrate the improvement brought by GPAO with interferometric observations obtained during the commissioning of the NGS mode end-2024. These science results include the first optical interferometry observations of a redshift $z\sim4$ quasar, the spectroscopy of a cool brown-dwarf with magnitude $K\sim 21.0$, the first observations of a Class I young star with GRAVITY, and the first sub-micro arcsecond differential astrometry in the optical. Together with the entire GRAVITY+ project, the implementation of GPAO is a true paradigm shift for observing the optical Universe at very high angular resolution.

The escape of Lyman-$α$ (Ly$α$) radiation encodes valuable information on the neutral interstellar medium and is often used as a proxy for the escape of ionizing photons. Yet, the theory of Ly$α$ transfer through anisotropic gas distributions remains underdeveloped. We present Monte Carlo radiative transfer simulations of Ly$α$ propagation through porous, inhomogeneous neutral gas, systematically exploring the effects of channel geometry, outflows, dust, and lognormally distributed column densities. We find that Ly$α$ photons do not preferentially escape through the lowest-column-density pathways, but instead traverse channels of substantial optical depth, leading to suppressed central flux and the absence of strongly beamed escape. Subdividing channels has little impact, indicating that geometry and covering fraction are more important than porosity. Channels containing moderate amounts of neutral hydrogen alter escape in characteristic ways, including the appearance of quadruple-peaked spectra, which can be captured by a simple flux-channel relation. Outflows reshape the spectra by facilitating escape through dense media, redshifting photons and blending central features, while dust modulates the visibility of small channels by suppressing flux at line center; in both cases, we develop an analytical model that predicts the resulting central fluxes. Extending to lognormal column density fields, we show that Ly$α$ photons probe a broad range of optical depths, producing skewed spectra that can be approximated by weighted sums of homogeneous models. Our results have direct implications for using Ly$α$ as a tracer of gas properties and ionizing photon escape; for instance, spectra suggestive of high column densities may nonetheless allow LyC leakage through narrow channels.

RUBIES-UDS-QG-z7 (RQG) is the earliest massive quiescent galaxy identified to date, inferred to have formed its abundant stellar mass in a single burst that ceases rapidly before $z\sim8$. An object of such extreme nature challenges our understanding of galaxy formation, requiring rapid growth and quenching mechanisms only $0.6 \ \rm{Gyr}$ after the Big Bang and implying number densities $2 \ \rm{dex}$ higher than currently predicted by simulations. We use synthetic observables to identify analogous systems within the First Light And Reionisation Epoch Simulations (FLARES) and find two massive galaxies ($M_{\ast}>10^{9} \ \mathrm{M_{\odot}}$) dominated by rapidly quenched bursts. One of these demonstrates excellent agreement with the inferred physical properties of RQG and implies a number density of analogous systems $\log_{10}(\mathrm{N_{Q}} \ / \ \mathrm{Mpc}^{-3}) = -7.92^{\ +0.52}_{\ -0.76}$. Beyond demonstrating that the current FLARES model is capable of producing RQG-like systems, these analogues provide a laboratory within which to study the underlying physics. Their active galactic nuclei (AGN) heat and expel gas, inducing rapid quenching and preventing timely rejuvenation. This causes above-average chemical enrichment at a given stellar mass, with super solar levels predicted for RQG. These metallicities are underestimated by spectral energy distribution fitting and we show that $α$-enhancement cannot be solely responsible. Degeneracies with age and dust attenuation appear the more likely causes. Tensions between observed and simulated number densities can be alleviated in part by considering systematics, but adjustments to AGN feedback, such as allowing super-Eddington accretion rates, may be required for full agreement.

We propose a causality-based divide-and-conquer algorithm for nonequilibrium Green's function calculations with quantics tensor trains. This algorithm enables stable and efficient extensions of the simulated time domain by exploiting the causality of Green's functions. We apply this approach within the framework of nonequilibrium dynamical mean-field theory to the simulation of quench dynamics in symmetry-broken phases, where long-time simulations are often required to capture slow relaxation dynamics. We demonstrate that our algorithm allows to extend the simulated time domain without a significant increase in the cost of storing the Green's function.

We study Carrollian contractions of $W_N$-algebras from a free-field perspective. Using a contraction of the Miura transformation, we obtain explicit free-field realizations of the resulting Carrollian $W_N$-algebras. At the classical level, they are isomorphic to the Galilean $W_N$-algebras. In the quantum case, we distinguish between two Carrollian constructions: a flipped Carrollian contraction, where the time direction is reversed in one sector, and a symmetric contraction. The flipped construction yields a quantum algebra isomorphic to the Galilean one, whereas the symmetric construction produces a distinct quantum Carrollian $W_N$-algebra whose basic structure constants are identical to those of the classical Carrollian $W_N$-algebra. These algebras provide a natural framework for studying extended symmetries in Carrollian conformal field theories, motivated by recent developments in flat space holography. Our construction provides tools for developing the representation theory of Carrollian (and Galilean) $W_N$-algebras using free-field techniques.

We continue the work of Belliard, Pimenta and Slavnov (2024) studying the modified rational six vertex model. We find another formula of the partition function for the inhomogeneous model, in terms of a determinant that mix the modified Izergin one and a Vandermonde one. This expression enables us to compute the partition function in the homogeneous limit for the rectangular lattice, and then to study the thermodynamic limit. It leads to a new result, we obtain the first order of free energy with boundary effects in the thermodynamic limit.

The H-alpha (Ha) emission line in galaxies is a powerful tracer of their recent star formation activity. With the advent of JWST, we are now able to routinely observe Ha in galaxies at high redshift (z > 3) and thus measure their star formation rates (SFRs). However, using classical SFR(Ha) calibrations to derive the SFRs leads to biased results because high-redshift galaxies are commonly characterized by low metallicities and bursty star formation histories, affecting the conversion factor between the Ha luminosity and the SFR. In this work, we develop a set of new SFR(Ha) calibrations that allow us to predict the SFRs of Ha-emitters at z > 3 with minimal error. We use the SPHINX cosmological simulations to select a sample of star-forming galaxies representative of the Ha-emitter population observed with JWST. We then derive linear corrections to the classical SFR(Ha) calibrations, taking into account variations in the physical properties (e.g., stellar metallicities) among individual galaxies. We obtain two new SFR(Ha) calibrations that, compared to the classical calibrations, reduce the root mean squared error (RMSE) in the predicted SFRs by $Δ$RMSE $\approx$ 0.04 dex dex and $Δ$RMSE $\approx$ 0.06 dex, respectively. Using the recent JWST NIRCam/grism observations of Ha-emitters at z ~ 6, we show that the new calibrations affect the high-redshift galaxy population statistics: (i) the estimated cosmic star formation rate density decreases by $Δρ$(SFR) $\approx$ 12%, and (ii) the observed slope of the star formation main sequence increases by $Δ$ $\partial$log SFR / $\partial$log M* = 0.08 $\pm$ 0.02.

We exploit the most robust, old, and cosmology-independent age estimates of individual stars from Gaia DR3 to place a lower bound on the age of the Universe, $t_U$. These constraints can serve as an anchor point for any cosmological model, providing an upper limit to the Hubble constant $H_0$. We consider the stellar age catalog of arXiv:2402.00561, selecting 3,000 of the oldest and most robustly measured main sequence turn-off (MSTO) and subgiant branch (SGB) stars, with ages $>12.5$ Gyr and associated error $<1$ Gyr. Ages are derived via isochrone fitting using the Bayesian code StarHorse, spanning the uniform range 0-20 Gyr, not assuming any cosmological prior on $t_U$. With a conservative cut in the Kiel diagram, strict quality cuts both on stellar parameters and posterior shapes, and removing potential contaminants, we isolate a final sample of 160 bona-fide stars, representing the largest sample of precise and reliable MSTO and SGB stars ages available to date. The age distribution of the final sample peaks at $13.6 \pm 1.0$ (stat) $\pm 1.3$ (syst) Gyr. Assuming a maximum formation redshift for these stars of $z_f = 20$ (a formation delay of $\sim$0.2 Gyr), we obtain a lower bound on $t_U$ of $t_U \geq 13.8 \pm 1.0$ (stat) $\pm 1.3$ (syst) Gyr. Considering the $10^{th}$ percentile of each star's posterior distributions, we find that, at 90% CL (stat), 70 stars favour $t_U > 13$ Gyr, while none exceeds 14.1 Gyr. An oldest age younger than 13 Gyr for this sample is incompatible with the data, even considering the full systematic error budget. This work presents the first statistically significant use of individual stellar ages as cosmic clocks, opening a new, independent approach for cosmological studies. While this already represents a major step forward, future Gaia data releases will yield even larger and more precise stellar samples, further strengthening these constraints.

It is known that any two trees on the same $n$ leaves can be displayed by a network with $n-2$ reticulations, and there are two trees that cannot be displayed by a network with fewer reticulations. But how many reticulations are needed to display multiple trees? For any set of $t$ trees on $n$ leaves, there is a trivial network with $(t - 1)n$ reticulations that displays them. To do better, we have to exploit common structure of the trees to embed non-trivial subtrees of different trees into the same part of the network. In this paper, we show that for $t \in o(\sqrt{\lg n})$, there is a set of $t$ trees with virtually no common structure that could be exploited. More precisely, we show for any $t\in o(\sqrt{\lg n})$, there are $t$ trees such that any network displaying them has $(t-1)n - o(n)$ reticulations. For $t \in o(\lg n)$, we obtain a slightly weaker bound. We also prove that already for $t = c\lg n$, for any constant $c > 0$, there is a set of $t$ trees that cannot be displayed by a network with $o(n \lg n)$ reticulations, matching up to constant factors the known upper bound of $O(n \lg n)$ reticulations sufficient to display \emph{all} trees with $n$ leaves. These results are based on simple counting arguments and extend to unrooted networks and trees.

Building on a recent construction of Plebanek and Salguero-Alarcón, which solved the Complemented Subspace Problem for $C(K)$-spaces, and the subsequent work of De Hevia, Martínez-Cervantes, Salguero-Alarcón, and Tradacete solving the Complemented Subspace Problem for Banach lattices, we show that the class of Banach lattices is not primary. Specifically, we exhibit a compact Hausdorff space $L$ such that $C(L) \simeq X \oplus \tilde{X}$ and neither $X$ nor $\tilde{X}$ is isomorphic to a Banach lattice. In particular, it also follows that the class of $C(K)$-spaces is not primary.

Reconstructing the star formation history (SFH) of disk galaxies is central to understanding their growth and evolution, yet such estimates can be strongly biased by stellar radial migration over cosmic time. Using 186 Milky Way (MW) and Andromeda (M31) analogs from the TNG50 cosmological simulation, we compare star formation rates (SFRs) inferred from present-day stellar positions with those based on stellar birth radii to quantify the magnitude, spatial structure, and temporal evolution of migration-induced biases. We find that radial migration systematically produces artificial star formation in regions that had not yet formed stars. Notably, ~80% of galaxies exhibit outer-disk stars older than 10 Gyr, which we find to have formed at radii interior to the outer disk and to have reached their present locations via substantial outward migration. Similar effects appear in ~45% of galaxies at intermediate radii during early epochs, and in 30% of quenched inner disks within the past 4 Gyr. Migration also smooths SFHs, washing out localized bursts and suppressions by dispersing stars across neighboring radii. The strength and imprint of these distortions depend sensitively on galactic structure and evolutionary history: strong bars drive mean SFR overestimates of up to 75% in the inner disk and 150% in the outskirts; thinner, dynamically cold disks suffer average outer-disk biases up to 160%; while thick disks exhibit typical inner-disk biases up to 125%. Merger timing further modulates these patterns. Our results demonstrate that failing to account for stellar migration can lead to severe misinterpretations of when and where stars formed, with direct implications for the chemical and evolutionary histories of the MW and external galaxies.