Papers

We obtain the first derivation of the 2D Vlasov-Poisson equation for classical particles with Coulomb interactions without any microscopic cutoff. The proof relies on our recent dual hierarchical approach to mean-field limits, together with a refined analysis of dual BBGKY hierarchies on linearized correlations, based on kinetic regularization effects. The result holds more generally for arbitrary singular interaction forces $K\in L^{2-\eta}_{loc}$ with $\eta>0$ small enough, in any dimension, and it extends to Brownian particles. It holds globally in time as long as the mean-field solution is regular enough.

Non-Abelian anyons offer a route to fault-tolerant and universal quantum computing, but experimental access to their defining braiding and fusion data remains limited by the resource overhead of implementing extended anyonic processes on quantum hardware. Here we introduce and experimentally realise a measurement-only protocol based on temporally ordered ribbon operations that reconstructs the non-Abelian braiding and fusion primitives of the quantum double model $D(S_3)$ without physical anyon transport. We implement a reduced two-qutrit version of the protocol on Quantinuum's H2 trapped-ion processors, realising ancilla-assisted ribbon operations and anyonic charge projections in a qubit encoding. We reconstruct the squared braiding phases and fusion amplitudes using an adapted Hadamard test and post-selected measurements, respectively. The associated braiding and fusion transformations reproduce their ideal actions with average normalised output-state fidelities of $\overline{\mathcal{F}}_{R}=0.9988$ and $\overline{\mathcal{F}}_{F}=0.9987$. Combining these primitives produces a non-Clifford braid and a non-stabilizer resource state, supporting measurement-only anyonic encodings as building blocks for larger topologically encoded quantum processors.

We apply the two-particle irreducible (2PI) formalism as a framework for a consistent thermal resummation in studies of cosmological phase transitions. Considering a model with two mixing real scalar fields, we work within the Hartree approximation and renormalize the 2PI effective action, while introducing a connection to physical parameters. This yields the Hartree-resummed finite-temperature effective potential, which is valid for all temperatures and avoids the limitations of conventional methods based on the high-temperature approximation. With this potential, we study one- and two-step transitions within the model, and compare our results with those obtained using resummation schemes widely employed in the literature. Finally, we evaluate the gravitational wave spectrum generated from first-order phase transitions, demonstrating the impact of the choice of resummation scheme on the predicted spectrum.

We present deep, NIRSpec G140M and G395M spectroscopy of Little Red Dots (LRDs) at z = 6.68 and z = 8.35. Both LRDs show broad Balmer and [O III] $\lambda$4364 emission. The broad [O III] $\lambda$4364 lines have FWHM ~1000 km/s, about 1/3 that of the H$\beta$ lines. Assuming gas temperatures T ~ 15,000 - 25,000 K, the [O III] $\lambda$4364/[O III] $\lambda$5008 ratios of the broad lines yield high gas densities, log n/cm^-3 = 6.3 to 7.9, 3-10$\times$ higher than those in broad-line regions of low-redshift quasars. If the broad-lines trace virial motions, it is evidence for metal-enhanced gas clouds, ~1-10~pc from the LRD engine. Both LRDs show narrow [C III] $\lambda$1907 + C III] $\lambda$1909, and O III] $\lambda\lambda$1661,1666. The C III] ratios yield narrow-line gas densities, log n/cm^-3 = 4.2-5.2, similar to those in other star-forming galaxies. The line equivalent widths, EW(O III]), EW(C III]), are at, or exceed, limits expected for stellar populations, likely requiring an additional ionizing source. The LRDs also have [O III] $\lambda$4364/H$\gamma$ ratios that favor ionization from an accretion disk, possibly combined with stars. Both LRDs show nitrogen enhancement based on detections of N III] $\lambda$1746 or N IV] $\lambda$1486, which may imply rapid, recent star-formation. These results favor a scenario where the LRD gas envelopes are highly stratified, having high-density clouds with a non-unity covering factors and a complex geometry, such that ionizing radiation from the LRD accretion disk, combined with that from star-forming regions, produce the nebular emission features.

Global fits of the Standard Model Effective Field Theory are challenged by the large number of operators, while any given database constrains only a small subset. Selecting relevant operator hypotheses therefore requires theoretical insight into operator correlations and the sensitivity of observables. We present llm4smeft, an open source framework that addresses this problem by combining a language model, fine-tuned on the SMEFT literature, with retrieval augmented generation based on quantitative summaries of SMEFiT package global fits. Given a set of observables, the framework proposes candidate relevant operators together with their corresponding Fisher information, while retrieval ensures that model outputs are grounded in existing fit results whenever available. The framework runs in an interactive mode in which accepted hypotheses are stored in a growing knowledge base. We publicly release the llm4smeft package together with the fine-tuned language model, in which the entire framework runs locally, requiring neither internet access nor paid cloud services.

Generalized contextuality is known to be required in optimal strategies for quantum state discrimination protocols. More recently, sequential discrimination tasks have been studied; n players attempt to determine in which state a qubit was prepared, in such a way that they all have a finite probability of success. We consider the extent to which contextuality plays a role in sequential versions of both unambiguous and minimum error discrimination. In the standard nonsequential case where n = 1, we use the COPE formalism to demonstrate that the presence of contextuality is guaranteed not only for the optimal measurement, but for a specific set of nonoptimal measurements as well. In the sequential case n > 1, we show that the presence of contextuality depends on which states are prepared, and on the protocol (unambiguous or minimum error) selected.

The subsystem-size dependence of ground-state entanglement entropy and its crossover to thermal entropy as a function of temperature are well understood for one-dimensional (1D) gapless systems described by conformal field theory (CFT), and for free fermions with a Fermi surface in any dimension. However, little is known about the entanglement entropy for gapless fermionic systems without quasi-particles, such as a strange metal. Here we study the entanglement entropy of fermions in a solvable large-$N$ 1D lattice model akin to the Yukawa-Sachdev-Ye-Kitaev (Yukawa SYK) model. In this model, two Fermi points are coupled to scalar bosons via spatially random Yukawa interactions, providing a solvable model of a strange metal when the bosons become critical at a quantum critical point. We exactly compute the second Rényi entropy of fermions in a spatial subregion in this model. Our results unravel crucial role of intra-subregion entanglement between fermionic and bosonic degrees of freedom along with the inter-subregion entanglement in understanding the ground states of such strongly coupled fermion-boson systems. We show that the crossover from thermal entropy to entanglement entropy, is captured by a single scaling ansatz, that collapses the second Rényi entropy of fermions for different subregion sizes and temperatures into a single universal curve. We further show that the universal scaling curve for the critical strange metal is well described by the standard CFT formula, albeit with an effective central charge substantially larger than the non-interacting value.

We construct non-commutative deformations of field and gauge theories based on star-products implemented by Drinfel'd twists. We are able to encompass a large family of twists, including those built out of conformal symmetries and supersymmetries. The main idea behind our construction is to work with twists constructed from symmetries of the undeformed theory, that are realised as active symmetry transformations. We argue that our construction amounts to a reformulation of known deformations of gauge theories, and that it significantly extends the range of applicable examples. To ensure consistency with gauge invariance, we also identify a unimodularity condition that is weaker than the one that is normally employed in the literature, so that we can apply twists that would otherwise be left out. Finally, we also prove a planar equivalence theorem stating that the Feynman diagrams of the deformed theories retain an undeformed internal structure, with the twist acting only on their external legs. All these results are important to identify and work with deformations of $\mathcal N=4$ super Yang-Mills that are proposed to be dual to homogeneous Yang-Baxter deformations of the $AdS_5\times S^5$ superstring, but the applicability of our construction and results goes beyond that.

Low dimensionality enhances quantum fluctuations, triggering novel states of quantum matter to emerge. In real materials, low dimensionality usually arises from spatially strongly anisotropic couplings. Here, we demonstrate a different mechanism: in two-dimensional systems with coupled alternating ferromagnetic (FM) and antiferromagnetic (AFM) spin-$1/2$ chains, an applied magnetic field may drive a dimensional reduction. Under magnetic field, the FM chains polarize and stiffen, suppressing the propagation of transverse AFM fluctuations from one chain to another, and effectively induce one-dimensional behavior at low energies. For a model describing botallackite, Cu$_2$(OH)$_3$Br, quantum Monte Carlo dynamics show that beyond a critical magnetic field, the low-energy spectrum reduces to that of a one-dimensional AFM Heisenberg spin-$1/2$ chain with field-dependent incommensurate two-spinon fluctuations, providing clear signatures for inelastic neutron scattering.

Being agnostic about the field content of a gravitational system, we consider a general disformal transformation of the metric, $g_{\mu\nu}=C h_{\mu\nu}+D t_{\mu\nu}$, on a four-dimensional Lorentzian manifold. Using the Cayley-Hamilton theorem, we derive an explicit formula for the inverse disformed metric. Implementing the Hawking-Ellis classification, we categorize disformal transformations into four types: Type I, II, III, and IV, based on possible Jordan block structures. We further identify the Segre subclasses from the eigenvalues. We derive explicit relations between the Cayley-Hamilton degree of $t_{\mu\nu}$, its Hawking-Ellis type, and its Segre subclass, restricting the possible types from the degree alone. In some cases, the type can be determined without even performing a full Jordan decomposition. For singular transformations, when new dynamical degrees of freedom emerge, we obtain the form of their corresponding mimetic energy-momentum tensor $T^\star_{\mu\nu}$. Within the polynomial sector, the Hawking-Ellis types of $t_{\mu\nu}$ and $T^\star_{\mu\nu}$ always coincide for Type I. For Types II and III it can differ, while Type IV is preserved generically but can reduce to Type I when the complex pair is mapped to a repeated real eigenvalue. This makes it possible to infer physical properties of $T^\star_{\mu\nu}$ directly from the Hawking-Ellis type of $t_{\mu\nu}$. We apply our setup to scalar and gauge fields. We find a new pure-disformal scalar-gauge family yielding irrotational perfect fluids, including barotropic fluids with an arbitrary constant equation-of-state parameter. Two scalar fields realize all four types and the reductions from Types II and IV to Type I. This framework applies to the kinematical and dynamical study of invertible and non-invertible disformal transformations with different field content.

Packet-switched quantum networks require buffers that can delay qubit payloads while routing information is read out in real time. Previous approaches have not provided this functionality in a fully fibre-integrated architecture compatible with telecom infrastructure. Here we demonstrate an optical-fibre-integrated buffer, based on a recirculating loop and a fibre storage line, in which the storage time of a polarisation-encoded qubit payload is determined by readout of an attached packet header. The key component behind this achievement is an ultra-low-loss poled fibre phase modulator, which provides fast, polarisation-insensitive switching directly in fibre and allows header and payload to be processed within the buffer. We demonstrate storage and retrieval of polarisation-encoded qubit payloads for storage times up to 47 $\mu$s, with an average quantum bit error rate of 1.8% together with stable operation over several hours. These results establish a practical fibre-based architecture for packet-level quantum network buffering that can easily integrate into the current telecommunication infrastructure opening up new paths for deployment of the quantum internet.

We construct a set of microphysical, finite-temperature equations of state (EOSs) for numerical simulations of neutron star mergers and core-collapse supernovae that is consistent with modern constraints from nuclear theory and multimessenger astronomy and systematically spans the posterior distribution of allowed EOSs. The EOSs are based on a simplified Skyrme functional whose inputs are nuclear matter saturation properties, extended to supra-saturation densities through the speed of sound at a set of reference densities. The models are assigned continuous likelihood weights from chiral effective field theory and perturbative quantum chromodynamics calculations, the gravitational wave signal GW170817, the complete set of NICER mass-radius measurements, and the Shapiro-delay mass measurement of the radio pulsar J0348. From the resulting catalogue of 5.2 million EOSs, the posterior yields $R_{1.4} = 11.8^{+0.8}_{-0.7}$ km, $\Lambda_{1.4} = 334^{+193}_{-113}$, and $M_{\rm max}^{\rm TOV} = 2.18^{+0.22}_{-0.14}\,M_\odot$ (medians with 90% credible intervals). From this posterior we select a ranked 12-member ensemble, headed by a fiducial, central EOS, whose members are individually plausible while jointly bracketing the posterior spread of neutron-star observables. For all ensemble members we generate general-purpose finite-temperature tables with the SROEOS code, each accompanied by nucleon effective-mass variants that bracket the ensemble's thermal-sector uncertainty, to be made publicly available upon publication.

Moving a detector through a beam with a spatially varying energy spectrum exposes the same target and apparatus to distinct incident spectra, enabling interaction spectroscopy. While movable neutrino detectors were put forth primarily to control systematic uncertainties, we show that detector motion enables probing the structure of fundamental interactions. We demonstrate this with the Intermediate Water Cherenkov Detector (IWCD), the movable detector of Hyper-Kamiokande in the J-PARC off-axis beam, considering neutrino non-standard interactions (NSI) as a benchmark. Exploiting ratios of neutral current to charged current event rates reduces common normalization uncertainties, while measurements at multiple off-axis positions can break degeneracies that persist for a single incident spectrum. Combining three off-axis positions and adopting a $5\%$ correlated normalization uncertainty benchmark, we project $95\%$ CL sensitivities to axial neutral current NSI of $-0.07 \lesssim \varepsilon^{uA}_{\mu\mu} \lesssim 0.06$ and vector NSI of $-0.10 \lesssim \varepsilon^{uV}_{\mu\mu} \lesssim 0.12$, as well as for charged current NSI of $-0.05 \lesssim \varepsilon^{udL}_{\mu\mu} \lesssim 0.05$. Axial NSI, which do not contribute to the ordinary matter potential, are complementary to neutrino oscillation and high energy scattering measurements. More broadly, detector motion provides a new way to distinguish interactions with different energy dependence.

Structured light has emerged as a promising resource for high-capacity and secure free-space optical communication, where atmospheric turbulence remains a major source of signal degradation. In this work, we investigate the resilience of different transverse mode structures of an optical beam with respect to the random action of turbulence. A spatial light modulator (SLM) is programmed to apply amplitude and phase modulation corresponding to the desired transverse mode, which is then transmitted through a turbulent medium emulated by a second SLM. Laguerre-Gauss, Hermite-Gauss, and Airy beams are investigated through the resulting intensity distributions measured with a camera. Different figures of merit are used to evaluate and compare the resilience of these modes.

Native noise processes in quantum processors are often difficult to isolate because multiple error mechanisms contribute to the same measured loss of coherence. Here we use dephasing-robust quantum noise spectroscopy to identify and characterize control noise induced by axial motion in an individually-addressed trapped-ion processor. When the ion motion is transverse to the addressing beam, thermal axial motion couples to the beam profile and produces effective amplitude control noise. We show that this noise is governed primarily by the local beam curvature and appears as a low-frequency contribution to the reconstructed control-noise spectrum. By varying the ion position within the beam profile, we separate curvature-dependent axial-motion noise from curvature-independent native control noise and extract motional parameters that are otherwise difficult to access on this platform. We also apply the protocol in parallel to a four-ion register, demonstrating a spectroscopic method for simultaneous characterization of position-dependent control noise across multiple qubits. The results of this study identify beam inflection points as operating regions that suppress axial-motion-induced noise at the cost of reduced Rabi rate, as found in PRX Quantum 3, 010334 (2022).

Na I D absorption is widely used to estimate the dust extinction toward Galactic and extragalactic sources, but the inferred column densities are unreliable once the lines saturate. We present an analytical framework for estimating column densities from the equivalent widths ($EW$s) of absorption-line doublets. The method requires only that the two doublet members be measured separately – the velocity structure need not be resolved – so a resolving power $\lambda/\Delta\lambda\gtrsim10^{3}$ suffices for Na I D, two orders of magnitude below velocity-resolved methods. For the Gaussian curve of growth, the classical inversion reduces to a universal saturation correction depending only on the doublet ratio, $R=EW_2/EW_1$: at fixed $R$, the inferred column density is linear in the measured $EW$. The formulation yields the exact Gaussian inversion, $N_{\tilde\kappa}$, which provides the Doppler parameter; a closed-form second-order approximation; and a strict lower bound, $N_{\rm min}$, valid for an arbitrary velocity structure. We recommend reporting $N_{\rm min}$: an optimal, assumption-free lower bound, within a few per cent of $N_{\tilde\kappa}$ for $R\gtrsim1.4$ and at most a factor $3.5$ below it at $R=1.1$. The ratio $N_{\tilde\kappa}/N_{\rm 2nd}$ provides a per-object saturation diagnostic. We validate the framework against published profile-fitting Na I D column densities toward Type Ia supernovae, using only the integrated $EW$s. An explicit closed-form formula converts the two $EW$s into an extinction estimate through the observed $\log N(\mathrm{Na\,I})$–$A_V$ relation. A public implementation with full uncertainty propagation accompanies the paper.

We present a novel approach to predicting plane-of-sky velocities of cold gas clouds in the circumgalactic medium (CGM) of galaxies. The method uses a convolutional neural network (CNN) trained on simulated emission maps derived from the TNG50 cosmological simulation, with forward modeled noise properties consistent with upcoming observational facilities. Using 182 Milky Way/Andromeda analog galaxies, we generate emission maps in H$\alpha$ using $\texttt{Cloudy}$ models, as well as line-of-sight averaged 2D velocity maps. Using a UNet architecture, we train the CNN to take emission maps as input and return plane-of-sky velocity maps as output, which cannot be observationally constrained using traditional methods. Qualitatively, the model is generally able to infer the true overall flow direction. We quantify the effects of Gaussian noise on the network's training and predictive power. At depths expected to be probed by forthcoming telescopes such as MOTHRA, the network has a typical RMS error for the plane-of-sky velocity direction of $0.3-0.5 v_{vir}$. This implies that 2D emission maps of sufficient depths will be able to estimate two additional phase space dimensions of cold CGM gas, enabling targeted followup and a better understanding of overall CGM flows.

Jupiter's upper atmosphere provides a real-world laboratory for validating first-principles models of giant gaseous exoplanets and for constraining the key physical processes that govern them. We extended the 1D first-principles thermo-chemical planetary upper atmosphere model Kompot to simulate hydrogen-rich atmospheres of giant exoplanets and benchmarked it against the archetype giant planet Jupiter. We modelled a longitudinal and latitudinal average thermal and chemical profile of Jupiter's upper atmosphere by solving the equations of energy balance, photochemical kinetics, hydrodynamics, and vertical transport in a 1D radial atmospheric grid. The thermal properties of the upper atmosphere were determined by a balance between heating from solar X-ray and ultraviolet (XUV), and infrared (IR) radiation, thermal conduction, Joule heating, and radiative cooling due to H3+ and CH4. The model results were compared with Jupiter observations from Galileo, JUNO, and other instruments. The simulation results were also used as input in the radiative transfer module of the TauREx code to simulate Jupiter's infrared transmission spectrum. Our model reproduces Jupiter's observed upper-atmospheric thermal structure and observed CH4 volume mixing ratios. The chemical abundances of other gases also exhibit strong agreement with observations and existing photochemical models. Heating and cooling results show that Joule heating is the dominant heating source throughout most of the upper atmosphere. The transmission spectrum indicates the rich presence of CH4 in the near- and mid-IR wavelength ranges. Our physically consistent model framework for Jupiter's upper atmosphere provides a validated baseline for future self-consistent simulations of the thermal and chemical structure of a diverse population of hydrogen-rich exoplanet atmospheres.

Long-term instabilities in astrophysical fluids are inherently nonlinear, where even small-amplitude perturbations can trigger dramatic instability. However, owing to the complex interactions among non-normal modes, the perturbation structures responsible for the greatest growth remain poorly understood. In this paper, we employ the nonlinear optimization method known as the conditional nonlinear optimal perturbation (CNOP) to identify the most dangerous initial velocity perturbation, i.e., the perturbation that maximizes the kinetic energy growth in the two-dimensional compressible Rayleigh-Taylor instability in astrophysical hydrodynamics. Compared with random perturbations, the optimal perturbation forms a coherent wave-packet structure localized around the density interface. We investigate its dependence on spatial resolution and optimization time horizon through two sets of numerical experiments. For a fixed optimization time, increasing the spatial resolution produces a more sharply localized wave packet, whereas for a fixed spatial resolution, increasing the optimization time causes the wave packet to become progressively more dispersed. Furthermore, we analyze the optimal perturbations in Fourier space using the fast Fourier transform (FFT), which provides a clearer characterization of the spectral distribution. Higher-resolution simulations concentrate most of the perturbation energy into only a few dominant modes, while longer optimization times distribute the energy over a broader range of modes. These results indicate that short optimization time horizons involve relatively weak modal interactions and remain closer to the linear regime, whereas longer optimization times enhance nonlinear modal interactions, broaden the spectral distribution, and reduce the predictive capability of linear stability theory.

We study a $\mathscr{PT}$-symmetric non-Hermitian multichannel Kondo model consisting of a pair of spin-$\frac12$ impurities coupled to $n$ conduction-electron channels through complex-conjugate Kondo couplings. The impurity renormalization-group (RG) flow is characterized by the Kondo scale $T_K$ and a dimensionless non-Hermiticity parameter $\alpha$. As $\alpha$ increases, the exact Bethe Ansatz solution exhibits four impurity phases: overscreened Kondo, zero mode, Yu–Shiba–Rusinov (YSR), and local moment. The Kondo, zero-mode, and local-moment phases are $\mathscr{PT}$-unbroken, whereas the YSR phase spontaneously breaks $\mathscr{PT}$ symmetry. Using a generalized thermodynamic Bethe Ansatz, we determine the impurity free energy and Affleck–Ludwig $g$-function throughout the $\mathscr{PT}$-unbroken phases. In the Kondo phase, the defect RG flow connects the ultraviolet and infrared conformal fixed points, with the impurity entropy flowing from $2\ln2$ to $2\ln\left[2\cos\left(\frac{\pi}{n+2}\right)\right]$, in agreement with defect conformal field theory. In the zero-mode phase, zero-energy impurity strings reorganize the spectrum into multiple excitation towers, while in the local-moment phase, the RG flow becomes cyclic, returning to the unscreened local-moment fixed point. We conjecture that RG irreversibility, and hence a generalized Affleck–Ludwig $g$-theorem, survives throughout the Kondo phase. Our exact solution nevertheless shows that a real spectrum and defect entropies consistent with defect CFT do not guarantee RG irreversibility: the impurity entropy is non-monotonic in both the zero-mode and local-moment phases.

We study the ultimate quantum limit of rotation sensing with a few strongly interacting bosons confined in a quasi-one-dimensional ring trap with two weak links. It is demonstrated that a self-consistent many-body solution of the problem is required to correctly predict the ultimate sensitivity of this strongly correlated many-body gyroscope to rotation. For both small rotation velocities and small particle numbers, the many-body quantum Fisher information becomes maximal for large interaction couplings, showing the potential of strongly interacting miniaturized many-body sensors to precisely estimate slow rotations with high spatial resolution.

The scale of Neutral Atom (NA) quantum computers requires automated compilation tools. Designing the required heuristic methods demands a deep understanding of complex hardware trade-offs, for which visualizations can provide crucial insights. This work introduces NAViz, the first publicly available app to visualize quantum computations on NA devices in real-time. A case study demonstrates how NAViz was instrumental in identifying and resolving inefficiencies in an existing compilation strategy, leading to a new, more performant one. The tool is available as part of the Munich Quantum Toolkit (MQT) at https://github.com/munich-quantum-toolkit/naviz.

I study constraints from consistent complex factorisation of $2\rightarrow 2$ scattering amplitudes in $4d$ and their relationship with supersymmetry. I complete the argument demonstrating that a massless helicity-$3/2$ particle must be a gravitino in a theory of supergravity and derive the structure and couplings of massive supermultiplets from first principles. For massive BPS particles in theories with extended supersymmetry, further constraints on the couplings are derived from consistent factorisation of massive superamplitudes. Among these is the requirement that BPS vector bosons must have couplings conforming to Lie algebra structure constants or generalised Chern-Simons terms. The gravitational coupling is shown to participate and draws the graviphotons into the Lie algebra. All $2\rightarrow 2$ tree-level amplitudes of massive particles with spin $s\leq 1$ are calculated in (super)gravity using on-shell methods and the double copy. These are assembled and decomposed into (super)amplitudes with varying amounts of supersymmetry. Finally, I study scattering of BPS gravitinos with unbroken $\mathcal{N}\geq 4$ supergravity and show that consistent factorisation leads to the full reconstruction of the super-Higgs mechanism. This argument completely determines the perturbative structure of all $\mathcal{N}=4$ Minkowski vacua of gauged maximal supergravity. Gravitinos in theories not admitting a super-Higgs mechanism are ruled-out.

We investigate an analytically tractable sector of the Extended Cuscuton model, a non-dynamical dark-energy realization within the framework of viable Horndeski gravity. We focus on four benchmark submodels and constrain them with current background probes, namely cosmic chronometers, Type-Ia supernovae, and BAO, while imposing theoretical viability, Lunar Laser Ranging, and Big Bang Nucleosynthesis bounds. We then forecast third-generation bright-standard-siren constraints with Einstein Telescope and Cosmic Explorer networks, considering prompt-emission, afterglow, and kilonova counterparts. Current data already restrict the viable parameter space to small departures from $\Lambda$CDM and do not remove the calibration-driven offset between the CC+SN and CC+BAO determinations of $H_0$. In principle, future bright sirens substantially sharpen the constraints, especially for kilonova catalogues and extended detector networks. Across the forecast configurations, the relative uncertainty on $H_0$ remains below $13.18\%$ and can reach $0.21\%$ in the most constraining cases, while $\Omega_\Lambda$ is recovered at the percent level in the best cases. These results show that third-generation standard sirens can provide a precise complementary test of non-dynamical dark energy beyond $\Lambda$CDM.

We present the selection and identification of high-z radio quasars from a combination of X-ray (eROSITA All-Sky Survey), optical/NIR (DECam Local Volume Exploration), and radio (Rapid ASKAP Continuum Survey) surveys. After building a sample of 68 new high-z quasar candidates, we performed follow-up spectroscopic observations on 46 sources, confirming 39 to have redshifts z>3.5. For the subset of radio quasars at z>4, the 14 new sources identified here represent an increase of $\sim$65% in the known population of objects above the same flux limits in the same area. Using X-ray-to-optical relative intensity, we identified blazars in our sample, which we then used to compare the total number of z>4, X-ray selected blazars to the predictions of a fractional IC/CMB model previously proposed in the literature. Overall we find a relatively good agreement, even considering the potential biases in the redshift distribution from the incompleteness of the spectroscopic follow-up and the blazar classification criteria. The sources presented in this work represent a sample well suited for investigating the evolution of the most extreme systems in the early Universe, including their relativistic jets and accretion properties

In this work, we investigate the possibility of interpreting the $D_{s1}(2700)$ as a $P$-wave $DK^{*}$ hadronic molecular state through a systematic study of its strong decay properties. Using the effective Lagrangian approach, we calculate the strong decay widths of the $D_{s1}(2700)$ into the two-body final states $DK$, $D^{*}K$, $D_s\eta$, and $D_s^{*}\eta$, as well as the three-body $D\pi K$ channel. The coupling of the $D_{s1}(2700)$ to its constituents, $DK^{*}$, is constrained by the available experimental measurement of $R_{D_{s1}} =\Gamma(D_{s1}(2700) \to D^{*}K)/\Gamma(D_{s1}(2700)\to DK)=0.91\pm0.13\pm0.12$. With the resulting coupling, the total decay width can be readily obtained and is found to be in good agreement with the experimental measurement, providing strong support for interpreting the $D_{s1}(2700)$ as a $P$-wave $DK^{*}$ molecular state. The experimentally unobserved $D_{s1}(2700)\to D_s^{*}\eta$ decay channel provides a further test of this interpretation, as its predicted sizable decay width differs significantly from the conventional quark model prediction.

We point out that the asymptotically Bertotti-Robinson multi-black hole solutions of Einstein-Maxwell theory can be constructed using only three-dimensional sigma-model techniques, without resorting to the monodromy-matrix approach.

In Jewish tradition, the boundary between days is not midnight, but nightfall. Nightfall is when one must pray ma'ariv, count the omer, and may engage in activity after Shabbat. While there are slightly different definitions of nightfall for Shabbat restrictions (Motsa'ei Shabbat) versus other purposes (Ts'eit HaKokhavim), most minhagim define nightfall to be when three stars of some specified size and proximity are visible in the sky. This definition presents some difficulty. Not only are these conditions difficult to define, they are further complicated by weather, cloud cover, and light pollution. Observant Jews therefore usually approximate these times by defining nightfall to be when the sun has reached a certain distance below the horizon. Although these approximations have been effective, modern astronomy enables us to calculate precisely when these conditions are met. This work applies these techniques to calculate the time of Ts'eit HaKokhavim and Motsa'ei Shabbat evaluates the accuracy of the approximations, and explores the effects of light pollution on these times. While Ts'eit HaKokhavim is reasonably well-approximated by standard methods, the conditions for Motsa'ei Shabbat generally occur after the time predicted by the approximations. Light pollution does not shift Ts'eit HaKokhavim by more than a minute but significantly changes Motsa'ei Shabbat. In fact, light pollution causes the conditions of Motsa'ei Shabbat to never be met on at least some nights in every population center. Finally, I provide a tool (halakhic-nightfall.streamlit.app) for calculating Ts'eit HaKokhavim and Motsa'ei Shabbat at an arbitrary time and location on Earth.

General Relativity (GR) can be effectively examined in the low-velocity, weak-field limit, where its inherently tensorial structure simplifies to a vector-based formulation closely analogous to classical electrodynamics. This correspondence becomes particularly clear when both theories are expressed within a field-free, interaction-based framework, in which the leading relativistic corrections emerge naturally as velocity- and acceleration-dependent modifications to the static interaction. As a result, several predictions of GR can be derived using familiar techniques from electrodynamics, provided the relevant phenomena remain within the regime of validity of the approximation. This structural analogy facilitates a conceptual understanding of GR enabling the introduction of its core ideas even in an introductory level course, the single exception being the treatment of radiation, which requires tools at more advanced level. Building on this pedagogical framework, the incorporation of special relativity (SR) and the equivalence principle enables concise and transparent derivations of gravitational time dilation, as well as its immediate consequences, including light deflection and gravitational frequency shifts. A detailed exposition of this material is provided in the supplementary material.

If two solid particles collide, charge is exchanged. However, this transfer is not restricted to the surface of the particle. Ions are also dispersed into the environment. They form a charge cloud around the particle. In this way, all particle-laden atmospheres from volcanic plumes on Earth over exoplanet atmospheres to protoplanetary disks might be subject to gas-phase ionization by means of particle collisions. In laboratory experiments, we quantify the amount of ions produced in a collision of glass beads with 2.8 mm diameter. We extract the ions by applying an external electrostatic field and measuring the generated current. The ions are detected at all the pressures studied, i.e. from 0.3 mbar to 100 mbar. However, the ionization rate peaks at about 1 mbar. Scaled to individual bouncing collisions, charge as high as 1 pC of each polarity was detected. This implies collisions of grains can be a significant source of ions in various atmospheres.