Mesoscale and Nanoscale Physics
Real-space Imaging of Quantum Hall Quasiparticles
Jinghao Deng, Yiming Sun, Dimitri Pimenov et al. (+4 more)
Quantum Hall systems host emergent quasiparticles with unusual charge,
spin, and statistics, such as fractionally charged anyons. Although transport measurements have revealed many of their collective properties, identifying and visualizing individual quasiparticles remain elusive. Here we use scanning tunneling spectroscopy (STS) to image
quantum Hall quasiparticles in
graphene. Within incompressible
quantum Hall states, we observe spatial variation of Landau level energies originating from electrostatic potentials created by charged defects in
graphene and the underlying hexagonal boron nitride (hBN). For surface and near-surface defects, the Coulomb potential lifts the degeneracy of Landau orbitals, producing discrete energy splittings that reveal Landau orbital wavefunctions. In
quantum Hall ferromagnetic states, quasiparticles bound to defect potentials produce distinct spatial and spectroscopic signatures that serve as hallmarks of the presence and number of localized excitations. In the fractional
quantum Hall regime at one-third filling, our theoretical calculations predict discrete spectroscopic changes associated with the sequential addition of localized anyons, with a three-anyon bound state quantitatively reproducing our experimental data at $\nu = 5/3$. These observations establish spectroscopic fingerprints of
quantum Hall quasiparticles and provide a pathway toward imaging and manipulating individual anyons in real space.
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All authors Jinghao Deng, Yiming Sun, Dimitri Pimenov, Takashi Taniguchi, Kenji Watanabe, Erich J Mueller, Xiaomeng Liu
High Energy Astrophysical Phenomena
The kinetic-energy bottleneck in Fast Radio Burst models
Paz Beniamini and Pawan Kumar
Most Fast
Radio Burst (FRB) models invoke a two-step process in which energy released by the central engine is converted into particle kinetic energy and subsequently radiated as coherent GHz emission. We derive model-independent constraints on this picture and apply them to the three main classes of FRB models. (i) Inner-magnetospheric models violate brightness-temperature and kinetic-luminosity limits unless particles are continuously re-accelerated in situ. Magnetar-strength fields can provide the required parallel electric field out to $R\lesssim10^{10}\mathrm{cm}$. Monster shocks provide continuous acceleration but, under a single-pass kinetic-energy interpretation, require extreme particle densities and predict emission well above GHz frequencies. Even mechanisms that bypass the kinetic bottleneck through conservative wave conversion remain subject to charge availability, which independently limits magnetospheric GHz production to $\lesssim 10^{10}$ cm for fiducial parameters. (ii) Light-cylinder forced-reconnection naturally provides continuous acceleration, but typically converts only $\lesssim10^{-6}$ of the injected energy into
radio emission. (iii) External-shock maser models satisfy the kinetic-luminosity and brightness-temperature constraints, but the upstream wind is unavoidably optically thick to induced Compton scattering, independent of the model's principal parameters. Proposed escape routes - emission above the maser peak or upstream magnetization $\sigma_{\rm w}\gtrsim30$ imply very low efficiencies, while the former also conflicts with narrow FRB spectra. We conclude that near-surface magnetospheric models with continuous particle acceleration remain the most promising scenario, provided the radiation can escape the magnetosphere.
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High Energy Physics (Phenomenology)
Gravitational ultra-relativistic freeze-out during general reheating
Mathieu Gross, Stephen E. Henrich and Fotis Koutroulis
We investigate ultrarelativistic freeze-out (UFO) in the context of generic reheating scenarios. While the standard WIMP dark matter paradigm has been extensively studied, UFO has so far only been analyzed within the specific reheating channel $\phi \rightarrow f\bar{f}$. Unlike in the standard WIMP mechanism, where dark matter can only be diluted after freeze-out at $T_\mathrm{FO} \sim m_\chi/\mathcal{O}(10)$, UFO dark matter can undergo freeze-in like phases following the initial freeze-out, driven by the non-trivial temperature
evolution. The exact temperature
evolution then needs to be accounted for, as a change in the temperature scaling can modify the IR/UV nature of UFO, impacting the relic abundance. We first generalize UFO to an arbitrary temperature profile $T \sim a^{-\xi}$, making explicit the UV and IR regimes for a thermally averaged cross section $\langle \sigma v \rangle \sim T^n / \Lambda^{n+2}$. Then, as a concrete example, we consider the minimal scenario in which gravitational particle production at the onset of reheating sources an initial radiation abundance, and show that this early hot bath changes the UFO parameter space. We refer to this effect as GUFO. Specializing to $n = 2$, we find that matter-like reheating ($V \sim \phi^2$) accommodates dark matter masses up to $10^7~\mathrm{GeV}$ for $\Lambda \lesssim 10^9~\mathrm{GeV}$ as thermalization becomes less stringent, while radiation-like reheating ($V \sim \phi^4$) is compatible with GUFO across all reheating channels only if gravitational processes are taken into account.
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High Energy Physics (Theory)
A Cosmological BCFW Bridge and Its Canonical Geometry
Aswini Bala, Sachin Jain and Vibhor Singh
We build a BCFW-like recursion for cosmological correlators using the orthogonal Grassmannian. The key step is a bridge deformation that leaves all the Grassmannian constraints intact. The recursion relations are purely algebraic and avoid any spectral or radial integrals that usually appear in curved space. We obtain the
gluon 4-point correlator using this bridge, producing two factorization poles, a total energy singularity coming from the three point building block, and a shifted energy singularity that emerges only after adding the two channels using recursion. We then show that the helicity stripped four-
gluon correlator has the canonical form of a rectangle, where its boundaries represent various poles. We also describe the geometry of the
gluon correlator in the Pfaffians as the natural coordinates in the Grassmannian. Using multiple deformation bridges, we also obtain the graviton four point correlator and observe a double-copy like relation at the level of the four point function, away from the physical cuts for each channel. We also extended the BCFW bridge formalism to the supersymmetric Grassmannian.
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Cosmology and Nongalactic Astrophysics
The swallowed spike: the formation of light primordial black hole structures around heavy seeds
Agnese Tolino, Francesca Scarcella, Bradley J. Kavanagh et al. (+2 more)
Spikes are steep enhancements in the dark matter (DM) distribution around a heavy compact object. If the compact object is
primordial, and the bulk of the DM is also composed of (lighter)
primordial compact objects, for instance asteroid-mass
primordial black holes (PBHs), the phenomenology of spike formation is highly non-trivial. In fact, lighter PBHs have negligible angular momentum at formation with respect to the massive central object and would therefore be captured unless enough torque is exerted from either small-scale or large-scale matter fluctuations. In this paper, we present the first comprehensive assessment of this scenario. We define the mechanisms and the initial conditions that allow light PBHs to avoid capture. We then quantify the different types of torque and follow the corresponding angular momentum
evolution with a combination of analytical prescriptions and numerical simulations. We find that in the innermost region no mechanism studied here is capable of providing enough torque; the resulting inner core is expected to be significantly less dense than in particle scenarios, potentially leading to interesting phenomenology.
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All authors Agnese Tolino, Francesca Scarcella, Bradley J. Kavanagh, Valentina De Romeri, Daniele Gaggero
High Energy Astrophysical Phenomena
Formation of Black Hole-White Dwarf X-ray Binaries in Globular Clusters
William Y. W. Yang, Kyle Kremer, James C. Lombardi et al. (+2 more)
Globular clusters are host to significant populations of dynamically-active
stellar remnants that connect to a variety of astrophysical sources. Using simulations performed with the Cluster Monte Carlo dynamics code, we study the formation of ultracompact binaries in which a
stellar-mass black hole accretes material from a white
dwarf companion in a sub-hour orbit. These binary systems are
prime multimessenger targets, as they can be observed as both luminous X-ray sources, and as millihertz gravitational wave sources detectable by the
Laser Interferometer Space
Antenna (LISA). We find that black hole+
giant collisions are the primary mechanism through which such systems form. We model the outcomes of these “common envelope”-like events using the smoothed particle hydrodynamics code StarSmasher, and verify these collisions yield black hole+white
dwarf binaries that enter Roche contact on sub-Gyr timescales via gravitational wave inspiral. We construct a mock catalog of local ultracompact X-ray sources and compare to candidate sources observed in globular clusters in the Milky Way (e.g., 47 Tuc X9) and external
galaxies (e.g., RZ 2109 in NGC 4472). Finally, we compute the gravitational wave strain for these sources, and show that of order one source may be resolvable in the Milky Way by LISA, representing a potentially powerful tool for observing new black holes in globular clusters.
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All authors William Y. W. Yang, Kyle Kremer, James C. Lombardi, Jr., Kristen C. Dage
Quantum Physics
Efficient Quantum Circuits for Coherent Conversion Between General First- and Second-Quantized Many-Body Representations
Jack S. Baker, Gaurav Saxena and Thi Ha Kyaw
Quantum simulation at fixed particle number admits two equivalent descriptions, a first-quantized (particle) representation and a second-quantized (occupation-number) representation. Their
quantum resource costs differ sharply across computational tasks, so the ability to convert coherently between them is valuable. We construct an explicit
unitary $Q$, with inverse $Q^\dagger$, that maps a first-quantized state to its fixed-$N$ occupation-number form while diagnosing the input's particle-exchange
symmetry. The conversion is therefore
symmetry-agnostic at the input yet fully resolved at the output, and it applies uniformly to bosonic, fermionic, and parastatistical sectors. At its foundation lies a structural identification that we place at the center of this work: the
quantum Schur transform supplied by Schur-Weyl duality is the non-abelian
Fourier transform of the commuting pair $(S_N,U(d))$, and the occupation-number representation is its weight basis, retaining only the labels shared by both factors, the irrep $\lambda$ and the $\mathfrak{u}(d)$ weight. This reduction is lossless for
bosons and
fermions, while a canonical Gelfand-Tsetlin promise renders it one-to-one for the remaining sectors. Algorithmically, $Q$ composes the strong Schur transform with reversible arithmetic that computes occupations as successive row-sum differences of the Gelfand-Tsetlin pattern, yielding gate complexity $\mathrm{poly}(N,d,\log(1/\epsilon))$. The converted state is prepared efficiently in
quantum memory. Any classical
algorithm that outputs it explicitly, however, pays a cost set by the sector dimension, which is
polynomial of degree $N$ in $d$ at fixed $N$ and exponential in $N$ when $d=\Theta(N)$. Finally, an efficient classical sampler for the induced occupation-number distribution would yield one for arbitrary
quantum circuits, contrary to standard complexity assumptions.
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Astrophysics of Galaxies
Constraining the Physical Properties of Quadruply Lensed Quasars using Optical-to-X-Ray Data
Kriti Kamal Gupta, Dominique Sluse, Maarten Baes et al. (+5 more)
Gravitational
lensing of luminous active
galactic nuclei (AGN; or
quasars) can be used as a natural
telescope to zoom in on their inner structures. With more and more lensed AGN being discovered, it is extremely important to have a homogeneous study focused on constraining their key physical properties, especially the bolometric luminosity. The primary limitation for such a study is the availability of observations for a representative sample of lensed AGN in at least the optical, ultraviolet (UV), and X-ray bands, where most of the AGN emission is concentrated. In this paper, we present one of the largest multiwavelength studies of lensed AGN with the aim of accurately measuring some of the fundamental quantities, such as their bolometric luminosities, black hole masses, and Eddington ratios. We compiled photometric and spectroscopic data in optical/UV and X-rays, for 27 quadruply lensed AGN ($0.6 < z < 3.1$) and calculated their bolometric luminosities by fitting their broadband spectral energy distributions (SEDs) with phenomenological models. We also performed spectral emission line fitting to estimate their black hole masses using the virial method. Additionally, we compared different prescriptions to calculate the bolometric luminosities of AGN from limited data, and our results show that the luminosity-dependent 2-10 keV X-ray bolometric corrections provide unbiased and reliable predictions of the bolometric luminosity, with a maximum scatter of $\sim 0.5$ dex. The predictions from optical bolometric corrections are generally overestimated but show a lower scatter once microlensing effects are taken into account. Thanks to the compiled optical/UV and X-ray data for our lensed AGN sample, we also present the well-known UV-X-ray luminosity relation for AGN as a novel way to determine uncertainty in the magnifications of lensed AGN induced by micro- and/or millilensing.
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All authors Kriti Kamal Gupta, Dominique Sluse, Maarten Baes, Daniel Gilman, Tommaso Treu, Timo Anguita, Ryan Keeley, Pritom Mozumdar
High Energy Physics (Phenomenology)
Fermion mass relations in one-parameter modular models
Salvador Centelles Chuliá, Xueqi Li, Xiang-Gan Liu et al. (+2 more)
Modular flavour
symmetries provide a possible organizing principle for the Standard Model Yukawa sector, by replacing generic couplings with a potentially small number of modular forms controlled by a single complex modulus. We study the extreme limit of this idea: One-Parameter Models, in which each charged-
fermion mass
matrix is fixed by a single modular invariant contraction. We develop a systematic method to construct such models, showing that the One-Parameter Model requirement is already highly constraining at the level of possible
fermion hierarchies. In a concrete realization, the charged-
lepton and down-
quark sectors are controlled by the common modulus, leading to exact mass relations at the flavour scale, $m_s^5 = 2\sqrt{2}\,m_d^3m_b^2, \qquad m_\mu^3 = \sqrt{2}\,m_e m_\tau^2, \qquad m_s^2m_\tau = \sqrt{2}\,m_e m_b^2$. We show that, once renormalization-group
evolution and selective supersymmetric threshold effects are included, these high-scale relations can be made compatible with low-energy charged-
fermion data. Our results provide a working proof of principle for One-Parameter Models and point towards a possible route to the flavour puzzle through highly constrained constructions.
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All authors Salvador Centelles Chuliá, Xueqi Li, Xiang-Gan Liu, Omar Medina, J. T. Penedo
Astrophysics of Galaxies
WaveDM.jl: An Adaptable Simulation Framework for Dynamics of Baryonic and Wave Dark Matter on Galaxy Scales
Runyu Meng and Xiaobo Dong
We present WaveDM$.$jl, an open-source Julia package for high-performance simulations of wave dark matter dynamics on
galaxy scales, with a design philosophy centered on extensibility and adaptability. The code solves the time-dependent Schrödinger–Poisson equation (SPE) using a pseudo-spectral
Fourier method. The spectral solver is tightly integrated with N-body gravitational force solvers, enabling simultaneous
evolution of wave dark matter and baryonic components in
galaxy-scale simulations. WaveDM$.$jl unifies shared-
memory, distributed-
memory, and GPU execution within a multi-level parallelization framework, enabling the same computational workflow to scale from single-node to multi-node computing environments without requiring major code changes. To further facilitate user-friendly
galaxy-scale simulations, the package provides a dedicated toolbox that integrates flexible initial condition generators, trajectory lookback,
tidal force calculations, and real-time visualization. Beyond astrophysical applications, the code's modular architecture and general nonlinear Schrodinger framework enable cross-disciplinary studies such as nonlinear optics and cold-atom physics. The code is open source and available on https://github$.$com/JuliaAstroSim/WaveDM$.$jl.
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Astrophysics of Galaxies
Investigating black hole accretion and feedback self-regulation in Seyfert galaxies using the FIRE-3 cosmological hydrodynamic simulations
Jonathan Mercedes-Feliz, Daniel Anglés-Alcázar, Jose Cevallos et al. (+12 more)
Recent observations of local Seyfert
galaxies show an intriguing connection between Active
Galactic Nuclei (AGN) luminosity and a deficit of molecular gas on ~50pc scales compared to 200pc, the plausible imprint of AGN feedback. Motivated by these findings, we investigate the interplay between supermassive black hole (BH)
accretion, AGN feedback, and
nuclear gas reservoirs using high-resolution cosmological hydrodynamic simulations implementing FIRE-3 multi-phase interstellar medium (ISM) physics and multi-component BH
accretion and feedback models. Focusing on the late-time
evolution of four Milky Way-mass
galaxies, we find recurrent cycles of increased gas inflow toward the
accretion disc, enhanced BH
accretion, feedback self-regulation, and suppressed gas inflow rate until the next fueling event. AGN winds interact with the ISM and escape preferentially through low-density polar channels after opening central cavities on ~10-500pc scales, regulating BH growth and producing episodic behaviour on ~10-100Myr timescales. The simulations reproduce the observed diversity of
nuclear morphologies, gas concentrations, and AGN luminosities in late-type Seyfert
galaxies, but do not exhibit a clear anti-correlation between gas concentration and AGN luminosity. Higher-luminosity AGN ($L_X$~$10^{41.5-43}$ erg s$^{-1}$) powered by the
accretion disc reservoir can coexist with feedback-driven cavities, consistent with observations, but they are more common in simulated
galaxies with centrally-peaked gas distributions. Although differences in sample selection, tracer choice, spatial resolution, and stochasticity in AGN fueling may impact underlying concentration-luminosity trends, the apparent tension between simulations and observations points to the timing between gas inflow,
accretion-disc depletion, and feedback-driven clearing on ~50-200pc scales as a key constraint on AGN self-regulation models.
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All authors Jonathan Mercedes-Feliz, Daniel Anglés-Alcázar, Jose Cevallos, Boon Kiat Oh, Santiago García-Burillo, Rachel K. Cochrane, Cristina Ramos Almeida, Claude-André Faucher-Giguère, Almudena Alonso-Herrero, Alexander J. Richings, Miguel Pereira-Santaella, Jorge Moreno, Niranjan Chandra Roy, Tanio Díaz-Santos, Philip F. Hopkins
Mesoscale and Nanoscale Physics
Local spectroscopy of anyons bound to charge traps
Jeong Min Park, Cristian Voinea, Yen-Chen Tsui et al. (+7 more)
Fractional
quantum Hall states host anyons, emergent quasiparticles with fractional charge and nontrivial exchange statistics. Controlling, trapping, and braiding anyons are central goals for both fundamental physics and topological
quantum computation. A key step toward such control is understanding how anyons behave when confined in local potentials, where their internal structure can become relevant. Here, we use the scanning tunneling microscopy/spectroscopy (STM/STS) to study the excitation spectrum in integer and fractional
quantum Hall states of monolayer
graphene near individual charged
impurities. In the integer
quantum Hall states, the STS spectra show lifting of orbital degeneracy near defects, appearing as a band of discrete energy levels. In fractional states, (v=1/3 and 2/5), however, we observe an additional energy splitting of the lowest-energy spectral feature that occurs only when the chemical potential lies within a fractional gap and is absent in compressible or integer regimes. We attribute this to many-body configurations of anyons trapped by an
impurity potential. Strikingly, numerical calculations show that the splitting requires an anisotropic confining potential, vanishing for a rotationally symmetric trap. The competing multi-anyon states carry nearly identical charge within the core of the potential but differ in how that charge is redistributed at larger radius. Our results establish local tunneling spectroscopy as a direct probe of anyon bound states, providing a key step toward understanding and controlling their behavior in confined geometries relevant for braiding and fusion.
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All authors Jeong Min Park, Cristian Voinea, Yen-Chen Tsui, Songyang Pu, Kenji Watanabe, Takashi Taniguchi, Nigel R. Cooper, Michael P. Zaletel, Zlatko Papić, Ali Yazdani
General Relativity and Quantum Cosmology
Obstructions to Minimal Regular Black Hole Cosmologies
Damien A. Easson
We derive an obstruction to Friedmann–Lemaître–Robertson–Walker (FLRW) daughter cosmologies from static, asymptotically flat regular black holes. The trapped region of such a parent is Kantowski–Sachs rather than FLRW, so the daughter must be introduced as a separate matched region. For closed daughters, the angular Darmois condition is controlled by the Misner–Sharp mass: asymptotic flatness and finite ADM mass force the induced density to decay as $A^{-3}$, while the $k=+1$
curvature term scales as $A^{-2}$. The minimal closed branch is therefore bounded rather than indefinitely expanding. Flat and open daughters avoid this boundedness mechanism. For their maximal homogeneous FLRW continuations, the regular-end affine-ANEC
theorem excludes simultaneous non-staticity,
curvature regularity, null geodesic completeness, and ANEC consistency. For Bardeen, the parent source does not naturally supply the late-time support needed for an unbounded closed daughter. Within these criteria, a viable FLRW daughter therefore requires additional structure, such as modified asymptotics, nonminimal matching, non-FLRW
evolution, or an additional stress-energy component.
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Astrophysics of Galaxies
A massive barred spiral galaxy at z = 5.102 discovered by JWST
Xiaohan Wang, Fengwu Sun, Yoshihisa Asada et al. (+21 more)
We report M1149-BSG-z5, a barred spiral
galaxy at $z = 5.102$, identified in the parallel field of MACS J1149+2223 with JWST and HST. M1149-BSG-z5 is the highest
redshift barred
galaxy candidate to date. Both isophote ellipse fitting and structural modeling support a
stellar bar of length $a_\mathrm{bar} \approx 4.5$ kpc, and extended spiral arms peaking at $r \approx 5.5$ kpc. M1149-BSG-z5 is a massive main sequence
star-forming
galaxy, with a
stellar mass of $10^{10.45}\rm M_\odot$ and a
star-formation rate of $144\,\rm M_\odot/yr$. A concentrated bulge is embedded in an extended disk with a global Sérsic index $n = 2.37$. With an effective radius of $R_{e} = 2.61\rm \ kpc$, M1149-BSG-z5 is larger than typical
galaxies at $z \sim 5$ and comparable to barred
galaxies at $2 < z < 4$. M1149-BSG-z5 also hosts a broad-line AGN, with a relatively low black-hole-to-
stellar mass ratio of $\rm M_{\rm BH}/M_\ast\sim10^{-3}$. Its metal-enriched emission-line properties indicate that it is already chemically evolved. These properties imply M1149-BSG-z5 as an early-assembled and structurally evolved
galaxy. We also find that M1149-BSG-z5 resides in an overdense region with a nearby companion
galaxy, suggesting an interaction-driven bar formation mechanism. Its concentrated light, early assembly and main-sequence
star formation also suggest
baryon-dominated, gas-rich conditions, where gravitational instability can further accelerate the bar formation.
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All authors Xiaohan Wang, Fengwu Sun, Yoshihisa Asada, Yunjing Wu, Xiaojing Lin, Shude Mao, Sijia Cai, Zheng Cai, Chian-Chou Chen, Wenlei Chen, Cheng Cheng, Christopher J. Conselice, Miroslava Dessauges-Zavadsky, Daneil Espada, Brenda L. Frye, Jean-Baptiste Jolly, Anton M. Koekemoer, Kotaro Kohno, Mingyu Li, Nicholas Martis, Hideki Umehata, Weichen Wang, Rogier A. Windhorst, Adi Zitrin
General Relativity and Quantum Cosmology
Modeling Direct Waves in Binary Black Hole Ringdowns
Richard Dyer, Adrian Ka-Wai Chung and Christopher J. Moore
Direct waves,
prompt signals propagating from a plunging object to the observer, exist alongside quasinormal modes in binary black hole ringdown. It has been suggested that the properties of the direct wave are related to the event horizon; this simplifies modeling the direct wave and suggests the possibility of using it as a new observational probe of the horizon geometry. This paradigm is tested by extracting direct waves from numerical-relativity waveforms, adapting techniques originally developed for studying quasinormal modes. The direct wave is identified over a range of ringdown start times, demonstrating the utility of the horizon mode model. However, the direct wave frequency is found to deviate from the horizon value, limiting its utility as a probe of the event horizon.
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High Energy Astrophysical Phenomena
Multi-messenger and Multi-band Studies of Massive Black Holes: the Synergies Between LISA and SKAO
Pedro R. Capelo, Alberto Mangiagli, Lorenz Zwick et al. (+2 more)
Depending on its mass, the same gas-embedded massive black hole (BH) binary can emit gravitational waves (GWs) in one or more bands (nHz and mHz) concurrently, along with electromagnetic (EM) waves over the entire spectrum. The Square Kilometre Array Observatory (SKAO), thanks to its unparalleled sensitivity, will be pivotal in achieving coincident GW-EM (mHz-
radio) and GW-GW (nHz-mHz) detections. We review the state-of-the-art predictions - achieved by means of numerical simulations and mock catalogues - of the numbers of detectable coincident GW-EM signals when employing the
Laser Interferometer Space
Antenna (LISA) and SKA-Mid. By exploiting the same underlying BH binary populations, to allow for a fairer comparison, we then assess the importance of a variety of EM models for the
radio flares and jets, finding that the number of
radio counterparts of LISA sources is relatively insensitive to the jet/
flare model employed and to whether SKA-Mid AA* or AA4 is assumed. Additionally, we describe how SKAO - as part of a
pulsar timing array (PTA) - and LISA will provide the opportunity to detect the first low-frequency, multi-band (nHz-mHz) GW detection of the same object. Supermassive BH binaries embedded in gas discs are subjected to hydrodynamical torques, causing perturbations that produce additional small-amplitude, higher-frequency GWs. The main carrier GWs may thus be identifiable as a deterministic signal by SKAO-era PTAs, while the higher-frequency harmonics would shine in LISA as
stochastic signals. Correlating these multi-band GWs would provide unprecedented constraints on the environment of the most massive BHs.
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All authors Pedro R. Capelo, Alberto Mangiagli, Lorenz Zwick, Lucio Mayer, Marta Volonteri
Nuclear Theory
Ab initio calculations of parity-violating electron scattering off $^{48}$Ca and $^{208}$Pb
Frederic Noël, Matthias Heinz, Martin Hoferichter et al. (+2 more)
Parity-violating electron scattering off
nuclei both serves as a low-energy precision probe to test electroweak interactions and allows one to access
neutron distributions inside
nuclei. It has implications for strong interactions in dense
neutron-rich environments, also providing constraints for the properties of matter in
neutron stars. Precision measurements are available for $^{48}$Ca and $^{208}$Pb by the CREX and PREX collaborations, respectively, and their interpretation requires advanced
nuclear-structure calculations to draw firm conclusions. We perform the first ab initio calculations of the parity-violating asymmetry $A_\text{PV}$ based on
nuclear forces from
chiral effective field theory, fully including corrections due to Coulomb distortion effects. Based on these results, we critically reexamine correlation analyses employed to infer weak radii and quantify the resulting tensions between ab initio and experimental results. We find that ab initio calculations prefer values of $A_\text{PV}$ slightly smaller and larger than observed for $^{48}$Ca and $^{208}$Pb, respectively, with a global significance of $1.9\sigma$. Using theoretically consistent inputs for charge and weak densities, we infer from the experimental $A_\text{PV}$ a
neutron skin of $^{208}$Pb of $R_n-R_p = 0.187(25)(18)$ fm, substantially smaller than that reported by PREX II.
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All authors Frederic Noël, Matthias Heinz, Martin Hoferichter, Takayuki Miyagi, Achim Schwenk
High Energy Astrophysical Phenomena
X-rays Mark the Spot: The Effects of Reduced Metallicity on X-ray AGN Obscuration at High Redshift
Yash A. Gursahani and Christopher S. Reynolds
The James Webb Space
Telescope has pushed the frontier of high-
redshift galaxy and active
galactic nucleus (AGN) observations firmly past $z=10$. Corresponding to the first 500 Myr after the Big Bang, this coincides with the epoch of supermassive black hole seeding and their early growth, much of which is likely to occur in highly obscured environments. In this work, we investigate the expected X-ray properties of these obscured AGNs focusing on the impact of the significantly lower iron abundance predicted at such early times. We use Monte Carlo methods to model the radiative transfer of X-rays from a central AGN through a surrounding
torus of cold gas, characterizing the emergent X-ray spectrum as a function of the
metallicity, opening angle of the
torus, and column density. Motivated by expectations of high-$z$ systems, we focus on Compton-thick obscurers with columns $N_H=10^{24}-10^{25}\,{\rm cm}^{-2}$. We find that decreased
metallicity can significantly increase the fraction of X-ray
photons that escape the
torus, improving the prospects of detecting these very high-$z$ AGNs. The covering fraction of the obscurer (i.e.
torus opening angle) plays a complex role, with repeated scatterings across the interior of the
torus (isotropizing the emission) competing with escape through the opening, producing
geometric beaming. Additionally, we explore non-
solar abundance ratios that mimic the delay-time distribution of Type Ia
supernovae. We use our models to address the detectability of highly obscured $z=10$ AGNs in next-generation, high-angular resolution X-ray surveys.
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Instrumentation and Methods for Astrophysics
Low-frequency VLBI with the SKA-Low
R. Timmerman, E. L. Escott, T. Vernstrom et al. (+2 more)
The Square Kilometre Array Observatory (SKAO) will provide unprecedented observational capabilities, revolutionizing
radio astronomy in the next decade. Of particular interest for many science areas is the low-frequency component: the SKA-Low. This array, operating at frequencies between 50 and 350 MHz, will be able to observe the Southern hemisphere with an angular resolution of several arcseconds. However, many science cases demand finer angular resolutions than the current design baseline for the SKA-Low. In this chapter, we present the Low-frequency Australian Megametre-Baseline Demonstrator Array (LAMBDA) project: the construction of a several SKA-Low-like stations throughout Australia which can be employed to extend the SKA-Low's baselines to the scale of megameters. This allows LAMBDA to not only probe the scientific opportunities accessible at higher angular resolutions, but also prove the feasibility of a potential extension of the SKA-Low to such baselines. Finally, LAMBDA also serves to characterize the performance of the SKA-Low as part of a Very Long Baseline Interferometry (VLBI) network and by providing an early testbed for the calibration strategies which would be required. With LAMBDA, the SKA-Low will be able to make a major impact in many science areas, including but not limited to
exoplanets, resolved active
galactic nuclei (AGN), young
stellar objects and
supernova remnants,
pulsar astrometry and scintillometry, gravitational
lensing and fast
radio bursts (FRBs).
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All authors R. Timmerman, E. L. Escott, T. Vernstrom, L. K. Morabito, C. Reynolds
High Energy Physics (Theory)
Lost in Translation: Moduli Stabilization from EFT to Eleven Dimensions
Iosif Bena, Raphaël Dulac, Mariana Graña et al. (+1 more)
We explicitly show how
moduli stabilization is realized geometrically in M-theory compactified on $T^4/\mathbb{Z}_2\, \times\, $K3, by using the Gibbons-Hawking approximation of the K3 metric. By relating this compactification to certain microstate geometries, we present the explicit solutions in which fully backreacted fluxes on certain four-cycles stabilize three of the $T^4/\mathbb{Z}_2$ compactification
moduli. The minimal tadpole contribution of these fluxes is linear in the number of stabilized
moduli, and we argue that this linear relation holds for more general fluxes. We also construct a one-parameter family of supersymmetric eleven-dimensional solutions that break Lorentz invariance and the warped-product structure of the compactification. These solutions are a continuous deformation of the warped-product Lorentz-invariant compactification, to which they reduce when the
moduli reach their stabilized values. Away from the Lorentz-invariant locus, the fluxes are no longer self-dual in the internal space, and include fields that do not exist in the corresponding EFT. Remarkably, although these fluxes still stabilize a modulus, it is not the $T^4/\mathbb{Z}_2$ modulus that appears stabilized in the Lorentz-invariant solution, but rather a nontrivial combination of the $T^4$ volume and K3 shape
moduli. The existence of these solutions suggests that the EFT description of
moduli stabilization can be misleading and does not reflect the
moduli-stabilization dynamics of the full eleven-dimensional theory. Our results extend straightforwardly to Type IIB String Theory compactified on orientifolds of $T^2 \times K3$.
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All authors Iosif Bena, Raphaël Dulac, Mariana Graña, Dimitrios Toulikas
High Energy Physics (Phenomenology)
Cosmological gravitational particle production in multifield inflation
Edward W. Kolb, Sarunas Verner and Jingyuan Wang
We study cosmological gravitational particle production (CGPP) of dark matter in two-field inflationary backgrounds with both flat and curved field-space geometries. As a concrete realization of broader multifield mechanisms, we adopt a Starobinsky+quadratic potential and construct
benchmark scenarios that interpolate between the flat field-space limit and the sidetracked attractor on a
hyperbolic field space, and we compute the production spectrum of a gravitationally coupled spectator scalar for both minimal ($\xi = 0$) and conformal ($\xi = 1/6$) coupling to the
Ricci scalar. We show that negative field-space
curvature can strongly enhance the post-inflationary oscillations of the
Ricci scalar, leading to an enhancement of up to an order of magnitude in the CGPP number density relative to the flat field-space limit, particularly for minimal coupling. For the sidetracked attractor, this enhanced production competes with a reduced inflationary energy scale, leading to a nontrivial dependence of the relic abundance on model parameters. We derive the relic abundance as a function of spectator mass and reheating temperature, and identify the viable parameter space for each
benchmark. The conformal case $\xi = 1/6$, whose scalar mode equation is structurally analogous to that of a massive Dirac
fermion, is much less constrained by isocurvature and provides a minimal scenario for purely gravitational dark matter production in multifield inflation.
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High Energy Physics (Phenomenology)
Probing Confining Dark Sectors with Cosmological Perturbations
Daven Wei Ren Ho, Ameen Ismail and Yuhsin Tsai
Dark matter may emerge as a composite state of a dark sector which confines in a strongly first-order phase transition (PT). To avoid structure formation constraints on warm dark matter, the dark PT must occur above the keV scale. We investigate the cosmological signatures of this scenario, focusing on a keV- to MeV-scale PT. The
stochastic nature of bubble nucleation sources
curvature perturbations that can be constrained by various cosmological observations. Composite dark matter inherits the isocurvature perturbations generated during the PT and sources large-scale
curvature perturbations. In contrast to a PT that reheats into dark radiation, the slower redshifting of dark matter enhances the infrared tail of the
curvature perturbation upon horizon entry. The PT-induced perturbations compete with the suppression of the matter power spectrum due to the free-streaming of composite dark matter. We place limits on the PT strength and temperature from
cosmic microwave background anisotropies, the Lyman-$\alpha$ forest, and other probes of the small-scale matter power spectrum. In a minimal scenario where the relic density is determined by the PT parameters, this provides a concrete example of a dark matter model that is testable via measurements of cosmological perturbations – even in the absence of a sizable nongravitational coupling to the visible sector.
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Quantum Physics
Fast and Parallel High-Rate STAR Architecture for Megaquop Quantum Simulation
Refaat Ismail, Milan Kornjača, Hong-Ye Hu et al. (+4 more)
Fault-tolerant
quantum simulation is approaching a phase where encoding overhead, logical Clifford operations, magic-state preparation, and rotation synthesis must be optimized together for efficient implementation. Space-Time efficient Analog Rotation (
STAR) architectures reduce two of these costs by preparing small-angle rotation magic states directly, and the transversal
STAR variant further lowers the Clifford overhead. Existing concrete implementations, however, largely inherit the low $O(1/d^2)$ encoding rate of the surface code, while high-rate codes have not yet been integrated into comparably explicit architectures. Here, we introduce a high-rate
STAR architecture for local
lattice Hamiltonian simulation based on a
symmetry-driven co-design of the
algorithm, QEC code, and neutral-atom hardware. Translation
symmetries of the target
lattice determine the choice of bicycle chain codes, a tunable family of self-dual bivariate bicycle codes that natively implement Clifford gates required for
lattice simulation. Disjoint logical representatives allow
STAR injections to be performed in parallel on all $k$ logical
qubits in a code block, amortizing resource state preparation and enabling practical post-selection rates. On neutral-atom platform, the same translation
symmetry compiles the key logical operations into low-depth, hardware-native acousto-optic-deflector shifts. End-to-end estimates show that an $8 \times 8$ transverse-field Ising simulation to $T^* \approx 8 (zJ)^{-1}$ requires $2240$ physical
qubits and $\sim 200$ s per shot, a $\sim 5.5\times$ space reduction relative to a surface code
STAR baseline at comparable speed; for
Fermi-Hubbard dynamics to $T^* \approx 4 (zt)^{-1}$, the corresponding estimates are $\sim 6300$ physical
qubits and $\sim 200$ s per shot. These results provide a concrete route toward early fault-tolerant
quantum simulation with high-rate codes.
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All authors Refaat Ismail, Milan Kornjača, Hong-Ye Hu, Nishad Maskara, Sheng-Tao Wang, Hengyun Zhou, Chen Zhao
Geophysics · Cross-listed from cs.LG
Geo-Strat-RL: Learning Geological Event Reasoning from Verifiable Tasks
Lukas Mosser
To evaluate whether
vision-
language models can reason about geological histories, it is necessary to construct observations for which the underlying process history is known. Furthermore,
reasoning over geological histories is not just a question of recognizing visual patterns, but also of understanding temporal and structural relationships that may be only indirectly visible or highly ambiguous. When ground-truth event histories are not uniquely identifiable or are unavailable, it remains an open challenge to teach models capable of visual
reasoning to produce valid geological reconstructions that are consistent with both observed evidence and geological principles. We therefore investigate whether defining a verifiable geological
reasoning task can improve geological event reconstruction across observation domains through reinforcement learning with verifiable rewards (RLVR). To this end, we present Geo-Strat-RL, a synthetic environment that generates stratigraphic observations and compact visible-evidence event histories. The environment combines a geological generator with an executable verifier that scores chronology, event identity, deposition, and structural relationships. We show that RLVR improves geological reconstruction in
vision-
language models (VLMs), increasing geological content scores on held out stratigraphic diagrams. We further evaluate the same held-out geological histories in a synthetic seismic observation domain by converting the generated scenes into acoustic-impedance-derived amplitude sections. In this controlled paired-renderer setting, we present evidence that geological
reasoning learned from stratigraphic diagram-domain RLVR training transfers to synthetic seismic representations without seismic-specific training examples, supporting the hypothesis that RLVR can teach reusable geological
reasoning concepts across related observation formats.
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Instrumentation and Methods for Astrophysics
Synergies Between Pulsar Timing Array and Astrometry
Gabriele Perna, Nicola Bellomo and Daniele Bertacca
The presence of a gravitational wave background can be established not only via exquisitely precise
pulsar timing array (PTA) measurements, but also via astrometric observations. In fact, the very same background responsible for the delay in the arrival time of pulse is also responsible of an apparent displacement of
galactic objects as
stars and asteroids. In this chapter we explore the natural synergy between the SKA Observatory, and current/future astrometric probes of the position of Milky Way objects. On top of presenting the potential of SKAO alone in terms of detecting a gravitational wave background, we also demonstrate the increased sensitivity that is actually achievable when SKAO measurements are used in combination with astrometric ones. In particular, we observe an approximate improvement ranging from~$10\%$ up to~$50\%$ in terms of forecast sensitivity for a PTA-astrometry joint-analysis.
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Chemical Physics
ConSolv: Solvent-Conditional Machine Learning Implicit Solvent Potential
Linying Zhang and Julija Zavadlav
Implicit solvent machine learning potentials (MLPs) offer a powerful route to bridging the gap between accuracy and efficiency in molecular simulations. However, existing models have largely focused on aqueous environments, overlooking the diverse and important roles of non-aqueous solvents in areas such as organic synthesis and battery technology. Here, we present ConSolv, a solvent-conditional MLP architecture that explicitly incorporates solvent effects on solute interactions through an
attention-based solvent-
embedding block. By combining experimental solvation free energy data with ab initio data, we train a single implicit solvent MLP that is transferable across 66 common organic solvents. ConSolv outperforms classical explicit solvent methods and selected ab initio implicit solvent approaches across multiple solvation free energy
benchmarks, and demonstrates generalization to unseen solvents. Beyond solvation free energies, the model shows close agreement with experimental
nuclear magnetic resonance (NMR) data for $\gamma$-fluorohydrin molecules in chloroform. ConSolv's architecture is readily extensible to broader chemical spaces and alternative training strategies, while its
attention-based design supports explainable artificial intelligence (AI) analysis that can help elucidate complex, solvent-dependent molecular interactions.
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Instrumentation and Methods for Astrophysics
Empirical-Bayes Unfolding of $\gamma$-ray Spectra
A. H. Mjøs, E. Lima, A. Kvellestad et al. (+2 more)
Unfolding observed $\gamma$-ray spectra is an ill-conditioned Poisson inverse problem. Detector response effects and finite energy resolution make distinct non-negative emitted $\gamma$-ray spectra nearly indistinguishable after forward mapping, so direct inversion can strongly amplify statistical fluctuations. Here, we present an empirical-Bayes hierarchical unfolding method that preserves the Poisson counting structure, enforces non-negativity, and incorporates background through a joint ON/OFF likelihood. The prior on the emitted spectrum is centered on an automatically selected Richardson-Lucy reference spectrum, with an adaptive width that remains broad in weakly constrained regions. Posterior inference is performed with the No-U-Turn Sampler, and simultaneous uncertainty bands are reported for the resolution-limited unfolded spectrum. Our
Bayesian method provides a robust and extensible framework for uncertainty quantification in unfolding, and a direct comparison with a recent frequentist regularized maximum-likelihood method gives highly consistent unfolded spectra in representative high- and low-statistics cases.
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All authors A. H. Mjøs, E. Lima, A. Kvellestad, A. C. Larsen, M. Hjorth-Jensen
Soft Condensed Matter
Curvature-induced smectic-C order of tangentially anchored hard spherocylinders on a sphere with a rigidly locked director field
Jonathan Washburn, Hartmut Löwen and Elshad Allahyarov
We study the strict locked-orientation limit of hard spherocylinders on a sphere, in which the rod axes are rigidly locked to a prescribed tangential director field and cannot reorient. Because the bulk hard-rod phase diagram contains no smectic-C phase, any coherent tilt isolates a
geometric curvature mechanism rather than a finite-stiffness
equilibrium effect. A ratio-symmetric recognition cost fixes the layer spacing at the bulk close-contact value and yields a hierarchy of
geometric statements: the lower edge of the smectic-area window at $45^\circ$ follows from reciprocal
symmetry; the upper edge at $58.3^\circ$ is a falsifiable channel-saturation hypothesis; the smectic-A to smectic-C boundary is a closed-form prediction; and the rod tilt angle is set by the rod-to-radius ratio, modulated by a chirality envelope peaking near $24^\circ$. Locked-orientation Monte Carlo across fifteen geometries confirms these predictions with no fitted elastic constants: the smectic area peaks at $55^\circ$, and a coherent smectic-C window is detected.
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Adaptation and Self-Organizing Systems · Cross-listed from cs.LG
How Complexity Contributes to Learning Opacity in Machine Learning
Joachim Stein and Eric Raidl
Machine learning (ML)
algorithms are known to be opaque. We do not know the reasons for their predictions. The learning process leading to the prediction function is also opaque. We do not fully understand the time
evolution of the weight values of neural nets (NN) and related dynamical phenomena. While prediction opacity is widely studied, learning opacity remains largely underexplored. This article studies learning opacity trough the lens of complex dynamical systems. We argue that NN learning is essentially a complex system and that learning opacity is due to dynamical complexity and the epistemological challenges that arise from it. We identify three key properties of training complexity – sensitivity to weight initialization, feedback in gradient based optimization, and sensitivity to the training data – and show how each contributes to learning opacity. As these properties are fundamental to the learning process damping or eliminating them would fundamentally alter how ML systems learn. Some sources of opacity in ML may hence be irreducible.
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Instrumentation and Methods for Astrophysics
Collaborating with Artists in the Search for Life
Jack Madden, Cybele Collins, Mia Rollins et al. (+1 more)
Art and science collaborations that go beyond outreach and advertisement in service of science have the potential to unlock new ways of seeing and understanding the Universe that science alone cannot reach. In this white paper for the NASA Decadal Astrobiology Research and Exploration Strategy (DARES) request for information, we outline examples and benefits of artscience and research-creation methods for astrobiology. The search for life and its origin is inherently interdisciplinary and requires novel approaches that could benefit from the training artists receive in design thinking, contextualization, speculation, and community building. We take a look at this process in action through the work of Robert Irwin during the 1970 NASA Habitability Symposium, Carl Sagan's approach to mixing art and science, and the Transition Design framework of creativity-led problem solving. Each example underscores a specific advantage of deeper art-science collaborations: Irwin's creative approach to problem-solving broke scientists from conventional thought patterns, Sagan's contextualization helped align scientific work with ethical and societal considerations, and design-led research is shown to improve planning and efficiency, even for problems as complex as searching for life. Specific implementation recommendations include specifically allowing funding for artist consultations in research grants, reviving NASA's artist-in-residence program, and supporting artscience training initiatives within the astrobiology community.
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All authors Jack Madden, Cybele Collins, Mia Rollins, Ashika Capirala