Quantum Physics
Detecting Hidden Nonlinear High Frequency Modes Beyond Fundamental Minimal Temporal Resolution Using Weak Measurements
Igor Prlina
In this work we study whether nonlinear models of
quantum mechanics can avoid detection by strong measurements, if the nonlinear effects only exist as high frequency modes. A potential physical process which could hide such modes would be amplitude level time averaging over fundamentally indistinguishable times. To that end, we have defined a temporal indistinguishability postulate which describes the averaging process, and handcrafted a nonlinear toy model well suited to avoid detection. We have demonstrated that even in such an ideal setup, tabletop weak postselected measurements can still detect nonlinear behavior and put constraints on nonlinear high frequency modes of
evolution, even at frequencies beyond fundamental minimal temporal resolution.
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Earth and Planetary Astrophysics
Evidence for a giant companion orbiting Tabby's star
Cristina Madurga-Favieres, P. A. Strøm, Thomas G. Wilson et al. (+2 more)
KIC 8462852, also known as Tabby's
star, shows deep, irregular flux variations up to 20 per cent in its Kepler light curve. These unusual events show no apparent periodicity. Multi-wavelength observations show the dips are consistent with transiting
dust, although its origin remains uncertain. The leading explanation is that
dust may originate from a family of exocomets or planetesimal fragments. TESS data reveal a unique, symmetric transit event consistent with a
planet or brown
dwarf. This would support the theory that incoming exocometary bodies may result from orbital perturbations by a
planet. The analysis of the TESS and, archival and newly obtained radial velocity (RV) data, suggests that a companion could orbit around Tabby's
star with a period of at least ~1030 d. When combined with the constraints imposed by Kepler and other photometric surveys, we find only five orbital period windows are possible. We conduct observations to follow-up the first two windows, significantly reducing the allowed ranges. Fitting the TESS transit using exocometary models produces a poor fit or the need of physically unrealistic parameters, favouring the
giant companion hypothesis. A 2.3 $\sigma$ detection of $M=9.4^{+4.9}_{-4.1}$ M$_{\mathrm{Jup}}$ (3$\sigma$ upper limit < 28.0 M$_{\mathrm{Jup}}$) at the transit orbital period provides tentative evidence of the companion, but more RV observations are required. Along with the radius $R=1.7\pm0.1$ R$_{\mathrm{Jup}}$, the companion would lie in the
giant planet-brown
dwarf regime. In the future
Gaia DR4 astrometry will reveal the nature of this object.
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All authors Cristina Madurga-Favieres, P. A. Strøm, Thomas G. Wilson, Neda Heidari, Flavien Kiefer
Quantum Physics
Unitary $k$-designs without independent Hamiltonian quenches
Pratik Nandy
Unitary $k$-designs provide a resource-efficient framework for emulating Haar randomness up to the $k$-th order. Quench-based protocols have recently been shown to generate such designs, but achieving this typically requires multiple
Hamiltonian realizations, even when using temporal ensembles. Here, we show that no independent
Hamiltonians are required: a single chaotic
Hamiltonian is sufficient to generate approximate
unitary $k$-designs, even when that
Hamiltonian is spatially local. We introduce a two-Pauli-kick (2PK) protocol, in which
unitary evolution under a fixed
Hamiltonian is interspersed with two Pauli operator insertions (kicks). We find that the resulting frame potential approaches the Haar value at long times, with deviations suppressed by the inverse
Hilbert-space dimension. We verify this for single realizations of Gaussian random
matrices, the Majorana and
Spin Sachdev-Ye-Kitaev models, and deterministic local
quantum spin chains. Remarkably, in deterministic
spin systems, the 2PK protocol generates approximate
unitary designs in regimes where quench-based protocols are either inapplicable or fail to converge. Furthermore, our protocol provides a finite-temperature extension of the frame potential and establishes an analytic bound in terms of the
equilibrium partition function. We discuss a
holographic perspective on this mechanism.
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Instrumentation and Methods for Astrophysics
STORM: RDMA-based Monte Carlo Transport Scheme for Distributed-Memory Particle Simulations
Maor Mizrachi, Barak Raveh and Elad Steinberg
Monte Carlo particle transport enables high-fidelity astrophysical radiation and
neutrino simulations - from core-collapse
supernovae and
neutron-
star mergers to
accretion flows - by handling multidimensional geometries, frequency dependence, and moving media without angular discretization. However, inter-rank communication limits scalability on unstructured meshes: standard two-sided MPI requires receivers to post receives and poll completions, creating per-iteration progress overhead that grows with the number of communication partners. Such problems have not demonstrated high scaling efficiency at $O(10^4)$ cores. We present STORM (Scalable Transport via One-sided Remote
Memory), an open-source library for Monte Carlo transport on general meshes, physics, and boundary conditions. STORM provides a lock-free, mesh-independent communication layer that replaces MPI's matched-send/receive semantics with Remote Direct
Memory Access (RDMA) - one-sided operations that write directly into a remote rank's
memory without involving its CPU. Each rank pair shares a single-producer, single-consumer ring buffer; RDMA writes transfer particles while receivers remain passive. A two-sided MPI backend provides a portable fallback. In an
adversarial uniform-emission
benchmark, the RDMA backend sustains $>97\%$ weak-scaling and $>88\%$ strong-scaling efficiency up to 13,440~cores (112~cores per network adapter), with $1.14$-$1.27\times$ speedups over the two-sided alternative. In a Hohlraum IMC
benchmark at 4480 ranks, it is $1.41\times$ faster because MPI progress overhead is reduced by $6.1\times$. By decoupling communication from physics models and mesh representations, STORM removes a barrier to scaling Monte Carlo transport in astrophysical multiphysics codes, enabling coupled radiation-hydrodynamics with energy- and angle-resolved
photon or
neutrino transport on dynamically evolving meshes at scale.
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Cosmology and Nongalactic Astrophysics
The correlation between voids identified in 3D large-scale-structure and 2D weak-lensing maps
Y.Fang, C. T. Davies, N. Hamaus et al. (+1 more)
We investigate the correspondence between voids identified in the 3D
halo distribution and those detected in WL convergence maps. We used 108 realizations of the full-sky
lensing simulations, populated with a source
galaxy redshift distribution consistent with the Dark Energy Survey Year 3 sample. Catalogs of 3D
halo voids and WL voids were constructed using the VIDE and tunnel
algorithms, respectively. The spatial association between the two populations was quantified by measuring the angular excess number density of
halo voids around WL void centers. We detected a statistically significant (S/N >= 25) positive correlation between WL voids and low-
redshift halo voids (0 < z_hv < 0.5) at small angular separations, indicating that WL voids trace genuine underdensities in the large-scale matter distribution. The correlation amplitude closely depends on the WL void selection scheme and decreases when stringent peak-amplitude thresholds are applied, thereby reducing the number of detected WL voids and broadening their effective sizes. The signal also displays a strong
redshift dependence:
halo voids at higher
redshift exhibit weaker correlations because of the declining efficiency of the WL kernel, while WL voids identified from higher-
redshift source bins produce stronger correlations due to the increased contribution from line-of-sight structures. We additionally examined the impact of
halo-void morphology and found that rounder voids with a weaker
alignment along the line of sight display marginally stronger associations with WL voids. Our results provide new insights into the contribution of 3D structure to WL-selected underdensities and offer guidance for future observational analyses seeking to interpret WL voids as tracers of the matter field.
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All authors Y.Fang, C. T. Davies, N. Hamaus, J. J. Mohr
Cosmology and Nongalactic Astrophysics
What could an emerging Big Bang Nucleosynthesis discrepancy be hinting at?
Vivian Poulin, Julien Froustey, Cyril Pitrou et al. (+1 more)
The latest measurement of the
primordial deuterium abundance is in $\sim 2\sigma$ tension with several state-of-the-art predictions of standard Big Bang nucleosynthesis (BBN), when using the
baryon density inferred from the $\Lambda$CDM model fit to
cosmic microwave background (CMB) data. This tension increases to $\sim 3\sigma$ for models attempting to solve the Hubble tension, such as early dark energy (EDE), which generally predict a larger
baryon density than in $\Lambda$CDM. We test whether this discrepancy could be pointing to a non-standard expansion history during BBN. We compute light-element abundances with PRIMAT and compare $\Lambda$CDM, a $\Delta N_{\rm eff}$ extension, and a very early dark energy (vEDE) component. For vEDE, we sample $\Delta H/H$, the fractional increase of the expansion rate while deuterium burning is freezing out and helium-4 fusion is mostly over. The
Bayesian analysis using BBN plus the CMB
baryon-density constraint in the EDE cosmology gives $\Delta H/H = 0.087^{+0.036}_{-0.037}$ during the deuterium burning epoch, i.e. at a temperature $T_{\rm D}\simeq0.03\,{\rm MeV}$, and no residual tension. The vEDE component preserves the observed deuterium abundance at the larger CMB
baryon density while only mildly affecting helium-4. By contrast, extra radiation raises the helium-4 abundance too efficiently and does not reconcile the
baryon density determinations. Together with inflation, dark energy, and EDE, our results hint at the presence of another light scalar field in cosmology.
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All authors Vivian Poulin, Julien Froustey, Cyril Pitrou, Tristan L. Smith
Quantum Physics
HI-QDC: An Isometric Modular Scalable Architecture for Quantum Data Centers
Mohadeseh Azari, Anoosha Fayyaz, Amy Babay et al. (+3 more)
Server-centric
quantum data-center architectures offer scalability by distributing communication tasks across QPUs rather than concentrating complexity in a centralized switching core. However, scaling such architectures increases the path length, the number of Bell-state measurements, and the loss of end-to-end fidelity. We ask whether the path diversity of a server-centric
topology can be converted into a mechanism for preserving not only rate, but also fidelity. We study this through end-to-end purification as a fidelity-restoration mechanism. First, in a black-box model, we determine the minimum number of raw end-to-end Werner-state copies, each carrying the degraded Werner parameter of a distance-ell path, that purification must consume to recover a single copy matching an elementary link, comparing recursive 2-to-1 and optimized nested r-to-1 purification. Second, we instantiate these requirements in a probabilistic BCube architecture, whose edge-disjoint path diversity supplies the raw copies. Because purification imposes a lower bound on input fidelity, no path redundancy can raise the output below this threshold, which limits scaling. To address it we present the Hop-Independent
Quantum Data Center (HI-QDC), an isometric, modular, scalable architecture in which purification transforms end-to-end
entanglement across a module into an effective link-level resource for the inter-module
topology. Our results identify the regimes in which a BCube module, under end-to-end purification, preserves both the fidelity and the yield of an elementary link. The module then hides its internal hop count and acts as an effective elementary link for a higher-level network. Thus
topology supplies the path multiplicity purification requires, while purification converts it into fidelity recovery, enabling recursively scalable
quantum data-center networks.
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All authors Mohadeseh Azari, Anoosha Fayyaz, Amy Babay, David Tipper, Prashant Krishnamurthy, Kaushik Seshadreesan
Mathematical Physics
An FBSDE Construction of the Sine-Gordon EQFT for $\beta^{2} < \frac{6}{7}\, 8\pi$ and Perturbative Renormalization in the Full Subcritical Regime
Sarah-Jean Meyer
We construct the sine-Gordon measure and its renormalized effective potential in finite volume up to the seventh threshold. The construction relies on a weak
stochastic control problem, its associated weak FBSDE, and an analysis of the renormalization flow equation using a multipole Mayer expansion. The analysis is fully inductive, and we include a complete order-by-order analysis in the subcritical regime $\beta^{2}<8\pi$.
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Materials Science
Magnetic ground states of CrPS$_4$ and NiPS$_3$ monolayers from long-range exchange interactions
Balazs Nagyfalusi, Ritesh Das, Alvaro Bermejillo-Seco et al. (+4 more)
We investigate the
magnetic properties of monolayer CrPS$_4$ and NiPS$_3$ by combining first-principles calculations, second-principles
spin models, and Monte Carlo simulations. Unlike conventional approaches that truncate exchange interactions after only a few shells and determine them by fitting total energies, we extract the
magnetic exchange tensors directly from density functional theory using the LKAG formalism and include interactions until numerical convergence is achieved. We show that long-range exchange interactions qualitatively modify the
magnetic behavior of both materials. In CrPS$_4$, they destabilize the previously predicted
ferromagnetic ground state and stabilize a
spin-spiral phase, reducing the critical temperature to about 21\,K, in agreement with available experiments. The resulting
magnetic phase diagram contains multiple collinear and non-collinear phases that can be tuned by temperature and external
magnetic fields. In NiPS$_3$, the experimentally observed zigzag
antiferromagnetic order only emerges when exchange interactions up to the fifth shell are included. These results demonstrate that quantitatively predictive
spin models for thiophosphate monolayers require long-range exchange interactions and provide a predictive framework for accurately describing two-dimensional van der Waals magnets.
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All authors Balazs Nagyfalusi, Ritesh Das, Alvaro Bermejillo-Seco, Herr S. J. van der Zant, Yaroslav M. Blanter, Amador Garcia-Fuente, Jaime Ferrer
Strongly Correlated Electrons
Yuan Xiao, Rimika Jaiswal, Oleg A. Starykh et al. (+1 more)
We study the zero-temperature properties of a
spin-$1/2$ Heisenberg chain with an additional three-site
chiral term of strength $g$. The model is known to be integrable and previous work using Bethe ansatz has identified a phase transition from the usual critical state for $g< g_c = 2/\pi$ to a
chiral phase for $g>g_c$. Here we combine analytical and computational approaches to demonstrate that the transition point comprises an unusual Lifshitz transition with dynamical critical exponent $z=3$, and the
chiral phase is a partially
spin-polarized phase which spontaneously breaks SU(2)
symmetry. We derive a strongly interacting
chiral boson field theory for the critical point, and show that even its small-momentum, low-energy response is non-trivial. We also determine the universal properties of the
chiral phase, and specifically show that it has a simultaneous quadratically dispersing
ferromagnetic "
magnon" mode coexisting with the power-law singularities and linearly dispersing excitations typical of a Luttinger
liquid. Our conclusions are validated using numerics based on
matrix product state methods and exact diagonalization.
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All authors Yuan Xiao, Rimika Jaiswal, Oleg A. Starykh, Leon Balents
Strongly Correlated Electrons
Colloquium: Semi-Dirac Fermions in Quantum Matter
Bruno Uchoa, Mohamed M. Elsayed, Valeri N. Kotov et al. (+2 more)
This article reviews the recent progress on the subject of semi-Dirac
fermions, two dimensional quasiparticles that disperse quadratically, as Galilean invariant particles, or linearly, as massless relativistic particles, depending on their direction of motion. These particles exist at a phase boundary set by the continuous change in the connectivity of
Fermi surfaces, known as topological Lifshitz transitions. The basic properties and the current experimental evidence of the existence of these particles in both synthetic
lattices and
quantum materials are presented. The many-body problem of semi-Dirac
fermions is discussed from a theoretical perspective with an eye to physical observables of relevance to experiments.
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All authors Bruno Uchoa, Mohamed M. Elsayed, Valeri N. Kotov, Yinming Shao, Dmitri N. Basov
Astrophysics of Galaxies
A Naked Dwarf: Molecular Gas in the Completely Stripped HI Tail of VCC 1249
Bumhyun Lee, Aeree Chung, Paolo Serra et al. (+12 more)
We present the first observational hints of the severe removal of both molecular and HI gas from the
dwarf galaxy VCC 1249. This extreme stripping event is thought to be driven by the combined effects of
tidal interaction and ram pressure. Using deep CO (2$-$1) observations from the James Clerk Maxwell
Telescope (JCMT), we obtained marginal CO detections in three regions within the stripped HI tail, with molecular masses of $\sim$10$^{5}$ to 10$^{6}$$M_{\odot}$, comparable to typical masses of
giant molecular clouds. In contrast, we did not find CO emission within the
stellar disk of VCC 1249. This indicates the severe removal of cold gas, which likely caused the sudden cessation of
star formation in the
galaxy. This identifies VCC 1249 as a unique laboratory for witnessing the rapid, environmentally-driven quenching of a
dwarf galaxy. Our findings provide a critical observational link between gas removal mechanisms and the dramatic phase transition of cluster
dwarfs from
star-forming to quiescent systems.
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All authors Bumhyun Lee, Aeree Chung, Paolo Serra, Nikki Zabel, Sungsoon Lim, Hyein Yoon, A. Boselli, Matteo Fossati, Yongjung Kim, Tomonari Michiyama, Juan Molina, Kana Morokuma-Matsui, Jaehyun Lee, Jeong Hwan Lee, Se-Heon Oh
High Energy Physics (Phenomenology)
Reheating the FCC: Probing Early Matter Domination with Long-Lived Particles
Nicolás Bernal, Giovanna Cottin, Kuldeep Deka et al. (+1 more)
We study a GeV-scale
Higgs-portal scalar $\phi$ that can dominate the early Universe and later decay into Standard Model states, ending an early matter-dominated era. Ordinary
cosmic reheating is the minimal example of this scenario. The small
Higgs mixing makes $\phi$ a long-lived particle (LLP), linking the reheating temperature $T_\text{rh}$ to displaced-decay signatures at
colliders. Including finite-temperature suppression of the decay width, we map FCC-hh LLP sensitivity onto the $[m_{\phi}, T_\text{rh}]$ plane. We find that FCC-hh displaced searches could probe GeV-scale transition temperatures, up to the electroweak scale within the broken-phase
Higgs-portal description.
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All authors Nicolás Bernal, Giovanna Cottin, Kuldeep Deka, Manuel López
Mesoscale and Nanoscale Physics
Ideal Bands in Tight-Binding Models
Lexu Zhao, Yang Ge, Shinsei Ryu et al. (+1 more)
A band is called ideal when its Dirichlet functional saturates the topological lower bound. We study ideal bands in finite-band tight-binding models with conventional two-dimensional
lattice translation
symmetries, allowing the bands to have non-flat dispersion. We first provide an analytic construction of isolated Chern-ideal bands with Chern number $|\mathrm{Ch}|=1$ in finite-band models with exponentially decaying hopping. This construction applies only when at least two orbitals have different embedded positions (modulo
lattice vectors), complementing the previously known construction for $|\mathrm{Ch}|>1$. We then show that isolated Chern-ideal bands with any nonzero Chern number cannot exist in finite-band models with finite-range hopping, regardless of the embedded orbital positions. The conclusion holds even if there are isolated band touching points, as long as the Berry
curvature does not diverge anywhere in the Brillouin zone. We finally generalize the conclusions to Wilson-loop-ideal bands with zero total Chern number, such as Kane-Mele $\mathbb{Z}_2$-ideal bands.
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All authors Lexu Zhao, Yang Ge, Shinsei Ryu, Jiabin Yu
Quantum Physics
Learning the closest Slater determinant
Nisarga Paul, Haimeng Zhao and David D. Dai
Learning compact, interpretable descriptions of
quantum many-body states is an important task in
quantum science. We study the task of learning the Slater determinant with maximum fidelity to an arbitrary fermionic many-body state, with motivation from both Hartree-Fock methods and agnostic
tomography. Given an $n$-
fermion wavefunction built from $m$ fermionic modes, we provide classical and
quantum algorithms returning a Slater determinant with fidelity within $\varepsilon$ of maximal in time $m^{\text{poly}(n,1/\varepsilon)}$. We prove matching hardness lower bounds, assuming standard complexity
conjectures, along some parameter axes. Given access to
quantum copies, we prove this can be accomplished with $\text{poly}(m,n,1/\varepsilon)$ copies of $\rho$. We also show that above a fidelity of $2/3$ any stationary point is the unique global maximum while below $2/3$ the optimization landscape can have spurious stationary points, and hence $2/3$ marks a transition point in the optimization landscape for this problem. We apply the
algorithm to the
Fermi-Hubbard model, extracting the closest Slater determinant from neural
quantum state solutions. Together, our results provide algorithmic tools with provable guarantees in understanding fermionic many-body systems with classical or
quantum simulation.
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High Energy Physics (Theory)
Sp(4,Z) actions on 3d U(1)^2 symmetric theories: Order-five duality and bilayer quantum Hall hierarchies
Yasin F. Alam, Andreas Karch, Da-Chuan Lu et al. (+1 more)
The $\mathrm{SL}(2,\mathbb{Z})$ electromagnetic duality of 4d Maxwell theory induces theory-generating operations on 3d theories with $U(1)$ global
symmetry. For theories with $U(1)^n$
symmetry, this structure generalizes to $\mathrm{Sp}(2n,\mathbb{Z})$. Focusing on the $U(1)^2$ case, we formulate the bulk $\mathrm{Sp}(4,\mathbb{Z})$ action and derive the corresponding boundary operations. We identify an intrinsically two-component element of order five, which generalizes the order-three $ST$ element of the single-$U(1)$ theory. Although its fifth power acts trivially in the bulk, the corresponding boundary operation closes only up to a decoupled $U(1)_1$ invertible phase, suggesting a mixed duality-gravitational anomaly. We realize the resulting theory-generating web for Abelian Chern-Simons theories within the $K$-
matrix formalism and apply it to
bilayer fractional
quantum Hall systems. Recasting the Haldane–Halperin hierarchy construction as a sequence of $\mathrm{SL}(2,\mathbb{Z})$ operations, we generalize it to systems with charge $U(1)_c$ and pseudospin $U(1)_s$
symmetries. The resulting
bilayer hierarchies contain branches terminating in an interlayer-correlated bosonic $(221)$ daughter sector, yielding candidate Abelian states at the even-denominator equal-layer fillings $3/8+3/8$ and $5/12+5/12$. Integral changes of anyon basis establish the equivalence of these states to their corresponding Abelian composite-
fermion descriptions. We further discuss the
spin-charge constraints that arise when the electromagnetic background field is treated as a
spin-$c$ connection.
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All authors Yasin F. Alam, Andreas Karch, Da-Chuan Lu, Ryan C. Spieler
High Energy Astrophysical Phenomena
Time-evolving Diagnostic of the Ionized Absorbers in NGC 4051. II. High-throughput Time-resolved Spectroscopy
Alfredo Luminari, Fabrizio Nicastro, Roberto Serafinelli et al. (+5 more)
Active
Galactic Nuclei (AGNs) are one of the most powerful sources in the Universe. The
accretion-liberated energy can strongly impact the surrounding environment, up to the host
galaxy and beyond. Notwithstanding their ubiquitous presence,
nuclear outflows are poorly characterised, mainly due to the degeneracy between their number density $n_e$ and radial location $r$, intrinsic in the photoionisation
equilibrium models which are usually employed to fit the observations. This degeneracy prevents a self-consistent determination of the gas energetics and, therefore, of the efficiency in transporting the AGN energy outwards. We analyse a joint XMM-Newton and NuSTAR observation of the bright, highly-variable AGN NGC 4051. The high flux allows to perform time-resolved spectroscopy and, thus, to study the
evolution of its three main ionised absorbers. Since the timescale of the gas ionisation variability depends on its number density, constraining it allows to break the density-distance degeneracy. We employ the Time-Evolving PhotoIonisation Device (TEPID) to model the temporal
evolution of the
outflows. We split the observation in 37 time-resolved spectra, each few kiloseconds long (total duration 160 ksec), and we fit them jointly with the time-resolved ionised spectra. We fully constrain $n_e=10^7 cm^{-3}$ and $r=10^4$ gravitational radii for the absorber with the highest opacity and intermediate ionisation. This distance is the same of the optical and UV Broad Line Region and of the soft X-ray emission lines. The fastest and most ionised absorber is at $r<600 r_G$, cospatial with the broad component of the Fe K$\alpha$ line. The slowest and least ionised absorber is at $r \geq 3.8 \cdot 10^5 r_G$, the same distance of the cold
torus and the narrow Fe K$\alpha$. The total energy
outflow rate is below $10^{-4} L_{bol}$, ruling out a meaningful mechanical impact on the host
galaxy.
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All authors Alfredo Luminari, Fabrizio Nicastro, Roberto Serafinelli, Riccardo Middei, Yair Krongold, Elias Kammoun, Luigi Piro, Francesca Diaferia
High Energy Physics (Phenomenology)
Dark Matter Weather: Probing Sub-GeV Interactions with Earth-Shielding Modulation
Tetiana Kozynets, Rebecca Leane and Juri Smirnov
Daily modulation from Earth shielding provides a powerful search handle for sub-GeV dark matter (DM) in low-threshold experiments. We use this effect as a probe of interaction structure in scenarios where DM couples to both electrons and
nuclei.
Nuclear scattering in the Earth alters the incident DM flux, while electron scattering produces the observable ionization signal, so the total rate and modulation pattern encode different aspects of the underlying interactions. We develop this two-interaction framework for argon and xenon targets and introduce a new statistical analysis that tests the modulation shape, including the location-dependent exposure of underground detectors to different Earth-crossing trajectories, alone and in combination with the ionization spectrum. We demonstrate the method for
liquid-noble detectors at underground sites SURF (USA), LNGS (Italy), and SUPL (Australia), and apply it to DarkSide-50 data as a concrete case study. Our results show that Earth-scattering modulation can help disentangle electron and
nuclear DM interactions and provide a validation handle for low-threshold
liquid-noble searches.
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Strongly Correlated Electrons
Monte Carlo Studies of Twisted Bilayer Graphene: Strain and Thermal Fluctuations
Johannes S. Hofmann, Patrick Ledwith, Ashvin Vishwanath et al. (+2 more)
We study the phase diagram of twisted
bilayer graphene at charge neutrality as a function of twist angle $\theta$, uniaxial heterostrain $\varepsilon$, and temperature $T$ using sign-problem-free
quantum Monte Carlo simulations. At $T=0$ and zero strain, we find a continuous transition from a Dirac semimetal to a gapped Kramers inter-valley coherent (KIVC) phase as $\theta$ decreases toward the magic angle. With finite strain, the KIVC phase undergoes a further continuous transition at smaller $\theta$ into an anisotropic semimetal with gapless excitations near the center of the moiré Brillouin zone. In the KIVC regime, the
entropy rises sharply with temperature and plateaus at $15\,\text{K} \lesssim T \lesssim 40\,\text{K}$ near the value expected from a Mott-like regime of localized electrons with nearly uncorrelated
spin, valley, and orbital degrees of freedom, despite the topological obstruction preventing a localized tight-binding description of the active bands. The spectral function evolves continuously with $\theta$: at low $T$, a gap opens at the $K$ points and the minimal gap shifts to $\Gamma$ as $\theta$ decreases; at intermediate $T$, the spectral function smoothly interpolates between a Dirac semimetal spectrum with coherent $K$-point quasiparticles and a spectrum with gapless $\Gamma$-centered quasiparticles near the magic angle. The later can be a anisotropic or a Mott semimetal and we discuss how to distiguish them in experiment.
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All authors Johannes S. Hofmann, Patrick Ledwith, Ashvin Vishwanath, Jong Yeon Lee, Erez Berg
High Energy Astrophysical Phenomena
Polarization of impulsive relativistic jets propagating in a stratified medium
Gal Birenbaum, Paz Beniamini and Jonathan Granot
Gamma-ray bursts (GRBs) and at least some
tidal disruption events (TDEs) are highly energetic transients involving impulsive relativistic jets. As these jets propagate into their surrounding media, they drive a relativistic forward shock into it, which radiates multi-wavelength polarized synchrotron emission, known as an afterglow. Analyzing the afterglow light curve along with its polarization curve can shed light on the geometrical properties of the GRB or TDE system such as the
magnetic field structure behind the shock, the jet angular structure and even distinguish between proposed scenarios of delayed
radio emission seen in some TDEs. While most afterglow polarization measurements are for long GRBs, whose massive
star progenitor winds are expected to form a stratified external medium, the polarization from such environments is largely unexplored. Similarly, stratified media surround jetted TDEs. In this work we explore how shock propagation into a stratified medium affects the observed afterglow polarization from impulsive relativistic jets. We find that for both top hat and structured jets, in most cases the polarization levels are reduced and its temporal signature evolves on longer time scales compared to a uniform external medium. The polarization peaks at times close to a geometrical break in the light curve, indicating measurements during this time probe the maximal levels of polarization possible for the system. In addition, observationally capturing the polarization
evolution time scales can assist in constraining our viewing angle and the external medium stratification. Such composite models, that account for more realistic systems that are motivated by light curve fittings, will allow us to complement afterglow light curves better and promote joint modeling of these observables.
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Solar and Stellar Astrophysics
A dust-free hierarchically nested supermassive-star model for James Webb Space Telescope Little Red Dots
Pau Amaro Seoane
Observations by the James Webb Space
Telescope reveal a population of high-
redshift objects, the little red dots. These sources exhibit optical reddening alongside blue ultraviolet continua, host broad Balmer lines indicative of active black holes, and lack detectable x-ray emission. Their
cosmic abundance at early epochs exceeds standard Eddington-limited growth timescales. Prevailing models invoke specific
dust geometries to reconcile these traits. We propose a
dust-free physical framework. We evaluate the concept that the
dust-poor subset of little red dots represents the observational manifestation of hierarchically nested supermassive
stars. A primary radiation-dominated envelope traps a
nuclear star cluster. Plunging
stars drive a
magnetic dynamo that inflates the envelope. This produces the red optical continuum. Unobscured infalling
stars yield the blue ultraviolet excess. Trapped
stellar debris sediments to form a high-density secondary core within this Compton-thick host. This nested
topology thermalizes x-rays and powers the broad hydrogen $\alpha$ features. The central seed accretes at the global radiation limit of the host envelope. This kinetic bypass shortens the assembly timescale from hundreds of millions of years to tens of millions of years.
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Quantum Physics
Enabling Neutral Atom Integration: Redesigning Device Models for Universal Quantum Ecosystems
Yannick Stade, Lukas Burgholzer, Ludwig Schmid et al. (+1 more)
Quantum computing is transitioning from an academic idea to a practical technology, driven by recent hardware advancements and clear paths toward real-world applications. Universal
quantum ecosystems (e.g., Qiskit, Cirq, PennyLane) facilitate this transition by providing a consistent interface to diverse
quantum devices, abstracting hardware-specific details through a device model that captures each device's computational capabilities. However, these device models have historically been shaped by superconducting hardware, assuming static
qubit positions and fixed coupling maps. This prevents them from representing the unique computational capabilities of emerging technologies such as neutral atoms, which feature dynamic
qubit rearrangement and zoned operations. As a result, although numerous specialized compilers for neutral atom devices already exist, they cannot retrieve the hardware information they need through these ecosystems - creating a technology lock that hinders or even prevents the integration of neutral atom devices. In this work, we demonstrate how this limitation leads to suboptimal compilation results and can exclude certain devices entirely. Motivated by this, we propose rethinking current device models to faithfully represent neutral atom devices, enabling their seamless integration into universal
quantum ecosystems. Evaluations conducted within the
Quantum Device Management Interface (QDMI) demonstrate that the proposed device model unlocks a routing overhead fidelity improvement by a factor of up to 100,000 on a
circuit with 16
qubits and 600 gates.
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All authors Yannick Stade, Lukas Burgholzer, Ludwig Schmid, Robert Wille
High Energy Astrophysical Phenomena
The Origin of the Magnetic Flux Driving TDE Jets
Nimrod Tripto, Julian Krolik and Tsvi Piran
Tidal Disruption Events (TDEs) occur when a
star approaches a black hole closely enough to be torn apart by
tidal forces, after which the
stellar debris begins to orbit the black hole. Over the past decade, hundreds of TDEs have been identified, with many more expected from upcoming surveys. A small subset of these events launch transient, highly luminous relativistic jets (10^47-10^48 erg/s isotropic-equivalent). These are generally interpreted in terms of the Blandford–Znajek mechanism, implying the presence of substantial
magnetic flux near the black hole horizon. The question arises: What is the origin of this flux? In this paper, we investigate three candidate sources:
stellar magnetic fields,
magnetic flux from large radii around the black hole (the Lasso mechanism), and
magnetic flux stored in the inner portion of a pre-existing
accretion disk. We find that: observed
stellar magnetic fields are insufficient to power these jets; the Lasso mechanism requires shallow radial
magnetic field profiles and a mechanism to trap the
magnetic flux brought by the debris in the vicinity of the black hole; pre-existing
magnetic flux near the black hole in an
accretion disk is the most plausible source.
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Cosmology and Nongalactic Astrophysics
Gravitational Lensing Predictions from Wave Simulations of Fuzzy Dark Matter
Jiajun Zhou, Zhengxiang Li, Amruth Alfred et al. (+3 more)
In the cold dark matter paradigm, ultra-light particles are emerging as strong contenders to conventional massive particles. A unique prediction of dark matter comprising such ultra-light particles, known as fuzzy dark matter (FDM), is the presence of strong density modulations throughout
galactic halos due to wave interference, which – when approximated by a Gaussian random field (GRF) – have been proposed to account for the inability to reproduce the observed positions (when measured at sufficient precisions) and flux ratios of multiply-lensed images of
quasars. Here, we predict for the first time the properties of gravitationally lensed images generated from 3-D density fields obtained by wave simulations that directly evolve the Schrödinger–Poisson equations. Using a novel framework to project these evolved density fields along various axes of the 3-D
halo, we obtain the distribution of perturbations to the positions of lensed images. As an exacting test, we find that particles of mass $10^{-22}$ eV can reproduce the positions of the quadruply-lensed
radio jets in system HS 0810+2554 to a level better than that of either the GRF approximation or, to a greater extent, an NFW best-fit solution, both of which rely on accurately capturing the global 3-D density field of dark matter
halos. Our work highlights the importance of wave simulations for making accurate FDM
lensing predictions and the potential for high-resolution observations of lensed systems to serve as a direct probe of the nature of dark matter.
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All authors Jiajun Zhou, Zhengxiang Li, Amruth Alfred, Ran Gao, Jeremy Lim, Zong-Hong Zhu
High Energy Physics (Theory)
New Type IIB Poly-instanton Effects and Axion Quintessence
Luca Caraffi, Federico Carta and Michele Cicoli
Previous studies of poly-instantons in type IIB Calabi-Yau orientifolds found that these effects arise when Euclidean D3-branes wrap rigid cycles with a Wilson line. In this work, we extend this result through a general analysis of instanton zero modes, revealing the existence of new poly-instanton effects for rigid cycles with a deformation, provided that O3-planes are localised on the worldvolume of the Euclidean D3-brane. We provide concrete Calabi-Yau examples with explicit orientifold involution and brane setup. One of them is particularly well suited for realising
axion hilltop quintessence. In particular, the double exponential suppression of poly-instanton effects allows to reproduce the observed
vacuum energy for natural values of the underlying parameters.
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Astrophysics of Galaxies
Two stellar clocks, one history: a Gaia colour-magnitude-diagram reconstruction of the solar-neighbourhood star-formation history tested against white dwarfs
Michele Cignoni, Pier Giorgio Prada Moroni, Martina Gabbanini et al. (+2 more)
The
solar-neighbourhood
star-formation history (SFH) can be constrained from the colour-magnitude diagram (CMD) of non-degenerate
stars and tested independently with the white-
dwarf luminosity function (WDLF). These two tracers sample complementary evolutionary phases and provide a consistency check on both the recovered SFH and the adopted WD cooling models. We reconstruct the local SFH from the
Gaia DR3 CMD and test whether the resulting history reproduces the observed 40 pc WDLF. We fit non-degenerate
stars in a cylinder of radius 200 pc and vertical extent $\pm40$ pc using the SFERA synthetic-population code. The fit is performed with the PISA and PARSEC
stellar libraries. Each CMD-derived solution is then used to generate a synthetic WD population for comparison with the 40 pc WDLF, adopting the same initial-final mass relation and four WD cooling model sets: BaSTI, MIST, La Plata, and Montreal. The two CMD-based solutions agree on the main features of the local SFH: low activity at the oldest ages, an early episode around 9-11 Gyr ago, reduced activity between about 4 and 9 Gyr, and enhanced
star formation over the last few Gyr. The predicted WDLFs reproduce the bright and intermediate part of the observed distribution for all cooling grids, but differ substantially around the WDLF maximum and along the faint tail. MIST and BaSTI shift too much weight to magnitudes fainter than the observed maximum, whereas La Plata gives the closest match to the faint tail but leaves larger residuals around the maximum. Montreal provides the best overall compromise. On this cooling scale, progressively removing the oldest synthetic WDs shows that the faint tail disfavours a substantial contribution from WDs with total ages older than about 11 Gyr.
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All authors Michele Cignoni, Pier Giorgio Prada Moroni, Martina Gabbanini, Scilla Degl'Innocenti, Antonio Tinarelli
Solar and Stellar Astrophysics
A Framework for Linking Pre- and Post-Common Envelope Binary Properties with Star Clusters: The First Demonstration with a Massive White Dwarf+M Dwarf Binary in Alessi 12
Steffani M. Grondin, Maria R. Drout, Jason Nordhaus et al. (+12 more)
Common envelope (CE)
evolution is a critical phase in the lives of binary
stars, producing close binaries that are progenitors of type Ia
supernovae and gravitational wave sources. Despite its importance, CE
evolution remains poorly understood, largely due to the scarcity of systems with constrained pre- and post-CE properties. Here, we present a
star cluster-based framework for reconstructing the evolutionary histories of white
dwarf+main-sequence (WD+MS) post-CE binaries, where cluster membership can provide an independent age constraint and/or rule out a merger origin for the WD. We demonstrate this method with Alessi12-PCE, the first such binary in an open cluster with precisely determined pre- and post-CE properties. We classify the companion as an M4V and measure a WD mass of $1.06 \pm 0.02 M_{\odot}$, making it the most massive WD+MS binary associated with a cluster. A 6.99-hour periodicity detected in a light curve is confirmed as the binary orbital period via radial velocity monitoring. Combined with the WD mass, WD cooling age, and Alessi 12 cluster age,
stellar evolution models imply a $5.40 \pm 0.10 M_{\odot}$ WD progenitor that entered a CE on the asymptotic
giant branch (AGB). CE
evolution models where convection is the dominant physical mechanism that sets $\alpha_{\text{CE}}$ reproduce the observed orbital separation in exactly two scenarios: either a mid-AGB interaction with $\alpha_{\text{CE}}\approx0.99$, or a late-AGB interaction with $\alpha_{\text{CE}}\approx0.05$. Applicable to other post-CE binaries in
star clusters, our new framework enables empirical constraints on CE physics inaccessible from field binaries alone.
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All authors Steffani M. Grondin, Maria R. Drout, Jason Nordhaus, Philip S. Muirhead, Bailey Filer, Alexander Laroche, Jeremy J. Webb, Floor S. Broekgaarden, Ryan Chornock, Kyle Kremer, Natalie LeBaron, Raffaella Margutti, Nikki Noughani, Huei Sears, Pier-Emmanuel Tremblay
Instrumentation and Methods for Astrophysics
Structural, thermal and optical tolerance analysis of SHARP, a near infrared spectrograph for next generation telescope
H. Mahmoodzadeh, P. Saracco, I. DI Antonio et al. (+15 more)
The design and verification of cryogenic near-infrared spectrographs require rigorous multidisciplinary analyses to ensure optical performance under realistic operational conditions. In this work, we present a structural-thermal-optical performance (STOP) analysis of the SHARP instrument, a multi-mode spectrograph designed for use with upcoming multi-conjugate adaptive optics (MCAO) systems on Extremely Large
Telescopes (ELTs). Transient and steady-state thermal simulations were performed using Ansys to model the cooldown process and temperature distribution within the opto-mechanical structure. The resulting temperature fields were mapped to structural models through linear interpolation, enabling the evaluation of thermal stresses and deformations of optical elements. Optical sensitivity and tolerance analyses were carried out using Ansys Zemax OpticStudio, with Monte Carlo simulations applied to assess robustness against decenter, tilt, and despace errors. Results indicate that SHARP maintains RMS spot radius values within acceptance threshold, and that the inclusion of compensators significantly enhances compliance with the Ensquared Energy (EE) requirement across all channels. The analysis confirms that SHARP can achieves its optical performance goals while remaining within mechanical and thermal constraints, providing a validated framework for the development of next-generation cryogenic astronomical instrumentation.
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All authors H. Mahmoodzadeh, P. Saracco, I. DI Antonio, P. Conconi, D. Scaccabarozzi, B. Saggin, E. Molinari, C. Arcidiacono, I. Arosio, E. Cascone, V. Cianniello, V. De Caprio, G. Di Rico, B. Di Francesco, C. Eredia, P. Franzetti, M. Fumana, E. Portaluri
General Relativity and Quantum Cosmology
Black hole-neutron star binaries with high spins and large mass asymmetries: III. Properties of the ejected material and its electromagnetic signatures
Konrad Topolski, Samuel D. Tootle, Paramvir Singh et al. (+2 more)
Compact binary systems consisting of a black hole (BH) and a
neutron star (NS) are expected to provide detectable signals both in the gravitational wave and in the electromagnetic channels, thus representing excellent sources for multi-messenger astronomy. In this third paper in a series, we report on the
geometric and thermodynamic properties of the purely dynamical ejecta component modeled in our general-relativistic magnetohydrodynamical simulations of BHNS systems over a comprehensive binary parameter space consisting of large mass ratio and high BH
spin. The
tidal disruption and dynamical mass ejection is studied by monitoring the transfer of energy and angular momentum to matter for the particular case of a highly unequal-mass binary with large BH
spin, extending known results for low-mass-ratio, irrotational BHNS binaries. By varying the binary parameters, we investigate their influence on the
geometric, thermodynamic, and kinematic properties of the ejected matter. Furthermore, we employ the
nuclear-reaction network SkyNet to obtain the elemental abundances resulting from the r-process active in the ejecta and study how they depend on the properties of the progenitor objects. Finally, using the radiative-transfer code POSSIS, we compute the kilonova light-curves from the results of our simulations, discuss their bolometric and optical/near-infrared
evolution, and compare them with the AT2017gfo data and upper-limits for S190814bv, finding overall consistency.
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All authors Konrad Topolski, Samuel D. Tootle, Paramvir Singh, Mattia Bulla, Luciano Rezzolla
High Energy Physics (Phenomenology)
Earth rotation turns event timing into a geometric probe of UHE neutrino origin
Andrew Cheek, João Paulo Pinheiro and Jordi Salvado
It has been proposed that the ultra-high-energy (UHE) event $\rm KM3-230213A$ detected by KM3NeT could be explained by dark matter (DM) decay. Prima facie this seems unlikely because the arrival direction of the event is opposite to the
Galactic Centre. We develop a per-event test statistic to quantitively assess this possibility and forecast the required future events to exclude the DM hypothesis in favour of an isotropic signal. For the single event observed, the DM decay hypothesis is disfavoured but not excluded ($p\text{-value}_{\rm DM}\simeq0.13$–$0.15$). We emphasise how including the time-averaged detector visibility helps discrimination despite reducing the proportion of visible sky, reducing the number of events for exclusion from $\sim33$–$43$ to $\sim22$–$27$. Moving beyond this, we perform a fully time-resolved forecast and find that the required number of events for exclusion reduces by $40\%$, $\sim14$–$16$. The time variation in the signal provides vital information allowing one to exclude or confirm the DM hypothesis with much fewer events. Our results are robust against DM decay channels and
halo distributions and can readily be applied to other relics distributed similarly. Our framework allows one to turn event timing into a probe of signal geometry and is generic to any UHE equatorial
neutrino telescopes.
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