High Energy Astrophysical Phenomena
A Newly Identified Transient Ultraluminous X-ray Source in M31
Ferdinand, Murray Brightman, Jean-Marie Hameury et al. (+9 more)
Ultraluminous X-ray sources (ULXs) are off-
nuclear X-ray sources with luminosities exceeding the Eddington limit of typical
stellar-mass compact objects. While most known ULXs are relatively persistent sources, transient ULXs have emerged as a distinct population that offer unique insight into extreme, super-Eddington
accretion. We report the discovery and X-ray characterization of a newly identified transient ULX in M31. First detected serendipitously on 2021 June 9, the source reached a peak unabsorbed $0.3 - 10$ keV luminosity of $\sim10^{39}\ \rm erg\ s^{-1}$. Its spectral
evolution suggests increasing advection at later epochs, opposite to the expected transition from a super-Eddington slim disk toward a standard thin disk during the decay of the outburst. The observed X-ray light curve can be reproduced using the disk-instability model of Hameury & Lasota, with characteristic timescales of $\sim41-61$ days. The inferred mass-
accretion rate is super-Eddington for a $1.4\,M_{\odot}$
neutron star but approximately Eddington for a $10\,M_{\odot}$
stellar-mass black hole. Nearby optical sources from the Hubble Source Catalog suggest a possible
giant donor with an age of $\log_{10}({\rm age/yr})\sim8.5$ and a mass of $\sim3.2\,M_{\odot}$, when compared with
stellar isochrones with an assumed $A_V=1.58$. We estimate a transient ULX occurrence rate in M31 of $0.18\pm0.10\ {\rm yr^{-1}}$. This rate is lower than those reported for other
galaxies in previous studies. M31 ULX-3 expands the small population of known transient ULXs in M31 and highlights the importance of continued, regular X-ray monitoring of nearby
galaxies.
Read the full abstract ▾
All authors Ferdinand, Murray Brightman, Jean-Marie Hameury, Elias Kammoun, Dominic J. Walton, Matthew J. Middleton, Hannah Earnshaw, Felix Fürst, Wynn V. Jacobson-Galán, Jacob E. Jencson, Margaret Lazzarini, Mark T. Reynolds
Solar and Stellar Astrophysics
Debye cooling of ultramassive white dwarfs
David Barba-González and Sivan Ginzburg
Recent observations of cold and massive white
dwarfs are beginning to probe Debye cooling: an accelerated cooling phase driven by the vanishing heat capacity $C_V(T)$ of the crystallized interiors at low temperatures $T$, due to the
quantum nature of
phonon oscillations. We analyse this regime by calculating, both analytically and numerically, the instantaneous cooling time $\tau(L)\equiv -\textrm{d}t/\textrm{d}\ln L$, which is a proxy for the number density of white
dwarfs at a given luminosity $L$. We find that cooling accelerates ($\tau$ shortens) at $L\lesssim 10^{-4}\,\textrm{L}_{\odot}$ due to a combination of Debye cooling and the simultaneous convective coupling of the degenerate core to the surface, with neither process causing significant acceleration on its own. Specifically, strong
magnetic fields can inhibit convective coupling, leading to an almost flat $\tau\propto L^{1/7}$ instead. We parametrize the uncertainty in the solid microphysics by generalizing the Helmholtz free energy such that $C_V\propto T^\delta$ at low temperatures. The currently observed decreasing luminosity function in the Debye regime is tentatively consistent with $\tau(L)$ of non-
magnetic white
dwarfs with $\delta=3$, corresponding to the standard Debye model. Larger samples could probe, in addition to magnetism, deviations $\delta<3$, which diverge appreciably before the
Galactic disc's age $t\approx 10\textrm{ Gyr}$ for masses $M\gtrsim 1.0\,\textrm{M}_{\odot}$. For $\delta>3$, in contrast, the cooling curves converge because the heat capacity becomes dominated by the degenerate electrons $C_V\propto T$.
Read the full abstract ▾
High Energy Physics (Theory)
Cosmological Correlators from Generating Potentials and Projective Geometry
Aswini Bala, Sachin Jain and Deep Mazumdar
We introduce novel scalar generating potentials to compute three and four point cosmological correlators in orthogonal Grassmannian space. These correlators are obtained by applying appropriate directional derivatives on these potentials, combined with helicity-dependent minors. We emphasize that, this is not a
spin-raising analog, but a much more powerful construction. The four point generating potential is associated with the geometry of a projective triangle. First-order directional derivatives generate
gluon correlator, while the Hessian of the same scalar potential produces the four-graviton correlators, thus realizing a differential double copy. Thus, double copy is a natural consequence of the underlying scalar potential as the origin of the
gluon and graviton four point correlators. This framework extends naturally to any
spin-$s$. We exhibit a
geometric origin for the
gluon colour identities: the projective homogeneity of the scalar potential implies Kleiss-Kuijf identity, while the kinematic Jacobi identity follows as a consequence of the closure of the triangle under directional derivatives. We also uncover a connection between the BCFW bridge deformation of the scalar potential and directional derivatives that produces the
spin-s correlator. Thus the generating potential provides a universal geometrical interpretation for any
spin-$s$ four point Grassmannian correlator, unlike \cite{Bala:2026lvw} where
geometric interpretation was only shown for the
gluons.
Read the full abstract ▾
High Energy Physics (Theory)
Worldsheets reconstructed: Duals to two-cut matrix models
Sounak Pal
We compute the higher-rank translation ($\mathcal{T}$) and rotation ($\mathcal{R}$)
matrices associated with a genus-one spectral curve. Using these data, we reconstruct the worldsheet correlators of vertex operators in the corresponding supersymmetric Landau–Ginzburg (LG) theory. This provides a generalization of the genus-zero, one-cut spectral-curve construction to higher-genus geometries. The
matrix-model correlators are mapped to integrals over the
moduli space of Riemann surfaces for the symmetric sextic double-well potential, which has a double-cut solution. We further identify the rational and
elliptic contributions to the worldsheet integrated vertex operators and show that each of the sector precisely matches the corresponding correlators of single-trace operators in the
matrix model. Altogether, our construction showcases an explicit dictionary between the higher-genus spectral-curve data, the associated Cohomological field theory (CohFT), and the worldsheet description of the corresponding
matrix-model observables.
Read the full abstract ▾
High Energy Physics (Phenomenology)
Sensitivity targets for dark photon searches in charged kaon decays
M. Fabbrichesi, E. Gabrielli and K. Müürsepp
We investigate the prospects for detecting invisible dark
photons in charged kaon decays through the two-pion channel $K^+\to\pi^+\pi^0\,\gamma_D$ and the one-pion radiative decay $K^+\to\pi^+\gamma\,\gamma_D$, where $\gamma$ and $\gamma_D$ denote the ordinary
photon and dark
photon, respectively. The former decay was previously proposed as a golden channel for massless dark
photon searches at NA62, while here we introduce the radiative process as a complementary probe and extend both analyses to massive dark
photons. The three-body modes are particularly relevant at low dark
photon masses, where the two-body decay $K^+\to\pi^+\, \gamma_D$ becomes strongly suppressed and vanishes in the massless limit. For massless dark
photons, renormalizable interactions induced by kinetic mixing are absent, and the dominant contribution arises from the effective non-renormalizable
flavor-changing
quark interaction $s\to d\, \gamma_D$ mediated by a dimension-five
magnetic-dipole operator. This is also true for massive dark
photons. Their kinetic mixing contributes negligibly to these channels, after considering the existing bounds on the mixing parameter. Only the same
flavor changing
magnetic-dipole operator as in the massless case is relevant. Using the
chiral quark model, we estimate the relevant hadronic
matrix elements of the dipole operator and account for constraints from $K^+\to\pi^+\,X$, where $X$ denotes resonant missing energy, $K^+\to\pi^+\nu\bar\nu$, and $K^0\!\!-\!\bar{K}^0$ mixing. Based on these calculations, we determine the allowed branching ratios for these decay modes and the sensitivities required at NA62 and future charged-kaon facilities.
Read the full abstract ▾
High Energy Physics (Phenomenology)
An early $Z'$ dominance: dark matter, gravitational waves & collider probes
Basabendu Barman, Nayan Das, Partha Kumar Paul et al. (+1 more)
In the minimal anomaly-free gauged B$-$L extension of the Standard Model (SM), we consider a scenario in which the energy density of the new Abelian gauge
boson dominates the Universe prior to big bang nucleosynthesis (BBN), resulting in an early matter-dominated (EMD) era. Taking one of the three right-handed
neutrinos to be a decaying dark matter (DM) candidate, we investigate its production during this EMD phase. We show that the region of parameter space consistent with the relic abundance lies within the projected sensitivity of several gravitational wave (GW) experiments, where the GW signal arises from
cosmic strings formed during the spontaneous breaking of the gauged B$-$L
symmetry. We further constrain the viable parameter space using bounds from
collider experiments, beam dump experiments, BBN, and ultra high energy
neutrino observations, demonstrating the complementarity of multi-messenger probes in exploring physics beyond the SM as well as non-standard cosmological histories prior to BBN.
Read the full abstract ▾
All authors Basabendu Barman, Nayan Das, Partha Kumar Paul, Narendra Sahu
General Relativity and Quantum Cosmology
The price of regularity: core gradient instability in nonsingular dyonic black holes
Lodovico Capuano and Alessandro Longo
Spacetime singularities displayed by classical black hole solutions are expected to be cured by high-energy effects, beyond the regime of validity of General Relativity. On the other hand, there are well-known examples of classical theories allowing for nonsingular black hole solutions. The most prominent is obtained by complementing the gravitational sector of General Relativity with a minimally coupled nonlinear-electrodynamics sector. It has recently been shown that purely electric/purely
magnetic nonsingular black holes in an Einstein-nonlinear-electrodynamics setup are always plagued by a gradient instability. In this work, we derive the quadratic action for linear perturbations of static, spherically symmetric dyonic solutions of Einstein-nonlinear-electrodynamics theories with a general dependence on both invariants. We show that regularity of the center, absence of ghosts and angular gradient stability cannot hold simultaneously: arbitrarily close to a regular center, at least one
photon polarization has a negative squared angular propagation speed. We further show that regularity drives one electromagnetic kinetic
eigenvalue to zero at the center, which may limit perturbative control near the core. Evading the obstruction requires extending the theory, for example by introducing additional degrees of freedom.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Full-Shape Analysis of the Redshift-Space Galaxy Trispectrum in the EFTofLSS
Beatriz Tucci and Oliver H. E. Philcox
The effective field theory of large-scale structure (EFTofLSS) program for spectroscopic
galaxy surveys has been remarkably successful for cosmological inference from the
galaxy power spectrum and bispectrum. However, a full-shape cosmological analysis including the
galaxy trispectrum has not yet been performed. In this work, we develop the tree-level EFTofLSS model of the
galaxy trispectrum, including all relevant ingredients:
galaxy bias, stochasticity, infrared resummation, Fingers-of-God (FoG) counterterms, Alcock-Paczynski distortions, binning effects, and covariance. We validate the model by performing cosmological inference using the one-loop
galaxy power spectrum, tree-level bispectrum, and tree-level trispectrum measured from dark-matter
halos in 25 AbacusSummit $N$-body simulations, whose large effective volume ($V=200h^{-3}\text{Gpc}^3$) allows us to test the precision of our model and determine scale cuts in both real-space and
redshift-space. We also study the cosmological information content of the
galaxy trispectrum in a DESI-like volume, finding that its inclusion can improve constraints e.g., on $\omega_{\rm cdm}$ by up to $15\%$. We further find that the maximum scale cut can be extended to $k_{\max}=0.12h\mathrm{Mpc}^{-1}$ depending on the tracer, thanks to our improved treatment of FoG effects. This provides a path towards using the three-dimensional large-scale structure to constrain new-physics scenarios with distinctive signatures in the trispectrum, in particular
primordial non-Gaussianity.
Read the full abstract ▾
Strongly Correlated Electrons
Junyi Cao and Eduardo Fradkin
We study zero modes bound to charge-conjugation defects in fractional
quantum Hall-
superconductor (FQH-SC)
heterostructures built from Abelian and non-Abelian FQH states. Although the associated defects are well described by $G$-crossed braided tensor categories, a local operator description of their zero modes is not generally known. We generalize the bulk-to-boundary construction of localized zero mode operators to FQH-SCs with non-Abelian parent topological orders, mapping bulk Wilson operators in the folded theory to localized zero mode operators in the one-dimensional FQH-SC theory. This construction distinguishes zero mode anyons from the local zero mode operators that act on the defect
Hilbert space and yields a generalized zero mode
algebra. It also determines the fusion-channel dependence of tunneling: tunneling of zero mode operators probes bulk monodromy, while direct zero mode anyon transfer probes $G$-crossed associativity data. Applying this framework, we recover the $\mathbb{Z}_{2m}$ parafermion zero mode structure of fermionic Laughlin FQH-SCs at filling $\nu=1/m$, obtain a $\mathbb{Z}_2^{(n)}\times\mathbb{Z}_N$ structure for generalized Moore-Read states at filling $\nu=1/m$, with $N=2m$ for fermionic states and $N=m$ for bosonic states, and find a $\mathrm{Fib}\times\mathbb{Z}_N$ structure for the $k=3$ Read-Rezayi state at filling $\nu=3/(3M+2)$, with $N=2(3M+2)$ for fermionic states and $N=(3M+2)/2$ for bosonic states. In the Read-Rezayi case, zero mode operator tunneling and direct zero mode anyon transfer yield distinct universal amplitude ratios between the neutral fusion channels, providing a characteristic signature of the underlying Fibonacci defect structure.
Read the full abstract ▾
Astrophysics of Galaxies
Modeling the nanohertz gravitational wave background with the t-process: Improved frequentist analysis of gravitational-wave power
B. E. Moreschi, K. A. Gersbach, G. Shaifullah et al. (+2 more)
Pulsar timing array (PTA) collaborations have recently reported evidence for a gravitational wave background (GWB) signal in the nanohertz band, which most likely originates from the incoherent superposition of GWs emitted by a population of supermassive black hole binaries (SMBHBs). Since the number of binaries emitting in each frequency bin is finite, and since individual loud sources can dominate the GWB, the power spectral density (PSD) of the background is expected to deviate significantly from the smooth power law that describes an idealized population. PTA searches usually describe the PSD either with a power law or with a free spectrum model, which fits the PSD in each frequency bin as a free parameter. In this paper, we explore the t-process as a third model; it assumes a power law as the underlying spectrum but leaves each frequency bin free to deviate from it. We compare the performance of these three models on simulated
datasets, injecting $100$ realizations of a realistic SMBHB population, to evaluate how well each model recovers a complex PSD. Using
Bayesian and frequentist tools, we find that the t-process model gives the most precise PSD results, with uncertainties $43\%$ and $26\%$ narrower than those obtained with the power law and the free spectrum, respectively, while the improvement in accuracy is smaller. Moreover, using the t-process model, we compute isotropic and anisotropic signal-to-noise ratios with median gains of about $46\%$ over the power law and $65\%$ over the free spectrum in the first nine frequency bins. The t-process also returns lower anisotropy p-values and among the frequency bins with $p<0.01$, it allows to localize the loudest binary within the angular resolution of the sky maps in $14.3\%$ of the cases, compared to the $10\%$ for the power law and the $6.2\%$ for the free spectrum.
Read the full abstract ▾
All authors B. E. Moreschi, K. A. Gersbach, G. Shaifullah, S. R. Taylor, A. Sesana
Astrophysics of Galaxies
KDG 162: A Nearby Isolated Star-forming Dwarf Galaxy
Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin et al. (+6 more)
The nearby
dwarf galaxy KDG 162 (also known as KK 153) has recently attracted
attention as a potentially gas-rich, isolated, and low-mass
dwarf galaxy. However, many of these characterizations depend on the true distance to KDG 162. Here we present new Hubble Space
Telescope (HST) imaging that resolves individual
stars down to 3 magnitudes below the tip of the red
giant branch. Using this HST imaging, we determine a distance to KDG 162 of D = 3.48 $\pm$ 0.12 Mpc, somewhat higher than previous determinations. We find KDG 162 to be relatively isolated and lying at the edge of first infall onto the M81 group. We use its
stellar content to measure its recent
star formation history and find that only a modest amount of
star formation can be attributed to within the last $\sim$500 Myr. The present-day
stellar mass outweighs the H I mass by a factor of 2$\times$. The properties of KDG 162 add to an increasingly detailed picture of nearby and isolated low-mass
galaxies. In the future, deeper observations would allow for reaching more age-sensitive populations, enabling the recovery of its
star-formation history back to ancient times.
Read the full abstract ▾
All authors Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin, R. Brent Tully, Rachael Beaton, Andrew Dolphin, Serafim S. Kaisin, Lidia N. Makarova, Edward J. Shaya
High Energy Physics (Theory)
The Cosmological $\delta$-shift
Carolina Figueiredo, Jiajie Mei, Yuyu Mo et al. (+1 more)
We consider the extension of the $\delta$-shift connecting Tr$(\phi^3)$ and pion amplitudes to observables in cosmology. We start in flat-space and explain how one can extract the pion wavefunction and correlators from those of Tr$(\phi^3)$ theory, via a simple kinematic deformation. As opposed to the amplitude, the $\delta$-shift for the wavefunction is no longer a linear deformation on the kinematics since the wavefunction depends on magnitudes rather than the squares of momenta. We "linearize" this deformation by using the frequency representation - allowing us to recast the contribution from any graph as a sum over residues. We then show how this construction extends to de Sitter, and find that, remarkably, in the frequency representation, the pion de Sitter wavefunction and correlators can be formulated in precisely the same way as in flat-space. Amongst other things, this unified formulation reveals a simple universal soft-limit for flat-space and de Sitter, where, in the soft-limit, the wavefunction turns into a sum of wavefunctions in a mixed theory of pions and scalars.
Read the full abstract ▾
All authors Carolina Figueiredo, Jiajie Mei, Yuyu Mo, Francisco Vazão
High Energy Astrophysical Phenomena
Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny
Willem B. Hoogendam, David O. Jones, Christopher J. Storfer et al. (+26 more)
We present photometric and spectroscopic follow-up observations of the strongly-lensed H-poor superluminous
supernova (SLSN) 2025wny at $z = 2.0155$. We use integral-field Keck-II/KCWI spectroscopy to obtain rest-frame ultraviolet spectra spanning $11$ to $61$ days after maximum light. We use Pan-STARRS photometry to constrain the brightest image's magnification, finding $\mu_A=19.4\pm1.6$, a factor of $\sim$2-4 higher than mass-modeling estimates. We fit the Pan-STARRS photometry with a magnetar energy-injection model including $^{56}$Ni decay using the Modular Open Source Fitter for Transients (MOSFiT); the model can reproduce the near-maximum light curve with parameters typical of local universe SLSNe-I, including a magnetar
spin period $P_{\rm spin}=4.1^{+0.7}_{-1.0}\,\mathrm{ms}$ and
magnetic field $B_{\perp}=2.4^{+1.1}_{-0.8}\times10^{14}\,\mathrm{G}$; however, the late-time plateau suggests an additional power source. Spectroscopically, iron-group element line blanketing is virtually absent in the rest-frame UV spectra, and the absorption features match previously identified SLSN-I features from abundance
tomography. Based on narrow ISM line
metallicity estimates, SN 2025wny exploded in a sub-
solar-
metallicity galaxy. From host-
galaxy lines in our rest-frame UV-to-optical spectrum we estimate high-velocity
outflows of $\sim$575 km s$^{-1}$ and an exceptionally high Ly$\alpha$ escape fraction of $f_{esc}^{Ly\alpha}=0.23\pm0.03$. SN 2025wny matches lower-
redshift SLSNe reasonably well. Upcoming surveys like LSST and Roman will discover additional high-
redshift SLSNe, further testing whether SLSNe-I explosions remain consistent at the population level in the early universe.
Read the full abstract ▾
All authors Willem B. Hoogendam, David O. Jones, Christopher J. Storfer, Luca Izzo, Kyle W. Davis, Miranda Y. Kong, Katie Auchettl, Aadya Agrawal, David R. Aguilera-Dena, Kenneth C. Chambers, Siyuan Chen, Thomas de Boer, Ryan J. Foley, Matthew Grayling, Jason T. Hinkle, Jens Hjorth, Mark E. Huber, Chien-Cheng Lin, Thomas B. Lowe, Eugene A. Magnier, Kaisey S. Mandel, C. Tanner Murphey, Gautham Narayan, Gregory S. H. Paek, Kishore C. Patra, Haille M. L. Perkins, Armin Rest, Benjamin J. Shappee, Richard J. Wainscoat
Quantum Physics
Visualizing two qubits
Simon Grosse-Holz
I propose a simple visualization for pure two-
qubit states, constructed from three components: two Bloch balls for the marginal
qubits (the mixed states obtained by ignoring the other
qubit, respectively) and an
entanglement component consisting of a rotoreflection and a contraction. I prove that this picture accurately captures the local and global structure of the relevant state space without gaps or degeneracies: the underlying parametrization is a global diffeomorphism onto the state space. Finally, I use this picture to visualize conditional states, the
entanglement degree(s) of freedom, and single
qubit rotations.
Read the full abstract ▾
Quantum Physics
Quantum Readout Complexity for Normalized Linear Functionals
Roi Vence-Nogueira
Quantum numerical
algorithms often encode a positive solution $q$ in the amplitudes of a
quantum state, while the required scientific output is a normalized linear functional of $q$. Basis measurements produce probabilities determined by squared solution values, while the functional uses the solution values themselves. We study the complexity of this output-interface problem for $F_\phi(q)=\int\phi q\,\mathrm d\nu/\int q\,\mathrm d\nu$ and identify a target-dependent susceptibility $\chi_\phi$ that governs the amount of copies of the solution state needed. For a fixed positive reference state and a neighborhood around it, the optimal number of unknown-state copies is $\Theta\!\left(\chi_0\varepsilon^{-2}\log(1/\beta)\right)$, where $\varepsilon$ is the absolute error tolerance and $\beta$ is the allowed failure probability. We show that two fixed single-copy measurements attain the same rate. We then analyze how this baseline changes when the interface retains classical information, uses adaptive allocation, supplies coherent access, or restricts the allowed solution family. Therefore $\chi_\phi$ quantifies a central cost of using a solution encoded in an $L^2$-normalized
quantum state to estimate an $L^1$-normalized linear observable.
Read the full abstract ▾
Instrumentation and Detectors
A Differentiable Surrogate for Loss-Dominated Ion Beam Transport
Jose M. Munoz-Arias, Laura Ruiz-Arango, Derick Gonzalez-Acevedo et al. (+3 more)
Radioactive
nuclei with extreme
proton-to-
neutron ratios provide unique probes of
nuclear structure, fundamental
symmetries, astrophysical processes, and applications such as medicine. However, their short half-lives and low production rates mean that experiments must work with few desired ions, often amid contaminant backgrounds exceeding the signal by six orders of magnitude. Efficiently isolating, transporting, and delivering these ions through multi-stage apparatus is therefore a central challenge. We introduce a differentiable probabilistic surrogate for ion-beam transport in regimes dominated by particle loss. The model jointly captures the survival probability of ions along the beamline and the evolving phase-space distribution of the surviving particles by combining discrete-time survival analysis with conditional normalizing flows. Applied to a high-dimensional electrostatic beamline, the resulting likelihood enables gradient-based optimization of operating voltages and inference of beam properties from sparse detector observations. Once trained, the surrogate provides millisecond-scale differentiable predictions, transforming particle-tracking simulations with hard losses into an inference-ready model for experimental design, beamline optimization, and future digital twins of experiments with rare
nuclei.
Read the full abstract ▾
All authors Jose M. Munoz-Arias, Laura Ruiz-Arango, Derick Gonzalez-Acevedo, Fabian C. Pastrana-Cruz, Jackson Hacias, Ronald F. Garcia Ruiz
Materials Science
Thermal Diffusivity in Metallic Nanowire Aerogels
Madeline A. Maben, WLNC Namila Liyanage, Cameron S. Jorgensen et al. (+4 more)
Metallic nanowire aerogels combine the functional properties of metals with the high porosity of aerogels. Here, Ag and Cu nanowire aerogels with densities of 20-500 mg cm-3 were synthesized by freeze casting and investigated using lock-in thermography during sequential mechanical compaction. Thermal transport depended strongly on nanowire diameter, with 30 nm Ag nanowires exhibiting substantially lower thermal diffusivity than 60 nm wires, likely due to enhanced surface scattering as the wire diameter approaches the electron mean free path in Ag. Surprisingly, increasing the aerogel density through mechanical compaction reduced the calculated thermal diffusivity by nearly 300x, opposite the conventional expectation that denser materials transport heat more efficiently. Further analysis showed that this decrease is dominated by the thickness term in the thermal diffusivity formalism, while the fitted transport coefficient changes comparatively little. The characteristic thermal
diffusion timescale decreased only modestly during compaction, indicating that densification primarily collapses pore volume without fundamentally restructuring the conductive nanowire network. This behavior resembles
topology-preserving densification, where large
geometric compression produces comparatively small changes in the effective percolative transport pathway. These results show that nanowire aerogels cannot always be treated as homogeneous bulk media, because their macroscopic geometry and conductive network evolve differently during compaction.
Read the full abstract ▾
All authors Madeline A. Maben, WLNC Namila Liyanage, Cameron S. Jorgensen, Erin Marlowe, Kai Liu, Gerd Duscher, Dustin A. Gilbert
Strongly Correlated Electrons
Chiral Central Charge from Real-Space Twist Operator Correlator
Yunlong Zang
Recent years have witnessed substantial progress in the
entanglement-based characterization of
quantum phases of matter, with growing interest in real-space formulas due to their theoretical and experimental relevance. For two-dimensional gapped
quantum systems, we propose a universal real-space formula for the
chiral central charge based on the twist-operator correlator $Z_{g,h}=\langle\psi^{(N)}\rvert\mathcal{T}_A(g)\mathcal{T}_B(h)\mathcal{T}_C(g)\mathcal{T}_C(h)\lvert\psi^{(N)}\rangle$, where $\lvert\psi^{(N)}\rangle=\lvert\psi\rangle^{\otimes N}$ is the $N$-copy state and $g,h\in S_N$ are permutations. The twist operator $\mathcal{T}_R(g)$ permutes the $N$ replicas within region $R$ according to $g$. For pairs $(g,h)$ satisfying the spherical condition, we show that the phase of the correlator is determined by the
chiral central charge $\mathfrak{c}_{-}$ through $Z_{g,h}/\left\lvert Z_{g,h}\right\rvert=(\theta_g\theta_h/\theta_{gh})^{\mathfrak{c}_{-}}$, where $\theta_g^{\mathfrak{c}_{-}}$ is the topological
spin of the twist defect labeled by $g\in S_N$. The construction applies to both bosonic and fermionic systems. We derive the formula within a field-theoretic framework under suitable assumptions and further test it numerically in microscopic
lattice models. Our results establish a universal connection between real-space
entanglement structures and the
chiral central charge, providing a systematic framework for characterizing
chiral topological phases directly on the
lattice.
Read the full abstract ▾
Statistical Mechanics
Algebraic Tensor Network Renormalization and Holographic duality
Chenqi Meng, Tian Lan and Zhengcheng Gu
Emergent generalized
symmetries and the
holographic principle play very important roles in understanding
quantum phase transitions. In recent years, tensor-network renormalization with generalized
symmetry and the corresponding fixed-point tensor formulation have been proposed as a discrete spacetime framework for reformulating conformal field theory. Nevertheless, a complete
holographic formulation within this framework is still lacking, and the current formulation does not directly accommodate sector partition functions that are modular covariant in general. In this work, we formulate $\mathcal{R}$-TNR, which builds the categorical constraints of a fusion category $\mathcal{R}$ into local tensor spaces and preserves these constraints under Loop-TNR. For suitable choices of $\mathcal{R}$, the initial tensors constructed here flow under $\mathcal{R}$-Loop-TNR to stable gapless fixed points. In the Ising, tricritical Ising, and three-state Potts conformal field theory examples, a broad range of initial parameters leads to the same gapless fixed point in each example. The method resolves conformal towers by anyon sector and yields scaling dimensions, conformal
spins, and magnitudes of sector-resolved structure constants with extremely high accuracy compared to previous methods. These results realize a topological bootstrap based on stable
symmetry-topological-order in which finite categorical and
geometric input, together with an initial tensor that need not be fine-tuned, suffices to recover the infrared conformal field theory and its sector-resolved conformal data.
Read the full abstract ▾
Quantum Physics
Energy-constrained two-way capacity bounds for noisy Gaussian channels
Stefano Pirandola
A gap between achievable rates and converse bounds persists for energy-constrained bosonic communication in the presence of excess noise. We derive a unified adaptive weak-converse bound for thermal attenuation, noisy amplification, and additive Gaussian noise under an unconditional mean transmitted-
photon-number constraint. The bound applies to arbitrary adaptive protocols with
quantum memories and constrains the two-way
quantum,
entanglement-distribution, private, and secret-key capacities. It vanishes throughout the
entanglement-breaking region and approaches the corresponding PLOB bound at infinite energy. At finite energy, it improves the evaluated Gaussian squashed-
entanglement and PLOB bounds in relevant parameter regimes, while comparison with hashing rates quantifies the remaining gap to achievability. The result provides a common energy-dependent
benchmark for noisy bosonic Gaussian channels and extends finite-energy converse methods beyond the
quantum-limited setting.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Quantum twisting microscopy as a momentum-resolved probe of quantum geometry and sublattice symmetries
Lucas V. Pupim and Mathias S. Scheurer
In two-dimensional (2D) flat-band systems, as engineered, for instance, by stacking and twisting van der Waals materials, the momentum dependence of the Bloch states is a key factor in determining the interaction-induced emergence of different phases. Hence, methods of probing this form of ”
quantum geometry” are crucial to understanding these systems. Yet, extracting the momentum dependence of the underlying
quantum geometric tensor from measurements is challenging in 2D. Here, we propose employing a
quantum twisting microscope (QTM) with a sublattice-polarized tip to fill this gap. We show how expectation values of sublattice Pauli
matrices can be probed across the scanned momentum path. This allows for the direct measurement of crucial
symmetries characterizing the different candidate instabilities in
graphene-based moiré systems. We furthermore show that the
quantum metric component along the scan direction can also be extracted; the full
quantum geometric tensor is also accessible, given that more than one sublattice polarization can be used. Our work illustrates the potential and extends the versatility of the QTM approach. If implemented in future experiments, this would provide unprecedented access to the
symmetry signatures of the correlated phases and to the underlying
quantum geometry in twisted
bilayer graphene and related systems.
Read the full abstract ▾
Quantum Physics
Observing the magic Mpemba effect in localized dynamics on a digital quantum computer
Han-Ze Li, Xianquan Yan, Yi-Rui Zhang et al. (+3 more)
The Mpemba effect challenges the intuition that states closer to
equilibrium must relax faster. We ask whether an analogous magic-ordering reversal can occur in the generation of
quantum magic (nonstabilizerness), a key resource for universal
quantum computation: can a state with less initial magic overtake one with more and reach its asymptotic value sooner? Here, we uncover interaction-induced dephasing as a distinct mechanism for this magic Mpemba effect, requiring neither transport nor conventional thermalization. For tilted product states in an interacting $\ell$-bit model, a random-phase analysis predicts a reversal of the magic ordering: states with less initial magic attain higher saturated magic, independent of their spatial pattern. Exact simulations of the $\ell$-bit model and localized
spin chains further show that these states also saturate earlier. We observe both features on IBM superconducting
quantum processors. An effective $\ell$-bit implementation accesses long dephasing times at fixed
circuit depth by encoding time in gate angles, while a microscopic
spin model exhibits the reversal universally across initial patterns in the localized regime but only selectively in the ergodic regime. These results establish interaction-induced dephasing as a route to anomalous
quantum-resource relaxation beyond transport-driven thermalizing dynamics.
Read the full abstract ▾
All authors Han-Ze Li, Xianquan Yan, Yi-Rui Zhang, Jian-Xin Zhong, Shuo Liu, Ching Hua Lee
Mesoscale and Nanoscale Physics
Geometric Photon-drag Effect in Unconventional Magnets
Bristi Ghosh, Vivek Pandey, Malay Bandyopadhyay et al. (+2 more)
The
photon-drag effect is a nonlinear optical phenomenon in which the finite momentum carried by incident
photons is transferred to charge carriers, thereby generating a dc photocurrent even in systems with inversion
symmetry. Within the density-
matrix formalism in the velocity gauge, and accounting for nonvertical optical transitions driven by finite
photon momentum, we derive the nonlinear injection and shift conductivities that characterize the
photon-drag photogalvanic response. We investigate these
photon-drag responses in unconventional $p_x$-wave and $d_{x^2-y^2}$-wave magnets in the presence of Rashba
spin-orbit coupling (RSOC), highlighting the distinct roles of
symmetry and
quantum geometry in shaping their nonlinear optical behavior. The key finding of our work is that, despite the broken inversion
symmetry, the conventional photogalvanic response vanishes identically in the $q=0$ limit after Brillouin-zone integration in both unconventional
magnetic phases, resulting in a nonlinear dc photocurrent entirely
photon-drag driven. The two unconventional magnets exhibit qualitatively distinct responses governed by their
symmetry properties: the $p$-wave magnet supports only linear injection and circular shift conductivities, whereas the $d$-wave altermagnet, which simultaneously breaks time-reversal and inversion
symmetries, admits all linear and circular components. Our findings establish altermagnets as a promising platform for controlling
symmetry-selective nonlinear photocurrents and may enable applications in polarization-sensitive photodetection, nonlinear optoelectronics, and
quantum geometric photogalvanics.
Read the full abstract ▾
All authors Bristi Ghosh, Vivek Pandey, Malay Bandyopadhyay, Pankaj Bhalla, Snehasish Nandy
Geophysics
Principal Surface Fault Rupture Hazard: Moving Beyond Aggregate Displacement Metrics
Saba Marmarchinia and Grigorios Lavrentiadis
Structures crossing active faults are subjected to permanent ground deformation that can impose severe demands on infrastructure. Although probabilistic fault displacement hazard analysis (PFDHA) has advanced considerably, existing principal fault displacement models use aggregate displacement, implicitly assuming that overlapping rupture strands contribute simultaneously to site demand. This assumption is suitable for regional hazard characterization but does not represent finite structural dimensions, where only a subset of ruptures may intersect a structure. This study presents a probabilistic framework that reformulates aggregate principal displacement into a rupture-level representation for infrastructure-specific hazard assessment. Using the Fault Displacement Hazard Initiative (FDHI) database of 75 surface-rupturing earthquakes, principal rupture strands are reconstructed from mapped rupture geometries and displacement observations using event- and segment-based coordinate systems. The framework models three quantities: (1) the number of overlapping principal ruptures, (2) partitioning of aggregate displacement among individual rupture strands while preserving the aggregate displacement budget, and (3) the spatial distribution of rupture strands relative to the primary fault trace. These components are integrated into a generalized PFDHA formulation accounting for earthquake magnitude, style of faulting, rupture
curvature, structural footprint, and fault-trace location uncertainty.
Benchmark fault-crossing applications demonstrate the framework's ability to estimate the probability that individual rupture strands intersect a structure and the associated displacement demand. The framework provides a physically consistent extension of aggregate-based models and a basis for infrastructure-specific PFDHA that explicitly accounts for rupture geometry and finite crossing dimensions.
Read the full abstract ▾
Materials Science
Small Distortions, Big Polarization: Tetragonal BaTiO3 Nanoparticles for High-Performance Piezoelectric Nanogenerators
Shivshankar Jokare, Vikash Kushwaha, Mandar Shirolkar et al. (+3 more)
Lead-free ferroelectric BaTiO3 (BTO) nanoparticles with stabilized tetragonal distortion were synthesized via a ligand-assisted sol-gel method to serve as the active piezoelectric phase in high-performance hybrid piezoelectric nanogenerators (PENGs) operating with triboelectric synergy. XRD, Raman spectroscopy, and Pair Distribution Function (PDF) analysis confirmed pseudo-cubic tetragonal BTO nanoparticle, annealed at 900{\deg}C (BTO-900, ~54nm) and well-defined tetragonal BTO annealed at 1200{\deg}C (BTO-1200, ~104nm). Density Functional Theory (DFT) calculations confirmed enhanced Ti-O covalency, stronger Ti 3d-O 2p hybridization, narrower HOMO-LUMO gap, and improved dipole coherence in BTO-900, indicating superior ferroelectric polarization, piezoelectric activity, and charge retention. BTO-900-PDMS PENG device generated a high open-
circuit voltage of ~100 V and stored ~29 {\mu}J energy, and superior capacitor-charging performance of BTO-900, while the optimized BTO-1200 based device showed a higher power density of ~649 {\mu}W cm-2 and short-
circuit current of ~181 {\mu}A. The superior performance of BTO-900 was attributed to enhanced defect-assisted charge trapping, interfacial polarization, and impedance-controlled charge retention. By coupling the intrinsic piezoelectric response of covalency-engineered tetragonal BTO with triboelectric charge generation at the BTO-PDMS interface, this work establishes nanoparticle size and bonding engineering as an effective route to high-output, lead-free piezoelectric nanogenerators for self-powered electronics.
Read the full abstract ▾
All authors Shivshankar Jokare, Vikash Kushwaha, Mandar Shirolkar, Shruti Kharadkar, R. Boomishankar, Smita Chaturvedi
Solar and Stellar Astrophysics
Coronal Mass Ejections from the Young Sun: Deceleration-Powered Solar Energetic Particles as a Self-Extinguishing Forcing of the Early Earth
Olga A. Panasenco
At $\sim$3.9~Ga (
stellar age $\sim$0.6~Gyr), the young Sun was far more magnetically active than today. It launched $\sim$$10^2$ large, fast coronal mass ejections (CMEs) per year into a denser, more magnetized wind. We follow these eruptions to Earth's atmosphere with a semi-analytic model chain. We find that a CME launched at $v_0\sim3\text{--}4\e{3}\unit{km\,s^{-1}}$ dissipates $\Delta E_k\sim6\e{25}\unit{J}$ as it decelerates, an amount set only by its launch and final speeds. Diffusive shock acceleration converts $\sim$10% of this energy into
solar energetic particles (SEPs), whose deposition depth depends mainly on a spectral break energy $E_b$. We show that the stronger field moves the Alfvén surface, inside which the
magnetic field controls the wind, from $\sim$10–25$\,\Rsun$ to $\sim$40–60$\,\Rsun$, so CME shocks deliver over ten times the particle fluence of
flares. Because the forcing is powered by deceleration, it follows the measured wind history ($\dot M\propto t^{-2.3}$) and declines as $\sim t^{-3}$. It was $\sim$50–100 times stronger at 3.9~Ga than at 2~Ga and several hundred times today's level. This decline, strongest when the Sun was faintest, is what greenhouse solutions of the faint young Sun (FYS) problem usually impose by hand. The magnitude is small: SEP-driven $\mathrm{N_2O}$ adds at most a few $\unit{W\,m^{-2}}$ to a 20–40$\unit{W\,m^{-2}}$ greenhouse requirement, and only if a fractal organic haze extends its lifetime. Counting energy deposited below a survival level near 1~hPa, we find the particles fix $\sim$$4\e{10}$–$4\e{11}\unit{mol\,N\,yr^{-1}}$, which could supply prebiotic feedstock to surface pools. The largest uncertainties are $E_b$, the event rate, the survival depth, and the $\mathrm{N_2O}$ lifetime.
Read the full abstract ▾
Quantum Physics
Complexity of self-consistent entanglement certification
Yujie Zhang
In recent work Phys. Rev. X 16, 031057 (2026), we proposed a self-consistent approach to
entanglement certification based on generalized noncontextuality. It requires no prior characterization of the measurement devices and, given access to all local measurements, can certify every entangled state in a Bell
circuit. Here, we study the complexity of this protocol in a finite experiment. At fixed local dimension $d$, we show that the optimal number of distinct local effects needed to reach a trace-distance
entanglement resolution $\gamma$ is $\Theta_d(\gamma^{-(d-1)})$. This scaling is necessary even when the measurements are tailored to the target state. Independent Haar-random projective measurements instead require $\Theta_d(\gamma^{-(d-1)}\log(1/\gamma))$ effects. Finally, we show that, once the exact operational identities are known, $\Theta_d(\gamma^{-2}\log(1/\delta))$ copies of the target state are necessary and sufficient for certification with error probability at most $\delta$. Determining the optimal sample complexity when those identities must instead be inferred from the same finite target-state data remains open.
Read the full abstract ▾
Astrophysics of Galaxies
Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) – IV. Methyl cyanide isotopologues toward BHR71-IRS1
P. Nazari, A. Coutens, J. K. Jørgensen et al. (+16 more)
Methyl cyanide is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions. We add to this number by analyzing data toward BHR71-IRS1 taken as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ~33 GHz frequency range. We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic
equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b). We detect CH3CN, CH3CN $v_8$=1, 13-CH3CN, CH3-13-CN, CH3C-15-N, CH2DCN, and CHD2CN. The column density ratio of 13-CH3CN/CH3-13-CN is around unity, in agreement with previous observations. The CH2DCN/CH3CN ratios are similar for all the low-mass objects but are ~1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-
stellar phase or a different formation timescale of Sgr B2(N2b). The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar
star-formation phase as methanol (i.e., the pre-
stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-
stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.
Read the full abstract ▾
All authors P. Nazari, A. Coutens, J. K. Jørgensen, A. Belloche, A. L. Plunkett, S. Maret, D. Harsono, M. N. Drozdovskaya, J.-E. Lee, F. Cruz-Sáenz de Miera, J. Ferrer Asensio, M. L. R. van 't Hoff, J.-H. Jeong, Á Kóspál, B. A. McGuire, S. Spezzano, Y.-L. Yang, H.-S. Yun, S. Zeng
General Relativity and Quantum Cosmology
Learning When Black Hole Hair Is Observable: Physical Identifiability, Generalization, and Observable Complementarity
Ariadna Uxue Palomino Ylla
High interpolation accuracy does not establish that physical parameters are identifiable. We study this distinction in a controlled Kiselev black hole
benchmark with a validated timelike-emitter and three-dimensional null-geodesic shooting calculation. The exact $k=0$ boundary provides an analytically known null control because the spacetime becomes Schwarzschild and independent of $w_q$. Ringdown is informative for the deformation amplitude $k$, while
photon geometry supplies an independent response direction that resolves much of the $w_q$ degeneracy. Relative to ringdown alone, ringdown plus
photon geometry gives a median pointwise $4.54\times$ gain in minimum singular value and a $2.28\times$ improvement in Jacobian condition number. In grouped physical interpolation, identifiable-$w_q$ normalized mean absolute error decreases from 0.309 to 0.087. Random splitting is more optimistic, while directional extrapolation is substantially harder and split-conformal coverage degrades under distribution shift. A non-learned nearest-model inverse shows that the gain is not confined to the tested learned architectures. A uniform 161-phase audit gives a typical normalized prediction shift of $9.48\times10^{-4}$, while a targeted 321-phase audit resolves the remaining forward-feature comparisons. However, frozen HGB and random-forest tail shifts exceed prespecified robustness thresholds. Thus, physical observable complementarity is supported, but inverse-
estimator robustness remains conditional. This is a theoretical identifiability
benchmark, not an observational constraint.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Mitigating prior-volume effects in galaxy clustering by adopting Mpc over Mpc/h units
Andrea Pezzotta, Alejandro Pérez-Fernández, Giosuè Gambardella et al. (+4 more)
We investigate prior-volume effects in
Bayesian analyses of
galaxy clustering based on state-of-the-art models, such as the EFT and the VDG$_\infty$ model. We show that these effects are largely driven by imposing priors on the model parameters defined in ${\rm Mpc}/h$ units, thereby introducing a spurious correlation with the Hubble parameter $h$, and that they can be strongly mitigated by adopting a more physically motivated formulation in ${\rm Mpc}$ units. We test this approach using a set of synthetic data vectors designed to reproduce the clustering signal expected in a Stage-IV survey across a range of cosmological models, including $\Lambda$CDM, $K$CDM, $w$CDM, and $w_0w_a$CDM. We find that the resulting constraints are largely free from shifts induced during the marginalisation process, even in the challenging $w_0w_a$CDM runs, reducing discrepancies with the fiducial values from several standard deviations to well within $1\sigma$. The performance of this approach is comparable to that of alternative mitigation strategies, such as the adoption of invariant priors or the reparametrisation of nuisance parameters in terms of growth and geometrical amplitudes. For the latter, we find that using $\sigma_{12}$ in place of the commonly adopted $\sigma_8$ to describe the amplitude of density fluctuations improves the performance of the reparametrisation technique, even at high
redshifts, where constraints on the dark-energy equation of state are weaker. We further show that these conclusions hold with the inclusion of additional BAO constraints, and for data sets with reduced statistical power. These results add to the benefits of working with ${\rm Mpc}$ units, avoiding an explicit dependence on $h$, with direct relevance for the analyses of Stage-IV
galaxy surveys.
Read the full abstract ▾
All authors Andrea Pezzotta, Alejandro Pérez-Fernández, Giosuè Gambardella, Ariel G. Sánchez, Alexander Eggemeier, Martin Crocce, Benjamin Camacho-Quevedo