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Physics

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Thursday 25 June

Astrophysics of Galaxies

The Impact and Environment of Massive Stars and Stellar Clusters

Loren Anderson, Jagadheep D. Pandian, Jyotirmoy Dey et al. (+10 more)

Massive stars and stellar clusters shape galactic evolution through powerful feedback mechanisms including radiation pressure, photoionization, stellar winds, and cosmic ray acceleration. However, their impact remains poorly understood due to observational challenges: they are rare, distant on average, and deeply embedded within dense, dusty environments. Radio observations provide a unique window into these processes, as radio emission penetrates obscuring material and traces both thermal free-free emission from ionized gas and non-thermal synchrotron emission from shocks and particle acceleration. The Square Kilometre Array (SKA) will revolutionize massive star studies through unprecedented sensitivity and angular resolution. SKA observations will enable detailed characterization of hierarchical structures within HII regions, measurements of physical conditions through hydrogen, helium, and carbon radio recombination lines (RRLs), and detection of non-thermal emission from cosmic ray acceleration in star-forming regions. SKA will permit systematic measurements of stellar wind mass-loss rates, studies of photoionized gas kinematics and dynamics, and exploration of photodissociation regions surrounding ultracompact HII regions. Additionally, magnetic field strengths can be probed through Zeeman effect observations of RRLs. This chapter discusses the current understanding of massive stars and stellar clusters and their feedback processes. We highlight how SKA observations will advance our knowledge of massive star formation, stellar winds, hierarchical structures in HII regions, cosmic ray acceleration, and magnetic field regulation of star formation - providing crucial insights into feedback mechanisms governing the structure and evolution of the Milky Way and galaxies.
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All authors Loren Anderson, Jagadheep D. Pandian, Jyotirmoy Dey, Marco Padovani, Ramlal Unnikrishnan, Annie Zavagno, Grazia Maria Umana, Jakob van den Eijnden, Giovanni Sabatini, Kimberly L. Emig, Alessio Traficante, Álvaro Sánchez-Monge, D. Anish Roshi

High Energy Physics (Theory)

Soft QED as Open Quantum System: Infrared Cancellation and Soft-Shell Coarse Graining

Soo-Jong Rey

I formulate unresolved soft-photon sector of QED as open quantum system. Resolved charged particles and hard photons form the system, unresolved soft photons form the environment, and basic object is the reduced density matrix. A resolved outcome $f$ of multiple hard particles and photons has probability $P_{f}(i) =\sum_n|\langle f,n|S|i,0\rangle|^2=\langle i|F_f|i\rangle$, with Kraus operators $K_n= {}_{\rm soft} \langle n|S|0 \rangle_{\rm soft}$ and effect $F_f=\sum_nK_n^\dagger\Pi_fK_n$. The SK formulation places unresolved virtual and real terms in one doubled-contour expansion. At one loop they carry the same on-shell eikonal kernel with opposite signs. This elegantly organizes the QED probability: for the same observable, perturbative order, diagrams, and phase space, the OQS gives the same infrared-finite terms as the full-QED. The soft-photon evolution is a unitary coherent-state displacement driven by the scattering current. The equal-history identity of influence functional exactly normalizes this soft evolution; together with the soft-photon theorem it removes the IR divergent leading-soft factor from inclusive probability. I also derive explicit leading-soft QED realization of scale-parametrized Lindblad evolution on a fixed hard-branch space. Tracing an infinitesimal soft-photon shell produces diagonal jump operators whose entries are fixed by the corresponding eikonal emission amplitudes. The finite-shell map is a completely positive unital Schur channel and, in the sharp scale-invariant leading-soft regime, a dephasing semigroup of a completely-positive-divisible scale flow. The resulting logarithmic visibility slope and monotonic purity loss are off-diagonal predictions of the reduced-state description. The same controlled-displacement dilation gives the Sudakov probability, Poisson soft-photon multiplicities, and the bremsstrahlung number spectrum.
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Materials Science

Ultrafast non-thermal suppression of ferroelectricity by carrier screening in LiNbO3

Man Tou Wong, Zhuquan Zhang, Zi-Jie Liu et al. (+1 more)

Ferroelectric materials are key to energy-efficient electronics, memory, and optical applications. While charge carriers typically screen and suppress ferroelectricity, their role under nonequilibrium conditions remains elusive. Here, we use femtosecond laser pulses to liberate trapped carriers in LiNbO3 and track the response using time-resolved second-harmonic generation and stimulated Raman scattering. Even dilute photoexcited carriers induce a rapid yet enduring suppression of polarization and Raman susceptibility. Fluence- and temperature-dependent analyses confirm the suppression is non-thermal and arises from transient carrier screening. These findings reveal an efficient, reversible, and symmetry-preserving mechanism to modulate ferroelectricity on ultrafast timescales, offering a new route to control ferroic and competing quantum phases.
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All authors Man Tou Wong, Zhuquan Zhang, Zi-Jie Liu, Keith A. Nelson

Strongly Correlated Electrons

SU(4) Heisenberg model on the hyperhoneycomb lattice

I. V. Lukin and A. G. Sotnikov

We study the ground state of the SU(4) Heisenberg model on the hyperhoneycomb lattice using three-dimensional projected entangled pair states. We show that it is possible to compute physical observables for the ground states using loop expansions, which converge quickly on tree-like lattices. Our extrapolations to the limit of infinite bond dimensions point toward gapless spin-liquid ground state.
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High Energy Physics (Theory)

Free-Field Construction of Heterotic String Compactified on Calabi-Yau Orbifolds via Correspondence with $\mathcal{N}{=}2$ SCFT Minimal Models

Alexander Belavin, Doron Gepner and Grigory Makarov

We establish a correspondence between the free-field construction and the minimal-model construction of the Calabi–Yau sector of the four-dimensional heterotic string compactified on Berglund–Hübsch type Calabi–Yau manifolds and their orbifolds. For Fermat-type polynomials the Calabi–Yau vertex operators expressed in terms of free fields are shown to correspond to products of primary fields of $\mathcal{N}{=}2$ minimal models. Using this correspondence we verify modular invariance of the free-field construction and extend it to Berglund–Hübsch Calabi–Yau orbifolds, deriving the conditions on complete vertex operators that parallel those of the minimal-model construction.
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Atomic Physics

Non-dipole effects in two-photon double ionization of the K-shell of a beryllium-like atomic ion

Alexey N. Hopersky, Alexey M. Nadolinsky, Rustam V. Koneev et al. (+1 more)

In the second order of the non-relativistic quantum perturbation theory and outside the framework of the dipole approximation for the operator of the radiation transition between continuum-spectrum states, the analytical structures and absolute values of the generalized cross-sections of the two-photon double ionization of the K-shell of beryllium-like ions of titanium (Ti18+), iron (Fe22+) and zinc (Zn26+) atoms were predicted. It has been established that taking into account non-dipole effects by several orders of magnitude (giant non-dipole effect) reduces the generalized cross-sections calculated within the framework of the dipole approximation. It has also been established that at high (12.5 - 28 keV) energies of the absorbed photons, the generalized cross-section of the two-photon double ionization of the K-shell is several orders of magnitude greater than the generalized cross-section of the single ionization. At the same time, as was to be expected, the transition from a neon-like ion to a beryllium-like ion is accompanied by a significant increase in the role of non-dipole effects.
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All authors Alexey N. Hopersky, Alexey M. Nadolinsky, Rustam V. Koneev, Julia N. Kolesnikova

High Energy Physics (Phenomenology)

Light and heavy meson production in small collision systems

Ivan Vitev

Recent results from the LHC on oxygen-oxygen (O-O) and neon-neon (Ne-Ne) collisions open a new window for investigating the interplay of cold nuclear matter (CNM) and quark-gluon plasma (QGP) effects in small collision systems. Building upon recent theoretical work on particle production dynamics in heavy-ion reactions, we present an updated study of light and heavy hadron modification relative to the proton-proton baseline in these systems for selected centralities. Our analysis combines perturbative QCD and hydrodynamic simulations to quantify initial-state effect, collisional energy loss, and medium-induced radiative corrections. We give theoretical predictions at both midrapidity and forward rapidity that can be confronted with ALICE, ATLAS, CMS, and LHCb measurements. Through comparison to the available data, we discuss the relative importance of CNM and QGP effects in O-O and Ne-Ne systems and the role of the heavy quark mass. Our analysis aims to clarify the onset of collective and deconfined behavior in small systems and to provide new insights into the transport properties of matter. We further argue that investigation of other observable such as energy correlators and quarkonia can lead to a more complete picture of QGP formation in these collisions.
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Statistical Mechanics

Jarzynski equality for counterwork under reversed memory-filtered driving

Pierre Nazé

We introduce a counterwork functional generated by a sign-inverting memory-filtered effective protocol. Given an imposed protocol $\lambda(t)$, the effective protocol $\Lambda(t)$ is obtained by applying an active protocol-memory kernel to $\dot{\lambda}(t)$, rather than by invoking a passive bath response. The counterwork is then the ordinary Hamiltonian work associated with $H(\Gamma,\Lambda(t))$, so that Jarzynski's equality applies directly to it. When $\Lambda(t)$ reverses the endpoints of $\lambda(t)$, the corresponding free-energy difference satisfies $\Delta F_C=-\Delta F_W$, and the exponential average of the counterwork is the reciprocal of that of the original work. We derive the kernel normalization realizing this reversed displacement and show, by Jensen's inequality, that the product of the exponentials of the average work and counterwork is bounded by unity, implying $\langle C\rangle+\langle W\rangle\geq0$. Thus negative average counterwork is possible only when compensated by the average work of the original operation. We further discuss the counteroperation under incomplete thermodynamic information, showing that the robust strategy is to enforce endpoint reversal while minimizing dissipated counterwork.
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General Relativity and Quantum Cosmology

Determination of the metric of a Schwarzschild black hole surrounded by a halo of dark matter

M. Castillo Alarcón, Leonel Bixano, I. A. Sarmiento-Alvarado et al. (+2 more)

Following the landmark acquisition of the first image of a black hole, systems comprising a black hole enveloped by a dark matter halo have attracted considerable attention. This work implements a novel method to analyze the structure of a system composed of a Schwarzschild black hole and a dark matter halo modeled as an anisotropic fluid, while ensuring that the proposed metric constitutes an exact solution of the Einstein field equations. Numerical results show that the connection between the temporal and radial metric functions preserves an inverse relationship, namely $A(r) \approx 1/B(r)$. Furthermore, we analytically demonstrate that the resulting functions satisfy $A(r)B(r) = 1 + \mathcal{O}(10^{-6})$, in excellent agreement with the numerical findings. In addition, the Einstein equations imply that the variation of the product $A(r)B(r)$ is governed by the factor $\varepsilon_h=\frac{8\pi G\rho_0r_0^2}{c^2}$. Finally, we show that the interior Schwarzschild region and the exterior dark matter halo can be joined smoothly via a regular Darmois Israel junction, without generating any thin shell curvature steps. To assess the observational implications of the model, we compare its theoretical predictions for the pericenter precession of the S2 star and the angular size of the shadow of Sgr A*. In both cases, the predicted deviations remain within the observational uncertainties reported by the GRAVITY Collaboration and the Event Horizon Telescope (EHT), respectively. These results demonstrate that the proposed black hole dark matter halo configuration is not only mathematically consistent, but also compatible with current observational constraints.
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All authors M. Castillo Alarcón, Leonel Bixano, I. A. Sarmiento-Alvarado, Claudio Salas-Pérez, Tonatiuh Matos

Lattice Field Theory

Sampling the Schwinger Model with Gauge-Equivariant Diffusion

Octavio Vega and Aida X. El-Khadra

We present a first study of a diffusion-based approach to accelerated sampling of the $N_f = 2$ lattice Schwinger model. Our work is inspired by recent and growing successes in developing such generative models for ensemble generation in LFT to overcome the well-known critical slowing down problem. We train a U(1)-equivariant score-based generative model to sample gauge link configurations from the marginal Schwinger model. By computing model likelihoods, we obtain unbiased estimates for observables that closely match those produced by MCMC simulations. We also demonstrate improvement over HMC as measured qualitatively by a reduction in topological freezing near critical parameters.
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Astrophysics of Galaxies

Self-interacting dark matter promotes bar formation in disk galaxies

Shashank Dattathri, Frank C. van den Bosch, HanYuan Zhang et al. (+4 more)

Despite its remarkable success on large scales, the standard $\Lambda$CDM paradigm faces persistent small-scale challenges that have motivated alternative models for the dark sector. Self-interacting dark matter (SIDM) offers a compelling possibility, in which dark matter particles can scatter off each other. Stellar bars are a ubiquitous feature of disk galaxies across cosmic time. Bars are dynamically coupled to their host galaxy's dark matter halo, and therefore their properties provide a powerful probe of the nature and distribution of dark matter. In this paper, we use idealized, high-resolution $N$-body simulations and analytic calculations based on kinetic theory to study bar formation and evolution in disk galaxies embedded in SIDM halos. We find that compared with collisionless CDM, SIDM produces bars that form earlier and grow to larger amplitudes, even for modest self-interaction cross sections. In several cases, disks that remain stable in CDM, including kinematically hot and dark-matter-dominated disks, develop strong bars in SIDM. This accelerated bar growth occurs because self-interactions broaden the bar-halo resonances and enhance angular momentum transfer from the stellar disk to the halo. We explicitly show that this phenomenon is not related to core formation in SIDM halos. At late times, gravothermal core collapse can raise the central dark matter density enough to weaken or dissolve the bar. These results suggest that the abundance, strength, and redshift evolution of barred galaxies offer a promising observational route to constraining dark matter self-interactions, particularly in light of the growing sample of high-redshift bars revealed by JWST.
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All authors Shashank Dattathri, Frank C. van den Bosch, HanYuan Zhang, Martin D. Weinberg, Eugene Vasiliev, Priyamvada Natarajan, Vasily Belokurov

Astrophysics of Galaxies

The Bright Future of the Dark and Dim Universe

N. Deg, Alejandro Benitez-Llambay, Elizabeth A. K. Adams et al. (+5 more)

This chapter investigates the low-mass frontier of galaxy formation through two complementary populations: the starless Reionization-Limited HI Clouds (RELHICs) that trace the “dark” Universe, and the faint, gas-rich galaxies that define the “dim” Universe. RELHICs offer pristine laboratories for probing the distribution of DM on sub-galactic scales, providing a direct test of the Lambda Cold Dark Matter ($\Lambda$CDM) model predictions. The dim Universe provides statistical constraints on cosmology, galaxy formation and evolution, as well as baryoninc physics through key observables including the low-mass end of the neutral-hydrogen mass function (HIMF), the neutral-hydrogen velocity function (HIVF), and the low-mass end of the baryonic Tully-Fisher relation (bTFR). This chapter outlines core science questions that can be tackled leveraging radio observations of both the dark and dim Universe. Additionally, it outlines strategies to identify RELHICs amid tidal or pressure-confined contaminants, while providing observational predictions for the dim Universe. The Square Kilometre Array (SKA) in its mid-frequency Array Assembly 4 (AA4) configuration will, for the first time, resolve the internal gas structure of nearby RELHICs and build deep, wide-area datasets that definitively constrain the HIMF, HIVF, and bTFR down to masses of $10^{6}~\msol$ – offering a complete observational framework to test the $\Lambda$CDM paradigm and the baryonic processes that shape the faint end of galaxy formation.
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All authors N. Deg, Alejandro Benitez-Llambay, Elizabeth A. K. Adams, N. Chamba, V. Kilborn, Filippo M. Maccagni, T. O'Beirne, K. Spekkens

Mesoscale and Nanoscale Physics

Collection, characterization, and precision measurement of levitated charged nanoparticles

B. E. Kane, Joyce Coppock, Sunghyun Kim et al. (+1 more)

We describe apparatus and experimental procedures for high stability precision measurements of levitated nanoscale particles confined in an ion trap in high vacuum. We discuss methods for particle generation and collection using electrospray emission, for rapid characterization by direct imaging of thermal motion, and for transfer of the particle from the trap where it is collected to a separate analysis trap in order to achieve better vacuum and lower noise. In the analysis trap at high vacuum (pressure $p\simeq10^{-8}$ Torr), we employ thermostatic control of the trapped particle oscillation amplitudes, allowing long-term, precision measurements of oscillation frequencies, from which the charge to mass ratio ($Q/M$) can be deduced. Under these conditions, we achieve $Q/M$ measurement precision approaching $10^{-5}$. This sensitivity will enable, for example, investigations of the surface chemistry of $\mu$m-scale levitated materials in ultra-high vacuum environments.
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All authors B. E. Kane, Joyce Coppock, Sunghyun Kim, Sarah Westgate

Earth and Planetary Astrophysics

From Young to Older Disks: JWST/MIRI Evidence for Fading Molecular Emission and Hints for Elevated C/O in Upper Scorpius

Chengyan Xie, Ilaria Pascucci, Feng Long et al. (+23 more)

We present JWST/MIRI spectroscopy of 14 disks in the older (~5-10 Myr) Upper Scorpius (USco) association and use slab of gas in local thermal equilibrium to infer basic gas properties. We find that half of these disks are molecular rich, with detections of H$_2$O, CO$_2$, HCN, C$_2$H$_2$, and H$_2$, while the other half are molecular poor, showing no molecular emission other than H$_2$. We further combine this sample with 10 other USco disks from the AGE-PRO program and compare the combined older sample to young (~1-3 Myr) JDISCS Cycle~1 systems, which are analyzed in a similar manner. We find that USco disks have lower detection rates of major molecular species but a significantly higher detection rate of rarer C-bearing molecules such as C$_4$H$_2$. At a given accretion luminosity, molecular line luminosities are systematically lower in USco than in young disks, and the scaling relations with accretion luminosity differ between the two populations. Moreover, we find that about half of the older disks, preferentially the millimeter faint, and likely more compact disks, have observable mass ratios of C- to O-bearing molecules that are higher than the maximum values in the young sample. These results point to reduced inner-disk molecular gas masses, cooler emitting layers, and higher inner gas C/O ratios in older disks, the latter being consistent with pebble drift. Taken together, our findings provide evidence for chemical evolution of inner disk gas from young to older systems, with important implications for the accretion of primordial planetary atmospheres.
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All authors Chengyan Xie, Ilaria Pascucci, Feng Long, Uma Gorti, Andrea Banzatti, Richard Booth, Klaus Pontoppidan, Tamara Molyarova, John Carpenter, Min Fang, Yao Liu, Eshan Raul, Ke Zhang, Steve Ertel, Jordan Stone, Aaron Empey, Carlo F. Manara, Paola Pinilla, Colette Salyk, Benoit Tabone, Miguel Vioque, Lucas Cieza, Giovanni Rosotti, James Miley, Geoffrey A. Blake, Abygail Waggoner

Earth and Planetary Astrophysics

Chemical Divergence and Water Depletion: Gas Properties of Evolved Upper Scorpius Disks Revealed by JWST/MIRI

Eshan Raul, Ke Zhang, Abygail Waggoner et al. (+25 more)

Tracing the chemical evolution of protoplanetary disks over time requires observations of disks at different ages. However, most JWST/MIRI surveys published to date have targeted younger ($\sim$1-3 Myr) rather than older systems. We present the results of a JWST/MIRI MRS survey of the inner regions of 10 protoplanetary disks (ages $\sim$2-6 Myr, spectral types M0-M4.5) in the Upper Scorpius region previously characterized by the ALMA AGE-PRO large program. Using MCMC slab modeling, we fit to a wide variety of detected molecules, including H$_2$O, CO, C$_2$H$_2$, $^{13}$CCH$_2$, HCN, HC$_3$N, CO$_2$, $^{13}$CO$_2$, C$_2$H$_6$, C$_4$H$_2$, and OH, as well as C$_6$H$_6$, CH$_3$, and H$_2$ visually. We classify each disk along two independent axes-a Water Classification based on H$_2$O line luminosity (Water-Rich, Water-Poor, or Water-Absent) and a Chemotype based on the dominant non-water chemistry (Organic-Rich, CO$_2$-Dominated, or Molecule-Absent)-and find an unexpectedly high diversity of distinct chemical compositions within our population. We leverage the heterogeneity of detected molecules in our sample to present new characteristic "diagnostic" wavelength regions for most species. We find that carbon-based molecules consistently exhibit markedly lower excitation temperatures ($\lesssim$300 K) compared to younger ($\sim$1-3 Myr) star-forming regions ($\sim$600-1000 K), hinting at relatively colder molecular reservoirs. We also determine that Upper Scorpius disks show systematically lower water luminosities by factors of 10-1000. In particular, disks with strong carbon-based molecular features but no observed H$_2$O defy expectations of an inner-disk dust cavity or a low ($\lesssim3$) $R_{\rm gas}/R_{\rm dust}$ ratio, instead suggesting that the presence of a strong outer-disk dust trap largely controls the chemical outcome of the terrestrial planet-forming region.
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All authors Eshan Raul, Ke Zhang, Abygail Waggoner, Chengyan Xie, Nicholas Tallon, Andrea Banzatti, Colette Salyk, Klaus Pontoppidan, Ilaria Pascucci, Nicole Arulanantham, Miguel Vioque, Aaron Empey, Carlo Manara, Geoffrey A. Blake, Paola Pinilla, Feng Long, Jinghuai Yao, Jayatee Kanwar, Naman S. Bajaj, María José Colmenares, Till Kaeufer, Benoit Tabone, Edwin Bergin, Lucas A. Cieza, Mayank Narang, James Miley, Sebastiaan Krijt, Giovanni Rosotti

Optics

Universal framework for the design of near-zero refractive index photonic crystals

Adrien Debacq and Michaël Lobet

Near-zero-index (NZI) media are of great interest for controlling light-matter interactions, but homogeneous NZI materials in the telecom band remain limited and often suffer from significant losses. Photonic crystals provide an attractive alternative due to their tunability and use of low-loss constituent materials. This work presents a predictive framework for designing epsilon-near-zero (ENZ), mu-near-zero (MNZ), and epsilon-and-mu-near-zero (EMNZ) photonic crystals. We demonstrate an equivalence between Dirac cones and EMNZ behavior, showing that a Dirac cone at the Gamma point is both necessary and sufficient to obtain an effective EMNZ response under normal incidence. This result implies that the presence of a Dirac cone fully determines the NZI response of a photonic crystal, independent of the material composition. The prediction is based on mode symmetry universality and effective medium theory. The approach enables switching between ENZ-MNZ and EMNZ regimes through geometric tuning of the unit cell. It is validated on triangular and rectangular lattices. Overall, this work provides a predictive design strategy for NZI photonic crystals, replacing trial-and-error optimization. It may also impact metamaterials in the telecom regime and applications in quantum communication.
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Astrophysics of Galaxies

JWST Reveals Compact Nuclear Starbursts Masquerading as AGNs in Metal-Poor Dwarfs: Where Are the Accreting Intermediate-Mass Black Holes?

William Matzko, Shobita Satyapal, Jeffrey D. Mckaig et al. (+18 more)

We present JWST/NIRSpec spectroscopy of the low-mass, metal-poor galaxy SDSS~J160135.95+311353.7 (J1601), selected for its extreme mid-infrared colors and compact nuclear emission, placing it within widely used WISE color diagnostics for active galactic nuclei (AGNs). Despite this selection, we find no evidence for coronal lines, X-ray emission, or variability typically associated with accretion activity. We compare J1601 to SDSS~J120122.30+021108.3 (J1201), a similar but lower-mass, more metal-poor system studied previously (Doan, 2025). Both galaxies host compact nuclear starbursts but differ in their stellar populations and dust properties: J1601 shows CO bandhead absorption indicative of red supergiants, weak nuclear Wolf–Rayet features, and a circumnuclear PAH ring, consistent with a more developed recent starburst, while J1201 is more dust-enshrouded and chemically primitive. Despite these differences, neither system shows evidence for AGN activity, indicating that the absence of accretion is not simply due to evolutionary timing. Photoionization models show that the weakness of high-ionization emission cannot be explained by low metallicity alone, implying a genuine deficit of hard ionizing photons. Crucially, the red mid-infrared colors in both systems originate from compact, unresolved nuclear emission confined to the nuclear star cluster. These results demonstrate that compact nuclear starbursts can mimic AGN-like mid-infrared colors without accretion, and that commonly used AGN diagnostics may not uniquely identify accreting black holes in metal-poor dwarf galaxies. Our findings suggest that such systems may not provide the conditions required for efficient black hole growth and/or may lie near or below the regime where black hole seeds can form.
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All authors William Matzko, Shobita Satyapal, Jeffrey D. Mckaig, Sara Doan, Michael McDonald, Archana Aravindan, Gabriela Canalizo, Jenna M. Cann, Nicholas P. Abel, Omkar Bait, Laura Blecha, Torsten Böker, Thomas Bohn, Jacqueline Fischer, Stephanie LaMassa, Suzanne C. Madden, Mallory Molina, Barry Rothberg, D. Schaerer, Anil Seth, Remington O. Sexton.

High Energy Astrophysical Phenomena

Modelling Dissipative Dynamics of r-mode Instability in Hybrid Stars

Khushbu Zala and Sreemoyee Sarkar

Compact star cores reach extreme densities and may contain exotic dense-matter phases. Information about the exotic interiors of rapidly rotating pulsars can be inferred from r-mode oscillations, whose stability is governed by viscous dissipation. In this work, we model a compact star containing a possible mixed phase of hadronic and quark matter and employ a hybrid statistical framework based on Bayesian inference to infer the dissipation time scales associated with the hybrid phase. Using low-mass X-ray binaries (LMXB) timing observations together with mass-radius constraints from the Neutron Star Interior Composition Explorer (NICER) mission, we estimate the shear and bulk viscosity contributions to r-mode damping for a hybrid star of two layers. Our inference yields shear and bulk viscous dissipation time scales of $\tau_s=(4.99^{+0.49}_{-0.52}) \times 10^8 T^{\frac{5}{3}}$s and $\tau_B=(2.150^{+1.23}_{-0.60}) \times 10^{19} (T^4 10^{-12}+T^2 10^{-6})^{-1}\Omega^{-2}$s respectively. The timescales thus obtained can be implemented to obtain the minima of the star's rotation frequency at $\Omega=451.87$ Hz at temperature $T=0.259$ MeV for a hybrid star of mass $1.5$ $M_{\odot}$ and $\Omega=517.47$ Hz at $T=0.234$ MeV for $M=1.75 M_{\odot}$. We find that the instability window obtained through the inference framework effectively explains the observed stability of millisecond pulsars in both the radio and LMXB populations, particularly for XTE J0929-314 and XTE J1807-294, J0437-4715, J2124-3358, respectively. These results demonstrate that Bayesian inference combined with r-mode phenomenology provides a powerful and observationally consistent framework for constraining the transport properties of dense hybrid matter.
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Chemical Physics

Nonlinear Freezing of Vibrational Polariton Transport via Mesoscale Simulations

Xinwei Ji and Tao E. Li

Two-dimensional real-space imaging of vibrational polariton transport in planar Fabry–Pérot microcavities is numerically simulated via the mesoscale cavity molecular dynamics approach, which self-consistently propagates $\sim\!2\times10^4$ realistic molecular simulation cells on a two-dimensional grid coupled to the same number of cavity modes. Beyond the well-known polariton ballistic-to-diffusive turnover in the linear response regime, these atomistic simulations reveal a nonlinear freezing mechanism of vibrational polariton transport, i.e., under strong pumping of the upper polariton, the initially ballistically propagating upper polariton completely freezes and localizes energy to molecules at specific locations. This mechanism originates from pump-induced breaking of the in-plane translation symmetry: significant molecular excitations at the pulse hot spot broaden the polariton density of states, thus funneling population to the $k_{\parallel}\rightarrow 0$ band edge with vanishing group velocities. Overall, our work provides numerical insights for exploring novel mechanisms of vibrational polaritons.
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Chemical Physics

Direct imaging of enantiomer-specific orientation dynamics in unidirectionally rotating chiral molecules

Kenta Mizuse, Ilia Tutunnikov, Long Xu et al. (+7 more)

Selectively controlling the dynamics of molecular enantiomers underlies advances across chemistry, biology, and physics, yet direct imaging of enantiomer-specific motion has so far remained elusive. Here, we image ultrafast enantioselective orientation dynamics in isolated chiral molecules. Unidirectional coherent rotation induced by a femtosecond laser-pulse pair generates equal and opposite out-of-plane orientations of the two enantiomers. Applying this scheme to 2-methyloxirane, we follow the rotational wave packets by time-resolved Coulomb explosion imaging with two orthogonally arranged detectors. The measured angular distributions reveal that the unidirectional rotation is identical for both enantiomers, while the out-of-plane orientations are mirror images that persist through both early-time quasi-classical and quantum dynamics regimes, in quantitative agreement with simulations. We demonstrate that full angular distributions provide richer dynamical information, with some qualitatively different distributions yielding similar orientation factors upon integration. Our approach opens a route to real-time observation and control of chiral dynamics in the gas phase.
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All authors Kenta Mizuse, Ilia Tutunnikov, Long Xu, Yuhei Oyagi, Naoya Sakamoto, Ryo Kondo, Allan Huang, Roman V. Krems, Ilya Sh. Averbukh, Yasuhiro Ohshima

General Relativity and Quantum Cosmology

The crust of dark-matter admixed neutron stars: bulk properties and torsional oscillations

Jiayi Zhang and Hector O. Silva

We study how dark matter (DM) impacts the crust and the spectrum of torsional crust oscillations of dark-matter-admixed neutron stars (DANSs). We construct two-fluid equilibrium solutions wherein baryonic and DM interact gravitationally only, adopting a unified nuclear equation of state for the former and a fermionic equation of state with repulsive self-interaction for the latter. At fixed total gravitational mass and DM mass fraction, we find that DM reduces the crust thickness in comparison to pure baryonic-matter neutron stars (NSs). The thinning of the crust is negligible when most of the DM distribution extends beyond the star's baryonic surface. However, the crust thickness can decrease by as much as 12% when the DM distribution is within the star's baryonic surface, i.e., when the star has a "dark core." We support these results by deriving approximate analytical formulas for the crust thickness that agree with our numerical calculations at the sub-percent level in best case scenarios. Next, we derive the equation that describes crustal torsional modes of DANSs in the relativistic Cowling approximation. We find that the oscillation frequencies are in general higher than those of a comparable pure baryonic-matter NS, with the largest frequency shifts happening in the same parameter space where the crust thickness decreases the most. Moreover, we study the degeneracy between DM and baryonic-crustal microphysics effects on these modes. As an example, we study electron screening, which softens the crust's shear modulus, thus decreasing the frequencies. We find that the degeneracy between the competing effects of DM and electron screening can be broken in some regions of the parameter space we explored. Should they be measured, our results suggest that torsional oscillations could be used to infer the existence of a DM core within massive NSs. (Abridged)
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High Energy Physics (Phenomenology)

The one-point charge correlator in deep inelastic scattering

Haotian Cao and Frank Petriello

In this work, we propose a novel definition of the one-point charge correlator (QC) adapted to the Breit frame in deep-inelastic scattering (DIS). We demonstrate that this observable is infrared and collinear (IRC) safe, ensuring its perturbative calculability. Utilizing soft-collinear effective theory (SCET), we systematically analyze the QC in both the forward and back-to-back limits. In the forward limit, we introduce the nucleon charge correlator as a novel non-perturbative object that encodes the multi-dimensional microscopic structure of the nucleon. In the back-to-back limit, the QC establishes a direct correspondence with transverse momentum-dependent distributions (TMDs), enabling its description within the standard TMD factorization formalism. The singular distributions are derived within SCET and are verified by the full QCD calculations up to $\mathcal{O}(\alpha_s^2)$. The corresponding collinear logarithms are resummed to all orders with the accuracy of NLL (${\cal{O}}(\alpha_s^n L^{n-1})$), while the transverse momentum-dependent logarithms are resummed to all orders with the accuracy of $N^3$LL for the unpolarized distribution and N$^2$LL for the Sivers asymmetry.
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Plasma Physics

Gyrokinetic Theory of Linear Gravitational Flute Interchanges with Flow Shear Stabilization

Zheng Yang Tan and Ian Abel

A collisionless electrostatic gyrokinetic theory is developed to describe how the presence of a differential velocity shear can help stabilize linear gravitational flute interchanges in slab geometry. This is made possible because the velocity shear acts to increase the perpendicular wavenumber of the unstable modes with time. Eventually, a threshold wavenumber is crossed where the effect of gyroaveraging, captured by the Bessel function in the gyrokinetic equation, results in a damping of the instability by nature of these Bessel functions being a decaying sinusoidal. However, transient amplification, responsible for subcritical turbulence, can still occur. Numerical comparisons are made with a Magnetohydrodynamic model with gyroviscous corrections as well as the GX gyrokinetic code. It is demonstrated that an increasing shear acts not only to accelerate the stabilization effect but also to reduce the overall transient amplification.
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Earth and Planetary Astrophysics

The Dynamical Origin of Millimetre-Sized Sporadic Meteoroids

Tam Do, Peter Brown and Petr Pokorný

Determining the relative contributions of cometary and asteroidal sources to the sporadic meteoroid population remains a longstanding challenge, particularly because commonly used orbit-based classification criteria have not been rigorously validated for meteoroids. We evaluate the efficacy of several established orbit-based criteria for meteoroid classification. These include the Whipple $K$-criterion, Kresák $Pe$-criterion, the Tisserand invariant with respect to Jupiter (T$_J$), and a recent classification based on aphelion distance proposed by Borovička. Our validations suggest that $K$ and $Pe$ are most reliable at recovering whether a meteoroid was released from a cometary or asteroidal parent. We applied these criteria to a suite of 386 observed millimetre-sized meteoroids to try to constrain their original source populations. Our analysis used the observed orbit co-variances to backward integrate a suite of clones for each meteoroid to statistically evaluate their dynamical origin. We find that if meteoroids are released in the last ~150-200 kyr, there is a dividing velocity of below 17 km/s where meteoroids in the millimetre to centimetre size range impacting Earth are predominantly asteroidal in origin, independent of the orbital criteria used. Above 17 km/s, the fraction of dynamically cometary meteoroids increases, although a definitively cometary dominated population does not arise until velocities of 27 km/s or higher. For ages older than 200 kyr, lower velocity meteoroids at Earth in the mm-sized range may be a mix of either cometary or asteroidal.
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Plasma Physics

Sawtooth suppression by flux pumping on HBT-EP

Boting Li, J.P. Levesque, G.A. Navratil et al. (+1 more)

This study examines the mechanisms underlying sawtooth suppression in the High Beta Tokamak-Extended Pulse (HBT-EP) device. It is observed that strong-intensity sawtooth activities correlate with reduced-amplitude MHD edge modes which are identified as $m/n=3/1$ external kink modes (XK), while sawtooth suppression correlates with larger and saturated edge mode amplitudes. To further investigate these correlations, the plasma-wall coupling was manipulated by adjusting the positions of the conducting walls in HBT-EP. It was found that strong sawtooth events occur when the normalized wall radius $b/a$ is within a critical value. This implies that the plasma-wall distance must be sufficiently small to ensure effective stabilization of the edge mode. Even slight differences in major radius result in significantly different discharge styles, categorized as “sawtoothing discharges” and “sawtooth-suppressed discharges” respectively. Through a series of mode structure analyses, we confirm the coexistence and coupling of the $m/n=1/1$ helical core (HC), $m/n=2/1$ tearing mode (TM), and $m/n=3/1$ XK during sawtooth suppression, and that this coupling induces anomalous current broadening. Based on these findings, we conclude that sawtooth suppression in the HBT-EP tokamak is consistent with the process of magnetic flux pumping.
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All authors Boting Li, J.P. Levesque, G.A. Navratil, M.E. Mauel

Instrumentation and Methods for Astrophysics · Cross-listed from cs.DL

A&A community survey on the future of scientific publishing: Credibility over speed, fairness over profit, human judgment over automation

João Alves, Arūnas Kučinskas, Charlotte Van Rooyen et al. (+7 more)

(Abridged) Scientific publishing is undergoing major change, driven by a shift toward open access (OA), the rise of artificial intelligence (AI), and growing demands for transparency, reproducibility, and equity. At the same time, rapid growth in article output strains editors and reviewers and means that metrics and speed can eclipse quality and rigor. To better understand how the community is responding, Astronomy & Astrophysics (A&A) commissioned the {A&A Survey on Trends and Challenges in Scientific Publishing}, which documents community opinion on journal choice, peer review, OA, research evaluation, and the role of AI, with the goal of informing future editorial policies and the wider conversation on sustainable, ethical, and equitable scientific communication. Distributed online in May 2025 to \SI{28787} A&A authors and co-authors, the survey drew \SI{2944} responses from 69 countries by its closing date. The responses were clear. Journal quality and reputation are the most decisive factors in deciding where to publish, followed by cost. The principal worry about peer review is reviewer expertise and fairness rather than speed. Citation counts are still an important consideration, but many respondents want broader, more qualitative measures of impact. The majority prefers public or institutional funding for OA, and views on AI are polarized, with widespread acceptance of administrative and language assistance but firm opposition to autonomous decision-making or content generation. Integrity, credibility, and fairness are common themes in every section of the responses. Overall, the survey portrays an engaged community that values quality over speed, fairness over profit, and human oversight over automation, providing A&A with clear insight into community preference and a solid framework for shaping future policies on OA, peer review, and the responsible integration of AI.
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All authors João Alves, Arūnas Kučinskas, Charlotte Van Rooyen, Marc Audard, Pierre-Alain Duc, David Elbaz, Thierry Forveille, Laszlo L. Kiss, Tiago Pereira, Eva Villaver

Optics

Analysis of Nonlinear Random Polarization in Dispersive Dielectrics

Nathan L. Gibson and Emmanuel E. Oguadimma

We present a study on the time-domain propagation of electromagnetic waves in dielectric materials modeled by a nonlinear Debye medium with random perturbations. Polynomial Chaos Expansions are employed to transform the random nonlinear Debye polarization model into a deterministic framework. We extend the Yee discretization to the resulting coupled system, establish second order accuracy, and verify convergence numerically. We investigate the sensitivity of nonlinear properties to uncertainty, particularly when the amplitude of the input signal is large. Given the challenges in manufacturing where uncertainties can cause optimal parameters to vary and potentially disrupt nonlinear effects, our approach incorporates these uncertainties within the simulation. This can enable the model-based design identification of realizable materials that maintain their desired effects despite variations. The findings from this study contribute to a deeper understanding of wave propagation in complex media, with potential implications for applications in optical communications, material science, and electromagnetic wave control.
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Quantum Physics · Cross-listed from cs.IT

A Quantum Method of Types

Arick Grootveld

The method of types is a fundamental tool in classical information theory, with applications ranging from composite hypothesis testing and universal source coding to the capacity of arbitrarily varying channels. In this work we introduce an empirical operator acting as a quantum analog of the empirical distribution. We show that this empirical operator satisfies combinatorial and large-deviation bounds, which in combination describe a quantum method of types. As an application, we use our method to prove a universal achievability result for composite quantum hypothesis testing.
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High Energy Physics (Phenomenology)

Collider Probes of Dark Energy Microphysics

Chaitanya Bashyam, Alfredo Gurrola, Andres Florez et al. (+1 more)

The physical origin of dark energy remains one of the most profound open questions in modern physics. Although cosmological observations tightly constrain the equation of state parameter $w$, this information alone does not reveal the underlying microphysics, as many distinct theoretical models can reproduce the same expansion history. A key discriminator among these models is the sound speed of dark energy perturbations, yet this quantity remains largely unconstrained by current astrophysical observations. In this work, we propose a fundamentally new approach: using collider measurements of beyond-the-Standard-Model (BSM) mediator resonances as a probe of dark energy microphysics. We construct a unified effective-field-theory framework in which a dynamical dark energy scalar is coupled, through symmetry-motivated derivative interactions, to a pseudoscalar mediator in the 2HDM+$a$ model. These interactions naturally induce invisible decays and modify the propagation of the BSM mediator in a dark energy background, leading to measurable distortions of resonance properties at colliders such as the LHC. We show that the decay widths, branching ratios, and kinematic structure of the mediator resonance become sensitive to the propagation properties of dark energy fluctuations, in particular the sound speed. As a result, collider observables provide a direct and complementary handle on dark energy microphysics, with the potential to distinguish between models that are otherwise indistinguishable through cosmology alone. Our results establish a new paradigm in which high-energy collider experiments can probe the physics of cosmic acceleration, revealing a connection between the smallest and largest scales in nature and opening a novel experimental pathway to uncover the fundamental origin of dark energy.
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All authors Chaitanya Bashyam, Alfredo Gurrola, Andres Florez, Cristian Rodriguez

Cosmology and Nongalactic Astrophysics

Simulation-Based Inference for Cluster Cosmology with Set-Based Neural Network Architectures

S. Zelmer, E. Bulbul, K. Lehman et al. (+18 more)

The unprecedented statistical power of galaxy cluster catalogs from the SRG (Spectrum Roentgen Gamma)/eROSITA All-Sky Survey provides a unique opportunity to place stringent constraints on cosmological models through measurements of structure growth. Fully exploiting the potential of these large X-ray-selected cluster samples, however, requires robust statistical frameworks that accurately connect observable quantities to the underlying cosmological parameters. We develop and implement a simulation-based inference (SBI) framework for cosmological parameter estimation using a realistic mock-generation pipeline calibrated on eRASS1 simulations. Synthetic galaxy cluster catalogs are propagated through the survey selection function to produce mock eRASS1 observations that reproduce the data's statistical properties. At the core of the method lies a set-based neural network (GNN on sets) that encodes information from individual clusters and is coupled to a masked autoregressive flow for flexible posterior density estimation. This approach enables the use of the full cluster-level information content without compressing the observables into binned summary statistics. Our framework recovers the input cosmologies within the inferred uncertainties, and passes calibration tests, demonstrating robustness in the presence of realistic survey effects. We obtain mock constraints of 11.5% on $\Omega_m$ and 4.4% on $\sigma_8$ averaged over a suite of simulated cluster catalogs matching the effective sample size of the data set (3,259 clusters). We achieve a precision comparable to that obtained with traditional MCMC analyses based on substantially larger cluster samples. The framework is readily extensible to more complex forward models and additional observables. This work highlights the potential of SBI methods for next-generation large-scale structure analyses with forthcoming X-ray cluster surveys.
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All authors S. Zelmer, E. Bulbul, K. Lehman, S. Krippendorf, E. Artis, S. Grandis, N. Clerc, Z. Ding, L. Fiorino, V. Ghirardini, M. Kluge, N. Malavasi, A. Merloni, T. Mistele, K. Nandra, M. E. Ramos-Ceja, J. S. Sanders, F. Pacaud, A. von der Linden, J. Weller, X. Zhang