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Monday 21 September

Cosmology and Nongalactic Astrophysics

Tangled $\tau$: Planck CMB Constraints on Flash Reionization

Param Upadhyay, Elisa G. M. Ferreira and Evan McDonough

Recent cosmological tensions have renewed interest in the role of reionization in parameter inference, and flash reionization has been proposed as a transient high-redshift ionization episode that can increase the Thomson optical depth while remaining compatible with CMB polarization data. In this work, we present the first Markov Chain Monte Carlo analysis of the flash reionization model fit to Planck cosmic microwave background temperature, polarization, and lensing data. We perform this analysis using Planck PR4 data in $\Lambda$CDM with flash reionization. We find that CMB data allow a wide range for the redshift of the flash, $z_{\rm flash}$, but with constraints that are tightly correlated with the peak ionization fraction $x_{\rm flash}$. We find constraints $x_{\rm flash}=0.24 ^{+0.13} _{-0.07}$ and $x_{\rm flash}= 0.15 ^{+0.07} _{ - 0.05}$ for the benchmark flash reionization scenarios with fixed $z_{\rm flash}=20$ and $25$ respectively. The standard $\Lambda$CDM parameters do not exhibit any significant shifts, and in particular, the total optical depth to reionization is not appreciably changed, with $\tau=0.061 \pm 0.007$ in flash reionization as compared to $\tau=0.059\pm 0.006$ in the standard tanh parametrization. We repeat this analysis for Planck PR3 data in place of PR4, and find that the mild preference for a flash is replaced by 95% CL upper bounds, given by $x_{\rm flash}<0.28$ and $x_{\rm flash}<0.18$ for $z_{\rm flash}=20$ and $25$, respectively, from Planck PR3 data.
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High Energy Physics (Phenomenology)

Interpreting the LZ 248 keV Event using Dark QCD

Francesco Sannino and Jessica Turner

The LUX-ZEPLIN (LZ) Collaboration has reported a nuclear-recoil candidate with reconstructed energy $248\pm23_{\rm stat}\pm23_{\rm sys}\,\mathrm{keV}$. We investigate an interpretation in terms of composite inelastic dark matter, in which a dimension-ten operator splits the lightest baryon of a confining $SU(3)_{\rm D}$ theory into two Majorana states. Endothermic scattering is mediated by a leptophobic vector coupled to baryon number. For a dark-baryon mass of $1\,\mathrm{TeV}$ and a splitting of $300\,\mathrm{keV}$, a reference nucleon cross section of $6.5\times10^{-43}\,\mathrm{cm^2}$ lies within LZ's published two-sided 90% confidence interval. This benchmark fixes $M_V/g_B\simeq9.9\,\mathrm{TeV}$, where $M_V$ and $g_B$ are the mediator mass and baryon-number gauge coupling, and is compatible with solar neutrino and dijet constraints.
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Astrophysics of Galaxies

EPOCHS-DR2 I: Expanded data release and properties of $6.5<z<16.5$ photometrically selected galaxies across NIRCam deep fields covering $\sim700\,\rm arcmin^2$ with the galfind software

Duncan Austin, Christopher J. Conselice, Thomas Harvey et al. (+14 more)

We present the \epochstwo\ sample of $2452$ star forming galaxies at $6.5<z_{\rm phot}<16.5$ produced using the \galfind\ photometric pipeline across $\sim650-740~\mathrm{arcmin}^2$ in six of the most widely used deep, blank field \jwst/NIRCam imaging surveys. $293$ galaxies are spectroscopically confirmed and a spectroscopic–photometric redshift comparison yields a normalized median absolute deviation, $\sigma_{\rm NMAD}=0.017$, an $\eta=4.3\%$ outlier rate, and a mean offset $\langle\Delta z\rangle=-0.022$. We find $34$ little red dots (LRDs) with “V–shaped” SEDs, as well as $69$ L–type, $36$ T–type, and $2$ compact Y–type brown dwarf candidates, which we remove from our sample. The fiducial sample yields a flattening $\beta_{\rm UV}-M_{\rm UV}$ relation with only moderately blue median $\beta_{\rm UV}(M_{\rm UV}=-19)=-2.32^{+0.08}_{-0.07}$ at $z\simeq12.5$, implying dust-polluted stellar populations at the highest redshifts. A “gold” sample of $62$ sources are identified at $z_{\rm phot}>10.5$, $\sim85\%$ of which are without NIRSpec follow-up, including $15$ candidates at $z_{\rm phot}>13.5$ across a diverse range of proper sizes $30\,\rm pc\lesssim r_{\rm c}\lesssim1.5\,\rm kpc$ and UV slopes $-4.0\lesssim\beta_{\rm UV}\lesssim-1.5$. Two very promising candidates stand out, GS-W-4608 and GN-Med-1881, with $\beta_{\rm UV}\lesssim-3$, $\gtrsim1.6\,\rm mag$ \lya\ break colors, and F335M and F410M detections which improve their high-redshift solution robustness. Complementary to our high-redshift sample, this public data release provides the community with optical/NIR catalogs, empirical PSFs, and \eazypy, \bagpipes, and \bdfinder\ SED fitting results, enhancing the legacy value of photometric JWST data in the upcoming era of wide-field imaging datasets with Euclid and Roman.
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All authors Duncan Austin, Christopher J. Conselice, Thomas Harvey, Nathan J. Adams, Louis Quilley, Jordan C. J. D'Silva, Vadim Rusakov, Qiong Li, Lewi Westcott, Caio Goolsby, James Arcidiacono, Kai Madgwick, William J. Roper, Brenda Frye, Norman A. Grogin, Rafael Ortiz III, Rogier Windhorst

High Energy Physics (Phenomenology)

A closer look at the LZ 248 keV event through the lens of cosmic-ray boosted dark matter

Bhavesh Chauhan, Soham Sahasrabuddhe and Manibrata Sen

We investigate whether cosmic ray boosted dark matter (CRDM) can explain the 248 keV nuclear recoil event observed by the LUX-ZEPLIN (LZ) collaboration. We consider spin-dependent interactions, mediated by a pseudoscalar, and incorporate relativistic kinematics in CRDM production, propagation, and detection. We find that spin-dependent interactions can produce sufficient number of nuclear recoils in the observed region of interest, without populating events at lower energies, which have not been observed. However, for a benchmark pseudoscalar interaction corresponding to the non-relativistic effective operator $\mathbb{O}_6$, the coupling required to produce the observed event corresponds to an energy scale comparable to the momentum transfer scales, thus making contact interaction approach challenging. Instead, we find that a pseudoscalar mediator with mass $\sim 300\,$MeV and $O(1)$ couplings can provide a promising solution to this unexplained event.
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Accelerator Physics

Bayesian Optimization of The Relativistic Heavy Ion Collider Luminosity via $s^*$ Control

Xiaofeng Gu, Benjamin Coe, Guillaume Robert-Demolaize et al. (+7 more)

Maximizing luminosity at the interaction point (IP) requires the collision location $s_{IP}$ to coincide with the longitudinal position of the minimum beta function, $s^$. Accurate optics measurements and control of $s^$ are therefore essential for luminosity optimization. At the Relativistic Heavy Ion Collider (RHIC), average horizontal beta-beat measurements between operating IPs are approximately $20%$, with significant variation in measured $s^*$. Precise control of the beam waist position $s^$ is particularly challenging for modern high-energy colliders with short bunch lengths and large crossing angles. We present an online Bayesian optimization (BO) application using the GPTune framework to optimize sPHENIX luminosity through $s^$ control at RHIC. GPTune was first validated at the RHIC Electron Beam Ion Source (EBIS), where it achieved up to a $70%$ increase in beam intensity over the baseline, although experienced operators could reach similar performance with longer manual tuning. The framework was subsequently deployed during sPHENIX operations. Using an intensity-normalized Zero-Degree Calorimeter (ZDC) signal as the optimization objective, due to the unavailability of the live sPHENIX MVTX signal, GPTune identified local luminosity maxima, recovered from intentionally degraded $s^$ configurations, and revealed residual horizontal and vertical waist offsets in the interaction region. These results demonstrate the robustness and efficiency of Bayesian optimization for real-time collider tuning under noisy, time-varying conditions. The $s^$ control methodology provides a promising tool for precision luminosity optimization and is particularly relevant to next-generation short-bunch colliders such as the Electron-Ion Collider (EIC).
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All authors Xiaofeng Gu, Benjamin Coe, Guillaume Robert-Demolaize, Takeshi Kanesue, Masahiro Okamura, William Fung, Yue Hao, Ji Qiang, Xiaoye S. Li, Yang Liu

Nuclear Theory

Accessing zero-point fluctuations in high-energy nuclear collisions

Jean-Paul Blaizot and Jean-Yves Ollitrault

Ultracentral high-energy collisions between identical nuclei are very sensitive to the size and shape of the frozen configuration of nucleons at the instant of the collision, an information that is encoded in the ground state wave functions of the colliding nuclei. The relative standard deviation of the size of the colliding system soon after the collision has recently been inferred from event-by-event fluctuations of the momentum per particle in collisions of $^{208}$Pb nuclei at the LHC, and since a single collision event produces thousands of particles, this information is very precise. We connect this measurement to the magnitude of the zero-point fluctuations of the radius of the lead nucleus. The value that is extracted from the data is compatible with predictions from nuclear-structure calculations, but is overestimated by classical Glauber-type modeling of high-energy collisions. The role of the Pauli principle in suppressing the fluctuations is underlined. It leads to a distinctive $A$ dependence that could be checked in collisions of smaller systems.
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Mesoscale and Nanoscale Physics

Collective Coordinate Dynamics of Antiferromagnet: Gravity by Quantum Metric

Kuangyin Deng and Ran Cheng

The collective coordinate dynamics of antiferromagnetic and ferrimagnetic textures emerges as a geodesic equation governed by the quantum geometry of the CP$^1$ state associated with the Néel vector, rendering an effective Riemannian gravity and a Lorentz force in the texture motion. This unveils a physical scenario fundamentally distinct from the Thiele equation widely used for ferromagnetic textures, which is inertialess without any gravity analogy. Applying our framework to an optically driven ultrafast antiferromagnetic domain wall, we can explain the helicity-dependent asymmetric motion observed experimentally and predict a vibrantly breathing wall width.
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Solar and Stellar Astrophysics

Elemental Abundances of Cool Stars: A Spectroscopic Framework Applied to Five Planet-Host Stars

Nicole Gromek, Drew Weisserman, Ryan Cloutier et al. (+2 more)

Stellar elemental abundances provide important constraints on the chemical environments from which planets form. M and late-K dwarfs are prime targets for the characterization of small exoplanets, yet their complex spectra make accurate elemental abundance measurements challenging. In this work, we present a spectral synthesis-based framework to derive detailed abundances for cool stars from high-resolution, near-infrared spectra. We apply our framework to SPIRou YJHK spectra of five planet-host stars–GJ 9827, K2-18, TOI-1201, TOI-1685, and Barnard's Star–and derive abundances of C, O, Na, Mg, Al, Si, K, Ca, Ti, Cr, Mn, and Fe for all five stars, plus Sc, V, and Ni for a subset, with typical uncertainties of $\lesssim 0.1$ dex. Our recovered metallicities and elemental abundances are broadly consistent with expected trends and previous literature analyses of these stars. We derive stellar ratios of C/O, Mg/Si, Fe/Mg, and Fe/O and find that all five systems are broadly consistent with solar ratios, with the exception of the metal-poor Barnard's Star ([M/H] $= -0.33 \pm 0.06$ dex), which is substantially iron-poor ([Fe/H] $= -0.722 \pm 0.085$ dex). Our results establish stellar chemical baselines for interior structure and atmospheric studies of these planetary systems with the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST), while highlighting the remaining model-dependent limitations of precise abundance analyses for cool stars.
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All authors Nicole Gromek, Drew Weisserman, Ryan Cloutier, Alexandrine L'Heureux, Charles Cadieux

High Energy Astrophysical Phenomena

PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field IV: X-Ray Variability Analysis

Ross Silver, Francesca Civano, Xiurui Zhao et al. (+31 more)

NuSTAR and XMM-Newton have observed the James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-Domain Field (TDF) for almost five contiguous years starting in 2019. In that time, the NEP X-ray survey has accumulated 3.5 Ms and 228 ks of quasi-simultaneous NuSTAR and XMM-Newton observations, respectively. This paper presents variability results for the 112 NuSTAR and 453 XMM-Newton sources detected in this field, based solely on the X-ray photometric data. Four NuSTAR sources and 11 XMM-Newton sources varied in at least one band at >=99% confidence. The sources with redshift measurements show a relationship between luminosity and variability with 74% of variable sources brighter than 5x the sensitivity limit of the survey. This is supported by about 1/3 of sources with more than 400 counts detected being variable and only 4 sources with fewer counts showing variability. Variability timescales are not well determined, but variability amplitude tends to be larger on longer timescales.
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All authors Ross Silver, Francesca Civano, Xiurui Zhao, Samantha Creech, S. P. Willner, Christopher N. A. Willmer, Rogier A. Windhorst, Haojing Yan, Anton M. Koekemoer, Rosalia O'Brien, Rafael Ortiz III, Rolf A. Jansen, Gibson B. Bowling, Payaswini Saikia, W. Peter Maksym, Nico Cappelluti, Francesca Fornasini, Massimo Ricotti, Timothy Carleton, Seth H. Cohen, Rachel Honor, Jake Summers, Jordan C. J. D'Silva, Sibasish Laha, Dan Coe, Christopher J. Conselice, Jose M. Diego, Simon P. Driver, Brenda Frye, Norman A. Grogin, Madeline A. Marshall, Nor Pirzkal, Aaron Robotham, Russell E. Ryan Jr

High Energy Physics (Phenomenology)

On the failure of the $12\%$ rule in $J/\psi$ and $\psi(2S)$ decays

Arthur Vereijken and Francesco Giacosa

The $12\%$ rule relates hadronic decays of the $J/\psi$ and $\psi(2S)$ through the ratio of their wave functions at the origin, but is strongly violated in several vector–pseudoscalar ($VP$) channels, most prominently in the $\rho\pi$ one. We study these decays within an effective chiral framework including strong and electromagnetic interactions, with the latter implemented through vector meson dominance. The $\psi(2S)\to VP$ data are described well by a relatively minimal model with three free parameters, yielding $\chi^2_{\rm red}\simeq 6.71/(9-3)=1.12$. In contrast, the corresponding description of the $J/\psi$ decays is insufficient ($\chi^2{\rm _{red}}\simeq 132/(11-3)=16.5$) and requires additional $\mathrm{SU}(3)$ flavor breaking and electromagnetic contributions for a fair agreement with data: $\chi^2_{\rm red}\simeq 9.87/(11-6)= 1.97$. In the past, a small mixing of $J/\psi$ with an invisible vector glueball was considered as a way to describe the decay patterns. However, we will show that our extended fits are `de facto' equivalent to those where a vector glueball mixes with the $J/\psi$, so that we cannot distinguish whether or not the vector glueball is present. Our results suggest that an important part of the $\rho\pi$ puzzle may arise from additional contributions to the $J/\psi\to VP$ amplitudes rather than from a suppression mechanism specific to the $\psi(2S)$.
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Mesoscale and Nanoscale Physics

Model of the magnon Kerr effect in a highly anisotropic ferromagnet

Davit Petrosyan, Hiroki Matsumoto, Hanchen Wang et al. (+3 more)

The magnon Kerr effect is a nonlinear phenomenon that occurs universally in any ferromagnet with finite magnetic anisotropy. It manifests itself as a magnon population-dependent change in the magnon dispersion relation. Here, we derive the Hamiltonian for the magnon Kerr effect for a thin film with uniaxial anisotropy. We consider the external field, parallel, perpendicular, and at an intermediate angle to the anisotropy axis, and determine the Kerr coefficient in each case. We show how the nonlinearity scales for different magnetic materials as a function of magnon frequency and magnetic sample volume. Moreover, we derive the equations of motion for a hybrid cavity-magnon system with such thin-film magnon Kerr nonlinearity, to obtain populations of photons and magnons, and scattering matrix terms for the microwave transmission of the cavity, relevant for experimental observations.
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All authors Davit Petrosyan, Hiroki Matsumoto, Hanchen Wang, Richard Schlitz, Pietro Gambardella, William Legrand

High Energy Physics (Theory)

Towards All-Order Locality in the Higher-Spin Holomorphic Zero-Form Sector

D.A. Valerev

This work addresses the construction of local interaction vertices in the holomorphic zero-form sector obtained from Vasiliev equations. We focus on a requirement on zero-form vertices, previously proposed in a less restrictive form in arXiv:2208.02004, which, together with spinor spin-locality, guarantees space-time spin-locality. Necessary and sufficient conditions on the holomorphic one-form sector vertices are derived that ensure the existence of holomorphic zero-form vertices satisfying this requirement. As a concrete demonstration, the proposed scheme is applied to compute the spin-local holomorphic $\eta^2$ zero-form sector vertex, a result that goes beyond previous work where only spinor spin-locality was established. These findings lay the groundwork for a systematic all-order construction of local vertices in higher-spin theory.
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Quantum Physics

Tight entropy contraction beyond detailed balance

Li Gao and Jingyu Guo

We establish quantitative entropy contraction bounds for finite-dimensional quantum channels beyond detailed balance. For channels compatible with a faithful conditional expectation, we show that GNS (Gelfand–Naimark–Segal) norm contraction yields relative entropy contraction with only a logarithmic loss in the dimensional constant. For quantum Markov semigroups with a faithful asymptotic conditional expectation, this gives a lower bound on the complete modified logarithmic Sobolev constant in terms of the GNS spectral gap. The bounds allow initial entanglement with an external environment and are independent of its system size. Applications to alternating reservoir pulses and continuously coupled energy ladders give bounds with optimal size dependence.
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High Energy Physics (Experiment)

Search for a top-philic heavy resonance in association with top quarks in $pp$ collisions at $\sqrt{s} = $ 13 TeV and 13.6 TeV with the ATLAS detector

ATLAS Collaboration

A search for a new top-philic vector boson ($Z'$) produced in association with a top-quark or a pair of top quarks, and decaying into a top quark pair is presented. The search uses $pp$ collision data collected by the ATLAS detector at the Large Hadron Collider at centre-of-mass energies of $\sqrt{s} =$ 13 TeV and 13.6 TeV, corresponding to integrated luminosities of 140 fb$^{-1}$ and 56 fb$^{-1}$, respectively. Events containing exactly two same-sign leptons or at least three leptons (electrons or muons) are selected. A transformer-based classifier parameterised as a function of the $Z'$ mass is used to optimise the signal-to-background discrimination. The results are interpreted in a simplified model with a colour-singlet vector boson coupled to top quarks with coupling strength $c_t$ and chirality angle $\theta$. No significant excess is observed above the expected Standard Model background. A $Z'$ boson with mass below 1150 GeV is excluded at 95% confidence level for a benchmark scenario with $c_t = 1$ and $\theta = 0$, with an expected limit of 1250 GeV.
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Cosmology and Nongalactic Astrophysics

Two-dimensional weak lensing shear for cluster mass, concentration, ellipticity and miscentering estimation

Calum Murray, Martin Kilbinger and Constantin Payerne

The effects of weak gravitational lensing induced by clusters of galaxies makes it possible to constrain their dark matter distribution. In general mass estimates from weak lensing are made by compressing the two-dimensional shear-field into one-dimension. In this work we build a forward model of the two-dimensional reduced-shear field around a galaxy cluster, including the non-Gaussian correlated large-scale structure from N-body simulations, the uncorrelated line-of-sight structure, cluster miscentering and ellipticity. We then use simulation-based inference to obtain posteriors on the cluster mass, concentration, miscentering and ellipticity from the full field. The two-dimensional approach leads to improvements on cluster mass constraints by up to 20%. We show that this is due to a better treatment of the spatially correlated noise across the shear field. There is also significant improvements on the cluster concentration and miscentering. Whilst improvements are also made to the estimation of cluster ellipticity, the constraints are still prior dependent for these individual cluster constraints. We also quantify the impact of the line-of-sight structure on the constraints. Neglecting it underestimates the mass uncertainty by up to a factor of $2$ for the most massive clusters.
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Cosmology and Nongalactic Astrophysics

Merlin: Fast and flexible 3x2pt cosmology with simulation-based inference

Alexandra Wernersson, Guillermo Franco-Abellán and Guadalupe Cañas-Herrera

We present Merlin, a simulation-based inference (SBI) pipeline to perform cosmological analyses of 3x2pt summary statistics: cosmic shear, galaxy clustering and the cross-correlation power spectra. Our approach combines Marginal Neural Ratio Estimation (MNRE) with 3x2pt angular power spectra predictions from the cloelib library, although the pipeline is readily extensible to other cosmology libraries. We demonstrate this pipeline on a realistic setting representative of a Stage-IV photometric survey, with a 50-dimensional parameter space describing cosmology and a wide range of systematic effects. We find posteriors that are in excellent agreement with the nested sampler Nautilus, while reducing the number of required CPU-hours by two orders of magnitude. Because the generation of training data and the training of inference networks are decoupled processes, a single simulation bank can be reused to perform inference under different analysis choices, further improving the simulator-efficiency. We illustrate this flexibility by applying scale cuts, varying the survey area, and removing cosmic shear from the data vector (2x2pt), all at zero extra model evaluations, whereas sampling-based methods need costly re-runs for each case. The Merlin code is publicly available on GitHub.
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Quantum Physics

Improving the Loss Tolerance of Heralded Photonic GHZ States for Long-Distance Device-Independent Conference Key Agreement

Yazeed K. Alwehaibi, Makoto Ishihara, Shakib Daryanoosh et al. (+6 more)

Heralded multipartite entanglement distribution is a key requirement for device-independent conference key agreement (DI-CKA) over lossy quantum networks. Although locally equivalent in the absence of loss, different single-rail photon-number encodings of Greenberger–Horne–Zeilinger (GHZ) states respond differently to photon loss. Here, we investigate the critical detection efficiencies for detection-loophole-free parity–CHSH violations of computational-basis GHZ states—a coherent superposition of the vacuum and an $n$-photon component—and of fixed-photon-number GHZ states, deriving exact analytical conditions for both. We show that for states that are not permutation symmetric, such as the latter, the assignment of measurement roles to physical modes affects loss tolerance. We introduce a star-network protocol employing heterogeneous sources to directly herald the loss-tolerant vacuum-$n$-photon GHZ states while retaining the favourable long-distance scaling $O(\eta_{\text{c}}^{n/2})$, where $\eta_{\text{c}}$ is the channel transmittance. For four users, we characterize the heralded state under photon loss and show that tunable source parameters allow genuine multipartite entanglement to persist at any finite channel distance. With ideal Pauli and displacement-based measurements, our protocol achieves positive DI-CKA key rates at lower detection efficiencies than previous schemes, while retaining comparable or greater rates and communication distances at high efficiency. Overall, our work improves the loss tolerance of heralded photonic GHZ states for DI-CKA both by directly heralding a more loss-tolerant encoding and by optimizing existing schemes. These results identify photon-number encoding, source architecture, and measurement-role assignment as key design parameters for loss-resilient multipartite quantum networks, offering a practical route toward near-term DI-CKA.
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All authors Yazeed K. Alwehaibi, Makoto Ishihara, Shakib Daryanoosh, Ewan Mer, Shang Yu, Wojciech Roga, Ian A. Walmsley, Masahiro Takeoka, Raj B. Patel

Nuclear Theory

Ruling out nucleonic direct Urca cooling in low-mass neutron stars using nuclear data

Gabriele Montefusco, Pietro Klausner, Marco Antonelli et al. (+3 more)

Connecting nuclear experiments to neutron star composition requires controlling the extrapolation of experimental information beyond the densities probed in the laboratory. We combine a broad set of nuclear structure observables and INDRA-FAZIA isospin-transport data within a Bayesian inference of the dense matter equation of state (EoS). To limit uncontrolled extrapolation to high density, we employ a flexible asymptotically causal metamodel whose neutron star posteriors are comparable to those obtained with agnostic EoS models. The nuclear structure information is propagated through its full multidimensional distribution of correlated nuclear matter parameters, while the density-dependent INDRA-FAZIA likelihood is evaluated directly along each sampled metamodel symmetry energy curve. These two sources of laboratory information give compatible constraints on the symmetry energy, and their combination preserves agreement with finite nuclear observables. When combined with ab initio chiral effective field theory calculations and astrophysical observations, all these constraints substantially improve the determination of central proton fractions in low-mass neutron stars, while leaving larger uncertainties for massive stars. Within the adopted nucleonic metamodel, the reduced probability of large proton fractions strongly disfavors electronic direct-Urca onset at or below $1.4\,M_\odot$: its posterior probability falls from $\sim20\%$ with chiral and astrophysical constraints alone to below $1\%$ when the laboratory information is included.
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All authors Gabriele Montefusco, Pietro Klausner, Marco Antonelli, Caterina Ciampi, Diego Gruyer, Francesca Gulminelli

High Energy Physics (Theory)

Chiral Carroll string near Schwarzschild black hole

Kedar S. Kolekar

We obtain the action for the chiral Carroll string moving in a curved string-Carroll target spacetime from a Carroll expansion, in powers of the speed of light $c$, of the action for the relativistic closed bosonic string. Applying this setup to a classical closed bosonic string approaching the $4$-dimensional Schwarzschild black hole, we study the dynamics of the string when it behaves as a chiral Carroll string with the near-horizon string-Carroll expanded geometry as the target spacetime. We find that the chiral Carroll string can have either left-moving or right-moving fluctuations on the horizon, while exhibiting a non-trivial motion in the Rindler spacetime which depends on these horizon fluctuations.
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Quantum Physics

A thermal microwave bus for neutral atom quantum computing

Matthew J.H. Kendall, Christopher J. Watson, Michael Ben Shem et al. (+1 more)

High-fidelity two-qubit gates in neutral-atom arrays rely on the Rydberg blockade, which is intrinsically short ranged and requires long range connectivity to be achieved through atom shuttling. We propose a four level architecture, where the typical ground state qubit can be leveraged for its long lifetime and the Rydberg states couple to a microwave cavity, allowing for long range cavity mediated gates. We first find the thermal dependence of two established protocols, the dispersive iSWAP native to the Tavis-Cummings model and the Controlled phase gate generated from driving the cavity. We simulate them under the presence of Rydberg decay, thermal photons, finite cavity linewidth and find fidelities which accompany closed form bounds. We then introduce the bichromatic Raman gate, which only virtually populates the Rydberg states and cancels dispersive shifts to mitigate both atomic and cavity decay, achieving a fidelity of $F = 0.997$. Finally, we consider a full optical tweezer array in a microwave cavity, and show that using a cavity mediated gate to close the periodic boundaries of the toric code shortens an error correction round by a factor of 2.3 for realistic array sizes. This was then applied to the wider family of Bivariate bicycle codes, and we find that it shortens a round of the gross code by a factor of 4.8.
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All authors Matthew J.H. Kendall, Christopher J. Watson, Michael Ben Shem, Jonathan D. Breeze

General Relativity and Quantum Cosmology

Observational Features of Nonsingular Rotating Black Holes in the Dark-Energy Dominated Universe

Ramon Torres

Recent DESI baryon acoustic oscillation measurements, combined with cosmic microwave background and type-Ia supernova data, suggest that dark energy may evolve with cosmic time. Along a cosmological background, an evolving dark-energy density can be expressed locally as a function of a monotonic curvature invariant, motivating an effective curvature-dependent cosmological term. Moreover, quantum field theory in curved spacetime and approaches to quantum gravity with running gravitational couplings provide complementary motivations for exploring such a term. Here we study how the phenomenology of nonsingular rotating black holes embedded in a Universe dominated by dark energy can differ substantially from that of the Kerr and Kerr–de Sitter geometries. The problem is directly formulated in phase space using a null geodesic super-Hamiltonian and a Mino-type parameter. The shadows of the black holes are calculated by backward ray tracing from a zero-angular-momentum observer. We define and analyze a comprehensive set of standard shadow observables, characterizing the size, shape, and displacement of the shadow. We show that the area of the shadow and its vertical diameter provide particularly clear signatures of a running cosmological term. In this way, joint analyses of multiple strong-field observables and of several black holes with different masses and spins could provide a realistic route to tightly constraining, or potentially measuring, the effective regularization scale behind the running of the cosmological term and statistically distinguishing the non-singular black hole geometry from Kerr/Kerr-dS solutions.
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Astrophysics of Galaxies

Galaxy evolution in the post-merger regime. V - Atomic gas evolution traced by ALFALFA stacks

Sara L. Ellison, Manasvee Saraf, Leonardo Ferreira et al. (+4 more)

(Abridged) In this work, we investigate the role of atomic hydrogen (HI) gas in the galaxy merger lifecycle. In order to both identify galaxies in mergers, as well as to predict their time since coalescence, we present an extension of the MUlti Model Merger Identifier (MUMMI) machine vision pipeline applied to Dark Energy Camera Legacy Survey (DECaLS) imaging. The new MUMMI-DECaLS catalog contains 19,951 post-mergers, of which 14,638 have robust time post-merger (T_PM) predictions. The MUMMI-DECaLS post-merger galaxy catalog is cross-matched with the Arecibo Legacy Fast ALFA (ALFALFA) survey. For the 752 post-mergers thus identified, as well as a matched control sample, we produce median spectral stacks of 21~cm emission, finding that the post-mergers are HI deficient by 0.11 dex compared with non-interacting galaxies. When divided into T_PM bins we find that the HI deficit (or excess) is strongly dependent on both the time since coalescence and whether the galaxies are star-forming or quenched. Star-forming post-mergers in particular show a strong HI evolution with T_PM, exhibiting a 0.1 dex MHI excess immediately after coalescence, a 0.3 dex MHI deficit at 0.16 < T_PM < 0.96 Gyr and normal gas masses by ~ 1.5 Gyr after coalescence. On the other hand, despite being matched in star formation rate, stellar mass and redshift, quenched post-mergers are HI deficient at both short and long post-coalescence times. Nonetheless, a significant mass of HI (>10^9 M_sun) remains even in these late-time quenched post-mergers, representing a resource which could potentially re-fuel star formation in the future. Our results demonstrate the complexity of quantifying the HI behaviour in mergers, which depends not only on timing, but also star-forming status, which can complicate comparisons between different studies and samples.
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All authors Sara L. Ellison, Manasvee Saraf, Leonardo Ferreira, Amelie Saintonge, Dirk Scholte, Jing Wang, Qifeng Huang

High Energy Astrophysical Phenomena

Magnetar magnetothermal evolution with Landau-quantized electrons: enhanced Joule heating due to free electron diamagnetism and the magnetar heating problem

Peter B. Rau

Magnetars are systematically more luminous than other neutron stars. Previous studies suggest that supporting such high luminosities requires a heat source beyond standard Ohmic dissipation– the “magnetar heating problem”. We previously demonstrated using periodic box simulations that de Haas–van Alphen (dHvA) oscillations of the Landau quantization-induced magnetization in a neutron star could repeatedly generate large-gradient field components that undergo rapid Ohmic dissipation. Using the QMFM finite volume code developed for this purpose, we perform axisymmetric 2.5D electron magnetohydrodynamics plus thermal evolution simulations of a realistic neutron star crust, including all Landau quantization effects, to quantify this enhancement to field dissipation and heating of the star. We show that Landau quantization effects generate strong, small-scale magnetic field structures whose dissipation can heat the field-confined equatorial hot spot beyond its temperature in the absence of Landau quantization. Enhanced heating is greatest for weaker initial fields $B\sim10^{14}$ G, for which magnetic energy is dissipated 30% faster: in this case, the crust cools sufficiently for the dHvA oscillations to reach large amplitudes. For the stronger fields $\gtrsim B\sim5\times10^{14}$ G required to power the most luminous magnetars, the enhancement is modest, as dissipation of these fields heats the crust sufficiently to thermally suppress dHvA oscillations. In cases where heating is significantly enhanced, most of the heat goes into increasing the neutrino luminosity, and surface photon luminosity is only slightly increased. For the simple crust-confined fields that we simulated, Landau quantization-enhanced Joule heating is thus insufficient to explain the magnetar heating problem.
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Mesoscale and Nanoscale Physics

Modified Low-Temperature Scanning Tunneling Microscope for Ultrafast Pump-Probe Spectroscopy

Vibhuti N. Rai, Junyoung Sim, Nils Bogdanoff et al. (+7 more)

Combining scanning tunneling microscopy (STM) with terahertz pulses (THz-STM) enables ultrafast dynamics of phonons, spins, and charge carriers to be probed with atomic-scale spatial and sub-picosecond temporal resolution. However, coupling THz radiation into a low-temperature STM junction presents some technical challenges as it requires optical access for laser illumination while maintaining junction stability. Instead of designing a completely new STM head with customized optical access and optics within the ultra-high vacuum chamber, we modified a Besocke "Beetle" style STM with minimal changes of the cryogenic radiation shields. Despite the given geometrical conditions, we achieved efficient coupling of THz and optical pulses to the STM junction while maintaining temperatures below 6 K. We designed the optical setup on a separate laser table, starting with femtosecond laser pulses that are used to generate THz pulses in a LiNbO$_3$ crystal. We show the obtained THz pulse shapes and determine the effective time resolution using cross-correlation measurements. We further demonstrate the stable performance of the modified STM by measuring THz-induced tunneling currents from monolayer molybdenum disulfide (MoS$_2$) grown on Au(111). The resulting current maps resolve atomic-scale contrast revealing a point defect. The measurements confirm efficient THz coupling and stable low-temperature STM operation with atomic resolution.
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All authors Vibhuti N. Rai, Junyoung Sim, Nils Bogdanoff, Sergey Trishin, Florian Faaber, Paul Wiechers, Caroline Firschke, Tobias Kampfrath, Christian Lotze, Katharina J. Franke

Optics

Fisher-information training of optical sensing front ends from natural fluctuations

Abhinav Sinha and Kai Wang

Fisher-information-based optimization of programmable optical front ends in situ generally requires a response model or parameter-labeled measurements. We show that natural parameter fluctuations can instead provide the training signal. We construct proxies for the Fisher information (FI) of one parameter and the prior-weighted FI spectrum of multiple parameters from measured covariances after subtracting conditional detection noise, assuming locally affine responses. We use simulated photon counts from two incoherent point sources to train a mode sorter that approaches the quantum limit for separation and the Nagaoka–Hayashi single-copy bound for joint centroid–separation estimation. We demonstrate count-only updates that require no instrument response model and achieve performance comparable to model-based gradients. Our results provide a route to adaptive optical measurements without controlled parameter scans.
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High Energy Astrophysical Phenomena

Luminosity Signatures of Dark Sector Particles from Black Hole Evaporation in Neutron Stars

Ioannis Dalianis and Anastasios Irakleous

Microscopic black holes may form at the centers of neutron stars through the accumulation and collapse of dark matter. While Standard Model particles produced by Hawking evaporation are efficiently absorbed by the dense stellar medium, sufficiently weakly interacting and long-lived particles can escape and subsequently decay into high-energy neutrinos, photons, or charged particles, providing an indirect probe of Hawking radiation. We examine the joint energy–angular distribution of these secondary particles, incorporating mediator propagation, energy-dependent decay, and relativistic decay kinematics. For relativistic mediators, the normalized energy-integrated angular profile becomes approximately independent of the black hole temperature, with its characteristic extent controlled primarily by the combination $c\tau_S/D$ of the mediator lifetime and source distance, as the boost enhancement of the decay length is compensated by relativistic beaming. We demonstrate the viability of this mechanism and illustrate its phenomenology with gravitationally coupled scalars, dark photons, dark-$Z$ bosons, and heavy neutral leptons. Comparing with monochromatic mediator production from dark matter annihilation, we find that the energy-integrated angular profiles can be nearly degenerate, while the energy spectra and energy-resolved angular distributions remain distinct. These complementary spectral and angular signatures provide targets for high-energy neutrino and gamma-ray searches.
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General Relativity and Quantum Cosmology

Boson Star Factory: Past, Present, and Future

Romain Gervalle, Jorge Filipe Mónico Delgado, Etevaldo dos Santos Costa Filho et al. (+4 more)

Boson stars are self-gravitating solitons of the Einstein-Klein-Gordon equations for a massive complex scalar field, and arguably the simplest horizonless compact objects arising in General Relativity. Beyond spherical symmetry, their construction requires solving a system of nonlinear elliptic partial differential equations, a difficult task per se and that each group has traditionally addressed with its own numerical implementation. A systematic comparison of different methods applied to the same physical model has so far been lacking. In this work, we carry out such a comparison for the two simplest non-spherical configurations: rotating boson stars and static dipolar boson stars. We employ three independent codes, based respectively on finite differences (FIDISOL/CADSOL), finite elements (FreeFem), and spectral methods (Kadath), and assess their accuracy through different diagnostics. The three solvers agree on the global observables to typically eight significant digits. We further compare the runtime of each code on identical hardware and provide precise benchmark values of the relevant physical quantities, intended to serve as reference data for future numerical studies of boson stars. As a further proof of concept, we also present the use of physics-informed neural networks to construct a rotating Q-ball solution.
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All authors Romain Gervalle, Jorge Filipe Mónico Delgado, Etevaldo dos Santos Costa Filho, Carlos Herdeiro, Víctor Jaramillo, Raimon Luna, Eugen Radu

High Energy Physics (Theory)

Gauss–Bonnet running and the de Sitter saddle of quadratic gravity inflation

Ruolin Liu and Niayesh Afshordi

Inflation driven purely by the quantum running of the curvature-squared couplings of quadratic gravity was shown to accommodate the high scalar tilt favored by recent cosmic microwave background observations, starting from a Euclidean four-sphere at a maximum of the running $R^2$ coupling. That maximum exists only in one renormalization scheme, and is not stationary once the Euler trace anomaly is included. We show that the standard one-loop running, with the usually neglected Gauss–Bonnet coefficient retained, recovers the missing de Sitter state: the Euler running balances the scale dependence of the $R^2$ term at a unique coupling ratio, giving a de Sitter solution that is stationary for the gravitational constraint and for the compact Euclidean action alike, and whose scalaron potential is an extremely flat hilltop ($m^2/H^2\simeq-5\times10^{-10}$) joined to an inverse-linear inflationary plateau. The last $N_*\simeq50$–$60$ $e$-folds are scheme independent, with scalar tilt $n_s\simeq1-4/(3N_*)$, while the tensor-to-scalar ratio, $r$, is set by the number of matter fields that enhance the running. The current tensor bound excludes pure gravity and sets a minimum matter content, some $4\times10^6$ conformally coupled scalars or $3\times10^5$ vectors—$2.6$ times fewer than the momentum-induced scheme requires—while one-loop control to the end of inflation sets a maximum about ten times higher. Across that window the model predicts $r\gtrsim0.008$ with $0.973\lesssim n_s\lesssim0.978$, within reach of upcoming CMB polarization surveys.
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High Energy Physics (Phenomenology)

Two-loop amplitude for the associated production of a top-anti-top pair and a $W$ boson at hadron colliders

Mattia Pozzoli

In this contribution I present a calculation of the inclusive cross-section for the associated production of a top-anti-top pair and a W boson at next-to-next-to-leading order in QCD, based on the first exact computation of the two-loop QCD amplitude at leading colour. I discuss a strategy to express the amplitude in terms of a set of special functions with rational coefficients, overcoming the obstacle posed by the presence of elliptic functions. The special functions are evaluated through the method of differential equations, while the rational coefficients are computed using finite field techniques. For the computation of the inclusive cross-section, the double-virtual correction is evaluated by interpolating a five-dimensional grid.
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Soft Condensed Matter

Nucleosome simulations suggest mechanisms of electrostatically-driven mesoscale chromatin evolution

Siddhartha G. Jena

Nucleosomes are structures made up of proteins called histones that bind and compact DNA, driving the mesoscale organization of the chromatin polymer. Although histone proteins have diversified over evolutionary time, their contributions to the corresponding diversification of chromatin structure are poorly understood. Here, we mine protein databases for histones and create in silico nucleosomes for 3241 organisms spanning $>$1.5B years of evolution. Using a combination of electrostatic calculations and coarse-grained molecular dynamics simulations, we reveal extensive biophysical diversification of the nucleosome unit. Finally, we perform coarse-grained oligonucleosomal simulations on a subset of evolutionarily and biophysically divergent nucleosomes, demonstrating dramatic differences in bulk phase behavior of chromatin. Taken together, our results suggest a paradigm in which histones may have evolved to facilitate particular types of mesoscale chromatin behavior.
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