Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Monday 15 June

Earth and Planetary Astrophysics

Transit Timing Variations in TESS: A Catalog from the First Five Years

Emma Nabbie, Chelsea X. Huang, Robert A. Wittenmyer et al. (+1 more)

We present the first catalog of transit timing variations (TTVs) in TESS systems with multiple TESS Objects of Interest (TOIs) using data from Sector 1 to Sector 69, spanning the first five years of mission operations. With an initial sample of 175 multi-TOI systems, we find significant TTVs in 20 systems, 13 of which had not been previously detected. Our results are generally consistent with the findings of previous Kepler TTV catalogs, with compact systems more likely to have detectable TTVs. However, the TTV systems in TESS exhibit a pile-up at the 2:1 orbital period resonance, in contrast to the pile-up near the 3:2 resonance from previous Kepler catalogs. This provides a tentative indicator that there may be different disk migration recipes that Kepler systems favor versus TESS systems. This catalog is a vital first step in determining which orbital resonances migrating planets tend to occupy at the end of formation, and aims to provide a list of high-impact targets for future in-depth follow up.
Read the full abstract

All authors Emma Nabbie, Chelsea X. Huang, Robert A. Wittenmyer, George Zhou

General Relativity and Quantum Cosmology

CASPER: Interpretable ResNet based Classifier with FastShap Explainer for Gravitational Wave Detection

R. Rai, R. Verma and Somya

Traditional matched filtering has been the standard for Gravitational waves (GW) detection ever since LIGO was established, even though it requires pre-computed waveform templates and provides no accounts of information about which signal drove the decision of classification. Deep-learning alternatives showed competitive sensitivity, but system biasesincluding class overlap, imbalanced class weighting, limited sample variation, and traintest mismatchcontinue to cause problems with generalisation in real detector noise. We introduce CASPER-Classification with Attribution via ShaPlEy in Residual neural networks, an end-to-end pipeline combining residual convolutional neural network (CNN) classifier with a FastSHAP explainer. 260 distinct events from the Gravitational Wave open Science Centre were fetched across SNR range of 7-42 from both H1 and L1 detectors with no synthetic augmentation. The classifier achieves AUC (Area Under Curve) of 91% across the model with a low false alarm rate. Focal Loss and Platt Calibration were used to improve decision boundary and generalisation. FastSHAP attribution maps recover the complete chirp morphology and provides detailed maps for a visual interpretation of the decision. The complete pipeline contains fewer parameters than standard deep learning models and requires no hardware except a standard CPU making our model an effective lightweight pipeline for Gravitational Wave Detection under real life conditions.
Read the full abstract

Astrophysics of Galaxies

Testing masking effectiveness using multi-line image cubes based on COSMOS2020 for [CII] line intensity mapping at $z_{[CII]} > 3.5$

J. Clarke, C. Karoumpis, A. Dev et al. (+5 more)

We created line intensity mapping intensity cubes for CO and [CII] emission lines using the COSMOS2020 galaxy catalogue, forming predictions based on empirical data, for observations from Prime-Cam mounted on the Fred Young Submm Telescope. We also included simulated noise including white and correlated components, and tested masking techniques to recover [CII] signal at $3.5<z<8.2$. We applied line luminosity models to the COSMOS2020 galaxy catalogue, spanning 1.44deg$^2$, to estimate the [CII] and CO J=1-0 emission, with other CO transitions derived using Spectral Line Energy Distribution templates. From these we made cubes for four 40 GHz bands in the EoR-Spec frequency range (205-420GHz), as well as a potential future upgrade to EoR-Spec including bands at 150 and 90GHz. Given the incompleteness of the empirical catalogue, these predictions are conservative lower limits, which we subsequently extrapolated from. We applied masks to recover the [CII] power spectra, using bright galaxies of COSMOS2020 as a foreground catalogue to target CO at low z (targeted masking), and matching bright voxels across frequency bands to eliminate those associated with CO emission (blind masking). Our CO intensity cube predictions are consistent with ALMA, VLA and NOEMA observations, indicating that this method gives realistic CO estimates for E-COSMOS. In ideal conditions, masking can recover [CII] above 300GHz, with targeted masking requiring a complete foreground catalogue of bright CO sources to prevent them from contributing to contaminant emission, and blind masking needing additional lower frequency ranges to be effective. However, noise will hinder [CII] recovery above 300 GHz until near the end of the currently planned 2000 hour observing period, as $S/N<5$ without extra observing time. Whilst CO can be recovered below 300GHz, [CII] will be unavailable without cross correlation techniques.
Read the full abstract

All authors J. Clarke, C. Karoumpis, A. Dev, D. Riechers, T. Oak, Y. Okada, K. Narita, F. Bertoldi

Solar and Stellar Astrophysics

Wildly Oscillating Stars – Unexplained dense ridge-like frequency agglomerations in A and F type pulsators

V. Antoci, J. Labadie-Bartz, M. Swiech et al. (+14 more)

We investigate the origin of the dense, ridge-like frequency clusters observed in a subset of A and F type pulsating stars, which we refer to as `wildly oscillating' stars (WOS). These agglomerated frequency regions occupy a confined part of the frequency spectrum, typically below the fundamental radial mode, and are not explained by pulsation theory. We analyse Kepler and TESS data, construct echelle diagrams, and perform searches for combination frequencies. We determine the fundamental radial mode in order to place the agglomerated regions in a seismic context. Rotational modulation is examined through phase-folded light curves and amplitude-phase analysis, and binarity and geometric modulation scenarios are tested. The WOS phenomenon is confined to a narrow region near the overlap of the delta Sct and gamma Dor instability strips. The observed ridge morphology and mode density cannot be reproduced by simple asymptotic g-mode behaviour, low-order p modes, binarity, or typical rotational splitting. In at least two stars, a significant fraction of peaks in the agglomerated region can be explained as nonlinear combination frequencies involving high-order g modes. However, these combinations require parent modes located within the agglomerated frequency band itself, indicating that intrinsic pulsation modes must be present there. Non-adiabatic stability calculations reproduce the classical instability domains but do not predict unstable modes with the observed density or organised ridge structure in the agglomerated region. The WOS appear to represent a pulsational regime not captured by current models of mode excitation or rotational modulation. The agglomerated frequency phenomenon requires a mechanism that selects or excites a confined intermediate-frequency band and produces organised ridge structures within a narrow region of stellar parameter space (abridged for arXiv).
Read the full abstract

All authors V. Antoci, J. Labadie-Bartz, M. Swiech, O. Deurfeldt-Pedros, S.J. Murphy, D.W. Kurtz, T.R. Bedding, G. Handler, J. Fuller, R.-M. Ouazzani, H. Kjeldsen, L. Fellay, M. Gade Pedersen, E. Niemczura, D.M. Bowman, M. Deal, P. Mani

Mesoscale and Nanoscale Physics

Kohn–Luttinger Superconductivity in Flat Chern Bands

Nianlong Zou, Cheng Xu, Yafis Barlas et al. (+1 more)

Recent observations of superconductivity near correlated topological phases in flat bands suggest a facile link between flat-band geometry and electron pairing. In this work, we reveal a geometry-driven Kohn–Luttinger mechanism in which Landau-level-like form factors align the attractive lobe of the RPA-screened Coulomb interaction with the form-factor peak, generating an anomalously strong attractive channel near local band extrema. Using the Skyrmion lattice model as a minimal realization, we show that for spin-unpolarized pairing the form-factor magnitude enforces an emergent momentum-space translational symmetry and selects an extended-$s$ instability concentrated at small Fermi pockets, while for spin-polarized pairing the form-factor phase drives chiral $p$- and $f$-wave order without invoking spin fluctuations. The band-extrema enhancement persists in higher Landau-level analogs and survives finite-temperature screening and Berezinskii–Kosterlitz–Thouless phase fluctuations. Our work establishes quantum geometry as a key organizing principle for unconventional pairing in flat Chern bands.
Read the full abstract

All authors Nianlong Zou, Cheng Xu, Yafis Barlas, Yang Zhang

High Energy Physics (Phenomenology)

Scaling of the Surface Free Energy as a Probe of the QCD Critical Region

Joseph I. Kapusta, Mayank Singh and Shensong Wan

The QCD phase diagram is expected to have a critical point that separates the crossover and first-order transition lines. A realistic model that incorporates phase boundary effects is essential for heavy ion simulations to isolate the experimental signatures of a critical point. We discuss how to construct such an equation of state, and study its critical behavior. The effect of the coefficient of surface energy on the size of the critical region is investigated. We found that with this construction and with the chosen background equation of state, the temperature must be within one percent of its critical value to observe the critical exponents. This makes it doubtful that the critical exponents can be measured in heavy ion collisions, though it may still be feasible to observe signatures of a first-order phase transition. The method presented here is general and can be utilized with any given equation of state to test the viability of observing critical exponents in experiments.
Read the full abstract

Plasma Physics

Optical Emission Spectroscopy Measurements of keV Apparent Ion Temperatures in Avalanche Energy's Centrifugal Mirror Machine

M. Affolter, E. C. Hayes, A. Helson et al. (+4 more)

Newly formed ions in $E \times B$ devices are rapidly accelerated by strong radial electric fields and execute large cycloidal orbits in the presence of an axial magnetic field. At locations where these orbits intersect, ions originating from different birth radii arrive with substantially different velocities, producing a non-Maxwellian velocity distribution with a large velocity variance. Through Coulomb collisions and collective interactions, this distribution relaxes toward a drifting Maxwellian in the rotating frame. Here, we present the first optical emission spectroscopy (OES) measurements of the line-of-sight-convolved ion-velocity distribution, from which an apparent ion temperature is determined, in Avalanche Energy's centrifugal mirror machine. High-resolution $H_\alpha$ spectra obtained along five chordal lines-of-sight spanning the plasma radius are analyzed using two complementary models representing limiting cases of the ion dynamics: a collisionless cycloidal model based on the ion-velocity distribution arising from deterministic single-particle orbits, and a rotating Gaussian model based on collisions and collective processes that fully randomize the cycloidal motion into a drifting Maxwellian in the rotating frame. Combined, these approaches bracket the possible degree of velocity-space relaxation and provide a stringent test of the inferred ion energies. Both models reproduce the measured spectra relatively well and yield density-weighted apparent ion temperatures of $1.40\pm0.43$ keV for the rotating Gaussian model and $1.55\pm0.24$ keV for the cycloidal model. These results provide direct spectroscopic evidence that strong $E \times B$ rotation in a device only a few centimeters in size can generate ion populations with keV energy spreads.
Read the full abstract

All authors M. Affolter, E. C. Hayes, A. Helson, E. McKee, A. Gargone, S. Hepner, R. Langtry

Superconductivity

How twist angle inhomogeneity masks the BKT transition and the order parameter symmetry

Ilaria Maccari, Louk Rademaker and Giulia Venditti

Two-dimensional superconductors, including twisted multilayer graphene, should exhibit a BKT transition, and the $T$-dependence of the superfluid stiffness should distinguish between nodal or gapped order parameter symmetries. However, this picture dramatically changes when spatially correlated disorder is taken into account. Such correlations naturally arise in moiré systems due to twist angle inhomogeneities, which we model using elasticity theory. Using a random impedance network based on realistic disorder in the local $T_c$, we show that the finite-frequency conductance reveals a smeared percolative transition instead of a BKT transition. At low temperatures, the disorder can effectively obscure the distinction between nodal and fully gapped superconducting order parameters. We propose that the real part of the conductivity can be used as a key diagnostic observable to probe the relevance of correlated disorder.
Read the full abstract

Astrophysics of Galaxies

Exploring the Relationship Between Bars, Star Formation Activity, and Host Galaxy Properties from $\mathbf{z \sim 0}$ to $\mathbf{z \sim 2}$

Eden Wise, Shardha Jogee, Yuchen Guo et al. (+20 more)

We present the most comprehensive study to date of the relationship between bars, star formation, and galaxy properties from $z \sim$ 0 to $z \sim$ 2. We use a mass-complete sample of 1,171 galaxies from the JWST CEERS survey with $M_\star > 10^{10} M_\odot$ and repeat the analysis using COSMOS-Web data. Our results are: 1) At high redshift ($z \sim$ $1-2$) barred galaxies tend to have high sSFRs and low Sérsic indices ($n \leq 2$), while at low redshifts barred galaxies emerge with both low sSFR and higher $n$, suggestive of quiescent galaxies with bulges. 2) The fractional contribution of barred quiescent galaxies to the bar fraction rises steeply from $z \sim$ 2 to $z \sim$ 0, while that of barred actively star-forming galaxies falls. 3) The fraction of quiescent galaxies that are barred rises steeply over the last 10 Gyr. 4) Our empirical results show good agreement with the TNG50-1 simulations for bars with $a_{\mathrm{bar}}$ $>$ 1.5 kpc. Our results allow for the possibility that bar-driven secular evolution may lead to quiescence and/or that bars are more likely to persist and grow in gas-poor, quiescent galaxies. The steep rise in the quiescent bar fraction over 10 Gyr may represent an evolutionary sequence whereby gas-rich disks at high redshift first develop short, dynamically young bars and over time, repeated bar-driven gas inflows lead to central starbursts and declining gas fractions that strengthen the bar as the galaxy transitions toward quiescence.
Read the full abstract

All authors Eden Wise, Shardha Jogee, Yuchen Guo, Steven L. Finkelstein, Micaela B. Bagley, Marc Huertas-Company, Kartheik G. Iyer, Elizabeth J. McGrath, Natalia C. Villanueva, Tommaso Zana, Anton M. Koekemoer, Eric F. Bell, Jean-Baptiste Billand, Yingjie Cheng, Alexander de la Vega, Elena D'Onghia, Tobias Géron, Mauro Giavalisco, Benne W. Holwerda, Ray A. Lucas, Fabio Pacucci, Maxime Tarrasse, L. Y. Aaron Yung

Materials Science

Machine learning insights into band gap properties in halide-based perovskites

Chadawan Khamdang and Mengen Wang

Halide perovskites show great promise for applications in optoelectronic devices. The lead-free perovskites are attracting increasing interest due to their low toxicity and motivate the exploration of alternative compositions and structures, including A$_2$BX$_6$, A$_2$BB$^\prime$X$_6$, A$_3$B$_2$X$_9$, and A$_4$BX$_6$. Accurate predictions of a wide range of band gap energies are important for designing new materials. It is also desired to generate a direct relationship between the structural and elemental descriptors and the band gap energies. In this work, we develop machine learning models to predict band gap energies across various types of halide perovskites based on atomic and structural properties. Algorithms including ensemble tree-based methods, random forest regression (RFR), gradient boosted regression trees (GBRT), and extreme gradient boosting (XGB) showed strong predictive accuracy. We also analyzed feature importance to identify key descriptors, including B-site and X-site elemental properties, as well as the number of A- and B-site atoms, as primary factors influencing band gap energies. These results improve our understanding of the ML models and provide guidance for designing new halide perovskite materials.
Read the full abstract

Nuclear Experiment

Measurement of dijet transverse momentum imbalance and azimuthal acoplanarity in $p$+$p$ collisions at $\sqrt{s} = 200$ GeV with the sPHENIX detector

sPHENIX Collaboration: M. I. Abdulhamid, U. Acharya, E. R. Adams et al. (+326 more)

This Letter reports on measurements of dijet transverse momentum ($p_\mathrm{T}$) imbalance and azimuthal acoplanarity in proton-proton collisions at $\sqrt{s} = 200$~GeV, using data recorded by the sPHENIX detector at the Relativistic Heavy Ion Collider corresponding to an integrated luminosity of $41$~pb$^{-1}$. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameters $R = 0.3$ to $0.8$ from electromagnetic and hadronic calorimeter energy deposits. The jet $p_\mathrm{T}$ resolution is determined directly in data using two independent methods. The dijet $p_\mathrm{T}$ imbalance is characterized by the ratio $x_\mathrm{J} = p_\mathrm{T,2}/p_\mathrm{T,1}$ where $p_\mathrm{T,1(2)}$ is the highest (second-highest) jet $p_\mathrm{T}$ in the event. The dijet azimuthal acoplanarity $\Delta\phi = |\phi_1 - \phi_2|$ is also reported. Results are reported for different $p_\mathrm{T,1}$ selections and jet radius parameters, normalized per dijet pair, and compared to the results of Pythia and Herwig Monte Carlo event generators. These measurements provide a stringent quantitative test of the modeling of QCD parton shower and hadronization dynamics, place important constraints on event-generator descriptions at RHIC energies, and establish a comprehensive proton-proton baseline for forthcoming measurements of jet modification in heavy ion collisions.
Read the full abstract

All authors sPHENIX Collaboration: M. I. Abdulhamid, U. Acharya, E. R. Adams, G. Adawi, I. Ahmed, C. A. Aidala, Y. Akiba, M. Alfred, S. Ali, A. Alsayegh, S. Altaf, H. Amedi, D. M. Anderson, V. V. Andrieux, A. Angerami, N. Applegate, M. U. Ashraf, H. Aso, S. Aune, B. Azmoun, V. R. Bailey, D. Baranyai, S. Bathe, A. Bazilevsky, S. Bela, R. Belmont, J. Bennett, J. C. Bernauer, J. Bertaux, R. Bi, A. Bonenfant, S. Boose, C. Borchers, H. Bossi, R. Botsford, R. Boucher, A. Brahma, J. W. Bryan, D. Cacace, I. Cali, M. Chamizo-Llatas, S. B. Chauhan, A. Chen, D. Chen, J. Chen, K. Chen, K. Y. Chen, K. Y. Cheng, C.-Y. Chi, M. Chiu, J. Clement, E. W. Cline, M. Connors, E. Cook, R. Corliss, Y. Corrales Morales, E. Croft, N. d'Hose, A. Dabas, D. Dacosta, M. Daradkeh, S. J. Das, A. P. Dash, G. David, C. T. Dean, K. Dehmelt, X. Dong, A. Drees, J. Driebeek, J. M. Durham, A. Enokizono, H. Enyo, J. Escobar Cepero, R. Esha, B. Fadem, R. Feder, K. Finnelli, D. Firak, D. S. Fitzgerald, L. V. Flores-Sanchez, A. Francisco, J. Frantz, A. Frawley, K. Fujiki, M. Fujiwara, B. Garcia, P. Garg, G. Garmire, E. Gentry, Y. Go, C. Goblin, I. Goel, W. Goodman, Y. Goto, A. Grabas, O. Grachov, J. Granato, N. Grau, S. V. Greene, S. K. Grossberndt, R. Guidolini-Cecato, T. Hachiya, J. S. Haggerty, R. Hamilton, J. Hammond, D. A. Hangal, T. Harada, S. Hasegawa, M. Hata, W. He, X. He, T. Hemmick, A. Hodges, M. E. Hoffmann, A. Holt, B. Hong, M. Housenga, S. Howell, Y. Hu, H. Z. Huang, J. Huang, T. C. Huang, D. A. Huffman, C. Hughes, J. Hwang, T. Ichino, M. Ikemoto, D. Imagawa, H. Imai, Y. Ishigaki, D. Jah, J. James, H.-R. Jheng, Y. Ji, Z. Ji, H. Jiang, M. Kano, L. Kasper, T. Kato, Y. Kawashima, A. M. Khan, M. S. Khan, T. Kikuchi, J. Kim, B. Kimelman, H. T. Klest, A. G. Knospe, M. B. Knuesel, H. S. Ko, J. Kuczewski, N. Kumar, R. Kunnawalkam Elayavalli, C. M. Kuo, J. Kvapil, Y. Kwon, J. Lajoie, J. D. Lang, A. Lebedev, S. Lee, L. Legnosky, S. Li, X. Li, T. Lian, S. Liechty, S. Lim, D. Lis, M. X. Liu, W. J. Llope, D. A. Loomis, R.-S. Lu, C. Ma, L. Ma, W. Ma, V. Mahaut, T. Majoros, I. Mandjavidze, E. Mannel, C. Markert, T. R. Marshall, C. Martin, H. Masuda, G. Mattson, M. Mazeikis, C. McGinn, E. McLaughlin, J. Mead, Y. Mei, T. Mengel, A. S. Menon, M. Meskowitz, J. Mills, A. Milov, C. Mironov, I. Mitrankov, M. Mitrankova, G. Mitsuka, N. Morimoto, M. Morita, D. Morrison, L. W. Mwibanda, C.-J. Naïm, J. L. Nagle, I. Nakagawa, Y. Nakamura, G. Nakano, Y. Namimoto, A. Narde, C. E. Nattrass, D. Neff, S. Nelson, D. Nemoto, P. A. Nieto-Marín, R. Nouicer, G. Nukazuka, E. O'Brien, G. Odyniec, S. Oh, V. A. Okorokov, A. C. Oliveira da Silva, I. Omae, J. D. Osborn, G. J. Ottino, Y. C. Ou, J. Ouellette, D. Padrazo Jr., T. Pani, J. Park, A. Patton, H. Pereira Da Costa, D. V. Perepelitsa, M. Peters, S. Ping, C. Pinkenburg, R. Pisani, C. Platte, C. Pontieri, T. Protzman, M. L. Purschke, J. Putschke, R. J. Reed, L. Reeves, S. Regmi, B. Rehman, E. Renner, D. Richford, C. Riedl, T. Rinn, C. Roland, G. Roland, A. Romero Hernandez, M. Rosati, D. Roy, A. Saed, T. Sakaguchi, H. Sako, S. Salur, J. Sandhu, M. Sarsour, S. Sato, B. Sayki, C. Scarlett, B. Schaefer, J. Schambach, M. Schernau, R. Seidl, B. D. Seidlitz, Y. Sekiguchi, M. Shahid, D. M. Shangase, Z. Shi, M. Shibata, C. W. Shih, K. Shiina, M. Shimomura, R. Shishikura, E. Shulga, A. Sickles, D. Silvermyr, J. Singh, R. A. Soltz, W. Sondheim, I. Sourikova, P. Steinberg, D. Stewart, M. Stojanovic, S. Stoll, Y. Sugiyama, O. Suranyi, A. Suzuki, R. Takahama, W.-C. Tang, S. Tarafdar, E. Thorsland, T. Todoroki, L. S. Tsai, H. Tsujibata, M. Tsuruta, J. Tutterow, E. Tuttle, B. Ujvari, E. N. Umaka, M. Vandenbroucke, J. Vasquez, J. Velkovska, V. Verkest, A. Vijayakumar, X. Wang, Y. Wang, Z. Wang, I. S. Ward, M. Watanabe, J. Webb, A. Wehe, A. Wils, V. Wolfe, C. Woody, W. Xie, Y. Yamaguchi, Z. Ye, K. Yip, Z. You, G. Young, C.-J. Yu, X. Yu, X. Yu, W. A. Zajc, V. Zakharov, J. Zhang, C. Zimmerli

Statistical Mechanics

Why dimensional analysis works: general classification of self-similarity based on scale-invariance

Hirokazu Maruoka

In this work, we formulate self-similarity from the perspective of scale invariance, where a self-similar form is understood as the transformation of a function into a form invariant under scale transformations. By applying this formulation to physical parameters, which consist of numerical values and units, it is demonstrated that dimensional analysis works for physical problems because scale invariance is partially shared between units and physical parameters. This naturally leads to the distinction between similarity of the first kind and similarity of the second kind according to whether the scale functions induced by units and those associated with physical parameters are equivalent or not. Self-similar solutions of the second kind can be further classified according to whether the power exponents of the similarity parameters include functions of dimensionless numbers. This leads to the conclusion that there are three kinds of self-similar solutions. The present work provides a unified framework for understanding dimensional analysis and a universal classification of self-similarity in physical problems.
Read the full abstract

General Relativity and Quantum Cosmology

Exciting the Vacuum: Non-Thermal Particle Bursts and Multi-Messenger Signals from Binary Black Holes

Sohrab Rahvar

We investigate particle production in the dynamical curved spacetime of a binary black hole system. Particle production is a well-known feature of quantum field theory in curved spacetime, underlying the Hawking and Unruh effects. Here we extend it to the time-varying gravitational perturbation sourced by a binary black hole. Treating a massless scalar field coupled to the binary metric, we compute the particle flux and radiated energy to leading order in the metric perturbation $h_{\mu\nu}$, using both the Bogoliubov transformation method and the S-matrix formalism. The perturbation is modeled with the standard quadrupole formalism, retaining the time-domain quadrupolar ($\ell=2$) contribution that dominates gravitational-wave emission. Our calculation is valid in the weak-field, large-separation inspiral regime and is not expected to capture the strong-field, nonlinear merger phase. In this regime we find a characteristic non-thermal, power-law emission with $dE/dt \propto M^{10/3}\omega^{16/3}$, in contrast to a thermal Hawking spectrum. Extending the analysis through merger that uses the numerically-relativistic metric is left to future work.
Read the full abstract

Superconductivity

Hybrid Ferromagnet-SNSPDs: Single photon induced order-to-disorder transition in ferromagnets coupled to thin film superconductors

Leif Bauer, Daien He, Sathwik Bharadwaj et al. (+1 more)

The development of midwave and longwave infrared single photon detectors is crucial for their emerging applications in spectroscopy, remote sensing, exoplanet detection, and free space quantum communications. However, existing sensors need to be operated at extremely low temperatures (0.08-0.9K) to reduce dark noise and hence require the use of advanced cryogenics such as dilution refrigerators or $^3$He cryogens, significantly limiting applications. Here we propose a vortex-engineering approach based on a hybrid phase transition in a ferromagnet/superconductor bilayer to increase the operating temperature of infrared single photon detectors up to 3.75K. We show that the introduction of a ferromagnetic layer produces a local magnetic field which impedes vortex crossing in the superconductor, reducing dark noise. When a single photon is incident, the photon-induced hotspot causes an order-to-disorder transition in the ferromagnet, leading to a vortex-induced phase transition in the superconducting layer. By engineering the ferromagnet's Curie temperature to be close to the device's operating temperature, single photon sensitivity can be achieved at increased operating temperatures. We predict at midwave/longwave infrared wavelengths (3-14$\mu$m) the operating temperature can be raised to 3.25-3.75K, enabling significantly simpler cooling systems.
Read the full abstract

All authors Leif Bauer, Daien He, Sathwik Bharadwaj, Zubin Jacob

Cosmology and Nongalactic Astrophysics

Tracing Ultra Light Axions in Post-reionization, Lyman-$\alpha$ and CMB Missions

Debarun Paul, Sourav Pal, Amit Dutta Banik et al. (+1 more)

Ultra-light axions (ULAs) are dark matter candidates proposed to resolve the small scale anomalies of the standard cosmological model. Due to their inherent quantum pressure, ULAs result in a distinct, scale-dependent suppression on the matter power spectrum, which can leave imprints on the upcoming observations. We explore such possibilities by forecasting on the post-reionization large scale structure (LSS) surveys and next-generation cosmic microwave background (CMB) missions. By utilizing the cross-correlation between 21-cm intensity mapping (SKA1-MID and PUMA) and the Lyman-$\alpha$ forest (DESI-like), we explore possible signatures of ULAs in post-reionization surveys while mitigating instrument-specific systematics. The Fisher matrix analysis projects uncertainties on the fractional ULA abundance across a wide ULA mass range of $10^{-30}\text{ eV} \le m_a \le 10^{-20}\text{ eV}$, revealing an optimal detection sensitivity at intermediate masses around $m_a \sim 10^{-25}\text{ eV}$. Furthermore, while next-generation CMB mission alone can yield small projected errors on the ULA fraction compared to future LSS missions, a joint analysis of the DESI-like and PUMA cross-spectrum alongside CMB-S4-like missions estimates an error on the ULA fraction to be $\mathcal{O}(10^{-4})$ for $m_a\lesssim 10^{-28}$ eV, highlighting a significant improvement over standalone LSS and CMB missions.
Read the full abstract

All authors Debarun Paul, Sourav Pal, Amit Dutta Banik, Supratik Pal

Quantum Physics

Tripartite entanglement of remote atomic qubits

Isabella Goetting, Ashish Kalakuntla, Mikhail Shalaev et al. (+6 more)

Distributed entanglement across multi-node quantum networks is essential for a wide range of quantum technologies, including modular quantum computers, distributed sensing and metrology, and multi-party secure communication protocols. Such large-scale quantum networks will require photonic interconnects to generate and sustain entangled states across localized nodes. Previously, three-node distributed Greenberger-Horne-Zeilinger (GHZ) states have been generated between solid-state qubits and atomic ensembles, but not yet in the platform of individual atomic qubits, which can be replicated, detected, and individually controlled with high fidelity. Here we report the first fully-distributed GHZ state of qubits across a three-node quantum network of single atomic memories, using photonic interconnects. We achieve a bounded fidelity of $0.841(17) \leq \mathcal{F} \leq 0.881(17)$ at an entanglement generation rate of 0.095(5)/sec and measure a clear violation of Mermin's inequality while closing the detection loophole for the first time in a fully-distributed multipartite entangled state.
Read the full abstract

All authors Isabella Goetting, Ashish Kalakuntla, Mikhail Shalaev, Harriet Bufan Shi, Ana Ferrari, Sagnik Saha, George Toh, Saki Male, Christopher Monroe

High Energy Physics (Theory)

Black hole equations of state and response functions

Silvester G.A. Borsboom and Manus R. Visser

We systematically develop a framework for equilibrium thermodynamics in terms of thermodynamic representations, which are choices of thermodynamic potential and independent variables, one from each conjugate pair. In each representation, equations of state arise from first derivatives of the potential and response functions from its second derivatives. We apply this framework to ideal gases and to Schwarzschild black holes in a spherical cavity in various representations, interpreting the cavity area and its conjugate surface pressure as the thermodynamic volume and pressure of a holographically dual system. For this quasi-local Schwarzschild black hole, stability depends on the thermodynamic representation, or equivalently on which variables are held fixed under equilibrium perturbations. The large black hole branch is thermally stable at fixed volume but mechanically unstable under isothermal compression, while the system is mechanically stable under adiabatic compression everywhere. At fixed pressure, the black hole is thermally unstable throughout the physical state space. We also find that the thermal expansion coefficient is negative everywhere and show that isenthalpic expansion always cools the black hole. More broadly, the framework provides a systematic route to deriving equations of state and response functions for a wide class of black hole systems using quasi-local gravitational thermodynamics.
Read the full abstract

High Energy Astrophysical Phenomena

Discovery of a Supernova Following the Einstein Probe Transient EP250302a at z = 1.131

Brendan O'Connor, Malte Busmann, James Freeburn et al. (+7 more)

We present a multi-wavelength analysis of the Einstein Probe (EP) fast X-ray transient (FXT) EP250302a located at redshift $z=1.131$. Despite its luminous prompt X-ray emission, the event was not detected in gamma-rays. Multi-wavelength follow-up identified a bright optical and X-ray source that displayed rapid chromatic flaring before returning to the standard decay of a gamma-ray burst afterglow. We interpret the chromatic flare as either due to a refreshed shock caused by a discrete shell collision or as reverse shock emission. Using the early optical data, we place constraints on the Lorentz factor of the outflow, requiring an ultrarelativistic jet with $\Gamma_0>25$. We additionally obtained deep late-time imaging with the Gemini North Telescope that reveals the presence of an optical excess at $20-30$ d post-explosion. We interpret this as supernova (SN) emission and find good agreement with the canonical broad-lined Ic SN 1998bw with a flux-scaling factor of $k_\textrm{98bw}>0.3$. This adds to the growing evidence that the majority of EP FXTs are associated with the deaths of massive stars.
Read the full abstract

All authors Brendan O'Connor, Malte Busmann, James Freeburn, Lei Hu, Noel Klingler, Daniel Gruen, Igor Andreoni, Julius Gassert, Xander J. Hall, Antonella Palmese

Nuclear Theory

Heaven and Earth: Connecting Jefferson Lab to the Cosmos

J. Piekarewicz

The nuclear equation of state (EOS) serves as the fundamental bridge between atomic nuclei and neutron stars–objects that differ in size by almost 20 orders of magnitude. Central to this connection is the nuclear symmetry energy, which controls both the neutron skin thickness of heavy nuclei and the radii of neutron stars. Recent electroweak experiments at Jefferson Lab, specifically PREX, have provided the cleanest terrestrial constraints on the EOS near saturation density. Complementary to neutron skins is the isovector giant dipole resonance, particularly the electric dipole polarizability. This contribution discusses the implications of these measurements on the nuclear EOS and the role of upcoming electroweak capabilities at Jefferson Lab in addressing their impact on the structure and composition of neutron stars.
Read the full abstract

High Energy Physics (Theory)

Thermal One-point Functions and Asymptotic CFT Data: QFT in AdS

Ilija Burić, Francesco Mangialardi, Francesco Russo et al. (+2 more)

We investigate the thermal partition and one-point functions of the three-dimensional conformal field theory dual to a massive interacting scalar field in AdS$_4$. Using thermal inversion formulas, we determine the asymptotic behaviour of the spectral density and OPE coefficients involving heavy operators at fixed spin. We first analyse these CFT data for the generalised free field, corresponding to the non-interacting bulk theory. Then we compute the first-order perturbative corrections induced by the cubic and quartic bulk interactions. The thermal observables considered here probe a sector associated with operators of large dimension and, in the bulk description, a regime dominated by states with large particle number. This regime remains comparatively unexplored even in generalised free field theory. Remarkably, the asymptotic formulas obtained from thermal inversion remain quantitatively accurate far from the asymptotic regime, describing CFT data reliably already at intermediate conformal weights. Our results show that this feature survives the inclusion of bulk interactions and provide new analytic control over heavy-state data in conformal field theories.
Read the full abstract

All authors Ilija Burić, Francesco Mangialardi, Francesco Russo, Volker Schomerus, Alessandro Vichi

Strongly Correlated Electrons

Exotic magnetism and persistent spin dynamics in a frustrated Jeff = 1/2 triangular lattice antiferromagnet

M. Barman, K. Jaksetič, M. Pregelj et al. (+3 more)

The delicate interplay between competing degrees of freedom, anisotropy, and frustration-induced strong quantum fluctuations in pseudospin-$J_{\rm eff}=1/2$ rare-earth triangular-lattice antiferromagnets offers a promising platform for the experimental realization of exotic states with nontrivial low-energy excitations. Here, we present thermodynamic, inelastic neutron scattering (INS), and muon spin relaxation ($\mu$SR) investigations of the frustrated magnet K$_3$NdTe$_2$O$9$, in which Nd$^{3+}$ ions constitute a structurally perfect triangular lattice with no detectable site disorder. The experiments reveal the realization of a Kramers doublet ground state with $J{\rm eff}=1/2$ moments, well separated from the first excited state, which interact antiferromagnetically with an exchange interaction of $\sim$0.6 K between the Nd$^{3+}$ moments in the triangular plane. The absence of oscillations and the so-called 1/3 plateau in the zero-field $\mu$SR asymmetry down to 50 mK rules out long-range magnetic ordering and spin freezing on the $\mu$SR time scale, respectively. The temperature dependence of the zero-field $\mu$SR relaxation rate is well described by the Orbach relaxation mechanism, indicating the existence of fluctuating moments in the ground state of this frustrated magnet. Our results demonstrate exotic magnetism and persistent spin dynamics down to 50 mK. These observations establish this new family of frustrated rare-earth triangular-lattice antiferromagnets as a promising venue for the experimental realization of nontrivial quantum states with exotic low-energy excitations.
Read the full abstract

All authors M. Barman, K. Jaksetič, M. Pregelj, M. D. Le. P. J. Baker, A. Zorko, P. Khuntia

General Relativity and Quantum Cosmology

Boundary conditions and Hilbert spaces in no-roll quantum cosmology

Steffen Gielen

We construct Hilbert spaces for the minisuperspace quantum cosmology of a closed Universe in the limit of extreme slow-roll inflation, in which the scalar field is approximated as constant. In this setting, the potential energy in the scalar field is an integration constant depending on initial conditions, equivalent to the cosmological constant as it appears in unimodular gravity. If one fixes the value of this integration constant, the Wheeler-DeWitt equation admits two independent solutions, and a natural inner product picks out one of them (essentially Vilenkin's tunnelling wavefunction) with positive norm. The physical Hilbert space is then one-dimensional, in agreement with some recent discussions of closed universes in quantum gravity. However, if the potential energy is left arbitrary, the theory allows for an infinite-dimensional Hilbert space corresponding to energy eigenstates of an effective Hamiltonian. Requiring that this Hamiltonian be represented as a self-adjoint operator leads to a one-parameter family of boundary conditions at the singularity, generalising the DeWitt criterion of a vanishing wavefunction. The boundary condition always leads to a mixture of Hartle-Hawking (no-boundary) and tunnelling wavefunctions, but a particular choice "almost" singles out the Hartle-Hawking wavefunction, with exponentially suppressed corrections.
Read the full abstract

High Energy Physics (Theory)

The Helical SYK Model and Emergent Infrared Integrability

Gustavo Valdivia-Mera, Bhavay Tyagi, Eric R. Bittner et al. (+1 more)

We construct a helical generalization of the Sachdev-Ye-Kitaev (SYK) model in $1+1$ dimensions, built from left- and right-moving Majorana fermions with local quartic interactions and random couplings in flavor-chirality space. These interactions organize into a symmetry-controlled hierarchy of quartic chirality sectors. At the most restrictive end of this hierarchy, symmetry forces the quartic structure into a density-density form, which admits an exact solution using bosonization, rendering the theory integrable. Once the full quartic helical interaction space is allowed, including purely chiral, chirality-balanced, and chirality-imbalanced sectors, this symmetry-protected integrable structure is lost. Nevertheless, the large-$N$ infrared limit remains analytically tractable through short-distance selection rules and disorder averaging. Using conformal perturbation theory about the free fixed point, we show that the entire interaction space is marginally irrelevant, and the theory thus becomes free and integrable in the IR.
Read the full abstract

All authors Gustavo Valdivia-Mera, Bhavay Tyagi, Eric R. Bittner, Pavan Hosur

Superconductivity

Superconductivity from emergent dipolar interactions in a fractionalized Fermi liquid

Mina-Lou Schleith, Arthur Bril and Nick Bultinck

Starting from the spin-fermion model or Hertz-Millis theory describing electrons coupled to anti-ferromagnetic spin fluctuations we develop a theory to describe the transition from a fractionalized Fermi liquid into a $d_{x^2-y^2}$ superconductor. We focus on small electron doping on top of the half-filled state. The doped electrons enter the system as spinon-chargon bound states, which form a small, reconstructed Fermi surface. The bound states are neutral under the emergent U(1) gauge symmetry of the fractionalized Fermi liquid, but interact via a dipolar two-body potential. We show that because of the projective action of translation symmetry on the spinons and chargons, the Fourier components of this repulsive dipolar interaction are peaked at the anti-ferromagnetic wave vector, thereby providing a robust microscopic mechanism for $d_{x^2-y^2}$ pairing in a fractionalized metal.
Read the full abstract

Quantum Physics

Fermionic Hamiltonian engineering with local control

Özgün Kum, Matthias Zipper, Ludwig Mathey et al. (+1 more)

Quantum simulators enable the exploration of complex quantum phenomena in condensed-matter systems by reproducing their dynamics on controllable quantum devices. However, experimental constraints often restrict the class of Hamiltonians that can be realized natively. Hamiltonian engineering addresses this limitation by expanding the set of accessible Hamiltonians beyond the fixed system Hamiltonian provided by the hardware. We introduce a framework for fermionic Hamiltonian engineering based on interleaving free evolution under the system Hamiltonian with a sequence of experimentally feasible local fermionic unitaries. The required sequences and free-evolution times are obtained efficiently through a linear program, enabling effective time evolution under a broad class of target Hamiltonians. In particular, our method realizes arbitrary complex tunnelling coefficients, constrained only by the connectivity of the underlying system Hamiltonian. We further show that symmetries of the Hamiltonian engineering task can be exploited to drastically reduce the cost of computing the control parameters, and that errors arising from finite pulse times can be compensated within the same framework through a simple modification of the linear program. To our knowledge, this is the first automated method to realize locally tunable artificial gauge fields in interacting fermionic lattice models using only site-resolved energy shifts as control. We demonstrate the method by engineering the dynamics of interacting Fermi-Hubbard chains with complex tunnelling coefficients and of the Harper-Hofstadter model on a 1088-mode lattice. For the latter, we exploit the translation symmetry of the model to determine a provably optimal six-pulse sequence that produces the desired dynamics independent of the lattice size.
Read the full abstract

All authors Özgün Kum, Matthias Zipper, Ludwig Mathey, Martin Kliesch

High Energy Astrophysical Phenomena

QPO-like Signatures and Hydrodynamical Variability in Accretion around a JNW-type Compact Spacetime in Freund-Nambu Scalar-Tensor Gravity

Orhan Donmez, M. Yousaf and G. Mustafa

Scalar tensor theories of gravity provide a broad as well as physically rich extension of general theory of relativity by allowing the gravitational interaction to be mediated not only by the spacetime metric but also by scalar degrees of freedom. In this manuscript, we present a new exact solution in the Freund-Nambu scalar-tensor (FNST) gravity scenario, representing a nontrivial scalar-tensor generalization of the Janis-Newman-Winicour naked-singularity geometry, characterized by an additional coupling parameter q in the scalar sector. We also numerically solve the general relativistic hydrodynamic equations in order to investigate the shock-cone mechanism formed by Bondi-Hoyle-Lyttleton accretion around this compact spacetime on the equatorial plane. We show that stronger scalar-tensor deviations modify the shock-cone morphology, significantly increase the amount of matter accumulated near the central compact object, and enhance the oscillatory behavior of the shock cone. The Lorentzian-like peaks obtained from the numerically computed power spectral density are interpreted as hydrodynamically generated QPO-like modes. These modes are driven by shock cone oscillations and by the compression and rarefaction of the plasma trapped inside the cone. Finally, for a compact object with mass parameter M = 10M_sun, the numerically extracted frequencies are found mainly in the range from a few Hz up to approximately 100 Hz. These frequencies overlap with the QPO ranges reported in stellar-mass black-hole-candidate systems. In particular, the frequencies obtained for the FNST2-FNST4 models fall within the range of timing features reported for the source GRS 1915+105. These results suggest that the exterior hydrodynamical variability of FNST compact spacetimes may provide phenomenological diagnostics of scalar-field-induced deviations from the Schwarzschild reference case.
Read the full abstract

High Energy Astrophysical Phenomena

Optical polarization variability and its relation to gamma-ray activity in blazars

Styliana Grigoriou, Anastasia Glykopoulou and Ioannis Liodakis

Optical polarization can be an important probe of particle acceleration and high-energy emission processes in relativistic jets from supermassive black holes. We combined publicly available observations from three past blazar monitoring programs to produce densely sampled light curves for 15 blazars in order to explore the relation of gamma-ray activity to the polarization variability as well as discover new rotations of the polarization angle. We find that the polarization degree does not correlate with the gamma-ray flux for individual sources nor different subsamples of blazars, potentially indicating multiple emission mechanisms. In the combined dataset, we identified a total of 64 rotations in 12 sources, 39 of which are newly identified rotations. We confirm the trend found in previous works for the whole sample: lower polarization degrees during periods of polarization angle rotations. However, looking at the individual sources, we identified cases where the rotation and non-rotation polarization degree distributions are indistinguishable, providing further evidence for the multiple emission mechanism hypothesis.
Read the full abstract

High Energy Physics (Phenomenology)

Freeze-in and ultra-relativistic freeze-out during general reheating scenarios

Kuldeep Deka

The dark-matter relic abundance can depend sensitively on the thermal history before radiation domination. We derive a general analytic framework for dark-matter production from the Standard Model bath during a non-instantaneous reheating era, unifying freeze-in, ultra-relativistic freeze-out and the approach to ordinary non-relativistic freeze-out. The reheating background is described by an effective equation-of-state parameter $\omega$ and a cooling index $\alpha$, while the dark-matter interaction rate is parametrised by an effective scale $\Lambda$ and a leading temperature power $n$. We show that the production history is organised by two critical temperature exponents: one controls whether a thermalised relativistic species decouples during reheating or after radiation domination begins, and the other controls whether post-decoupling production is infrared dominated, ultraviolet dominated or logarithmic. We derive analytic relic yields in the main regimes, including both the entropy-diluted freeze-out contribution and the post-freeze-out production term. These results explain the scaling of relic-density contours and are checked against numerical Boltzmann solutions. For matter-like reheating our framework reproduces the known IR/UV ultra-relativistic freeze-out structure, while more general reheating histories can shift the same microscopic interaction between freeze-in, ultra-relativistic freeze-out and ordinary freeze-out regimes.
Read the full abstract

Statistical Mechanics

Derivation of height field theory for the two-dimensional classical dimer model from a Grassmann-integral representation

Stephen Powell

The classical dimer model on bipartite lattices hosts a Coulomb phase, characterized by algebraic correlations and topological order. Its long-wavelength properties can be described by the fluctuations of a vector field with zero divergence, which, in two dimensions, is equivalent to a continuum height model. We show how this field theory can be derived constructively for both square and honeycomb lattices, starting from an exact representation of the dimer model in terms of Grassmann integrals. Taking the continuum limit gives a massless Dirac fermion in two-dimensional Euclidean space, which, using bosonization in the path integral representation, maps exactly to the well-known height field theory, incorporating the relationship between its boundary discontinuity (or "tilt") and the flux. By including source terms coupling to the flux density and the local valence-bond-solid order parameter, which we show are the only ones required to describe the asymptotic long-distance correlations, we derive expressions for the dimer observables in terms of the height.
Read the full abstract

Astrophysics of Galaxies

Chemical hints of Population III stars from silicon abundances in massive galaxies

E. Eftekhari, A. Ferré-Mateu, A. Vazdekis et al. (+4 more)

The formation of massive galaxies remains a fundamental question in astrophysics, with recent JWST observations suggesting that intense star formation occurred earlier than previously expected. We used the prototypical massive relic galaxy NGC 1277 as a fossil record to probe the chemical signatures of early star formation. With a stellar mass of $1.2 \pm 0.4 \times 10^{11}M_\odot$ and a compact structure (half-light radius of 1.2 kpc), NGC 1277 is representative of massive relic galaxies-systems that formed rapidly at high redshifts ("red nuggets" at $z>2$) and have since undergone largely passive evolution, preserving the imprint of their earliest stellar populations. Using deep near-infrared spectroscopy, we identified unusually strong silicon (Si) absorption features in this galaxy. We measure $[\mathrm{Si}/\mathrm{Fe}]=1.05^{+0.45}_{-0.27}$ and $[\mathrm{Mg}/\mathrm{Fe}]=0.36^{+0.27}_{-0.24}$, corresponding to a significantly enhanced silicon-to-magnesium ratio ($[\mathrm{Si}/\mathrm{Mg}]=0.67^{+0.45}_{-0.27}$) which cannot be reproduced by current stellar population models or typical core-collapse supernova yields. This enhancement suggests a contribution from very massive, metal-poor progenitors during the earliest phases of star formation. Such conditions are consistent with nucleosynthetic yields from pair-instability supernovae or other enrichment channels associated with extremely massive stars, whose chemical signatures are expected to remain less diluted in systems like NGC 1277 due to their rapid formation timescales and minimal late-time accretion. This result provides rare chemical evidence of early massive-star enrichment preserved in a local relic galaxy and opens a new observational window into the chemical evolution of the Universe.
Read the full abstract

All authors E. Eftekhari, A. Ferré-Mateu, A. Vazdekis, F. La Barbera, M. A. Beasley, J. P. V. Benedetti, M. Kriek