Astrophysics of Galaxies
Cosmic Evolution Survey: LOFAR 144 MHz imaging of the COSMOS field
E. Vardoulaki, T. Shimwell, M. J. Hardcastle et al. (+18 more)
We present the first deep, targeted LOFAR 144 MHz source catalogue of the COSMOS field, together with the first 144 MHz source counts in this field. The data comprise 48 h of observations. Over the 2.6 sq. deg. region adopted for the catalogue analysis, the final Dutch-array image reaches a median rms sensitivity of ~100 uJy/beam at an angular resolution of 15" x 6". The resulting catalogue contains 1984
radio sources; a peak S/N >= 5 selection is adopted for the resolved/unresolved classification and source-count analysis. We characterised the catalogue using Monte Carlo source-injection and recovery simulations, including dedicated simulations of extended sources, to quantify completeness, flux-density redistribution, and morphology-dependent source-recovery effects. The catalogue reaches 90% completeness at 1.48 mJy. The resulting Euclidean-normalised differential source counts are measured down to ~0.4 mJy and show good agreement with LoTSS DR3 144 MHz source counts and with the VLA-COSMOS 3 GHz counts scaled to 144 MHz, with ~5% of catalogue sources having multiple 3 GHz counterparts within a beam-matched search region. Comparison with the VLA-COSMOS 3 GHz catalogue shows good astrometric agreement, with median offsets of Delta_RA = 0.35" (+0.03"/-0.05") and Delta_Dec = -0.83" (+0.02"/-0.03"), approximately 6% of the corresponding synthesised-beam dimensions, and no significant radial dependence across the field. The resulting catalogue provides a low-frequency view of COSMOS and a reference
dataset for future deeper LOFAR observations and multiwavelength studies of this extensively characterised extragalactic field.
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All authors E. Vardoulaki, T. Shimwell, M. J. Hardcastle, L. Doukas, L. K. Morabito, C. L. Hale, M. T. Sargent, V. Smolčić, G. Zamorani, G. Gozaliasl, F. An, M. Aravena, A. L. Faisst, M. Vaccari, E. Treister, A. Finoguenov, P. Best, J. S. Kartaltepe, C. Casey, S. Jin, V. Mainieri
Solar and Stellar Astrophysics
Anchoring the Chromospheric Activity$-$Rotation Relation: A Study of the Pleiades and Group X
A. Núñez, M. A. Agüeros, J. L. Curtis et al. (+1 more)
We present a study of the rotation and the chromospheric H$\alpha$ activity of low-mass
stars in the $\approx$120 Myr-old Pleiades and the $\approx$400 Myr-old Group X open clusters. We combine published and new rotation periods ($P_\mathrm{rot}$) from TESS and ZTF, and use LAMOST, SDSS, and MDM spectra to measure H$\alpha$ equivalent widths (EWs). While overall the Group X distributions of $P_\mathrm{rot}$ and EWs are as expected, detailed comparisons to the Pleiades and to the 700-Myr-old
benchmark Praesepe produce some surprises. For F through mid K
stars, the Group X color$-$period sequence lies between those of the Pleiades and of Praesepe, as expected. But the $P_\mathrm{rot}$ for its late K and early M dwarfs and the Praesepe slow-rotator sequence overlap, indicating that the 700 Myr-old
stars have not spun down significantly despite being nearly twice as old as their Group X counterparts. In the Rossby number$-L_\mathrm{H\alpha}/L_\mathrm{bol}$ plane, rapid rotators in Group X are saturated, as is seen in older clusters, whereas the rapid rotators in the Pleiades show a weak but measurable dependence of $L_\mathrm{H\alpha}/L_\mathrm{bol}$ on rotation. This implies that the chromospheric activity$-$rotation relation attains its mature form between 120 and 400 Myr. Dividing the sample by color reveals that K, M0, and M1 dwarfs are no longer saturated by $\approx$120 Myr, M2 and M3 dwarfs become unsaturated between $\approx$400 and $\approx$700 Myr, and later M dwarfs remain largely saturated through field ages even as their saturated $L_\mathrm{H\alpha}/L_\mathrm{bol}$ levels decline, indicating that chromospheric
evolution is not determined by rotation period alone.
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All authors A. Núñez, M. A. Agüeros, J. L. Curtis, C. A. Ospinal Achicanoy
High Energy Physics (Theory) · Cross-listed from math.RA
Okubo algebras and Exceptional Periodicity: tetracode gradings, root-lattice obstructions and Clifford cones
Alessio Marrani and Daniele Corradetti
The Okubo
algebra brings together ternary gradings, integral root frames and rank-three geometry. We examine how these structures extend to the complex Exceptional Periodicity
algebras. With $N=4(n+1)$, a tetracode character gives eight nonzero homogeneous components of dimension $t_n=8n+3+2^{4n}$. On a tip, a compatible grading has zero component of dimension $8n-5$ and eight nonzero components of dimension $1+2^{4n-3}$. The arithmetic behaves differently: for $n\geq2$, the
lattice $D_N^+$ has no full-rank orthogonal frame of unscaled $A_2$
lattices. We exhibit failures of the Jacobi and Jordan identities and determine the derivations and full automorphism group of the ambient
algebra above level one. We also give a Clifford-module proof, with the normalization fixed by root products, of the published realization of EP tips as special Vinberg $H$-
algebras. This identifies a positive real form and yields explicit formulas for its cone, cubic, Cholesky coordinates and rational dual invariant. The cone is symmetric exactly at $n=1$. Its determinant-one hypersurface belongs to the known $L(8n,1,0)$ series, whose $r$- and $c$-maps give homogeneous scalar
manifolds for supergravity theories with eight real supercharges.
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High Energy Astrophysical Phenomena
The ePESSTO+ census of ZTF nuclear transients. I. What flares in galactic nuclei?
E. Concepción, T. Petrushevska, G. Leloudas et al. (+21 more)
Transients in galactic
nuclei arise from distinct processes, only some of which trace the supermassive black hole (SMBH). These include tidal disruption events (TDEs), changing-look active galactic
nuclei, Bowen fluorescence
flares (BFFs) and ambiguous nuclear transients, alongside
supernovae that appear nuclear but are unrelated to the SMBH. Reliable classification requires spectroscopy, which will not scale to the alert volumes of the Legacy Survey of Space and Time (LSST). We aim to characterise the population of nuclear transients, to identify early observables capable of distinguishing SMBH-related
flares, and TDEs in particular, from the dominant
supernova background, and to assess the biases this selection introduces. We implemented a real-time filter on the Lasair broker, selecting transients from the Zwicky Transient Facility (ZTF) alert stream by nuclear coincidence with the host
galaxy, with no photometric cuts, to retain SMBH-related
flares in both quiescent and active hosts. The filter ran over 16 months, with candidates reported for classification through ePESSTO+ and other facilities. The filter returned 476 candidates, of which 202 were spectroscopically classified, yielding predominantly
supernovae, 10 confirmed TDEs (5%) and one BFF. The mean g-r colour and the rise time separate TDEs from the
supernova background. Our filter recovers 10 of the 25 TDEs classified in the same period and declination range; most misses are technical or observational rather than physical. Simple real-time filtering combined with basic photometric criteria can already isolate TDEs efficiently from nuclear transient alert streams, and high completeness is achievable. In the LSST era, where samples will be predominantly photometric, selection bias will become as important as contamination, and retaining
flares in active hosts is necessary if unusual events are not to be excluded.
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All authors E. Concepción, T. Petrushevska, G. Leloudas, D. Ilić, M. Gromadzki, S. Bhattacharyya, P. Charalampopoulos, A. Gomboc, N. Ihanec, M. Nicholl, P. J. Pessi, D. R. Young, P. Wiseman, T.-W. Chen, M. Dennefeld, Y. Dgany, C. P. Gutiérrez, C. Inserra, L. Makrygianni, T. E. Müller-Bravo, S. Nissen, F. Onori, R. Roy, M. Quilt
Other Condensed Matter
Momentum conservation for ab initio calculations with pseudopotentials via a phase space electronic structure formulation
Guy Ohad, Nadine C. Bradbury and Joseph E. Subotnik
We demonstrate how to build a robust phase space electronic
Hamiltonian $\hat{H}_\text{PS}(\boldsymbol{R},\boldsymbol{P})$ that depends on nuclear position $\boldsymbol{R}$ and nuclear momentum $\boldsymbol{P}$ in the presence of ionic pseudopotentials. In particular, we show that in order to account for the non-local component of a pseudopotential while also conserving linear and angular momentum, one is forced to introduce a non-local one-electron operator $\hat{\boldsymbol{\Gamma}}^\text{nl}$ that couples electronic and nuclear momenta together. To test the validity of our ansatz, we derive a generalized form of Nafie's exact equality (which relates electronic momentum and electronic position) so as to include the presence of pseudopotentials. We then
benchmark our proposed phase space electronic structure theory against this generalized Nafie-like result for a diverse set of diatomic molecules spanning a wide range of elements. We find excellent agreement across this ab initio test set, highlighting the strength of our method in capturing meaningful electronic momentum beyond the Born-Oppenheimer framework.
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Mesoscale and Nanoscale Physics
Plasmon modes in triple-point semimetal, its quadratic cousin, and Hopf semimetal
Ipsita Mandal
We study collective charge excitations in pseudospin-1 triple-point semimetals within the random-phase approximation, considering both the linearised model with a flat-band and its quadratic-corrected counterpart. We analyse their density response, Drude weights, screening, plasmon dispersion and damping, particle-hole continua, and Friedel oscillations from the long-wavelength to the arbitrary-momentum regime. The quadratic correction renders the flat-band dispersive and endows it with a Fermi surface, thereby affecting the overall response. Comparisons with Weyl and Hopf semimetals reveal how bandstructure and
quantum geometry jointly govern collective charge dynamics. While the Drude weights are determined by the Fermi surface and band-velocities, interband screening, plasmon dispersion, and Friedel oscillations reflect the
quantum geometry of the eigenstates.
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Instrumentation and Detectors
The Energetic Particle Detector Instrument on ELFIN
Colin Wilkins, Ryan Caron, Ethan Tsai et al. (+24 more)
We present the design methodology, implementation, and data products of the Energetic Particle Detector (EPD) instrument on-board the Electron Losses and Fields Investigation (ELFIN) dual SmallSat mission. ELFIN was designed to study the time-
evolution of energetic particle distributions in Earth's magnetosphere, having operated in polar Low Earth Orbit (LEO) from 2018 to 2022. Each satellite's instrument payload contained a pair of detector heads to sense differential-directional fluxes of 50 keV to $\sim$5 MeV electrons (EPDE), and 50 keV to $\sim$2 MeV atomic ions (EPDI), with an energy resolution better than 50% ($\Delta E/E<0.5$). The satellites were spinning with a nominal period of 2.8 s in a plane containing Earth's background
magnetic field, with particle counting intervals subdivided into 16 consecutive
spin sectors. Each EPD was paired with a three-axis Fluxgate Magnetometer (FGM) sampled at 80 Hz for local pitch-angle determination. Each detector head operated on the principle of pulse-height analysis (PHA) in solid state media, collimated by a rectangular 22.5$^\circ$ field of view and entrance aperture. The EPDE contained a stack of 6 silicon detectors (0.7 cm total thickness) with 0.15 cm$^2$ str
geometric factor, with ion contamination mitigated by an aperture foil and digital coincidence logic. The EPDI contained a stack of 2 silicon detectors (0.1 cm total thickness) with 0.03 cm$^2$ str
geometric factor, with electron contamination mitigated by a
magnetic broom stage and digital anti-coincidence logic. The total assembled mass, volume, and power required for the EPD detector heads and
circuit boards were 939 g, 10$\times$9.8$\times$8.4 cm$^3$, and 2.3 W, respectively. We describe each EPD design element alongside instrument data products and processing.
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All authors Colin Wilkins, Ryan Caron, Ethan Tsai, Chris Shaffer, Patrick Cruce, Maxwell Chung, Andrei Runov, Jiang Liu, Drew Turner, Yuri Shprits, Wen Li, Michael Lawson, Emmanuel Masongsong, Cindy Russell, Eric Grimes, Jiashu Wu, Matthew Allen, Jessica Artinger, Alex Flemming, Brayden Hesford, Laura Iglesias, James King, Austin Norris, Carter Pedersen, Daniel Thomlinson, Wynne Turner, Vassilis Angelopoulos
Statistical Mechanics
Exact Microscopic One-Body Reduction in the Symmetric Exclusion Process
Olivier Bénichou and Aurélien Grabsch
The symmetric exclusion process (SEP) is a paradigmatic model of interacting particle transport. Its current–density correlations are governed by an infinite many-body hierarchy of equations. Only recently, this hierarchy was found to collapse at large scales onto a single closed equation. Is this remarkable simplification created by coarse graining, or does it reflect a deeper property already present in the microscopic dynamics? Here we show that the second scenario is realized. At arbitrary time on the
lattice, the entire hierarchy collapses onto a single linear equation which is exactly equivalent to a persistence problem for a single auxiliary random walker. Thus an interacting many-body problem reduces exactly to a genuine one-body problem before any scaling limit is taken. This reduction determines the complete finite-time correlation profile, including during nonequilibrium relaxation. More broadly, the microscopic operator uncovered here opens a route to more general correlation functions in the SEP, and may point to a general organizing principle for nonequilibrium interacting particle systems.
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Mathematical Physics · Cross-listed from math.GT
A proof of the framed LMOV conjecture for links
Kefeng Liu, Pan Peng and Shengmao Zhu
We prove the Labastida–Mariño–Ooguri–Vafa
conjecture for oriented links with arbitrary integer framings. Consequently, the framed reformulated invariants have finite integral LMOV expansions for every integer framing vector.
Astrophysics of Galaxies
Dynamical formation of dormant black holes: Predictions for Gaia DR4
Daniel Marín Pina, Michela Mapelli, Giuliano Iorio et al. (+1 more)
Dormant black holes (dormant BHs, i.e., X-ray quiet binaries comprising a BH and a companion
star) are probes of the effect of cluster dynamics and binary stellar
evolution on compact-object binaries. A dozen dormant BH binaries are known, a number that will increase substantially with the upcoming Gaia Data Release 4 (DR4). Their origin is uncertain, and dynamical formation is proposed as one possible channel. Here, we study the formation of dormant BHs in low-mass
star clusters, accounting for the interplay of binary stellar
evolution and cluster dynamics. We present new simulations with the $N$-body code PeTar, interfaced with the population synthesis code SEVN for single and binary
star evolution. Our grid spans a range of cluster masses ($300-4800\,$M$_\odot$),
metallicities ($1.4\times10^{-2}$, $1.4\times10^{-4}$), and natal kick models (with and without fallback). We find that almost all dormant BH binaries escape the parent cluster within $\sim1\,$Gyr ($\sim10\,$Myr) when assuming weak (strong) natal kicks. Most ($73\%$) dormant BHs form via the exchange of a BH (or its progenitor
star) into a stellar binary, or of a
star into a binary with a BH. Dormant BHs in low-mass clusters have a wide orbital period distribution (from a few hours to $10^8\,$d), with an upper limit set by natal kicks, a bimodal eccentricity distribution (a first peak at zero eccentricity for circularised systems and a second at high eccentricity), and stellar masses that follow the (evolved) initial mass function. Large BH masses are a smoking gun of dynamical formation, via exchanges and stellar collisions. We expect Gaia DR4 to contain $\sim1-64$ high-
metallicity and $\sim0.4-48$ low-
metallicity dormant BHs, with a period distribution peaking at $\sim10^3\,$d, $\gtrsim90\%$ of them with eccentricity $e>0.1$, and $\sim20\%$ with large BH masses ($m_{\rm BH} \gtrsim 30\,$M$_\odot$).
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All authors Daniel Marín Pina, Michela Mapelli, Giuliano Iorio, Cecilia Sgalletta
High Energy Physics (Theory)
Black Strings and Black Holes: Worldsheet Spectra and Near-Extremal Limits
Ziyi Li
We study aspects of the Euclidean partition function of the $\frac{SL(2,\mathbb R)\times U(1)}{U(1)}$ gauged WZW model. The target space geometry is either a smooth horizonless geometry with a linear-dilaton asymptotic region, or the Horne–Horowitz black string, depending on which circles we unwind as the time-direction. We first study the worldsheet spectrum and obtain the character decomposition via the holonomy integrals. Next, we obtain the spacetime spectrum of the horizonless geometry by directly performing the unfolded modular integrals, and recover the Maldacena-Ooguri-Son spectrum in the ungauged limit. When the chirally charged three-dimensional black string is dimensionally reduced, the target space is instead a two-dimensional charged black hole. We study the near extremal regime of the black hole and black string. For the two dimensional black hole, we propose two candidate towers of states that produce the expected $\frac{3}{2}\log T$ of the AdS$_2$ throat from the worldsheet discrete series representation. These towers appear only below the temperature at which the full amplitude becomes divergent. We comment on the contribution of these states in the near-extremal limit of the full partition function.
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Quantum Physics
$T$-efficient unitary synthesis via block-sparse Hamiltonian simulation
Diyi Liu, Shuchen Zhu, Wibe Albert de Jong et al. (+3 more)
We construct Clifford+$T$
circuits implementing arbitrary $n$-
qubit unitaries with worst-case $T$-count $\widetilde{O}(N^{8/7})$ at constant operator-norm error, where $N=2^n$, improving the previous exponent $5/4$. The construction uses $\widetilde{O}(N^{6/7})$ clean ancillas. The main idea is to reduce the data addressed by each query to the block-encoding
circuit for a sparse piece while controlling the additional simulation work needed to combine the pieces. We simulate a Hermitian logarithm of the target by flattening its traceless part with a two-layer random similarity transformation, randomly partitioning the transformed generator into block-sparse Hermitian pieces, and combining their evolutions using qDRIFT. For a target operator-norm error $\epsilon\in(0,1/2)$, let $L=\log_2(N/\epsilon)$, the
qubit count plus the requested bits of accuracy. By successively correcting the approximation error, we obtain a
circuit using $\widetilde{O}(N^{8/7}L^{3/7}+NL)$ $T$ gates and $\widetilde{O}(N)$ clean ancillas whenever $L\le N$. We also prove that, at constant precision, the exponent $8/7$ is optimal within a sequential block-SELECT model.
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All authors Diyi Liu, Shuchen Zhu, Wibe Albert de Jong, Di Fang, David Williams-Young, Chao Yang
General Relativity and Quantum Cosmology · Cross-listed from math.CA
Hypergeometric solutions to coupled Klein-Gordon equations in cosmology with small-field excursions
Amin Aboubrahim, Anastasiia Minenkova and Tomas Yonkers
The Klein-Gordon equation is a second order differential equation that appears in a variety of applications in mathematics, physics and engineering. This equation is often solved using numerical methods, since a general analytical solution is unattainable. However, one can find very useful analytical solutions for some special cases. In cosmology, the Klein-Gordon equation of a field can explain the physics of inflation and has important consequences on understanding the origin and
evolution of the universe. An analytical solution to the Klein-Gordon equation in cosmology has been obtained in the small-field excursion approximation, and it turns out that the solution can be written in terms of the confluent hypergeometric limit function. In this work, we derive this result again while showing the details of the calculations and then generalize to the case of two coupled Klein-Gordon equations. We show that the solution of this coupled system can be written in terms of Kummer's hypergeometric limit function while considering minimal assumptions. We carry out a full numerical calculation of the coupled system and compare it to the results from the analytical expressions.
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Quantum Physics
Can the system dynamics remain structurally non-Markovian while its experimentally accessible memory signatures disappear?
Sayan Sengupta, Anish Sharma, George Biswas et al. (+1 more)
We investigate how unresolved quasistatic disorder in system bath coupling affects non-Markovian dynamics in
spin environments. The coupling is fixed within each experimental shot but varies between shots, so repeated shot
tomography reconstructs a disorder averaged dynamical map. For a single
spin bath with pure dephasing Ising interaction, disorder can drive a transition to CP-divisible dynamics for fixed bath preparations, with a critical strength set by bath polarization along the interaction axis. However, when the bath state fluctuates physically between shots, the averaged dynamics remain CP indivisible at any finite disorder strength. We extend these results analytically to inhomogeneously coupled pure dephasing baths of any number \(N\) of non-interacting
spins. At any finite disorder strength, one unpolarized bath
spin suffices to retain CP-indivisible dynamics, whereas a fully polarized bath yields Markovian (CP-divisible) dynamics. Dynamics with physically fluctuating bath states likewise remain non-Markovian (CP indivisible) at finite disorder for arbitrary \(N\) in the pure dephasing case. For anisotropic Heisenberg interactions, any nonzero transverse exchange eliminates the disorder driven transition to CP divisibility in a single
spin bath. Exact diagonalization of anisotropic models with inhomogeneous couplings up to \(N=12\) reveals persistent trace distance revivals for fixed bath preparations, sampled Haar random preparations, and physically fluctuating bath states, showing that this effect of transverse exchange extends beyond a single bath
spin. Increasing disorder still suppresses experimentally accessible revivals and can make
memory effects unresolvable at finite measurement resolution even as the dynamics remain CP indivisible. Thus, transverse exchange and physical bath state fluctuations preserve dynamical indivisibility against unresolved coupling disorder.
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All authors Sayan Sengupta, Anish Sharma, George Biswas, Anindya Biswas
Astrophysics of Galaxies
Massive double-exponential galaxies with extended LSB emission: An IllustrisTNG exploration II -are they unique?
Suchira Sarkar, Kanak Saha and Anshuman Borgohain
The massive disk
galaxies (stellar mass >= 10^11 M_solar ) in the local universe (z < 0.1) encode challenging aspects of
galaxy formation physics. We have studied one class of such
galaxies - the giant low surface brightness
galaxies (gLSBs) that show a hybrid morphology - a central Sersic, an inner high surface brightness, exponential stellar disk surrounded by an outer, extended low surface brightness disk, using large volume IllustrisTNG-100 simulation. This is motivated by the recent observation of several such systems and an earlier work by Sarkar & Saha (2025) from IllustrisTNG-50. We find that despite using a ~ 10 times larger volume simulation, only ~11% of massive disk
galaxies show such morphology, consistent with findings from TNG50. This shows robustly that such
galaxies are not common in the local universe. We compared them with the typical disk
galaxies from observations, and single-exponential gLSBs from TNG100. We show that while the inner disk components lie well within the central surface brightness vs. radial scale length distribution of the typical disks, the outer LSB disks lie significantly at the outskirt, occupying a unique space. Their median bulge-to-total ratio is ~ 0.2 making them disk dominated, similar to the typical disks and the single-exponential gLSBs. We find their median dark matter mass fraction to be high (~ 0.9), typical of gLSBs. The outer LSB disks reach fainter central surface brightness and larger scale length values than the single-exponential gLSBs. Our exploration will be useful in understanding their formation mechanism across
cosmic time.
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Materials Science
Time-Resolved Phonon Dispersions of Thermally Excited Graphite at the Nanoscale
Mairi McCauley, Christoph T. Koch and Benedikt Haas
Lattice vibrations govern the propagation of heat in materials, and investigating their dynamics through time-resolved
phonon dispersion measurements would provide insight into these excitations and their interactions. However, time-resolved measurements that directly resolve the
phonon dispersion at the nanoscale have not been previously demonstrated. Momentum-resolved vibrational electron energy loss spectroscopy (EELS) provides access to
phonon energies and momenta with nanoscale spatial resolution. Here, we combine momentum-resolved vibrational EELS with pulsed
laser heating and synchronised gated electron detection to observe the
phonon dispersion of graphite during controlled heating and cooling on the microsecond timescale. Recording both the gain and loss spectra at defined times relative to
laser excitation, we determine the temperature at each time delay and follow changes to the
phonon branches as a function of temperature. The momentum-resolved spectra reveal a decrease in energy of the optical
phonon branch with increasing temperature accompanied by an increase in peak width. These changes are consistent with temperature-dependent
phonon renormalisation and scattering associated with anharmonic interactions. The approach is compatible with detector gating on timescales down to 50 ns, providing a route towards extending these measurements to faster dynamics. This work demonstrates time-resolved
phonon dispersion spectroscopy using vibrational EELS and provides a route towards probing temperature-dependent
phonon dynamics at the nanoscale with simultaneous energy and momentum resolution.
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Optics
Mode locking by phase-sensitive amplification
Francesco De Lucia, Yifan Sun, Georges Semaan et al. (+4 more)
Mode locking is the mechanism by which
lasers organize many optical modes into stable trains of ultrashort pulses. It underpins optical frequency combs, precision timing and spectroscopy, and provides the phase-coherent waveforms required for applications ranging from strong-field physics to optical frequency metrology. Conventional pulse-forming mechanisms select pulse amplitude without fixing its phase relative to an external optical reference, leaving pulse formation and optical-phase stabilization as separate functions. Phase-sensitive amplification offers a different possibility: the optical reference can participate directly in pulse formation. Here we demonstrate this principle in a continuously pumped oscillator. Kerr-induced phase
evolution and cavity detuning turn pump-referenced parametric gain into a power-dependent discriminator that supports stable single-
soliton operation. Roundtrip-resolved interferometry reveals that the
soliton optical phase remains referenced to the master
laser modulo $\pi$. These results establish phase-sensitive mode locking, in which pulse-amplitude selection and optical-phase referencing arise from the same coherent nonlinear feedback.
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All authors Francesco De Lucia, Yifan Sun, Georges Semaan, Clement Dupont, Nicolas Englebert, Simon-Pierre Gorza, François Leo
Nuclear Theory
Shear viscosity from fluctuations in linearized relativistic hydrodynamics
Jakub Sterba, Iurii Karpenko, Marlene Nahrgang et al. (+1 more)
In this work we incorporate thermal fluctuations into fluid-dynamic simulations with the vHLLE code, in linear approximation. The fluctuations are built in following the fluctuation-dissipation
theorem. The effect of space discretization into
cells in numerical hydrodynamics on the spatial correlation of fluctuations is studied with the help of static structure factor. A difference from the continuum result is pointed out and systematically investigated. Time
evolution of the ensuing fluctuations is examined and the Green-Kubo formula is used for the extraction of shear viscosity from the fluctuations. The extracted value is demonstrated to be the same as the input value of the shear viscosity for the simulations using Israel-Stewart equations. It is also shown that numerical regulators commonly used in the codes to ensure stability of the calculation severely spoil the fluctuations and break the fluctuation-dissipation
theorem.
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All authors Jakub Sterba, Iurii Karpenko, Marlene Nahrgang, Boris Tomasik
Quantum Physics
On the Increase of Boltzmann Entropy in Closed Macroscopic Quantum Systems
Cedric Igelspacher and Roderich Tumulka
We consider a closed macroscopic
quantum system in a pure state $\psi$ evolving unitarily with
Hamiltonian $H$ in a finite-dimensional
Hilbert space $\mathscr{H}$. Following von Neumann, we assume a decomposition of $\mathscr{H}$ into mutually orthogonal subspaces $\mathscr{H}_{\nu}$, where each $\nu$ represents a macro state, and $\mathscr{H}_\nu$ contains the pure states compatible with $\nu$. We define the
quantum Boltzmann
entropy for a macro state $\nu$ as $S_\mathrm{qB}(\nu) = k_{\mathrm{B}} \log \dim \mathscr{H}_{\nu}$, where $k_\mathrm{B}$ is the Boltzmann constant. Goldstein et al. [http://arxiv.org/abs/1903.11870] have suggested, as a version of the second law of thermodynamics, that $S_\mathrm{qB}$ predominantly increases with time for realistic macroscopic systems. Here, we discuss precise versions of this statement and confirm them for several simple models of $H$ and $\mathscr{H}_\nu$.
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Materials Science
Direct growth of crystalline spinel GaON films: A wide-bandgap mixed-anion semiconductor
Baikui Li, Zecheng Yang, Wenhao Yin et al. (+5 more)
Mixed-anion
semiconductors offer opportunities for bandgap engineering beyond conventional multication
alloys, but competing phases and disorder complicate their synthesis and the identification of their electronic properties. Gallium oxynitride (GaON) could connect the technologically important GaN and Ga2O3 systems, yet establishing a clear relation between its
crystal structure, composition and bandgap remains challenging. Here we report the direct growth of crystalline spinel gamma-GaON films by nitrogen-
plasma-assisted pulsed-
laser deposition. Varying the nitrogen and oxygen supply yields monoclinic beta-Ga2O3, predominantly disordered films and crystalline spinel GaON. Complementary diffraction, atomic-resolution microscopy and elemental analysis establish the spinel structure and nitrogen incorporation. Temperature-dependent photocurrent spectroscopy reveals a clear
redshift of the crystalline gamma-GaON response, supporting assignment of a band-edge transition near 4.3 eV at room temperature. These results open opportunities to investigate mixed-anion wide-bandgap
semiconductor physics and develop
heterostructures.
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All authors Baikui Li, Zecheng Yang, Wenhao Yin, Zijing Wu, Haitao Zhao, Yunwei Sheng, Honglei Wu, Jiannong Wang
Materials Science
A Transferable Machine-Learned Potential Enabling Large-Scale Copper-Carbon Simulations from Equilibrium to Extreme Conditions
Feiyu Zhou, Wei Qiu, Yan Chen et al. (+4 more)
Cu-C materials and interfaces are central to diamond thermal management, metallization,
graphene growth and carbon-coating technologies, but atomistic simulations across these applications require a potential that describes metallic Cu, diverse carbon bonding, heterogeneous Cu-C interactions and close atomic encounters. Here we develop NEP-CuC, a transferable neuroevolution potential trained on a
dataset of 2,727 uniformly relabelled configurations selected from a heterogeneous Cu-C candidate pool. Disagreement within an ensemble of five independently trained models provides an internal indicator of model sensitivity. A Ziegler-Biersack-Littmark (ZBL) correction describes short-range nuclear repulsion, while a runtime D3(BJ) correction supplements dispersion-sensitive calculations. Tests on source-derived held-out and independent external
datasets, together with structural, elastic, defect, interfacial, vibrational and finite-temperature transport
benchmarks, establish broad but property-dependent physical fidelity across elemental Cu, diverse carbon environments and heterogeneous Cu-C configurations. Large-scale simulations of amorphous-carbon formation and orientation-dependent shock compression of Cu further test transferability under strongly non-
equilibrium conditions. For Cu/diamond interfaces, the same potential describes deposition, annealing and tensile response: preparation history leaves persistent differences in interphase structure, while the mean peak nominal tensile stress at 500 K decreases from $12.35\pm0.71$ to $6.65\pm0.98$ GPa as the incident Cu energy during the initial deposition stage increases from 1 to 50 eV. NEP-CuC provides an atomistic framework for linking processing, interfacial structure and physical response across Cu-C systems, with direct relevance to Cu/diamond thermal-management interfaces, diamond metallization and non-
equilibrium Cu-C processing.
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All authors Feiyu Zhou, Wei Qiu, Yan Chen, Jiahui Liu, Yilun Liu, Shengying Yue, Penghua Ying
General Relativity and Quantum Cosmology
Mini-Superspace Hamiltonian Dynamics and Canonical Quantization of Bumblebee Cosmology
Pranjal Sarmah
The work presents a canonical
Hamiltonian system in a classical scenario and further extend the analysis to a
quantum mechanical framework for a homogeneous and isotropic universe governed by Bumblebee
gravity, in which spontaneous Lorentz
symmetry breaking is triggered by a vector field acquiring a
vacuum expectation value (VEV). Starting from the full four-dimensional covariant action, the derivation has been carried out for the one-dimensional mini-superspace Lagrangian density for a flat Friedmann-Lemaître-Robertson-Walker (FLRW) background with a purely temporal bumblebee field configuration. Further, the work focuses on to construct the classical
Hamiltonian system through a canonical Legendre transformation, identifying the lapse function $N(t)$ as a Lagrange multiplier enforcing a primary
Hamiltonian constraint. Apart form that, the conservation of phase-space volume via Liouville's
theorem, locate and classify the critical points of the resulting dynamical system, and examine the stability of the Lorentz-violating
vacuum has been carried to test the classical
Hamiltonian system in the work. Furthermore, the modified first and second Friedmann equations and discuss the resulting time-dependence of the effective gravitational coupling, illustrating the results with numerical phase-space has been discussed in this work. Finally, the work extended to construct the Wheeler-DeWitt equation through the canonical quantization and obtain the approximate solutions in the deep-
quantum ($a\to0$) and near-
vacuum regimes for it.
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Materials Science
Imaging Gate-Tunable Single-Layer Molecular Kagome Lattices
Ziyi Wang, Rafal Zuzak, Weichen Tang et al. (+11 more)
Kagome
lattices provide a simple geometry for engineering electronic states that exhibit novel
quantum behavior. In conventional kagome materials, however, the relevant states are often embedded in chemically complex three-dimensional
crystals and are difficult to isolate or tune. Molecule-based kagome networks offer structural precision and tunability, but have largely been confined to metallic substrates incompatible with 2D devices. Here we report growth of single-layer Ni$_3$(HITP)$_2$ metal-organic frameworks (MOFs) on van der Waals substrates including
graphene-based field-effect devices using metal-salt molecular beam epitaxy. Low-temperature scanning tunneling spectroscopy resolves kagome-derived flat-band and van Hove singularity-based spectral features consistent with first-principles calculations. Gating hybrid 2D MOF devices allows us to energetically shift kagome spectral features, thus establishing electrostatic control of chemically programmable 2D kagome electronic
lattices.
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All authors Ziyi Wang, Rafal Zuzak, Weichen Tang, Haowen Pang, Yutang Qiao, Dhanvanth Balakrishnan, Yuqiao Yan, Aining Hu, Andrew Sun, Takashi Taniguchi, Kenji Watanabe, Feng Wang, Steven G. Louie, Michael F. Crommie
General Relativity and Quantum Cosmology
Dynamical stability and observational constraints on a late-time dark-matter particle-creation model
Anirban Chatterjee
We investigate the cosmological dynamics of gravitational particle creation in a spatially flat FLRW Universe comprising radiation, baryons, dark matter (DM), and a separately conserved dark-energy component. The DM sector is described as an effective open thermodynamic fluid incorporating intrinsic pressure and particle-creation-induced negative pressure. Introducing the compact variable $u=H_0/(H_0+H)$, we construct a four-dimensional autonomous system and systematically investigate its critical points, dynamical stability, and physical admissibility. The model is constrained using three observational combinations: PPS+BAO+OHD, Union3+BAO+OHD, and DES-DOV+BAO+OHD. The observationally preferred parameter regions exclude the nontrivial DM-dominated de Sitter-like branches from the physical phase space, while identifying a stable, physically admissible, dark-energy-dominated accelerating attractor. The reconstructed cosmological
evolution consistently reproduces the radiation–matter–acceleration sequence, with a transition
redshift $z_{\rm tr}\simeq0.71$–$0.73$. Posterior-level analysis reveals that approximately $92\%$–$97\%$ of the samples support this accelerating attractor. The asymptotic
evolution approaches a quintessence-like power-law expansion with $H\rightarrow0$, rather than a de Sitter state. These findings establish a connection between observational constraints, gravitational particle creation, and the global dynamical structure governing the distant
cosmic future.
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Quantum Gases
Phases of a rotating Bose-Einstein condensate trapped in a hard-wall potential
Hélène Perrin and G. M. Kavoulakis
We investigate the rotational properties of a zero-temperature Bose-Einstein condensed gas, which is confined in a hard-wall potential. For weak interactions the gas carries its angular momentum via
vortices of multiple quantization. As the coupling increases and for sufficiently slow rotational frequencies of the trap, the multiply-quantized
vortex states become unstable against a mixed state. For stronger couplings, as the angular frequency of the trap increases, there is a transition from a
vortex lattice, to a
vortex lattice with a hole at the trap center, and finally to a giant
vortex. For weak effective attractive interactions we still have
vortices of multiple quantization. These states become unstable towards states which break the axial
symmetry of the problem and resemble center-of-mass excitation, as the coupling becomes more negative. Finally, for even more attractive forces, the system becomes unstable against collapse.
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Materials Science
Flexoelectricity and Flexomagnetism
Alexander Edström and Massimiliano Stengel
Strain gradients, unlike homogeneous strain, are odd under space inversion and unlock couplings that are strictly forbidden in the parent
crystal. At the nanoscale, and in curved low-dimensional systems in particular, such gradients are readily attainable and often unavoidable, so that
curvature acts as a
symmetry-breaking field written into the
lattice itself. This chapter reviews the resulting couplings to electric polarization and magnetism. After establishing the
geometric relation between strain gradients and
curvature, we review flexoelectricity as the better-established reference case: the bulk, surface and dynamic contributions that complicate its definition, its microscopic mechanisms, its manifestation in two-dimensional materials, and the first-principles methodology now available for its calculation. Using the magnetoelectric effect as a conceptual bridge, we then develop flexomagnetism in a broad sense, covering any coupling phenomena between magnetism and strain gradients, and specifically discuss the linear magnetization response to
curvature and
curvature-induced Dzyaloshinskii-Moriya interactions, beyond the established curvilinear treatment. Finally, we briefly describe some additional effects fitting under this broad umbrella of flexomagnetism, including nonlinear ones, inhomogeneous magnetoelectric and Rashba-type phenomena, and connections to altermagnetism.
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General Relativity and Quantum Cosmology
Linear Response to Black Hole Deformations
Stefan Hohenegger
Modifications of
gravity beyond (
vacuum) General Relativity have a subtle impact on the physics around black holes. Describing these effects across different observables is, however, a priori strongly model dependent. While effective descriptions of the geometry allow to efficiently capture deviations from
benchmark predictions, they sometimes lack a clear passage towards (effective) new physics. Inspired by linear response theory, in this work I therefore propose a formalism that allows to calculate leading corrections of observables relative to the Schwarzschild black hole anywhere in space-time (outside of the horizon): the order of corrections is fixed through an
eigenvalue $\mathcal{E}$ of the Einstein tensor, which is identified with an external energy momentum tensor that generates the deformation of the geometry. In this ways, $\mathcal{E}$ can be linked to effective physics models. Focusing on spherically symmetric and static black holes, I illustrate the approach at the hand of a number of observables in the vicinity of the horizon, such as characteristic quantities of particles moving around the black hole (e.g. the black hole shadow or the radius of the innermost stable circular orbit) or the spectrum of scalar quasi-normal modes. Reversing the logic, I argue that the knowledge of such observables provides non-trivial constraints on $\mathcal{E}$, which in turn grant insights into the effective physics in the vicinity of the black hole.
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Optics
Continuous-wave 148.4 nm Generation in Quasi-phase Matched BaMgF4
Yuanzhuang Bu, Xiangting Wang, Ruiyin Gu et al. (+6 more)
We report continuous-wave (CW)
vacuum-ultraviolet (VUV) generation at 148.4 nm by second-harmonic generation of 296.8-nm fundamental light in quasi-phase matched (QPM) BaMgF4 (BMF). At the incident power of 170 mW, a VUV output power of approximately 31 pW can be obtained. The quadratic dependence of the signal on the incident power in the QPM region and its attenuation in the ambient environment support the identification of VUV generation. The polarization dependence shows a sine-function shape with a 15% output attenuation from the maximum to the minimum. These results highlight the potential of BMF as a nonlinear medium for CW VUV generation.
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All authors Yuanzhuang Bu, Xiangting Wang, Ruiyin Gu, Chongtai Liu, Luxin Jiang, Xinqing Ding, Ke Zhang, Yongkai Li, Kemi Xu
Mathematical Physics
Haagerup-Izumi modular data from hyperbolic words: S-fold TQFTs, central charge, torsion and the Bethe vacua
David E Evans
The modular data of the doubles of the Haagerup–Izumi categories is a grafting of two finite metric groups (conjectured by Evans–Gannon, proved for untwisted categories by Gannon–Schopieray–Yadav). Gang and Kim found non-
unitary modular data of this shape in the topological twist of rank-$0$ $S$-fold theories, from the Bethe
vacua of an abelianised gauge theory. The aim is to understand rigorously the significance of the handle-gluing and fibering operators, and to construct the Bethe
vacua. For every
hyperbolic once-punctured-
torus monodromy $\varphi$, a word in $L$ and $R$, the two groups are $A_\mp=\coker(\varphi\mp1)$, with the torsion linking forms of the mapping
tori of $\varphi$ and $-\varphi$. Over all words of trace $m^2+2$ these forms reproduce the Evans–Gannon table of Q-systems, one printed entry being corrected, and the distinct modular data in the list of Gannon–Schopieray–Yadav. The Bethe data are given in closed form by the word: the level
matrix, the positive
vacuum, $c_{\eff}=\#L$, and the handle-gluing values $2^{\#L}\lambda^{\pm1}|A_-||A_+|$ at the identity classes, $\lambda$ the stretch factor. Each kernel vector of $\varphi\mp1$ modulo $|A_\mp|$ at which an explicit trigonometric formula does not vanish gives a solution of the Bethe equations in closed form. Under the half-index dictionary, with the unit in the class of $\sigma V^*$, $c\equiv\#L-6\#R\pmod{24}$.
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Solar and Stellar Astrophysics
Star spots mimic the proposed abundance signatures of planet formation
Andrew R. Casey, Megan Bedell, Adam Wheeler et al. (+2 more)
Trends with stellar elemental abundances and condensation temperature have been proposed as a possible tracer of rocky
planet formation. Here we present an alternative explanation, where we show that stellar activity (
star spots) can also cause apparent abundance changes in refractory elements preferentially over volatile elements. This effect arises naturally from atomic physics: refractory (rocky; high-$T_c$) elements preferentially have low first-ionization potentials, with strong transitions that are most sensitive to the cooler, magnetically-perturbed spot conditions, making any spot-induced change in line strength correlated with $T_c$. We re-examine literature on Sun-like
stars in the Solar neighborhood and find that the $\log{R'_{HK}}$ stellar activity indicator is correlated with the so-called $T_c$ slope: the gradient of chemical abundances with respect to condensation temperature. Using 1D LTE Korg.jl simulations of the Sun with spots of varying size and contrast, we show that a wide range of spot configurations can manifest as abundance patterns that mimic a signal of abundance trends with condensation temperature. Finally, we conduct a line-by-line differential analysis of an ambient Solar spectrum relative to a Solar sunspot umbra to represent an extreme case, where we find that elements with high condensation temperature can show a factor of three (0.5 dex) increase. We discuss implications that stellar activity poses for precision spectroscopy, and provide some direction on how this effect might be mitigated.
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All authors Andrew R. Casey, Megan Bedell, Adam Wheeler, Julianne Dalcanton, Lily Zhao