Strongly Correlated Electrons
Dynamical signatures of deconfined spinons in dimerized sawtooth chains
Nishan Ranabhat, Brandon B. Le, Seung-Hun Lee et al. (+1 more)
We study the ground-state properties and dynamical response of the Heisenberg model on the sawtooth chain in and away from the exactly solvable valence-bond-solid (VBS) point. We employ U(1)-symmetric density-
matrix renormalization group (DMRG) and time-dependent variational principle (TDVP) methods to compute
equilibrium diagnostics and the zero-temperature dynamical structure factor (DSF) $S^{zz}(q,\omega)$ across the dimerized phase, a valence-bond-ordered state in which the two
symmetry-equivalent apex–base bonds of each triangle develop unequal
spin correlations, probing the approach to the continuous lower phase boundary, the exact VBS point, and the approach to the first-order upper boundary. In every regime, the DSF is a broad continuum dominated by a bright band at its lower edge, with the intensity at the one-triplon energy $\omega \simeq J_{AB}$ suppressed. We identify the spectrum as a deconfined two-spinon continuum of kink and antikink domain walls between the two degenerate singlet coverings. Closed-form spinon dispersions fix the continuum edges and track the dominant band across the zone in all three regimes, while an explicit finite-separation two-kink calculation in a constrained
Hilbert space reproduces the measured intensity distribution. Our results provide a microscopic picture of fractionalized excitations in the dimerized sawtooth chain and are relevant to the recently discovered Ti$^{3+}$ kagome fluorides, where strongly anisotropic exchange interactions can generate sawtooth-chain building blocks.
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All authors Nishan Ranabhat, Brandon B. Le, Seung-Hun Lee, Gia-Wei Chern
Nuclear Theory
Single-particle potentials in asymmetric nuclear matter within the LOCV framework
Zahra Ziarati and Hamidreza Moshfegh
The single-particle potentials and effective masses of
protons and
neutrons in asymmetric
nuclear matter are investigated within the lowest-order constrained variational (LOCV) method. The dependence of these quantities on momentum, density, and isospin asymmetry is studied using the $Reid68$ and $AV_{18}$ nucleon-nucleon interactions, with the effects of three-body forces also examined. The
neutron and
proton single-particle potentials exhibit a systematic splitting with increasing asymmetry, while their decomposition into different interaction channels identifies the dominant contributions to the in-medium interaction. The
symmetry potential decreases with increasing momentum and shows a pronounced dependence on density and three-body forces, particularly at low momentum. The
neutron-
proton effective-mass splitting increases with asymmetry, with the
neutron effective mass larger than the
proton effective mass. The calculated
symmetry potential is also compared with results from other microscopic and phenomenological approaches and with the empirically constrained Lane potential, showing a consistent decreasing trend with increasing kinetic energy. These results provide a microscopic, state-dependent single-particle potential for asymmetric
nuclear matter, with its momentum, density, and asymmetry dependence determined directly from the underlying two and three-body interactions.
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Mesoscale and Nanoscale Physics
Majorana signatures in an asymmetrically coupled quantum dot–topological superconducting nanowire junction
Levente Máthé, Ioan Grosu, Liviu P. Zârbo et al. (+1 more)
We present a theoretical study of the
quantum transport through a nanoscale system in which a central
quantum dot (QD) is coupled asymmetrically to normal leads and to two Majorana bound states (MBSs) localized at the ends of a topological superconducting nanowire threaded by a tunable
magnetic flux. The effects of the leads–QD coupling asymmetry parameter $\alpha$ and the bias voltage asymmetry parameter $q$ on the system's linear conductance are considered for the case of unhybridized and hybridized MBSs. In the zero-temperature limit, for unhybridized MBSs the system's linear conductance is finite only when the
magnetic flux phase $\phi = (2n+1)\pi$ ($n\in\mathbb{Z}$) and it scales as $\mathcal{G}=2q\alpha e^2/[h(\alpha+1)]$, while for hybridized MBSs it presents a complicated dependence on the system's parameters. At finite temperature, for unhybridized MBSs, the system's linear conductance oscillates as a function of the
magnetic flux phase $\phi$ with a period of $2\pi$, and the position of the linear conductance maxima can be shifted from $\phi=2n\pi$ to $\phi=(2n+1)\pi$ by simply varying the value of the bias voltage asymmetry parameter $q$. For hybridized MBSs, the conductance exhibits a similar behavior when the energy level of the central QD, $\varepsilon_d$, is tuned at the leads'
Fermi level ($\varepsilon_d=\varepsilon_F$), although when $\varepsilon_d\neq\varepsilon_F$ the oscillation period changes to $4\pi$, and the position of the linear conductance maxima depends on the actual value of $\varepsilon_d$ and other parameters in the system. Our results highlight the experimental importance of the leads-QD and bias voltage asymmetry parameters, which are often present in realistic experimental setups, and can strongly affect the identification and observation of MBSs transport signatures.
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All authors Levente Máthé, Ioan Grosu, Liviu P. Zârbo, Ionel Ţifrea
Fluid Dynamics
Variational Acoustics
Md Mahmudur Rahman and Ivan C. Christov
Many variational principles for acoustics have appeared in the literature, often introduced in an ad hoc manner by picking and choosing terms in a Lagrangian density to yield a desired governing partial differential equation. In this chapter, we show that such guesswork is unnecessary, as the governing equations of acoustics can be derived systematically from the primitive Lagrangians of classical continuum mechanics. Furthermore, we note that using Eulerian coordinates is not the only way to derive variational principles in acoustics. To this end, we review the construction of an action in the Lagrangian frame for compressible nondissipative fluids. We explore the consequences of material relabeling
symmetry and the associated pseudomomentum balance, together with the boundary and jump conditions it implies. Via perturbation expansions, we show how to recover the equations of linear acoustics from each variational principle, the material frame yielding in addition the second-order acoustic energy balance. We show how weakly nonlinear approximations with variational structure emerge in each frame, in both cases for a general barotropic fluid, with the nonlinearity carried by the fluid's parameter $B/A$ and the perfect-gas results recovered as a special case.
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Statistical Mechanics
Information-theoretic formulation of the Traveling Salesman Problem
Enrico Maria Fenoaltea, Riccardo Piombo and Aurelio Patelli
The Traveling Salesman Problem (TSP) asks for the shortest route to visit a set of cities exactly once. It combines a simple local rule - each city must be visited once - with a hard, global constraint- all cities must be traversed within a single cycle. We cast the problem within a probabilistic, information-theoretic framework. The coexistence of local and global constraints is precisely what makes the problem difficult to address in this framework: the local rule can be enforced through vertex-level constraints, whereas the global constraint cannot be captured by independent edge probabilities. We show that this obstacle can be overcome by defining a maximum-
entropy probability distribution over graphs, in which edge costs and degree constraints generate an assignment-like ensemble, and a global term, describing the hard constraint, tilts this ensemble toward
Hamiltonian cycles. To make the construction tractable, we derive a mean-field approximation in terms of edge occupancies and implement a differentiable cycle penalty that suppresses sub-tours. This leads to a self-consistent numerical procedure whose output is not only a candidate tour but also a probability
matrix encoding competing edges and degenerate solutions. We test the method on synthetic ensembles and on TSPLIB instances. The
algorithm converges to connected tours in
polynomial time, matching the best-known solution in the majority of instances and remaining within a small relative gap otherwise. Beyond its competitive performance, the proposed framework offers a general approach for handling hard constraints while reducing hard combinatorial optimization problems to simpler ones.
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High Energy Physics (Theory)
Vortex-Antivortex Annihilation from BPS Equations
J. P. S. Neto, J. G. F. Campos and A. Mohammadi
In this work, we introduce a
vortex-
impurity model that admits BPS configurations containing both
vortices and antivortices and allows
vortex-antivortex annihilation to be described within the
moduli-space approximation. For a suitable class of
impurities, the BPS equations can be mapped through a coordinate transformation onto those of the
impurity-free Abelian-
Higgs model. In particular, we identify nonlocalized
impurities that act as mirrors, generating a
vortex-antivortex pair symmetrically placed with respect to the
impurity. We derive the corresponding
moduli-space metric and show that, within the geodesic approximation, the pair approaches the annihilation configuration asymptotically. We further extend the construction to chains and two-dimensional arrays of alternating
vortices and antivortices. Finally, we introduce radial bump
impurities that produce stretched and compressed
vortices with nontrivial internal
magnetic structures.
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Cosmology and Nongalactic Astrophysics
HOLISMOKES – XVIII. Cosmology with strongly lensed type II supernovae: Effects of instrumental setups on $H_0$
J. Grupa, S. Taubenberger, S. H. Suyu et al. (+3 more)
The upcoming Rubin Observatory and subsequent follow-up observations should improve the determination of the Hubble constant ($H_0$) via time-delay cosmography of strongly lensed type II
supernovae (LSNe II), by enabling the detection of many more such events. In our previous work, we developed a method for determining the
supernova (SN) phase from spectral absorption features. Because obtaining spectra of faint targets such as distant SN II is expensive, we examined how low-resolution spectra influence the precision of time-delay
retrieval, and consequently the precision on $H_0$. We considered spectral resolutions $R = \frac{\lambda}{\Delta \lambda}$ between 100 and 250, and we investigated three signal-to-noise ratio ($S/N$) values of 10, 15, and 20, for each resolution. Furthermore, we forecast the precision on $H_{0}$ achievable with $S/N=10$ and compared the observing time required to reach it with ground-based and space-based facilities. We find that the time delay can be determined without bias and with uncertainties as low as 1.3 days for the investigated resolutions and $S/N$ values when we combine time-delay measurements of multiple absorption lines. For a typical LSN II system (absolute magnitude $\sim-$17 mag in the rest-frame V band, source
redshift of \zs = 0.8), the required exposure times range from multiple hours for ground-based observations to a few minutes for space-based observations with the JWST. Our predictions on the precision of $H_0$ for a single lensed SN range from 14.2% for $R = 100$ and $S/N$ = 10 to 7.5% for $R = 250$ and $S/N$ = 20, enabling a 1% determination of $H_0$ from $\sim$20 lensed SNe in the coming years.
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All authors J. Grupa, S. Taubenberger, S. H. Suyu, D. Sluse, S. Huber, C. Vogl
Medical Physics
Adapting the TG-43 formalism for use in Diffusing alpha-emitters Radiation Therapy
Guy Heger, Lior Epstein and Lior Arazi
Background: Diffusing alpha-emitters Radiation Therapy ("Alpha DaRT") enables the treatment of solid tumors using alpha particles. In Alpha DaRT, the tumor dose distribution is mainly dictated by the
diffusion of the decay products of $^{224}$Ra. Due to the inherently different mechanism of dose delivery of the Alpha-DaRT source compared to sources emitting only electrons or
photons, the conventional formalism of TG-43 cannot be directly applied to Alpha DaRT. Purpose: To adapt the TG-43 formalism to be used with the Alpha-DaRT model, with the specific aim of allowing commercial treatment-planning software packages to be used for Alpha-DaRT treatment planning. Methods: The effective dose rate is defined, along with an activity conversion factor. These, together with a numerical calculation that solves the model equations, allow implementing the Alpha-DaRT model predictions into the TG-43 formalism. Results: An example of calculated $F(r, \theta)$ and $g_L(r)$ tables is presented for an Alpha-DaRT treatment scenario, with the model parameters representing preclinical data on squamous
cell carcinoma. Conclusions: Commercial software can be used for Alpha-DaRT treatment planning. However, the generated $F(r, \theta)$ and $g_L(r)$ tables depend on tissue parameters, as well as treatment duration, and so these tables should be generated on a case-by-case basis.
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Instrumentation and Methods for Astrophysics
RadialPaths: Radial profiles in multi-centred astronomical structures
Rafael S. de Souza
Radial profiles are routinely used to locate structural changes within resolved astronomical systems, but they generally define radial position relative to a single centre. In interacting, clumpy, or otherwise multi-centred structures, the radial location assigned to a feature can depend on the adopted centre. We introduce a centre-conditioned radial representation for connected structures with multiple centres. Distances are measured through the observed source footprint rather than across excluded background, and can be viewed as arrival times of fronts propagating from the centres. Each location is associated with the centre reached first and described by two complementary coordinates: relative centre–boundary depth and normalized progression away from that centre. For an ideal centred circular source, both reduce exactly to the familiar normalized radius $r/R$; in folded, elongated, or tailed geometries they separate because proximity to a lateral boundary and progression through the structure represent different notions of “outward”. Synthetic examples show that single-centre and equivalent-area radial descriptions do not retain the association between localized features and individual centres, whereas centre-conditioned profiles do. In two JADES DR2 systems, the resulting F277W profiles remain stable under modest changes in the adopted source footprint and one-pixel centre shifts. The construction assumes neither a light-profile law nor an overlapping flux decomposition, and the same radial geometry can be applied to registered maps of continuum light, colour, emission lines,
stellar-population properties, and line-of-sight kinematics. An accompanying Python package, RadialPaths, provides the reference implementation together with documentation and online tutorials at \href{https://rafaelsdesouza.com.br/radialpaths} {GitHub}.
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Adaptation and Self-Organizing Systems
Mixed-mode bursting oscillations in a three-timescale biophysical neuronal oscillator model
Ngoc Anh Phan and Yangyang Wang
Mixed-mode oscillations (MMOs), characterized by the alternation of small-amplitude oscillations (SAOs) and large-amplitude oscillations (LAOs), and bursting oscillations are common forms of complex oscillatory dynamics observed in systems with multiple timescales and have been widely studied across scientific disciplines. Mixed-mode bursting oscillations (MMBOs) combine features of MMOs and bursting, with LAOs organized into burst events. Most existing studies treat MMBOs as two-timescale phenomena, identifying distinct
geometric mechanisms depending on how the timescales are grouped. In this work, we use a three-timescale biophysical cortical neuronal oscillator model to demonstrate that a three-timescale implementation of
geometric singular perturbation theory (GSPT) provides stronger predictive insight into MMBO dynamics. This perspective unifies mechanisms previously identified from fast-slow analysis, while revealing the canard-delayed-
Hopf (CDH) singularity as an organizing center for MMBOs near the singular limit. We perform a detailed bifurcation analysis of the full eight-dimensional model to determine how MMBOs are organized along families of isolas. We then combine GSPT with full-system bifurcation analysis to show how tuning the relative timescales induces transitions among MMOs, MMBOs, and bursting dynamics. Our results highlight the importance of studying MMBOs from a three-timescale perspective and demonstrate that combining GSPT with full-system bifurcation analysis can reveal organizing structures and mechanisms that are not apparent from either approach alone.
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Instrumentation and Methods for Astrophysics
The MegaWave Radio Surveyor
T. Joseph W. Lazio, Evgenya Shkolnik, James Aguirre et al. (+40 more)
Several Decadal-level questions in astrophysics,
exoplanets, astrobiology, and cosmology can be addressed only at low
radio frequencies inaccessible from Earth. The MegaWave
Radio Surveyor would open this largely-unexplored region of the electromagnetic spectrum with a space-based interferometer to (1)~Track the space weather of other
stars; (2)~Detect magnetically-generated emission from
exoplanets to probe their interiors and assess
magnetic shielding of their atmospheres; (3)~Probe the Universe's
evolution during the Dark Ages via the highly-redshifted HI hyperfine line; and (4)~Assess the role of
cosmic rays and
magnetic fields in the
cosmic web. An Astrophysics Strategic Technology & Research Accelerator (ASTRA) Initiative concept, the MegaWave
Radio Surveyor's science objectives respond to the Pathways to Discovery Decadal Survey and three other National Academies studies, and it would serve as a Formative Era mission in the Enduring Quests, Daring
Visions roadmap. Developments in U.S. space industries enable this observatory to be realized. The MegaWave
Radio Surveyor would offer a versatile, scalable, and resilient architecture capable of sensitive and simultaneous observations below 45~MHz and unprecedented angular resolution at these frequencies. The concept builds upon NASA's Sun
Radio Interferometer Space Experiment (SunRISE),
Star-
Planet Activity Research CubeSat (SPARCS), and Lunar Surface Electromagnetics Experiment (LuSEE-Night). The MegaWave
Radio Surveyor could leverage multiple elements of the Artemis program, such as access to and beyond cislunar space and communications, and there are opportunities to infuse new autonomy/AI modes for mission operations. By opening one of the last windows in the electromagnetic spectrum and pioneering space interferometry at unprecedented scales, the MegaWave
Radio Surveyor would establish a transformational capability.
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All authors T. Joseph W. Lazio, Evgenya Shkolnik, James Aguirre, Stuart D. Bale, Judd Bowman, Ruby Byrne, Joseph Callingham, Tracy E. Clarke, Ivey Davis, Tim Dolch, Peter Driscoll, Anastasia Fialkov, Steven Furlanetto, Simona Giacintucci, Ravit Helled, Jacqueline Hewitt, Phil Hopkins, Andrea Isella, Daniel Jacobs, Eloy de Lera Acedo, Melodie M. Kao, Mary Knapp, L.V.E. Koopmans, Nicholas Kern, Jasmina Lazendic-Galloway, Susan T. Lepri, R. O. Parke Loyd, James P. Lux, James P. Mason, Raul Monsalve, Miguel Morales, Julian B. Muñoz, Rachel Osten, J. Sebastian Pineda, Jonathan Pober, Sam B. Ponnada, Leslie A. Rogers, Saurabh Singh, Jake D. Turner, Jackie Villadsen, Philippe Zarka, John ZuHorne, Ellen Zweibel
Earth and Planetary Astrophysics
Non-equilibrium condensation of the first Solar System solids
Sebastien Charnoz, Jérome Aleon, Marc Chaussidon et al. (+3 more)
Primitive meteorites (chondrites) consist of an out-of-
equilibrium assemblage of minerals formed during the assembling of our
Solar Nebula. The conditions under which their precursors condensed remain unclear as a result of subsequent re-processing in the protoplanetary disk or in asteroidal parent bodies. Chondrites are classified into three main classes enstatite (EC), ordinary (OC), and carbonaceous (CC) distinguished by different bulk composition and oxidation state. While
equilibrium condensation models explain the composition of some of their refractory components they do not explain the emergence of three mineralogical classes. Moreover, the low pressures, steep temperature gradients, and short dynamical transport timescales in forming protoplanetary disks likely hindered
equilibrium. Here we test the hypothesis that chondrite precursors formed via kinetic non-
equilibrium condensation. Using a new time-dependent condensation model, we show that varying the cooling rate and pressure produce only three types of mineralogies. Departure from
equilibrium yields increasingly oxidized and hydrous mineralogies. When projected into a Urey-Craig diagram, the predicted mineralogical types fall close to the redox states of EC, OC, and CC chondrites. These results suggest that the mineralogical diversity of chondrites may reflect, in part, local condensation kinetics, offering an alternative to large-scale variations of oxidation conditions.
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All authors Sebastien Charnoz, Jérome Aleon, Marc Chaussidon, Paolo Sossi, Yves Marrocchi, Patrick Franco
Quantum Physics
Exploiting overcompleteness of Platonic-solid POVMs for shadow estimation
Dario Melegari, Stefano Mangini, Keijo Korhonen et al. (+2 more)
Accurately estimating expectation values of observables from a finite number of measurement shots is a central challenge in
quantum information science. Informationally overcomplete measurements provide a route to reduce estimation variance through optimized classical post-processing. However, the interplay between measurement geometry and dual-frame construction remains largely unexplored. In this work, we study Platonic solid POVMs —highly symmetric, overcomplete single-
qubit measurements whose effects correspond to the vertices of the five Platonic solids on the Bloch sphere— for the estimation of molecular
Hamiltonians. Using $k$-locally optimal dual frames, we show that the geometry of the POVM can have a non-trivial and non-monotonic effect on the estimation variance. We further propose a joint optimization of the POVM orientation and effect weights using a classical proxy state, either a product state or a
Matrix Product State (MPS) approximation. We demonstrate that optimized Platonic solid POVMs can outperform standard randomized Pauli measurements, provided the MPS bond dimension is sufficient to faithfully represent the target state. These results reveal a trade-off between classical preprocessing and estimation accuracy, suggesting a practical route to improved observable estimation on near-term
quantum hardware.
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All authors Dario Melegari, Stefano Mangini, Keijo Korhonen, Hetta Vappula, Daniel Cavalcanti
Solar and Stellar Astrophysics
Active nests at solar maximum: How nested flux emergence dominated flaring activity and structured the heliosphere
Adam J. Finley, Allan Sacha Brun, Antoine Strugarek et al. (+5 more)
Multi-viewpoint observations from near-Earth satellites and ESA's
Solar Orbiter enable a global view of the Sun. This continuous coverage is essential for characterising active nests. We investigated how the formation of active nests during the maximum of
solar cycle 25 affected the Sun's flaring activity and large-scale
magnetic field. Active nests were identified from their persistent activity in Carrington coordinates. For each nest, we monitored the
evolution of their photospheric
magnetic field, extreme ultraviolet emission, and associated
solar flares. Their impact on the
solar corona was explored through potential field source surface extrapolations and coronagraph observations. These results were then compared with in-situ measurements of
solar wind speed and
magnetic field polarity. During 156 days of global monitoring in 2024, nearly 80% of all
solar flares originated from three active nests in the southern hemisphere. Two of the nests converged over several months, colliding with a burst of activity in October 2024. The third nest was linked to the emergence of NOAA active region AR13664 in May 2024. Magnetically complex NOAA active regions were more prevalent within active nests. During 2024, 28% of the 147 nested active regions were complex, compared to just 16% of the 181 regions elsewhere. In January 2025, two active nests emerged from the collision site, and a new active nest appeared in the north. This reinforced a tilted dipole
topology throughout 2025. Active nests modulated global
solar activity in 2024 and shaped the
solar corona and wind in 2025. Nearly continuous tracking was used to isolate their flaring and flux emergence rates. Active nest migration was driven by the emergence of
magnetic flux, implying a coherent sub-surface origin. By anchoring the coronal
magnetic field, active nests created more favourable source regions for
solar wind connectivity studies.
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All authors Adam J. Finley, Allan Sacha Brun, Antoine Strugarek, Barbara Perri, Daniel Müller, Miho Janvier, Andy S H To, Henrik Eklund
High Energy Physics (Phenomenology)
Enhancement of nonlinear pair production in a flying-focus pulse
Md Reshad Ur Rahman, Martin S. Formanek, Elias Gerstmayr et al. (+3 more)
A
photon can decay into an electron-positron pair in the presence of an intense
laser pulse by a process known as nonlinear Breit-Wheeler pair production (NBWPP). For a sufficiently intense pulse, the probability of NBWPP for a high-energy gamma
photon scales more favorably with the interaction time than with the field intensity. In contrast to typical stationary-focus Gaussian (SFG)
laser pulses, a flying-focus (FF) pulse features a focal point that moves at a programmable velocity. Here, we show that a FF pulse counterpropagating with a high-energy
photon beam while its focus copropagates with the beam at the speed of light enhances the NBWPP yield relative to an equal-energy SFG pulse. Numerical simulations show that a Joule-class tightly-focused FF pulse allows for an enhancement of the pair-production yield by 12%, 29% and 76% for a
photon of 10, 20 and 50 GeV energy, respectively. Thus, in this regime, FF pulses are more efficient at producing electron-positron pairs than conventional SFG pulses.
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All authors Md Reshad Ur Rahman, Martin S. Formanek, Elias Gerstmayr, Dillon Ramsey, John P. Palastro, Antonino Di Piazza
Materials Science
Milled to order: toward predictive mechanochemistry of halide perovskites
Susan A. Rigter and Loreta A. Muscarella
Mechanochemical milling is regarded as a scalable, solvent-free method that makes halide perovskites that solution processing cannot. Its deeper promise, though, is that mechanical force could become a new axis of synthetic control to turn milling from an empirical method into a predictive science. Halide perovskites are the ideal platform to establish this: their soft
lattices and low formation energies make them intrinsically responsive to mechanical activation. Realising this requires settling what milling actually makes, and how: can a milled phase genuinely be trapped outside
equilibrium, or is it just a convenient way to the
equilibrium phase, and by what atomistic pathway does it work? These questions are mostly answered by assumption, while the in-situ and computational tools that resolved them for other material classes already exist. Closing this gap will unlock two design capabilities: mechanical energy used as a synthetic variable to tune phase selection, and metastability made programmable, producing trapped phases, specific intermediates, and compositions that have no possible solution route. Finally, two tests decide whether that control reaches practice: the state engineered during milling must survive into a working device, and the method must prove genuinely greener across the full device life cycle, rather than just solvent-free.
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Biological Physics
Retrievable but Unencountered: The Missing Exposure Denominator in Large Academic Ebook Collections
Jette Veenstra and Mauricio Munoz Arias
Academic libraries hold ebook collections so large that no reader can inspect more than a negligible fraction of the catalogue. Assessment of those collections rests almost entirely on usage telemetry. A title that generates no recorded interaction is treated as a title nobody wanted. That inference is unavailable on the present evidence. We separate two constructs the literature conflates: retrievability, the probability that a system returns an item to a query that already specifies it, and encounterability, the probability that an item enters a reader's
attention without prior title-level intent. Following a stated protocol over work published from 2018 onward, we find three things. Large zero-use populations are robustly documented. Usage depends heavily on the measuring instrument. And no standard library metric records an item impression. The consequence is an identification problem. Recorded non-use mixes non-exposure, unnoticed exposure, rejection, and off-channel use, and no study located under our protocol decomposes it. Recommender-system research already names this problem: there, feedback is missing not at random. We close with four measurement directions that would narrow the gap without closing it.
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Cosmology and Nongalactic Astrophysics
The Impact of Magnitude Uncertainties and K-corrections on Standard Siren Measurements of the Hubble Constant
M. Pálfi and P. Raffai
Gravitational-wave standard sirens provide an independent probe of the Hubble constant. Dark siren analyses that rely on
galaxy catalogues are sensitive to catalogue-related uncertainties. While incompleteness, weighting schemes, and
redshift errors have been studied extensively, the impact of magnitude uncertainties and K-corrections has received little
attention so far. We assess how magnitude errors and K-corrections propagate into the Hubble constant inference, and compare their impact to that of realistic spectroscopic
redshift errors to determine their relevance. We use a modified version of the gwcosmo Python package to construct line-of-sight
redshift priors from a complete, volume-limited mock
galaxy catalogue up to $z<0.2$. We simulate and analyse a sample of $\sim200$ binary black hole events with luminosity weighting in the $B$- and $K$-bands and test different uncertainty models for
redshifts, magnitudes, and K-corrections. The choice of luminosity-weighting scheme has a substantial impact on the inferred Hubble constant posterior, with the direct $B$- and $K$-band comparison producing differences comparable to the largest uncertainty-induced changes. Spectroscopic
redshift errors produce the largest integrated changes in the Hubble constant posterior among the tested uncertainty treatments. Photometric magnitude uncertainties lead to substantially smaller, band-dependent deviations. In the $K$-band, the tested K-correction treatments have only a minor impact in the present low-
redshift mock analysis, with the empirical correction slightly reducing the integrated deviation relative to the no-correction case. In realistic, flux-limited catalogues with larger localization areas and photometric or mixed
redshift errors, the relative impact of magnitude uncertainties is expected to be even smaller, indicating that they need not be prioritized in near-future dark siren analyses.
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Physics and Society
District-Level Food Environment Indicators and Social Vulnerability in São Paulo
Pedro Lemes Sixel Lobo, Eric Tokuda, Kuruvilla Joseph Abraham et al. (+4 more)
Urban food environments may reflect broader socioeconomic inequalities, but district-level evidence remains limited in Brazilian cities. This study examined whether indicators of food retail and street-
market availability discriminate between levels of social vulnerability across the 96 districts of São Paulo. We conducted an exploratory cross-sectional ecological analysis integrating the São Paulo Social Vulnerability Index (IPVS), establishment records from the Relação Anual de Informações Sociais (RAIS), and street-
market data from CAISAN. Census-sector information was aggregated at the district level. Twenty districts without an IPVS classification were excluded, resulting in 76 observations. The outcome distinguished districts classified as IPVS level 1 from those classified as levels 2–7. Predictors described the densities of healthy and unhealthy food establishments, the number of street
markets, and the availability of establishments selling fresh or in natura food. Eight conventional machine-learning classifiers were evaluated using leave-one-out cross-validation. Reported mean F-scores ranged from 0.62 to 0.75, with XGBoost obtaining the highest value. In the Random Forest model, the densities of healthy and unhealthy food establishments jointly accounted for approximately 60% of the total
impurity-based feature importance. These findings indicate that publicly available food-environment indicators contain information associated with the district-level distribution of social vulnerability. However, the small ecological sample, class imbalance, outcome binarization, and cross-sectional design limit predictive generalization and preclude causal or household-level interpretations.
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All authors Pedro Lemes Sixel Lobo, Eric Tokuda, Kuruvilla Joseph Abraham, Roberto Fray, Dirce Maria Marchioni, Alexandre Cláudio Botazzo Delbem, Rogerio Salvini
Optics
Moving forward with multilayer metastructures - simple design of complex optics
David A. B. Miller
I propose a simple and progressive way of designing and fabricating complex multilayered optics, even as we scale to large numbers of layers. The approach relies on successive layers of two-by-two blocks in which light only flows in the forward direction. It exploits a proposed trapezoidal architecture that can also support self-configuration in programmable structures, with the desired linear function or
matrix set up using input vectors that correspond to the
matrix rows, without any iteration other than successive single-parameter power maximizations. A key required component is a layer of 2 by 2 beamsplitters. The approach can support functions corresponding to a broad range of banded diagonal
matrices. Example applications include a camera that also measures phase gradients and the direct convolution of a line of inputs with a kernel based on wavelets.
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Fluid Dynamics
The bursting of hollow droplets
Alfonso M. Ganan-Calvo
A bubble bursting from a drop of finite size (a hollow droplet) is the generic bursting event in a breaking wave, yet it has been studied almost exclusively at unbounded baths. We follow it from the puncture of the film to the spectrum of a spray, in axisymmetric simulations over
liquid-to-gas volume ratios $\Lambda$ from $1/16$ to $512$ and Ohnesorge numbers from $0.005$ to $0.11$. Ejection ceases at $\mathit{Oh}_1=\mathit{Oh}_c(1+2\beta/\lambda)$, with $\beta\simeq0.83$ and $\lambda=(1+\Lambda)^{1/3}$: confinement extends ejection to bubbles too small to eject at a flat surface, and the distance $\delta=1-\mathit{Oh}/\mathit{Oh}_1$ to that boundary organizes everything that follows. The collapse, driven by capillary waves, is that of a gas thread pinching next to its mouth, whether the
liquid shell is punctured once or twice. The ejected volume is $M_e=C\,\delta\,V_{\rm red}$, with $C\simeq0.013$ and $V_{\rm red}=V_{\rm gas}V_{\rm liq}/(V_{\rm gas}+V_{\rm liq})$ a reduced volume. Whatever the confinement, the first droplet is smallest at $\delta\simeq0.2$ in units of the viscocapillary length $\ell_\mu=\mu^2/(\rho\sigma)$ and at $\delta\simeq0.3$ in units of the bubble radius $R_0$, where the unbounded bath also places its optimum. The largest reaches a tenth of $R_0$. Between them the census is exponential, with a scale set by $R_0$ and no lower cut-off: the smallest droplet a simulation records is set by its resolution, not by $\ell_\mu$, which belongs to the pinch singularity rather than to the droplets. Mixed over bubble populations, the census gives spray spectra in closed form, whose shape measures the population. The bursting also produces hollow droplets, each a potential new generator.
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Astrophysics of Galaxies
Phase-Space Diagnostics for Dwarf Galaxies in Cluster Environments
Anna Ivleva, Rhea-Silvia Remus, Klaus Dolag et al. (+3 more)
Ongoing effort is devoted to observing spectroscopic samples of
dwarf galaxies in clusters, allowing the analysis of their distribution and associated trends in projected phase-space (PPS), i.e. line-of-sight velocity vs. projected clustercentric distance. By utilizing the resolved baryonic
halos inside the
galaxy clusters of a cosmological simulation from the Magneticum suite, we complement on prior studies with dedicated focus on the
dwarf galaxy population ($M_\ast<10^9\,M_\odot$) and correlations between infall time and location in PPS. The inferred trend recovers the radial correlation reported by prior works, but we find a significant fraction ($\geq30\%$) of recently accreted
galaxies at locations that were previously predicted to be dominated by ancient infallers. Splitting the diagram with an infall time threshold of 3 Gyr, we develop a detailed infall time template in PPS. We provide our data to allow observers to statistically infer the time of infall of their sample when placing them on the PPS. Additionally, we review the trajectories in PPS of different orbits and their dependence on the observer's orientation. Compared to massive
galaxies, we find a much broader radial distribution for
dwarfs in 3D PS. Utilizing a set of high-resolution idealized simulations, we predict strongly altered orbits for dark matter-deficient
galaxies.
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All authors Anna Ivleva, Rhea-Silvia Remus, Klaus Dolag, Lucas M. Valenzuela, Jonah S. Gannon, Duncan A. Forbes
High Energy Astrophysical Phenomena
Synchrotron self-Compton Reverse Shock in Energy-Injection and Radiative Scenarios
Fraija Nissim, Betancourt-Kamenetskaia Boris, Galván Antonio et al. (+1 more)
Gamma-ray bursts (GRBs) are among the most energetic extragalactic transients, providing a unique laboratory to investigate the physical origin of the diverse morphologies observed in high-energy light curves and spectra. These morphologies, interpreted through synchrotron and synchrotron self-Compton (SSC) closure relations (CRs), may depend on the circumburst density profile, energy injection, and the dynamical
evolution of the reverse shock in the adiabatic or radiative regime. We derive the SSC closure relations produced in the reverse-shock region for both thick- and thin-shell cases, considering constant-density and stratified circumburst media. The analysis assumes two power-law (PL) distributions for the electron spectral index and includes scenarios with and without energy injection from the progenitor. We show that, depending on the physical parameters, SSC emission from the reverse shock can reproduce the initial steep-decay and plateau phases commonly observed in GRB afterglows. We then compare the predicted spectral and temporal indices with those derived from PL and broken power-law (BPL) fits reported in the Second
Fermi-LAT Gamma-ray Burst Catalog (2FLGC). Our results indicate that PL (BPL) light-curve fits preferentially favor scenarios with (without) energy injection. In scenarios with energy injection, the data preferentially support a constant-density environment over a
stellar-wind profile.
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All authors Fraija Nissim, Betancourt-Kamenetskaia Boris, Galván Antonio, Dainotti Maria Giovanna
Cosmology and Nongalactic Astrophysics
Paleo-Detectors as a Novel Probe of Dark Matter-Nucleus Effective Interactions
Dionysios P. Theodosopoulos
Paleo-detectors are a proposed approach to the direct detection of dark matter (DM) based on the observation of DM-induced
nuclear recoils. Rather than relying on large detector masses required for conventional detectors, paleo-detectors exploit extremely long integration times, using small samples of naturally occurring minerals that have resided deep underground and accumulated damage tracks over geological timescales of order a gigayear. In this contribution, we review recent theoretical predictions for the sensitivity of paleo-detectors to WIMP-
nucleus interactions within the framework of a Non-Relativistic Effective Field Theory (NREFT). We discuss both elastic and inelastic scattering processes and consider isoscalar couplings, taking into account backgrounds from
neutrinos and radiogenic sources. We present projected sensitivities of paleo-detectors for different readout and exposure scenarios and compare the reach of paleo-detectors to that of conventional direct-detection experiments. For DM masses in the range $1\ \mathrm{GeV}/c^2$-$10\ \mathrm{GeV}/c^2$, paleo-detectors are expected to achieve sensitivities exceeding those of conventional experiments for WIMP-
nucleus interactions mediated by all NREFT operators, with only a weak dependence on the read-out scenario or target mineral. For larger DM masses, $10\ \mathrm{GeV}/c^2$-$5\ \mathrm{TeV}/c^2$, paleo-detectors are projected to attain sensitivities comparable to or surpassing conventional experiments for interactions mediated by several NREFT operators, depending on the specific read-out scenario and choice of target mineral.
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High Energy Physics (Theory)
Gravitational Compton Amplitude to All Orders in Perturbation Theory
Miguel Correia, Giulia Isabella and Anna M. Wolz
We show how amplitudes from the scattering of gravitational waves off compact objects in worldline effective field theory can be efficiently computed to arbitrary order in Newton's constant $G$. Our approach solves an effective wave equation for the partial-wave amplitude in which Wilson coefficients (
tidal Love numbers) enter through boundary conditions at short distances. We then perform the sum over partial waves to obtain the momentum-space Compton amplitude in terms of
elliptic polylogarithms. We reproduce recent results through $\mathcal{O}(G^4)$ and obtain new predictions up to $\mathcal{O}(G^7)$, with Love numbers first contributing at $\mathcal{O}(G^5)$. We find the first ultraviolet divergence in a classical gravitational amplitude at $\mathcal{O}(G^7)$, showing that a pure point-particle description is not consistent in general relativity. Matching to black hole perturbation theory, we show that static Love numbers vanish on-shell and predict subleading non-zero Schwarzschild black hole Love numbers.
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History and Philosophy of Physics
Holography as an Information Principle in Quantum Gravity
Sebastian De Haro, Enrico Cinti and Aude Corbeel
We draw on 't Hooft's seminal formulation of the
holographic principle to analyse the methodological and conceptual role of information in
quantum gravity. We argue that, in 't Hooft's work and in later developments, information functions as a substantive guiding principle. We distinguish three aspects of this role: First,
holographic bounds on the amount of information that can be stored in a region function as theory selection criteria that constrain viable
quantum gravity theories. Second, holography functions as a principle of theoretical equivalence: the bulk and boundary theories must describe the same physical content, even though 't Hooft privileges a more fundamental, lower-dimensional, and potentially deterministic boundary description. Third, the distribution and encoding of information connect 't Hooft's proposals to contemporary work on bulk reconstruction,
holographic quantum error correction, and ER=EPR, where emergent spacetime structure is tied to patterns of
entanglement and redundancy. On the basis of these three roles, we argue that purely epistemic or Shannon-style conceptions of information are inadequate in this context: we instead outline a distinction between what we call maximal and intermediate conceptions that aim to capture the methodological and interpretative roles of information in
holographic quantum gravity. We therefore suggest that, in the context of holography and
quantum gravity, a more systematic philosophical treatment of the role of information as an interpretation-guiding principle would be desirable.
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Cosmology and Nongalactic Astrophysics
Lluís Galbany, Chris Ashall, Jing Lu et al. (+19 more)
SN~2003fg-like events are a peculiar type Ia
supernova (SN~Ia) subtype characterized by broader light curves, higher near-infrared luminosities, and stronger carbon absorptions at early times. Here we present observations of the largest compilation of 2003fg-like SN Ia host
galaxies to date, obtained with Integral Field Spectroscopy (IFS). For 20 objects, we study both the global host-
galaxy properties and, for the first time for a sizeable sample, the local environment at the SN position. Globally, 2003fg-like SNe~Ia occur in
galaxies with lower
stellar mass, lower oxygen abundance, and marginally higher specific
star-formation rate (sSFR) than those of normal SNe~Ia, although their hosts are not as extreme in such properties as superluminous SNe, nor representative of metal-poor
dwarf-
galaxy samples. Locally, the SN positions show lower
star-formation-rate,
stellar-mass surface densities, and lower sSFR, than normal SN~Ia environments, consistent with a significant preference for the outskirts of their hosts, while their
stellar age indicators are typical. The most distinctive local property is
metallicity, with 2003fg-like SNe~Ia occupying the most metal-poor environments among SNe~Ia. We also find a tentative positive correlation between the light-curve width and the oxygen abundance for 2003fg-like events. Our results imply that 2003fg-like SNe~Ia arise from the merger of two white
dwarfs (WDs) or the core-degenerate scenario, but disfavor the single, rapidly rotating super-M$_{ch}$ C-O WD progenitor, as this channel requires a young
stellar population that we do not observe at the SN positions. The preference of 2003fg-like SNe~Ia for low-
metallicity environments suggests that they may have been more common in the early Universe. (abridged)
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All authors Lluís Galbany, Chris Ashall, Jing Lu, Jason T. Hinkle, Willem B. Hoogendam, Benjamin J. Shappee, Alaa Alburai, Ramon Sanfeliu, Joseph P. Anderson, Eddie Baron, Chris Burns, Georgios Dimitriadis, Inma Domínguez, Peter Hoeflich, Eric Y. Hsiao, Hanindyo Kuncarayakti, Joseph D. Lyman, Nidia Morrell, Mark M. Phillips, Sebastián F. Sánchez, Maximilian D. Stritzinger, Nicholas B. Suntzeff
High Energy Astrophysical Phenomena
Using CFHT's SITELLE to Probe the Long-Sought Supernova Remnant Shell in the Crab Nebula
Lucas V. da Conceição, Janette Suherli, Samar Safi-Harb et al. (+3 more)
We present deep, wide-field integral field spectroscopy of the Crab nebula obtained with the imaging
Fourier transform spectrometer SITELLE at the Canada–France–Hawaii
Telescope (CFHT), to search for the long-sought forward shock. Our observations target the coronal line [Fe XIV]$\lambda$5303, a tracer of shock-heated gas, over two $11^{\prime} \times 11^{\prime}$ fields that probe projected radii of $\sim$2.4–10~pc west of the
pulsar, encompassing the range in which a
supernova shell is expected. After data processing and a search over the full field of view, we found no statistically significant [Fe XIV] emission in the surveyed regions. We derive a conservative average surface-brightness upper limit of $\lesssim 3.79 \times 10^{-17}~\mathrm{erg}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}~\mathrm{arcsec}^{-2}$ over three representative annuli. This represents the deepest large-area optical constraint on coronal iron emission beyond the visible nebula from the Crab's putative
supernova remnant (SNR) shell. Our results are consistent with scenarios in which the forward shock is expanding into a very low-density medium, the shocked gas is weak or underionized, or the shell lies outside the observed region. This work demonstrates the power of wide-field optical integral field spectroscopy for constraining faint, large-scale structures in SNRs.
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All authors Lucas V. da Conceição, Janette Suherli, Samar Safi-Harb, Carter Rhea, Ivo R. Seitenzahl, Ashley J. Ruiter
Statistical Mechanics
Critical Properties and Glass Transitions in Randomly Coupled Fields
Amer Al-Hiyasat
We study an assembly of $N$ scalar fields coupled via a quenched random interaction, equivalent to a
spin glass whose
spins are promoted to $d$-dimensional fields. When $N$ is large, the random coupling
matrix produces a family of Gaussian universality classes whose critical exponents are determined by the behavior of the
eigenvalue density near the spectral edge. For a Wigner
matrix, the correlation length diverges at criticality but the susceptibility remains finite, and one-loop replica analysis supports an upper critical dimension of unity. In an exactly solvable spherical variant, the heat capacity jumps at the transition in $d>1$, and correlations remain pinned to their critical form throughout the glass phase, giving generic scale invariance despite the absence of a Goldstone mode.
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Quantum Physics
Quantizing the guiding center: do quantization and coarse graining commute?
Rodrigo Andrade e Silva and Ted Jacobson
We develop a nonperturbative, group-theoretic quantization of the effective guiding center theory of a charged particle drifting in a
magnetic field in two spatial dimensions, and compare the resulting
quantum theory with a corresponding coarse graining of the underlying microscopic theory. In the classical effective theory, the small gyro motion is not resolved, while the motion of the center of the gyro orbit remains observable. The reduced phase space is the physical space itself, so quantization leads to noncommuting spatial coordinates, and the effective theory loses access to the metric structure of physical space, retaining only its area structure. By formulating a prescription to match between the microscopic and effective
quantum theories, we find that the predictions of the quantized effective theory are generally consistent with those of the microscopic theory. However, for closed isomagnetic contours the effective theory predicts a quantization of “radius”, a spatial discreteness absent from the microscopic theory. This illustrates that quantization of an effective theory may yield spurious nonperturbative predictions, even if that
quantum theory shows no internal signs of breakdown.
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