General Relativity and Quantum Cosmology
Higher-derivative gravitational effective field theories are generically weakly hyperbolic
Farid Thaalba, Fernando Abalos and Miguel Bezares
We analyse the initial-value problem of metric higher-derivative effective theories of
gravity. We show that any such theory whose characteristic velocities are independent of derivatives of the metric is intrinsically weakly
hyperbolic, independently of the gauge fixing. To show this, we identify the
spin-$2$ physical sector directly from the characteristic equation; this can be done without introducing an order-reduced formulation, which greatly simplifies the computation. In this sector, every metric theory with more than two derivatives in the equations of motion contains a weakly
hyperbolic block. Since this obstruction is physical, no choice of gauge or constraint addition can remove it, providing a structural explanation for the failure of strong hyperbolicity in this broad class of theories.
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Statistical Mechanics
Slow is fast: raising barriers to accelerate thermal relaxation
Yubo Wang and Zhiyue Lu
For a reversible system relaxing to
equilibrium, the obvious fastest strategy is to lower all kinetic barriers (open all gates). We find that such intuition holds at three levels: the all-open-gate strategy achieves the highest local conductance, it maximizes the instantaneous speed of approach in every $f$-divergence, and it simultaneously maximizes all relaxation
eigenvalues. Nevertheless, we show that a counter-intuitive finite-time optimum lies beyond this intuition and operates at a fourth level, invisible to all three: eigenvector rotation. Noncommutativity enables timed schedules to reproject residual amplitudes across relaxation modes, thereby achieving faster relaxation. Optimal schedules are bang–bang. In our illustrative example, the best-found schedule also employs counter-gating, transiently raising selected barriers, and reduces the terminal residual by a factor of $130$ relative to all-open, and by $7$ relative to the best static landscape. A no-go
theorem shows that noncommutativity is necessary: commuting generators collapse every schedule to a static time-averaged landscape, worse than the intuitive static control. In the reverse problem, the dual schedule preserves nonequilibrium free energy far more effectively than intuitively keeping all barriers at maximum heights. Whether accelerating or delaying relaxation, barrier control performs no work on the reduced Markov system; it only re-times a fixed total dissipation budget.
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Cosmology and Nongalactic Astrophysics
Constraints on Ultra-Light Axions from the DESI DR1 Full Shape, Planck and ACT
Francesco Verdiani, Emanuele Castorina, Ennio Salvioni et al. (+2 more)
We present updated bounds on ultra-light
axions (ULAs) as a subcomponent of dark matter, derived from the full-shape analysis of the DESI Data Release 1
galaxy power spectra combined with
Cosmic Microwave Background (CMB) data from ACT and Planck. We focus on the mass window $10^{-32}\,\mathrm{eV}\leq m_a \leq 10^{-24}\,\mathrm{eV}$, employing state-of-the-art analysis methods rooted in the Effective Field Theory of Large Scale Structure. For the smallest masses, our joint analysis with DESI improves over CMB-only constraints by more than a factor of 2, establishing the most stringent limits to date. For instance, for $m_a \sim 10^{-29}\,\mathrm{eV}$ ULAs are constrained to be a fraction as small as $0.3\%$ of the total matter energy density. The DESI Luminous Red
Galaxy sample shows a mild preference for an ULA subcomponent with $m_a \approx 10^{-26}\,\mathrm{eV}$, mirroring previous hints from BOSS, but this preference vanishes upon combination with CMB data. Probing the largest masses, $m_a\gtrsim10^{-25}\,\mathrm{eV}$, in future studies will benefit from extending the data analysis to smaller scales, both for
galaxy clustering and CMB
lensing, but will also require concurrent improvements in the theoretical modeling.
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All authors Francesco Verdiani, Emanuele Castorina, Ennio Salvioni, Emiliano Sefusatti, Matteo Viel
Astrophysics of Galaxies
Electron Density of Ionized Gas Outflows: Insights from the MaNGA Survey
Andrew Weldon, Casey Papovich, Justin Spilker et al. (+1 more)
We investigate the properties of ionized gas
outflows in nearby
star-forming
galaxies from the final Data Release of the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) Survey. Using spatially resolved spectroscopy, we search for signatures of ionized
outflows within physically motivated
outflow apertures. We find significant evidence for additional broad H$\alpha$, [N II]$\lambda\lambda$6550,6584, and [S II]$\lambda\lambda$6718,6733 emission-line components in 115
galaxies, $\sim$3% of
star-forming MaNGA
galaxies. Our analysis suggests that
outflow electron densities ($n_{\text{e, out}}$), mass-loss rates, and mass-loading factors are related to both the properties of the regions that launch and global
galactic properties. In particular, we find correlations between $n_{\text{e, out}}$ and both the enclosed ($-$3.4$\sigma$) and global ($-$2.4$\sigma$)
star-formation-rate surface densities, such that lower surface density regions tend to drive denser ionized gas
outflows. We find several $>$$2\sigma$ correlations between the mass-loading factor and
galactic properties using individual $n_{\text{e, out}}$ estimates, while more significant correlations ($>$$3\sigma$) only emerge when $n_{\text{e, out}}$ is fixed to the median value of the sample. Combining with literature $n_{\text{e, out}}$ measurements out to $z \sim 1.9$, $n_{\text{e, out}}$ exhibits no significant
redshift evolution, in contrast to the strong
evolution observed for gas electron densities of the interstellar medium (ISM). Ionized
outflows remain denser than the ISM by a factor of $\sim$8.5 at $z \sim 0$ and $\sim$1.6 at $z \sim 1.9$. These results provide new constraints for feedback models and highlight the need for high-resolution IFU observations and synthetic line diagnostics from simulations to investigate the connection between
outflow properties and local ISM conditions.
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All authors Andrew Weldon, Casey Papovich, Justin Spilker, Robert C. Kennicutt Jr
Quantum Physics
Paraparticles intrinsically exhibit Hardy-space breakdown
Kejun Liu
The
memory kernel of an open
quantum system obeys Kramers–Kronig (KK) relations if and only if its Laplace transform is analytic in the upper half-plane – a property known as Hardy-space analyticity. Here we show that non-
unitary exchange statistics, the defining property of paraparticles, intrinsically breaks Hardy-space analyticity. The metric $\eta$ that guarantees a real closed-system spectrum for these particles necessarily differs from the physical Born inner product ($\|\eta - I\|_F / \|I\|_F = 0.51$) – a mathematical consequence of the R-
matrix's non-unitarity, not a parameter choice. This metric is a "shadow metric": Schur's lemma forces it to commute with every bilinear observable, making the distortion physically invisible in the closed system. But when the paraparticle is coupled to a bath, any coupling operator that lies outside the
symmetry algebra – that is, any interaction that sees the internal flavour structure – exposes the distortion. The
memory kernel then develops upper-half-plane poles at coupling $g_c \approx 0.1$, breaking standard dispersion relations before the closed-system spectrum complexifies.
Fermions and
bosons, whose exchange is
unitary ($\eta = I$ as an analytic fact of the canonical anticommutation
algebra), are immune at any coupling, because there is no distortion to expose. The violation is intrinsic: it distinguishes non-
unitary exchange statistics from ordinary particle statistics at the level of the
memory kernel's analytic structure.
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Instrumentation and Methods for Astrophysics
Ardua: Unveiling the Baryon Cycle from Stars to the Cosmic Web
Carlos J. Vargas, Caroline Kilbourne, Haeun Chung et al. (+29 more)
The circumgalactic medium (CGM) – the multiphase gas reservoirs surrounding
galaxies – remains the least understood component of the
baryon cycle governing
galaxy growth, despite its central role in the Astro2020 Decadal Survey's priorities. Existing constraints come almost exclusively from pencil-beam absorption spectroscopy, leaving the spatial structure, kinematics, and phase interactions of CGM gas fundamentally unmapped. We present Ardua, a mission concept for NASA's ASTRA Initiative that combines wide-field far-ultraviolet spectroscopy with a Line Emission Mapper (LEM)-derived X-ray microcalorimeter instrument to obtain the first comprehensive emission maps spanning the full CGM temperature range, including cool neutral gas, ionized warm-hot phase gas, and the volume-filling hot corona. By observing more than 50 nearby
galaxies comprehensively in the UV and X-ray, Ardua will test competing
galaxy formation models, resolve multiphase gas flows and feedback-driven
outflows, and extend
baryon-cycle science to the intergalactic medium and the environments of
exoplanet-hosting
stars. Beyond its core CGM/IGM program, Ardua's wide-field, high-sensitivity instruments are designed to serve as a flexible community resource, supporting guest-investigator science across astrophysics. No planned or approved mission is designed to deliver this combined UV/X-ray survey capability.
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All authors Carlos J. Vargas, Caroline Kilbourne, Haeun Chung, Erika Hamden, Ralph Kraft, Joseph N. Burchett, Lauren Corlies, Claude-André Faucher-Giguère, Kevin France, Keri Hoadley, Briana Indahl, Dong-Woo Kim, Varsha Kulkarni, Jiangtao Li, Nicole Melso, Drew Miles, Nikole M. Nielsen, Anna Ogorzalek, Ben Oppenheimer, Frits Paerels, Daniel Patnaude, Molly Peeples, Frederick S. Porter, David Schiminovich, Malgorzata Sobolewska, Ming Sun, Todd Tripp, Jason Tumlinson, Sarah Tuttle, Jessica Werk, Ka-Wah Wong, John ZuHone
Materials Science
Direct writing of individual quantum dots
Weikun Zhu, Natalie Ngoh, Shelly Ben-David et al. (+9 more)
Quantum light sources capable of generating single
photons are fundamental building blocks for photonic
quantum technologies. In the ongoing search for an ideal
quantum emitter, inorganic halide perovskite nanocrystals have emerged as a promising source of single
photons. Their unique optical response, with an unmatched ease of synthetic tunability, stands out amongst the competing platforms. However, their
stochastic dispersion in solution challenges the deterministic and stable integration of individual emitters with photonic structures that is required for practical technologies. Notably, resolution and material compatibility constraints make conventional top-down fabrication processes insufficient for such heterogeneous integration. Here, we report direct writing of perovskite
quantum dots (QDs) with individual-emitter resolution. By inducing a nanoscale-confined formation volume using a thermal scanning probe method, we achieve site-selective synthesis down to a single atomic-scale QD with spectral tunability and < 25 nm spatial control. As a result, we demonstrate high-yield arrays of CsPbI3 single-
photon emitters with narrow linewidths and high single-
photon purity up to 98% at room temperature, performance consistent with that of their state-of-the-art colloidal counterparts. Through such deterministic control, we uniquely realize the precise, on-demand coupling of these emitters to photonic cavities, as evidenced by a measured enhancement in the spontaneous emission rate. This represents a key advancement toward addressing the longstanding integration obstacles of these materials. Overall, by combining the atomic-scale tunability of chemical synthesis with the spatial control of additive manufacturing, our work opens new emitter engineering strategies to realize the untapped potential of colloidal materials for next-generation
quantum technologies.
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All authors Weikun Zhu, Natalie Ngoh, Shelly Ben-David, Maxwell Conte, Teddy Hsieh, Sarah O. Spector, Tara Sverko, Patricia Jastrzebska-Perfect, Will Jack, Jinwoo Sim, Peter F. Satterthwaite, Farnaz Niroui
Cosmology and Nongalactic Astrophysics
Reconstructing the kinematics of Laniakea using Type Ia Supernovae
Francesco Sorrenti, Erick Pastén and Leonardo Giani
We develop a kinematic framework that relates the monopole, dipole, and quadrupole of the luminosity distance to an ellipsoidal peculiar velocity field describing the dynamics of the Laniakea supercluster. By properly accounting for the transformations between the CMB and Laniakea reference frames and selecting Type Ia
supernovae within the volume associated with the superstructure, we show that luminosity distance multipoles encode the expansion and shear of the local velocity field. This allows the ellipsoidal kinematics of Laniakea to be inferred directly from
supernova observations. Our results provide a physically motivated interpretation of luminosity distance anisotropies within the volume dynamically dominated by Laniakea as signatures of its large-scale kinematics. The framework developed here suggests that future
supernova observations can enable the independent reconstruction of large-scale structures in the local Universe
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Quantum Physics
Noise Resilience of Quantum Key Distribution Protocols Secured Against Independent Attacks With One-Way Communication
Adam Bílek, Ryszard Kukulski, Paulina Lewandowska et al. (+2 more)
We investigate the resilience to noise of single-
qubit quantum key distribution (QKD) protocols in the scenario of security against independent eavesdropping attacks and key
distillation based on one-way classical communication. To this end, we introduce a noise-based metric that quantifies the efficiency of QKD protocols. Within this framework, we analyze the maximal noise levels that allow Alice and Bob to asymptotically establish a secure secret key. Using this assumption, we compare the noise tolerance of general single-
qubit QKD protocols, in particular the BB84, B92, E91, and six-state protocols. Our main result determines the noise level threshold for QKD allowing one to distill an asymptotically secure secret key. Additionally, we demonstrate that the six-state protocol achieves the greatest resistance to noise while simultaneously yielding a higher post-selection efficiency than the other analyzed single-
qubit protocols, confirming its robustness within the considered security model. Finally, we perform an analysis of the proposed noise-based metric and the conventional
quantum bit error rate (QBER) metric.
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All authors Adam Bílek, Ryszard Kukulski, Paulina Lewandowska, Łukasz Pawela, Zbigniew Puchała
Quantum Physics
Trotter error compensation with polylogarithmic precision and nested-commutator scaling without ancillas
Xinzhao Wang, Shuo Zhou, Ziruo Wang et al. (+5 more)
Product formulas are among the most practical approaches to
Hamiltonian simulation, requiring no ancillary
qubits and exhibiting error bounds governed by nested commutators rather than only by
Hamiltonian norms. Their
circuit size, however, scales polynomially with the inverse precision. We develop a high-order nested-commutator compensation (HNCC)
algorithm that preserves the main advantages of product formulas while achieving polylogarithmic precision dependence in the
circuit size and the standard $\mathcal{O}(\varepsilon^{-2})$ sampling cost. HNCC uses a truncated Baker–Campbell–Hausdorff expansion to represent high-order Trotter errors by products of nested commutators and compensates these errors at the channel level through randomly sampled Pauli-rotation channels, avoiding Hadamard tests and ancillary
qubits. For a fixed $K$-th order product formula applied to a $k$-local
Hamiltonian on $N$
qubits with $\Gamma$ Pauli terms and local interaction strength $g_0$, HNCC estimates $\operatorname{tr}[Oe^{-i tH}\rho e^{i tH}]$ to additive precision $\varepsilon\|O\|$ using $\mathcal{O}(\varepsilon^{-2})$ repetitions. Its maximum gate count per
circuit is $\mathcal{O}\bigl( kN^{\frac{1}{2K+1}} \Gamma^{1-\frac{1}{2K+1}} \max\{\Gamma,N\log(1/\varepsilon)\}^{\frac{1}{2K+1}} (kg_0t\log(1/\varepsilon))^{1+\frac{1}{2K+1}} \bigr)$. Finite-size resource estimates for the periodic Heisenberg chain indicate that HNCC has the lowest estimated $T$-gate count per
circuit among the product-formula-based methods considered.
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All authors Xinzhao Wang, Shuo Zhou, Ziruo Wang, Pei Zeng, Jinzhao Sun, Qi Zhao, Tom Gur, Tongyang Li
Quantum Physics
Bounding Kirkwood-Dirac negativity of Gaussian processes
Luca Bianchi, Carlo Marconi, Riccardo Cioli et al. (+1 more)
The Kirkwood-Dirac quasiprobability provides an operational representation of a
quantum state, whose negativity serves as a measure of nonclassicality. Despite its fundamental importance, the extremal values of the Kirkwood-Dirac negativity are still unknown in the general case. We investigate the Kirkwood-Dirac quasiprobability of an arbitrary
quantum state under Gaussian processes. In this setting, we derive an upper bound on the negativity for any number of modes and measurements. For a single mode and two measurements, we show that the eigenstates of the quadrature operators saturate this upper bound, while a nontrivial minimum is reached by pure Gaussian states. As a consequence, our results indicate that Gaussian states are sufficient to achieve extreme values of nonclassicality.
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All authors Luca Bianchi, Carlo Marconi, Riccardo Cioli, Jan Sperling
General Relativity and Quantum Cosmology
Corrected thermodynamics and radiation predictions of modified black bounce compact objects
Shokhzod Jumaniyozov, Javlon Rayimbaev, Yassine Sekhmani et al. (+3 more)
We study the thermodynamic properties and radiation characteristics of a regular compact object obtained by applying the Simpson-Visser (SV) regularisation to the Schwarzschild modified
gravity black hole. The resulting SV-MOG spacetime, whose lapse function involves both the MOG coupling parameter alpha and the black-bounce parameter l, smoothly interpolates between a regular black hole, a one-way wormhole, and a traversable wormhole depending on the parameter l. We derive the Hawking temperature and heat capacity for the black hole branch, identifying second-order phase transitions signaled by sign changes in CV, and, for the horizonless wormhole branch where no causal horizon and hence no genuine Hawking radiation exists we instead construct a physically well-defined effective temperature from the Lyapunov exponent of the unstable
photon sphere.
Quantum gravitational corrections to the
entropy are incorporated via logarithmic terms parameterized by coefficients beta1, beta2, whose theoretically preferred ranges in loop
quantum gravity and string theory we discuss, and we show that deviations from the Bekenstein-Hawking area law become significant at small horizon radii. A linear scalar-perturbation analysis further shows that the effective radial potential remains non-negative throughout the black-hole exterior and across the wormhole throat, indicating stability against monopole perturbations independently of the thermodynamic stability inferred from the heat capacity.
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All authors Shokhzod Jumaniyozov, Javlon Rayimbaev, Yassine Sekhmani, Satimbay Palvanov, Olmos Tursunboyev, Dilshod Karshiev
High Energy Physics (Theory)
Effective dynamics and quantum information in de Sitter wedge holography
Sabyasachi Maulik and Soumen Pari
In this paper, we study codimension-two holography in a de Sitter (dS) wedge setup, based on the idea of wedge holography. We consider a $d+1$-dimensional Anti-de Sitter (AdS) bulk spacetime bounded by two end-of-the-world branes with $d$-dimensional de Sitter geometry. We propose that this configuration is holographically dual to a conformal field theory (CFT) living on a $d-1$-dimensional sphere. Our computations of the partition function and
holographic entanglement entropy support this duality and indicate that the dual CFT is non-
unitary. We also analyze the mass spectrum in dS wedge holography. We verify the first law of
entanglement entropy within this framework. Finally, we make use of the island prescription to study the Page curve in a simplified model within our dS wedge holography framework.
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Quantum Physics
Optimal tomography of bosonic and fermionic Gaussian states
Senrui Chen, Marco Fanizza, Filippo Girardi et al. (+4 more)
The sample complexity is the minimum number of copies required to learn an accurate classical description of a
quantum state. Bosonic and fermionic Gaussian
quantum states are families of
quantum states that play a key role in
quantum science and technology, from
quantum optics and many-body physics to
quantum chemistry,
quantum computing, and
quantum information theory. Despite their importance, their sample complexity had not been fully determined. We settle this open problem and show that both bosonic and fermionic Gaussian states can be learned using a number of copies that scales quadratically in the number of modes, regardless of whether the state is pure or mixed, and independently of any energy bound on the state. We derive these results by using the representation theory of Gaussian
unitaries and by putting forth a generalization of the random purification channel to this setting and beyond.
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All authors Senrui Chen, Marco Fanizza, Filippo Girardi, Ludovico Lami, Francesco Anna Mele, Michael Walter, Freek Witteveen
Quantum Physics
Optimal operating temperature for industry-compatible silicon spin quantum computing: colder is not necessarily better
Paul Steinacker, Amanda E. Seedhouse, Nard Dumoulin Stuyck et al. (+22 more)
Silicon
spin qubits are a leading candidate for large-scale
quantum computing owing to their compatibility with
semiconductor manufacturing. However, scaling to useful fault-tolerant processors will likely generate thermal loads that exceed the cooling power available at millikelvin temperatures. Raising the operating temperature eases cooling requirements but reduces gate fidelity, increasing the overhead of
quantum error correction. Identifying the operating temperature that minimizes total power consumption is therefore a key challenge for commercially viable
quantum computers. Here, we use gate set
tomography to
benchmark two-
qubit silicon chips fabricated in both industrial and academic environments over a range of temperatures. Elevated temperatures substantially shorten coherence times and increase gate and state-preparation-and-measurement infidelities. Based on these measurements, we develop a general power model for silicon
quantum computers that combines cryogenic cooling requirements with error-correction overheads. We show that a finite optimal operating temperature exists and is strongly influenced by a crossover temperature near 1 K in current devices, above which gate fidelity degrades rapidly. These results connect device-level fidelity limitations to system-level power requirements, providing design guidelines for large-scale silicon
quantum computers.
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All authors Paul Steinacker, Amanda E. Seedhouse, Nard Dumoulin Stuyck, Tuomo Tanttu, MengKe Feng, Santiago Serrano, Ensar Vahapoglu, Samuel K. Bartee, Philip Y. Mai, Alexis Shaw, Andreas Nickl, Sebastian Pauka, Brendan Harlech-Jones, Juan P. Dehollain, Fay E. Hudson, Kok Wai Chan, Thomas A. Ohki, David Reilly, Christopher C. Escott, Chih Hwan Yang, Wee Han Lim, Arne Laucht, Andre Saraiva, Andrew S. Dzurak, Jared H. Cole
High Energy Physics (Phenomenology)
A Standard Model analysis of $D^0 \to \pi^- \pi^+, K^- K^+, K_{\rm S}^0 K_{\rm S}^0$
Robert Fleischer, Maria Laura Piscopo, K. Keri Vos et al. (+1 more)
We investigate the Standard Model (SM) description of the singly Cabibbo-suppressed charm decays $D^0\to \pi^-\pi^+$, $D^0\to K^-K^+$ and $D^0\to K_{\rm S}^0K_{\rm S}^0$. Using factorisation together with isospin
symmetry, we constrain non-factorisable effects and the associated $U$-
spin breaking required by the measured branching fractions. We find that corrections of order $50\%$ are sufficient to describe all modes, which although sizeable, are not unexpected for hadronic charm decays. Using the constraints from the branching fractions, we derive SM predictions for the direct CP asymmetry in $D^0\to K_{\rm S}^0K_{\rm S}^0$, finding it to be at most at the per-mille level in our
benchmark scenario, providing motivation for future precision measurements.
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All authors Robert Fleischer, Maria Laura Piscopo, K. Keri Vos, B. Yağmur Zubaroğlu
Quantum Physics
Input-Aware Dynamic Backdoor Attack Against Quantum Neural Networks
Junrui Zhang, Zemin Chen, Lusi Li et al. (+3 more)
Quantum Neural Networks (QNNs) are a promising framework for
quantum machine learning on near-term
quantum devices, but their security risks remain insufficiently understood. Studies have shown that QNNs are vulnerable to
backdoor attacks, yet existing
quantum backdoors mostly rely on a fixed trigger shared by all poisoned inputs. This fixed-trigger design is a major weakness because many defenses detect or weaken the repeated patterns such triggers leave in data representations. Although input-aware dynamic
backdoors have been studied in classical neural networks, transferring them to QNNs is difficult because
quantum learning introduces new obstacles. In particular, measurement compresses the post-ansatz
quantum state into a limited classical output, weakening supervision for a trigger generator, while individual density
matrices fluctuate with the input and make per-sample contrastive learning unstable. To address these challenges, we propose Q-DIBA, the first input-aware dynamic
backdoor attack for QNNs. Q-DIBA jointly trains a classical trigger generator and a victim QNN through a three-mode mini-batch strategy that supports clean behavior, attack activation, and trigger specificity. To provide stable
quantum-level supervision, Q-DIBA introduces an ensemble density contrastive loss that operates on post-ansatz
quantum states before measurement and contrasts mode-averaged density
matrices rather than individual samples. Experiments on MNIST and Fashion-MNIST across multiple QNN architectures show that Q-DIBA achieves high clean accuracy, strong attack success, and high cross-trigger accuracy, demonstrating effectiveness, stealthiness, and input specificity. The attack also remains resilient against defenses including visual inspection, spectral-signature detection, and fine-tuning, suggesting that input-aware
quantum backdoors are an important threat to secure QNN deployment.
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All authors Junrui Zhang, Zemin Chen, Lusi Li, Mohammad Ghasemigol, Daniel Takabi, Rui Ning
Cosmology and Nongalactic Astrophysics
Anisotropic Dirac-Born-Infeld Inflation with Non-Vacuum Initial States: Primordial Perturbations, Non-Gaussianity, and Observational Constraints
Narges Rashidi and Maryam Roushan
We investigate linear and nonlinear
primordial perturbations in an anisotropic Dirac-Born-Infeld (DBI) inflationary model with a non-
vacuum initial state. Using the Arnowitt-Deser- Misner (ADM) formalism, we expand the action up to second and third order in the
curvature perturbation and derive the corresponding scalar and tensor power spectra, as well as the bispectrum and the equilateral non-linearity parameter \(f_{NL}^{\mathrm{equil}}\). The effects of anisotropic corrections and non-Bunch-Davies (non-BD) initial conditions are incorporated through the slow-roll sector and Bogoliubov coefficients. For the numerical analysis, we consider an intermediate expansion scenario together with a phenomenological ansatz for the excited-state occupation number \(N_k\). By comparing the model predictions with recent observational
datasets, including Planck2018 TT, TE, EE + lowE +
lensing + BK18 + BAO and DESI+CMB+DESY5 data, we identify observationally viable regions in the parameter space of the model. Our analysis indicates that the anisotropic DBI scenario with non-
vacuum initial conditions can remain compatible with current constraints on the scalar spectral index, tensor-to-scalar ratio, and equilateral non-Gaussianity for suitable ranges of the anisotropy parameter \(c\) and the initial-state parameter \(N_{k,0}\).
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Earth and Planetary Astrophysics
Ice Deposition Fronts In Porous Bodies From Transient Heating Events In a Protoplanetary Disk
Stephen Li, Alice C. Quillen, Adam E. Rubinstein et al. (+2 more)
Using a 1D mass and heat transport model, we numerically integrate heat flow and gas transport in a porous body exposed to a transient heating event while embedded in a protoplanetary disk. When small icy grains are heated, volatiles sublimate, enriching the disk with volatile gases. When a porous body enters this heated, volatile-rich environment, volatile gases diffuse throughout the cool, porous body and deposit ice where the partial pressure of a volatile exceeds its vapor pressure. We simulate sublimation and deposition fronts of water, carbon dioxide, and carbon monoxide. Our simulations show that an ice deposition front forms and moves deeper into the porous body as the body warms. The amount of nebular gas deposited in an initially dry body is usually extremely low; however, in an initially icy body, an ice deposition front contains locally sublimated volatiles. In this case, the front can increase the ice volume fraction (by a factor of 2) in a thin layer below the surface. We find that the propagation speed, propagation strength, and final depth of an ice deposition front primarily depend on pore size. We propose that nebular heating events can alter the subsurface morphology and physical properties of porous icy objects embedded in a protoplanetary disk.
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All authors Stephen Li, Alice C. Quillen, Adam E. Rubinstein, Dominique Segura-Cox, Kevin Righter
General Relativity and Quantum Cosmology
Universal Bounds on Black Hole Observables Imposed by Energy Conditions
Rahul Kumar Walia, Boris Georgiev and Chi-kwan Chan
Energy conditions (ECs) underpin fundamental results in general relativity, yet their observational validity in strong gravitational fields remains largely untested. Here, we establish a direct correspondence between the local stress-energy tensor,
photon-orbit dynamics, and strong-field observables associated with black hole shadows,
photon rings, and eikonal gravitational-wave ringdown for static, spherically symmetric black holes within general relativity. We show that imposing local ECs at unstable
photon spheres yields analytic bounds on these observables. In particular, the demagnification of successive
photon rings provides an exact diagnostic of the local tangential null energy condition. These bounds offer a direct route to constraining the matter fields sourcing spacetimes and testing ECs through strong-field observations. Combining them with observational measurements of these observables further restricts admissible black hole geometries and additionally constrains the otherwise inaccessible
photon sphere geometry and local stress-energy content, demonstrating their observational potential in the strong-field regime.
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Atmospheric and Oceanic Physics · Cross-listed from stat.AP
Improved Global Ocean Heat Content Estimation by Modeling Vertical Spatio-Temporal Dependence
Thea Sukianto, Donata Giglio and Mikael Kuusela
Estimating ocean heat content (OHC) with reliable uncertainties is critical for understanding and monitoring the
evolution of Earth's
climate, as the ocean has stored most of the energy accumulated in the
climate system due to Earth Energy Imbalance. Here, we use Argo profiling float data from 2004-2022 to map OHC. As fewer Argo observations are available deeper in the water column, previous studies have partitioned the ocean into at least two pressure layers and mapped each separately, which complicates the estimation of uncertainties when the maps are summed to get the total OHC. In this work, we consider the case of two pressure layers and propose an improved mapping and uncertainty quantification method using bivariate locally stationary Gaussian processes and conditional simulations to map the two sections jointly while accounting for the correlation between them. We find that modeling this correlation results in improved OHC anomaly mapping and up to a 15 percent reduction of global OHC anomaly uncertainties in comparison to mapping the two layers separately without accounting for their dependence. These estimated uncertainties are essential to analyze the statistical significance of OHC anomalies on both regional and global scales, which we demonstrate using several climatological case studies.
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Quantum Physics
Multiparameter Quantum Metrology in Molecular Dimers
Omar Bachain, Mohamed Amazioug and Rachid Ahl Laamara
We investigate multiparameter
quantum estimation in a molecular dimer composed of two dipole–dipole interacting two-level systems, focusing on the simultaneous estimation of temperature $T$ and detuning $\Lambda$. By employing a vectorization approach to derive the
quantum Fisher information
matrix, we analyze the precision limits of both simultaneous and individual estimation strategies. We show that simultaneous estimation outperforms the individual one in the near-resonant and low-temperature regime, where
quantum coherence is enhanced, while its advantage is progressively reduced under detuned conditions and increasing temperature. Our results demonstrate that temperature acts as a key control parameter governing both estimation precision providing a unified perspective on
quantum metrology. These findings highlight the potential of molecular
quantum systems as realistic platforms for multiparameter
quantum sensing.
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Quantum Physics
Quantum probe advantage in learning many-body systems
Wenzheng Dong, Andrew G. Green, Vlatko Vedral et al. (+1 more)
Which properties of a
quantum many-body system are operationally accessible is a central question underlying spectroscopy, thermodynamics, and
quantum information science. Conventional response theory answers this question within a system-only paradigm: one perturbs and measures the matter itself, obtaining susceptibility built from causally ordered nested commutators. Here we show that coherently controlled
quantum probes, when measured at the end, define a strictly larger operational learning framework beyond that accessible from response theory. We establish this through a
quantum-
circuit description that unifies spectroscopy, probe microscopy, and probe-based
quantum technologies within a common operational framework, from which we develop
quantum protocols for learning many-body properties from probe readout only. This advantage arises because the reduced dynamics of
quantum probes generically encode anti-commutator and mixed-order correlators of the target; therefore, measurements on the probe provide access to fluctuations, non-
equilibrium structure, and
entanglement entropy that are in general not accessible through response functions or a single probe alone. Moreover, we demonstrate that entangled probes can access many-body properties such as von Neumann
entropy. We prove that the required probe resources scale with the complexity of the target correlations rather than with the size of the many-body system.
Quantum probes are therefore not merely more sensitive sensors but provide a new way to learn many-body properties distinct from those of
tomography or
quantum simulation.
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All authors Wenzheng Dong, Andrew G. Green, Vlatko Vedral, Jinzhao Sun
High Energy Physics (Theory)
Modular structures in the DSSYK partition function
Matteo Beccaria and Eleonora Alfinito
We study the low-temperature expansion of the disk partition function $Z(\beta)$ of the double-scaled SYK model (DSSYK) at fixed coupling $\lambda=2p^{2}/N$, where $N$ is the number of Majorana
fermions and $p$ is the number of
fermions in each interaction term, both taken to infinity. We show that the exact Bessel-function representation of $Z(\beta)$, expanded at large argument (corresponding to low temperature), can be organized in terms of the classical ring of quasi-modular Eisenstein series $E_{2},E_{4},E_{6}$ and their differential identities. Exploiting the modular $S$-duality properties of this ring, we derive the semiclassical (small $\lambda$) low-temperature expansion of $Z(\beta)$, splitting it into a perturbative tower and a non-perturbative sector controlled by $\widetilde q=e^{-4\pi^{2}/\lambda}$. At each order in $\widetilde q$, we determine the non-perturbative correction in closed form up to second order in $\lambda$; the resulting series resums into a compact expression in the same Eisenstein series, extending previous semiclassical results beyond their strict $\beta\to\infty$ limit. We further show that this entire structure follows from a single, exact differential equation coupling a modular derivative to derivatives with respect to temperature. Finally, we prove that the non-perturbative sector of $Z(\beta)$ is exactly supported, to all orders in $\lambda$, on the same exponents as the on-shell actions of known bilocal-Liouville saddles of the DSSYK Schwarzian limit, pointing to a well-defined bulk origin for these non-perturbative corrections.
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Instrumentation and Methods for Astrophysics
WALOP-South: a four camera one shot imaging polarimeter for the PASIPHAE survey. Paper III – PSF modelling
Indrajit Paul, Kishan Deka, Tuhin Ghosh et al. (+22 more)
The two WALOP instruments, built for the PASIPHAE survey, will measure the linear polarization of large numbers of
stars in the
Galactic polar regions in the SDSS-$r$ band. They are designed with a wide field-of-view, enabling measurement of the Stokes parameters $I$, $q$, and $u$ for multiple
stars simultaneously within a $35^\prime \times 35^\prime$ region of sky for WALOP-South and $30^\prime \times 30^\prime$ region for WALOP-North. In this paper, we present a polar shapelet-based PSF photometry framework for well-sampled
stellar point sources applicable to WALOP-type wide-field polarimeters. Polar shapelets are a set of orthogonal basis functions, constructed from Gauss-Hermite or Gauss-Laguerre
polynomials, that are well-suited to modelling localized PSF in a compact and efficient way. We developed an efficient PSF modelling method that uses polar shapelets as basis functions to reconstruct the spatial variation of the PSF shape across the CCD using Zemax-simulated images of one of the WALOP instruments, and show that a limited number of shapelet coefficients are sufficient to capture this variation consistently across different CCD locations. To simulate realistic
star images, we introduce random sub-pixel shifts in the
star centroids in the Zemax-simulated images, and account for this using a two-step iterative method that alternately estimates the PSF model and the sub-pixel centroid shift. Applying PSF photometry to the target faint
stars, we demonstrate that the photometric accuracy of approximately 0.15% is achievable, and that the reconstructed PSF model can be incorporated into the photometry across different seeing conditions, meeting the polarimetric science requirements of the PASIPHAE survey.
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All authors Indrajit Paul, Kishan Deka, Tuhin Ghosh, Siddharth Maharana, A. N. Ramaprakash, Ramya M. Anche, Artem Basyrov, Dmitry Blinov, Hans Kritian Eriksen, Eirik Gjerløw, John A. Kypriotakis, Sebastian Kiehlmann, Ioannis Liodakis, Nikolaos Mandarakas, Georgia V. Panopoulou, Vasiliki Pavlidou, Timothy J. Pearson, Vincent Pelgrims, Stephen B. Potter, Anthony C. S. Readhead, Raphael Skalidis, Trygve Leithe Svalheim, Konstantinos Tassis, Namita Uppal, Ingunn K. Wehus
Solar and Stellar Astrophysics
Time-Resolved Connection between Starspots and Flares in Nearby Young Solar-type Stars Observed by TESS
Daijiro Hitotsuyanagi, Hiroto Yamada, Daisuke Yamashiki et al. (+3 more)
Superflares are energetic explosions on
stellar surface with energies of 10^33-10^36 erg, significantly exceeding those of typical
solar flares. While previous studies have suggested that these events are driven by
magnetic energy stored in large starspots, the detailed time-resolved relationship between starspot area and
flare activity on individual
stars has remained unclear. In this paper, we investigate the time
evolution of
magnetic activity on three representative young
solar-type
stars (EK Draconis, DS Tucanae A, and V889 Herculis) using $\sim$7 years of photometric data from the Transiting
Exoplanet Survey Satellite (TESS). We automatically detected
stellar flares and derived the
flare frequency, starspot area, and rotational period for each TESS sector covering ~27 days. As a result, we found that the
flare frequency and starspot area vary significantly across sectors, although we could not identify any activity-cycle-like pattern. There is a positive correlation between the starspot area and
flare occurrence frequency for all three targets and the power-law dependence is consistent among the
stars. This result supports the physical picture that superflares on young
solar-type
stars are powered by
magnetic energy stored in large starspots, analogous to
solar flares, and that the energy release rate changes as the total stored
magnetic energy varies. Furthermore, from the analysis of EK Draconis, we find a possible dependence of starspot area on rotation period, which may suggest that large starspots preferentially form at mid-latitudes. These findings demonstrate that the
magnetic activity mechanisms established for the Sun extend to the extreme
magnetic activity observed on young active
stars.
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All authors Daijiro Hitotsuyanagi, Hiroto Yamada, Daisuke Yamashiki, Kazuma Ishihara, Yosuke Yamashiki, Kosuke Namekata
Quantum Physics
Multiparameter Quantum Estimation in a Raman-Coupled Two-Qubit System
Omar Bachain, Mohamed Amazioug and Rachid Ahl Laamara
We investigate multiparameter
quantum estimation in a Raman-coupled two-
qubit system at thermal
equilibrium. Analytical expressions for the
quantum Fisher information
matrix are derived to characterize the simultaneous estimation of the temperature and Raman coupling strength. The corresponding
quantum Cramér–Rao bounds are obtained and compared with those of individual estimation strategies. Our results reveal optimal operating regimes determined by the interplay between thermal fluctuations and coherent interactions. In particular,
quantum thermometry exhibits a well-defined optimal temperature window, whereas the estimation of the Raman coupling strength is significantly enhanced in the low-temperature and weak-coupling regime. We further show that simultaneous estimation can outperform independent estimation within appropriate parameter regions, highlighting the advantages of multiparameter
quantum metrology. These results provide analytical insights into the ultimate precision limits of Raman-coupled two-
qubit systems and identify promising operating regimes for
quantum sensing and
quantum thermometry.
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Fluid Dynamics
Coherence as Thermodynamic Organization: Toward a Non-Equilibrium Turbulence Theory
Sharath S. Girimaji
Since the foundational studies in the late nineteenth century, fluid
turbulence has stood as a profound, unsolved challenge in classical physics. Much of this enduring difficulty stems from non-
equilibrium turbulence, where the lack of a unifying physical framework for macroscopic coherent structures has hampered predictive flow modeling. Here, we establish a foundational bridge between non-
equilibrium statistical physics and turbulent coherent structures through the renormalized Navier-Stokes equations. We demonstrate that all forms of turbulent coherence are fundamentally universal thermodynamic responses mandated by macroscopic energy throughput imbalances. Depending on topological access to bifurcations, these formations manifest either as transient adjustments (analogous to Kubo's near-
equilibrium fluctuations) or as autonomous, transformative states (mirroring Prigogine's far-from-
equilibrium dissipative structures). By introducing a computable, effective thermodynamic order parameter ($\Pi$), this paradigm establishes a rigorous foundation for non-
equilibrium theory, enabling unequivocal identification of necessary flow resolution in continuously driven, dissipative continuum systems.
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High Energy Physics (Experiment)
Analytical Markov Chain for Spatiotemporal Flux Evolution of the Inner Filter Effect in Fluorescent Media
Xuhui Yang and Guofu Cao
Characterizing emission and decay time spectra in multi-component fluorescent media is essential for identifying intrinsic material properties and optimizing detectors. However, wavelength
evolution from the secondary inner filter effect (IFE) distorts these observable spectra. While Monte Carlo (MC) ray-tracing can simulate this distortion, accumulating adequate tracking statistics requires long computation times, which hinders parameter optimization within high-dimensional spaces. This paper presents an analytical Markovian transport model based on spatiotemporal decoupling. A Laplace transform converts the multi-nested convolution integrals over continuous domains into a discrete Markov transition
matrix, reducing the computational complexity from an exponential scale with respect to wavelength bins $N_{\lambda}$ and cascade order $n$, $\mathcal{O}(N_{\lambda}^n)$, to a linear scale, $\mathcal{O}(N_{\lambda} + n)$. The resulting algebraic solutions evaluate transient decay time spectra as a continuum superposition of Gamma wave packets and predict steady-state wavelength spectrum distortions driven by the IFE within a sub-second timescale. Validations across orthogonal and front-face spectrometer configurations show that the calculated spectra match MC simulations in lineshape. This model can serve as a fast forward engine to accelerate parameter space screening, provide early-stage detector design references, and act as a physics-constrained input for event vertex reconstruction
algorithms.
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Cosmology and Nongalactic Astrophysics
Anisotropic separate universe : Long-wavelength perturbations and conserved quantities
Daiki Saito and Atsushi Naruko
We investigate the long-wavelength
evolution of linear perturbations in a homogeneous and anisotropic background with a scalar field coupled to a vector field. Using the spatial gradient expansion in the uniform-$\mathcal{N}$ gauge in which the number of $e$-folds is unperturbed, we derive the complete set of superhorizon solutions and establish their correspondence with infinitesimal variations of the homogeneous anisotropic background. This extends the separate-universe picture, previously known for isotropic FLRW cosmology, to anisotropic spacetimes despite the mixing of scalar, vector, and tensor perturbations induced by broken rotational
symmetry. We show that the long-wavelength equations form a self-consistent system and identify a conserved quantity that generalizes the conserved Wronskian of isotropic cosmology. Unlike the isotropic case, the superhorizon modes sourcing the
curvature perturbation are governed by three independent conserved channels associated with the scalar field, the background shear, and the gauge-field tilt, together with an additional dynamical shear contribution originating from the anisotropic geometry. This reveals that the
evolution of
curvature perturbations around anisotropic background is intrinsically richer than in isotropic multi-field models. Our formulation provides a practical prescription for computing the final
curvature perturbation directly from horizon-crossing fluctuations, thereby establishing the anisotropic generalization of the $\delta N$ formalism. We further derive an explicit relation between
curvature perturbations and
primordial gravitational waves, demonstrating how anisotropic expansion couples scalar and tensor sectors on superhorizon scales. Our framework provides a practical basis for predicting statistical anisotropies in
primordial scalar and tensor perturbations.
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