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Friday 7 August

Astrophysics of Galaxies

A Review of Galaxy Quenching – Part II: Theoretical Solutions and Direct Observational Tests

Asa F. L. Bluck

The goal of this review article series is to provide a comprehensive overview of galactic star formation and quenching from both an observational and theoretical perspective. Drawing on a vast quantity of literature, we attempt to answer a deceptively simple question: why do galaxies cease forming stars? In Part II, we concentrate primarily on results from theory and simulations, in addition to direct observational tests of theoretically proposed quenching routes. Over the past two decades, N-body simulations, semi-analytic models, idealized hydrodynamical simulations, cosmological hydrodynamical simulations, and zoom-in hydrodynamical simulations have all provided crucial insights into the fundamental causes and specific mechanisms of galaxy quenching. Throughout this part of the review, we discuss intrinsic routes to massive galaxy quenching from strong baryonic feedback - including supernovae and active galactic nuclei (in both the ejective and preventative modes). Additionally, we discuss dynamical stabilization and the role of mergers. We go on to consider environmental routes to quenching via both ram pressure and dynamical stripping, and as a consequence of the location of satellite galaxies within the cosmic web. We review observational tests of the fundamental causes, specific mechanisms, and triggering of quenching from various techniques. Finally, we conclude this review with tentative answers to the major outstanding issues in this field.
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Mathematical Physics

The two-sided Bogoliubov inequality in von Neumann algebras conceptualizes the free energy–quantum correlations link

Benedikt M. Reible, Albert Much, Rainer Verch et al. (+2 more)

The quantum-mechanical two-sided Bogoliubov inequality provides upper and lower bounds for the free energy required to separate a system of interacting particles into independent subsystems. The bounds can be calculated straightforwardly from the ensemble average of the interface energy, bypassing the direct evaluation of the free energy. In this work, we generalize the two-sided Bogoliubov inequality to arbitrary von Neumann algebras by employing the Araki-Uhlmann relative entropy and the framework of unbounded perturbation theory of KMS states. Furthermore, we obtain variational expressions for the relative free energy that extend existing bounded-perturbation principles to the unbounded setting. Crucially, these mathematical developments yield a physically well-founded thermodynamic criterion for the quantification of entanglement in infinite-dimensional systems.
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All authors Benedikt M. Reible, Albert Much, Rainer Verch, Christof Schütte, Luigi Delle Site

Quantum Physics

Consequences of a dynamical no-signaling condition for classical-quantum interactions

S. Camalet

Hybrid classical-quantum approaches are instrumental in numerous fields, from condensed matter physics to quantum information science. We recently proposed to describe hybrid systems starting from a set of natural axioms for measurement probabilities without adding any underlying mathematical structure. The so defined probability measures fulfill a no-signaling condition that ensures that instantaneous communication is impossible. We formulate here a dynamical generalization of this condition. It means that, for two independent systems, the outcome probabilities of a measurement made on one of them are not affected by a measurement performed earlier on the other. Analogous requirements are satisfied for usual classical and quantum bipartite systems and violating them would make faster-than-light signaling possible. The dynamical no-signaling condition has important consequences for classical-quantum interactions that depend on the hybrid approach used. For no-signaling hybrid dynamics with classical trajectories, the classical degrees of freedom can influence the quantum ones but the latter cannot react on the former. If pure states of quantum systems remain pure then the dynamical no-signaling condition implies the absence of classical reaction. When all hybrid states are allowed, there are no genuine classical-quantum interactions for no-signaling hybrid dynamics that do not generate correlations between the classical and the quantum degrees of freedom. In all these cases, the proposed condition is equivalent to the convex-linearity of the probability measure transformations describing finite-time evolutions.
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Quantum Gases

Crossing over universal scaling laws in two-dimensional driven dissipative condensates

Q. Fontaine, F. Helluin, M. Escalera et al. (+8 more)

In low dimensional systems, fluctuations are enhanced and prevent the spontaneous breaking of continuous symmetries. As a result, spatial and temporal correlation functions decay at large distances and long times. A well established example is given by two-dimensional bosonic condensates at equilibrium, which do not display long-range order of the coherence but algebraic decay belonging to the Berezinski-Kosterlitz-Thouless universality class. In contrast, the universal behaviors of non-equilibrium bosonic condensates are more diverse and many open questions remain. Here, we explore the spatio-temporal coherence properties of two-dimensional driven-dissipative polariton condensates in semiconductor optical microcavities. By tuning microscopic parameters, we observe a cross-over between two scaling laws that we attribute to the Edwards-Wilkinson (EW) and the Kardar-Parisi-Zhang (KPZ) universality classes. We demonstrate the collapse of the measured first-order correlations onto the EW and KPZ universal scaling functions and obtain critical exponents, well matching the values predicted theoretically. Our results highlight the intrinsic non-equilibrium nature of polariton condensates and establish them as a platform of choice for controlled exploration of the two-dimensional KPZ universality class.
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All authors Q. Fontaine, F. Helluin, M. Escalera, D. Pinto Dias, A. Lemaître, M. Morassi, M. Wouters, A. Minguzzi, L. Canet, S. Ravets, J. Bloch

Optics

Giant backward Brillouin interaction in generic InP integrated photonics

Riley te Morsche, Lukas Puts, Weiming Yao et al. (+1 more)

We report the first measurement of backward stimulated Brillouin scattering (SBS) in generic InP waveguides, supporting enhanced Brillouin gain of $g_B/Q_m = 3.5 \pm 0.6~\text{W}^{-1} \text{m}^{-1}$ mediated by weakly-guided pressure waves in InGaAsP. This leads to SBS gain coefficients as high as $737 \pm 54~\text{W}^{-1} \text{m}^{-1}$, observed in a mature, foundry-accessible photonic integration platform.
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All authors Riley te Morsche, Lukas Puts, Weiming Yao, David Marpaung

Superconductivity

Emergent magnetic pseudogap from phase fluctuations and hierarchy of scales in two-dimensional superconductors

Xu-Cheng Wang and Yang Qi

Preformed pairs and phase fluctuations are believed to play a vital role in predicting the charge pseudogap in the normal state of two-dimensional superconductors. In this work, we extend this idea and further identify the emergent magnetic pseudogap from pure phase fluctuations without invoking any competing order. We examine the NMR relaxation rate $1/T_1T$ by evaluating the bubble contribution and leading-order vertex correction within perturbation theory. It is found that the magnetic pseudogap, manifesting as a smooth suppression of $1/T_1T$ in the normal state, is characterized by a temperature scale $T_\text{mPG}$ distinct from the superconducting gap $\Delta_\text{SC}$ and transition temperature $T_c$. The onset scales of both charge and magnetic pseudogap are dominated by the competition of BKT correlation length $\xi(T)$ and BCS coherence length $\xi_\text{BCS}$. Moreover, the vertex correction is shown to be irrelevant for $d$-wave pairing, while it becomes prominent in $s$-wave systems and drives a coherent enhancement of $1/T_1T$ at lower temperatures just above $T_c$. We attribute this normal-state enhancement of $1/T_1T$ to the diverging coherence peak at the $s$-wave superconducting gap edge, which shares the same spirit as the celebrated Hebel-Slichter peak in the BCS theory. Analogous to the coherent Hebel-Slichter peak, regularization by Fermi-liquid-like scatterings is important and is characterized by a scattering length $\ell$. The normal-state coherent enhancement of $1/T_1T$ is hence described by the competition of $\xi(T)$ and $\ell$, through which the coherence scale $T_\text{coh}$ is determined. As a result, the complete evolution of $1/T_1T$ is understood quantitatively in a unified picture as the interplay among hierarchy of scales $\xi(T)$, $\xi_\text{BCS}$ and $\ell$.
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General Relativity and Quantum Cosmology

Testing the spin-induced multipole moments of compact binary coalescences using the flexible theory-independent framework

Elise M. Sänger, Alessandra Buonanno, Ajit Kumar Mehta et al. (+1 more)

According to the no-hair theorem, the multipole moments of an electrically neutral black hole in general relativity are entirely determined by its mass and spin. However, this is not in general true for compact objects: The multipole moments of neutron stars or exotic compact objects can depend on their formation history and internal processes, which are encoded in an equation of state. Furthermore, their spin-induced multipole moments differ from those of black holes of the same mass and spin, leaving an imprint on the dynamics and emitted gravitational waves of the binary. Gravitational waves can thus be used to test the nature of compact binary coalescences. Here, we present a test of the spin-induced quadrupole and octupole moments of compact objects based on the flexible theory-independent (FTI) framework. FTI is a parameterized inspiral test of general relativity which enables the addition of post-Newtonian coefficient deviations to the gravitational-wave phase of a generic aligned-spin frequency-domain waveform model. We use this test on synthetic signals to study the measurability of spin-induced quadrupole and octupole moments. Next, we apply the test to a subset of signals observed by the LIGO-Virgo-KAGRA Collaboration. Lastly, we present forecasts for next-generation ground-based detectors, such as Einstein Telescope and Cosmic Explorer. Our estimates suggest that these detectors will be capable of placing stringent constraints on the spin-induced quadrupole and octupole moments of $\mathcal{O}(10^{-2})$ and $\mathcal{O}(10^{-1})$ respectively, which is two orders of magnitude tighter than current constraints, and thus on the nature of black holes in a compact binary coalescence.
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All authors Elise M. Sänger, Alessandra Buonanno, Ajit Kumar Mehta, Jan Steinhoff

Mathematical Physics · Cross-listed from math.PR

Negative association of Busemann functions in exponential last-passage percolation

Erik Bates and Xiao Shen

One hallmark of exactly solvable KPZ random growth models is product-form invariant measures. In the setting of exponential last-passage percolation (LPP), this corresponds to the independence of Busemann increments along any down-right path. However, this independence breaks down when multiple asymptotic directions are considered simultaneously, owing to the fact that jointly invariant measures are not jointly product-form. This paper shows that the failure of independence is one-sided: Busemann increments across arbitrary directions are negatively associated. As an application, we derive an exponential concentration inequality for sums of Busemann increments on the diffusive scale, even when the increments are not independent. While our argument relies on a Burke property that is special to exponential weights, all other proof ingredients$\unicode{x2014}$including hidden LPP monotonicities and braid relations for queueing maps$\unicode{x2014}$hold for arbitrary weights.
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High Energy Astrophysical Phenomena

Search for gamma-ray spectral lines from dark matter annihilation with the H.E.S.S. Inner Galaxy Survey

H.E.S.S. Collaboration, F. Aharonian, H. Ashkar et al. (+116 more)

Spectral gamma-ray line features are expected as key signatures from dark matter (DM) annihilations of TeV-scale particle DM. Observations of the Galactic Centre with atmospheric Cherenkov telescopes are unique to probe thermal-relic TeV particle DM, well beyond the reach of direct detection and collider searches. We report here on the search for line signals in very-high-energy gamma rays using data from the Inner Galaxy Survey, consisting of 546 hours of H.E.S.S. observations of the inner few degrees of the Galactic Centre. No significant signal is detected. We then compute the exclusion limits on the annihilation line cross section $\langle \sigma v \rangle_{\rm line}$, with a two-dimensional log-likelihood ratio test statistics, exploiting spectral and spatial features of the DM signal. Assuming an Einasto DM density profile for the Milky Way, our results provide the most constraining limits so far, reaching $\langle \sigma v \rangle_{\rm line} = 2.3$ $\times$ $10^{-28}$ and $2.4 \times$ $10^{-27}$ cm$^3$s$^{-1}$ for DM masses of 1 and 10 TeV, respectively. The present limits are used to constrain the widely searched Wino, Higgsino and Quintuplet models. For the first time, thermal Higgsino DM is probed for DM Milky Way models.
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All authors H.E.S.S. Collaboration, F. Aharonian, H. Ashkar, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, K. Bernlohr, M. Bottcher, C. Boisson, J. Bolmont, F. Brun, B. Bruno, T. Bulik, C. Burger-Scheidlin, S. Casanova, J. Celic, M. Cerruti, A. Chen, M. Chernyakova, J.O. Chibueze, O. Chibueze, B. Cornejo, G. Cotter, J. de Assis Scarpin, M. de Bony de Lavergne, M. de Naurois, E. de Ona Wilhelmi, A. G. Delgado Giler, J. Djuvsland, A. Dmytriiev, K. Egberts, K. Egg, C. Escanuela Nieves, M. D. Filipovic, G. Fontaine, S. Funk, S. Gabici, J.F. Glicenstein, J. Glombitza, P. Goswami, B. Hess, J.A. Hinton, W. Hofmann, T. L. Holch, M. Holler, M. Jamrozy, F. Jankowsky, I. Jaroschewski, I. Jung-Richardt, K. Kasprzak, K. Katarzynski, D. Kerszberg, B. Khelifi, N. Komin, K. Kosack, D. Kostunin, R.G. Lang, S. Lazarevic, A. Lemiere, J.-P. Lenain, P. Liniewicz, A. Luashvili, J. Mackey, D. Malyshev, D. Malyshev, V. Marandon, M. Meyer, A. Mehta, A.M.W. Mitchell, R. Moderski, L. Mohrmann, A. Montanari, E. Moulin, J. Niemiec, L. Olivera-Nieto, M.O. Moghadam, S. Panny, R.D. Parsons, U. Pensec, G. Puhlhofer, A. Quirrenbach, M. Regeard, A. Reimer, O. Reimer, I. Reis, H. Ren, B. Reville, F. Rieger, G. Roellinghoff, G. Rowell, B. Rudak, K. Sabri, V. Sahakian, H. Salzmann, A. Santangelo, M. Sasaki, F. Schussler, J.N.S. Shapopi, W. Si Said, S. Spencer, L. Stawarz, S. Steinmassl, T. Takahashi, T. Tanaka, A.M. Taylor, G. L. Taylor, T. Unbehaun, C. van Eldik, M. Vecchi, C. Venter, J. Vink, T. Wach, S.J. Wagner, A. Wierzcholska, M. Zacharias, A. Zech, W. Zhong, F. Bradascio

General Relativity and Quantum Cosmology

Multiscale probing of a Hernquist-type environmental black hole spacetime with the Sgr A* shadow and S2 orbital dynamics

Lai Zhao, Meirong Tang, Zheng-Wen Long et al. (+1 more)

The supermassive black hole Sgr A* at the Galactic center provides a unique opportunity to probe the distribution of environmental matter around black holes. In this work, we adopt the Hernquist-type environmental black hole spacetime, a non-vacuum exact solution of the Einstein field equations, as its gravitational model to describe the joint gravitational field of the black hole and its surrounding matter, with environmental effects characterized by the dimensionless compactness $C$ and the characteristic scale $\alpha$. We combine black hole shadow data with two sets of S2 star data provided by Do et al. and Gillessen et al., and constrain the model parameters using the Markov chain Monte Carlo method. At the 95% credible upper limit, the shadow-only data constrain $C < 1.498\times10^{-1}$.but provide no effective constraint on $\alpha$. The two S2 datasets yield $C<5.239\times10^{-5}$ and $C<1.303\times10^{-4}$, respectively, with $\alpha$ exhibiting a bimodal structure in both cases. After combining the shadow and S2 star data, the $C$ upper limits are tightened to $C<3.760\times10^{-5}$ and $C<1.073\times10^{-4}$, respectively. These results indicate that current observations rule out highly compact configurations of the environmental halo, while the obtained constraints are consistent with the typical compactness range of matter halos. However, $\alpha$ still exhibits a significant bimodal degeneracy, indicating that current observations are insufficient to uniquely determine the radial distribution of the environmental halo. Future observations of multiple stellar orbits may provide further insights into the radial structure of the environmental halo.
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All authors Lai Zhao, Meirong Tang, Zheng-Wen Long, Zhaoyi Xu

Accelerator Physics

RF cavity design and beam loading effects in the rectilinear cooling channel for a muon collider

C. Barbagallo, A. Grudiev, D. Merenich et al. (+2 more)

High-gradient normal-conducting RF cavities are crucial components of the rectilinear cooling channel in a muon collider, providing the accelerating field necessary to sustain the rapid six-dimensional ionization cooling essential to achieve high luminosity. To reach this goal, a muon collider requires approximately $10^{12}$ muons per bunch. At such high beam intensities, beam loading induced by bunch-driven wakefields can significantly reduce the cavity accelerating gradient and compromise beam stability. This paper focuses on the conceptual RF design and beam-induced effect analysis of copper cavities with so-called beam windows developed to meet the beam dynamics requirements of the rectilinear muon cooling channel. We first present the design and optimization of the cavities, evaluating their RF performance and power requirements. Thereafter, we analyze cavity wakefields and beam loading effects, proposing a new numerical method for their compensation, which takes the transverse distribution of the beam into account.
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All authors C. Barbagallo, A. Grudiev, D. Merenich, X. Lu, T. Luo

Astrophysics of Galaxies

A Review of Galaxy Quenching – Part I: Defining the Problem and Observational Results

Asa F. L. Bluck

The goal of this review article series is to provide a comprehensive overview of galactic star formation and quenching from both an observational and theoretical perspective. Drawing on a vast quantity of literature, we attempt to answer a deceptively simple question: why do galaxies cease forming stars? In Part I, we concentrate on observational results, especially from the past two decades, where there have been enormous advances made towards answering this fundamental question. In Part II we focus on theory and simulations, including discussion of direct observational tests thereof. Observationally, the advent of wide-field spectroscopic galaxy surveys, spatially resolved spectroscopy, high resolution sub-mm and radio observations, X-ray observations, the Hubble Space Telescope (HST), and most recently the James Webb Space Telescope (JWST) have all contributed significantly to our empirical knowledge of star formation and its demise in galaxy quenching. We discuss the fundamental problems which quenching aims to solve, various routes to identifying quiescent galaxies in observations, observational constraints on quenching from studies of galaxy populations, and the spatially resolved view of quenching. We end this part of the review with a detailed discussion of the latest results on galaxy quenching at the high redshift frontier from JWST observations.
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Quantum Physics

Origin of Long-Lived Nuclear Spin States and Coherences in Aliphatic Chains Revealed by Relaxation Theory

Danil A. Markelov and Kirill F. Sheberstov

Delocalized long-lived states (LLSs) and collective zero-quantum long-lived coherences (LLCs) in aliphatic chains provide a promising route for preserving nuclear spin order with lifetimes that exceed the conventional $T_1$ and $T_2$ relaxation times, respectively. Their extended lifetimes make them attractive for applications including hyperpolarization storage, ligand-observed drug screening based on the loss of longevity upon binding to a target protein, and quantum information processing exploiting the collective properties of many-body spin systems. Although LLSs and LLCs have been observed experimentally in methylene networks, their origin and general structure in chains of arbitrary length have remained unclear. Here we show that these relaxation-protected modes follow directly from Redfield relaxation theory. Specifically, we construct the long-lived subspace, i.e., the zero-eigenvalue subspace of the relaxation superoperator associated with the dominant intra-pair dipole–dipole relaxation mechanism. The long-lived subspace contains $2^N-1$ independent non-trivial operators, which excludes the identity operator, where $N>1$ is the number of $-\mathrm{CH}_2-$ groups in the chain. In achiral molecules, conservation of the global intra-pair permutation parity restricts experimental access to at most $2^N-2$ of these operators, whereas in chiral molecules this parity is not conserved, making up to $2^N-1$ long-lived operators accessible. We further develop a general framework for constructing both LLSs and LLCs in aliphatic chains containing an arbitrary number of $-\mathrm{CH}_2-$ groups in achiral molecules, and illustrate the approach explicitly for chains with $N=2$, 3, and 4 methylene groups.
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Mesoscale and Nanoscale Physics

Perfect absorption by metal-contacted two-dimensional systems with ultra-proximate reflectors

Kirill Kapralov, Vladislav Atlasov, Alina Khisameeva et al. (+2 more)

Electromagnetic absorbance by most two-dimensional electron systems is typically well below unity, which hinders both practical applications in photodetection and fundamental studies of their optical properties. Here, we show that a periodic structure comprised of narrow two-dimensional sections connected with wide perfectly conducting metal sections enables large absorbance. It reaches 50 % provided the filling factor by the two-dimensional system $f$ equals its dimensionless conductivity $\eta=\sigma Z_0/2$, where $Z_0$ is the free-space impedance. The absorbance is further raised to 100 % if the periodic structure is placed above a perfectly conducting electromagnetic reflector, and provided $f=2\eta$. Surprisingly, the optimal distance between two-dimensional system and reflector may fall well below the quarter of incident wavelength $\lambda_0/4$, which was assumed as conventional absorption enhancement condition in optics. For low filling factors $f\ll1$, large dielectric constants of the substrate, and grating periods comparable with $\lambda_0$, the optimal distance to reflector tends to zero. Above the critical values of the grating geometrical parameters, the absorbance maximum ceases to exist. The critical behavior manifests as a large-amplitude resonance in 'dirty' two-dimensional system with purely real conductivity, while enhancement of carrier momentum relaxation time lowers the resonant peak. Such resonance mimics the plasmonic one, but does not rely on high electron mobility.
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All authors Kirill Kapralov, Vladislav Atlasov, Alina Khisameeva, Viacheslav Muravev, Dmitry Svintsov

Mathematical Physics

Topological defects in reflection positive topological field theories

Lukas Müller

Topological defects in quantum field theories are believed to assemble into higher categories with extra structure. This has been made precise for defects in $2$- and $3$-dimensional oriented topological quantum field theories by Davydov, Kong, and Runkel and by Carqueville, Meusburger, and Schaumann, respectively. In this paper we study the extra structure present on these categories when the topological field theory is additionally reflection positive. We define reflection defect TQFTs as symmetric monoidal functors out of a defect bordism category that intertwine orientation reversal with complex conjugation; they are reflection positive if they satisfy an additional positivity condition. Our main result is that in two dimensions the bicategory of defects $\mathcal{T}_\mathcal{Z}$ associated to a reflection defect TQFT carries the natural structure of an $O(2)$-dagger bicategory, a structure we define explicitly. If the theory is reflection positive, $\mathcal{T}_\mathcal{Z}$ can be equipped with additional structure closely related to the definition of a 3-Hilbert space (the two agree up to some finiteness and completeness conditions).
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Quantum Gases

Observation of far-from-equilibrium scaling in the transient dynamics of 2D quantum magnets

Fabio Bensch, Umberto Borla, Federico Balducci et al. (+7 more)

The transient regime of far-from-equilibrium quantum many-body dynamics lacks the established organizing principles that universality and scaling provide in equilibrium. It is least understood for two-dimensional short-range interacting systems, where mean-field arguments are not expected to hold, controlled theoretical descriptions are few, and fluctuations are strong. Here we investigate the quench dynamics of the transverse-field Ising model using programmable Rydberg-atom arrays realizing honeycomb, square, kagome, and triangular lattices. Starting from a fully magnetized state, we observe a pronounced softening of the dominant collective magnetization oscillation accompanied by a maximum in the damping rate, signaling a crossover between interaction- and field-dominated transient dynamics. Even though the microscopic lattice geometries are different, both the oscillation frequencies and the damping rates collapse onto common curves after being rescaled by the coordination-number-weighted interaction strength. Our findings show that a mean-field description effectively reproduces the magnetization oscillations. The importance of correlated quantum fluctuations is underlined by the failure of the discrete truncated Wigner approximation to predict the damping for strong interactions, while tree-tensor-network simulations reproduce the dynamics accurately. These results reveal a robust scaling regime governing the transient dynamics of short-range interacting two-dimensional quantum magnets. They reveal that the dominant transient dynamics is governed by a simple collective description despite the presence of strong quantum fluctuations — an important insight in the quest to uncover organizing principles in far-from-equilibrium quantum matter.
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All authors Fabio Bensch, Umberto Borla, Federico Balducci, Philip Osterholz, Shuanghong Tang, Silpa Baburaj Sheela, Anushya Chandran, Roderich Moessner, Jad C. Halimeh, Christian Groß

Cosmology and Nongalactic Astrophysics

Redshift Dependence of $H_0$ Dipole in Pantheon+ Supernovae

M.H. Jalali-Kanafi, E. Ó Colgáin, S. Pourojaghi et al. (+1 more)

We examine the dipole structure in the local cosmic expansion rate $H_0$ using the Pantheon+ compilation of Type Ia supernovae. We reconstruct directional maps of $H_0$ across the sky within the low-redshift regime, $z_{\rm min} < z < 0.2$, evaluated in the CMB rest frame. To perform a tomographic analysis, we choose 10 different values for $z_{\rm min}\in [0.015 , 0.045]$ range. We find a dipole amplitude $A_{\rm dip}=1.16\pm0.28\ {\rm km/s/Mpc}$ for the lowest bin, monotonically decreasing to $A_{\rm dip} =0.35\pm0.52\ {\rm km/s/Mpc}$, as we increase $z_{\rm min}$. Since $A_{\rm dip}$ is positive-definite, by construction $A_{\rm dip} > 0$ even in an isotropic universe, thus to assess the statistical significance, we compare to $A_{\rm dip}$ generated from 1000 Monte Carlo simulations based on the $\Lambda$CDM model and the same redshift ranges. Our results reveal a $2-3\sigma$ dipole pattern (depending on how the significance level is computed) for $z_{\rm min}\lesssim 0.032$. For redshift thresholds where the signal remains statistically significant ($>2\sigma$), the inferred dipole direction points close to Shapley supercluster and CMB dipole directions. As $z_{\rm min}$ increases, the dipole amplitude diminishes in line with expectations of a higher redshift isotropic Universe, but the difference in maximal antipodal $H_0$ determinations, $\Delta\text{H}_0^{\rm max}$, retain a signal of an anisotropy that disappears in the dipole ansatz. The decreasing statistical significance of all estimators with increasing $z_{\rm min}$ suggests that any $H_0$ dipole is a low-redshift feature.
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All authors M.H. Jalali-Kanafi, E. Ó Colgáin, S. Pourojaghi, M.M. Sheikh-Jabbari

Quantum Physics

Existence of Kraus decomposition in infinite dimension via strongly-convergent direct process tomography

Paul E. Lammert

An algorithm is presented for Kraus decomposition of a completely positive operator over separable (countably-infinite-dimensional) Hilbert spaces, together with an elementary proof that the generated sum convergences in strong-operator topology. This improves on the standard, nonconstructive, proof by fusing the abstract problem with practical process tomography. Kraus operators are generated one-by-one, each having one more guaranteed zero matrix entry than the previous one. In this way, the stream of outputs of the algorithm provides a coherent family of Kraus decompositions of restrictions of the target CP map to ever-larger subspaces.
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Quantum Physics

Atomic correlation effects in collapse-induced spontaneous radiation

Simone Manti, Nicola Bortolotti, Lajos Diósi et al. (+2 more)

Collapse models introduce stochastic and nonlinear modifications in the quantum dynamics, predicting observable effects, such as spontaneous radiation from charged particles, which can be used to constrain their parameters. Recently, attention has focused on the 1-100 keV energy range, where the wavelength of the emitted photons becomes comparable to atomic dimensions, making the emission sensitive to atomic structure and leading to model-dependent behaviors that enable their discrimination. Here, we derive a general expression for the spontaneous emission rate for arbitrary noise, providing a framework that systematically incorporates the atomic structure through the radial distribution of the emitters, modulated by the specific collapse model. The formalism recovers previous results in the appropriate limits and naturally includes new low-energy effects, such as cancellation mechanisms arising from charge correlations. We evaluate the rates for germanium and xenon within the Diósi-Penrose and Continuous Spontaneous Localization models, showing how these correlations modify the predicted emission rates. This approach provides a unified framework to account for atomic effects and enables more robust, material-dependent experimental constraints on collapse model parameters.
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All authors Simone Manti, Nicola Bortolotti, Lajos Diósi, Kristian Piscicchia, Catalina Curceanu

Optics

Fast Ptychographic Near-Field Computed Tomography

Sami Wirtensohn, Silja Flenner, Imke Greving et al. (+13 more)

Near-field X-ray ptychography enables quantitative three-dimensional imaging with nanometer-scale resolution, but its broader application is limited by long acquisition times - often necessitating cryogenic or vacuum environments - and demanding sample preparation procedures. In this paper, we present a flexible near-field ptychography setup that operates under ambient conditions and features an adjustable geometry for different sample sizes and resolution requirements. By replacing stepwise angular acquisition with a fly-rotation sample motion, the scanning overhead is reduced by a factor of 11, drastically lowering the tomographic scan time. To address the bottleneck in sample preparation, we also introduce a sample milling machine that enables fast preparation of specimen pillars with diameters down to 20 um. By lowering both preparation effort and measurement time while maintaining high spatial resolution, the presented system overcomes key limitations of near-field ptychography and makes quantitative X-ray nanotomography substantially more accessible for biological research.
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All authors Sami Wirtensohn, Silja Flenner, Imke Greving, Jens Brehling, Hilmar Burmester, Dominik John, Sara Baggio, Franziska Hinterdobler, Maximiliane Wojke, Kritika Singh, Benedikt J. Daurer, Johannes Hagemann, Frank Seiboth, Sara Savatovic, Fritz Vollrath, Julia Herzen

Statistical Mechanics

Distribution of the Radius of Gyration for an ISAW

Antony Lesage, Vincent Dahirel, Jean-Marc Victor et al. (+1 more)

We aim at calculating an explicit expression for the finite-size probability distribution of the radius of gyration $R$ of an Interacting Self-Avoiding Walk (ISAW), as a function of chain length $N$ and monomer-monomer interaction energy $\varepsilon$. We first derive the explicit free energy expression for a non-interacting Self-Avoiding Walk, introducing a new natural scale variable $t = \rho^g$ expressed as a power of the density $\rho$. Then, thanks to a cumulant expansion approach introduced by Lhuillier, Victor and coworkers, we extend it to the interacting case, capturing both the coil-globule transition and finite-size corrections to scaling, including entropic and surface-energy contributions. The radius of gyration distribution determined by the new free energy expression is then compared, using Bayesian inference to estimate the model parameters, to results from extensive Monte Carlo simulations of three-dimensional ISAWs, showing excellent agreement except very close to the $\Theta$-point, where finite chain lengths limit the accessible scaling regime. This validates our resulting free energy expression and allows us, as an application, to construct a phase diagram of the coil-globule transition.
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All authors Antony Lesage, Vincent Dahirel, Jean-Marc Victor, Maria Barbi

Statistical Mechanics

Statistical stability of random potentials to thermal and quantum activation

Luis Filsinger and Roland Willa

In numerous physical, chemical, and biological systems the dynamics can be reduced to the motion of state variables in a complex potential landscape. In case the manifold is known, the motion and response of the embedded object can be described deterministically up to stochastic effects usually associated with a noise. In contrast, if the manifold is unknown, the static and dynamic response of the state variable may be used as a spectroscopic tool to characterize the potential landscape. Inspired by a seminal work of L.\ Embon and co-workers, [Sci.\ Rep.\ 5, 7598 (2015)] we investigate the statistical properties of potential minima, in particular, their stability to thermal and quantum activation. For Gaussian random manifolds, we derive an algebraic expression to evaluate the statistical probability of the potential character (value, slope, curvature, ...). With this tool, we compute the expectation value for the rate of thermal and quantum activation and link these findings to the principal characteristics of the Gaussian potential, i.e., its Green's function. This link provides the opportunity to access information on the potential's Green's function by studying the activation behavior of an object in this manifold.
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Fluid Dynamics

Autoregressive rollout error in latent-space reduced-order models of bluff-body wakes is accumulated phase drift

Suvam Samanta and Sachidananda Behera

Autoregressive reduced order models suffer from compounding long horizon rollout errors, typically treated as unstructured noise. We demonstrate that for bluff body wakes across Re=100 to 800, this rollout error is highly structured and reveals what these models actually learn. For a convolutional autoencoder LSTM model, 95 % to 98% of the error is pure phase error, peaking sharply at the vortex shedding frequency. The network reproduces the attractor geometry almost exactly, matching limit cycle amplitudes within 0.15%, but traverses the cycle at slightly the wrong rate. This timing error, accumulating to just a few thousandths of a cycle over the entire rollout, drives the long horizon error even while one step validation errors appear virtually perfect. Because phase error drifts linearly, it can be corrected offline without retraining using just one parameter per latent coordinate, fitted on a short calibration window. The signal to noise ratio of this phase fit serves as a diagnostic that reliably predicts correction success (r=0.85 across 50 networks). While simple periodic baselines match this performance on stationary limit cycles, they fail by over an order of magnitude when applied to wakes driven by slowly varying inflows. Conversely, our phase correction requires only phase coherence, successfully removing roughly half of the rollout error during non stationary flow.
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Quantum Physics

Ultrafast quantum gate operations in a Kramers-Henneberger atom Qubit

A. Tasnim Aynul, C. Li, L. Cruz Rodriguez et al. (+1 more)

We propose and demonstrate the Kramers-Henneberger KH) atom as a novel qubit platform for ultrafast single-qubit gate operations. In the KH frame, the time-averaged strong laser field engineers a double-well potential whose two lowest eigenstates define the qubit basis, so that the computational structure is created and maintained by the driving field itself. A weak resonant control field drives coherent gate operations: full time-dependent Schrödinger equation simulations with the complete time-dependent KH potential confirm a Z gate and S gate of the order of femtoseconds, six orders of magnitude faster than laser-driven superconducting qubit gates. Decoherence characterisation gives longer decoherence times than those required for the gate operations. The complete six-gate single-qubit set is demonstrated in the time-averaged two-level limit, with strong agreement between the full and time-averaged descriptions confirming that fidelity is limited by structured leakage rather than stochastic decoherence. In principle, this is an error channel suppressible through pulse engineering. These results constitute the first demonstration of coherent single-qubit gates in a strong-field setting, with a clear pathway toward attosecond-scale operations.
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All authors A. Tasnim Aynul, C. Li, L. Cruz Rodriguez, C. Figueira de Morisson Faria

General Relativity and Quantum Cosmology

Anomaly quenching and dynamical cooling of Hawking evaporation in Horndeski gravity

Amogh Srivastav and S. Shankaranarayanan

We investigate the semiclassical Hawking evaporation of a two-dimensional Callan-Giddings-Harvey-Strominger (CGHS) black hole perturbed by first-order Horndeski scalar-tensor couplings. By evaluating the exact scalar curvature invariants, we demonstrate that coordinate singularities near the apparent horizon parametrize a physical deformation of the surface gravity while preserving a strictly regular event horizon. In the linear-order $\gamma_3 \Phi X$ coupling sector, the surface gravity and correspondingly the Hawking temperature decreases dynamically as the black hole loses mass. Extrapolating this cooling effect via a resummed temperature equation suggests that evaporation halts, potentially leaving behind a stable, macroscopic cold remnant at the boundary of perturbative control. Utilizing both the conformal trace anomaly and the Robinson-Wilczek gravitational anomaly, we establish that the asymptotic radiation flux identically reflects this geometric shift. Consequently, the fine-grained entanglement entropy of the Hawking radiation departs from linear growth and transitions to an asymptotic logarithmic regime. This indicates that quantum information may be permanently retained within the remnant, altering the standard semiclassical Page curve without requiring a breakdown of horizon regularity.
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Quantum Physics

Exploring the Relaxation Landscape of a 2D Quantum Magnet on a 256-Qubit Processor

Tiago Mendes-Santos, Joseph Vovrosh, Sergi Julià-Farré et al. (+33 more)

How quantum matter relaxes far from equilibrium is a central open problem in many-body physics, and one for which analog quantum simulators are well positioned to move from confirming theory to discovering new physics. Here, we use a two-dimensional Rydberg atom array of 256 qubits to map the relaxation landscape of the two-dimensional transverse-field Ising model across its phase diagram. Beyond the expected rapid thermalization, we identify two further regimes. The first is a prethermal regime whose dynamics are governed by an effective XY model. The second, and most unexpected, is a crossover regime characterized by a slowdown in relaxation. This slowdown occurs precisely where state-of-the-art classical tensor-network methods lose control at late times, whereas the quantum simulation remains consistent across system sizes. These results establish Rydberg atom arrays as a platform for scientific discovery in nonequilibrium quantum many-body dynamics.
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All authors Tiago Mendes-Santos, Joseph Vovrosh, Sergi Julià-Farré, Dorian Claveau, Guillaume Villaret, Lucas Béguin, Lucas Leclerc, Laurin Brunner, Wladislaw Krinitsin, Matthias Hecker, Fergus Hayes, Boris Albrecht, Lilian Bourachot, Clémence Briosne-Frejaville, Antoine Cornillot, Julius de Hond, Djibril Diallo, Clément Dupays, Robin Dupont, Thomas Eritzpokhoff, Loïc Henriet, Lucas Lassablière, Arvid Lindberg, Yohann Machu, Hadriel Mamann, Thomas Pansiot, Julien Ripoll, Bruno Ximenez, Henrique Silvério, Joseph Tindall, Markus Schmitt, Markus Heyl, Adrien Signoles, Constantin Dalyac, Antoine Browaeys, Alexandre Dauphin

General Relativity and Quantum Cosmology

New Universal Relations for Magnetized Neutron Stars

Byon N. Jayawiguna, Siddarth Ajith, Takuya Katagiri et al. (+2 more)

Unlike the neutron-star mass–radius relation, which depends sensitively on the internal stellar structure through the equation of state of dense nuclear matter, certain neutron-star properties obey approximately universal relations that exhibit only weak dependence on the equation of state. In this paper, we explore new universal relations for magnetized neutron stars. We focus on a purely poloidal dipolar magnetic-field configuration and treat the effects of the magnetic field perturbatively to second order in the field strength. After appropriately normalizing the relevant quantities by the stellar mass and the magnetic-field strength at the pole, we first identify an exact universal relation between the magnetic dipole moment and stellar compactness. We then find approximate universal relations among the magnetic dipole moment, magnetically-induced stellar quadrupole moment, and ellipticity, with fractional variations due to the equation of state at the level of O(10%). We support these numerical findings with analytic estimates for Newtonian polytropes, which reproduce the observed behavior. Among the newly discovered relations, the one connecting the magnetic dipole moment and stellar quadrupole moment may be particularly useful for the analysis of gravitational-wave signals from binaries containing magnetized neutron stars.
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All authors Byon N. Jayawiguna, Siddarth Ajith, Takuya Katagiri, Kent Yagi, Piyabut Burikham

Plasma Physics

Electron-Scale-Driven Turbulence by Negative-Density-Gradient in NSTX

C. Clauser, J. Candy, J. Parisi et al. (+7 more)

Gyrokinetic simulations of an NSTX spherical-tokamak plasma reveal novel negative-density-gradient (NDG) drift waves at electron-gyroradius-scale that drive turbulent transport comparable to the experimental power flow. Linear simulations indicate that the dominant instability is a trapped-electron electron-scale tearing-parity mode driven mainly by negative electron density gradient, $a/L_{ne} \equiv - a/n_e \, (dn_e/dr) < 0$. Although thermal transport is mainly carried by transverse magnetic, $\delta A_{\parallel}$, fluctuations, the growth rate is sensitive to compressional magnetic fluctuations, $\delta B_{\parallel}$, differentiating these from standard microtearing modes (MTMs). Linear sensitivity analysis also reveals that the modes are most unstable at lower collisionality, consistent with the trapped-electron character. Electron-scale and multi-scale nonlinear simulations show that these modes can account for several megawatts of experimental power, with the latter suggesting that experimental gradients may lie at a bifurcation between distinct turbulence regimes.
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All authors C. Clauser, J. Candy, J. Parisi, T. Rafiq, W. Guttenfelder, G. Avdeeva, E. Belli, J. Berkery, I. Sfiligoi, E. Schuster

General Relativity and Quantum Cosmology

Quantum-cosmological corrections to inflationary spectra from Gaussian wave packets

Sebastien Sonet, Alessandro Tronconi and Giovanni Venturi

In the context of quantum cosmology, we study quantum entanglement in solutions of the Wheeler–DeWitt equation for a homogeneous inflaton–gravity system coupled to perturbations. The wave function describing the homogeneous degrees of freedom is entangled with the wave function describing the perturbations, and this may lead to potentially observable effects on the inflationary spectra. We restrict our analysis to two simplified models that admit a future de Sitter attractor, while neglecting non-adiabatic effects and contributions of order $\mathcal{O}(\hbar^2)$ in the Mukhanov–Sasaki equation. Analytical expressions for the resulting spectra are obtained by marginalising over the homogeneous inflaton variable and can be evaluated in regimes where reliable approximations are available. Small deviations from the standard semiclassical spectra are indeed generated, and these are significantly larger than the quantum-gravitational corrections usually considered in this context.
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Quantum Physics

Rate-Fidelity Control for Wide-Area Quantum Links

Connor Clayton, Cory Nunn, Quinn Carmack et al. (+4 more)

Quantum network links must distribute entanglement at high rates while satisfying application-specified fidelity demands. However, wide-area deployed fiber links suffer from polarization drift which destabilizes end-to-end fidelity and forces periodic compensation. Current deployments often use active stabilization with fixed control policies, and improvements generally stem from advances in quantum hardware. Meanwhile, software control remains relatively underexplored. Here, we formulate quantum link operation as a joint control problem over tunable rate-fidelity tradeoffs and uncontrollable link drift. From this framework, we construct a link control protocol that dynamically adapts source pump power and polarization compensation to maximize entanglement distribution rate subject to a minimum fidelity constraint. We evaluate the protocol through trace-driven simulations driven by data from a 64 km deployed optical fiber. Compared with optimized static policies, our adaptive controller improves mean entanglement distribution rate by 14% over a 24 hour trace, without requiring any offline policy optimization. Our results show that software-based physical layer control can provide a practical mechanism for improving near-term quantum link performance without requiring additional quantum hardware.
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All authors Connor Clayton, Cory Nunn, Quinn Carmack, Wayne McKenzie, Anne Marie Richards, Xiaodi Wu, Bobby Bhattacharjee