General Relativity and Quantum Cosmology
How Inflation Might Explain Large-Scale Anisotropy
Brett McInnes
Several recent observational analyses have suggested the possible existence of anisotropy in our Universe. It is often thought that this would contradict the inflationary picture. We have argued that this is not the case: if we relax the artificial restriction that spacetime torsion must be zero, then such anisotropies arise naturally, indeed almost inevitably, in a theory of torsional Inflation. This is seen most clearly if one uses a “$1\,+\,3\,$” analysis of a torsional spacetime, leading naturally to concepts of intrinsic torsion and extrinsic torsion. An anisotropic
quantum fluctuation of the inflaton leads to an extrinsic torsion field which is anisotropic and which grows throughout the inflationary era, even though the intrinsic geometry of the spatial sections is isotropised in the conventional manner. This leads to an anisotropic Hubble field at the end of Inflation. The anisotropy takes a very specific and characteristic form, which in principle could be observable on relatively short
cosmic scales. On the other hand, an unusual feature of torsional geometry leads to a short interval, early in the inflationary era, during which there is a torsion-induced energy flux, which leaves an anisotropic signal in superhorizon modes and thus ultimately at very large scales in the present Universe. Thus in principle torsion can explain anisotropies both on relatively short
cosmic scales and also at the largest scales.
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High Energy Physics (Experiment)
The Search Budget of the BSM Resonance Program
Theresa Reisch and Tobias Golling
Data-directed scans, anomaly searches and general searches probe many mass spectra at once, and for them the look-elsewhere effect sets the discovery bar. We count the trials factor of the ATLAS BSM resonance program in effective independent resolution elements, from public inputs alone, and then work out what a fully combinatorial scan would cost in the same units. The published record, summed over the 104 spectra it scans, amounts to $N_{\mathrm{trials}} = 7.9 \times 10^{3}$ looks, so a $5\sigma$ global discovery today costs a local $Z_{\mathrm{local}} = 6.55$. Scanning instead every mass built from up to four reconstructed objects, one event-level selection at a time and priced on Run 2 and Run 3 together, amounts to $3.6 \times 10^{5}$ looks and $Z_{\mathrm{local}} = 7.11$. A factor 46 more looks therefore costs $0.56\sigma$. If the trials factor cannot be enumerated because the
estimator is itself imperfect, as in machine-learning searches, two-stage unblinding is a safeguard against its spurious signals: at the defect rate measured for a published bump-hunting network it is the more sensitive procedure.
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Quantum Physics
Krylov Tomography and Finite-Uncertainty Certification of Exceptional-Point Dynamics
Aritra Ghosh and M. Bhattacharya
Exceptional points (EPs) can produce striking responses, but locating one does not reveal how much of its dynamics an excitation accesses, which responses a detector distinguishes, or whether a missing signal is absent or undetected. We introduce Krylov
tomography, a preparation- and measurement-aware framework that uses time-resolved data and models with stated uncertainty limits to answer these questions, while also bounding offset-induced departures from exact-EP behavior. As an explicit illustration of the general framework, we present finite-precision simulations of a red-sideband optomechanical model, whose second-moment coherence sector contains a third-order EP, certifying preparation-sensitive access to two and three directions. Krylov
tomography thus bridges EP structure and finite-precision measurements, providing a general framework for non-Hermitian systems.
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General Relativity and Quantum Cosmology
Galactic microlensing by Lobo-Parsaei-Riazi phantom wormhole: Paczyński light curves and probabilistic features
G.F. Akhtaryanova, R.Kh. Karimov, R.N. Izmailov et al. (+1 more)
Gravitational microlensing can provide a possible observational method for distinguishing between the signatures of massive and massless phantom wormholes. In this work, we consider
Galactic microlensing by the bounded Lobo-Parsaei-Riazi phantom wormhole (LPR), assuming source
stars located in the
Galactic Bulge and in the Large Magellanic Cloud (LMC). We derive the weak-field deflection angle up to fourth post-Newtonian order and compute the Einstein radius, Einstein-radius crossing time, and idealized point-source Paczyński-type light curves. We also estimate the optical depth and event rate in a simplified model in which the wormhole lenses are assumed to be gravitationally bound to the
Galaxy. The LPR parameter $\gamma$, which is related to the radial equation-of-state parameter by $\omega = 1/ \gamma$, affects the ADM mass, the Einstein radius, and the microlensing timescale. In the massive phantom branch $-1 < \gamma < 0$, the leading deflection term is proportional to $1/r$, and the resulting point-source light curves are Paczyński-like. The massless comparison case $\gamma = 1$ is qualitatively different because the leading $1/r$ term vanishes and gutters may appear. The idealized observational predictions are compared with those for a Schwarzschild black hole.
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All authors G.F. Akhtaryanova, R.Kh. Karimov, R.N. Izmailov, U.K. Khidirov
Earth and Planetary Astrophysics
Asymmetric Aerosol Distribution on the Terminators of the Warm Saturn WASP-69 b Revealed by JWST NIRISS/SOSS
Le-Chris Wang, Sagnick Mukherjee, Stephen P. Schmidt et al. (+16 more)
How aerosols form, are transported, and cycle between condensation and evaporation across
exoplanet temperature regimes remains poorly understood. Recent models and observations suggest that warm
giant planets near $800$–$1000$ K may span a transition between homogeneous and longitudinally heterogeneous aerosol distributions. We present a robust detection of aerosol asymmetry in a
giant planet with $T_{\rm eq}\lesssim1000$ K, using the $0.86$–$2.82~\mu$m JWST NIRISS/SOSS transmission spectrum of WASP-69 b. The evening limb shows prominent 1.4 $\mu$m H$_2$O absorption ($\Delta\mathrm{BIC}_{\rm H_2O}=+22.7$), whereas H$_2$O is not detected on the morning limb ($\Delta\mathrm{BIC}_{\rm H_2O}=-8.7$). Atmospheric
retrievals reveal significant aerosol opacity on both limbs, with high-altitude, optically thick clouds muting molecular features on the morning limb and lower cloud opacity allowing H$_2$O to emerge on the evening limb. The evening terminator is hotter by $304^{+62}_{-91}$ K, consistent with morning-limb condensates partially evaporating during transport toward the evening limb. This mechanism is independently verified with 3D general circulation models.
Stellar contamination or aerosols dominated by photochemical haze do not readily explain the asymmetry. From a limb-resolved analysis, we infer a
stellar-to-superstellar atmospheric
metallicity, with $\rm[M/H]=0.11^{+0.40}_{-0.46}$ from the
equilibrium retrieval and [O/H]$=1.38^{+0.44}_{-0.79}$ from the free
retrieval. We also detect an escaping metastable-helium tail extending to $3.08^{+0.50}_{-0.45}\,R_p$. WASP-69 b anchors the cooler edge of the emerging population of
planets with asymmetric aerosol distributions and suggests that substantial aerosol opacity may persist on both limbs across this transition.
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All authors Le-Chris Wang, Sagnick Mukherjee, Stephen P. Schmidt, Kevin B. Stevenson, Mei Ting Mak, Patrick McCreery, Harry Baskett, Carlos Gascón, David K. Sing, Katharine A. Bennett, Duncan A. Christie, Guangwei Fu, Mercedes López-Morales, Joshua D. Lothringer, Nathan J. Mayne, Lakeisha M. Ramos Rosado, Zafar Rustamkulov, Kevin C. Schlaufman, Kristin S. Sotzen
General Relativity and Quantum Cosmology
Finite-Momentum Kinetic Corrections to Viscous Tensor Perturbations in an Expanding Universe
Nishil Savla and Gurudatt Gaur
We study tensor perturbations propagating through a viscous relativistic medium in a spatially flat FLRW universe, with particular emphasis on the correction produced by spatial free streaming beyond a local causal relaxation model. We start from the relaxation-time Boltzmann equation used by Baym, Patil, and Pethick to describe the response of matter to a gravitational wave. In the zero-streaming limit, the tensor stress obeys a Maxwell-Cattaneo, or linear Muller-Israel-Stewart, relation. We then retain the spatial streaming term and evaluate the resulting angular response analytically for an ultrarelativistic isotropic medium. The resulting kinetic response is coupled to the tensor Einstein equation and solved numerically in a flat matter-plus-Lambda background, with comparison to the local MIS propagation model and an independent kinetic WKB calculation. For the illustrative normalization considered, the full numerical calculation produces a nonmonotonic correction to the tensor power transfer function, with a maximum of about 0.8 percent near x equal to 0.37 and a minimum of about minus 5.6 percent near x equal to 1.97. These features are stable under angular-resolution and ODE-tolerance tests and are reproduced by the kinetic WKB calculation. We also find a corresponding finite-momentum phase correction. The effect is a property of the specified single-relaxation-time kinetic model and should not be interpreted as a universal transport law.
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Quantum Physics
Multiplexing of Continuous-Variable and Discrete-Variable Quantum Key Distribution Systems over Fibered and Free-Space Channels
Mattia Sabatini, Edoardo Rossi, Matías R. Bolaños et al. (+7 more)
Future
quantum communication infrastructures will need to serve heterogeneous users on shared physical channels: short-range, high-throughput links favor Continuous-Variable
Quantum Key Distribution (CV-QKD), while long-reach, high-loss links remain the domain of Discrete-Variable QKD (DV-QKD). Wavelength-division multiplexing (WDM) of the two protocols on a common channel would address both regimes simultaneously, but their markedly different noise sensitivities make coexistence non-trivial and, to date, experimentally untested. Here we report the first simultaneous operation of two independent CV- and DV-QKD systems on a common optical channel, using standard C-band DWDM filters at 1550.12 nm (CV) and 1545.32 nm (DV). We demonstrate joint operation on both optical fiber and a 620 m urban daylight free-space link. On fiber, the two systems exhibit the expected complementarity, crossing over at 7.56 dB of channel loss where both deliver $\sim$1.43 Mbit/s; in daylight free-space, both sustain Mbit/s key rates under time-varying atmospheric attenuation. Across all configurations we observe no measurable multiplexing-induced penalty in QBER or excess noise. These results establish hybrid CV-DV WDM as a practical building block for heterogeneous
quantum communication networks, where metropolitan high-throughput users and long-reach backbone links can be served on a single physical infrastructure.
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All authors Mattia Sabatini, Edoardo Rossi, Matías R. Bolaños, Francesco Vedovato, Thomas Liege, Eleni Diamanti, Giuseppe Vallone, Paolo Villoresi, Yoann Piétri, Marco Avesani
Mathematical Physics · Cross-listed from math.PR
Conditioned Brownian motion and local equivalence of path ensembles
Tobias Schmidt
We study Brownian motion in R^d conditioned so that the time average of a continuous confining potential remains below a fixed level. On every fixed initial time interval, we prove that the conditioned process converges in total variation to the ground-state
diffusion associated with a suitable Schrödinger operator. We also obtain sharp asymptotics for the probability of the conditioning event, including bounded perturbations of the constraint. The proof is based on a local limit
theorem for the corresponding Feynman-Kac measures. Our results extend the previously known one-dimensional quadratic case to arbitrary finite dimension and a broad class of confining potentials, therefore resolving a
conjecture of Aurzada, Lifshits and Schickentanz. The presented approach also works when Brownian motion is replaced by suitable reversible Markov processes, including multidimensional Ornstein-Uhlenbeck processes, CIR processes and continuous-time Markov chains.
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Materials Science
Valley- and Spin-Dependent Electronic and Transport Properties of Two-Dimensional Altermagnetic Titanium-Based Chalcogenide Halides
Ruo-Yu Ning, Zhi-Hua Yan, Jin-Yang Li et al. (+2 more)
Altermagnets (AMs) combine fully compensated magnetization with momentum-dependent
spin splitting, yet intrinsic altermagnetic materials exhibiting exceptional valley characteristics remain scarce. Here, we identify monolayer titanium-based chalcogenide halides, Ti$_2X_2Y$ ($X$ = F, Cl, Br, I; $Y$ = O, S, Se, Te), as a new family of two-dimensional altermagnetic valley materials. These monolayers exhibit robust $d$-wave altermagnetic order, semiconducting band gaps, and pronounced
spin-polarized valley characteristics. We show that uniaxial strain breaks the valley degeneracy, inducing
giant valley polarization together with a tunable piezomagnetic response. An in-plane electric field generates noncollinear
spin currents, while
spin–orbit coupling gives rise to the anomalous
Hall effect, valley-selective linear dichroism, and the magneto-optical Kerr effect. These findings establish Ti$_2X_2Y$ monolayers as a versatile platform for exploring
spin- and valley-dependent electronic, optical, and transport phenomena in two-dimensional altermagnets.
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All authors Ruo-Yu Ning, Zhi-Hua Yan, Jin-Yang Li, Yong-Kun Wang, Si Li
Optics
Nonlinear tunnel oscillations of light in spherical Bragg resonators
Victor P. Ruban
A weakly nonlinear regime of radial tunneling is theoretically considered for a light wave in a spherical dielectric Bragg resonator containing a set of “shell” eigenmodes (both TE and TM) with different azimuthal numbers $l\geqslant 1$, which are concentrated near a defect of the Bragg structure, several layers away from the origin. Also, a single mixed radial mode with $l=1$ is located near the resonator center, either TM or TE. Nonlinearity of Kerr type in the main approximation is actual for the central mode only, while all the shell modes remain in the linear regime. The tunneling occurs between the central mode and the shell $l=1$ mode of the same
symmetry. Nontrivial part of the dynamics of optical field is described by a
Hamiltonian system of ordinary differential equations for complex vectors ${\bf C}_{1}(t)$ and ${\bf C}_{2}(t)$, which determine the magnitude and spatial orientation of the wave structures at the center and at the shell, respectively. Depending on “asymmetry parameter” of tunnel coupling, the system demonstrates different variants of nonlinear behavior.
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Materials Science
Mirror Chern insulators in two-dimensional altermagnetic Tc$_2$Cl$_2$O and Tc$_2$Br$_2$O
Rong Wang, Ruo-Yu Ning, Zhi-Hua Yan et al. (+1 more)
The interplay between altermagnetism and crystalline band
topology provides an intriguing avenue for realizing unconventional topological phases with distinctive
spin-dependent properties. Here, based on first-principles calculations and theoretical analysis, we identify monolayer $\mathrm{Tc}_2X_2\mathrm{O}$ ($X$ = Cl, Br) as a family of two-dimensional altermagnetic mirror Chern
insulators. In the absence of
spin–orbit coupling (SOC), both monolayers exhibit robust altermagnetism with mirror-
spin coupling and host two
symmetry-protected Weyl points in each
spin channel near the
Fermi level. The Weyl points in opposite
spin channels carry distinct mirror-
symmetry eigenvalues, $m_z=\pm i$. Upon inclusion of SOC, the Weyl points are gapped, and the two mirror sectors acquire opposite Chern numbers, ${\cal {C}}_{+}=1$ and ${\cal {C}}_{-}=-1$, resulting in a nonzero mirror Chern number ${\cal {C}}_m=1$. A low-energy $k\cdot p$ model captures the
symmetry protection of the Weyl points and elucidates their SOC-induced mass gaps and topological character. Furthermore, the resulting mirror Chern insulating phases host helical edge states within the bulk band gap and exhibit a quantized
spin Hall conductivity. Our work establishes a direct connection between altermagnetism and mirror Chern
topology and provides a promising platform for exploring unconventional topological and
spin-dependent phenomena in two-dimensional altermagnetic materials.
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All authors Rong Wang, Ruo-Yu Ning, Zhi-Hua Yan, Si Li
Soft Condensed Matter
Cooperative effects of membrane confinement and gelation on PEG crystallization pathway
Masaki Yoshida, Naoya Yanagisawa, Fumiya Kanie et al. (+5 more)
Lipid-coated microscale hydrogels provide confined, hydrated environments in which
polymer phase behavior can differ markedly from that in bulk. Here, we investigate the crystallization pathway of poly(ethylene glycol) (PEG) encapsulated in lipid-coated agarose microgels. Surprisingly, polarized-light microscopy reveals birefringence in the microgels under conditions where PEG remains non-crystalline in the corresponding bulk solution. The birefringence disappears upon heating and spontaneously reappears after further cooling or upon local mechanical stimulation. Infrared microspectroscopy demonstrates that the birefringent microgels contain crystalline PEG, whereas non-birefringent microgels contain PEG in an amorphous-like state, indicating the existence of a metastable precursor prior to crystallization. Furthermore, cooling below the phase-separation temperature produces PEG-rich domains preferentially near the membrane, suggesting that membrane wetting governs the spatial distribution of PEG before crystallization. Together, these results indicate that membrane confinement and agarose gelation cooperatively alter the local hydration environment of PEG, thereby stabilizing an amorphous-like precursor and redirecting the subsequent crystallization pathway. Our findings identify the coupling of membrane wetting and gelation as a key factor governing PEG crystallization in confined soft materials.
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All authors Masaki Yoshida, Naoya Yanagisawa, Fumiya Kanie, Hidemasa Teraoka, Ikki Morichika, Satoshi Ashihara, Tetsuya Hama, Miho Yanagisawa
Chemical Physics
A Comparative Study of Coherent and Action-Detected 2D Electronic Spectroscopies of a Multichromophore Photosynthetic System
Edoardo Amarotti, Ajeet Kumar, Luca Bolzonello et al. (+3 more)
Coherent two-dimensional electronic spectroscopy (C-2DES) is a powerful tool for resolving excitonic structure and dynamics in light-harvesting complexes with dense energy-level
manifolds. In contrast, action-detected 2DES has seen limited use on such systems, and its capacity to reveal electronic structure and dynamics remains unclear. Here we compare C-2DES and fluorescence-detected 2DES (F-2DES) on the major plant light-harvesting complex (LHCII) at 78 K. C-2DES resolves excitonic features and their spectral
evolution, mapping energy-transfer pathways. F-2DES shows strong cross-peaks, but these are largely time-invariant and dominated by incoherent mixing, obscuring the dynamics. C-2DES is therefore preferred for resolving ultrafast energy transfer in light-harvesting complexes and other large interacting networks. Combined, the two measurements directly quantify the suppression of population dynamics by incoherent mixing, confirming that nearly the entire LHCII trimer network contributes. We also identify pulse-shaper nonlinearities in F-2DES as spurious features, highlighting the need for rigorous artifact suppression.
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All authors Edoardo Amarotti, Ajeet Kumar, Luca Bolzonello, David Bina, Tõnu Pullerits, Donatas Zigmantas
High Energy Physics (Theory)
Tropical and Stringy Integrals for In-In Correlators
Song He, Xiang Li, Yong-Xiang Su et al. (+1 more)
We introduce tropical and stringy integrals for fixed-graph contributions to cosmological in-in correlators of conformally coupled scalars. The full-time representation factorizes into a graph-dependent vertex-space Laplace integral, with one real variable for each graph vertex, and an elementary edge-space Laplace integral, with one real variable for each internal edge. The vertex-space exponent is a sum of absolute values associated with sites and relative edge times; as a piecewise-linear function, it is the support function of the in-in zonotope. Each absolute value is also the tropical limit of a positive Laurent binomial. Retaining these binomials before tropicalization defines a finite-$\alpha'$ vertex-space stringy integral, so both the polytope and its stringy integral are read directly from the physical time integral. In the $\alpha' \to 0$ limit this integral becomes the normalized dual volume of the in-in zonotope, while the edge-space factor deforms independently into a product of beta integrals and restores the elementary propagator normalization. We derive the field-theory rational form from augmented-graph chambers, as well as exact finite-$\alpha'$ parallel-edge reduction, factorization formulas for edge-energy and partial-energy poles, and even descendant towers. As an alternative
geometric realization of fixed-graph correlators, we find an ambient Minkowski-sum and stringy-integral realization of the graph correlahedron for a tree graph as the so-called graph cubeahedron of its line graph. For completeness, we also record the logarithmic critical equations and generic reference degrees of the associated affine divisor arrangement.
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All authors Song He, Xiang Li, Yong-Xiang Su, Fan Zhu
Chemical Physics
Iterative Projection-Based Embedding Scheme Combined with Variational Quantum Eigensolver
Hongseok Choi, Kyungmin Kim and Young Min Rhee
Quantum embedding methods offer a promising route to extend
quantum chemical calculations to large multiscale systems by treating a chemically important subsystem at a high level of theory while describing its surrounding environment at an affordable level. The methods are also quite relevant for
quantum computing approaches based on hardware with limited resources. Here, we present an iterative projection-based
embedding framework combined with VQE, in which the environment density is allowed to respond self-consistently to the refined electronic structure of the embedded subsystem described by VQE. Unlike conventional one-shot approaches where the environment remains frozen after the initial orbital optimization, the proposed iterative scheme alternates between the VQE-level treatment of the subsystem and a mean-field-level refinement of the environment until mutual self-consistency is achieved. The convergence behavior of the scheme is first examined using several small test systems. Its practical applicability is then demonstrated with a composite system with a CH2NH molecule sandwiched by two benzene rings, with the C=N dihedral angle rotating from 0 to 90 deg. The iterative procedure consistently converges within ~10 iteration steps across all tested geometries, yielding energies below the conventional one-shot
embedding results. The converged results well reproduce the fully correlated reference energy employing the same active space, and the resulting potential energy surface with respect to the dihedral rotation is also in good agreement with the reference one. These results demonstrate that our iterative
embedding framework is numerically robust and physically sound, yielding a self-consistent and reliable treatment of inter-subsystem correlation. We expect that its formulation will be particularly compatible with the emerging paradigm of
quantum-classical hybrid computing.
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High Energy Physics (Experiment)
Heavy-flavour production and correlations in pp collisions: precision tests of pQCD and hadronisation with ALICE
Deependra Sharma and for the ALICE Collaboration
Heavy
quarks (charm and beauty) are predominantly produced in hard partonic scatterings, making their cross sections in
proton–
proton (pp) collisions calculable in perturbative
quantum chromodynamics (pQCD) and thus providing stringent tests of pQCD. Furthermore, the associated production of two charm
hadrons in a single collision offers a sensitive probe of multiparton interaction dynamics, distinguishing between single parton scattering (SPS) and double parton scattering (DPS) processes. In this contribution, preliminary measurements of
prompt D-
meson production are reported, together with the final results of the $\rm B^{0}$-
meson production cross section down to $p_{\rm T}$ = 1 GeV/$c$ at midrapidity. The rapidity dependence of B-
meson production is investigated by computing the ratio with respect to LHCb measurements at forward rapidity. The associated production of $\rm D^{0}$–$\mathrm{J}/\psi$ pairs in pp collisions at $\sqrt{s} = 13.6$ TeV is presented as well, where $\rm D^{0}$
mesons are reconstructed at midrapidity, while $\mathrm{J}/\psi$ candidates are measured at forward rapidity. These measurements are compared with pQCD calculations and phenomenological models, providing crucial constraints on heavy-
quark production, hadronisation, and multiparton interaction dynamics.
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High Energy Astrophysical Phenomena
Multi-scale Memory and Regime Shift in the Hyperactive Repeating FRB 20240114A
Wen-Long Zhang, Sheng-Lun Xie, Jun-Jie Wei et al. (+5 more)
We present a statistical analysis of FRB~20240114A, a hyperactive repeating fast
radio burst, based on 11,553 bursts detected by FAST over 214 days. Our main findings are fourfold. (1) On the most active day (MJD~60381, 3,197 bursts in 4.38 hr), event-rate coherence analysis reveals persistent correlated activity extending up to 3600~s, the longest reported for any repeating FRB, showing
memory persists even in intense bursting epochs. (2) The waiting-time distribution on this day is well described by three exponentials, whereas the full 214-day sample develops a threshold power-law tail, indicating burst statistics depend on the observational baseline, with long-range correlations emerging only over longer timescales, a hallmark of self-organized criticality. (3) Rescaled range (R/S) analysis of waiting times reveals a broken power law, with Hurst exponents $H_1=0.63\pm0.02$ (short-lag weak
memory) and $H_2=1.04\pm0.02$ (long-lag non-stationary drift). The break corresponds to $\sim$1 hour, consistent with the 3600~s coherence limit. R/S analysis of energies similarly exhibits a break ($H_1=0.60\pm0.01$, $H_2=1.10\pm0.05$) at a different lag, reinforcing that non-stationarity affects both temporal and energetic properties. (4) Energy distributions exhibit waiting-time-dependent slopes that are consistent with the full and daily samples, and the high-energy cutoff remains constant across waiting-time groups, suggesting that the maximum energy scale is an intrinsic source property. Together, these results establish a multi-scale
memory framework: the source behaves stochastically on short timescales but exhibits systemic non-stationarity over months, providing
benchmarks for burst models and highlighting the need for long-term, high-cadence monitoring to capture temporal complexity.
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All authors Wen-Long Zhang, Sheng-Lun Xie, Jun-Jie Wei, Di Xiao, Long-Xuan Zhang, Shuang-Xi Yi, Fa-Yin Wang, Xue-Feng Wu
Superconductivity
Internal cyclotron probe of the vertical polarizability of a surface-state electron on helium
Kirill Shulga
We study a surface-state electron on
liquid helium in a tilted
magnetic field. The tilt couples the cyclotron ladder to the vertical Rydberg-like subbands of the same electron and thereby realizes a self-coupled Landau-subband
Hamiltonian. In the far-detuned regime, the cyclotron line acquires a state-dependent shift described by standard second-order perturbation theory. The resulting expression identifies the cyclotron resonance as a direct probe of the dynamical polarizability of the vertical ladder. The theory is intrinsically multilevel. Exact diagonalization confirms a broad microwave window in which sizable state-dependent cyclotron shifts are expected while the system remains dispersive.
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High Energy Physics (Phenomenology)
Tracing Vacuum Hadronization with Conserved Currents
Weiyao Ke, Hai Tao Li, Wanchen Li et al. (+2 more)
We show that color triality constrains the nonperturbative states that screen a Wilson-line endpoint, allowing the joint flows of net electric charge,
baryon number, and strangeness to probe QCD
vacuum hadronization. Whether evaluated from resolved
hadrons in a jet initiated by a
quark of
flavor $f$ or from the corresponding charge correlators, these flows satisfy the Gell-Mann–Nishijima relation $\langle Q_{\rm flow}\rangle_f \simeq I_{3,f} +\frac{1}{2}\left( \langle S_{\rm flow}\rangle_f +\langle B_{\rm flow}\rangle_f \right)$, where $I_{3,f}$ is the third component of the initiating-
quark isospin. The net jet
baryon number, $\langle B_{\rm flow}\rangle_f\simeq \frac{r_{qq}}{1+r_{qq}}$, directly probes the relative probability of a diquark–antidiquark
vacuum excitation, with $r_{qq}$ the diquark-to-
quark production ratio. Thus, for $r_{qq}\ll1$, the
baryon number carried by the jet is substantially suppressed relative to the initiating-
quark value $B_f=1/3$. Likewise, the strange-to-light pair-production ratio, defined by $u\bar u:d\bar d:s\bar s=1:1:r_s$, is encoded in the measured jet strangeness $\langle S_{\rm flow}\rangle_f \simeq S_f+\frac{3r_s}{2+r_s} \left(\frac{1}{3}- \langle B_{\rm flow}\rangle_f\right)$, predicting a nonzero mean net strangeness even in $u$- and $d$-initiated jets. The conserved-current moments appearing in these relations are independent of the renormalization scale. Their simultaneous measurement therefore provides a direct,
flavor-resolved probe of
vacuum pair production and
quantum-number transport during hadronization.
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All authors Weiyao Ke, Hai Tao Li, Wanchen Li, Xiaohui Liu, Ding Yu Shao
Quantum Physics · Cross-listed from cs.CY
ChatGPT Solves All Tested Qiskit Homework Assignments
Alexei Kaltchenko and Gurnivaj Tiwana
Generative AI creates an assessment challenge in
quantum software education: a student can provide a homework notebook to ChatGPT and request a completed submission. This study examined whether introductory Qiskit homework could remain autogradable while requiring students to run, review, and discuss results rather than banning AI. Three packages were tested: seeded basis-state
circuits with bit flips and customized measurement mappings;
Quantum Fourier Transform followed by inverse-transform recovery; and seeded Deutsch-Jozsa with customized oracle masks. The designs used personalization, simulator execution, JSON submissions, hidden references,
circuit metrics, reflections, and optional IBM
Quantum execution. For each package, one student-visible instance was tested in 50 separate ChatGPT sessions, yielding 150 sessions overall. Every final artifact was executed and passed its grader. Nine sessions were fully archived; none required operator code changes or correction of
quantum logic. Under the study's operational definition, each tested instance had zero observed ChatGPT-resiliency. Seeds changed parameters rather than task structure, expected results remained derivable from visible assignment logic, scaffolding exposed key solution steps, and hidden grading verified output consistency without establishing independent authorship or understanding. Because one instance was repeated for each package, the results do not establish solvability for every seed or possible Qiskit assessment. The tested personalized, execution-oriented take-home designs therefore did not prevent successful completion under a minimally engaged-student workflow. Correct artifacts should be complemented by direct assessment through supervised modification, oral defense, prediction, and transfer tasks.
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Materials Science
Interplay of exchange and spin-conserving scattering processes in a ferromagnetic two-sublattice system
Ariyan Tavakoli, Kai Leckron and Hans Christian Schneider
In
magnetic alloys or hybrid systems formed by molecular magnets coupled to a
magnetic substrate, the exchange interaction leads to fast
spin dynamics after excitation. We investigate the electronic charge and
spin dynamics due to the exchange interaction in a two-sublattice system with
antiferromagnetic coupling. We employ a simplified model for a ferrimagnetic
alloy as a coupled system of itinerant and localized electron states together with an exchange coupling between the two. For the itinerant system we include electron-electron Coulomb scattering and electron-
phonon scattering. We study numerically the heat-induced ultrafast magnetization dynamics due to the interplay of exchange scattering and
spin-independent scattering processes and discuss different scenarios for the demagnetization and relaxation dynamics of the sublattices. Our results highlight the impact of
spin-conserving electron-electron scattering processes on the exchange-driven
spin dynamics on ultrashort timescales.
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Mesoscale and Nanoscale Physics
Coherence protection of a silicon hole spin qubit with phase-modulated microwave driving
Sayyid I. Ibad, Yusuke Sato, Takuma Kuno et al. (+8 more)
Hole
spins in silicon
quantum dots are a promising platform for
quantum computing due to their strong intrinsic
spin-orbit coupling (SOC), which enables fast, all-electrical control. However, this coupling also increases their susceptibility to charge noise, thereby limiting coherence times. Moreover, holes in silicon are also affected by hyperfine interactions with residual
nuclear spins in the silicon substrate, introducing a non-negligible source of low-frequency noise. Here, we implement a phase-modulated concatenated continuous driving (CCD) technique for hole
spin qubits to suppress low-frequency noise through microwave phase modulation. This approach stabilizes Rabi oscillations and extends the oscillation decay time compared to the conventional method. Furthermore, by defining a
qubit in the CCD frame, we achieve coherent control while simultaneously protecting the
qubit from noise, confirming coherence protection during gate operations. These results demonstrate a viable route toward noise-robust hole
spin qubits.
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All authors Sayyid I. Ibad, Yusuke Sato, Takuma Kuno, Itaru Yanagi, Toshiyuki Mine, Ryuta Tsuchiya, Digh Hisamoto, Hiroyuki Mizuno, Raisei Mizokuchi, Jun Yoneda, Tetsuo Kodera
General Relativity and Quantum Cosmology
Can Stochastic Clocks in FLRW Minisuperspace Prevent Dynamical Singularities?
Pradosh Keshav MV
We develop a
stochastic extension of the Wheeler–DeWitt equation in FLRW minisuperspace and show that
quantum backreaction can dynamically regulate the big bang singularity without imposing external boundary conditions. Using Laplace–Beltrami quantisation and an open-system treatment of coarse-grained graviton modes, we obtain a
stochastic Hamiltonian evolution equation in which the
diffusion coefficient takes the form $\sigma(a)\propto a^2$. This multiplicative noise vanishes at the origin and renders $a=0$ an entrance boundary in Feller's classification, leading to super-exponential suppression of the Laplace–Beltrami weighted stationary density and zero probability flux into the singular point. At large scale factor, the global behaviour depends on the cosmological sector: de Sitter and positive potential-dominated regimes exhibit power-law stationary tails, whereas confining potentials or negative effective cosmological constant lead to an entrance boundary at infinity and a globally normalizable steady state. Taken together, these results indicate that
stochastic backreaction arising from semiclassical coarse-graining provides a consistent and dynamical mechanism for singularity avoidance in minisuperspace
quantum cosmology.
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Quantum Physics
Dissipation-tunable extended and localized steady states in a non-disordered lattice
Ming-Jie Tao, Yi-Ting Wang, Jing Li et al. (+3 more)
Dissipation is usually regarded as a source of decoherence that suppresses
quantum interference and localization. Here we show that suitably engineered dissipation can instead be used to select localized or extended states in a strictly non-disordered one-dimensional
lattice. The underlying clean
lattice has spatially inhomogeneous hopping and supports both extended bulk states and localized boundary states, including an algebraically localized bound state in the continuum. We introduce a nonlocal bond jump operator with a tunable relative phase and show that this phase selectively favors eigenstates with different spatial phase correlations. As a result, the long-time density
matrix can be steered toward sectors dominated by localized or extended
Hamiltonian eigenstates without changing any
Hamiltonian parameter. The microscopic origin of the selection is quantified by the fraction of site pairs separated by a distance $l$ that are phase matched with the dissipative channel. We further characterize the dissipative quench through the
quantum fidelity and show that the selected character of the steady state can persist after the dissipation is removed. Our results establish phase-selective bond dissipation as a route to controllable state preparation and transport manipulation in non-disordered
lattices.
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All authors Ming-Jie Tao, Yi-Ting Wang, Jing Li, Hongsheng Hou, Xiang-Ping Jiang, Lei Pan
General Relativity and Quantum Cosmology
Open quantum system approach to the Unruh-DeWitt detector in impulsive plane wave spacetimes
Hing-Tong Cho
In this paper we employ the open
quantum system framework with the influence functional formalism to non-perturbatively analyze the response of an Unruh-DeWitt detector modeled as a harmonic oscillator which interacts with a massless scalar field in impulsive plane wave spacetimes. Subtracting the Minkowski results, we obtain the expectation values for $\langle Q^2 \rangle$, $\langle P^2 \rangle$, and $\langle \{Q,P\} \rangle$, along with transition probabilities $P_{0\rightarrow 1}$ from ground state to the first excited state of the detector due to the influence of the wave. Explicit calculations are performed for both a pure gravitational wave (vanishing
Ricci tensor) and a null electromagnetic wave (vanishing Weyl tensor). In both scenarios, the wave suppresses excitation transitions. Since our approach is non-perturbative, we are able to consider cases with both weak and strong coupling constants.
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High Energy Physics (Phenomenology)
Minimal Quark-Lepton Complementarity from a Rigid Deformation of Tri-Bimaximal Mixing
Gazal Sharma and Gaurav Katoch
We propose a minimal three-family realization of
quark–
lepton complementarity (QLC) in which the non-trivial correlation
matrix is an exactly
unitary, rigid deformation of tri-bimaximal mixing. In a canonical TBM convention the deformation is a rotation about the normalized axis $n_{gg}=(2,1,2)^T/3$, with rotation angle fixed by the Cabibbo angle, $\alpha_{gg}=-3\theta_C/4$. The resulting ansatz, $\UPMNS=\VCKM^\dagger\UTBM R_{n_{gg}}(-3\theta_C/4)$, contains no new continuous parameter in the Dirac
lepton-mixing sector once the structural choice is fixed. With the 2025 Particle Data Group CKM fit it predicts $\theta_{12}=33.29^\circ$, $\theta_{13}=8.46^\circ$, $\theta_{23}=49.19^\circ$, and $\dcp=180.79^\circ$, with CKM-induced uncertainties much smaller than present oscillation errors. We derive leading Wolfenstein sum rules; in particular, the real deformation preserves the CKM-induced suppression $\Jcp=-A\eta\lambda^3/6+\mathcal O(\lambda^4)$ and hence a near-CP-conserving phase. A retrospective simplicity scan shows that the pair $(2,1,2),3/4$ ranks first among 5510 oriented primitive-integer/rational candidates when tested on epoch-matched 2016 and 2018 oscillation data. In an enlarged 49,622-candidate 2018 scan it is second in raw score but remains first among candidates no more complex than itself under several independent simplicity measures; profiling the rotation strength for the fixed $(2,1,2)$ axis gives $r_{\rm BF}=0.74941$. We formulate the deformation by a convention-covariant
flavor-space generator and give an exact effective eigenframe realization $M_\nu=A I+B\Sgg+C\Sgg^2$. The construction is presently allowed in normal ordering, with the atmospheric sector providing its strongest pressure; its upper-octant atmospheric angle and near-$\pi$ Dirac phase provide sharp falsifiability targets.
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Solar and Stellar Astrophysics
The Kick Velocities of Neutron Stars in Binary Systems
Paul Disberg, Ilya Mandel and Ryosuke Hirai
Neutron stars (NSs) receive natal kicks on their formation in
supernovae (SNe). We consider constraints placed on the natal kick magnitudes by NSs in different classes of binary systems. We compare observed systems to predictions from the COMPAS rapid population synthesis code, where we apply kick models with varied natal kick prescriptions. Specifically, we compare binary orbits (i.e., periods and eccentricities) and systemic kick estimates of (1)
Gaia observations of NS-harboring binaries (
Gaia NSs), (2) NS low-mass X-ray binaries (LMXBs), (3) NS-white
dwarf binaries (NSWDs), (4) NS high-mass X-ray binaries (HMXBs) and in particular Be X-ray binaries (BeXBs), and (5) double NSs (DNSs). In this comparison, we find that we can reproduce most of the observed properties of the
Gaia NSs, LMXBs, and NSWDs with natal kicks calibrated to the velocities of young isolated
pulsars, although we need a small amount of "rocket" kicks to explain the
Gaia NS eccentricities. The HMXBs and DNSs, in contrast, show evidence of significantly reduced NS natal kicks. In particular, we find that an apparent correlation between eccentricity and systemic kick for DNSs can be explained by Blaauw kicks, if the natal kicks are $\lesssim 10$ km s$^{-1}$. Although our model does not align well with low-
metallicity Gaia NSs, high-eccentricity BeXBs, and DNS mass estimates, we provide alternative hypothetical explanations for these systems. We conclude that a model in which NSs that are formed in binaries with high-mass companions receive significantly reduced natal kicks can provide a relatively consistent explanation for the observed NSs in binary systems.
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Astrophysics of Galaxies
OutThere Survey: Addressing $\mathrm{\xi_{ion}}$ and $\mathrm{f_{esc}}$ with a population of average galaxies at z$\sim$2
Ravi Jaiswar, Anshu Gupta, Elisabete da Cunha et al. (+24 more)
Constraining the major contributors to the ionisation of the early universe is an ongoing endeavour of high-
redshift galaxy research. We measure the ionising
photon production efficiency and Lyman Continuum escape fraction for a sample of 230 intermediate
redshift ($1.3<z<2.6$) sources observed as a part of the OutThere survey; a pure-parallel, wide-area JWST/NIRISS survey with accompanying JWST/NIRCam, NIRISS and HST photometry. The low threshold emission selection criteria for this sample makes for a large and robust control, against which other works may be contrasted, particularly for low-mass
galaxies above z$>$5. This control sample allows us to verify the correlations between ionising and spectral/physical properties suggested by previous studies. We find no significant correlations between the ionising
photon production efficiency ($\mathrm{\xi_{ion}}$) with the UV slope, $\mathrm{M_{UV}}$, M$_*$ or sSFR. We do find that $\mathrm{\xi_{ion}}$ correlates with [OIII]5007Å\, equivalent width (EW) (Spearman coefficient $\rho$ =0.24; p$< 4\times10^{-4}$) and H$\alpha$ EW ($\rho$ =0.63; p$<< 1\times10^{-6}$) hold even at low EW albeit with more scatter. We also find that our novel approach to determining the ionising
photon escape fraction $\mathrm{f_{esc}}$ results in values within theoretical ranges (0-10%) though vary substantially in comparison to the empirical results (median $\mathrm{f_{esc}} = 0.9\%^{+1.1}_{-0.5}$ including non-detections, median $\mathrm{f_{esc}} = 1.9\%^{+8.9}_{-1.8}$ above a $0.01\%$ threshold). We find that this escape fraction method has consistently significant correlations with the
redshift, SFR and M$_{UV}$ and sample-dependent correlations with [OIII]5007Å\,EW,H$\alpha$ EW and
stellar mass.
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All authors Ravi Jaiswar, Anshu Gupta, Elisabete da Cunha, Cathryn M. Trott, Andrew Battisti, Isabel Perez, Karl Glazebrook, Lalitwadee Kawinwanichakij, Zackary L. Hutchens, Ivelina Momcheva, Claudia Del.P Lagos, Themiya Nanayakkara, Colin Jacobs, Danilo Marchesini, David A. Wake, Alice Shapley, Gabriel Brammer, Raphael Hviding, Casey Papovich, Ryan L. Sanders, Rhea-Silvia Remus, Mengtao Tang, Daniel Stark, Vincente Estrada-Carpenter, Joshua Speagle, Kartheik Iyer, Jasleen Matharu
Quantum Physics
Tight Entropy Contraction of Generalized Quantum Depolarization
Li Gao and Long Zhao
We establish upper and lower bounds for relative
entropy contraction of generalized
quantum depolarizing channels and
semigroups. Our bound provides tight first order asymptotic of the contraction rate in terms of the dimension constant. One side estimate are based on sharp reverse ratio and convexity of relative
entropy of two states, which can be derived from the recently introduced Hockey-Stick
quantum $f$-divergence, and also independently, Bogoliubov–Kubo–Mori
quantum Fisher information metric. The other side follows from the existence of index achieving pure state with respect to a general conditional expectation. Our results extend to the complete
entropy contraction rate, tensor stable estimates for product dynamics. Examples include
quantum depolarization, dephasing, and compact group symmetrization, with consequences for the decay rate of coherence and asymmetry.
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Optics
Cavity-Enhanced Activation of Radiatively Suppressed Light-Hole Exciton Emission in Colloidal Nanoplatelets
Komal Sharma, Riya Dutta, Prathmesh Deshmukh et al. (+2 more)
Light-hole (LH)
excitons provide access to well-defined polarization and
spin degrees of freedom that are central to
quantum photonics and
chiral light-matter interactions. Achieving LH emission is challenging because LH states are energetically unfavoured and typically relax non-radiatively. Existing strategies to access LH
excitons rely on modifying the electronic band structure through strain, shape anisotropy, or piezoelectric fields, approaches that are material-specific and offer limited post-synthesis tunability. Here we demonstrate an all-photonic route to activate LH
exciton emission in colloidal CdSe-CdS nanoplatelets (NPLs) using a distributed Bragg reflector (DBR) cavity, without altering the underlying band structure. In the absence of a cavity mode, the system exhibits amplified spontaneous emission from heavy-hole (HH) states without detectable LH emission at low excitation powers. By spectrally matching a cavity resonance to the LH
exciton, cavity-coupled LH emission emerges at significantly lower excitation powers. Temperature-dependent spectroscopy reveals reversible switching between LH- and HH-coupled emission through
exciton-cavity detuning, while polarization-resolved and spectrally resolved time-resolved photoluminescence measurements provide independent evidence distinguishing the cavity-coupled LH and HH emission channels. These findings establish cavity engineering as a general materials-level approach for accessing radiatively suppressed optical states.
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All authors Komal Sharma, Riya Dutta, Prathmesh Deshmukh, Vinod M.Menon, Jaydeep K. Basu