Wed·Aug 7, 2024Wednesday·August 7, 2024

1. 01*

   KAN we improve on HEP classification tasks? Kolmogorov-Arnold Networks applied to an LHC physics example

   Johannes Erdmann🇩🇪 · Florian Mausolf🇩🇪 · Jan Lukas Späh🇩🇪

   Recently, Kolmogorov-Arnold Networks (KANs) have been proposed as an alternative to multilayer perceptrons, suggesting advantages in performance and interpretability. We study a typical binary event classification task in high-energy physics including high-level features and comment on the performance and interpretability of KANs in this context. Consistent with expectations, we find that the learned activation functions of a one-layer KAN resemble the univariate log-likelihood ratios of the respective input features. In deeper KANs, the activations in the first layer differ from those in the one-layer KAN, which indicates that the deeper KANs learn more complex representations of the data, a pattern commonly observed in other deep-learning architectures. We study KANs with different depths and widths and we compare them to multilayer perceptrons in terms of performance and number of trainable parameters. For the chosen classification task, we do not find that KANs are more parameter efficient. However, small KANs may offer advantages in terms of interpretability that come at the cost of only a moderate loss in performance.

   hep-phcs.LGhep-exphysics.data-anComput.Softw.Big Sci.(2025)·4 citations
2. 02*

   Factorization for energy-energy correlator in heavy ion collision

   Balbeer Singh🇺🇸 · Varun Vaidya🇺🇸

   We present a factorization formula for the energy-energy correlator in the collinear limit for the case of heavy ion collisions. Employing Soft Collinear Effective Theory, we provide a complete framework for jet production and evolution by separating the jet dynamics from the universal medium physics to all orders in perturbation theory in terms of gauge invariant operators. The EFT allows us to precisely define the domain of validity of different approximations and to systematically go beyond leading order results in the literature through radiative corrections. For this observable, we show where the leading order GLV and BDMPS-Z results are valid and infer that higher order radiative corrections lead to both DGLAP and BFKL evolutions. We further show the impact of BFKL resummation on the medium induced jet function for two point energy correlator. Crucially, the EFT approach enables us to evaluate the universality of the non-perturbative physics which is the key to predictive power in a strongly coupled medium.

   hep-phJHEP(2025)·39 citations
3. 03*

   A new method to clarify contribution of chiral magnetic effect in small collision system $p^{\uparrow }+A$ involving a transversely polarized proton

   Gui-Zhen Wu🇨🇳 · Zong-Wei Zhang🇨🇳 · Chen Gao🇨🇳 · Yi Xu🇨🇳 · Wei-Tian Deng🇨🇳

   In this paper, we propose a new experiment method to check contribution of chiral magnetic effect (CME). With experimental data of DIS involving transversely polarized proton, we have calculated the 3-D charge density inside the polarized proton, which is found to have a significant violation to spherical symmetry. Then we have calculated the property of electromagnetic field (E-M field) generated by a single transversely polarized proton ($p^{\uparrow }$). Based on them, the E-M field generated in small collision system $p^{\uparrow }+A$ are studied. We find that the orientation of this E-M field has a significant dependence on the polarization direction of the proton, and the correlator ($\Delta \gamma$ ) has also significant dependence on the angle between reaction plane and polarization direction. As background contribution are canceled comparing two collision geometry schemes, only contribution of CME is remained.

   hep-phnucl-thPRC(2024)·2 citations
4. 04*

   Reconciling Cosmological Tensions with Inelastic Dark Matter and Dark Radiation in a $\mathbf{U}(1{)}_{\mathbf{D}}$ Framework

   Wonsub Cho🇰🇷 · Ki-Young Choi🇰🇷 · Satyabrata Mahapatra🇰🇷

   We propose a novel and comprehensive particle physics framework that addresses multiple cosmological tensions observed in recent measurements of the Hubble parameter, $S_8$, and Lyman-$\alpha$ forest data. Our model, termed `{\bf SIDR$+{\mathbf{z}}_{\mathbf{t}}$}' (Self Interacting Dark Radiation with transition redshift), is based on an inelastic dark matter (IDM) scenario coupled with dark radiation, governed by a $U(1{)}_D$ gauge symmetry. This framework naturally incorporates cold dark matter (DM), strongly interacting dark radiation (SIDR), and the interactions between these components. The fluid-like behavior of the dark radiation component which originates from the self-quartic coupling of the $U(1{)}_D$ breaking scalar can suppress the free-streaming effects. Simultaneously, the interacting DM-DR system can attenuate the matter power spectrum at small scales. The inelastic nature of DM provides a distinct temperature dependence for the DM-DR interaction rate determined by the mass-splitting between the inelastic dark fermions which is crucial for resolving the Ly-$\alpha$ discrepancies. We present a cosmologically consistent analysis of the model by solving the relevant Boltzmann equations to obtain the energy density and number density evolution of different species of the model. The DR undergoes two ``steps" of increased energy density when the heavier dark species freeze out and become non-relativistic, transferring their entropy to the dark radiation and enhancing $\Delta N_{\mathrm{eff}}$. The analysis showcases the model's potential to uphold the Big Bang Nucleosynthesis (BBN) prediction of $\Delta N_{\mathrm{eff}}$ but dominantly producing additional contributions prior to recombination, while simultaneously achieving correct relic density of DM though an hybrid of freeze-in and non-thermal production.

   hep-phastro-ph.COJCAP(2024)·6 citations
5. 05*

   ${\eta }_{c2}{(}^1{D}_2)$ and its electromagnetic decays

   Xin-Yao Du🇨🇳 · Su-Yan Pe · Wei Li · Man Jia🇨🇳 · Qiang Li · Tianhong Wang · Bo Wang · Guo-Li Wang

   The spin-singlet state ${\eta }_{c2}{(}^1{D}_2)$ has not been discovered in experiment and it is the only missing low-excited $D$-wave charmonium, so in this paper, we like to study its properties. Using the Bethe-Salpeter equation method, we obtain its mass as $3828.2$ MeV and its electromagnetic decay widths as $\Gamma [{\eta }_{c2}(1D)\to h_c(1P)\gamma ]=284$ keV, $\Gamma [{\eta }_{c2}(1D)\to J/\psi \gamma ]=1.04$ keV, $\Gamma [{\eta }_{c2}(1D)\to \psi (2S)\gamma ]=3.08$ eV, and $\Gamma [{\eta }_{c2}(1D)\to \psi (3770)\gamma ]=0.143$ keV. {Considering the strong decay widths are estimated to be $\Gamma ({\eta }_{c2}(1D)\to {\eta }_c\pi \pi )=144\mathrm{keV}$ and $\Gamma ({\eta }_{c2}(1D)\to gg)=46.1\mathrm{keV}$, we obtain the total decay width of $475$ keV for ${\eta }_{c2}(1D)$, and point out that the full width is very sensitive to the mass $M_{{\eta }_{c2}}$.} In our calculation, the emphasis is put on the relativistic corrections. Our results show that ${\eta }_{c2}\to h_c\gamma$ is the nonrelativistic $E1$ transition dominated $E1+M2+E3$ decay, and ${\eta }_{c2}\to \psi \gamma$ is the $M1+E2+M3+E4$ decay but the relativistic $E2$ transition contributes the most.

   hep-phhep-exPRD(2024)·6 citations
6. 06*

   Splitting amplitudes at N${}^3$LO in QCD

   Xin Guan🇺🇸 · Franz Herzog🇬🇧 · Yao Ma🇨🇭 · Bernhard Mistlberger🇺🇸 · Adi Suresh🇺🇸

   In the limit where partons become collinear to each other, scattering amplitudes factorize into a product of universal, process-independent building blocks and scattering amplitudes involving fewer partons. We compute these universal building blocks -- known as splitting amplitudes -- for two collinear QCD partons up to third loop order in QCD. Our results describe arbitrary time-like splitting processes. Due to the violation of strict collinear factorization in space-like splitting processes, we specifically present space-like splitting amplitudes for three-parton QCD scattering amplitudes at third loop order. To achieve our results, we perform a collinear expansion of three-loop scattering amplitudes using a new expansion-by-subgraph technology, which is based on the method of regions.

   hep-phhep-thJHEP(2025)·32 citations
7. 07*

   Valence Quark Distributions in Pions: Insights from Tsallis Entropy

   Jingxuan Chen🇨🇳 · Xiaopeng Wang🇨🇳 · Yanbing Cai🇨🇳 · Xurong Chen · Qian Wang🇨🇳

   We investigate the valence quark distributions of pions at a low initial scale ($Q_0^2$) by employing Tsallis entropy, a non-extensive measure that effectively captures long-range correlations among internal constituents. Utilizing the maximum entropy approach, we adopt two distinct functional forms and fit experimental data through the elegant GLR-MQ-ZRS evolution equation to derive the model parameters. Our findings indicate that the resulting valence quark distributions provide an optimal fit to experimental data, with the values of the $q$ parameter deviating from unity. This deviation indicates the significant role that correlations among valence quarks play in shaping our understanding of pion internal structure. Additionally, our computations of the first three moments of pion quark distributions at $Q^2=4{\mathrm{GeV}}^2$ display consistency with other theoretical models, thereby reinforcing the importance of incorporating valence quark correlations within this analytical framework.

   hep-phCPC(2026)·6 citations
8. 08*

   Hybrid approach to perfect and dissipative spin hydrodynamics

   Zbigniew Drogosz🇵🇱 · Wojciech Florkowski🇵🇱 · Mykhailo Hontarenko🇵🇱

   A hybrid framework of spin hydrodynamics is proposed that combines the results of kinetic theory for particles with spin 1/2 with the Israel-Stewart method of introducing nonequilibrium dynamics. The framework of kinetic theory is used to define the perfect-fluid description that conserves baryon number, energy, linear momentum and spin part of angular momentum. This leads to the entropy conservation although, in the presence of spin degrees of freedom, the perfect-fluid formalism includes extra terms whose structure is usually attributed to dissipation. The genuine dissipative terms appear from the condition of positive entropy production in nonequilibrium processes. They are responsible for the transfer between the spin and orbital parts of angular momentum, with the total angular momentum being conserved.

   hep-phnucl-thPRD(2024)·32 citations
9. 09*

   Jet Definition and Transverse-Momentum-Dependent Factorization in Semi-Inclusive Deep-Inelastic Scattering

   Paul Caucal🇫🇷 · Edmond Iancu🇫🇷 · A. H. Mueller🇺🇸 · Feng Yuan🇺🇸

   Using the colour dipole picture of Deep Inelastic Scattering (DIS) and the Colour Glass Condensate effective theory, we study semi-inclusive jet production in DIS at small $x$ in the limit where the photon virtuality $Q^2$ is much larger than the transverse momentum squared $P_{\perp }^2$ of the produced jet. In this limit, the cross-section is dominated by aligned jet configurations, that is, quark-antiquark pairs in which one of the fermions -- the would-be struck quark in the Breit frame -- carries most of the longitudinal momentum of the virtual photon. We show that physically meaningful jet definitions in DIS are such that the effective axis of the jet sourced by the struck quark is controlled by its virtuality rather than by its transverse momentum. For such jet definitions, we show that the next-to-leading order (NLO) cross-section admits factorisation in terms of the (sea) quark transverse momentum dependent (TMD) distribution, which in turn satisfies a universal Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and Sudakov evolution.

   hep-phnucl-thPRL(2025)·20 citations
10. 10*

    Finite beaming effect on QED cascades

    Suo Tang🇨🇳

    The quantum electrodynamic (QED) theory predicts the photon emission and pair creation involved in QED cascades occur mainly in a forward cone with finite angular spread $\Delta \theta \sim 1/{\gamma }_i$ along the momenta of incoming particles. This finite beaming effect has been assumed to be negligible because of the particles' ultra-relativistic Lorentz factor ${\gamma }_i\gg 1$ in laser-driven QED cascades. We develop an energy- and angularly resolved particle-tracking code, resolving both the energy spectra and the momentum profile of the outgoing particles in each QED event, which improves substantially the agreement between the simulation and exact QED results. We investigate QED cascades driven by two counter-propagating circularly polarized laser pulses, and show that the narrow beaming could be accumulated to effectively suppress the long-term growth of cascades, even though it can hardly affect the early formation of cascades. For QED cascades longer than $10$ laser cycles, the finite beaming effect could decrease the final pair yield, especially at ultrahigh intensities $\xi >600$, by more than $10\%$.

    hep-phPLB(2024)·5 citations
11. 11*

    $\mathrm{SU}(3{)}_{\mathrm{F}}$ sum rules for CP asymmetry of $D_{(s)}$ decays

    Syuhei Iguro🇩🇪 · Ulrich Nierste🇩🇪 · Emil Overduin🇩🇪 · Maurice Schüßler🇩🇪

    Charge-parity (CP) asymmetries in charm decays are extremely suppressed in the Standard Model and may well be dominated by new physics contributions. The LHCb collaboration reported the results of direct CP asymmetry measurements in $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$ decays with unprecedented accuracy: $a_{\mathrm{CP}}(K^{+}{K}^{-})=(7.7\pm 5.7)\times 10^{-4}$ and $a_{\mathrm{CP}}({\pi }^{+}{\pi }^{-})=(23.2\pm 6.1)\times 10^{-4}$, with the latter quantity inferred from the precise measurement of $\Delta a_{\mathrm{CP}}=a_{\mathrm{CP}}(K^{+}{K}^{-})-a_{\mathrm{CP}}({\pi }^{+}{\pi }^{-})=(-15.7\pm 2.9)\times 10^{-4}$. When interpreted within the Standard Model, these values indicate a breakdown of the approximate $U$-spin symmetry of QCD. If, however, this symmetry holds and the data stem from new physics, other CP asymmetries should be enhanced as well. We derive CP asymmetry sum rules based on $\mathrm{SU}(3)$ flavor symmetry for $D$ meson decays into a pair of pseudoscalar mesons as well as a pair of a pseudoscalar and a vector meson for two generic scenarios, with $\Delta U=0$ and $|\Delta U|=1$ interactions, respectively. The correlations implied by the sum rules can be used to check the consistency between different measurements and to discriminate between these scenarios with future data. For instance, we find $a_{\mathrm{CP}}({\pi }^{+}{K}^{\ast 0})+a_{\mathrm{CP}}(K^{+}{\overline{K}}^{\ast 0})=0$ for $\Delta U=0$ new physics and the opposite relative sign for the $|\Delta U|=1$ case. One sum rule, connecting four decay modes, holds in both scenarios. We further extend our sum rules to certain differences of CP asymmetries from which the $D$ production asymmetries drop out.

    hep-phhep-exPRD(2025)·16 citations
12. 12*

    Overview of $B\to K^{(\ast )}\ell \ell$ Theoretical Calculations and Uncertainties

    F. Mahmoudi🇫🇷 · Y. Monceaux🇫🇷

    The search for New Physics (NP) beyond the Standard Model (SM) has been a central focus of particle physics, including in the context of $B$-meson decays involving $b\to s\ell \ell$ transitions. These transitions, mediated by flavour-changing neutral currents, are highly sensitive to small NP effects due to their suppression in the SM. While direct searches at colliders have not yet led to NP discoveries, indirect probes through semi-leptonic decays have revealed anomalies in observables such as the branching fraction $\mathcal{B}(B\to K\mu \mu )$ and the angular observable $P_5^{\prime }(B\to K^{\ast }\mu \mu )$. In order to assess the observed tensions, it is essential to ensure an accurate SM prediction. In this review, we examine the theoretical basis of the $B\to K^{(\ast )}\ell \ell$ decays, addressing in particular key uncertainties arising from local and non-local form factors. We also discuss the impact of QED corrections to the Wilson coefficients, as well as the effect of CKM matrix elements on the predictions and the tension with the experimental measurements. We discuss the most recent results, highlighting ongoing efforts to refine predictions and to constrain potential signs of NP in these critical decay processes.

    hep-phSymmetry(2024)·22 citations
13. 13*

    Two-loop running effects in Higgs physics in Standard Model Effective Field Theory

    Stefano Di Noi🇮🇹 · Ramona Gröber🇮🇹 · Manoj K. Mandal🇮🇹

    We consider the renormalization group equations within the Standard Model Effective Field Theory and compute two-loop contributions proportional to the top quark Yukawa coupling for the operator generating an effective Higgs-gluon coupling, focusing on the Yukawa-like operator. These two-loop running effects are relevant for processes where the effective Higgs-gluon coupling contributes at a lower loop order compared to the Standard Model contribution and where a dynamical scale choice is adopted. Such a situation arises, for instance, in the Higgs transverse momentum distribution and Higgs pair production. We investigate the phenomenological impact of our computations on these two processes and find that the two-loop contributions are significant and can lead to deviations of up to 20\% in the scenarios we consider.

    hep-phJHEP(2024)·51 citations
14. 14*

    Minding the gap: testing natural anomaly-mediated SUSY breaking at high luminosity LHC

    Howard Baer🇺🇸 · Vernon Barger🇺🇸 · Jessica Bolich🇺🇸 · Juhi Dutta🇺🇸 · Dibyashree Sengupta🇮🇹

    While the minimal anomaly-mediated SUSY breaking model (mAMSB) seems ruled out by constraints on Higgs mass, naturalness and wino dark matter, a slightly generalized version dubbed natural AMSB (nAMSB) remains both viable and compelling. Like mAMSB, nAMSB features winos as the lightest gauginos, but unlike mAMSB, nAMSB allows a small mu parameter so that higgsinos are the lightest of electroweakinos (EWinos). nAMSB spectra depend on the input value of gravitino mass m_{3/2}, where the lower range of m_{3/2} is excluded by LHC gluino pair searches while a higher m_{3/2} band is excluded by LHC limits on wino pair production followed by boosted hadronic wino decays. A remaining intermediate gap in m_{3/2} values remains allowed by present LHC searches, but appears to be completely explorable by high luminosity ugrades of LHC (HL-LHC). We explore a variety of compelling discovery channels that may allow one to close the intermediate gap in m_{3/2} values: 1. same-sign diboson +MET (SSdB) production arising from wino pair production, leading to same-sign dileptons plus MET, 2. trilepton production arising from wino pair production and 3. soft dilepton plus jet events from higgsino pair production, 4. top-squark pair production. From our signal-to-background analysis along a nAMSB model line, we expect HL-LHC to either discover or rule out the nAMSB model with 3000 fb^{-1} of integrated luminosity.

    hep-phPRD(2025)·3 citations
15. 15*

    Parametrization sampling and the pion PDF in a phenomenological analysis

    Aurore Courtoy🇲🇽

    In these proceedings, we extend the discussion of the pion PDF obtained by NLO QCD analysis in the Fantômas4QCD framework. Our pion analysis uses a state-of-the-art statistical methodology that accounts for the epistemic uncertainty. Fantômas4QCD, designed to handle multiple functional forms for solving the inverse problem, systematically explores a variety of solutions for PDFs, thereby improving estimates of epistemic uncertainty. Through this novel approach, we interpret our results for the valence sector, considering various non-perturbative methods available for predicting the pion PDF. We emphasize the distinctions between (global) QCD analyses and QFT-based calculations.

    hep-phPoS(2025)·1 citation
16. 16*

    Proper Time Observables of General Gravitational Perturbations in Laser Interferometry-based Gravitational Wave Detectors

    Vincent S. H. Lee🇺🇸 · Kathryn M. Zurek🇺🇸

    We present an explicitly gauge-invariant observable of {\em any} general gravitational perturbation, $h_{\mu \nu }$ (\textit{not} necessarily due to gravitational waves (GWs)), in a laser interferometry-based GW detector, identifying the signature as the proper time elapsed of the beamsplitter observer, between two events: when a photon passes through the beamsplitter, and when the same photon returns to the beamsplitter after traveling through the interferometer arm and reflecting off the far mirror. Our formalism applies to simple Michelson interferometers and can be generalized to more advanced setups. We demonstrate that the proper time observable for a plane GW is equivalent to the detector strain commonly used by the GW community, though now the common framework can be easily generalized for other types of signals, such as dark matter clumps or spacetime fluctuations from quantum gravity. We provide a simple recipe for computing the proper time observable for a general metric perturbation in linearized gravity and explicitly show that it is invariant under diffeomorphisms of the perturbation, as any physical observable should be.

    hep-phgr-qcPRD(2025)·16 citations
17. 17*

    Long-lived particle phenomenology in one-loop neutrino mass models with dark matter

    Carolina Arbeláez🇨🇱 · Giovanna Cottin🇨🇱 · Juan Carlos Helo🇨🇱 · Martin Hirsch🇪🇸 · Téssio B. de Melo🇨🇱

    Neutrino masses and dark matter (DM) might have a common origin. The scotogenic model can be considered the proto-type model realizing this idea, but many other variants exist. In this paper we explore the phenomemology of a particular DM neutrino mass model, containing a triplet scalar. We calculate the relic density and check for constraints from direct detection experiments. The parameter space of the model, allowed by these constraints, contains typically a long-lived or quasi-stable doubly charged scalar, that can be searched for at the LHC. We reinterpret existing searches to derive limits on the masses of the scalars of the model and estimate future sensitivities in the high-luminosity phase of the LHC. The searches we discuss can serve to constrain also many other 1-loop neutrino mass models.

    hep-phJHEP(2025)·3 citations
18. 18*

    Field Redefinitions in Classical Field Theory with some Quantum Perspectives

    Juan Carlos Criado🇪🇸 · Joerg Jaeckel🇩🇪 · Michael Spannowsky🇬🇧

    In quantum field theories, field redefinitions are often employed to remove redundant operators in the Lagrangian, making calculations simpler and physics more evident. This technique requires some care regarding, among other things, the choice of observables, the range of applicability, and the appearance and disappearance of solutions of the equations of motion (EOM). Many of these issues can already be studied at the classical level, which is the focus of this work. We highlight the importance of selecting appropriate observables and initial/boundary conditions to ensure the physical invariance of solutions. A classical analogue to the Lehmann-Symanzik-Zimmermann (LSZ) formula is presented, confirming that some observables remain independent of field variables without tracking redefinitions. Additionally, we address, with an example, the limitations of non-invertible field redefinitions, particularly with non-perturbative objects like solitons, and discuss their implications for classical and quantum field theories.

    hep-phhep-thPRD(2025)·7 citations
19. 19*

    Adiabatic Conversion of ALPs into Dark Photon Dark Matter

    Edward Broadberry🇺🇸 · Saurav Das🇺🇸 · Anson Hook🇺🇸 · Gustavo Marques-Tavares🇺🇸

    We introduce a mechanism by which a misaligned ALP can be dynamically converted into a dark photon in the presence of a background magnetic field. An abundance of non-relativistic ALPs will convert to dark photons with momentum of order the inhomogeneities in the background field; therefore a highly homogeneous field will produce non-relativistic dark photons without relying on any redshifting of their momenta. Taking hidden sector magnetic fields produced by a first order phase transition, the mechanism can reproduce the relic abundance of dark matter for a wide range of dark photon masses down to $10^{-13}$ eV.

    hep-phJHEP(2025)·7 citations
20. 20*

    Event Horizon Telescope observations exclude compact objects in baseline mimetic gravity

    Mohsen Khodadi🇮🇷 · Sunny Vagnozzi🇮🇹 · Javad T. Firouzjaee🇮🇷

    Mimetic gravity has gained significant appeal in cosmological contexts, but static spherically symmetric space-times within the baseline theory are highly non-trivial: the two natural solutions are a naked singularity and a black hole space-time obtained through an appropriate gluing procedure. We study the shadow properties of these two objects, finding both to be pathological. In particular, the naked singularity does not cast a shadow, whereas the black hole casts a shadow which is too small. We argue that the Event Horizon Telescope images of M87${}^{\star }$ and Sgr A${}^{\star }$ rule out the baseline version of mimetic gravity, preventing the theory from successfully accounting for the dark sector on cosmological scales. Our results highlight an interesting complementarity between black hole imaging observations and modified gravity theories of cosmological interest.

    ↳ gr-qcastro-ph.COhep-phhep-thSci.Rep.(2024)·77 citations
21. 21*

    Krylov complexity of thermal state in early universe

    Tao Li🇨🇳 · Lei-Hua Liu🇨🇳

    Thermal interactions are ubiquitous in the cosmos, driving systems toward equilibrium. In this work, we investigate the evolution of thermal states across the early universe, encompassing the inflationary, radiation-dominated (RD), and matter-dominated (MD) eras, through the lens of Krylov complexity. Utilizing a purification scheme, we map the thermal state to a two-mode pure state, facilitating an open-system analysis of Krylov complexity in contrast to closed-system methodologies. Our numerical results demonstrate that Krylov complexity grows exponentially during inflation, indicating chaotic behavior, before saturating at nearly constant values in the RD and MD eras due to particle production via preheating. Furthermore, we analyze the Krylov entropy, which exhibits an evolutionary trend analogous to that of complexity. Crucially, our analysis reveals a dynamical transition in the universe's dissipative nature: with the universe acting as a strongly dissipative system during inflation and transitioning to a weakly dissipative regime in the subsequent eras. These findings provide a novel quantum information perspective on early universe dynamics.

    ↳ hep-thastro-ph.COgr-qchep-ph+1EPJC(2026)·18 citations
22. 22*

    Non-Hermitian Quantum Mechanics Approach for Extracting and Emulating Continuum Physics Based on Bound-State-Like Calculations

    Xilin Zhang🇺🇸

    This work introduces a unified emulation framework for studying continuum physics in finite quantum systems. Using a reduced basis method, we construct powerful emulators for the inhomogeneous Schrödinger equation that operate in a combined parameter space of complex energy ($E$) and other inputs ($\mathbf{\theta }$). Within the space, the emulators simultaneously perform analytical continuation in $E$ -- extracting continuum physics from numerically simpler bound-state-like calculations -- and interpolate this entire process across $\mathbf{\theta }$. This yields a small, non-Hermitian system whose properties (e.g., resonances and scattering observables) can be rapidly predicted for any $\mathbf{\theta }$. Crucially, the complex-$E$ emulation provides a pathway to compute continuum observables for complex systems where advanced bound-state methods exist but direct continuum calculations are yet to be developed, while the $\mathbf{\theta }$-emulation enables rapid parameter-space exploration and can be adapted to accelerate other existing continuum calculations. Demonstrations with two- and three-body systems highlight the method's effectiveness and suggest its connection to (near-)optimal rational approximation. This Letter presents the key results, with further details reserved for a companion paper.

    ↳ nucl-thhep-phphysics.atom-phphysics.chem-ph+1PRL(2025)·15 citations
23. 23*

    Uniqueness Criteria for the Virasoro-Shapiro Amplitude

    Clifford Cheung🇺🇸 · Aaron Hillman🇺🇸 · Grant N. Remmen🇺🇸

    The scattering amplitudes of string theory exhibit many extraordinary properties. But are they the unique mathematical objects to do so? Recently, it has been shown how the spectrum and amplitudes of open string theory follow directly from the assumptions of faster than power-law falloff at high energies and a property dubbed level truncation. At present there is no analogous principle for closed string scattering, which is famously rigid and naively impervious to modification. In this paper we analytically bootstrap the spectrum and four-point amplitudes of the closed string -- together with a parameterized space of deformations -- from conditions on high-energy falloff and level truncation. While these deformations exhibit the same Regge scaling as pure gravity, in the tensionless limit they reproduce remarkable extremal amplitudes that have appeared in bottom-up studies of positivity.

    ↳ hep-thgr-qchep-phPRD(2025)·38 citations
24. 24*

    Neutrinoless $\beta \beta$ decay nuclear matrix elements complete up to N${}^2$LO in heavy nuclei

    Daniel Castillo🇪🇸 · Lotta Jokiniemi🇨🇦 · Pablo Soriano🇪🇸 · Javier Menéndez🇪🇸

    We evaluate all nuclear matrix elements (NMEs) up to next-to-next-to leading order (N${}^2$LO) in chiral effective field theory ($\chi$EFT) for the neutrinoless double-beta ($0\nu \beta \beta$) decay of the nuclei most relevant for experiments, including ${}^{76}$Ge, ${}^{100}$Mo, and ${}^{136}$Xe. We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) and the nuclear shell model to calculate the N${}^2$LO NMEs from very low-momentum (ultrasoft) neutrinos and from loop diagrams usually neglected in $0\nu \beta \beta$ studies. Our results indicate that the overall N${}^2$LO contribution is centered around $-(5$-$10)\%$ for the shell model and $+(10$-$15)\%$ for the pnQRPA, with sizable uncertainties due to the scale dependence of the ultrasoft NMEs and the short-range nature of the loop NMEs. The sign discrepancy between many-body methods is common to all studied nuclei and points to the different behaviour of the intermediate states of the $0\nu \beta \beta$ decay. Within uncertainties, our results for the ultrasoft NME are of similar size as contributions usually referred to as ``beyond the closure approximation''.

    ↳ nucl-thhep-exhep-phnucl-exPLB(2025)·19 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.