Thu·Jan 18, 2024Thursday·January 18, 2024

1. 01*

   Role of $\rho -\omega$ interference in semileptonic $B\to {\pi }^{+}{\pi }^{-}\ell {\bar{\nu }}_{\ell }$ decays

   Florian U. Bernlochner🇩🇪 · Stefan Wallner🇩🇪

   It is long known that interference effects play an important role in understanding the shape of the ${\pi }^{+}{\pi }^{-}$ spectrum of resonances near the threshold. In this manuscript we investigate the role of the $\rho -\omega$ interference in the study of semileptonic $B\to {\pi }^{+}{\pi }^{-}\ell {\bar{\nu }}_{\ell }$ decays. We determine for the first time the strong phase between $B\to {\rho }^0\ell {\bar{\nu }}_{\ell }$ and $B\to \omega \ell {\bar{\nu }}_{\ell }$ from a recent Belle measurement of the $m_{\pi \pi }$ spectrum of $B\to {\pi }^{+}{\pi }^{-}\ell {\bar{\nu }}_{\ell }$. We find ${\varphi }_{\rho -\omega }=\left(-46_{-67}^{+155}\right)°$ and extract the branching fraction of $\mathcal{B}(B\to {\rho }^0\ell {\bar{\nu }}_{\ell })=\left(1.41_{-0.38}^{+0.49}\right)\times 10^{-4}$. In addition, we set a limit on the $S$-wave component within a mass window ranging from $2m_{\pi }$ to $1.02\mathrm{GeV}$ of $0.51\times 10^{-4}\mathrm{at}90\%\mathrm{CL}$. We also determine the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element of $|V_{ub}{|}_{\rho -\omega }=\left(3.03_{-0.44}^{+0.49}\right)\times 10^{-3}$, which takes into account the $\rho -\omega$ interference.

   hep-phhep-exPRD(2024)·10 citations
2. 02*

   Dark showers from Z-dark Z' mixing

   Hsin-Chia Cheng🇺🇸 · Xu-Hui Jiang🇨🇳 · Lingfeng Li🇺🇸 · Ennio Salvioni🇮🇹

   We discuss dark shower signals at the LHC from a dark QCD sector, containing GeV-scale dark pions. The portal with the Standard Model is given by the mixing of the Z boson with a dark Z' coupled to the dark quarks. Both mass and kinetic mixings are included, but the mass mixing is the essential ingredient, as it is the one mediating visible decays of the long-lived dark pions. We focus especially on the possibility that the dark Z' is lighter than the Z. Indirect constraints are dominated by electroweak precision tests, which we thoroughly discuss, showing that both Z-pole and low-energy observables are important. We then recast CMS and LHCb searches for displaced dimuon resonances to dark shower signals initiated by the production of on-shell Z or Z', where the visible signature is left by a dark pion decaying to ${\mu }^{+}{\mu }^{-}$. We demonstrate how dark shower topologies have already tested new parameter space in Run 2, reaching better sensitivity on a light dark Z' compared to the flavor-changing decays of B mesons, which can produce a single dark pion at a time, and the electroweak precision tests.

   hep-phhep-exJHEP(2024)·27 citations
3. 03*

   Cosmological first-order phase transitions without bubbles

   Dongdong Wei🇨🇳 · Haibin Chen🇨🇳 · Qiqi Fan🇨🇳 · Yun Jiang🇨🇳

   In the traditional view a cosmic first-order phase transition cannot occur without nucleating handful of bubbles in the entire Hubble volume. The presence of domain walls during the transition may, however, significantly alter the dynamics of the phase transitions. Using lattice simulation, we demonstrate that vacuum fluctuations induce the destabilization of the domain walls that will classically transform into the domain trenches of the true vacuum, resulting in successful phase transitions without bubbles. After providing an analytical method to estimate the temperature at which the domain trenches are produced, we take the Z2-odd singlet model as an example and conclude that the bubble-free mechanism developed in this Letter constitutes a competing means of completing the phase transition against with quantum tunneling, opening up the new viable parameter region.

   hep-phgr-qchep-lat5 citations
4. 04*

   Vacuum Stability in the Standard Model and Beyond

   Gudrun Hiller🇩🇪 · Tim Höhne🇩🇪 · Daniel F. Litim🇬🇧 · Tom Steudtner🇩🇪

   We revisit the stability of the Standard Model vacuum, and investigate its quantum effective potential using the highest available orders in perturbation theory and the most accurate determination of input parameters to date. We observe that the stability of the electroweak vacuum centrally depends on the values of the top mass and the strong coupling constant. We estimate that reducing their uncertainties by a factor of two to three is sufficient to establish or refute SM vacuum stability at the $5\sigma$ level. We further investigate vacuum stability for a variety of singlet scalar field extensions with and without flavor using the Higgs portal mechanism. We identify the BSM parameter spaces for stability and find sizable room for new physics. We further study the phenomenology of Planck-safe models at colliders, and determine the impact on the Higgs trilinear, the Higgs-to-electroweak-boson, and the Higgs quartic couplings, some of which can be significant. The former two can be probed at the HL-LHC, the latter requires a future collider with sufficient energy and precision such as the FCC-hh.

   hep-phhep-thPRD(2024)·56 citations
5. 05*

   Dark Matter searches with photons at the LHC

   Subhojit Roy🇺🇸 · Carlos E.M. Wagner🇺🇸

   We unveil blind spot regions in dark matter (DM) direct detection (DMDD), for weakly interacting massive particles with a mass around a few hundred~GeV that may reveal interesting photon signals at the LHC. We explore a scenario where the DM primarily originates from the singlet sector within the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM). A novel DMDD spin-independent blind spot condition is revealed for singlino-dominated DM, in cases where the mass parameters of the higgsino and the singlino-dominated lightest supersymmetric particle (LSP) exhibit opposite relative signs (i.e., $\kappa <0$), emphasizing the role of nearby bino and higgsino-like states in tempering the singlino-dominated LSP. Additionally, proximate bino and/or higgsino states can act as co-annihilation partner(s) for singlino-dominated DM, ensuring agreement with the observed relic abundance of DM. Remarkably, in scenarios involving singlino-higgsino co-annihilation, higgsino-like neutralinos can distinctly favor radiative decay modes into the singlino-dominated LSP and a photon, as opposed to decays into leptons/hadrons. In exploring this region of parameter space within the singlino-higgsino compressed scenario, we study the signal associated with at least one relatively soft photon alongside a lepton, accompanied by substantial missing transverse energy and a hard initial state radiation jet at the LHC. In the context of singlino-bino co-annihilation, the bino state, as the next-to-LSP, exhibits significant radiative decay into a soft photon and the LSP, enabling the possible exploration at the LHC through the triggering of this soft photon alongside large missing transverse energy and relatively hard leptons/jets resulting from the decay of heavier higgsino-like states.

   hep-phhep-thJHEP(2024)·16 citations
6. 06*

   Mass suppression effect in QCD radiation and hadron angular distribution in jet

   Chuan-Hui Jiang🇨🇳 · Hai Tao Li🇨🇳 · Shi-Yuan Li🇨🇳 · Zong-Guo Si🇨🇳

   The finite mass of the heavy quark suppresses the collimated radiations, which is generally referred to as the dead cone effect. In this paper, we study the distribution of hadron multiplicity over the hadron opening angle with respect to the jet axis in various flavors of jets. The corresponding measurement can be the most straightforward and simplest to explore the dynamical evolution of the radiations in the corresponding jet, which can expose the mass effect. We also propose the transverse energy-weighted angular distribution which sheds light on the interplay between perturbative and nonperturbative effects in the radiation. With Monte-Carlo simulations, our calculation shows that the dead cone effect can be clearly seen by taking the ratio between the b jet and the light-quark (inclusive) jet, promising to be measured at the LHC in the future.

   hep-phhep-exnucl-thCPC(2024)·3 citations
7. 07*

   A unified scheme for calculating the exclusive semi-leptonic decays of hadrons

   Guo-He Yang🇨🇳

   Exclusive semi-leptonic decay stands as a pivotal channel in the exploration of heavy flavor physics, primarily due to its straightforward experimental measurability. In this work, we delve into the hadron matrix element and hadron tensor within the context of exclusive semi-leptonic decays. We challenge the conventional exclusive decay theory by introducing a fresh perspective, revealing that while the baryon sector is consistent, the meson sector warrants revision. Employing a novel form factor derived from the Taylor series expansion in our differential width calculations, we demonstrate that fitting experimental data necessitates a more streamlined and minimal parameter set compared to the standard Light Cone Sun Rul(LCSR) form factors. Furthermore, we propose that our hypothesis can be empirically validated or refuted through the precise measurement of the double differential decay width, offering a tangible path forward for experimental validation.

   hep-phhep-thJ.Phys.G(2025)·0 citations
8. 08*

   Accelerating HEP simulations with Neural Importance Sampling

   Nicolas Deutschmann🇨🇭 · Niklas Götz🇩🇪

   Many high-energy-physics (HEP) simulations for the LHC rely on Monte Carlo using importance sampling by means of the VEGAS algorithm. However, complex high-precision calculations have become a challenge for the standard toolbox, as this approach suffers from poor performance in complex cases. As a result, there has been keen interest in HEP for modern machine learning to power adaptive sampling. While previous studies have shown the potential of normalizing-flow-powered neural importance sampling (NIS) over VEGAS, there remains a gap in accessible tools tailored for non-experts. In response, we introduce ZüNIS, a fully automated NIS library designed to bridge this divide, while at the same time providing the infrastructure to customise the algorithm for dealing with challenging tasks. After a general introduction on NIS, we first show how to extend the original formulation of NIS to reuse samples over multiple gradient steps while guaranteeing a stable training, yielding a significant improvement for slow functions. Next, we introduce the structure of the library, which can be used by non-experts with minimal effort and is extensivly documented, which is crucial to become a mature tool for the wider HEP public. We present systematic benchmark results on both toy and physics examples, and stress the benefit of providing different survey strategies, which allows higher performance in challenging cases. We show that ZüNIS shows high performance on a range of problems with limited fine-tuning.

   hep-phhep-exhep-thphysics.comp-ph+1JHEP(2024)·36 citations
9. 09*

   Limiting attractors in heavy-ion collisions -- the interplay between bottom-up and hydrodynamic attractors

   Kirill Boguslavski🇦🇹 · Aleksi Kurkela🇳🇴 · Tuomas Lappi🇫🇮 · Florian Lindenbauer🇦🇹 · Jarkko Peuron🇫🇮

   In this contribution to the Quark Matter 2023 proceedings, we study the hydrodynamization process in heavy-ion collisions using QCD kinetic theory and introduce the new concept of limiting attractors. They are defined via an extrapolation of observables to vanishing and infinite couplings. We find that the pressure ratio exhibits both a hydrodynamic and a bottom-up limiting attractor, while the ratios of hard probes transport coefficients ${\hat{q}}^{zz}/{\hat{q}}^{yy}$ and ${\kappa }_T/{\kappa }_z$ are better described in terms of the new bottom-up limiting attractor.

   hep-phnucl-thEPJ Web Conf.(2024)·2 citations
10. 10*

    Properties of $Q^{5}q$ dibaryons

    Xin-Zhen Weng🇮🇱

    We investigate heavy flavor dibaryons with five heavy quarks $Q$ ($Q=\{c,b\}$) and one light quark $q$ ($q=\{u,d,s\}$), namely the $Q^{5}q$ dibaryons. In the framework of an extended chromomagnetic model, we systematically study the mass spectrum of these dibaryons. We find no stable state below the corresponding baryon-baryon thresholds. In addition to the analysis of the masses, we also study their two body decay properties by estimating the relative width ratios of the decay channels. We hope our study will be of help for future experiments.

    hep-ph2 citations
11. 11*

    Machine Learning for Prediction of Unitarity and Bounded from Below Constraints

    Darius Jurčiukonis🇱🇹

    The machine learning (ML) techniques to predict unitarity (UNI) and bounded from below (BFB) constraints in multi-scalar models is employed. The effectiveness of this approach is demonstrated by applying it to the two and three Higgs doublet models, as well as the left-right model. By employing suitable neural network architectures, learning algorithms, and carefully curated training datasets, a significantly high level of predictivity is achieved. Machine learning offers a distinct advantage by enabling faster calculations compared to alternative numerical methods, such as scalar potential minimization. This research investigates the feasibility of utilizing machine learning techniques as an alternative for predicting these constraints, offering potential improvements over traditional numerical calculations.

    hep-phPoS(2024)·1 citation
12. 12*

    Gravitational waves and primordial black holes from axion domain walls in level crossing

    Hai-Jun Li🇨🇳 · Yu-Feng Zhou🇨🇳

    In this paper, we investigate the nano-Hertz gravitational waves (GWs) emission and the massive primordial black holes (PBHs) formation from the light QCD axion scenario. We consider the axion domain walls formation from the level crossing induced by the mass mixing between the light $Z_{\mathcal{N}}$ QCD axion and axion-like particle. A general mixing case is considered that the heavy and light mass eigenvalues do not necessarily have to coincide with the axion masses. In order to form the domain walls, the axions should start to oscillate slightly before the level crossing. The domain walls must annihilate before dominating the Universe to avoid the cosmological catastrophe. Then we focus our attention on the GWs emission from the domain walls annihilation and the PBHs formation from the domain walls collapse. We show the predicted GWs spectra with the peak frequency $\sim 0.2\mathrm{nHz}$ and the peak amplitude $\sim 5\times 10^{-9}$, which can be tested by the future pulsar timing array projects. In addition, during the domain walls annihilation, the closed walls could shrink to the Schwarzschild radius and collapse into the PBHs. We find that the PBHs in the mass range of $\mathcal{O}(10^5-10^8)M_{\odot }$ could potentially form in this scenario and account for a small fraction $\sim 10^{-5}$ of the cold dark matter.

    hep-phastro-ph.COastro-ph.HEgr-qcCPC(2025)·15 citations
13. 13*

    A description of ${\chi }_{cJ}\to VV$ decays within the effective field theory framework

    Nikolay Kivel🇩🇪

    We study ${\chi }_{cJ}\to VV$ decays using the QCD effective field theory approach. The helicity suppressed decay amplitudes are also considered. The colour-singlet contributions of these amplitudes suffer from the endpoint singularities, it is shown that they can be absorbed into renormalisation of the nonfactorisable colour-octet matrix element. The latter can be associated with the colour-octet component of the charmonium wave function. The heavy quark spin symmetry makes it possible to establish the relationships between colour-octet matrix elements for different states ${\chi }_{cJ}$ up to higher order corrections in small velocity $v$. This allows us to estimate the polarisation parameters for ${\chi }_{c2}\to VV$ using data for ${\chi }_{c0,1}\to VV$. This analysis is carried out for the available data on the ${\chi }_{cJ}\to \varphi \varphi$ decays.

    hep-phJHEP(2024)·2 citations
14. 14*

    Topological Portal to the Dark Sector

    Joe Davighi🇨🇭 · Admir Greljo🇨🇭 · Nudzeim Selimovic🇮🇹

    We propose a unique topological portal between quantum chromodynamics (QCD) and a dark sector characterized by a global symmetry breaking, which connects three QCD to two dark pions. When gauged, it serves as the leading portal between the two sectors, providing an elegant, self-consistent scenario of light thermal inelastic dark matter. The inherent antisymmetrization leads to diminished annihilations at later times and suppressed direct detection. However, novel collider signatures offer tremendous prospects for discovery at Belle II.

    hep-phhep-exhep-thPRL(2025)·21 citations
15. 15*

    Beam-Dump Ceiling and Its Experimental Implication: The Case of a Portable Experiment

    Doojin Kim🇺🇸 · Jaehoon Yu🇺🇸 · Jong-Chul Park🇰🇷 · Hyunyong Kim🇺🇸

    We generalize the nature of the so-called beam-dump ``ceiling'' beyond which the improvement on the sensitivity reach in the search for fast-decaying mediators dramatically slows down, and we point out its experimental implications that motivate tabletop-sized beam-dump experiments for the search. Light (bosonic) mediators are well-motivated new-physics particles as they can appear in dark-sector portal scenarios and models to explain various laboratory-based anomalies. Due to their low mass and feebly interacting nature, beam-dump-type experiments, utilizing high-intensity particle beams can play a crucial role in probing the parameter space of such visibly decaying mediators, in particular, the ``prompt-decay'' region, where the mediators feature relatively large coupling and mass. We present a general and semianalytic proof that the ceiling effectively arises in the prompt-decay region of an experiment and show its insensitivity to data statistics, background estimates, and systematic uncertainties, considering a concrete example, the search for axion-like particles interacting with ordinary photons at three benchmark beam facilities: PIP-II at FNAL and SPS and LHC-dump at CERN. We then identify optimal criteria to perform a cost-effective and short-term experiment to reach the ceiling, demonstrating that very short-baseline compact experiments enable access to the parameter space unreachable thus far.

    hep-phhep-exPRD(2026)·8 citations
16. 16*

    Limits on Non-Relativistic Matter During Big-Bang Nucleosynthesis

    Tsung-Han Yeh🇨🇦 · Keith A. Olive🇺🇸 · Brian D. Fields🇺🇸

    Big-bang nucleosynthesis (BBN) probes the cosmic mass-energy density at temperatures $\sim 10$ MeV to $\sim 100$ keV. Here, we consider the effect of a cosmic matter-like species that is non-relativistic and pressureless during BBN. Such a component must decay; doing so during BBN can alter the baryon-to-photon ratio, $\eta$, and the effective number of neutrino species. We use light element abundances and the cosmic microwave background (CMB) constraints on $\eta$ and $N_{\nu }$ to place constraints on such a matter component. We find that electromagnetic decays heat the photons relative to neutrinos, and thus dilute the effective number of relativistic species to $N_{\mathrm{eff}}<3$ for the case of three Standard Model neutrino species. Intriguingly, likelihood results based on {\em Planck} CMB data alone find $N_{\nu }=2.800\pm 0.294$, and when combined with standard BBN and the observations of D and \he4 give $N_{\nu }=2.898\pm 0.141$. While both results are consistent with the Standard Model, we find that a nonzero abundance of electromagnetically decaying matter gives a better fit to these results. Our best-fit results are for a matter species that decays entirely electromagnetically with a lifetime ${\tau }_X=0.89\sec$ and pre-decay density that is a fraction $\xi =({\rho }_X/{\rho }_{\mathrm{rad}}){|}_{10\mathrm{MeV}}=0.0026$ of the radiation energy density at 10 MeV; similarly good fits are found over a range where $\xi {\tau }_X^{1/2}$ is constant. On the other hand, decaying matter often spoils the BBN+CMB concordance, and we present limits in the $({\tau }_X,\xi )$ plane for both electromagnetic and invisible decays. For dark (invisible) decays, standard BBN (i.e. $\xi =0$) supplies the best fit. We end with a brief discussion of the impact of future measurements including CMB-S4.

    ↳ astro-ph.COhep-phJCAP(2024)·12 citations
17. 17*

    Detecting Dark Matter Substructures on Small Scales with Fast Radio Bursts

    Huangyu Xiao🇺🇸 · Liang Dai🇺🇸 · Matthew McQuinn🇺🇸

    We propose measuring the arrival time difference of Fast Radio Bursts (FRBs) along two adjacent sightlines as a new probe to dark matter substructures on scales down to $\sim 1$AU. We discuss two observational scenarios in which it may be possible to place interesting constraints on such models through monitoring repeating FRB sources: 1) By sending radio receivers to space to form a baseline of tens of AU or more and measuring the temporal variation of the arrival time difference between receivers. 2) By measuring the temporal variation of the arrival time difference between two lensed images of one strongly lensed repeater. In both scenarios, obtaining interesting constraints requires correlating the voltage time series to measure the radio-signal arrival time to sub-nanosecond precision. We find that two radio dishes separated by $20$AU may be sensitive to the enhancement of small-scale structures at $\sim 10^{-8}{M}_{\odot }$ masses in the QCD axion dark matter scenario or from an early epoch of matter-domination with a reheating temperature up to 60 MeV. Other dark matter models such as those composed of $\sim 10^{-13}{M}_{\odot }$ primordial black holes produced during inflation would also be probed by this method. We further show that a strong lensing situation of multiple images provides an equivalent $\sim 2000$AU baseline, which can be much more sensitive but with the uncertainty that intervening ISM decoherence may degrade the timing precision and that spatial variation in the FRB emission spot may result in confounding signals. We show that the lensing magnifications of Type Ia supernovea constrain a similar quantity to such FRB timing, with present limits being equivalent to ruling out the same parameter space that would be probed by a $0.14$AU baseline.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phPRD(2024)·29 citations
18. 18*

    On gravity as a medium property in Maxwell equations

    Jai-chan Hwang🇰🇷 · Hyerim Noh🇰🇷

    The effect of gravity in Maxwell's equations is often treated as a medium property. The commonly used formulation is based on managing Maxwell's equations in exactly the same form as in Minkowski spacetime and expressing the effect of gravity as a set of constitutive relations. We show that such a set of Maxwell's equations is, in fact, a combination of the electric and magnetic fields defined in two different non-covariant ways, both of which fail to identify the associated observer's four-vectors. The suggested constitutive relations are also ad hoc and unjustified. To an observer with a proper four-vector, the effect of gravity can be arranged as effective polarizations and magnetizations appearing in both the homogeneous and inhomogeneous parts. Modifying the homogeneous part by gravity is inevitable to any observer, and the result cannot be interpreted as the medium property. For optical properties one should directly handle Maxwell's equations in curved spacetime.

    ↳ gr-qcastro-ph.HEhep-phGen.Rel.Grav.(2024)·2 citations
19. 19*

    Higher Derivative Supergravities in Diverse Dimensions

    Mehmet Ozkan🇹🇷 · Yi Pang🇨🇳 · Ergin Sezgin🇺🇸

    We survey on-shell and off-shell higher derivative supergravities in dimensions $1\le D\le 11$. Various approaches to their construction, including the Noether procedure, (harmonic) superspace, superform method, superconformal tensor calculus, $S$-matrix and dimensional reduction, are summarized. Primarily the bosonic parts of the invariants and the supertransformations of the fermionic fields are provided. The process of going on-shell, solutions to the Killing spinor equations, typical supersymmetric solutions, and the role of duality symmetries in the context of $R^4,D^4{R}^4$ and $D^6{R}^4$ invariants are reviewed.

    ↳ hep-thgr-qchep-phmath-ph+1Phys.Rept.(2024)·44 citations
20. 20*

    The Dark Dimension, the Swampland, and the Dark Matter Fraction Composed of Primordial Near-Extremal Black Holes

    Luis A. Anchordoqui🇺🇸 · Ignatios Antoniadis🇹🇭 · Dieter Lust🇩🇪

    In a recent publication we studied the decay rate of primordial black holes perceiving the dark dimension, an innovative five-dimensional (5D) scenario that has a compact space with characteristic length-scale in the micron range. We demonstrated that the rate of Hawking radiation of 5D black holes slows down compared to 4D black holes of the same mass. Armed with our findings we showed that for a species scale of $\mathcal{O}(10^9\mathrm{GeV})$, an all-dark-matter interpretation in terms of primordial black holes should be feasible for black hole masses in the range $10^{14}\lesssim M/\mathrm{g}\lesssim 10^{21}$. As a natural outgrowth of our recent study, herein we calculate the Hawking evaporation of near-extremal 5D black holes. Using generic entropy arguments we demonstrate that Hawking evaporation of higher-dimensional near-extremal black holes proceeds at a slower rate than the corresponding Schwarzschild black holes of the same mass. Assisted by this result we show that if there were 5D primordial near-extremal black holes in nature, then a PBH all-dark-matter interpretation would be possible in the mass range $10^7\sqrt{\beta }\lesssim M/\mathrm{g}\lesssim 10^{21}$, where $\beta$ is a parameter that controls the difference between mass and charge of the associated near-extremal black hole.

    ↳ hep-thhep-phPRD(2024)·36 citations
21. 21*

    Progress and Challenges in Small Systems

    Jorge Noronha🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸

    We present a comprehensive review of the theoretical and experimental progress in the investigation of novel high-temperature quantum chromodynamics phenomena in small systems at both the Relativistic Heavy Ion Collider and the Large Hadron Collider. We highlight the challenges and opportunities associated with studying small systems, by which we generally mean collision systems that involve at least one light ion or even a photon projectile. We discuss perspectives on possible future research directions to better understand the underlying physics at work in the collisions of small systems.

    ↳ nucl-thhep-phIJMPE(2024)·63 citations
22. 22*

    Inflationary Krylov complexity

    Tao Li🇨🇳 · Lei-Hua Liu🇨🇳

    In this work, we have systematically investigated the Krylov complexity of curvature perturbation for the modified dispersion relation in inflation, using the algorithm in closed system and open system. Our analysis could be applied to the most inflationary models. Following the Lanczos algorithm, we find the very early universe is an infinite, many-body, and maximal chaotic system. Our numerics shows that the Lanczos coefficient and Lyapunov index of the standard dispersion relation are mainly determined by the scale factor. As for the modified case, it is nearly determined by the momentum. In a method of the closed system, we discover that the Krylov complexity will show irregular oscillation before the horizon exits. The modified case will present faster growth after the horizon exists. Since the whole universe is an open system, the approach of an open system is more realistic and reliable. Then, we construct the exact wave function which is very robust only requiring the Lanczos coefficient proportional to $n$ (main quantum number). Based on it, we find the Krylov complexity and Krylov entropy could nicely recover in the case of a closed system under the weak dissipative approximation, in which our analysis shows that the evolution of Krylov complexity will not be the same with the original situation. We also find the inflationary period is a strong dissipative system. Meanwhile, our numerics clearly shows the Krylov complexity will grow during the whole inflationary period. But for the small scales, there will be a peak after the horizon exits. Our analysis reveals that the dramatic change in background (inflation) will significantly impact the evolution of Krylov complexity. Since the curvature perturbation will transit from the quantum level to the classical level.

    ↳ hep-thastro-ph.COgr-qchep-ph+1JHEP(2024)·29 citations
23. 23*

    On the structure of the large-$N$ expansion in SU($N$) Yang-Mills theory

    Marco Bochicchio🇮🇹 · Mauro Papinutto🇮🇹 · Francesco Scardino🇮🇹

    Recently, we have computed the short-distance asymptotics of the generating functional of Euclidean correlators of single-trace twist-$2$ operators in the large-$N$ expansion of SU($N$) Yang-Mills (YM) theory to the leading-nonplanar order. Remarkably, it has the structure of the logarithm of a functional determinant, but with the sign opposite to the one that would follow from the spin-statistics theorem for the glueballs. In order to solve this sign puzzle, we have reconsidered the proof in the literature that in the 't Hooft topological expansion of large-$N$ YM theory the leading-nonplanar contribution to the generating functional consists of the sum over punctures of $n$-punctured tori. We have discovered that for twist-$2$ operators it contains -- in addition to the $n$-punctured tori -- the normalization of tori with $1\le p\le n$ pinches and $n-p$ punctures. Once the existence of the new sector is taken into account, the violation of the spin-statistics theorem disappears. Moreover, the new sector contributes trivially to the nonperturbative $S$ matrix because -- for example -- the $n$-pinched torus represents nonperturbatively a loop of $n$ glueball propagators with no external leg. This opens the way for an exact solution limited to the new sector that may be solvable thanks to the vanishing $S$ matrix.

    ↳ hep-thhep-phNPB(2025)·7 citations
24. 24*

    Deuteron gravitational form factors: exchange currents

    Fangcheng He🇺🇸 · Ismail Zahed🇺🇸

    Following on our recent analysis of the energy momentum tensor (EMT) of light nuclei in the impulse approximation, we evaluate the leading exchange corrections also upto momenta of the order of the nucleon mass. The exchange contributions to the EMT, are composed of the pair interaction, plus the seagull and the pion exchange interactions, modulo the recoil correction. The exchange contributions are shown to satisfy the current conservation requirement. These contributions are small compared to those from the impulse approximation for most of the deuteron gravitational form factors (GFFs), for momenta smaller than half of the nucleon mass. For larger momenta, the exchange contributions are significant for the deuteron A- and D-GFFs. We suggest that the pion GFFs can be extracted from the exchange contributions of select deuteron GFFs.

    ↳ nucl-thhep-phPRC(2024)·7 citations
25. 25*

    Slaying Axion-Like Particles via Gravitational Waves and Primordial Black Holes from Supercooled Phase Transition

    Angela Conaci🇮🇹 · Luigi Delle Rose🇮🇹 · P. S. Bhupal Dev🇺🇸 · Anish Ghoshal🇵🇱

    We study the formation of primordial black holes (PBHs) from density fluctuations due to supercooled phase transitions (PTs) triggered in an axion-like particle (ALP) model. We find that the mass of the PBHs is inversely correlated with the ALP decay constant $f_a$. For instance, for $f_a$ varying from $\mathcal{O}$(100 MeV) to $\mathcal{O}$($10^{12}$ GeV), the PBH mass varies between $(10^3-10^{-24})M_{\odot }$. We then identify the ALP parameter space where the PBH can account for the entire (or partial) dark matter fraction of the Universe, in a single (multi-component) dark matter scenario, with the ALP being the other dark matter candidate. The PBH parameter space ruled out by current cosmological and microlensing observations can thus be directly mapped onto the ALP parameter space, thus providing new bounds on ALPs, complementary to the laboratory and astrophysical ALP constraints. Similarly, depending on the ALP couplings to other Standard Model particles, the ALP constraints on $f_a$ can be translated into a lower bound on the PBH mass scale. Moreover, the supercooled PT leads to a potentially observable stochastic gravitational wave (GW) signal at future GW observatories, such as aLIGO, LISA and ET, that acts as another complementary probe of the ALPs, as well as of the PBH dark matter. Finally, we show that the recent NANOGrav signal of stochastic GW in the nHz frequency range can be explained in our model with $f_a\simeq (10\mathrm{GeV}-1\mathrm{TeV})$.

    ↳ astro-ph.COhep-phhep-thJHEP(2024)·38 citations
26. 26*

    Could Sample Variance be Responsible for the Parity-Violating Signal Seen in the BOSS Galaxy Survey?

    Oliver H. E. Philcox🇺🇸 · Julia Ereza🇪🇸

    Recent works have uncovered an excess signal in the parity-odd four-point correlation function measured from the BOSS spectroscopic galaxy survey. If physical in origin, this could indicate evidence for new parity-breaking processes in the scalar sector, most likely from inflation. At heart, these studies compare the observed four-point correlator to the distribution obtained from parity-conserving mock galaxy surveys; if the simulations underestimate the covariance of the data, noise fluctuations may be misinterpreted as a signal. To test this, we reanalyse the BOSS CMASS + LOWZ parity-odd dataset with the noise distribution modeled using the newly developed GLAM-Uchuu suite of mocks. These comprise full N-body simulations that follow the evolution of $2000^3$ dark matter particles in a $\Lambda$CDM universe, and represent a significant upgrade compared to the formerly MultiDark-Patchy mocks, which were based on an alternative (non N-body) gravity solver. We find no significant evidence for parity-violation in the BOSS dataset (with a baseline detection significance of $1.4\sigma$), suggesting that the former signal ($>3.5\sigma$ with our data cuts) could be caused by an underestimation of the covariance in MultiDark-Patchy. The significant differences between results obtained with the two sets of BOSS-calibrated galaxy catalogs showcases the heightened sensitivity of beyond-two-point analyses to the treatment of non-linear effects and indicates that previous constraints may suffer from large systematic uncertainties.

    ↳ astro-ph.COastro-ph.GAgr-qchep-ph+125 citations
27. 27*

    Learning New Physics from Data -- a Symmetrized Approach

    Shikma Bressler🇮🇱 · Inbar Savoray🇺🇸 · Yuval Zurgil🇮🇱

    Thousands of person-years have been invested in searches for New Physics (NP), the majority of them motivated by theoretical considerations. Yet, no evidence of beyond the Standard Model (BSM) physics has been found. This suggests that model-agnostic searches might be an important key to explore NP, and help discover unexpected phenomena which can inspire future theoretical developments. A possible strategy for such searches is identifying asymmetries between data samples that are expected to be symmetric within the Standard Model (SM). We propose exploiting neural networks (NNs) to quickly fit and statistically test the differences between two samples. Our method is based on an earlier work, originally designed for inferring the deviations of an observed dataset from that of a much larger reference dataset. We present a symmetric formalism, generalizing the original one; avoiding fine-tuning of the NN parameters and any constraints on the relative sizes of the samples. Our formalism could be used to detect small symmetry violations, extending the discovery potential of current and future particle physics experiments.

    ↳ hep-exhep-phPRD(2024)·2 citations
28. 28*

    Species Scale and Primordial Gravitational Waves

    Marco Scalisi🇩🇪

    The species scale is a field-dependent UV cut-off for any effective field theory weakly coupled to gravity. In this letter we show that, in the context of inflationary cosmology, a detection of primordial gravitational waves will set an upper bound on the decay rate $|{\Lambda }_s^{\prime }/{\Lambda }_s|$ of the species scale. Specifically, we derive this in terms of the tensor-to-scalar ratio $r$ of power spectra of primordial perturbations. Given the targets of current and next generation experiments, we show that any successful detection would signify that this upper limit is of the order of unity, which is consistent with recent discussions in the literature.

    ↳ hep-thastro-ph.COgr-qchep-phFortsch.Phys.(2024)·9 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.