Thu·Oct 12, 2023Thursday·October 12, 2023

1. 01*

   Gravitational Waves from Nnaturalness

   Brian Batell🇺🇸 · Akshay Ghalsasi🇺🇸 · Matthew Low🇺🇸 · Mudit Rai🇺🇸

   We study the prospects for probing the Nnaturalness solution to the electroweak hierarchy problem with future gravitational wave observatories. Nnaturalness, in its simplest incarnation, predicts $N$ copies of the Standard Model with varying Higgs mass parameters. We show that in certain parameter regions the scalar reheaton transfers a substantial energy density to the sector with the smallest positive Higgs squared mass while remaining consistent with bounds on additional effective relativistic species. In this sector, all six quarks are much lighter than the corresponding QCD confinement scale, allowing for the possibility of a first-order chiral symmetry-breaking phase transition and an associated stochastic gravitational wave signal. We consider several scenarios characterizing the strongly-coupled phase transition dynamics and estimate the gravitational wave spectrum for each. Pulsar timing arrays (SKA), spaced-based interferometers (BBO, Ultimate-DECIGO, $\mu$Ares, asteroid ranging), and astrometric measurements (THEIA) all have the potential to explore new regions of Nnaturalness parameter space, complementing probes from next generation cosmic microwave background radiation experiments.

   hep-phJHEP(2024)·7 citations
2. 02*

   Coherent photoproduction of light vector mesons off nuclear targets in the dipole picture

   Cheryl Henkels🇧🇷 · Emmanuel G. de Oliveira🇧🇷 · Roman Pasechnik🇸🇪 · Haimon Trebien🇧🇷

   We study the coherent photoproduction of light vector mesons in Pb-Pb collisions in the framework of color dipole approach. We employ the Glauber--Gribov formalism supplemented by an effective suppression factor $R_G$ accounting for the gluon shadowing correction. We adjust the latter to reproduce the deep inelastic structure function $F_2$ (E665) and $\rho$ meson photoproduction (ALICE) data. We achieve a good description of the available data points with $R_G=0.85$ at scale $M_{\rho }^2/4=0.15$ GeV${}^2$. In addition, employing this suppression factor, we present predictions for coherent $\rho (2S)$, $\omega (1S,2S)$ and $\varphi (1S,2S)$ photoproduction observables using the holographic vector meson wave functions.

   hep-phNPA(2025)·5 citations
3. 03*

   Quantisation Across Bubble Walls and Friction

   Aleksandr Azatov🇮🇹 · Giulio Barni🇮🇹 · Rudin Petrossian-Byrne🇮🇹 · Miguel Vanvlasselaer🇧🇪

   We quantise from first principles field theories living on the background of a bubble wall in the planar limit with particular focus on the case of spontaneous breaking of gauge symmetry. Using these tools, we compute the average momentum transfer from transition radiation: the soft emission of radiation by an energetic particle passing across the wall, with a particular focus on the longitudinal polarisation of vectors. We find these to be comparable to transverse polarisations in symmetry-breaking transitions with mild super-cooling, and dominant in broken to broken transitions with thin wall. Our results have phenomenological applications for the expansion of bubbles during first order phase transitions. Our general framework allows for the robust calculation of any particle processes of interest in such translation breaking backgrounds.

   hep-phastro-ph.COhep-thJHEP(2024)·54 citations
4. 04*

   Probing self-interacting sterile neutrino dark matter with the diffuse supernova neutrino background

   A. Baha Balantekin🇺🇸 · George M. Fuller🇺🇸 · Anupam Ray🇺🇸 · Anna M. Suliga🇺🇸

   The neutrinos in the diffuse supernova neutrino background (DSNB) travel over cosmological distances and this provides them with an excellent opportunity to interact with dark relics. We show that a cosmologically-significant relic population of keV-mass sterile neutrinos with strong self-interactions could imprint their presence in the DSNB. The signatures of the self-interactions would be ``dips" in the otherwise smooth DSNB spectrum. Upcoming large-scale neutrino detectors, for example Hyper-Kamiokande, have a good chance of detecting the DSNB and these dips. If no dips are detected, this method serves as an independent constraint on the sterile neutrino self-interaction strength and mixing with active neutrinos. We show that relic sterile neutrino parameters that evade X-ray and structure bounds may nevertheless be testable by future detectors like TRISTAN, but may also produce dips in the DSNB which could be detectable. Such a detection would suggest the existence of a cosmologically-significant, strongly self-interacting sterile neutrino background, likely embedded in a richer dark sector.

   hep-phastro-ph.COastro-ph.HEPRD(2023)·21 citations
5. 05*

   Search for WIMPs at future ${\mu }^{+}{\mu }^{+}$ colliders

   Hajime Fukuda🇯🇵 · Takeo Moroi🇯🇵 · Atsuya Niki🇯🇵 · Shang-Fu Wei🇯🇵

   Weakly interacting massive particles (WIMPs) with electroweak charges, such as the wino and the Higgsino, stand out as natural candidates for dark matter in the universe. In this paper, we study the search for WIMPs at future multi-TeV ${\mu }^{+}{\mu }^{+}$ colliders. We investigate both the direct production search of WIMPs through the mono-muon channel and the indirect search through quantum corrections in elastic ${\mu }^{+}{\mu }^{+}$ Moller scattering. We find that the indirect search has an advantage over the direct search with sufficient luminosities, $\mathcal{O}({\text{ab}}^{-1})$, and low systematic uncertainties, $\lesssim 0.3\%$. This advantage arises due to the weaker mass dependence observed in the indirect search in comparison to direct production methods. The advantage is further enhanced if the initial muon beams are polarized. Specifically, we demonstrate that the indirect search method can detect the thermal mass target for the wino and the Higgsino for $\sqrt{s}=6\text{TeV}$ and $2\text{TeV}$ (with $\sqrt{s}$ being the center of mass energy), respectively, with $10{\text{ab}}^{-1}$, an $80\%$ polarized beam and an accuracy of $0.1\%$. Our findings illuminate the potential of future high-energy ${\mu }^{+}{\mu }^{+}$ colliders in advancing our understanding of dark matter.

   hep-phhep-exJHEP(2024)·22 citations
6. 06*

   Modern topics in relativistic spin dynamics and magnetism

   Andrew Steinmetz🇺🇸

   Magnetism is a rich subject touching all aspects of physics. My goal with this dissertation is to explore spin and magnetic moments in \emph{relativistic} mechanics from both a quantum and classical perspective. We emphasize the special case of gyromagnetic ratio $g=2$ and its relationship to the algebraic spin structure of wave equations. In relativistic quantum mechanics, we investigate generalizations of the Dirac equation for arbitrary magnetic moments for fermions. We analyze the homogeneous magnetic field case and the Coulomb problem for hydrogen-like atoms with emphasis on the role of the anomalous magnetic moment (AMM). We explore alternative approaches which combine mass and the magnetic moment. Classically, we propose a relativistic covariant model of the Stern-Gerlach force via the introduction of a magnetic four-potential. This model modifies the covariant torque equations and unites the Ampèrian and Gilbertian models for magnetic moments. We further study (transition) magnetic dipoles in Majorana neutrinos specifically analyzing the relationship between flavor mixing and electromagnetic (EM) fields. We demonstrate EM flavor mixing explicitly in the 2-flavor model and develop a dynamical mass basis with an EM rotation matrix. EM induced neutrino mass splitting is compared to neutrino mass hierarchy. An interesting application of these theoretical developments is to study primordial magnetization in the early universe during the hot dense electron-positron plasma epoch. We propose a model of magnetic thermal matter-antimatter plasmas. We analyze the paramagnetic characteristics of electron-positron plasma when exposed to an external primordial field. Future research outlooks include: Second order equations for anomalous quantum chromodynamic (QCD) moments, neutrino CP violation in strong EM fields, and fifth-dimension spin dynamics in Kaluza-Klein theory.

   hep-phastro-ph.CO3 citations
7. 07*

   Dynamically generated states from the $\eta K^{\ast }{\bar{K}}^{\ast }$, $\pi K^{\ast }{\bar{K}}^{\ast }$, and $K{K}^{\ast }{\bar{K}}^{\ast }$ systems within the fixed-center approximation

   Qing-Hua Shen🇨🇳 · Xu Zhang🇨🇳 · Xiang Liu🇨🇳 · Ju-Jun Xie🇨🇳

   The three-body systems $\eta K^{\ast }{\bar{K}}^{\ast }$, $\pi K^{\ast }{\bar{K}}^{\ast }$, and $K{K}^{\ast }{\bar{K}}^{\ast }$ are further investigated within the framework of fixed-center approximation, where $K^{\ast }{\bar{K}}^{\ast }$ is treated as the fixed-center, corresponding to the possible scalar meson $a_0(1780)$ or the tensor meson $f_2^{\prime }(1525)$. The interactions between $\eta$, $\pi$, $K$, and $K^{\ast }$ are taken from the chiral unitary approach. The resonance structures appear in the modulus squared of the three-body scattering amplitude and suggest that $\eta /\pi /K$-$(K^{\ast }{\bar{K}}^{\ast }{)}_{a_0(1780)/f_2^{\prime }(1525)}$ hadron state can be formed. By scattering the $\eta$ meson on the fixed-center $(K^{\ast }{\bar{K}}^{\ast }{)}_{a_0(1780)}$, it is found that there is a distinct peak around 2100 MeV, as shown in the modulus squared of the three-body scattering amplitude, which can be associated with the meson $\pi (2070)$. For the scattering of the $\eta$ meson on the $(K^{\ast }{\bar{K}}^{\ast }{)}_{f_2^{\prime }(1525)}$, a resonance structure around 1890 MeV is found and it can be associated with the ${\eta }_2(1870)$ meson. Other resonance structures are also found and can be associated with ${\pi }_2(1880)$ and $\eta (2010)$.

   hep-phhep-exnucl-exnucl-thPRD(2024)·2 citations
8. 08*

   Two-Loop QCD Corrections to C even Bottomonium Exclusive Decays to Double $J/\psi$

   Yu-Dong Zhang🇨🇳 · Xiao-Wei Bai🇨🇳 · Feng Feng🇨🇳 · Wen-Long Sang🇨🇳 · Ming-Zhen Zhou🇨🇳

   In the framework of nonrelativistic QCD (NRQCD) factorization, we compute both the polarized and the unpolarized decay widths for the processes ${\eta }_b({\chi }_{bJ})\to J/\psi J/\psi$, accurate up to next-to-next-to-leading-order (NNLO) in ${\alpha }_s$. For the first time, we confirm that the NRQCD factorization does hold at NNLO for the process involving triple quarkonia. We find the radiative corrections are considerable. In particular for ${\chi }_{b2}$, both $\mathcal{O}({\alpha }_s)$ and $\mathcal{O}({\alpha }_s^2)$ corrections are sizable and negative, and can significantly reduce the leading order prediction. At NNLO, the branching fractions are $8.2\times 10^{-7}$, $6.2\times 10^{-6}$, $7.2\times 10^{-7}$ and $2.7\times 10^{-6}$ for ${\eta }_b$, ${\chi }_{b0}$, ${\chi }_{b1}$ and ${\chi }_{b2}$ decay, respectively. Our theoretical predictions are consistent with the upper limits measured by the {\tt Belle} Collaboration. Moreover, we investigate the dependence of the theoretical predictions on the ratio of the charm quark mass and the bottom quark mass. By fixing $m_b$ and varying $m_c$ from $1.25$ to $1.9$ GeV, we find the branching fraction can change a factor of $2$, $3$, and $6$ for ${\eta }_b$, ${\chi }_{b0}$, and ${\chi }_{b1}$, respectively. In the phenomenological analysis, with the integrate luminosity $\mathcal{L}=100{\mathrm{fb}}^{-1}$, we expect about $(5-10)\times 10^3$ ${\eta }_b({\chi }_{bJ})\to J/\psi J/\psi \to \ell \bar{\ell }\ell \bar{\ell }$ events produced at the {\tt LHC}, thus it might be hopeful to search for these processes. On the other hand, there are less than $100$ ${\eta }_b({\chi }_{bJ})\to J/\psi J/\psi$ signal events at the B factory, so it seems the experimental measurements on these channels are quite challenging based on current dataset.

   hep-phPRD(2023)·4 citations
9. 09*

   The decays $\tau \to [K^{-}{K}^0{\pi }^0,K^{-}{K}^{+}{\pi }^{-},K^0\overline{K^0}{\pi }^{-}]{\nu }_{\tau }$ in the NJL quark model

   M. K. Volkov🇷🇺 · A. A. Pivovarov🇷🇺 · K. Nurlan🇷🇺

   The $\tau$ lepton decays $\tau \to [K^{-}{K}^0{\pi }^0,K^{-}{K}^{+}{\pi }^{-},K^0\overline{K^0}{\pi }^{-}]{\nu }_{\tau }$ are described in the $U(3)\times U(3)$ NJL quark model. The contact channel and intermediate channels with axial-vector, vector and pseudoscalar mesons are taken into account. It is shown that the strange scalar meson $K_0^{\ast }$ plays an important role in these processes in addition to the intermediate vector meson $K^{\ast }$. The obtained results are in satisfactory agreement with the recent experimental data within the experimental and theoretical uncertainties.

   hep-ph0 citations
10. 10*

    Slepton searches in the trilinear RPV SUSY scenarios at the HL-LHC and HE-LHC

    Arghya Choudhury🇮🇳 · Arpita Mondal🇮🇳 · Subhadeep Mondal🇮🇳 · Subhadeep Sarkar🇮🇳

    In this work we have studied a multi-lepton final state arising from sneutrino and left-handed slepton production at the high luminosity and high energy LHC in the context of R-parity violating supersymmetry when only the lepton number violating ${\lambda }_{121}$ and/or ${\lambda }_{122}$ couplings are non-zero. We have taken into account both pair production and associated production of the three generations of left-handed sleptons and sneutrinos, which are assumed to be mass degenerate. The lightest supersymmetric particle is assumed to be bino and it decays via the R-parity violating couplings into light leptons and neutrinos. Our final state has a large lepton multiplicity, $N_l\ge 4(l=e,\mu )$. We perform both cut-based and machine learning based analyses for comparison. We present our results in the bino-slepton/sneutrino mass plane in terms of exclusion and discovery reach at the LHC. Following our analysis, the slepton mass can be discovered upto $\sim$ 1.54 TeV and excluded upto $\sim$ 1.87 TeV at the high luminosity LHC while these ranges go upto $\sim$ 2.46 TeV and $\sim$ 3.06 TeV respectively at the high energy LHC.

    hep-phEur.Phys.J.ST(2024)·11 citations
11. 11*

    Simulation of Hadronic Interactions with Deep Generative Models

    Tuan Minh Pham🇺🇸 · Xiangyang Ju🇺🇸

    Accurate simulation of detector responses to hadrons is paramount for all physics programs at the Large Hadron Collider (LHC). Central to this simulation is the modeling of hadronic interactions. Unfortunately, the absence of first-principle theoretical guidance has made this a formidable challenge. The state-of-the-art simulation tool, \textsc{Geant4}, currently relies on phenomenology-inspired parametric models. Each model is designed to simulate hadronic interactions within specific energy ranges and for particular types of hadrons. Despite dedicated tuning efforts, these models sometimes fail to describe the data in certain physics processes accurately. Furthermore, fine-tuning these models with new measurements is laborious. Our research endeavors to leverage generative models to simulate hadronic interactions. While our ultimate goal is to train a generative model using experimental data, we have taken a crucial step by training conditional normalizing flow models with \textsc{Geant4} simulation data. Our work marks a significant stride toward developing a fully differentiable and data-driven model for hadronic interactions in High Energy and Nuclear Physics.

    hep-phhep-exEPJ Web Conf.(2024)·0 citations
12. 12*

    Event Generator Tuning Incorporating Systematic Uncertainty

    Jaffae Schroff🇺🇸 · Xiangyang Ju🇺🇸

    Event generators play an important role in all physics programs at the Large Hadron Collider and beyond. Dedicated efforts are required to tune the parameters of event generators to accurately describe data. There are many tuning methods ranging from expert-based manual tuning to surrogate function-based semi-automatic tuning, to machine learning-based re-weighting. Although they scale differently with the number of generator parameters and the number of experimental observables, these methods are effective in finding optimal generator parameters. However, none of these tuning methods includes the Monte Carlo (MC) systematic uncertainties. That makes the tuning results sensitive to systematic variations. In this work, we introduce a novel method to incorporate the MC systematic uncertainties into the tuning procedure and to quantitatively evaluate uncertainties associated with the tuned parameters. Tested with a dummy example, the method results in a ${\chi }^2$ distribution that is centered around one, the optimal generator parameters are closer to the true parameters, and the estimated uncertainties are more accurate.

    hep-phhep-exphysics.data-anEPJ Web Conf.(2024)·0 citations
13. 13*

    FeAmGen.jl: A Julia Program for Feynman Amplitude Generation

    Quan-feng Wu🇨🇳 · Zhao Li🇨🇳

    FeAmGen.jl is a Julia package designed to generate Feynman diagrams and their corresponding amplitudes for various processes in particle physics. Utilizing the models in the Universal Feynman Output (UFO) format and Qgraf for diagram generation, it also employs SymEngine.jl and Form for amplitude generation. Additionally, the package offers functions for constructing Feynman integral topologies. In conclusion, FeAmGen.jl provides usability and versatility for the high precision calculations of the perturbative quantum field theory in the Standard Model or in the extensions beyond it. The corresponding codes are available at https://code.ihep.ac.cn/IHEP-Multiloop/FeAmGen.jl.git.

    hep-phComput.Phys.Commun.(2024)·4 citations
14. 14*

    Solutions of the Schrödinger equation with Quarkonium potential to predict the mass-spectra of the heavy mesons via series expansion method

    E. P. Inyang · E. P. Inyang · I. O. Akpan · E. S. William

    In this study, a quarkonium potential is adopted as the quark-antiquark interaction potential for predicting the mass spectra of heavy mesons. We solved the radial Schrödinger equation analytically using the series expansion method and obtained the energy eigenvalues. The present results are applied for predicting the mass spectra of heavy mesons such as charmonium and bottomonium. The present potential provides satisfying results in comparison with experimental data and the work of other researchers with a maximum error of 0.058 GeV

    hep-phnucl-th0 citations
15. 15*

    General backreaction force of cosmological bubble expansion

    Jun-Chen Wang🇨🇳 · Zi-Yan Yuwen🇨🇳 · Yu-Shi Hao🇨🇳 · Shao-Jiang Wang🇨🇳

    The gravitational-wave energy-density spectra from cosmological first-order phase transitions crucially depend on the terminal wall velocity of asymptotic bubble expansion when the driving force from the effective potential difference is gradually balanced by the backreaction force from the thermal plasma. Much attention has previously focused on the backreaction force acting on the bubble wall alone but overlooked the backreaction forces on the sound shell and shock-wave front, if any, which have been both numerically and analytically accomplished in our previous studies but only for a bag equation of state. In this paper, we will generalize the backreaction force on bubble expansion beyond the simple bag model.

    hep-phastro-ph.COgr-qcPRD(2024)·14 citations
16. 16*

    Precision-Machine Learning for the Matrix Element Method

    Theo Heimel🇩🇪 · Nathan Huetsch🇩🇪 · Ramon Winterhalder🇧🇪 · Tilman Plehn🇩🇪 · Anja Butter🇩🇪

    The matrix element method is the LHC inference method of choice for limited statistics. We present a dedicated machine learning framework, based on efficient phase-space integration, a learned acceptance and transfer function. It is based on a choice of INN and diffusion networks, and a transformer to solve jet combinatorics. We showcase this setup for the CP-phase of the top Yukawa coupling in associated Higgs and single-top production.

    hep-phSciPost Phys.(2024)·53 citations
17. 17*

    The classical field approximation of ultra light dark matter: quantum breaktimes, corrections, and decoherence

    Andrew Eberhardt🇯🇵 · Alvaro Zamora🇺🇸 · Michael Kopp🇸🇪 · Tom Abel🇺🇸

    The classical field approximation is widely used to better understand the predictions of ultra-light dark matter. Here, we use the truncated Wigner approximation method to test the classical field approximation of ultra-light dark matter. This method approximates a quantum state as an ensemble of independently evolving realizations drawn from its Wigner function. The method is highly parallelizable and allows the direct simulation of quantum corrections and decoherence times in systems many times larger than have been previously studied in reference to ultra-light dark matter. Our study involves simulation of systems in 1, 2, and 3 spatial dimensions. We simulate three systems, the condensation of a Gaussian random field in three spatial dimensions, a stable collapsed object in three spatial dimensions, and the merging of two stable objects in two spatial dimensions. We study the quantum corrections to the classical field theory in each case. We find that quantum corrections grow exponentially during nonlinear growth with the timescale being approximately equal to the system dynamical time. In stable systems the corrections grow quadratically. We also find that the primary effect of quantum corrections is to reduce the amplitude of fluctuations on the deBroglie scale in the spatial density. Finally, we find that the timescale associated with decoherence due to gravitational coupling to Baryonic matter is at least as fast as the quantum corrections due to gravitational interactions. These results strongly imply that quantum corrections do not impact the predictions of the classical field theory.

    ↳ astro-ph.COhep-phPRD(2024)·21 citations
18. 18*

    The Qitai Radio Telescope

    Na Wang🇨🇳 · Qian Xu · Jun Ma · Zhiyong Liu · Qi Liu🇨🇳 · Hailong Zhang · Xin Pei · Maozheng Chen🇺🇸 · Richard N. Manchester🇦🇺 · Kejia Lee🇬🇷 · Xingwu Zheng · Hans J. Kärcher and 16 other authors

    This study presents a general outline of the Qitai radio telescope (QTT) project. Qitai, the site of the telescope, is a county of Xinjiang Uygur Autonomous Region of China, located in the east Tianshan Mountains at an elevation of about 1800 m. The QTT is a fully steerable, Gregorian type telescope with a standard parabolic main reflector of 110 m diameter. The QTT has adopted an um-brella support, homology-symmetric lightweight design. The main reflector is active so that the deformation caused by gravity can be corrected. The structural design aims to ultimately allow high-sensitivity observations from 150 MHz up to 115 GHz. To satisfy the requirements for early scientific goals, the QTT will be equipped with ultra-wideband receivers and large field-of-view mul-ti-beam receivers. A multi-function signal-processing system based on RFSoC and GPU processor chips will be developed. These will enable the QTT to operate in pulsar, spectral line, continuum and Very Long Baseline Interferometer (VLBI) observing modes. Electromagnetic compatibility (EMC) and radio frequency interference (RFI) control techniques are adopted throughout the system design. The QTT will form a world-class observational platform for the detection of low-frequency (nanoHertz) gravitational waves through pulsar timing array (PTA) techniques, pulsar surveys, the discovery of binary black-hole systems, and exploring dark matter and the origin of life in the universe.

    ↳ astro-ph.IMhep-phSCPMA(2023)·14 citations
19. 19*

    Spectroscopy of hadrons with heavy quarks from lattice QCD

    Sasa Prelovsek🇸🇮

    Lattice QCD results on hadrons with heavy quarks are briefly reviewed. The focus is on the spectrum of conventional and exotic hadrons. Structure of certain conventional hadrons is addressed as well.

    ↳ hep-lathep-phNuovo Cim.C(2024)·10 citations
20. 20*

    CMB delensing with deep learning

    Shulei Ni🇺🇸 · Yichao Li🇺🇸 · Xin Zhang🇺🇸

    The cosmic microwave background (CMB) stands as a pivotal source for studying weak gravitational lensing. While the lensed CMB aids in constraining cosmological parameters, it simultaneously smooths the original CMB's features. The angular power spectrum of the unlensed CMB showcases sharper acoustic peaks and more pronounced damping tails, enhancing the precision of inferring cosmological parameters that influence these aspects. Although delensing diminishes the $B$-mode power spectrum, it facilitates the pursuit of primordial gravitational waves and enables a lower variance reconstruction of lensing and additional sources of secondary CMB anisotropies. In this work, we explore the potential of deep learning techniques, specifically the U-Net++ algorithm, to play a pivotal role in CMB delensing. We analyze three fields, namely $T$, $Q$, and $U$ sky maps, present the angular power spectra of the CMB delensed $TT$, $EE$, $BB$, and $TE$, and compare them with the unlensed CMB angular power spectra. Our findings reveal that the angular power spectrum of the lensed CMB, processed by U-Net++, closely aligns with that of the unlensed CMB. Thus, U-Net++ based CMB delensing proves to be effective in mitigating the impacts of weak gravitational lensing, paving the way for enhancing the CMB delensing power spectrum in forthcoming CMB experiments. The code utilized for this analysis is available on GitHub.

    ↳ astro-ph.COgr-qchep-phCommun.Theor.Phys.(2026)·6 citations
21. 21*

    Probing the horizon of black holes with gravitational waves

    Elisa Maggio🇩🇪

    Gravitational waves open the possibility to investigate the nature of compact objects and probe the horizons of black holes. Some models of modified gravity predict the presence of horizonless and singularity-free compact objects. Such dark compact objects would emit a gravitational-wave signal which differs from the standard black hole scenario. In this chapter, we overview the phenomenology of dark compact objects by analysing their characteristic frequencies in the ringdown and the emission of gravitational-wave echoes in the postmerger signal. We show that future gravitational-wave detectors will allow us to perform model-independent tests of the black hole paradigm.

    ↳ gr-qcastro-ph.HEhep-phhep-thLect.Notes Phys.(2023)·9 citations
22. 22*

    Constraints on a Generalization of Geometric Quantum Mechanics from Neutrino and $B^0$-$\overline{B^0}$ Oscillations

    Nabin Bhatta🇺🇸 · Djordje Minic🇺🇸 · Tatsu Takeuchi🇺🇸

    Nambu Quantum Mechanics, proposed in Phys. Lett. B536, 305 (2002), is a deformation of canonical Quantum Mechanics in which the manifold over which the "phase" of an energy eigenstate time evolves is modified. This generalization affects oscillation and interference phenomena through the introduction of two deformation parameters that quantify the extent of deviation from canonical Quantum Mechanics. In this paper, we constrain these parameters utilizing atmospheric neutrino oscillation data, and $B^0$-$\overline{B^0}$ oscillation data from Belle. Surprisingly, the bound from atmospheric neutrinos is stronger than the bound from Belle. Various features of Nambu Quantum Mechanics are also discussed.

    ↳ hep-thhep-phquant-phJHEP(2024)·1 citation
23. 23*

    Underdetermination of dark energy

    William J. Wolf🇬🇧 · Pedro G. Ferreira🇬🇧

    There is compelling evidence that the Universe is undergoing a late phase of accelerated expansion. One of the simplest explanations for this behaviour is the presence of dark energy. A plethora of microphysical models for dark energy have been proposed. The hope is that, with the ever increasing precision of cosmological surveys, it will be possible to precisely pin down the model. We show that this is unlikely and that, at best, we will have a phenomenological description for the microphysics of dark energy. Furthermore, we argue that the current phenomenological prescriptions are ill-equipped for shedding light on the fundamental theory of dark energy.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2023)·124 citations
24. 24*

    Vector dark matter production during inflation and reheating

    Jose A. R. Cembranos🇪🇸 · Luis J. Garay🇪🇸 · Álvaro Parra-López🇪🇸 · Jose M. Sánchez Velázquez🇪🇸

    Gravitational particle production of spectator fields due to the expansion universe during the inflationary and reheating phases of the early universe is of particular interest in the context of dark matter, since it allows to constrain the properties of the dark candidate by comparing the density of particles produced with the observed dark matter abundance. In such processes, tachyonic instabilities arise as a consequence of the coupling to the curvature, greatly enhancing mode production. In this work, we consider a massive vector field that is coupled to the curvature scalar and the Ricci tensor only, and study its gravitational production through inflation and reheating. We show how the mechanism is more efficient than in the case of a non-minimally coupled scalar field, giving rise to larger abundances. Moreover, we analyze the importance of the coupling to the Ricci tensor, which increases tachyonic instabilities in the system, and constrain the mass of the dark particle and the values of the coupling constants by comparing the corresponding abundance with observations

    ↳ gr-qchep-phhep-thJCAP(2024)·23 citations
25. 25*

    On thermal transition in QCD

    Masanori Hanada🇬🇧 · Hiromasa Watanabe🇯🇵

    We describe how the general mechanism of partial deconfinement applies to large-$N$ QCD and the partially-deconfined phase inevitably appears between completely-confined and completely-deconfined phases. Furthermore, we propose how the partial deconfinement can be observed in the real-world QCD with the SU(3) gauge group. For this purpose, we employ lattice configurations obtained by the WHOT-QCD collaboration and examine our proposal numerically. In the discussion, the Polyakov loop plays a crucial role in characterizing the phases, without relying on center symmetry, and hence, we clarify the meaning of the Polyakov loop in QCD at large $N$ and finite $N$. Both at large $N$ and finite $N$, the complete confinement is characterized by the Haar-random distribution of the Polyakov line phases. Haar-randomness, which is stronger than unbroken center symmetry, indicates that Polyakov loops in any nontrivial representations have vanishing expectation values and deviation from the Haar-random distribution at higher temperatures is quantified with the loops. We discuss that the transitions separating the partially-deconfined phase are characterized by the behaviors of Polyakov loops in various representations. The lattice QCD data provide us with the signals exhibiting two different characteristic temperatures: deconfinement of the fundamental representation and deconfinement of higher representations. As a nontrivial test for our proposal, we also investigate the relation between partial deconfinement and instanton condensation and confirm the consistency with the lattice data. To make the presentation more easily accessible, we provide a detailed review of the previously known aspects of partial deconfinement.

    ↳ hep-thhep-lathep-phnucl-thPTEP(2024)·21 citations
26. 26*

    Cosmological and idealized simulations of dark matter haloes with velocity-dependent, rare and frequent self-interactions

    Moritz S. Fischer🇩🇪 · Lenard Kasselmann🇩🇪 · Marcus Brüggen🇩🇪 · Klaus Dolag🇩🇪 · Felix Kahlhoefer🇩🇪 · Antonio Ragagnin🇮🇹 · Andrew Robertson🇺🇸 · Kai Schmidt-Hoberg🇩🇪

    Dark matter self-interactions may have the capability to solve or at least mitigate small-scale problems of the cosmological standard model, Lambda Cold Dark Matter. There are a variety of self-interacting dark matter models that lead to distinguishable astrophysical predictions and hence varying success in explaining observations. Studies of dark matter (DM) density cores on various mass scales suggest a velocity-dependent scattering cross-section. In this work, we investigate how a velocity dependence alters the evolution of the DM distribution for frequent DM scatterings and compare to the velocity-independent case. We demonstrate that these cases are qualitatively different using a test problem. Moreover, we study the evolution of the density profile of idealized DM haloes and find that a velocity dependence can lead to larger core sizes and different time-scales of core formation and core collapse. In cosmological simulations, we investigate the effect of velocity-dependent self-interaction on haloes and satellites in the mass range of $\approx 10^{11}-10^{14}$ M${}_{\odot }$. We study the abundance of satellites, density, and shape profiles and try to infer qualitative differences between velocity-dependent and velocity-independent scatterings as well as between frequent and rare self-interactions. We find that a strongly velocity-dependent cross-section can significantly amplify the diversity of rotation curves, independent of the angular dependence of the differential cross-section. We further find that the abundance of satellites in general depends on both the velocity dependence and the scattering angle, although the latter is less important for strongly velocity-dependent cross-sections.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2024)·44 citations
27. 27*

    Feature Learning and Generalization in Deep Networks with Orthogonal Weights

    Hannah Day🇺🇸 · Yonatan Kahn · Daniel A. Roberts🇺🇸

    Fully-connected deep neural networks with weights initialized from independent Gaussian distributions can be tuned to criticality, which prevents the exponential growth or decay of signals propagating through the network. However, such networks still exhibit fluctuations that grow linearly with the depth of the network, which may impair the training of networks with width comparable to depth. We show analytically that rectangular networks with tanh activations and weights initialized from the ensemble of orthogonal matrices have corresponding preactivation fluctuations which are independent of depth, to leading order in inverse width. Moreover, we demonstrate numerically that, at initialization, all correlators involving the neural tangent kernel (NTK) and its descendants at leading order in inverse width -- which govern the evolution of observables during training -- saturate at a depth of $\sim 20$, rather than growing without bound as in the case of Gaussian initializations. We speculate that this structure preserves finite-width feature learning while reducing overall noise, thus improving both generalization and training speed in deep networks with depth comparable to width. We provide some experimental justification by relating empirical measurements of the NTK to the superior performance of deep nonlinear orthogonal networks trained under full-batch gradient descent on the MNIST and CIFAR-10 classification tasks.

    ↳ cs.LGhep-phhep-thstat.MLMach.Learn.Sci.Tech.(2025)·4 citations
28. 28*

    Simulations of galaxy cluster mergers with velocity-dependent, rare and frequent self-interactions

    V. M. Sabarish · Marcus Brüggen🇩🇪 · Kai Schmidt-Hoberg🇩🇪 · Moritz S. Fischer🇩🇪 · Felix Kahlhoefer🇩🇪

    Self-interacting dark matter (SIDM) has been proposed to solve small-scale problems in $\Lambda$CDM cosmology. In previous work, constraints on the self-interaction cross-section of dark matter have been derived assuming that the self-interaction cross-section is independent of velocity. However, a velocity-dependent cross-section is more natural in most theories of SIDM. Using idealized $N$-body simulations without baryons, we study merging clusters with velocity-dependent SIDM. In addition to the usual rare scattering in the isotropic limit, we also simulate these systems with anisotropic, small-angle (frequent) scatterings. We find that the collision-less brightest cluster galaxy (BCG) has an offset from the DM peak that grows at later stages. Finally, we also extend the existing upper bounds on the velocity-independent, isotropic self-interaction cross-section to the parameter space of rare and frequent velocity-dependent self-interactions by studying the central densities of dark matter-only isolated haloes. For these upper-bound parameters, the DM-BCG offsets just after the first pericentre in the dark matter-only simulations are found to be $\le$ 10 kpc. On the other hand, because of BCG oscillations, we speculate that the distribution of BCG offsets in a relaxed cluster is a statistically viable probe. Therefore, this motivates further studies of BCG off-centring in hydrodynamic cosmological simulations.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2024)·19 citations
29. 29*

    Extreme mass-ratio inspirals as probes of fundamental dipoles

    Jacopo Lestingi🇮🇹 · Enrico Cannizzaro🇮🇹 · Paolo Pani🇮🇹

    Even if globally neutral, in various scenarios compact objects can have a nonvanishing dipole moment. Examples include neutron stars with magnetic dipoles, black-hole microstates in the string-theory fuzzball scenario, and classical black holes in modified theories of gravity with spin-induced scalarization or Lorentz-violating terms. A fundamental dipole moment would give rise to rich phenomenology, for example to intrinsic precession and extra emission channels in binary systems. We show that extreme mass-ratio inspirals (EMRIs) detectable by future gravitational-wave interferometers allow us to study a fundamental dipole on the secondary object in a model-agnostic fashion. By developing a general model for a fundamental scalar dipole, we compute the extra flux associated with it. This effect is suppressed by the square of the mass ratio relative to the case of fundamental charges, making its detection with EMRIs very challenging for the typical dipole moments predicted in various models. On the other hand, for the same reason the impact of an extra dipole for constraints on extra fundamental charges is likely negligible, making the latter constraints more robust.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2024)·13 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.