Fri·Jun 30, 2023Friday·June 30, 2023

1. 01*

   New Physics in CP Violating and Flavour Changing Quark Dipole Transitions

   Svjetlana Fajfer🇸🇮 · Jernej F. Kamenik🇸🇮 · Nejc Košnik🇸🇮 · Aleks Smolkovič🇨🇭 · Michele Tammaro🇸🇮

   We explore CP-violating (CPV) effects of heavy New Physics in flavour-changing quark dipole transitions, within the framework of Standard Model Effective Field Theory (SMEFT). First, we establish the relevant dimension six operators and consider the Renormalisation Group (RG) evolution of the appropriate Wilson coefficients. We investigate RG-induced correlations between different flavour-violating processes and electric dipole moments (EDMs) within the Minimal Flavour Violating and $U(2{)}^3$ quark flavour models. At low energies, we set bounds on the Wilson coefficients of the dipole operators using CPV induced contributions to observables in non-leptonic and radiative $B$, $D$ and $K$ decays as well as the neutron and electron EDMs. This enables us to connect observable CPV effects at low energies and general NP appearing at high scales. We present bounds on the Wilson coefficients of the relevant SMEFT operators at the high scale $\Lambda =5\mathrm{TeV}$, and discuss most sensitive CPV observables for future experimental searches.

   hep-phJHEP(2023)·10 citations
2. 02*

   Super-Nyquist ultralight dark matter searches with broadband atom gradiometers

   Leonardo Badurina🇬🇧 · Ankit Beniwal🇬🇧 · Christopher McCabe🇬🇧

   Atom gradiometers have emerged as compelling broadband probes of scalar ultralight dark matter (ULDM) candidates that oscillate with frequencies between approximately $10^{-2}$ Hz and $10^3$ Hz. ULDM signals with frequencies greater than $\sim 1$ Hz exceed the expected Nyquist frequency of atom gradiometers, and so are affected by aliasing and related phenomena, including signal folding and spectral distortion. To facilitate the discovery of super-Nyquist ULDM signals, in this work we investigate the impact of these effects on parameter reconstruction using a robust likelihood-based framework. We demonstrate that accurate reconstruction of ULDM parameters can be achieved as long as the experimental frequency resolution is larger than the ULDM signal linewidth. Notably, as ULDM candidates whose frequencies differ by integer multiples of the sampling frequency are identified at the same aliased frequency, our discovery analysis recovers discrete islands in parameter space. Our study represents the first comprehensive exploration of aliasing in the context of dark matter direct detection and paves the way for enhanced ULDM detection strategies with atom gradiometers.

   hep-phastro-ph.COphysics.atom-phPRD(2023)·20 citations
3. 03*

   The Dark Dimension and the Standard Model Landscape

   Luis A. Anchordoqui🇺🇸 · Ignatios Antoniadis🇫🇷 · Jules Cunat🇫🇷

   We study the landscape of lower-dimensional vacua of the SM coupled to gravity in the presence of the ``dark dimension'' of size $R_{\perp }$ in the micron range, focusing on the validity of the swampland conjecture forbidding the presence of non-SUSY AdS vacua in a consistent quantum gravity theory. We first adopt the working assumption that right-handed neutrinos propagate in the bulk, so that neutrino Yukawa couplings become tiny due to a volume suppression, leading to naturally light Dirac neutrinos. We show that the neutrino KK towers compensate for the graviton tower to maintain stable dS vacua found in the past, but neutrino oscillation data set restrictive bounds on $R_{\perp }$ and therefore the first KK neutrino mode is too heavy to alter the shape of the radon potential or the required maximum mass for the lightest neutrino to carry dS rather than AdS vacua found in the absence of the dark dimension, $m_{1,\max }\lesssim 7.63\mathrm{meV}$. We also show that a very light gravitino (with mass in the meV range) could help relax the neutrino mass constraint $m_{1,\max }\lesssim 50\mathrm{meV}$. The differences for the predicted total neutrino mass $\sum m_{\nu }$ among these two scenarios are within reach of next-generation cosmological probes that may measure the total neutrino mass with an uncertainty $\sigma (\sum m_{\nu })=0.014\mathrm{eV}$. We also demonstrate that the KK tower of a very light gravitino can compensate for the graviton tower to sustain stable dS vacua and thus right-handed neutrinos can (in principle) be locked on the brane. For this scenario, Majorana neutrinos could develop dS vacua, which is not possible in the SM coupled to gravity. Finally, we investigate the effects of bulk neutrino masses in suppressing oscillations of the 0-modes into the first KK modes to relax the oscillation bound on $R_{\perp }$.

   hep-phhep-thPRD(2024)·32 citations
4. 04*

   New energy spectra in neutrino and photon detectors to reveal hidden dark matter signals

   Wim Beenakker🇳🇱 · Sascha Caron🇳🇱 · Jochem Kip🇳🇱 · Roberto Ruiz de Austri🇪🇸 · Zhongyi Zhang🇳🇱

   Neutral particles capable of travelling cosmic distances from a source to detectors on Earth are limited to photons and neutrinos. Examination of the Dark Matter annihilation/decay spectra for these particles reveals the presence of continuum spectra (e.g. due to fragmentation and W or Z decay) and peaks (due to direct annihilations/decays). However, when one explores extensions of the Standard Model (BSM), unexplored spectra emerge that differ significantly from those of the Standard Model (SM) for both neutrinos and photons. In this paper, we argue for the inclusion of important spectra that include peaks as well as previously largely unexplored entities such as boxes and combinations of box, peak and continuum decay spectra.

   hep-phJHEP(2023)·1 citation
5. 05*

   Recent 3-Loop Heavy Flavor Corrections to Deep-Inelastic Scattering

   J. Ablinger🇦🇹 · A. Behring🇨🇭 · J.Blümlein · A. De Freitas🇦🇹 · A. Goedicke🇩🇪 · A. von Manteuffel🇩🇪 · C. Schneider🇦🇹 · K. Schönwald🇨🇭

   We report on recent progress in calculating the three loop QCD corrections of the heavy flavor contributions in deep--inelastic scattering and the massive operator matrix elements of the variable flavor number scheme. Notably we deal with the operator matrix elements $A_{gg,Q}^{(3)}$ and $A_{Qg}^{(3)}$ and technical steps to their calculation. In particular, a new method to obtain the inverse Mellin transform without computing the corresponding $N$--space expressions is discussed.

   hep-phhep-exPoS(2024)·1 citation
6. 06*

   Stability of Electroweak Vacuum and Supersymmetric Contribution to Muon g-2

   So Chigusa🇺🇸 · Takeo Moroi🇯🇵 · Yutaro Shoji🇮🇱

   We study the stability of the electroweak vacuum in the supersymmetric (SUSY) standard model (SM), paying particular attention to its relation to the SUSY contribution to the muon anomalous magnetic moment $a_{\mu }$. If the SUSY contribution to $a_{\mu }$ is sizable, the electroweak vacuum may become unstable because of enhanced trilinear scalar interactions in particular when the sleptons are heavy. Consequently, assuming enhanced SUSY contribution to $a_{\mu }$, an upper bound on the slepton masses is obtained. We give a detailed prescription to perform a full one-loop calculation of the decay rate of the electroweak vacuum for the case that the SUSY contribution to $a_{\mu }$ is enhanced. We also give an upper bound on the slepton masses as a function of the SUSY contribution to $a_{\mu }$.

   hep-phJHEP(2023)·4 citations
7. 07*

   Parametric study of the polarization dependence of nonlinear Breit-Wheeler pair creation process using two laser pulses

   Qian Qian🇺🇸 · Daniel Seipt🇩🇪 · Marija Vranic🇵🇹 · Thomas E. Grismayer🇵🇹 · Tom G. Blackburn🇸🇪 · Christopher P. Ridgers🇬🇧 · Alexander G. R. Thomas🇺🇸

   With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser-plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong-field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate the electron beam through quantum radiation reaction. The second pulse is optimized to generate electron-positron pairs by nonlinear Breit-Wheeler decay of the photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates.

   hep-phphysics.plasm-phPhys.Plasmas(2023)·12 citations
8. 08*

   Theoretical Corrections of $R_D$ and $R_{D^{\ast }}$

   Xin-Xin Long🇨🇳 · Shu-Min Zhao🇨🇳 · Ming-Yue Liu🇨🇳 · Xi Wang🇨🇳 · Yi-Tong Wang🇨🇳 · Zhong-Jun Yang🇨🇳 · Xing-Xing Dong🇨🇳 · Tai-Fu Feng🇨🇳

   $R_{D^{(\ast )}}$ is the ratio of branching ratio $\overline{B}\to D^{(\ast )}\tau {\overline{\nu }}_{\tau }$ to $\overline{B}\to D^{(\ast )}l{\overline{\nu }}_l(l=e,\mu )$. There is a gap of 2${\sigma }_{exp}$ or more between its experimental value and the prediction under the standard model(SM). People extend the MSSM with the local gauge group $U(1{)}_X$ to obtain the $U(1{)}_X$SSM. Compared with MSSM, $U(1{)}_X$SSM has more superfields and effects. In $U(1{)}_X$SSM, we research the semileptonic decays $\overline{B}\to D^{(\ast )}l{\overline{\nu }}_l$ and calculate $R_{D^{(\ast )}}$. The numerical results of $R_{D^{(\ast )}}$ are further corrected under $U(1{)}_X$SSM, which are much better than the SM predictions. After correction, the theoretical value of $R_{D^{(\ast )}}$ can reach one ${\sigma }_{exp}$ range of the averaged experiment central value.

   hep-phEPJC(2023)·1 citation
9. 09*

   Total cross section of the process $e^{+}+e^{-}\to {\Sigma }^0+{\bar{\Sigma }}^0$ in the vicinity of charmonium $\psi (3770)$ including the $D$-meson loop and three gluon contributions

   Azad I. Ahmadov🇦🇿

   For the study of the structure of baryons it is necessary to investigate the production of a baryon pair in $e^{+}{e}^{-}$ annihilation. The baryon-antibaryon pair production at the electron-positron linear collider makes it possible to investigate in detail the basic structure of the Standard Model. The creation of baryon-antibaryon pairs in electron-positron annihilation provides an increasingly powerful tool at higher c.m. energies. We present phenomenological results for ${\Sigma }^0{\bar{\Sigma }}^0$ production in $e^{+}{e}^{-}$ interaction at the BESIII and BABAR Colliders. In the present work, we investigate a hyperon pair produced in the reaction $e^{+}{e}^{-}\to {\Sigma }^0{\bar{\Sigma }}^0$. We calculate the total cross section of the process $e^{+}{e}^{-}\to {\Sigma }^0{\bar{\Sigma }}^0$ taking into account the contributions of the $D$-meson loop and three gluon loops as well as the interference of all diagrams to the Born approximation. For these contributions large relative phases are generated with respect to the pure electromagnetic mechanism. For the large momentum transferred region we obtain as a byproduct a fit of the electromagnetic form factor of the $\Sigma$ hyperon.

   hep-phPRD(2024)·2 citations
10. 10*

    Data-driven determination of the light-quark connected component of the intermediate-window contribution to the muon $g-2$

    Genessa Benton🇺🇸 · Diogo Boito🇧🇷 · Maarten Golterman🇺🇸 · Alexander Keshavarzi🇬🇧 · Kim Maltman🇦🇺 · Santiago Peris🇪🇸

    We present the first data-driven result for $a_{\mu }^{\mathrm{win},\mathrm{lqc}}$, the isospin-limit light-quark connected component of the intermediate-window Hadronic-Vacuum-Polarization contribution to the muon anomalous magnetic moment. Our result, $(198.8\pm 1.1)\times 10^{-10}$, is in significant tension with eight recent mutually compatible high-precision lattice-QCD determinations, and provides enhanced evidence for a puzzling discrepancy between lattice and data-driven determinations of the intermediate window quantity, one driven largely by a difference in the light-quark connected component.

    hep-phhep-latPRL(2023)·35 citations
11. 11*

    Self-interacting dark matter implied by nano-Hertz gravitational waves

    Chengcheng Han🇨🇳 · Ke-Pan Xie🇨🇳 · Jin Min Yang🇨🇳 · Mengchao Zhang🇨🇳

    The self-interacting dark matter (SIDM) paradigm offers a potential solution to the small-scale structure problems faced by collision-less cold dark matter. This framework incorporates self-interactions among dark matter particles, typically mediated by a particle with a MeV-scale mass. Recent evidences of nano-Hertz gravitational waves from pulsar timing arrays (PTAs) such as NANOGrav, CPTA, EPTA, and PPTA suggest the occurrence of a first-order phase transition (FOPT) at a MeV-scale temperature. Considering the close proximity between these two scales, we propose that the mediator mass in the SIDM model originates from the spontaneous breaking of a $U(1{)}^{\prime }$ symmetry, which is driven by the FOPT indicated by PTA data. Consequently, the alignment of these two scales is believed to be deeply connected by the same underlying physics. By extensively exploring the parameter space, remarkably, we find that the parameter space favored by SIDM just provides an explanation for the PTA data.

    hep-phastro-ph.COPRD(2024)·105 citations
12. 12*

    Associated production of a top-quark pair with two isolated photons at the LHC through NLO in QCD

    Daniel Stremmer🇩🇪 · Malgorzata Worek🇩🇪

    We report on the computation of NLO QCD corrections to top-quark pair production in association with two photons at the LHC. Higher-order effects and photon bremsstrahlung are taken into account in the production and decays of the top-quark pair. Top-quark and $W$-boson decays are treated in the Narrow Width Approximation conserving spin correlations up to NLO in QCD. This is the first time that the complete set of NLO QCD corrections to the $pp\to t\bar{t}\gamma \gamma$ process including top-quark decays is calculated. We present results at the integrated and differential cross-section level in the di-lepton and lepton $+$ jet channel. In addition, we investigate the effect of photon bremsstrahlung in $t\bar{t}$ production and top-quark decays, as well as the mixed contribution. The latter contribution, in which two photons occur simultaneously in the production and decay of the $t\bar{t}$ pair, proved to be significant at both the integrated and differential cross-section level.

    hep-phhep-exJHEP(2023)·13 citations
13. 13*

    On the hypothesis of a second Higgs boson near 0.5 TeV

    S.S. Afonin🇷🇺

    Recently, a second Higgs-like boson $h^{\prime }$ with the mass near 0.5~TeV was predicted from a dual holographic model describing the hypothetical strongly-coupled sector beyond the Standard Model. We analyze under what conditions this prediction can be reproduced within the framework of more traditional models for describing a strongly-coupled field theory -- the spectral sum rules and the Nambu--Jona-Lasinio model in the scalar channel. It is shown that the results of both approaches are close and lead to this prediction if the covariant four-momentum cutoff in them is identified with the unitarity bound on the Higgs boson mass, and also under the assumption that the strongly coupled sector beyond the Standard Model is described by some quantum field theory based on the $SU(2)$ gauge group. We also present additional arguments suggesting that a mass of about 0.5 TeV would be natural for a heavy analogue of the Higgs boson, if it exists.

    hep-phTheor.Math.Phys.(2026)·0 citations
14. 14*

    Conformal Symmetry and Effective Potential: II. Evolution

    I.V. Anikin🇷🇺

    We present the second part of a paper series devoted to the study of the multi-loop effective potential evolution in ${\phi }^4$-theory using the conformal symmetry. In this paper, we demonstrate that the conformal symmetry can still be useful for the effective potential approach even at the presence of the mass parameter. To this goal, it is necessary to introduce the special treatment of the mass terms as sorts of interaction in an asymptotical expansion of the generating functional. The introduced vacuum $V_{z,x}$-operation is the main tool to the algebraic scheme of anomalous dimension calculations. It is shown that the vacuum $V_{z,x}$-operation transforms the given Green functions to the corresponding vacuum integrations which generate the effective potential.

    hep-phhep-thEPJA(2023)·2 citations
15. 15*

    Footprints of Axion-Like Particle in Pulsar Timing Array Data and James Webb Space Telescope Observations

    Shu-Yuan Guo🇨🇳 · Maxim Khlopov🇷🇺 · Xuewen Liu🇨🇳 · Lei Wu🇨🇳 · Yongcheng Wu🇨🇳 · Bin Zhu🇨🇳

    Several Pulsar Timing Array (PTA) collaborations have recently reported the evidence for a stochastic gravitational-wave background (SGWB), which can unveil the formation of primordial seeds of inhomogeneities in the early universe. With the SGWB parameters inferred from PTAs data, we can make a prediction of the seeds for early galaxy formation from the domain walls in the axion-like particles (ALPs) field distribution. This also naturally provides a solution to the observation of high redshifts by the James Webb Space Telescope. The predicted photon coupling of the ALP is within the reach of future experimental searches.

    hep-phastro-ph.COastro-ph.GASCPMA(2024)·131 citations
16. 16*

    Self-Interacting Forbidden Dark Matter under a Cannibally Co-Decaying Phase

    Kwei-Chou Yang🇹🇼

    In a usual dark matter (DM) model without a huge mass difference between the DM and lighter mediator, using the coupling strength suitable for having the correct relic density, the resulting self-interaction becomes several orders of magnitude smaller than that required to interpret the small scale structures. We present a framework that can offer a solution for this point. We consider a model that contains the vector DM and a heavier but unstable Higgs-like scalar in the hidden sector. When the temperature drops below $\sim m_{\mathrm{DM}}$, the hidden sector, which is thermally decoupled from the visible sector, enters a cannibal phase, during which the DM density is depleted with the out-of-equilibrium decay of the scalar. The favored parameter region, giving the correct relic density and the proper size of self-interactions, shows the scalar-to-DM mass ratio $\in [1.1,1.33]$ and the scalar mass $\in [9,114]\mathrm{MeV}$. A sizable parameter space still survives the most current constraints and can be further probed by the near future NA62 beam dump experiment.

    hep-phastro-ph.COastro-ph.HEhep-exJHEP(2024)·2 citations
17. 17*

    Cross section for supernova axion observation in neutrino water Cherenkov detectors

    Pierluca Carenza🇸🇪 · Giampaolo Co'🇮🇹 · Maurizio Giannotti🇺🇸 · Alessandro Lella🇮🇹 · Giuseppe Lucente🇮🇹 · Alessandro Mirizzi🇮🇹 · Thomas Rauscher🇨🇭

    Axions coupled to nucleons might be copiously emitted from core-collapse supernovae (SNe). If the axion-nucleon coupling is strong enough, axions would be emitted from the SN as a burst and, reaching Earth, may excite the oxygen nuclei in water Cherenkov detectors (${}^{16}\mathrm{O}+a\to {}^{16}{\mathrm{O}}^{\ast }$). This process will be followed by decay(s) of the excited state resulting in an emission of photons and thus providing a possibility for a direct detection of axions from a Galactic SN in large underground neutrino Cherenkov detectors. Motivated by this possibility, we present an updated calculation of axion-oxygen cross section obtained by using self-consistent continuum Random Phase Approximation. We calculate the branching ratio of the oxygen nucleus de-excitation into gamma-rays, neutrons, protons and $\alpha$-particles and also consider photon emission from secondary nuclei to compute a total $\gamma$ spectrum created when axions excite ${}^{16}\mathrm{O}$. These results are used to revisit the detectability of axions from SN 1987A in Kamiokande-II.

    hep-phastro-ph.HEnucl-thPRC(2024)·25 citations
18. 18*

    Pulsar Timing Array Stochastic Background from light Kaluza-Klein resonances

    Eugenio Megias🇪🇸 · Germano Nardini🇳🇴 · Mariano Quiros🇪🇸

    We investigate the potential of the warped-extradimension framework as an explanation for the recently observed stochastic gravitational background at nHz frequencies in pulsar timing arrays (PTA). Our analysis reveals that the PTA data can be effectively accommodated by a first-order phase transition triggered by a radion at the MeV-GeV scale feebly coupled to the Standard Model. Remarkably, this outcome remains robust irrespective of the specific details of the warped extradimension embedding, providing a foundation for future investigations aiming to develop concrete extradimension descriptions of Nature. We also demonstrate that many existing embeddings are not viable, as their radion and graviton phenomenology clash with a MeV-GeV scale radion. As a possible way-out, we sketch a promising solution involving multiple branes, wherein the light radion, graviton, and ensuing light resonances remain consistent with collider bounds and gravity tests.

    hep-phastro-ph.HEgr-qcPRD(2023)·61 citations
19. 19*

    NANOGrav Signal from a Dark Conformal Phase Transition

    Kohei Fujikura🇯🇵 · Sudhakantha Girmohanta🇨🇳 · Yuichiro Nakai🇨🇳 · Motoo Suzuki🇺🇸

    We explore the possibility that a confining first-order phase transition of a nearly-conformal dark sector generates the reported NANOGrav signal of a stochastic gravitational wave background. The visible Standard Model (SM) sector and the dark sector are initially thermally decoupled so that their temperatures are different. The nearly conformal phase transition is described by the shallow potential of a dilaton (or a radion in the 5D holographic perspective) generated by a new dark Yang-Mills field coupled to the conformal sector. For a dark sector only gravitationally connected with the visible sector, the NANOGrav signal is explained by the phase transition without contradicting the $\Delta N_{\mathrm{eff}}$ constraint, together with a contribution from supermassive black hole binaries. While the dilaton and dark glueballs can be produced after the phase transition, they immediately decay into dark radiation, which can help ameliorate the Hubble tension and be tested by the future CMB-S4 experiment. Alternatively, for a dark conformal sector decaying into the visible sector after the phase transition, the $\Delta N_{\mathrm{eff}}$ constraint is not applied and the phase transition can solely explain the NANOGrav signal.

    hep-phastro-ph.COhep-thPLB(2023)·102 citations
20. 20*

    Implication of nano-Hertz stochastic gravitational wave background on ultralight axion particles

    Jing Yang🇨🇳 · Ning Xie🇨🇳 · Fa Peng Huang🇨🇳

    Recently, the Hellings Downs correlation has been observed by different pulsar timing array (PTA) collaborations, such as NANOGrav, European PTA, Parkes PTA, and Chinese PTA. These PTA measurements of the most precise pulsars within the Milky Way show the first evidence for the stochastic gravitational wave background of our Universe. We study the ultralight axion interpretation of the new discovery by investigating the gravitational wave from axion transitions between different energy levels of the gravitational atoms, which are composed of cosmic populated Kerr black holes and their surrounding axion clouds formed through the superradiant process. By Bayesian analysis, we demonstrate that this new observation naturally admits an ultralight axion interpretation around $10^{-21}$eV, which is consistent in magnitude with the typical mass of fuzzy dark matter.

    hep-phastro-ph.HEJCAP(2024)·54 citations
21. 21*

    Why quarkonium hybrid coupling to two S-wave heavy-light mesons is not suppressed

    R. Bruschini🇺🇸

    We examine the couplings of quarkonium hybrids to heavy-light meson pairs in the Born-Oppenheimer approximation for QCD. The lowest hybrid multiplets consist of bound states of the ${\Pi }_u$ and ${\Sigma }_u^{-}$ potentials. We find that the ${\Sigma }_u^{-}$ potential can couple to pairs of $S$-wave mesons through string breaking, while the ${\Pi }_u$ potential cannot. From this observation, we derive model-independent selection rules that contradict previous expectations that quarkonium hybrids are forbidden to decay into pairs of $S$-wave mesons. These Born-Oppenheimer selection rules are consistent with the partial decay widths of the lowest charmonium hybrid with exotic quantum numbers $J^{PC}=1^{-+}$ recently calculated in lattice QCD.

    hep-phPRD(2024)·17 citations
22. 22*

    Gravitational Waves from Domain Wall Collapse, and Application to Nanohertz Signals with QCD-coupled Axions

    Naoya Kitajima🇯🇵 · Junseok Lee🇯🇵 · Kai Murai🇯🇵 · Fuminobu Takahashi🇯🇵 · Wen Yin🇯🇵

    We study for the first time the gravitational waves generated during the collapse of domain walls, incorporating the potential bias in the lattice simulations. The final stages of domain wall collapse are crucial for the production of gravitational waves, but have remained unexplored due to computational difficulties. As a significant application of this new result, we show that the observed NANOGrav, EPTA, PPTA, and CPTA data, which indicate stochastic gravitational waves in the nanohertz regime, can be attributed to axion domain walls coupled to QCD. In our model, non-perturbative effects of QCD induce a temperature-dependent bias around the QCD crossover, inducing the rapid collapse of the domain walls. We use sophisticated lattice simulations that account for the temperature-dependent bias to measure the gravitational waves resulting from the domain wall annihilation. We also discuss the future prospects for accelerator-based searches for the axion and the potential for the formation and detection of primordial black holes.

    hep-phastro-ph.COPLB(2024)·183 citations
23. 23*

    QCD-Collapsed Domain Walls: QCD Phase Transition and Gravitational Wave Spectroscopy

    Yang Bai🇺🇸 · Ting-Kuo Chen🇺🇸 · Mrunal Korwar🇺🇸

    For a discrete symmetry that is anomalous under QCD, the domain walls produced in the early universe from its spontaneous breaking can naturally annihilate due to QCD instanton effects. The gravitational waves generated from wall annihilation have their amplitude and frequency determined by both the discrete symmetry breaking scale and the QCD scale. The evidence of stochastic gravitational waves at nanohertz observed by pulsar timing array experiments suggests that the discrete-symmetry-breaking scale is around 100 TeV, assuming the domain-wall explanation. The annihilation temperature is about 100 MeV, which could naturally be below the QCD phase transition temperature. We point out that the QCD phase transition within some domains with an effective large QCD $\theta$ angle could be a first-order one. To derive the phase diagram in $\theta$ and temperature, we adopt a phenomenological linear sigma model with three quark flavors. The domain-wall explanation for the NANOGrav, EPTA, PPTA and CPTA results hints at a first-order QCD phase transition, which predicts additional gravitational waves at higher frequencies. If the initial formation of domain walls is also a first-order process, this class of domain-wall models predicts an interesting gravitational wave spectroscopy with frequencies spanning more than ten orders of magnitude, from nanohertz to 100 Hz.

    hep-phastro-ph.COJHEP(2023)·93 citations
24. 24*

    Growing Excesses of New Scalars at the Electroweak Scale

    Srimoy Bhattacharya🇿🇦 · Guglielmo Coloretti🇨🇭 · Andreas Crivellin🇨🇭 · Salah-Eddine Dahbi🇿🇦 · Yaquan Fang🇨🇳 · Mukesh Kumar🇿🇦 · Bruce Mellado🇿🇦

    We combine searches for scalar resonances at the electroweak scale performed by the Large Hadron Collider experiments ATLAS and CMS where persisted excesses have been observed in recent years. Using both the side-bands of Standard Model Higgs analyses as well as dedicated beyond the Standard Model analyses, we find significant hints for new scalars at $\approx 95$GeV ($S^{\prime }$) and $\approx 152$GeV ($S$). The presence of a $95$GeV scalar is preferred over the Standard Model hypothesis by $3.8\sigma$, while interpreting the $152$GeV excesses in a simplified model with resonant pair production of $S$ via a new heavier scalar $H(270)$, a global significance of $\approx 5\sigma$ is obtained. While the production mechanism of the $S^{\prime }$ cannot yet be determined, data strongly favours the associated production of $S$, i.e. via the decay of a heavier boson $H$ ($pp\to H\to S{S}^{\ast }$). A possible alternative or complementary decay chain is $H\to S{S}^{\prime }$, where $S\to W{W}^{\ast }$ ($S^{\prime }$) would be the source of the leptons ($b$-quarks) necessary to explain the multi-lepton anomalies found in Large Hadron Collider data.

    hep-phhep-ex59 citations
25. 25*

    The gravitational eikonal: from particle, string and brane collisions to black-hole encounters

    Paolo Di Vecchia🇩🇰 · Carlo Heissenberg🇸🇪 · Rodolfo Russo🇬🇧 · Gabriele Veneziano🇨🇭

    Motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal approach, inspired by its electromagnetic predecessor, has been successfully applied to the transplanckian energy collisions of elementary particles and strings since the late eighties, and to string-brane collisions in the past decade. After the direct detection of gravitational waves from black-hole mergers, most of the attention has shifted towards adapting these methods to the physics of black-hole encounters. For such systems, the eikonal exponentiation provides an amplitude-based approach to calculate classical gravitational observables, thus complementing more traditional analytic methods such as the Post-Newtonian expansion, the worldline formalism, or the Effective-One-Body approach. In this review we summarize the main ideas and techniques behind the gravitational eikonal formalism. We discuss how it can be applied in various different physical setups involving particles, strings and branes and then we mainly concentrate on the most recent developments, focusing on massive scalars minimally coupled to gravity, for which we aim at being as self-contained and comprehensive as possible.

    ↳ hep-thgr-qchep-phPhys.Rept.(2024)·158 citations
26. 26*

    Fate of chiral symmetry in Riemann-Cartan geometry

    Gustavo P. de Brito🇩🇰 · Antonio D. Pereira🇧🇷 · Arthur F. Vieira🇩🇰

    We study the mechanism of chiral symmetry breaking for fermionic systems in a gravitational background with curvature and torsion. The analysis is based on a scale-dependent effective potential derived from a bosonized version of the Nambu-Jona-Lasino model in a Riemann-Cartan background. We have investigated the fate of chiral symmetry in two different regimes. First, to gain some intuition on the combined effect of curvature and torsion, we investigate the regime of weak curvature and torsion. However, this regime does not access the deep infrared limit, which is essential to answer questions related to the mechanism of gravitational catalysis in fermionic systems. Second, we look at the regime of vanishing curvature and homogeneous torsion. In this case, although we cannot probe the combined effects of curvature and torsion, we can access the deep infrared contributions of the background torsion to the mechanism of chiral symmetry breaking. Our main finding is that, in the scenario where only torsion is present, there is no indication of a mechanism of gravitational catalysis.

    ↳ hep-thgr-qchep-phPRD(2023)·2 citations
27. 27*

    Exploring resonantly produced mixed sterile neutrino dark matter models

    Emma L. Horner🇺🇸 · Francisco Mungia Wulftange🇺🇸 · Isabella A. Ianora🇺🇸 · Chad T. Kishimoto🇺🇸

    An unidentified 3.55 keV X-ray line in stacked spectra of galaxies and clusters raises the interesting possibility that it originates from the decay of sterile neutrino dark matter. In this work, we explore mixed sterile neutrino dark matter models that combine cold dark matter and warmer sterile neutrino dark matter produced through lepton number-driven active-to-sterile neutrino transformation. We analyze the sensitivity of the sterile neutrino spectra on active-sterile mixing and on initial neutrino lepton numbers. Furthermore, we assess the viability of these models with estimates of the number of subhalos formed as the host sites of satellite galaxies.

    ↳ astro-ph.COhep-phPRD(2023)·6 citations
28. 28*

    Relativistic Hydrostatic Structure Equations and Analytic Multilayer Stellar Model

    Shuichi Yokoyama🇯🇵

    The relativistic extension of the classic stellar structure equations is investigated. It is pointed out that the Tolman-Oppenheimer-Volkov (TOV) equation with the gradient equation for local gravitational mass can be made complete as a closed set of differential equations by adding that for the Tolman temperature with one equation of state, and the set is proposed as the relativistic hydrostatic structure equations. The exact forms of the relativistic Poisson equation and the steady-state heat conduction equation in the curved spacetime are derived. The application to an ideal gas of particles with the conserved particle number current leads to a strong prediction that the heat capacity ratio almost becomes one in any Newtonian convection zone such as the solar surface. The steady-state heat conduction equation is solved exactly in the system and thermodynamic observables exhibit the power law behavior, which implies the possibility for the system to be a new model of stellar corona and a flaw in the earlier one obtained by using the non-relativistic stellar structure equations. The mixture with another ideal gas yields multilayer structure to a stellar model, in which classic stellar structure equations are reproduced and analytic multilayer structure of luminous stars including the Sun is revealed in suitable approximation.

    ↳ gr-qcastro-ph.HEastro-ph.SRhep-ph+11 citation
29. 29*

    Mirror QCD phase transition as the origin of the nanohertz Stochastic Gravitational-Wave Background

    Lei Zu🇨🇳 · Chi Zhang🇨🇳 · Yao-Yu Li🇨🇳 · Yu-Chao Gu🇨🇳 · Yue-Lin Sming Tsai🇨🇳 · Yi-Zhong Fan🇨🇳

    Several Pulsar Timing Array (PTA) collaborations have recently provided strong evidence for a nHz Stochastic Gravitational-Wave Background (SGWB). Here we investigate the implications of a first-order phase transition occurring within the early universe's dark quantum chromodynamics (dQCD) epoch, specifically within the framework of the mirror twin Higgs dark sector model. Our analysis indicates a distinguishable SGWB signal originating from this phase transition, which can explain the measurements obtained by PTAs. Remarkably, a significant portion of the parameter space for the SGWB signal also effectively resolves the existing tensions in both the $H_0$ and $S_8$ measurements in Cosmology. This intriguing correlation suggests a possible common origin of these three phenomena for $0.2<\Delta N_{\mathrm{eff}}<0.5$, where the mirror dark matter component constitutes about $30\%$ of the total dark matter abundance. Next generation CMB experiment such as CMB-S4 is able to test this parameter region.

    ↳ astro-ph.HEastro-ph.COhep-phSci.Bull.(2024)·75 citations
30. 30*

    String Model Building on Quantum Annealers

    Steven A. Abel🇬🇧 · Luca A. Nutricati🇬🇧 · John Rizos🇬🇷

    We explore for the first time the direct construction of string models on quantum annealers, and investigate their efficiency and effectiveness in the model discovery process. Through a thorough comparison with traditional methods such as simulated annealing, random scans, and genetic algorithms, we highlight the potential advantages offered by quantum annealers, which in this study promised to be roughly fifty times faster than random scans and genetic algorithm and approximately four times faster than simulated annealing.

    ↳ hep-thhep-phquant-phFortsch.Phys.(2023)·4 citations
31. 31*

    Off-shell form factor in N=4 sYM at three loops

    A.V.Belitsky🇺🇸 · L.V.Bork🇷🇺 · V.A.Smirnov🇷🇺

    In this paper we provide a detailed account of our calculation, briefly reported in arXiv:2209.09263, of a two-particle form factor of the lowest components of the stress-tensor multiplet in N=4 sYM theory on its Coulomb branch, which is interpreted as an off-shell kinematical regime. We demonstrate that up to three-loop order, both its infrared-divergent as well as finite parts do exponentiate in the Sudakov regime, with the coefficient accompanying the double logarithm being determined by the octagon anomalous dimension ${\Gamma }_{\mathrm{oct}}$. We also observe that up to this order in 't Hooft coupling the logarithm of the Sudakov form factor is identical to twice the logarithm of the null octagon, which was introduced within the context of integrability-based computation of four point correlators with infinitely large R-charges. The null octagon is known in a closed form for all values of the 't Hooft coupling constant and kinematical parameters. We conjecture that the relation between the former and the off-shell Sudakov form factor holds to all loop orders.

    ↳ hep-thhep-phJHEP(2023)·18 citations
32. 32*

    D-term Uplifts in Non-Supersymmetric Heterotic String Models

    Alonzo R. Diaz Avalos🇬🇧 · Alon E. Faraggi🇬🇧 · Viktor G. Matyas🇬🇧 · Benjamin Percival🇬🇧

    Recently, we proposed that the one-loop tadpole diagram in perturbative non-supersymmetric heterotic string vacua that contain an anomalous $U(1)$ symmetry, leads to an analog of the Fayet-Iliopoulos $D$-term in $\mathcal{N}=1$ supersymmetric models, and may uplift the vacuum energy from negative to positive value. In this paper, we extend this analysis to new types of vacua, including those with Stringy Scherk-Schwarz (SSS) spontaneous supersymmetry breaking versus those with explicit breaking. We develop a criteria that facilitates the extraction of vacua with Scherk-Schwarz breaking. We develop systematic tools to analyse the T-duality property of some of the vacua and demonstrate them in several examples. The extraction of the anomalous $U(1)$ $D$-terms is obtained in two ways. The first utilises the calculation of the $U(1)$-charges from the partition function, whereas the second utilises the free fermionic classification methodology to classify large spaces of vacua and analyse the properties of the massless spectrum. The systematic classification method also ensures that the models are free from physical tachyons. We provide a systematic tool to relate the free fermionic basis vectors and one-loop Generalised GSO phases that define the string models, to the one-loop partition function in the orbifold representation. We argue that a $D$-term uplift, while rare, is possible for both the SSS class of models, as well as in those with explicit breaking. We discuss the steps needed to further develop the arguments presented here.

    ↳ hep-thhep-phPRD(2023)·17 citations
33. 33*

    Stochastic gravitational wave background from early dark energy

    Naoya Kitajima🇯🇵 · Tomo Takahashi🇯🇵

    We study the production of stochastic gravitational wave background from early dark energy (EDE) model. It is caused by resonant amplification of scalar field fluctuations, which easily takes place for typical EDE potential based on the string axion or $\alpha$-attractor model. The resultant spectrum of gravitational wave background is computed by performing 3D lattice simulations. We show that, specifically in some class of generalized $\alpha$-attractor EDE model, a significant amount of gravitational waves can be produced via tachyonic instability with a peak around femto-Hz frequency range. Models predicting such gravitational waves can be constrained by the cosmic microwave background observations.

    ↳ astro-ph.COgr-qchep-phJCAP(2023)·5 citations
34. 34*

    Inflationary interpretation of the stochastic gravitational wave background signal detected by pulsar timing array experiments

    Sunny Vagnozzi🇮🇹

    Various pulsar timing array (PTA) experiments (NANOGrav, EPTA, PPTA, CPTA, including data from InPTA) very recently reported evidence for excess red common-spectrum signals in their latest datasets, with inter-pulsar correlations following the Hellings-Downs pattern, pointing to a stochastic gravitational wave background (SGWB) origin. Focusing for concreteness on the NANOGrav signal (given that all signals are in good agreement between each other), I inspect whether it supports an inflationary SGWB explanation, finding that such an interpretation calls for an extremely blue tensor spectrum, with spectral index $n_T\simeq 1.8\pm 0.3$, while Big Bang Nucleosynthesis limits require a very low reheating scale, $T_{\mathrm{rh}}\lesssim 10\mathrm{GeV}$. While not impossible, an inflationary origin for the PTA signal is barely tenable: within well-motivated inflationary models it is hard to achieve such a blue tilt, whereas models who do tend to predict sizeable non-Gaussianities, excluded by observations. Intriguingly, ekpyrotic models naturally predict a SGWB with spectral index $n_T=2$, although with an amplitude too suppressed to be able to explain the signal detected by PTA experiments. Finally, I provide explicit expressions for a bivariate Gaussian approximation to the joint posterior distribution for the intrinsic-noise amplitude and spectral index of the NANOGrav signal, which can facilitate extending similar analyses to different theoretical signals.

    ↳ astro-ph.COgr-qchep-phhep-thJHEAp(2023)·254 citations
35. 35*

    Astrophysical neutrino oscillations after pulsar timing array analyses

    Gaetano Lambiase🇮🇹 · Leonardo Mastrototaro🇮🇹 · Luca Visinelli🇨🇳

    The pattern of neutrino flavor oscillations could be altered by the influence of noisy perturbations such as those arising from a gravitational wave background (GWB). A stochastic process that is consistent with a GWB has been recently reported by the independent analyses of pulsar timing array (PTA) data sets collected over a decadal timescale by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the European Pulsar Timing Array (EPTA), the Parkes Pulsar Timing Array (PPTA), and the Chinese Pulsar Timing Array (CPTA) collaborations. We investigate the modifications in the neutrino flavor oscillations under the influence of the GWB reported by the PTA collaborations and we discuss how such effects could be potentially revealed in near-future neutrino detectors, possibly helping the discrimination of different models for the GWB below the nHz frequency range.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAhep-ph+1PRD(2023)·34 citations
36. 36*

    Gravitational Waves from SMBH Binaries in Light of the NANOGrav 15-Year Data

    John Ellis🇬🇧 · Malcolm Fairbairn🇬🇧 · Gert Hütsi🇪🇪 · Juhan Raidal🇪🇪 · Juan Urrutia🇪🇪 · Ville Vaskonen🇪🇪 · Hardi Veermäe🇪🇪

    The NANOGrav Collaboration has recently announced evidence for nHz gravitational waves (GWs), in the form of a Hellings-Downs angular correlation in the common-spectrum process that had been observed previously by them and other Pulsar Timing Arrays (PTAs). We analyze the possibility that these GWs originate from binary supermassive black holes (SMBHs) with total masses $\gtrsim 10^9{M}_{\odot }$. The spectral index of the GW signal differs at 95 % CL from that predicted for binary evolution by GW emission alone, and we find $>3\sigma$ evidence that environmental effects such as dynamical friction with gas, stars, and dark matter may be affecting the binary evolution. We estimate the required magnitude and spectrum of such environmental effects and comment on their possible implications for measurements of GWs at higher frequencies.

    ↳ astro-ph.COhep-phhep-thPRD(2024)·135 citations
37. 37*

    Cosmic topology. Part IIa. Eigenmodes, correlation matrices, and detectability of orientable Euclidean manifolds

    Johannes R. Eskilt🇳🇴 · Yashar Akrami🇺🇸 · Stefano Anselmi🇮🇹 · Craig J. Copi🇺🇸 · Andrew H. Jaffe🇬🇧 · Arthur Kosowsky🇺🇸 · Deyan P. Mihaylov🇺🇸 · Glenn D. Starkman🇺🇸 · Andrius Tamosiunas🇺🇸 · James B. Mertens🇺🇸 · Pip Petersen🇺🇸 · Samanta Saha🇺🇸 · Quinn Taylor🇺🇸 · Özenç Güngör (COMPACT Collaboration)🇺🇸

    If the Universe has non-trivial spatial topology, observables depend on both the parameters of the spatial manifold and the position and orientation of the observer. In infinite Euclidean space, most cosmological observables arise from the amplitudes of Fourier modes of primordial scalar curvature perturbations. Topological boundary conditions replace the full set of Fourier modes with specific linear combinations of selected Fourier modes as the eigenmodes of the scalar Laplacian. We present formulas for eigenmodes in orientable Euclidean manifolds with the topologies $E_1-E_6$, $E_{11}$, $E_{12}$, $E_{16}$, and $E_{18}$ that encompass the full range of manifold parameters and observer positions, generalizing previous treatments. Under the assumption that the amplitudes of primordial scalar curvature eigenmodes are independent random variables, for each topology we obtain the correlation matrices of Fourier-mode amplitudes (of scalar fields linearly related to the scalar curvature) and the correlation matrices of spherical-harmonic coefficients of such fields sampled on a sphere, such as the temperature of the cosmic microwave background (CMB). We evaluate the detectability of these correlations given the cosmic variance of the observed CMB sky. We find that topologies where the distance to our nearest clone is less than about 1.2 times the diameter of the last scattering surface of the CMB give a correlation signal that is larger than cosmic variance noise in the CMB. This implies that if cosmic topology is the explanation of large-angle anomalies in the CMB, then the distance to our nearest clone is not much larger than the diameter of the last scattering surface. We argue that the topological information is likely to be better preserved in three-dimensional data, such as will eventually be available from large-scale structure surveys.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2024)·23 citations
38. 38*

    Primordial magnetic field as a common solution of nanohertz gravitational waves and the Hubble tension

    Yao-Yu Li🇨🇳 · Chi Zhang🇨🇳 · Ziwei Wang🇨🇳 · Ming-Yang Cui🇨🇳 · Yue-Lin Sming Tsai🇨🇳 · Qiang Yuan🇨🇳 · Yi-Zhong Fan🇨🇳

    The origin of interstellar and intergalactic magnetic fields remains largely unknown. One possibility is that they are related to the primordial magnetic fields (PMFs) produced by, for instance, the phase transitions of the early Universe. In this paper, we show that the PMF-induced turbulence generated at around the QCD phase transition epoch--the characteristic magnetic field strength $B_{\mathrm{ch}}^{\ast }\sim \mathcal{O}(1)\mu \mathrm{G}$ and coherent length scale ${\ell }_{\mathrm{ch}}^{\ast }\sim \mathcal{O}(1)\mathrm{pc}$--can naturally accommodate nanohertz gravitational waves reported by pulsar timing array (PTA) collaborations. Moreover, the evolution of the PMFs to the recombination era with the form of $B_{\mathrm{ch}}\sim {\ell }_{\mathrm{ch}}^{-\alpha }$ can induce baryon density inhomogeneities, alter the recombination history, and alleviate the tension of the Hubble parameter $H_0$ and the matter clumpiness parameter $S_8$ between early- and late-time measurements for $0.88\le \alpha \le 1.17$ (approximate 95\% credible region based on three PTA likelihoods). The further evolved PMFs may account for the $\sim \mathcal{O}(10^{-16})$ Gauss extragalactic magnetic field inferred with GRB 221009A.

    ↳ astro-ph.HEastro-ph.COgr-qchep-phPRD(2024)·56 citations
39. 39*

    Footprints of the QCD Crossover on Cosmological Gravitational Waves at Pulsar Timing Arrays

    Gabriele Franciolini🇮🇹 · Davide Racco🇺🇸 · Fabrizio Rompineve🇨🇭

    Pulsar Timing Arrays (PTAs) have reported evidence for a stochastic gravitational wave (GW) background at nHz frequencies, possibly originating in the early Universe. We show that the spectral shape of the low-frequency (causality) tail of GW signals sourced at temperatures around $T\gtrsim 1$ GeV is distinctively affected by confinement of strong interactions (QCD), due to the corresponding sharp decrease in the number of relativistic species. Bayesian analyses in the NANOGrav 15 years and the previous International PTA datasets reveal a significant improvement in the fit with respect to cubic power-law spectra, previously employed for the causality tail. This suggests that the inclusion of Standard Model effects on GWs can have a potentially decisive impact on model selection.

    ↳ astro-ph.COastro-ph.HEgr-qchep-lat+1PRL(2024)·129 citations
40. 40*

    Dark Matter Spike surrounding Supermassive Black Holes Binary and the Nanohertz Stochastic Gravitational Wave Background

    Zhao-Qiang Shen🇨🇳 · Guan-Wen Yuan🇨🇳 · Yi-Ying Wang🇨🇳 · Yuan-Zhu Wang🇨🇳 · Yin-Jie Li🇨🇳 · Yi-Zhong Fan🇨🇳

    The NANOGrav, PPTA, EPTA, CPTA and MPTA collaborations have reported compelling evidence for the existence of the Stochastic Gravitational-Wave Background (SGWB). This inferred background's amplitude and frequency spectrum align closely with the astrophysical predictions for a signal originating from the population of supermassive black hole (SMBH) binaries. Considering these findings, we explore the possibility of detecting dark matter (DM) spikes surrounding SMBHs, which could alter the gravitational-wave waveform and influence the SGWB. We show that the evolution of SMBH binaries, driven by both gravitational radiation and the dynamic friction of the surrounding DM spike, presents observable effects in the nHz frequency domain of the SGWB. We also employ the Bayesian inference method to fit the SGWB spectra from the NANOGrav, EPTA, and PPTA. The model with DM spike improves the fittings to the former two data sets. The spike slope ${\gamma }_{\mathrm{sp}}$ is slightly smaller than 1, which may suggest that the spike is flattened during the inspiral of the SMBHBs.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAgr-qc+1Phys.Dark Univ.(2025)·65 citations
41. 41*

    Cosmic Superstrings Revisited in Light of NANOGrav 15-Year Data

    John Ellis🇬🇧 · Marek Lewicki🇵🇱 · Chunshan Lin🇵🇱 · Ville Vaskonen🇪🇪

    We analyze cosmic superstring models in light of NANOGrav 15-year pulsar timing data. A good fit is found for a string tension $G\mu \sim 10^{-12}-10^{-11}$ and a string intercommutation probability $p\sim 10^{-3}-10^{-1}$. Extrapolation to higher frequencies assuming standard Big Bang cosmology is compatible at the 68\% CL with the current LIGO/Virgo/KAGRA upper limit on a stochastic gravitational wave background in the 10 to 100 Hz range. The superstring interpretation of the NANOGrav data would be robustly testable by future experiments even in modified cosmological scenarios.

    ↳ astro-ph.COastro-ph.HEgr-qchep-ph+1PRD(2023)·143 citations
42. 42*

    The recent gravitational wave observation by pulsar timing arrays and primordial black holes: the importance of non-gaussianities

    Gabriele Franciolini🇮🇹 · Antonio Junior Iovino🇮🇹 · Ville Vaskonen🇪🇪 · Hardi Veermae🇪🇪

    We study whether the signal seen by pulsar timing arrays (PTAs) may originate from gravitational waves (GWs) induced by large primordial perturbations. Such perturbations may be accompanied by a sizeable primordial black hole (PBH) abundance. We improve existing analyses and show that PBH overproduction disfavors Gaussian scenarios for scalar-induced GWs at 2{\sigma} and single-field inflationary scenarios, accounting for non-Gaussianity, at 3{\sigma} as the explanation of the most constraining NANOGrav 15-year data. This tension can be relaxed in models where non-Gaussianites suppress the PBH abundance. On the flip side, the PTA data does not constrain the abundance of PBHs.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phPRL(2023)·281 citations
43. 43*

    The nanohertz stochastic gravitational wave background from cosmic string loops and the abundant high redshift massive galaxies

    Ziwei Wang🇨🇳 · Lei Lei🇨🇳 · Hao Jiao🇨🇦 · Lei Feng🇨🇳 · Yi-Zhong Fan🇨🇳

    Recently, pulsar timing array (PTA) experiments have provided compelling evidence for the existence of the nanohertz stochastic gravitational wave background (SGWB). In this work, we demonstrated that cosmic string loops generated from cosmic global strings offer a viable explanation for the observed nanohertz SGWB data, requiring a cosmic string tension parameter of $\log (G\mu )\sim -12$ and a loop number density of $\log N\sim 4$. Additionally, we revisited the impact of cosmic string loops on the abundance of massive galaxies at high redshifts. However, our analysis revealed challenges in identifying a consistent parameter space that can concurrently explain both the SGWB data and observations from the James Webb Space Telescope. This indicates the necessity for either extending the existing model employed in this research or acknowledging distinct physical origins for these two phenomena.

    ↳ astro-ph.HEastro-ph.COgr-qchep-phSCPMA(2023)·97 citations
44. 44*

    Probing the Dark Matter density with gravitational waves from super-massive binary black holes

    Anish Ghoshal🇵🇱 · Alessandro Strumia🇮🇹

    Supermassive black hole binaries source gravitational waves measured by Pulsar Timing Arrays. The frequency spectrum of this stochastic background is predicted more precisely than its amplitude. We argue that Dark Matter friction can suppress the spectrum around nHz frequencies, where it is measured, allowing to derive robust and significant bounds on the Dark Matter density, which, in turn, controls indirect detection signals from galactic centers. A precise spectrum of gravitational waves would translate in a tomography of the DM density profile, potentially probing DM particle-physics effects that induce a characteristic DM density profile, such as DM annihilations or de Broglie wavelength.

    ↳ astro-ph.COgr-qchep-phJCAP(2024)·60 citations
45. 45*

    Have pulsar timing array methods detected a cosmological phase transition?

    Andrea Addazi🇨🇳 · Yi-Fu Cai🇨🇳 · Antonino Marciano🇮🇹 · Luca Visinelli🇨🇳

    We show that the recent detection of a gravitational wave (GW) background reported by various pulsar timing array (PTA) collaborations including NANOGrav-15yr, PPTA, EPTA, and CPTA can be explained in terms of first order phase transitions (FOPTs) from dark sector models (DSM). Specifically, we explore a model for first order phase transitions that involves the majoron, a Nambu-Goldstone boson that is emerging from the spontaneous symmetry breaking of a $U(1{)}_L$ or $U(1{)}_{B-L}$ symmetry. We show how the predicted GW power spectrum, with a realistic choice of the FOPT parameters, is consistent with 1-$\sigma$ deviations from the estimated parameters of the background detected by the PTA collaborations.

    ↳ astro-ph.COastro-ph.HEhep-phhep-thPRD(2024)·111 citations
46. 46*

    Quantum data learning for quantum simulations in high-energy physics

    Lento Nagano🇯🇵 · Alexander Miessen🇨🇭 · Tamiya Onodera🇯🇵 · Ivano Tavernelli🇨🇭 · Francesco Tacchino🇨🇭 · Koji Terashi🇯🇵

    Quantum machine learning with parametrised quantum circuits has attracted significant attention over the past years as an early application for the era of noisy quantum processors. However, the possibility of achieving concrete advantages over classical counterparts in practical learning tasks is yet to be demonstrated. A promising avenue to explore potential advantages is the learning of data generated by quantum mechanical systems and presented in an inherently quantum mechanical form. In this article, we explore the applicability of quantum-data learning to practical problems in high-energy physics, aiming to identify domain specific use-cases where quantum models can be employed. We consider quantum states governed by one-dimensional lattice gauge theories and a phenomenological quantum field theory in particle physics, generated by digital quantum simulations or variational methods to approximate target states. We make use of an ansatz based on quantum convolutional neural networks and numerically show that it is capable of recognizing quantum phases of ground states in the Schwinger model, (de)confinement phases from time-evolved states in the ${\mathbb{Z}}_2$ gauge theory, and that it can extract fermion flavor/coupling constants in a quantum simulation of parton shower. The observation of non-trivial learning properties demonstrated in these benchmarks will motivate further exploration of the quantum-data learning architecture in high-energy physics.

    ↳ quant-phhep-lathep-phPRResearch(2023)·18 citations
47. 47*

    Cosmic Acceleration and Turns in the Swampland

    Julian Freigang🇩🇪 · Dieter Lust🇩🇪 · Guo-En Nian🇳🇱 · Marco Scalisi🇩🇪

    We argue that field trajectories, which lead to cosmic acceleration and feature rapid turns near the boundary of the moduli space, are in the Swampland. We obtain this result by assuming the validity of the Swampland Distance Conjecture (SDC) in the presence of a positive scalar potential and by focusing on hyperbolic spaces, as prototype geometries of infinite distance limits of Calabi-Yau compactifications. We find that, in a quasi-de Sitter space with Hubble rate $H$ and acceleration parameter $ϵ$, the turning rate $\Omega$ is upper bounded such as $\Omega /H<\mathcal{O}(\sqrt{ϵ})$. Therefore, field trajectories consistent with the SDC can only have a negligible deviation from geodesics. This has direct implications for the realization and consistency of multi-field scenarios in string theory. Moreover, it implies a tension between asymptotic accelerating expansion, consistent with observations, and the de Sitter conjecture.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2023)·18 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.