Wed·Feb 2, 2022Wednesday·February 2, 2022

1. 01*

   Modelling vector-like quarks in partial compositeness framework

   Avik Banerjee🇸🇪 · Diogo Buarque Franzosi🇸🇪 · Gabriele Ferretti🇸🇪

   Composite Higgs models, together with partial compositeness, predict the existence of new scalars and vector-like quarks (partners) at and above the TeV scale. Generically, the presence of these additional scalars opens up new decay topologies for the partners. In this paper we show how to systematically construct the general low energy Lagrangian to capture this feature. We emphasize the specific pattern in the top-partner spectrum arising in this class of models. We then present a concrete realization in the context of the SU(5)/SO(5) coset. We show that the top-partners in this model can have significant branching ratios to the additional scalars and a third generation quark, compared to the usual Standard Model channels. Amongst the most promising signatures at the LHC are final states containing a diphoton resonance along with a top quark.

   hep-phhep-exJHEP(2022)·51 citations
2. 02*

   Hadronic structure on the light-front IV: Heavy and light Baryons

   Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸

   This work is a continuation in our series of papers, that addresses quark models of hadronic structure on the light front. The chief focus of this paper is the quantum-mechanical solution of the three-quark model Hamiltonian, describing baryons. In Jacobi coordinates, we use a harmonic oscillator basis for the transverse directions. For the longitudinal momentum fractions $x_i$, the pertinent basis follows from quantum mechanics in a "triangular cup" potential, which we solve exactly. We calculate the masses and light front wave functions for the flavor symmetric ${\frac{3}{2}}^{+}$ baryons $bbb,ccc,sss,uuu$.

   hep-phhep-latnucl-thPRD(2023)·21 citations
3. 03*

   Axion cosmology in the presence of non-trivial Nambu-Goldstone modes

   Motohiko Yoshimura🇯🇵

   Axion cosmology is reexamined taking into account effect of kinetic pseudo Nambu-Goldstone modes, with its importance recently pointed out. When Peccei-Quinn (PQ) symmetry is broken by a chiral U(1) singlet, it is found that the effect of kinetic Nambu-Goldstone mode makes the axion dark matter untenable. When PQ symmetry is extended and is broken by two singlets, we find axion cosmology to work, but there are several differences from the axion cosmology studied in the literature. The differences are (1) ordinary type of dark matter scaling as $1/{\mathrm{cosmic}\mathrm{scale}\mathrm{factor}}^3$ arising from a modulus field and not from the usual angular field, (2) mass of the dark matter quantum in the ultralight range, $(10^{-32}\sim 10^{-14})$eV, (3) emergence of dark energy with the present density of order (a few meV)${}^4$ consistent with observations, (4) presence of a long range spin-dependent force, (5) slow-roll inflation after PQ symmetry breaking when conformal coupling to gravity is introduced.

   hep-phastro-ph.COhep-exPRD(2022)·2 citations
4. 04*

   Generalized parton distributions of sea quarks in the proton from nonlocal chiral effective theory

   Fangcheng He🇨🇳 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸 · A. W. Thomas🇦🇺 · P. Wang🇨🇳

   We calculate the spin-averaged generalized parton distributions (GPDs) of sea quarks in the proton at zero skewness from nonlocal covariant chiral effective theory, including one-loop contributions from intermediate states with pseudoscalar mesons and octet and decuplet baryons. A relativistic regulator is generated from the nonlocal Lagrangian where a gauge link is introduced to guarantee local gauge invariance, with additional diagrams from the expansion of the gauge link ensuring conservation of electric charge and strangeness. Flavor asymmetries for sea quarks at zero and finite momentum transfer, as well as strange form factors, are obtained from the calculated GPDs, and results compared with phenomenological extractions and lattice QCD.

   hep-phhep-exnucl-thPRD(2022)·19 citations
5. 05*

   Pion axioproduction: The Delta resonance contribution

   Thomas Vonk🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪

   The process of pion axioproduction, $aN\to \pi N$, with an intermediate $\Delta$ resonance is analyzed using baryon chiral parturbation theory. The $\Delta$ resonance is included in two ways: First, deriving the $a\Delta N$-vertices, the axion is brought into contact with the resonance, and, second, taking the results of $\pi N$ elastic scattering including the $\Delta$, it is implicitly included in the form of a pion rescattering diagram. As a result, the partial wave cross section of axion-nucleon scattering shows an enhancement in the energy region around the $\Delta$ resonance. Because of the isospin breaking, the enhancement is not as pronounced as previously anticipated. However, since the isospin breaking here is much milder than that for usual hadronic processes, novel axion search experiments might still exploit this effect.

   hep-phhep-exnucl-exnucl-thPRD(2022)·15 citations
6. 06*

   Transverse Polarization of Hyperons Produced in Semi-Inclusive Deep Inelastic Scattering

   Yuji Koike🇯🇵 · Kazuki Takada🇯🇵 · Sumire Usui🇯🇵 · Kenta Yabe🇯🇵 · Shinsuke Yoshida🇨🇳

   We study the transverse polarization of hyperons produced in semi-inclusive deep inelastic scattering, $ep\to e{\Lambda }^{\uparrow }X$, in the framework of the collinear twist-3 factorization. The cross section from the twist-3 distribution functions and the twist-3 quark fragmentation functions is computed in the leading order with respect to the QCD coupling constant. The constraint relations among the twist-3 FFs are taken into account to simplify the formula. The formula is relevant to large-$P_T$ hyperon production in the future Electron-Ion-Collider experiment.

   hep-phnucl-thPRD(2022)·11 citations
7. 07*

   The ${\bar{B}}^0\to D^{\ast +}{\bar{D}}^{\ast 0}{K}^{-}$ reaction to detect the $I=0,J^P=1^{+}$ partner of the $X_0(2866)$

   L. R. Dai🇨🇳 · R. Molina🇪🇸 · E. Oset🇪🇸

   We have chosen the ${\bar{B}}^0\to D^{\ast +}{\bar{D}}^{\ast 0}{K}^{-}$ reaction in order to observe the $I=0,J^P=1^{+}$ ($R_1$) partner state of the $X_0(2866)$ stemming from the $D^{\ast }{\bar{K}}^{\ast }$ molecular picture. The reaction proceeds via external emission in the most favored Cabibbo decay mode and one observes the $R_1$ state as a very strong peak versus the background in the $D^{\ast +}{K}^{-}$ spectrum. The branching ratio for $R_1$ production in this reaction is estimated of the order of $4\times 10^{-3}$. The method used, applied to the $B^{+}\to D^{-}{D}^{+}{K}^{+}$ reaction, produces a ratio of signal to background in the $D^{-}{K}^{+}$ spectrum in very good agreement with the LHCb experiment that observed the $X_0(2866)$.

   hep-phhep-exPLB(2022)·19 citations
8. 08*

   Using the non-hydrodynamic mode to study the onset of hydrodynamic behavior in ultraperipheral symmetric nuclear collisions

   Nikhil Hatwar🇮🇳 · Madhukar Mishra🇮🇳

   With the attempts of extending the hydrodynamic framework of heavy-ion collision to proton-proton and other small and low energy systems, we are confronted with the question of how small the system can get and still be safely modelled as a fluid. One of the transport coefficients required in the $2^{nd}$ order relativistic viscous hydrodynamics is the shear relaxation time, inclusion of which solves the causality violation problem in the Navier-Stokes equation. In phenomenological studies this coefficient has been taken as a constant and much attention has gone into finding and fixing the shear viscosity to entropy density ratio, $\eta /s$. This transport coefficient also happens to control the non-hydrodynamic mode of the out-of-equilibrium hydrodynamics theory. It has been predicted that for decreasing system size, observables become sensitive to variation in shear relaxation time as a result of increasing dominance of non-hydrodynamic mode, which could potentially indicate breakdown of hydrodynamics. In this study, we try to test this prediction in the peripheral Pb-Pb collisions at $2.76$ TeV and Au-Au collisions at $200$ GeV, with IPGlasma initial condition and $(2+1)-$Dimensional viscous hydrodynamics. We find that elliptic flow does show adequate sensitivity to variation in relaxation time for decreasing system size. The multiplicity rapidity density limit for applicability of hydrodynamics is found to be around $dN/dy\approx 10$, with the possibility of refinement in this value given a way to improve the centrality resolution in experimental data for referencing in peripheral collisions.

   hep-phPRC(2022)·5 citations
9. 09*

   Softly-broken $A_4$ or $S_4$ 3HDMs with stable states

   Ivo de Medeiros Varzielas🇵🇹 · Diogo Ivo🇵🇹

   We study multi-Higgs models with a triplet of $A_4$ or $S_4$ symmetry that is softly-broken. Focusing on parameters that softly break the respective symmetries but preserve the directions of the vacuum expectation values of the triplet we analyse the masses of physical states and discuss their decays. In contrast with previously studied symmetries, we find some cases with stable states that are protected by residual symmetries left unbroken by both the soft-breaking parameters and by the vacuum.

   hep-phEPJC(2022)·10 citations
10. 10*

    What's Anomalous in LHC Jets?

    Thorsten Buss🇩🇪 · Barry M. Dillon🇩🇪 · Thorben Finke🇩🇪 · Michael Krämer🇩🇪 · Alessandro Morandini🇩🇪 · Alexander Mück🇩🇪 · Ivan Oleksiyuk🇩🇪 · Tilman Plehn🇩🇪

    Searches for anomalies are a significant motivation for the LHC and help define key analysis steps, including triggers. We discuss specific examples how LHC anomalies can be defined through probability density estimates, evaluated in a physics space or in an appropriate neural network latent space, and discuss the model-dependence in choosing an appropriate data parameterisation. We illustrate this for classical k-means clustering, a Dirichlet variational autoencoder, and invertible neural networks. For two especially challenging scenarios of jets from a dark sector we evaluate the strengths and limitations of each method.

    hep-phSciPost Phys.(2023)·38 citations
11. 11*

    A novel search for high-frequency gravitational waves with low-mass axion haloscopes

    Valerie Domcke🇨🇭 · Camilo Garcia-Cely🇩🇪 · Nicholas L. Rodd🇨🇭

    Gravitational waves (GWs) generate oscillating electromagnetic effects in the vicinity of external electric and magnetic fields. We discuss this phenomenon with a particular focus on reinterpreting the results of axion haloscopes based on lumped-element detectors, which probe GWs in the 100 kHz-100 MHz range. Measurements from ABRACADABRA and SHAFT already place bounds on GWs, although the present strain sensitivity is weak. However, we demonstrate that the sensitivity scaling with the volume of such instruments is significant - faster than for axions - and so rapid progress will be made in the future. With no modifications, DMRadio-m${}^3$ will have a GW strain sensitivity of $h\sim 10^{-20}$ at 200 MHz. A simple modification of the pickup loop used to readout the induced magnetic flux can parametrically enhance the GW sensitivity, particularly at lower frequencies.

    hep-phastro-ph.COastro-ph.IMgr-qc+1PRL(2022)·166 citations
12. 12*

    Cooling of Neutron Stars admixed with Light Dark Matter: a case study

    M. Ángeles Pérez-García🇪🇸 · H. Grigorian🇷🇺 · C. Albertus🇪🇸 · D. Barba🇪🇸 · J. Silk🇫🇷

    Neutron Stars (NSs) are born as hot, lepton-rich objects that evolve according to the standard paradigm through subsequent stages where they radiate the excess of energy by emitting, first, neutrinos and, later on, photons. Current descriptions based on Standard Model calculations cannot fully explain all the existing cooling data series for the dozens of objects that have been reported. In this work, we consider the intriguing possibility that cooling NSs could be actually admixed with a fraction of light dark matter (LDM), $\chi$. We focus on a particular case study assuming a generic light candidate with mass $m_{\chi }=0.1$ $GeV/{\mathrm{c}}^2$ that undergoes self-annihilating reactions through pseudoscalar mediators producing neutrinos in the final state. We include one additional feature, allowing thermal conduction from LDM while inside the dark core. By performing simulations of the temperature evolution in the NS, we find that cooling patterns could be distorted by the presence of LDM and discuss these results in light of their observability.

    hep-phnucl-thPLB(2022)·17 citations
13. 13*

    Two-loop amplitude generation in OpenLoops

    Stefano Pozzorini🇨🇭 · Natalie Schär🇨🇭 · Max F. Zoller🇨🇭

    Numerical tools, such as OpenLoops, provide NLO scattering amplitudes for a very wide range of hard scattering amplitudes in a fully automated way. In order to match the numerical precision of current and future experiments, however, the higher precision of NNLO calculations is essential, and their automation in a similar tool highly desirable. In our approach, D-dimensional amplitudes are decomposed into loop-momentum tensor integrals with coefficients constructed in four dimensions and rational terms. We present a fully generic algorithm for the efficient numerical construction of the tensor coefficients, which constitutes an important building block for an automated NNLO tool.

    hep-phSciPost Phys.Proc.(2022)·2 citations
14. 14*

    X-ray morphology of cluster-mass haloes in self-interacting dark matter

    Xuejian Shen🇺🇸 · Thejs Brinckmann🇮🇹 · David Rapetti🇺🇸 · Mark Vogelsberger🇺🇸 · Adam Mantz🇺🇸 · Jesús Zavala🇮🇸 · Steven W. Allen🇺🇸

    We perform cosmological zoom-in simulations of $19$ relaxed cluster-mass haloes with the inclusion of adiabatic gas in the cold dark matter (CDM) and self-interacting dark matter (SIDM) models. These clusters are selected as dynamically relaxed clusters from a parent simulation with $M_{200}\simeq 1-3\times 10^{15}{\mathrm{M}}_{\odot }$. Both the dark matter and the intracluster gas distributions in SIDM appear more spherical than their CDM counterparts. Mock X-ray images are generated based on the simulations and are compared to the real X-ray images of $84$ relaxed clusters selected from the Chandra and ROSAT archives. We perform ellipse fitting for the isophotes of mock and real X-ray images and obtain the ellipticities at cluster-centric radii of $r\simeq 0.1-0.2R_{200}$. The X-ray isophotes in SIDM models with increasing cross-sections are rounder than their CDM counterparts, which manifests as a systematic shift in the distribution function of ellipticities. Unexpectedly, the X-ray morphology of the observed non-cool-core clusters agrees better with SIDM models with cross-section $(\sigma /m)=0.5-1{\mathrm{cm}}^2/\mathrm{g}$ than CDM and SIDM with $(\sigma /m)=0.1{\mathrm{cm}}^2/\mathrm{g}$. Our statistical analysis indicates that the latter two models are disfavored at the $68\%$ confidence level (as conservative estimates). This conclusion is not altered by shifting the radial range of measurements or applying temperature selection criterion. However, the primary uncertainty originates from the lack of baryonic physics in the adiabatic model, such as cooling, star formation and feedback effects, which still have the potential to reconcile CDM simulations with observations.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2022)·23 citations
15. 15*

    Compactness bounds in General Relativity

    Artur Alho🇵🇹 · José Natário🇵🇹 · Paolo Pani🇮🇹 · Guilherme Raposo🇮🇹

    A foundational theorem due to Buchdahl states that, within General Relativity (GR), the maximum compactness $\mathcal{C}\equiv GM/(R{c}^2)$ of a static, spherically symmetric, perfect fluid object of mass $M$ and radius $R$ is $\mathcal{C}=4/9$. As a corollary, there exists a compactness gap between perfect fluid stars and black holes (where $\mathcal{C}=1/2$). Here we generalize Buchdahl's result by introducing the most general equation of state for elastic matter with constant longitudinal wave speeds and apply it to compute the maximum compactness of regular, self-gravitating objects in GR. We show that: (i) the maximum compactness grows monotonically with the longitudinal wave speed; (ii) elastic matter can exceed Buchdahl's bound and reach the black hole compactness $\mathcal{C}=1/2$ continuously; (iii) however, imposing subluminal wave propagation lowers the maximum compactness bound to $\mathcal{C}\approx 0.462$, which we conjecture to be the maximum compactness of \emph{any} static elastic object satisfying causality; (iv) imposing also radial stability further decreases the maximum compactness to $\mathcal{C}\approx 0.389$. Therefore, although anisotropies are often invoked as a mechanism for supporting horizonless ultracompact objects, we argue that the black hole compactness cannot be reached with physically reasonable matter within GR and that true black hole mimickers require either exotic matter or beyond-GR effects.

    ↳ gr-qcastro-ph.HEhep-phPRD(2022)·53 citations
16. 16*

    Earth rotation and time-domain reconstruction of polarization states for continuous gravitational waves from a known pulsar

    Naoto Kuwahara🇯🇵 · Hideki Asada🇯🇵

    We consider effects of the Earth rotation on antenna patterns of a ground-based gravitational wave (GW) detector in a general metric theory that allows at most six polarization states (two spin-0, two spin-1 and two spin-2) in a four-dimensional spacetime. By defining the cyclically averaged antenna matrix for continuous GWs from a known pulsar, we show that waveforms for each polarization state can be uniquely reconstructed in time domain from a given set of the strain outputs at a single detector. Constraining the propagation speed of extra polarization modes, if they coexist with the transverse-traceless modes, is also discussed. We examine also possible effects due to the length-of-day modulation as well as a secular change in the pulsar spin period.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2022)·5 citations
17. 17*

    Transport of hard probes through glasma

    Margaret E. Carrington🇨🇦 · Alina Czajka🇵🇱 · Stanislaw Mrowczynski🇵🇱

    We calculate the transverse momentum broadening $\hat{q}$ and collisional energy loss $dE/dx$ of hard probes traversing an evolving glasma during the earliest phase of a relativistic heavy-ion collision. We use a Fokker-Planck equation and apply a proper time expansion to describe the temporal evolution of the glasma. The correlators of the chromodynamic fields that determine the Fokker-Planck collision terms, which in turn provide $\hat{q}$ and $dE/dx$, are computed to fifth order. Both transport coefficients are strongly dependent on time. The maximum values they acquire before the proper time expansion breaks down are large: $\hat{q}$ is of the order of a few $\mathrm{Ge}{\mathrm{V}}^2/fm$ and $dE/dx\sim 1GeV/fm$. Their precise values depend on the probe's velocity $\mathbf{v}$, the saturation momentum $Q_s$, and an IR regulator $m$ that is related to the confinement scale. We study the dependence of our results on these quantities. Different regularization procedures are analysed and shown to produce similar results. We also discuss the validity of the proper time expansion and the compatibility of the approximations that are inherent in the derivation of the Fokker-Planck equation. We show that hard probes lose a comparable amount of energy when they propagate through the short-lived glasma phase, and the long-lasting hydrodynamic phase. The conclusion is that the glasma plays an important role in jet quenching.

    ↳ nucl-thhep-phPRC(2022)·65 citations
18. 18*

    Exploring the $\theta$-vacuum structure in the functional renormalization group approach

    Kenji Fukushima🇯🇵 · Takuya Shimazaki🇯🇵 · Yuya Tanizaki🇯🇵

    We investigate the $\theta$-vacuum structure and the 't Hooft anomaly at $\theta =\pi$ in a simple quantum mechanical system on $S^1$ to scrutinize the applicability of the functional renormalization group (fRG) approach. Even though the fRG is an exact formulation, a naive application of the fRG equation would miss contributions from the $\theta$ term due to the differential nature of the formulation. We first review this quantum mechanical system on $S^1$ that is solvable with both the path integral and the canonical quantization. We discuss how to construct the quantum effective action including the $\theta$ dependence. Such an explicit calculation poses a subtle question of whether a Legendre transform is well defined or not for general systems with the sign problem. We then consider a deformed theory to relax the integral winding by introducing a wine-bottle potential with the finite depth $\propto g$, so that the original $S^1$ theory is recovered in the $g\to \infty$ limit. We numerically solve the energy spectrum in the deformed theory as a function of $g$ and $\theta$ in the canonical quantization. We test the efficacy of the simplest local potential approximation (LPA) in the fRG approach and find that the correct behavior of the ground state energy is well reproduced for small $\theta$. When the energy level crossing is approached, the LPA flow breaks down and fails in describing the ground state degeneracy expected from the 't Hooft anomaly. We finally turn back to the original theory and discuss an alternative formulation using the Villain lattice action. The analysis with the Villain lattice at $\theta =\pi$ indicates that the nonlocality of the effective action is crucial to capture the level crossing behavior of the ground states.

    ↳ hep-thhep-phJHEP(2022)·7 citations
19. 19*

    AutoSourceID-Light. Fast Optical Source Localization via U-Net and Laplacian of Gaussian

    Fiorenzo Stoppa · Paul Vreeswijk · Steven Bloemen · Saptashwa Bhattacharyya🇮🇳 · Sascha Caron🇳🇱 · Gu{\dh}laugur Jóhannesson🇮🇸 · Roberto Ruiz de Austri🇪🇸 · Chris van den Oetelaar · Gabrijela Zaharijas🇸🇮 · Paul. J. Groot · Eric Cator · Gijs Nelemans

    $\text{Aims}$. With the ever-increasing survey speed of optical wide-field telescopes and the importance of discovering transients when they are still young, rapid and reliable source localization is paramount. We present AutoSourceID-Light (ASID-L), an innovative framework that uses computer vision techniques that can naturally deal with large amounts of data and rapidly localize sources in optical images. $\text{Methods}$. We show that the AutoSourceID-Light algorithm based on U-shaped networks and enhanced with a Laplacian of Gaussian filter (Chen et al. 1987) enables outstanding performances in the localization of sources. A U-Net (Ronneberger et al. 2015) network discerns the sources in the images from many different artifacts and passes the result to a Laplacian of Gaussian filter that then estimates the exact location. $\text{Results}$. Application on optical images of the MeerLICHT telescope demonstrates the great speed and localization power of the method. We compare the results with the widely used SExtractor (Bertin & Arnouts 1996) and show the out-performances of our method. AutoSourceID-Light rapidly detects more sources not only in low and mid crowded fields, but particularly in areas with more than 150 sources per square arcminute.

    ↳ astro-ph.IMhep-phAstron.Astrophys.(2022)·4 citations
20. 20*

    Gamma-ray Cosmology and Tests of Fundamental Physics

    J. Biteau🇫🇷 · M. Meyer🇩🇪

    The propagation of gamma-rays over cosmological distances is the subject of extensive theoretical and observational research at GeV and TeV energies. The mean free path of gamma-rays in the cosmic web is limited above 100 GeV due to the production of electrons and positrons on the cosmic optical and infrared backgrounds. Electrons and positrons cool in the intergalactic medium while gyrating in its magnetic fields, which could cause either its global heating or the production of lower-energy secondary gamma-rays. The energy distribution of gamma-rays surviving the cosmological journey carries observed absorption features that gauge the emissivity of baryonic matter over cosmic time, constrain the distance scale of $\Lambda$CDM cosmology, and limit the alterations of the interaction cross section. Competitive constraints are in particular placed on the cosmic star-formation history as well as on phenomena expected from quantum gravity and string theory, such as the coupling to hypothetical axion-like particles or the violation of Lorentz invariance. Recent theoretical and observational advances offer a glimpse of the multi-wavelength and multi-messenger path that the new generation of gamma-ray observatories is about to open.

    ↳ astro-ph.COastro-ph.HEhep-phGalaxies(2022)·38 citations
21. 21*

    Sexaquark dilemma in neutron stars and its solution by quark deconfinement

    M. Shahrbaf🇵🇱 · D. Blaschke🇵🇱 · S. Typel🇩🇪 · G. R. Farrar🇺🇸 · D. E. Alvarez-Castillo🇵🇱

    Following the idea that a stable sexaquark state with quark content (uuddss) would have gone unnoticed by experiment so far and that such a particle would be a good dark matter candidate, we investigate the possible role of a stable sexaquark in the physics of compact stars given the stringent constraints on the equation of state that stem from observations of high mass pulsars and GW170817 bounds on the compactness of intermediate mass stars. We find that there is a "sexaquark dilemma" (analogous to the hyperon dilemma) for which the dissociation of the sexaquark in quark matter is a viable solution fulfilling all present constraints from multi-messenger astronomy. The parameters needed to model the hybrid star including sexaquarks are in line with parameters of pre-existing quark- and hadronic-matter models. We find that current constraints -- tidal deformability in accordance with GW170817 and maximum mass above the lower limit from PSR J0740+6620 -- can be satisfied two ways: with early quark deconfinement such that neither sexaquarks nor hyperons are present in any NS interiors, or with later deconfinement such that a neutron-sexaquark shell surrounds the inner quark matter core.

    ↳ nucl-thastro-ph.HEhep-phPRD(2022)·53 citations
22. 22*

    BICEP/Keck data and Quadratic Gravity

    Alberto Salvio🇮🇹

    The recent results of the BICEP and Keck collaborations have put stringent bounds on many inflationary models, including some well-motivated ones. This is certainly the case when gravity remains described by Einstein's theory up to the inflationary scale, but can be avoided by introducing quadratic-in-curvature terms that are effective at that scale. Recently it has also been shown that these terms can UV complete gravity respecting stability and unitarity. Here the predictions of such quadratic gravity are computed and compared with the BICEP/Keck constraints by focusing on some of the inflationary scenarios that are best-motivated from the particle physics point of view and are already ruled out in Einstein gravity: (critical) Higgs inflation and natural inflation. The first scenario can be considered as the most economical option as the inflaton is identified with the only known elementary scalar field in the Standard Model and the near criticality of the Standard Model is used to remain in the perturbative regime. In the second one a pseudo-Nambu-Goldstone boson contributes to the inflationary dynamics and its potential is naturally flat. It is shown that in both scenarios one can restore the agreement with the observational constraints in quadratic gravity.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2022)·36 citations
23. 23*

    IceCube and High-Energy Cosmic Neutrinos

    Francis Halzen🇺🇸 · Ali Kheirandish🇺🇸

    The IceCube experiment discovered PeV-energy neutrinos originating beyond our Galaxy with an energy flux that is comparable to that of TeV-energy gamma rays and EeV-energy cosmic rays. Neutrinos provide the only unobstructed view of the cosmic accelerators that power the highest energy radiation reaching us from the universe. We will review the rationale for building kilometer-scale neutrino detectors that led to the IceCube project, which transformed a cubic kilometer of deep transparent natural Antarctic ice into a neutrino telescope of such a scale. We will summarize the results from the first decade of operations: the status of the observations of cosmic neutrinos and of their first identified source, the supermassive black hole TXS 0506+056. Subsequently, we will introduce the phenomenology associated with cosmic accelerators in some detail. Besides the search for the sources of Galactic and extragalactic cosmic rays, the scientific missions of IceCube and similar instruments under construction in the Mediterranean Sea and Lake Baikal include the observation of Galactic supernova explosions, the search for dark matter, and the study of neutrinos themselves. This review resulted from notes created for summer school lectures and should be accessible to nonexperts.

    ↳ astro-ph.HEhep-exhep-ph25 citations
24. 24*

    Induced gravitational waves from the cosmic coincidence

    Shyam Balaji🇫🇷 · Joseph Silk🇫🇷 · Yi-Peng Wu🇫🇷

    The induced gravitational wave (GW) background from enhanced primordial scalar perturbations is one of the most promising observational consequences of primordial black hole (PBH) formation from inflation. We investigate the induced GW spectrum ${\Omega }_{\text{IGW}}$ from single-field inflation in the general ultra-slow-roll (USR) framework, restricting the peak frequency band to be inside $10^{-3}$-$1$ Hz and saturating PBH abundance to comprise all dark matter (DM) in the ultralight asteroid-mass window. By invoking successful baryogenesis driven by USR inflation, we verify the viable parameter space for the specific density ratio between baryons and PBH DM observed today, the so-called "cosmic coincidence." We show that the cosmic coincidence requirement bounds the spectral index $n_{\mathrm{UV}}$ in the high frequency limit, ${\Omega }_{\text{IGW}}(f\gg 1)\propto f^{-2n_{\mathrm{UV}}}$, into $0<n_{\mathrm{UV}}<1$, which implies that baryogenesis triggered by USR inflation for PBHs in the mass range of $10^{-16}$-$10^{-12}{M}_{\odot }$ can be tested by upcoming Advanced LIGO and Virgo data and next generation experiments such as LISA, Einstein Telescope, TianQin and DECIGO.

    ↳ astro-ph.COhep-phJCAP(2022)·59 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.