Thu·Jul 25, 2019Thursday·July 25, 2019

1. 01*

   Vector Self-Interacting Dark Matter

   Ian Chaffey🇺🇸 · Philip Tanedo🇺🇸

   We present a model of vector dark matter that interacts through a low-mass vector mediator based on the Higgsing of an SU(2) dark sector. The dark matter is charged under a U(1) gauge symmetry. Even though this symmetry is broken, the residual global symmetries of the theory prevent dark matter decay. We present the behavior of the model subject to the assumption that the dark matter abundance is due to thermal freeze out, including self-interaction targets for small scale structure anomalies and the possibility of interacting with the Standard Model through the vector mediator.

   hep-phPRD(2020)·9 citations
2. 02*

   Calculating $\beta$-function coefficients of Renormalization Group Equations

   Joydeep Roy🇨🇳

   Renormalization Group Equations (RGEs) are indispensable tool to know the behavior of physical parameters at different energy scales. They are also extremely crucial if we want to extend our known Standard Model gauge group by some extra gauge groups and the $\beta$-functions are the soul of these RGEs. In literature although it is quite common to find long, final expressions of the RGEs, unfortunately it is difficult to find any pedagogical review to calculate these $\beta$-function coefficients explicitly from the known formulae. Therefore in this note we shall try to explain the detail calculations of RGEs by giving some explicit examples taken from the literature. The goal and hope is to provide a hand on experience on calculating these RGEs for the young readers.

   hep-phhep-th6 citations
3. 03*

   Mesonic dynamics and QCD phase transition

   Shi Yin🇨🇳 · Rui Wen🇨🇳 · Wei-jie Fu🇨🇳

   We study the nontrivial dispersion relation of mesons resulting from the splitting of the transversal and longitudinal mesonic wave function renormalizations, and its influences on the QCD phase transition, equation of state, and the fluctuations of baryon number. The calculations are performed in a two-flavor low energy effective model within the functional renormalization group approach. We find that influences of the splitting mesonic wave function renormalizations on the equilibrium thermodynamical bulk properties are mild. Furthermore, we have compare the fixed and running expansion for the effective potential in detail, through which the role of the field-dependent meson and quark wave function renormalizations could be inferred.

   hep-phPRD(2019)·25 citations
4. 04*

   Dielectron production in pion-nucleon reactions and form factor of baryon transition within the time-like region

   A.P.Jerusalimov🇷🇺 · G.I.Lykasov🇷🇺

   Dielectron production in reactions ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ and ${\pi }^{-}p\to n{e}^{+}{e}^{-}\gamma$ at energies less than 1 GeV is studied assuming electron-positron pair production to occur in the virtual time-like photon splitting process. Theoretical predictions of the effective mass distribution of dielectrons and their angular dependence are presented. Extraction of the electromagnetic form factor of baryon transition in the time-like region from future experiments of the HADES Collaboration is discussed.

   hep-ph0 citations
5. 05*

   Measuring the Weizsaecker-Williams distribution of linearly polarized gluons at an electron-ion collider through dijet azimuthal asymmetries

   Vladimir Skokov🇺🇸

   The Weizsaecker-Williams transverse momentum dependent (TMD) gluon distributions can be probed in the production of a hard dijet in semi-inclusive DIS. This process is sensitive not only to the conventional but also to the linearly polarized gluon distribution. The latter gives rise to an azimuthal dependence of the dijet cross section and therefore can be distinguished from the former. Feasibility study of a measurement of these TMDs through dijet production at a future electron-ion collider shows that the extraction of the distribution of linearly polarized gluons with a statistical accuracy of 5% will require estimated luminosity of 20 fb^{-1} /A.

   hep-phPoS(2019)·1 citation
6. 06*

   Pion-induced Drell-Yan processes within TMD factorization

   Alexey Vladimirov🇩🇪

   We extract the pion transverse momentum dependent (TMD) parton distribution by fitting the pion-induced Drell-Yan process within the framework of TMD factorization. The analysis is done at the next-to-next-to-leading order (NNLO) with proton TMD distribution and non-perturbative TMD evolution extracted earlier in the global fit. We observe the significant difference in the normalization of transverse momentum differential cross-section measured by E615 experiment and the theory prediction.

   hep-phJHEP(2019)·64 citations
7. 07*

   $P$-wave contributions to $B_{(s)}\to \psi K\pi$ decays in perturbative QCD approach

   Ya Li🇨🇳 · Zhou Rui🇨🇳 · Zhen-Jun Xiao🇨🇳

   In this work, we studied the quasi-two-body decays $B_{(s)}\to \psi [K^{\ast }(892),K^{\ast }(1410),$ $K^{\ast }(1680)]\to \psi K\pi$ by employing the perturbative QCD (PQCD) factorization approach, where the charmonia $\psi$ represents $J/\psi$ and $\psi (2S)$. The corresponding decay channels are studied by constructing the kaon-pion distribution amplitude (DA) ${\Phi }_{K\pi }^{\mathrm{P}}$, which contained the important final state interactions between the kaon and pion in the resonant region. The relativistic Breit-Wigner formulas are adopted to parameterize the time-like form factor $F_{K\pi }$ appeared in the kaon-pion DAs. The SU(3) flavor symmetry breaking effect resulting from the mass difference between kaon and pion is taken into account, which makes significant contributions to the longitudinal polarizations. We accommodate well the observed branching ratios and the polarization fractions of the $B_{(s)}\to \psi K^{\ast }(892)\to \psi K\pi$ by tuning the hadronic parameters for the kaon-pion DAs. The PQCD predictions for the $B_{(s)}\to \psi [K^{\ast }(1410),K^{\ast }(1680)]\to \psi K\pi$ modes from the same set of parameters can be tested by the future precise data from the LHCb and the Belle II experiments.

   hep-phCPC(2020)·15 citations
8. 08*

   Constraining Dimension-Six Nonminimal Lorentz-Violating Electron--Nucleon Interactions with EDM Physics [CPT'19]

   Jonas B. Araujo🇧🇷 · A. Blin🇵🇹 · Marcos Sampaio🇧🇷 · Manoel M. Ferreira Jr🇧🇷

   Electric dipole moments of atoms can arise from P-odd and T-odd electron--nucleon couplings. This work studies a general class of dimension-six electron--nucleon interactions mediated by Lorentz-violating tensors of ranks ranging from $1$ to $4$. The possible couplings are listed as well as their behavior under C, P, and T, allowing us to select the couplings compatible with electric-dipole-moment physics. The unsuppressed contributions of these couplings to the atom's hamiltonian can be read as equivalent to an electric dipole moment. The Lorentz-violating coefficients' magnitudes are limited using electric-dipole-moment measurements at the levels of $3.2\times 10^{-31}{\text{(eV)}}^{-2}$ or $1.6\times 10^{-33}{\text{(eV)}}^{-2}$.

   hep-ph1 citation
9. 09*

   Parametrized leptogenesis from linear seesaw

   Pei-Hong Gu🇨🇳

   We present a purely linear seesaw mechanism in a left-right symmetric framework and then realize a novel leptogenesis scenario for parametrizing the cosmic baryon asymmetty by the charged lepton masses and the light Majorana neutrino mass matrix up to an overall factor. Through the same Yukawa couplings, the lepton-number-conserving decays of the mirror charged leptons can generate three individual lepton asymmetries stored in the ordinary lepton flavors, while the lepton-number-violating processes for the Majorana neutrino mass generation can wash out part of these lepton asymmetries. The remnant lepton asymmetries then can be partially converted to a baryon asymmetry by the sphaleron processes. Our scenario prefers a normal hierarchical neutrino spectrum so that it could be verified by the future data from cosmological observations, neutrino oscillations and neutrinoless double beta decay.

   hep-phEPJC(2020)·1 citation
10. 10*

    Baryon asymmetry from left-right phase transition

    Pei-Hong Gu🇨🇳

    We extend the standard model fermions by a mirror copy to realize a left-right symmetry. During a strongly first order phase transition of the spontaneous left-right symmetry breaking, the CP-violating reflections of the mirror fermions off the mirror Higgs bubbles can generate a mirror lepton asymmetry and an equal mirror baryon asymmetry. We then can obtain an ordinary baryon asymmetry through the mirror fermion decays where a dark matter scalar plays an essential role. Benefitted from a parity symmetry for solving the strong CP problem, the cosmic baryon asymmetry can be well described by the ordinary lepton mass matrices up to an overall factor. In this scenario, the Dirac CP phase in the Majorana neutrino mass matrix can provide a unique source for the required CP violation. Furthermore, the Higgs triplet for type-II seesaw as well as the first generation of mirror charged fermions can be allowed at the TeV scale.

    hep-ph1 citation
11. 11*

    A Supersymmetric Theory of Baryogenesis and Sterile Sneutrino Dark Matter from $B$ Mesons

    Gonzalo Alonso-Álvarez🇩🇪 · Gilly Elor🇺🇸 · Ann E. Nelson🇺🇸 · Huangyu Xiao🇺🇸

    Low-scale baryogenesis and dark matter generation can occur via the production of neutral $B$ mesons at MeV temperatures in the early Universe, which undergo CP-violating oscillations and subsequently decay into a dark sector. In this work, we discuss the consequences of realizing this mechanism in a supersymmetric model with an unbroken $U(1{)}_R$ symmetry which is identified with baryon number. $B$ mesons decay into a dark sector through a baryon number conserving operator mediated by TeV scale squarks and a GeV scale Dirac bino. The dark sector particles can be identified with sterile neutrinos and their superpartners in a type-I seesaw framework for neutrino masses. The sterile sneutrinos are sufficiently long lived and constitute the dark matter. The produced matter-antimatter asymmetry is directly related to observables measurable at $B$ factories and hadron colliders, the most relevant of which are the semileptonic-leptonic asymmetries in neutral $B$ meson systems and the inclusive branching fraction of $B$ mesons into hadrons and missing energy. We discuss model independent constraints on these experimental observables before quoting predictions made in the supersymmetric context. Constraints from astrophysics, neutrino physics and flavor observables are studied, as are potential LHC signals with a focus on novel long lived particle searches which are directly linked to properties of the dark sector.

    hep-phastro-ph.COhep-exJHEP(2020)·42 citations
12. 12*

    (Not as) Big as a Barn: Upper Bounds on Dark Matter-Nucleus Cross Sections

    Matthew C. Digman🇺🇸 · Christopher V. Cappiello🇺🇸 · John F. Beacom🇺🇸 · Christopher M. Hirata🇺🇸 · Annika H. G. Peter🇺🇸

    Critical probes of dark matter come from tests of its elastic scattering with nuclei. The results are typically assumed to be model-independent, meaning that the form of the potential need not be specified and that the cross sections on different nuclear targets can be simply related to the cross section on nucleons. For point-like spin-independent scattering, the assumed scaling relation is ${\sigma }_{\chi A}\propto A^2{\mu }_A^2{\sigma }_{\chi N}\propto A^4{\sigma }_{\chi N}$, where the $A^2$ comes from coherence and the ${\mu }_A^2\simeq A^2{m}_N^2$ from kinematics for $m_{\chi }\gg m_A$. Here we calculate where model independence ends, i.e., where the cross section becomes so large that it violates its defining assumptions. We show that the assumed scaling relations generically fail for dark matter-nucleus cross sections ${\sigma }_{\chi A}\sim 10^{-32}-10^{-27}{\text{cm}}^2$, significantly below the geometric sizes of nuclei, and well within the regime probed by underground detectors. Last, we show on theoretical grounds, and in light of existing limits on light mediators, that point-like dark matter cannot have ${\sigma }_{\chi N}\gtrsim 10^{-25}{\text{cm}}^2$, above which many claimed constraints originate from cosmology and astrophysics. The most viable way to have such large cross sections is composite dark matter, which introduces significant additional model dependence through the choice of form factor. All prior limits on dark matter with cross sections ${\sigma }_{\chi N}>10^{-32}{\text{cm}}^2$ with $m_{\chi }\gtrsim 1\text{GeV}$ must therefore be re-evaluated and reinterpreted.

    hep-phastro-ph.COnucl-thPRD(2019)·92 citations
13. 13*

    The electro-weak couplings of the top and bottom quarks -- global fit and future prospects

    Gauthier Durieux🇮🇱 · Adrian Irles🇫🇷 · Víctor Miralles🇪🇸 · Ana Peñuelas🇪🇸 · Roman Pöschl🇫🇷 · Martín Perelló🇪🇸 · Marcel Vos🇪🇸

    We evaluate the implications of LHC and LEP/SLC measurements for the electro-weak couplings of the top and bottom quarks. We derive global bounds on the Wilson coefficients of ten two-fermion operators in an effective field theory description. The combination of hadron collider data with $Z$-pole measurements is found to yield tight limits on the operator coefficients that modify the left-handed couplings of the bottom and top quark to the $Z$ boson. We also present projections for the high-luminosity phase of the LHC and for future electron-positron colliders. The bounds on the operator coefficients are expected to improve substantially during the remaining LHC programme, by factors of $1$ to $5$ if systematic uncertainties are scaled as statistical ones. The operation of an $e^{+}{e}^{-}$ collider at a center-of-mass energy above the top-quark pair production threshold is expected to further improve the bounds by one to two orders of magnitude. The combination of measurements in $pp$ and $e^{+}{e}^{-}$ collisions allows for a percent-level determination of the top-quark Yukawa coupling, that is robust in a global fit.

    hep-phJHEP(2019)·122 citations
14. 14*

    MadMiner: Machine learning-based inference for particle physics

    Johann Brehmer🇺🇸 · Felix Kling🇺🇸 · Irina Espejo🇺🇸 · Kyle Cranmer🇺🇸

    Precision measurements at the LHC often require analyzing high-dimensional event data for subtle kinematic signatures, which is challenging for established analysis methods. Recently, a powerful family of multivariate inference techniques that leverage both matrix element information and machine learning has been developed. This approach neither requires the reduction of high-dimensional data to summary statistics nor any simplifications to the underlying physics or detector response. In this paper we introduce MadMiner, a Python module that streamlines the steps involved in this procedure. Wrapping around MadGraph5_aMC and Pythia 8, it supports almost any physics process and model. To aid phenomenological studies, the tool also wraps around Delphes 3, though it is extendable to a full Geant4-based detector simulation. We demonstrate the use of MadMiner in an example analysis of dimension-six operators in ttH production, finding that the new techniques substantially increase the sensitivity to new physics.

    hep-phhep-exphysics.data-anstat.MLComput.Softw.Big Sci.(2020)·147 citations
15. 15*

    Searches for other vacua II: A new Higgstory at the cosmological collider

    Anson Hook🇺🇸 · Junwu Huang🇨🇦 · Davide Racco🇨🇦

    The detection of an oscillating pattern in the bispectrum of density perturbations could suggest the existence of a high-energy second minimum in the Higgs potential. If the Higgs field resided in this new minimum during inflation and was brought back to the electroweak vacuum by thermal corrections during reheating, the coupling of Standard Model particles to the inflaton would leave its imprint on the bispectrum. We focus on the fermions, whose dispersion relation can be modified by the coupling to the inflaton, leading to an enhanced particle production during inflation even if their mass during inflation is larger than the Hubble scale. This results in a large non-analytic contribution to non-Gaussianities, with an amplitude $f_{\mathrm{NL}}$ as large as $100$ in the squeezed limit, potentially detectable in future 21-cm surveys. Measuring the contributions from two fermions would allow us to compute the ratio of their masses, and to ascribe the origin of the signal to a new Higgs minimum. Such a discovery would be a tremendous step towards understanding the vacuum instability of the Higgs potential, and could have fascinating implications for anthropic considerations.

    hep-phastro-ph.COhep-thJHEP(2020)·113 citations
16. 16*

    Dark Sectors from the Hidden Photon Perspective

    Patrick Foldenauer🇩🇪

    The non-observation of dark matter (DM) by direct detection experiments suggests that any new interaction of DM with the Standard Model (SM) should be very weak. One of the simplest scenarios to achieve this is a dark sector that is charged under a new $U(1{)}_X$ symmetry, which is kinetically mixed with the SM hypercharge $U(1{)}_Y$. We briefly review the status of such a minimal setup and analyze in a second step how the picture is altered if also SM fields are charged under the new symmetry. We exemplify this for the case of a gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ and show that this allows for a simultaneous explanation of the $(g-2{)}_{\mu }$ excess and the DM relic abundance ${\Omega }_{DM}$. Furthermore, we discuss the potential of four-lepton and two-lepton plus missing energy signatures to test such scenarios.

    hep-phhep-exPoS(2019)·8 citations
17. 17*

    Thermal Dark Energy

    Edward Hardy🇬🇧 · Susha Parameswaran🇬🇧

    We present a novel source of dark energy, which is motivated by the prevalence of hidden sectors in string theory models and is consistent with all of the proposed swampland conjectures. Thermal effects hold a light hidden sector scalar at a point in field space that is not a minimum of its zero temperature potential. This leads to an effective "cosmological constant", with an equation of state $w=-1$, despite the scalar's zero temperature potential having only a 4D Minkowski or AdS vacuum. For scalar masses $\lesssim \mu$eV, which could be technically natural via sequestering, there are large regions of phenomenologically viable parameter space such that the induced vacuum energy matches the measured dark energy density. Additionally, in many models a standard cosmological history automatically leads to the scalar having the required initial conditions. We study the possible observational signals of such a model, including at fifth force experiments and through $\Delta N_{\mathrm{eff}}$ measurements. Similar dynamics that are active at earlier times could resolve the tension between different measurements of $H_0$ and can lead to a detectable stochastic gravitational wave background.

    ↳ hep-thhep-phPRD(2020)·24 citations
18. 18*

    The theta-dependent Yang-Mills theory at finite temperature in a holographic description

    Si-wen Li🇨🇳

    The theta-dependent gauge theories can be studied by using holographic duality through string theory on certain spacetimes. Via this correspondence we consider a stack of $N_0$ dynamical D0-branes as D-instantons in the background sourced by $N_c$ coincident non-extreme black D4-branes. According to the gauge-gravity duality this D0-D4 brane system corresponds to Yang-Mills theory with a theta angle at finite temperature. We solve the IIA supergravity action by taking account into a sufficiently small backreaction of the D-instantons and obtain an analytical solution for our D0-D4-brane configuration. Then the dual theory in the large $N_c$ limit can be holographically investigated with the gravity solution. In the dual field theory, we find the coupling constant exhibits the property of asymptotic freedom as it is expected in QCD. The contribution of the theta-dependence to the free energy gets suppressed at high temperature which is basically consistent with the calculation by using the Yang-Mills instanton. The topological susceptibility in the large $N_c$ limit vanishes and this behavior remarkably agrees with the implications from the simulation results at finite temperature. Besides we finally find a geometrical interpretation of the theta-dependence in this holographic system.

    ↳ hep-thhep-phCPC(2020)·7 citations
19. 19*

    Constraining the gauge-fixed Lagrangian in minimal Landau gauge

    Axel Maas🇦🇹

    A continuum formulation of gauge-fixing resolving the Gribov-Singer ambiguity remains a challenge. Finding a Lagrangian formulation of operational resolutions in numerical lattice calculations, like minimal Landau gauge, would be one possibility. Such a formulation will here be constrained by reconstructing the Dyson-Schwinger equation for which the lattice minimal-Landau-gauge ghost propagator is a solution. It is found that this requires an additional term. As a by-product new, high precision lattice results for the ghost-gluon vertex in three and four dimensions are obtained.

    ↳ hep-lathep-phSciPost Phys.(2020)·26 citations
20. 20*

    Backreaction of electromagnetic fields and the Schwinger effect in pseudoscalar inflation magnetogenesis

    O.O. Sobol🇨🇭 · E.V. Gorbar🇺🇦 · S.I. Vilchinskii🇺🇦

    We study magnetogenesis in axionlike inflation driven by a pseudoscalar field $\varphi$ coupled axially to the electromagnetic (EM) field $(\beta /M_p)\varphi F_{\mu \nu }{\tilde{F}}^{\mu \nu }$ with dimensionless coupling constant $\beta$. A set of equations for the inflaton field, scale factor, and expectation values of quadratic functions of the EM field is derived. These equations take into account the Schwinger effect and the backreaction of generated EM fields on the Universe expansion. It is found that the backreaction becomes important when the EM energy density reaches the value ${\rho }_{\mathrm{EM}}\sim (\sqrt{2ϵ}/\beta ){\rho }_{\inf }$ ($ϵ$ is the slow-roll parameter and ${\rho }_{\inf }$ is the energy density of the inflaton) slowing down the inflaton rolling and terminating magnetogenesis. The Schwinger effect becomes relevant when the electric energy density exceeds the value ${\rho }_E\sim {\alpha }_{\mathrm{EM}}^{-3}({\rho }_{\mathrm{tot}}^2/M_p^4)$, where ${\rho }_{\mathrm{tot}}=3H^2{M}_p^2$ is the total energy density and ${\alpha }_{\mathrm{EM}}$ is the EM coupling constant. For large $\beta$, produced charged particles could constitute a significant part of the Universe energy density even before the preheating stage. Numerically studying magnetogenesis in the $\alpha$-attractor model of inflation, we find that it is possible to generate helical magnetic fields with the maximal strength $10^{-15}\mathrm{G}$, however, only with the correlation length of order $1\mathrm{pc}$ at present.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·93 citations
21. 21*

    Gauge field and brane-localized kinetic terms on the chiral square

    Ricardo G. Landim🇩🇪

    Extra dimensions have been used as attempts to explain several phenomena in particle physics. In this paper we investigate the role of brane-localized kinetic terms (BLKT) on thin and thick branes with two flat extra dimensions (ED) compactified on the chiral square, and an abelian gauge field in the bulk. The results for a thin brane have resemblance with the 5-D case, leading to a tower of massive KK particles whose masses depend upon the compactification radius and the BLKT parameter. On the other hand, for the thick brane scenario, there is no solution that satisfy the boundary conditions. Because of this, the mechanism of suppressed couplings due to ED [1902.08339] cannot be extended to 6-D.

    ↳ hep-thhep-phEPJC(2019)·7 citations
22. 22*

    Entropy Constraints on High Spin Particles

    Markus Dierigl🇳🇱 · Gia Dvali🇩🇪

    Elementary particles of large spin $s$ store quantum information in degenerate states and therefore are subject to the Bekenstein entropy bound. We observe that for sufficiently large $s$ the bound is violated unless the particle acquires a new associated length-scale different from its Compton wavelength. This can be regarded as a glimpse of stringiness. Moreover, this bound is independent of gravity. The inclusion of gravity additionally generates a new scale at which the thermality of the black hole radiation is violated by the emission of a high spin particle. This bound can be understood as the black hole species bound, i.e. an induced quantum gravity cutoff-scale given by $M_P/\sqrt{s}$. The two bounds carry qualitatively different information.

    ↳ hep-thgr-qchep-phquant-ph1 citation
23. 23*

    Fast Extragalactic X-ray Transients From Binary Neutron Star Mergers

    Shlomo Dado🇮🇱 · Arnon Dar🇮🇱

    The observed light curves and other properties of the two extragalactic fast x-ray transients, CDF-S XT1 and CDF-S XT2, which were discovered recently in archival data of the Chandra Deep Field-South (CDF-S) observations, indicate that they belong to two different populations of X-ray transients. XT1 seems to be an x-ray flash (XRF), i.e., a narrowly beamed long duration gamma ray burst viewed from far off-axis while XT2 seems to be a nebular emission powered by a newly born millisecond pulsar in a neutron stars binary merger.

    ↳ astro-ph.HEhep-phPRD(2020)·8 citations
24. 24*

    Gravitational wave probes of dark matter: challenges and opportunities

    Gianfranco Bertone🇳🇱 · Djuna Croon🇨🇦 · Mustafa A. Amin🇺🇸 · Kimberly K. Boddy🇺🇸 · Bradley J. Kavanagh🇳🇱 · Katherine J. Mack🇺🇸 · Priyamvada Natarajan🇺🇸 · Toby Opferkuch🇨🇭 · Katelin Schutz🇺🇸 · Volodymyr Takhistov🇺🇸 · Christoph Weniger🇳🇱 · Tien-Tien Yu🇺🇸

    In this white paper, we discuss the prospects for characterizing and identifying dark matter using gravitational waves, covering a wide range of dark matter candidate types and signals. We argue that present and upcoming gravitational wave probes offer unprecedented opportunities for unraveling the nature of dark matter and we identify the most urgent challenges and open problems with the aim of encouraging a strong community effort at the interface between these two exciting fields of research.

    ↳ astro-ph.COgr-qchep-phSciPost Phys.Core(2020)·173 citations
25. 25*

    Analytic Description of Primordial Black Hole Formation from Scalar Field Fragmentation

    Eric Cotner🇺🇸 · Alexander Kusenko🇺🇸 · Misao Sasaki🇯🇵 · Volodymyr Takhistov🇺🇸

    Primordial black hole (PBH) formation is a more generic phenomenon than was once thought. The dynamics of a scalar field in inflationary universe can produce PBHs under mild assumptions regarding the scalar potential. In the early universe, light scalar fields develop large expectation values during inflation and subsequently relax to the minimum of the effective potential at a later time. During the relaxation process, an initially homogeneous scalar condensate can fragment into lumps via an instability similar to the gravitational (Jeans) instability, where the scalar self-interactions, rather than gravity, play the leading role. The fragmentation of the scalar field into lumps (e.g. Q-balls or oscillons) creates matter composed of relatively few heavy "particles", whose distribution is subject to significant fluctuations unconstrained by comic microwave background (CMB) observations and unrelated to the large-scale structure. If this matter component comes to temporarily dominate the energy density before the scalar lumps decay, PBHs can be efficiently produced during the temporary matter-dominated era. We develop a general analytic framework for description of PBH formation in this class of models. We highlight the differences between the scalar fragmentation scenario and other commonly considered PBH formation models. Given the existence of the Higgs field and the preponderance of scalar fields within supersymmetric and other models of new physics, PBHs constitute an appealing and plausible candidate for dark matter.

    ↳ astro-ph.COhep-phhep-thJCAP(2019)·194 citations
26. 26*

    Tensions between the Early and the Late Universe

    L. Verde (1)🇪🇸 · T. Treu (2)🇺🇸 · A.G. Riess (3,4) ((1) ICREA & ICC UB, University of Barcelona, (2) UCLA, (3) JHU, (4) STScI)🇺🇸

    The standard cosmological model successfully describes many observations from widely different epochs of the Universe, from primordial nucleosynthesis to the accelerating expansion of the present day. However, as the basic cosmological parameters of the model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. The workshop "Tensions between the Early and the Late Universe" was held at the Kavli Institute for Theoretical Physics on July 15-17 2019 (More details of the workshop (including on-line presentations) are given at the website: https://www.kitp.ucsb.edu/activities/enervac-c19) to evaluate increasing evidence for these discrepancies, primarily in the value of the Hubble constant as well as ideas recently proposed to explain this tension. Multiple new observational results for the Hubble constant were presented in the time frame of the workshop using different probes: Cepheids, strong lensing time delays, tip of the red giant branch (TRGB), megamasers, Oxygen-rich Miras and surface brightness fluctuations (SBF) resulting in a set of six new ones in the last several months. Here we present the summary plot of the meeting that shows combining any three independent approaches to measure H${}_0$ in the late universe yields tension with the early Universe values between 4.0$\sigma$ and 5.8$\sigma$. This shows that the discrepancy does not appear to be dependent on the use of any one method, team, or source. Theoretical ideas to explain the discrepancy focused on new physics in the decade of expansion preceding recombination as the most plausible. This is a brief summary of the workshop.

    ↳ astro-ph.COgr-qchep-phhep-thNature Astron.(2019)·1467 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.