Wed·Aug 1, 2018Wednesday·August 1, 2018

1. 01*

   Electroweak Corrections to Higgs to $\gamma \gamma$ and $W^{+}{W}^{-}$ in the SMEFT

   Sally Dawson🇺🇸 · Pier Paolo Giardino🇺🇸

   Higgs decays to gauge boson pairs are a crucial ingredient in the study of Higgs properties, with the decay $H\to \gamma \gamma$ being particularly sensitive to new physics effects. Assuming all potential new physics occurs at energies much above the weak scale, deviations from Standard Model predictions can be parameterized in terms of the coefficients of an effective field theory (SMEFT). When experimental limits on the SMEFT coefficients reach an accuracy of a few percent, predictions must be done beyond the lowest order in the SMEFT in order to match theory and experimental accuracy. This paper completes a program of computing the one-loop electroweak SMEFT corrections to $H\to V{V}^{\prime }$, $V=W^{\pm },Z,\gamma$. The calculation of the real contribution to $H\to W^{+}{W}^{-}\gamma$ is performed by mapping two-loop amplitudes to the $3-$ body phase space.

   hep-phPRD(2018)·79 citations
2. 02*

   The Serendipity of Electroweak Baryogenesis

   Geraldine Servant🇩🇪

   The origin of the matter antimatter asymmetry of the universe remains unexplained in the Standard Model of particle physics. The origin of the flavour structure is another major puzzle of the theory. In this article, we report on recent work attempting to link the two themes through the appealing framework of electroweak baryogenesis. We show that Yukawa couplings of Standard Model fermions can be the source of CP-violation for electroweak baryogenesis if they vary at the same time as the Higgs is acquiring its vacuum expectation value, offering new avenues for electroweak baryogenesis. The advantage of this approach is that it circumvents the usual severe bounds from Electric Dipole moments. These ideas apply if the mechanism explaining the flavour structure of the Standard Model is connected to electroweak symmetry breaking, as motivated for instance in Randall-Sundrum or Composite Higgs models. We compute the resulting baryon asymmetry for different configurations of the Yukawa coupling variation across the bubble wall, and show that it can naturally be of the right order.

   hep-phPhil.Trans.Roy.Soc.Lond.A(2018)·22 citations
3. 03*

   Consequences of Fine-Tuning for Fifth Force Searches

   Nikita Blinov🇺🇸 · Sebastian A. R. Ellis🇺🇸 · Anson Hook🇺🇸

   Light bosonic fields mediate long range forces between objects. If these fields have self-interactions, i.e., non-quadratic terms in the potential, the experimental constraints on such forces can be drastically altered due to a screening (chameleon) or enhancement effect. We explore how technically natural values for such self-interaction coupling constants modify the existing constraints. We point out that assuming the existence of these natural interactions leads to new constraints, contrary to the usual expectation that screening leads to gaps in coverage. We discuss how screening can turn fundamentally equivalence principle (EP)-preserving forces into EP-violating ones. This means that when natural screening is present, searches for EP violation can be used to constrain EP-preserving forces. We show how this effect enables the recently discovered stellar triple system \textit{PSR J0337$+$1715} to place a powerful constraint on EP-preserving fifth forces. Finally, we demonstrate that technically natural cubic self-interactions modify the vacuum structure of the scalar potential, leading to new constraints from spontaneous and induced vacuum decay.

   hep-phastro-ph.COgr-qchep-thJHEP(2018)·15 citations
4. 04*

   Custodial symmetry violation in the Georgi-Machacek model

   Ben Keeshan🇨🇦 · Heather E. Logan🇨🇦 · Terry Pilkington (Carleton U.)🇨🇦

   We study the effects of custodial symmetry violation in the Georgi-Machacek (GM) model. The GM model adds isospin-triplet scalars to the Standard Model in a way that preserves custodial symmetry at tree level; however, this custodial symmetry has long been known to be violated at the one-loop level by hypercharge interactions. We consider the custodial-symmetric GM model to arise at some high scale as a result of an unspecified ultraviolet completion, and quantify the custodial symmetry violation induced as the model is run down to the weak scale. The measured value of the eletroweak rho parameter (along with unitarity considerations) lets us constrain the scale of the ultraviolet completion to lie below tens to hundreds of TeV. Subject to this constraint, we quantify the size of other custodial-symmetry-violating effects at the weak scale, including custodial symmetry violation in the couplings of the 125 GeV Higgs boson to W and Z boson pairs and mixings and mass splittings among the additional Higgs bosons in the theory. We find that these effects are small enough that they are unlikely to be probed by the Large Hadron Collider, but may be detectable at a future $e^{+}{e}^{-}$ collider.

   hep-phPRD(2020)·31 citations
5. 05*

   Fermionic spectral functions with the Functional Renormalization Group

   Ralf-Arno Tripolt🇮🇹 · Johannes Weyrich🇩🇪 · Lorenz von Smekal🇩🇪 · Jochen Wambach🇮🇹

   We present first results on the calculation of fermionic spectral functions from analytically continued flow equations within the Functional Renormalization Group approach. Our method is based on the same analytic continuation from imaginary to real frequencies that was developed and used previously for bosonic spectral functions. In order to demonstrate the applicability of the method also for fermionic correlations we apply it here to the real-time quark propagator in the quark-meson model and calculate the corresponding quark spectral functions in the vacuum.

   hep-phhep-thnucl-thPRD(2018)·32 citations
6. 06*

   Direct Detection of Axion-Like Particles in Bismuth-Based Topological Insulators

   Tairan Liang🇨🇳 · Bin Zhu🇨🇳 · Ran Ding🇨🇳 · Tianjun Li🇨🇳

   In recent years a new field emerged in dark matter community and immediately attracted a multitude of theoriests and experimentalists, that of light dark matter direct detection in electronic systems. The phenomenon is similar with nuclear recoil in elastic scattering between dark matter and nucleus but with different kinematics. Due to the small energy gap, the electronic system can probe sub-GeV dark matter rather than nucleus target. In particular the absorption into materials can even detect ultra-light dark matter within mass around meV. In terms of the equivalence between optical conductivity and absorption cross section, axion detection can be computed in Bismuth-based topological insulators. It is found that topological insulator has strong sensitivity on axion and provides a complementary direct detection to superconductor and semiconductors. The novelty of topological insulator is that the thin film could even obtain the same sensitivity as superconductor.

   hep-phInt.J.Mod.Phys.A(2018)·5 citations
7. 07*

   Higher order and top mass effects in Higgs boson pair production beyond the Standard Model

   Gerhard Buchalla🇩🇪 · Alejandro Celis🇩🇪 · Matteo Capozi🇩🇪 · Gudrun Heinrich🇩🇪 · Ludovic Scyboz🇩🇪

   We discuss the interplay between NLO QCD corrections and anomalous couplings in Higgs boson pair production via gluon fusion, within the framework of a non-linearly realised Effective Field Theory, described by the electroweak chiral Lagrangian. We study how the NLO corrections with full top quark mass dependence affect the total cross sections as well as distributions in the Higgs boson pair invariant mass. For a large part of the parameter space, significant and non-homogeneous K-factors arise.

   hep-phPoS(2018)·0 citations
8. 08*

   Signatures of the genuine and matter-induced components of the CP violation asymmetry in neutrino oscillations

   J. Bernabeu🇪🇸 · A. Segarra🇪🇸

   CP asymmetries for neutrino oscillations in matter can be disentangled into the matter-induced CPT-odd (T-invariant) component and the genuine T-odd (CPT-invariant) component. For their understanding in terms of the relevant ingredients, we develop a new perturbative expansion in both $\Delta m_{21}^2,|a|\ll |\Delta m_{31}^2|$ without any assumptions between $\Delta m_{21}^2$ and $a$, and study the subtleties of the vacuum limit in the two terms of the CP asymmetry, moving from the CPT-invariant vacuum limit $a\to 0$ to the T-invariant limit $\Delta m_{21}^2\to 0$. In the experimental region of terrestrial accelerator neutrinos, we calculate their approximate expressions from which we prove that, at medium baselines, the CPT-odd component is small and nearly $\delta$-independent, so it can be subtracted from the experimental CP asymmetry as a theoretical background, provided the hierarchy is known. At long baselines, on the other hand, we find that (i) a Hierarchy-odd term in the CPT-odd component dominates the CP asymmetry for energies above the first oscillation node, and (ii) the CPT-odd term vanishes, independent of the CP phase $\delta$, at $E=0.92\mathrm{GeV}(L/1300\mathrm{km})$ near the second oscillation maximum, where the T-odd term is almost maximal and proportional to $\sin \delta$. A measurement of the CP asymmetry in these energy regions would thus provide separate information on (i) the neutrino mass ordering, and (ii) direct evidence of genuine CP violation in the lepton sector.

   hep-phJHEP(2018)·20 citations
9. 09*

   Dispersive analysis of $\eta \to 3\pi$

   Gilberto Colangelo🇨🇭 · Stefan Lanz🇨🇭 · Heinrich Leutwyler🇨🇭 · Emilie Passemar🇺🇸

   The dispersive analysis of the decay $\eta \to 3\pi$ is reviewed and thoroughly updated with the aim of determining the quark mass ratio ~$Q^2=(m_s^2-m_{ud}^2)/(m_d^2-m_u^2)$. With the number of subtractions we are using, the effects generated by the final state interaction are dominated by low energy $\pi \pi$ scattering. Since the corresponding phase shifts are now accurately known, causality and unitarity determine the decay amplitude within small uncertainties -- except for the values of the subtraction constants. Our determination of these constants relies on the Dalitz plot distribution of the charged channel, which is now measured with good accuracy. The theoretical constraints that follow from the fact that the particles involved in the transition represent Nambu-Goldstone bosons of a hidden approximate symmetry play an equally important role. The ensuing predictions for the Dalitz plot distribution of the neutral channel and for the branching ratio ${\Gamma }_{\eta \to 3{\pi }^0}/{\Gamma }_{\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0}$ are in very good agreement with experiment. Relying on a known low-energy theorem that relates the meson masses to the masses of the three lightest quarks, our analysis leads to $Q=22.1(7)$, where the error covers all of the uncertainties encountered in the course of the calculation: experimental uncertainties in decay rates and Dalitz plot distributions, noise in the input used for the phase shifts, as well as theoretical uncertainties in the constraints imposed by chiral symmetry and in the evaluation of isospin breaking effects. Our result indicates that the current algebra formulae for the meson masses only receive small corrections from higher orders of the chiral expansion, but not all of the recent lattice results are consistent with this conclusion.

   hep-phhep-latEPJC(2018)·95 citations
10. 10*

    Positivity bounds on vector boson scattering at the LHC

    Cen Zhang🇨🇳 · Shuang-Yong Zhou🇨🇳

    Weak vector boson scattering (VBS) is a sensitive probe of new physics effects in the electroweak symmetry breaking. Currently, experimental results at the LHC are interpreted in the effective field theory approach, where possible deviations from the Standard Model in the quartic-gauge-boson couplings are often described by 18 dimension-8 operators. By assuming that a UV completion exists, we derive a new set of theoretical constraints on the coefficients of these operators, i.e. certain combinations of coefficients must be positive. These constraints imply that the current effective approach to VBS has a large redundancy: only about $2\%$ of the full parameter space leads to a UV completion. By excluding the remaining unphysical region of the parameter space, these constraints provide guidance for future VBS studies and measurements.

    hep-phhep-exhep-thPRD(2019)·136 citations
11. 11*

    Proof of NRQCD Color Octet Factorization of P-Wave Heavy Quarkonium Production In Non-Equilibrium QCD at RHIC and LHC

    Gouranga C Nayak🇺🇸

    Recently we have proved NRQCD color octet factorization of S-wave and P-wave heavy quarkonia production at all orders in coupling constant in QCD in vacuum at high energy colliders in Eur. Phys. J. C76 (2016) 448 and in arXiv:1807.04722 [hep-ph] respectively. In this paper we extend this to prove NRQCD color octet factorization of P-wave heavy quarkonium production in non-equilibrium QCD at RHIC and LHC at all orders in coupling constant. This proof is necessary to study the quark-gluon plasma at RHIC and LHC.

    hep-phnucl-th2 citations
12. 12*

    Walking, Weak first-order transitions, and Complex CFTs

    Victor Gorbenko🇺🇸 · Slava Rychkov🇫🇷 · Bernardo Zan🇫🇷

    We discuss walking behavior in gauge theories and weak first-order phase transitions in statistical physics. Despite appearing in very different systems (QCD below the conformal window, the Potts model, deconfined criticality) these two phenomena both imply approximate scale invariance in a range of energies and have the same RG interpretation: a flow passing between pairs of fixed point at complex coupling. We discuss what distinguishes a real theory from a complex theory and call these fixed points complex CFTs. By using conformal perturbation theory we show how observables of the walking theory are computable by perturbing the complex CFTs. This paper discusses the general mechanism while a companion paper [1] will treat a specific and computable example: the two-dimensional Q-state Potts model with Q > 4. Concerning walking in 4d gauge theories, we also comment on the (un)likelihood of the light pseudo-dilaton, and on non-minimal scenarios of the conformal window termination.

    ↳ hep-thcond-mat.stat-mechcond-mat.str-elhep-lat+1JHEP(2018)·279 citations
13. 13*

    Differential equations from unitarity cuts: nonplanar hexa-box integrals

    Samuel Abreu🇩🇪 · Ben Page🇩🇪 · Mao Zeng🇺🇸

    We compute $ϵ$-factorized differential equations for all dimensionally-regularized integrals of the nonplanar hexa-box topology, which contribute for instance to 2-loop 5-point QCD amplitudes. A full set of pure integrals is presented. For 5-point planar topologies, Gram determinants which vanish in $4$ dimensions are used to build compact expressions for pure integrals. Using unitarity cuts and computational algebraic geometry, we obtain a compact IBP system which can be solved in 8 hours on a single CPU core, overcoming a major bottleneck for deriving the differential equations. Alternatively, assuming prior knowledge of the alphabet of the nonplanar hexa-box, we reconstruct analytic differential equations from 30 numerical phase-space points, making the computation almost trivial with current techniques. We solve the differential equations to obtain the values of the master integrals at the symbol level. Full results for the differential equations and solutions are included as supplementary material.

    ↳ hep-thhep-phJHEP(2019)·71 citations
14. 14*

    Search for a Dark Photon in Electro-Produced $e^{+}{e}^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

    P. H. Adrian🇺🇸 · N. A. Baltzell🇺🇸 · M. Battaglieri🇮🇹 · M. Bondí🇮🇹 · S. Boyarinov🇺🇸 · S. Bueltmann🇺🇸 · V. D. Burkert🇺🇸 · D. Calvo🇮🇹 · M. Carpinelli🇮🇹 · A. Celentano🇮🇹 · G. Charles🇫🇷 · L. Colaneri🇮🇹 and 65 other authors

    The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}{e}^{-}$ invariant mass distribution, using 1.7 days (1170 nb${}^{-1}$) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times 10^{-6}$. Future runs with higher luminosity will explore new territory.

    ↳ hep-exhep-phPRD(2018)·79 citations
15. 15*

    Deep inelastic scattering from polarized spin-$1/2$ hadrons at low $x$ from string theory

    Nicolas Kovensky🇦🇷 · Gustavo Michalski🇦🇷 · Martin Schvellinger🇦🇷

    We study polarized deep inelastic scattering of charged leptons from spin-$1/2$ hadrons at low values of the Bjorken parameter and large 't Hooft coupling in terms of the gauge/string theory duality. We calculate the structure functions from type IIB superstring theory scattering amplitudes. We discuss the role of the non-Abelian Chern-Simons term and the Pauli term from the five-dimensional $SU(4)$ gauged supergravity. Furthermore, the exponentially small-$x$ regime where Regge physics becomes important is analyzed in detail for the antisymmetric structure functions. In this case the holographic dual picture of the Pomeron exchange is realized by a Reggeized gauge field. We compare our results with experimental data of the proton antisymmetric structure function $g_1$, obtaining a very good level of agreement.

    ↳ hep-thhep-exhep-phJHEP(2018)·24 citations
16. 16*

    Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications

    Qiang Yuan (PMO, USTC, PKU)🇨🇳 · Lei Feng (PMO)🇨🇳

    The DArk Matter Particle Explorer (DAMPE) is a satellite-borne, high-energy particle and $\gamma$-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals an interesting spectral softening around $0.9$ TeV and a tentative peak around $1.4$ TeV. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.

    ↳ astro-ph.HEhep-phSCPMA(2018)·39 citations
17. 17*

    QCD+QED lattice calculation of hadronic decay rates

    D. Giusti🇮🇹

    Isospin is an almost exact symmetry of strong interactions and the corrections to the isosymmetric limit are, in general, at the percent level. For several hadronic quantities relevant for flavour physics phenomenology, such as pseudoscalar meson masses or the kaon leptonic and semileptonic decay rates, these effects are of the same order of magnitude of the uncertainties quoted in current large-scale QCD simulations on the lattice and cannot be neglected anymore. In this contribution I discuss some recent results for the leptonic decay rates of light pseudoscalar mesons obtained by the Soton--RM123 Collaboration including the leading-order electromagnetic and strong isospin-breaking corrections in first principles lattice simulations. The adopted strategy is within the reach of present lattice technologies and it allows to determine electromagnetic corrections to physical observables for which delicate cancellations of infrared divergences occur in the intermediate steps of the calculation. The application of the developed method to the study of heavy-light meson and semileptonic decay rates is currently underway.

    ↳ hep-lathep-exhep-phNuovo Cim.C(2019)·2 citations
18. 18*

    Boltzmann equations for preheating

    William T. Emond🇬🇧 · Peter Millington🇬🇧 · Paul M. Saffin🇬🇧

    We derive quantum Boltzmann equations for preheating by means of the density matrix formalism, which account for both the non-adiabatic particle production and the leading collisional processes between the produced particles. In so doing, we illustrate the pivotal role played by pair correlations in mediating the particle production. In addition, by numerically solving the relevant system of Boltzmann equations, we demonstrate that collisional processes lead to a suppression of the growth of the number density even at the very early stages of preheating.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2018)·8 citations
19. 19*

    SHiP: a new facility to search for long lived neutral particles and investigate the ${\nu }_{\tau }$ properties

    Elena Graverini🇨🇭

    SHIP is a new general purpose fixed target facility, whose Technical Proposal has been recently reviewed by the CERN SPS Committee and by the CERN Research Board. The two boards recommended that the experiment proceeds further to a Comprehensive Design phase. A 400 GeV proton beam extracted from the SPS will be dumped on a heavy target with the aim of integrating $2\times 10^{20}$ proton-target collisions (\textit{pot}) in 5 years. A dedicated detector, based on a long vacuum tank followed by a spectrometer and particle identification detectors, will allow to probe a variety of New Physics models with light long-lived exotic particles and masses below $\mathcal{O}(10)$~GeV/$c^2$, including Dark Photons, light scalars and pseudo-scalars, and Heavy Neutrinos. The sensitivity to Heavy Neutrinos will allow for the first time to probe, in the mass range between the $K$ and the $D$ meson mass, a coupling range for which Baryogenesis and neutrino oscillations could also be explained. Another dedicated detector will allow the study of neutrino cross-sections and angular distributions. ${\nu }_{\tau }$ deep inelastic scattering cross sections will be measured with a statistics 1000 times larger than currently available, with the extraction of the so far never measured $F_4$ and $F_5$ structure functions, and allow to perform charm physics studies with significantly improved accuracy.

    ↳ hep-exhep-phphysics.ins-det0 citations
20. 20*

    Strong, Random field behavior of the Euclidean Dirac propagator

    M. P. Fry🇮🇪

    The one-loop effective action of quantum electrodynamics in four dimensions is shown to be controlled by the Euclidean Dirac propagator $G$ in a background potential. After separating the photon self-energy and photon-photon scattering graphs from the effective action the remainder is known to be the logarithm of an entire function of the electric charge of order 4 under mild regularity assumptions on the potential. This input together with QED's lack of an ultrastable vacuum constrain the strong field behavior of $G$. It is shown that $G$ vanishes in the strong field limit. The relevance of this result to the decoupling of QED from the remainder of the electroweak model for large amplitude variations of the Maxwell field is discussed.

    ↳ hep-thhep-phPRD(2018)·1 citation
21. 21*

    Chiral Symmetry Breaking and Restoration in (2+1) Dimensions from Holography: Magnetic and Inverse Magnetic Catalysis

    Diego M. Rodrigues🇧🇷 · Danning Li🇨🇳 · Eduardo Folco Capossoli🇧🇷 · Henrique Boschi-Filho🇧🇷

    We study the chiral symmetry breaking and restoration in $(2+1)$-dimensional gauge theories from the holographic hard and softwall models. We describe the behavior of the chiral condensate in the presence of an external magnetic field for both models at finite temperature. For the hardwall model we find Magnetic Catalysis (MC) in different set ups. For the softwall model we find Inverse Magnetic Catalysis (IMC) and MC in different situations. We also find for the softwall model a crossover transition from IMC to MC at a pseudocritical magnetic field. This study also shows spontaneous symmetry breaking for both models. Interestingly, for $B=0$ in the softwall model we found a nontrivial expectation value for the chiral condensate.

    ↳ hep-thhep-phPRD(2018)·28 citations
22. 22*

    Towards the Theory of the Yukawa Potential

    J. C. del Valle🇲🇽 · D. J. Nader🇲🇽

    Using three different approaches, Perturbation Theory (PT), the Lagrange Mesh Method (Lag-Mesh) and the Variational Method (VM), we study the low-lying states of the Yukawa potential $V(r)=-(\lambda /r)e^{-\alpha r}$. First orders in PT in powers of $\alpha$ are calculated in the framework of the Non-Linerization Procedure. It is found that the Padé approximants to PT series together with the Lag-Mesh provide highly accurate values of the energy and the positions of the radial nodes of the wave function. The most accurate results, at present, of the critical screening parameters (${\alpha }_c$) for some low-lying states and the first coefficients in the expansion of the energy at ${\alpha }_c$ are presented. A locally-accurate and compact approximation for the eigenfunctions of the low-lying states for any $r\in [0,\infty )$ is discovered. This approximation used as a trial function in VM eventually leads to energies as precise as those of PT and Lag-Mesh. Finally, a compact analytical expression for the energy as a function of $\alpha$, that reproduce at least $6$ decimal digits in the entire physical range of $\alpha$, is found.

    ↳ physics.comp-phhep-phJ.Math.Phys.(2018)·7 citations
23. 23*

    Eternal Inflation and Swampland Conjectures

    Hiroki Matsui🇯🇵 · Fuminobu Takahashi🇯🇵

    We study if eternal inflation is realized while satisfying the recently proposed string Swampland criteria concerning the range of scalar field excursion, $|\Delta \varphi |<\mathcal{D}\cdot M_{\mathrm{P}}$, and the potential gradient, $|\nabla V|>c\cdot V/M_{\mathrm{P}}$, where $\mathcal{D}$ and $c$ are constants of order unity, and $M_{\mathrm{P}}$ is the reduced Planck mass. We find that only the eternal inflation of chaotic type is possible for $c\sim \mathcal{O}(0.01)$ and $1/\mathcal{D}\sim \mathcal{O}(0.01)$, and that the Hubble parameter during the eternal inflation is parametrically close to the Planck scale, and is in the range of $2\pi c\lesssim H_{\inf }/M_{\mathrm{P}}<1/\sqrt{3}$.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·100 citations
24. 24*

    Dai-Freed anomalies in particle physics

    Iñaki García-Etxebarria🇩🇪 · Miguel Montero🇳🇱

    Anomalies can be elegantly analyzed by means of the Dai-Freed theorem. In this framework it is natural to consider a refinement of traditional anomaly cancellation conditions, which sometimes leads to nontrivial extra constraints in the fermion spectrum. We analyze these more refined anomaly cancellation conditions in a variety of theories of physical interest, including the Standard Model and the $SU(5)$ and $Spin(10)$ GUTs, which we find to be anomaly free. Turning to discrete symmetries, we find that baryon triality has a ${\mathbb{Z}}_9$ anomaly that only cancels if the number of generations is a multiple of 3. Assuming the existence of certain anomaly-free ${\mathbb{Z}}_4$ symmetry we relate the fact that there are 16 fermions per generation of the Standard Model - including right-handed neutrinos - to anomalies under time-reversal of boundary states in four-dimensional topological superconductors. A similar relation exists for the MSSM, only this time involving the number of gauginos and Higgsinos, and it is non-trivially, and remarkably, satisfied for the $SU(3)\times SU(2)\times U(1)$ gauge group with two Higgs doublets. We relate the constraints we find to the well-known Ibañez-Ross ones, and discuss the dependence on UV data of the construction. Finally, we comment on the (non-)existence of K-theoretic $\theta$ angles in four dimensions.

    ↳ hep-thhep-phJHEP(2019)·209 citations
25. 25*

    Footprint of Two-Form Field: Statistical Anisotropy in Primordial Gravitational Waves

    Ippei Obata🇯🇵 · Tomohiro Fujita🇯🇵

    We study the observational signatures of two-form field in the inflationary cosmology. In our setup a two-form field is kinetically coupled to a spectator scalar field and generates sizable gravitational waves and smaller curvature perturbation. We find that the sourced gravitational waves have a distinct signature: they are always statistically anisotropic and their spherical moments are non-zero for hexadecapole and tetrahexacontapole, while the quadrupole moment vanishes. Since their amplitude can reach $\mathcal{O}(10^{-3})$ in the tensor-to-scalar ratio, we expect this novel prediction will be tested in the next generation of the CMB experiments.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2019)·28 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.