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  • 301. Fonda, Piermarco
    et al.
    Franti, Lasse
    Keraenen, Ville
    Keski-Vakkuri, Esko
    Thorlacius, Larus
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    Tonni, Erik
    Holographic thermalization with Lifshitz scaling and hyperscaling violation2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 8, s. 051-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Vaidya type geometry describing gravitation collapse in asymptotically Lifshitz spacetime with hyperscaling violation provides a simple holographic model for thermalization near a quantum critical point with non-trivial dynamic and hyperscaling violation exponents. The allowed parameter regions are constrained by requiring that the matter energy momentum tensor satisfies the null energy condition. We present a combination of analytic and numerical results on the time evolution of holographic entanglement entropy in such backgrounds for different shaped boundary regions and study various scaling regimes, generalizing previous work by Liu and Suh.

  • 302.
    Fontanella, Andrea
    et al.
    UAM, CSIC, Inst Fis Teor, C Nicolas Cabrera,13-15,CU Cantoblanco, E-28049 Madrid, Spain.
    Ohlsson Sax, Olof
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Stefański, Bogdan, Jr.
    Alessandro, Alessandro
    The effectiveness of relativistic invariance in AdS(3)2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 7, artikel-id 105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use relativistic invariance to investigate two aspects of integrable AdS(3) string theory. Firstly, we write down the all-loop TBA equations for the massless sector of the theory with R-R flux, using the recently discovered hidden relativistic symmetry. Secondly, for the low-energy relativistic limit of the theory with NS-NS flux we write down the S matrix, dressing factors and TBA. We find that the integrable system coincides with a restriction to AdS(3) of the relativistic q-deformed AdS(5) theory. We also comment on the relativistic limit of the small-k NS-NS theory.

  • 303.
    Freese, Katherine
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Lopez, Alejandro
    Shah, Nausheen R.
    Shakya, Bibhushan
    MSSM A-funnel and the galactic center excess: prospects for the LHC and direct detection experiments2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikel-id 059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The pseudoscalar resonance or "A-funnel" in the Minimal Supersymmetric Standard Model (MSSM) is a widely studied framework for explaining dark matter that can yield interesting indirect detection and collider signals. The well-known Galactic Center excess (GCE) at GeV energies in the gamma ray spectrum, consistent with annihilation of a less than or similar to 40 GeV dark matter particle, has more recently been shown to be compatible with significantly heavier masses following reanalysis of the background. In this paper, we explore the LHC and direct detection implications of interpreting the GCE in this extended mass window within the MSSM A-funnel framework. We find that compatibility with relic density, signal strength, collider constraints, and Higgs data can be simultaneously achieved with appropriate parameter choices. The compatible regions give very sharp predictions of 200-600 GeV CP-odd/even Higgs bosons at low tan beta at the LHC and spin-independent cross sections approximate to 10(-11) pb at direct detection experiments. Regardless of consistency with the GCE, this study serves as a useful template of the strong correlations between indirect, direct, and LHC signatures of the MSSM A-funnel region.

  • 304. G., Aad
    et al.
    Jovicevic, J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Kuwertz, E. S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, A. K.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et.al, .
    Search for new phenomena in events with three or more charged leptons in pp collisions at √s=8 TeV with the ATLASdetector2015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A generic search for anomalous production of events with at least three charged leptons is presented. The data sample consists of pp collisions at s=8" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">s√=8s=8 TeV collected in 2012 by the ATLAS experiment at the CERN Large Hadron Collider, and corresponds to an integrated luminosity of 20.3 fb−1. Events are required to have at least three selected lepton candidates, at least two of which must be electrons or muons, while the third may be a hadronically decaying tau. Selected events are categorized based on their lepton flavour content and signal regions are constructed using several kinematic variables of interest. No significant deviations from Standard Model predictions are observed. Model-independent upper limits on contributions from beyond the Standard Model phenomena are provided for each signal region, along with prescription to re-interpret the limits for any model. Constraints are also placed on models predicting doubly charged Higgs bosons and excited leptons. For doubly charged Higgs bosons decaying to  or μτ, lower limits on the mass are set at 400 GeV at 95% confidence level. For excited leptons, constraints are provided as functions of both the mass of the excited state and the compositeness scale Λ, with the strongest mass constraints arising in regions where the mass equals Λ. In such scenarios, lower mass limits are set at 3.0 TeV for excited electrons and muons, 2.5 TeV for excited taus, and 1.6 TeV for every excited-neutrino flavour.

  • 305. Garbrecht, Björn
    et al.
    Konstandin, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Hybrid inflation exit through tunneling2007Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, s. 033-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For hybrid inflationary potentials, we derive the tunneling rate from field configurations along the flat direction towards the waterfall regime. This process competes with the classically rolling evolution of the scalar fields and needs to be strongly subdominant for phenomenologically viable models. Tunneling may exclude models with a mass scale below 10(12) GeV, but can be suppressed by small values of the coupling constants. We find that tunneling is negligible for those models, which do not require fine tuning in order to cancel radiative corrections, in particular for GUT-scale SUSY inflation. In contrast, electroweak scale hybrid inflation is not viable, unless the inflaton-waterfall field coupling is smaller than approximately 10(-11).

  • 306. Girardi, Ivan
    et al.
    Meloni, Davide
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Zhang, He
    Zhou, Shun
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Constraining sterile neutrinos using reactor neutrino experiments2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experiment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle sin(2) 2 theta(14) less than or similar to 0.06 at 3 sigma confidence level for the mass-squared difference Delta m(41)(2) in the range (10(-3), 10(-1)) eV(2). The latter bound can be improved by six years of running of the JUNO experiment, sin(2) 2 theta(14) less than or similar to 0.016, although in the smaller mass range Delta m(41)(2) is an element of(10(-4), 10(-3)) eV(2). We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters theta(13) and Delta m(31)(2) (at Daya Bay and JUNO), theta(12) and Delta m(21)(2) (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where Delta m(41)(2) similar to Delta m(31)(2), sterile states do not affect these measurements substantially.

  • 307. Good, Michael R. R.
    et al.
    Ong, Yen Chin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University.
    Signatures of energy flux in particle production: a black hole birth cry and death gasp2015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 7, artikel-id 145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is recently argued that if the Hawking radiation process is unitary, then a black hole's mass cannot be monotonically decreasing. We examine the time dependent particle count and negative energy flux in the non-trivial conformal vacuum via the moving mirror approach. A new, exactly unitary solution is presented which emits a characteristic above-thermal positive energy burst, a thermal plateau, and negative energy flux. It is found that the characteristic positive energy flare and thermal plateau is observed in the particle outflow. However, the results of time dependent particle production show no overt indication of negative energy flux. Therefore, a black hole's birth cry is detectable by asymptotic observers via particle count, whereas its death gasp is not.

  • 308. Good, Michael R. R.
    et al.
    Yelshibekov, Khalykbek
    Ong, Yen Chin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    On horizonless temperature with an accelerating mirror2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 3, artikel-id 013Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new solution of a unitary moving mirror is found to produce finite energy and emit thermal radiation despite the absence of an acceleration horizon. In the limit that the mirror approaches the speed of light, the model corresponds to a black hole formed from the collapse of a null shell. For speeds less than light, the black hole correspondence, if it exists, is that of a remnant.

  • 309.
    Gordon, James
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Antisymmetric Wilson loops in N=4 SYM beyond the planar limit2018Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikel-id 107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the 1/2-BPS circular Wilson loop in the totally antisymmetric representation of the gauge group in N = 4 supersymmetric Yang-Mills. This observable is captured by a Gaussian matrix model with appropriate insertion. We compute the first 1/N correction at leading order in 't Hooft coupling by means of the matrix model loop equations. Disagreement with the 1-loop effective action of the holographically dual D5-brane suggests the need to account for gravitational backreaction on the string theory side.

  • 310.
    Gouteraux, Blaise
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stanford University, United States .
    Martin, Victoria L.
    Spectral weight and spatially modulated instabilities in holographic superfluids2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 5, artikel-id 005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Free fermions form a Fermi surface, which results in non-zero spectral weight at low energy and finite wavevector k(F). In this work, we find similar features in holographic phases dual to strongly coupled quantum superfluid matter. At zero temperature, the phases we consider exhibit semi-local criticality in the IR and all the charge is carried by the scalar condensate outside the black hole horizon. Depending on the value taken by the IR critical exponents, we find Fermi surfaces in the transverse sector, Fermi shells in the longitudinal sector or no spectral weight at all. When there is non-zero transverse spectral weight, the IR can be subject to an instability at finite wavevector, the endpoint of which is likely a spatially modulated phase.

  • 311.
    Goutéraux, Blaise
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Charge transport in holography with momentum dissipation2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, s. 181-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we examine how charge is transported in a theory where momentum is relaxed by spatially dependent, massless scalars. We analyze the possible IR phases in terms of various scaling exponents and the (ir) relevance of operators in the IR effective holographic theory with a dilaton. We compute the (finite) resistivity and encounter broad families of (in) coherent metals and insulators, characterized by universal scaling behaviour. The optical conductivity at zero temperature and low frequencies exhibits power tails which can violate scaling symmetries, due to the running of the dilaton. At low temperatures, our model captures features of random-field disorder.

  • 312.
    Goutéraux, Blaise
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Universal scaling properties of extremal cohesive holographic phases2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2014, nr 1, s. 080-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that strongly-coupled, translation-invariant holographic IR phases at finite density can be classified according to the scaling behaviour of the metric, the electric potential and the electric flux introducing four critical exponents, independently of the details of the setup. Solutions fall into two classes, depending on whether they break relativistic symmetry or not. The critical exponents determine key properties of these phases, like thermodynamic stability, the (ir)relevant deformations around them, the low-frequency scaling of the optical conductivity and the nature of the spectrum for electric perturbations. We also study the scaling behaviour of the electric flux through bulk minimal surfaces using the Hartnoll-Radicevic order parameter, and characterize the deviation from the Ryu-Takayanagi prescription in terms of the criti cal exponents.

  • 313.
    Goutéraux, Blaise
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden.
    Jokela, Niko
    Univ Helsinki, Dept Phys, POB 64, FIN-00014 Helsinki, Finland.;Univ Helsinki, Helsinki Inst Phys, POB 64, FIN-00014 Helsinki, Finland..
    Ponni, Arttu
    Univ Helsinki, Dept Phys, POB 64, FIN-00014 Helsinki, Finland.;Univ Helsinki, Helsinki Inst Phys, POB 64, FIN-00014 Helsinki, Finland..
    Incoherent conductivity of holographic charge density waves2018Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 7, artikel-id 004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The DC resistivity of charge density waves weakly-pinned by disorder is controlled by diffusive, incoherent processes rather than slow momentum relaxation. The corresponding incoherent conductivity can be computed in the limit of zero disorder. We compute this transport coefficient in holographic spatially modulated breaking translations spontaneously. As a by-product of our analysis, we clarify how the boundary heat current is obtained from a conserved bulk current, de fined as a suitable generalization of the Iyer-Wald Noether current of the appropriate Killing vector.

  • 314.
    Goutéraux, Blaise
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Kiritsis, E.
    Quantum critical lines in holographic phases with (un)broken symmetry2013Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, s. 053-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    All possible scaling IR asymptotics in homogeneous, translation invariant holographic phases preserving or breaking a U(1) symmetry in the IR are classified. Scale invariant geometries where the scalar extremizes its effective potential are distinguished from hyperscaling violating geometries where the scalar runs logarithmically. It is shown that the general critical saddle-point solutions are characterized by three critical exponents (theta, z, zeta). Both exact solutions as well as leading behaviors are exhibited. Using them, neutral or charged geometries realizing both fractionalized or cohesive phases are found. The generic global IR picture emerging is that of quantum critical lines, separated by quantum critical points which correspond to the scale invariant solutions with a constant scalar.

  • 315.
    Gran, U.
    et al.
    Chalmers Univ Technol, Div Theoret Phys, Dept Phys, SE-41296 Gothenburg, Sweden..
    Tornso, M.
    Chalmers Univ Technol, Div Theoret Phys, Dept Phys, SE-41296 Gothenburg, Sweden..
    Zingg, Tobias
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Holographic plasmons2018Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, artikel-id 176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since holography yields exact results, even in situations where perturbation theory is not applicable, it is an ideal framework for modeling strongly correlated systems. We extend previous holographic methods to take the dynamical charge response into account and use this to perform the first holographic computation of the dispersion relation for plasmons. As the dynamical charge response of strange metals can be measured using the new technique of momentum-resolved electron energy-loss spectroscopy (M-EELS), plasmon properties are the next milestone in verifying predictions from holographic models of new states of matter.

  • 316. Gran, U.
    et al.
    Tornso, M.
    Zingg, Tobias
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Holographic response of electron clouds2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 3, artikel-id 019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to make progress towards more realistic models of holographic fermion physics, we use gauge/gravity duality to compute the dispersion relations for quasinormal modes and collective modes for the electron cloud background, i.e. the non-zero temperature version of the electron star. The results are compared to the corresponding results for the Schwarzschild and Reissner-Nordstrom black hole backgrounds, and the qualitative differences are highlighted and discussed.

  • 317. Gran, U.
    et al.
    Tornsö, M.
    Zingg, T0bias
    KTH, Skolan för teknikvetenskap (SCI), Fysik. Nordita, Stockholm University .
    Exotic holographic dispersion2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2019, nr 2, artikel-id 32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For strongly interacting systems, where perturbation theory is not applicable, holographic duality is a powerful framework for computing e.g. dispersion relations. Using the standard Reissner-Nordström black hole as a holographic model for a (strange) metal, we obtain exotic dispersion relations for both plasmon modes and quasinormal modes for certain intermediate values of the charge of the black hole. The obtained dispersion relations show dissipative behavior which we compare to the generic expectations from the Caldeira-Leggett model for quantum dissipation. Based on these considerations, we investigate how holography can predict higher order corrections for strongly coupled physics.

  • 318. Gran, Ulf
    et al.
    Greitz, Jesper
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Howe, Paul
    Nilsson, Bengt E. W.
    Topologically gauged superconformal Chern-Simons matter theories2012Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, s. 046-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By coupling N = 8 superconformal matter to N = 8 superconformal Chern-Simons gravity in three dimensions we obtain theories with novel terms in the scalar potential leading to AdS(3) solutions and superconformal symmetry breaking. If we start from the theory derived by Bagger, Lambert and Gustavsson, our coupled theory either inherits the SO(4) gauge group or reduces it to SO(3). If the construction is instead based on a free matter theory we find that the gravitational topological gauging also requires the introduction of a Chern-Simons gauge sector resulting in a consistent theory for any SO(N) gauge group.

  • 319.
    Greitz, Jesper
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Howe, P. S.
    Half-maximal supergravity in three dimensions: supergeometry, differential forms and algebraic structure2012Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 6, s. 177-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The half-maximal supergravity theories in three dimensions, which have local SO(8) x SO(n) and rigid SO(8, n) symmetries, are discussed in a superspace setting starting from the superconformal theory. The on-shell theory is obtained by imposing further constraints; it is essentially a non-linear sigma model that induces a Poincare supergeometry. The deformations of the geometry due to gauging are briefly discussed. The possible p-form field strengths are studied using supersymmetry and SO(8, n) symmetry. The set of such forms obeying consistent Bianchi identities constitutes a Lie super co-algebra while the demand that these identities admit solutions places a further constraint on the possible representations of SO(8, n) that the forms transform under which can be easily understood using superspace cohomology. The dual Lie superalgebra can then be identified as the positive sector of a Borcherds superalgebra that extends the Lie algebra of the duality group. In addition to the known p = 2, 3, 4 forms, which we construct explicitly, there are five-forms that can be non-zero in supergravity, while all forms with p > 5 vanish. It is shown that some six-forms can have non-trivial contributions at order alpha'.

  • 320. Gromov, Nikolay
    et al.
    Kazakov, Vladimir
    Leurent, Sebastien
    Volin, Dmytro
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Trinity College Dublin, Ireland.
    Quantum spectral curve for arbitrary state/operator in AdS(5)/CFT42015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We give a derivation of quantum spectral curve (QSC) - a finite set of Riemann-Hilbert equations for exact spectrum of planar N = 4 SYM theory proposed in our recent paper Phys. Rev. Lett. 112 (2014). We also generalize this construction to all local single trace operators of the theory, in contrast to the TBA-like approaches worked out only for a limited class of states. We reveal a rich algebraic and analytic structure of the QSC in terms of a so called Q-system - a finite set of Baxter-like Q-functions. This new point of view on the finite size spectral problem is shown to be completely compatible, though in a far from trivial way, with already known exact equations (analytic Y-system/TBA, or FiNLIE). We use the knowledge of this underlying Q-system to demonstrate how the classical finite gap solutions and the asymptotic Bethe ansatz emerge from our formalism in appropriate limits.

  • 321. Gromov, Nikolay
    et al.
    Levkovich-Maslyuk, Fedor
    Quark-anti-quark potential in=4 SYM2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, artikel-id 122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We construct a closed system of equations describing the quark-anti-quark potential at any coupling in planar = 4 supersymmetric Yang-Mills theory. It is based on the Quantum Spectral Curve method supplemented with a novel type of asymptotics. We present a high precision numerical solution reproducing the classical and one-loop string predictions very accurately. We also analytically compute the first 7 nontrivial orders of the weak coupling expansion. Moreover, we study analytically the generalized quark-anti-quark potential in the limit of large imaginary twist to all orders in perturbation theory. We demonstrate how the QSC reduces in this case to a one-dimensional Schrodinger equation. In the process we establish a link between the Q-functions and the solution of the Bethe-Salpeter equation.

  • 322. Gromov, Nikolay
    et al.
    Levkovich-Maslyuk, Fedor
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Sizov, Grigory
    New construction of eigenstates and separation of variables for SU(N) quantum spin chains2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We conjecture a new way to construct eigenstates of integrable XXX quantum spin chains with SU(N) symmetry. The states are built by repeatedly acting on the vacuum with a single operator B-good(u) evaluated at the Bethe roots. Our proposal serves as a compact alternative to the usual nested algebraic Bethe ansatz. Furthermore, the roots of this operator give the separated variables of the model, explicitly generalizing Sklyanin's approach to the SU(N) case. We present many tests of the conjecture and prove it in several special cases. We focus on rational spin chains with fundamental representation at each site, but expect many of the results to be valid more generally.

  • 323. Hagedorn, Claudia
    et al.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Riad, Stella
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Schmidt, Michael A.
    Unification of gauge couplings in radiative neutrino mass models2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the possibility of gauge coupling uni fi cation in various radiative neutrino mass models, which generate neutrino masses at one-and/or two-loop level. Renormalization group running of gauge couplings is performed analytically and numerically at one-and two-loop order, respectively. We study three representative classes of radiative neutrino mass models: (I) minimal ultraviolet completions of the dimension-7 Delta L = 2 operators which generate neutrino masses at one-and/or two-loop level without and with dark matter candidates, (II) models with dark matter which lead to neutrino masses at one-loop level and (III) models with particles in the adjoint representation of SU(3). In class (I), gauge couplings unify in a few models and adding dark matter amplifies the chances for uni fi cation. In class (II), about a quarter of the models admits gauge coupling uni fi cation. In class (III), none of the models leads to gauge coupling uni fi cation. Regarding the scale of uni fi cation, we find values between 10(14) GeV and 10(16) GeV for models belonging to class (I) without dark matter, whereas models in class (I) with dark matter as well as models of class (II) prefer values in the range 5.10(10) - 5.10(14) GeV.

  • 324.
    Harmark, Troels
    et al.
    Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark..
    Hartong, Jelle
    Univ Edinburgh, Sch Math, Peter Guthrie Tait Rd, Edinburgh EH9 3FD, Midlothian, Scotland.;Univ Edinburgh, Maxwell Inst Math Sci, Peter Guthrie Tait Rd, Edinburgh EH9 3FD, Midlothian, Scotland..
    Menculini, Lorenzo
    Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark.;Univ Perugia, Dipartimento Fis & Geol, Ist Nazl Fis Nucl, Sez Perugia, Via Pascoli, I-06123 Perugia, Italy..
    Obers, Niels A.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark.;Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Oling, Gerben
    Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark..
    Relating non-relativistic string theories2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, artikel-id 071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Non-relativistic string theories promise to provide simpler theories of quantum gravity as well as tractable limits of the AdS/CFT correspondence. However, several apparently distinct non-relativistic string theories have been constructed. In particular, one approach is to reduce a relativistic string along a null isometry in target space. Another method is to perform an appropriate large speed of light expansion of a relativistic string. Both of the resulting non-relativistic string theories only have a well-defined spectrum if they have nonzero winding along a longitudinal spatial direction. In the presence of a Kalb-Ramond field, we show that these theories are equivalent provided the latter direction is an isometry. Finally, we consider a further limit of non-relativistic string theory that has proven useful in the context of AdS/CFT (related to Spin Matrix Theory). In that case, the worldsheet theory itself becomes non-relativistic and the dilaton coupling vanishes.

  • 325.
    Herrero-Garcia, Juan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Teoretisk partikelfysik.
    Riad, Stella
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Wirén, Jens
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Full parameter scan of the Zee model: exploring Higgs lepton flavor violation2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikel-id 130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the general Zee model, which includes an extra Higgs scalar doublet and a new singly-charged scalar singlet. Neutrino masses are generated at one-loop level, and in order to describe leptonic mixing, both the Standard Model and the extra Higgs scalar doublets need to couple to leptons (in a type-III two-Higgs doublet model), which necessarily generates large lepton flavor violating signals, also in Higgs decays. Imposing all relevant phenomenological constraints and performing a full numerical scan of the parameter space, we find that both normal and inverted neutrino mass orderings can be fitted, although the latter is disfavored with respect to the former. In fact, inverted ordering can only be accommodated if theta(23) turns out to be in the first octant. A branching ratio for h -> tau mu of up to 10(-2) is allowed, but it could be as low as 10(-6). In addition, if future expected sensitivities of tau -> mu gamma are achieved, normal ordering can be almost completely tested. Also, mu e conversion is expected to probe large parts of the parameter space, excluding completely inverted ordering if no signal is observed. Furthermore, non-standard neutrino interactions are found to be smaller than 10(-6), which is well below future experimental sensitivity. Finally, the results of our scan indicate that the masses of the additional scalars have to be below 2.5 TeV, and typically they are lower than that and therefore within the reach of the LHC and future colliders.

  • 326.
    Herrero-Garcia, Juan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Rius, Nuria
    Santamaria, Arcadi
    Higgs lepton flavour violation: UV completions and connection to neutrino masses2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, artikel-id 084Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study lepton violating Higgs (HLFV) decays, first from the effective field theory (EFT) point of view, and then analysing the different high-energy realizations of the operators of the EFT, highlighting the most promising models. We argue why two Higgs doublet models can have a BR(h -> tau mu) similar to 0:01, and why this rate is suppressed in all other realizations including vector-like leptons. We further discuss HLFV in the context of neutrino mass models: in most cases it is generated at one loop giving always BR (h -> tau mu) < 10(-4) and typically much less, which is beyond experimental reach. However, both the Zee model and extended left-right symmetric models contain extra SU(2) doublets coupled to leptons and could in principle account for the observed excess, with interesting connections between HLFV and neutrino parameters.

  • 327.
    Hoppe, Jens
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    Lee, Ki-Myeong
    New BPS configurations of BMN matrix theory2008Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We explore the 1/2 BPS configurations in BMN matrix theory with SO(3) angular momentum of SO(3) x SO(6) symmetry. The fluctuation analysis of the BPS configurations near the abelian solutions and also the fuzzy two sphere vacua reveals how nonabelian BPS configurations emerge. Especially the irreducible nonabelian configurations seem to have the maximal angular momentum of order N-3 ,beyond which they collapse to abelian ones. We also find some new BPS configurations explicitly.

  • 328.
    Hällgren, Tomas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Seidl, Gerhart
    Department of Physics, Oklahoma State University.
    Neutrino oscillations in deconstructed dimensions2005Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2005, nr 02, s. 049-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a model for neutrino oscillations in the presence of a deconstructed non-gravitational large extra dimension compactified on the boundary of a two-dimensional disk. In the deconstructed phase, sub-mm lattice spacings are generated from the hierarchy of energy scales between similar to 1 TeV and the usual B - L breaking scale similar to 10(15) GeV. Here, short-distance cutoffs down to similar to 1eV are motivated by the strong coupling behavior of gravity in local discrete extra dimensions. This could make it possible to probe the discretization of extra dimensions and non-trivial field configurations in theory spaces which have only a few sites, i.e., for coarse latticizations. Thus, the model has relevance to present and future precision neutrino oscillation experiments.

  • 329.
    Johansson, Hendrik
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Uppsala University, Sweden.
    Kalin, Gregor
    Mogull, Gustav
    Two-loop supersymmetric QCD and half-maximal supergravity amplitudes2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using the duality between color and kinematics, we construct two-loop four point scattering amplitudes in N = 2 super-Yang-Mills (SYM) theory coupled to N-f fundamental hypermultiplets. Our results are valid in D <= 6 dimensions, where the upper bound corresponds to six-dimensional chiral N = (1, 0) SYM theory. By exploiting a close connection with N = 4 SYM theory-and, equivalently, six-dimensional N = (1, 1) SYM theory we find compact integrands with four-dimensional external vectors in both the maximally-helicity-violating (MHV) and all-chiral-vector sectors. Via the double-copy construction corresponding D-dimensional half-maximal supergravity amplitudes with external graviton multiplets are obtained in the MHV and all-chiral sectors. Appropriately tuning N-f enables us to consider both pure and matter-coupled supergravity, with arbitrary numbers of vector multiplets in D = 4. As a bonus, we obtain the integrands of the genuinely six-dimensional supergravities with N = (1, 1) and N = (2, 0) supersymmetry. Finally, we extract the potential ultraviolet divergence of half-maximal supergravity in D = 5-2 is an element of and show that it non-trivially cancels out as expected.

  • 330.
    Johansson, Henrik
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Uppsala Univ, Dept Phys & Astron, S-75108 Uppsala, Sweden.;Stockholm Univ, NORDITA, Roslagstullsbacken 23, S-10691 Stockholm, Sweden.
    Mogull, Gustav
    Uppsala Univ, Dept Phys & Astron, S-75108 Uppsala, Sweden..
    Teng, Fei
    Uppsala Univ, Dept Phys & Astron, S-75108 Uppsala, Sweden..
    Unraveling conformal gravity amplitudes2018Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conformal supergravity amplitudes are obtained from the double-copy construction using gauge-theory amplitudes, and compared to direct calculations starting from conformal supergravity Lagrangians. We consider several different theories: minimal N = 4 conformal supergravity, non-minimal N = 4 Berkovits-Witten conformal supergravity, mass-deformed versions of these theories, as well as supersymmetry truncations thereof. Coupling the theories to a Yang-Mills sector is also considered. For all cases we give the gravity Lagrangians that the double copy implicitly generates. The two main results are: we determine a Lagrangian for the non-minimal Berkovits-Witten theory, and we uncover the double-copy prescription for the minimal N = 4 conformal supergravity.

  • 331. Johansson, Henrik
    et al.
    Ochirov, Alexander
    Color-kinematics duality for QCD amplitudes2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikel-id 170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that color-kinematics duality is present in tree-level amplitudes of quantum chromodynamics with massive flavored quarks. Starting with the color structure of QCD, we work out a new color decomposition for n-point tree amplitudes in a reduced basis of primitive amplitudes. These primitives, with k quark-antiquark pairs and (n - 2k) gluons, are taken in the (n - 2)!/k! Melia basis, and are independent under the color-algebra Kleiss-Kuijf relations. This generalizes the color decomposition of Del Duca, Dixon, and Maltoni to an arbitrary number of quarks. The color coefficients in the new decomposition are given by compact expressions valid for arbitrary gauge group and representation. Considering the kinematic structure, we show through explicit calculations that color-kinematics duality holds for amplitudes with general configurations of gluons and massive quarks. The new (massive) amplitude relations that follow from the duality can be mapped to a well-defined subset of the familiar BCJ relations for gluons. They restrict the amplitude basis further down to (n - 3)!(2k - 2)/k! primitives, for two or more quark lines. We give a decomposition of the full amplitude in that basis. The presented results provide strong evidence that QCD obeys the color-kinematics duality, at least at tree level. The results are also applicable to supersymmetric and D-dimensional extensions of QCD.

  • 332.
    Johansson, Henrik
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Uppsala Univ, Dept Phys & Astron, SE-75108 Uppsala, Sweden.;Stockholm Univ, NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden.;Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Ochirov, Alexander
    Swiss Fed Inst Technol, Inst Theoret Phys, Wolfgang Pauli Str 27, CH-8093 Zurich, Switzerland..
    Double copy for massive quantum particles with spin2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 040Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The duality between color and kinematics was originally observed for purely adjoint massless gauge theories, and later found to hold even after introducing massive fermionic and scalar matter in arbitrary gauge-group representations. Such a generalization was critical for obtaining both loop amplitudes in pure Einstein gravity and realistic gravitational matter from the double copy. In this paper we elaborate on the double copy that yields amplitudes in gravitational theories coupled to flavored massive matter with spin, which is relevant to the problems of black-hole scattering and gravitational waves. Our construction benefits from making the little group explicit for the massive particles, as shown on lower-point examples. For concreteness, we focus on the double copy of QCD with massive quarks, for which we work out the gravitational Lagrangian up to quartic scalar and vector-scalar couplings. We find new gauge-invariant double-copy formulae for tree-level amplitudes with two distinct-flavor pairs of matter and any number of gravitons. These are similar to, but inherently different from, the well-known Kawai-Lewellen-Tye formulae, since the latter only hold for the double copy of purely adjoint gauge theories.

  • 333. Kazakov, V.
    et al.
    Leurent, S.
    Volin, D.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    T-system on T-hook: Grassmannian solution and twisted Quantum Spectral Curve2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2016, nr 12, artikel-id 44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose an efficient grassmannian formalism for solution of bi-linear finite-difference Hirota equation (T-system) on T-shaped lattices related to the space of highest weight representations of gl(K1, K2|M) superalgebra. The formalism is inspired by the quantum fusion procedure known from the integrable spin chains and is based on exterior forms of Baxter-like Q-functions. We find a few new interesting relations among the exterior forms of Q-functions and reproduce, using our new formalism, the Wronskian determinant solutions of Hirota equations known in the literature. Then we generalize this construction to the twisted Q-functions and demonstrate the subtleties of untwisting procedure on the examples of rational quantum spin chains with twisted boundary conditions. Using these observations, we generalize the recently discovered, in our paper with N. Gromov, AdS/CFT Quantum Spectral Curve for exact planar spectrum of AdS/CFT duality to the case of arbitrary Cartan twisting of AdS5×S5 string sigma model. Finally, we successfully probe this formalism by reproducing the energy of gamma-twisted BMN vacuum at single-wrapping orders of weak coupling expansion.

  • 334.
    Krikun, Alexander
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Charge density wave instability in holographic d-wave superconductor2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, s. 135-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the observation of the spatially modulated static mode in the spectrum of fluctuations around the condensed phase of the holographic d-wave superconductor. The mode involves the time component of the gauge field that is related to the charge density wave in the dual superconductor. No additional ingredients are added to the action of four dimensional theory. We speculate on the relevance of the observed mode to the formation of the pseudogap state.

  • 335.
    Krikun, Alexander
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Phases of holographic d-wave superconductor2015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 10, artikel-id 123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study different phases in the holographic model of d-wave superconductor. These are described by solutions to the classical equations of motion found in different ansatze. Apart from the known homogeneous d-wave superconducting phase we find three new solutions. Two of them represent two distinct families of the spatially modulated solutions, which realize the charge density wave phases in the dual theory. The third one is the new homogeneous phase with nonzero anapole moment. These phases are relevant to the physics of cuprate high-Tc superconductor in pseudogap region. While the d-wave phase preserves translation, parity and time reversal symmetry, the striped phases break translations spontaneously. Parity and time-reversal are preserved when combined with discrete half-periodic shift of the wave. In anapole phase translation symmetry is preserved, but parity and time reversal are spontaneously broken. All of the considered solutions break the global U(1). Thermodynamical treatment shows that in the simplest d-wave model the anapole phase is always preferred, while the stripe phases realize the continuous transition in solution space between the normal phase and two homogeneous condensed phases.

  • 336. Kristjansen, Charlotte
    et al.
    Semenoff, Gordon W.
    Young, Donovan
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Chiral primary one-point functions in the D3-D7 defect conformal field theory2013Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, s. 117-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compute the one-point functions of chiral primary operators in the non-supersymmetric defect conformal field theory that is dual to the IIB string theory on AdS(5) x S-5 background with a probe D7 brane with internal gauge field flux, both in perturbative Yang-Mills theory and in the string theory dual. The former is expected to be accurate at weak coupling whereas the latter should be accurate in the planar strong coupling limit of the gauge theory. We consider the distinct cases where the D7 brane has geometry AdS(4) x S-4 with an instanton bundle of the worldvolume gauge fields on S-4 and AdS(4) x S-2 x S-2 with Dirac monopole bundles on each S-2. The gauge theory computation and the string theory computation can be compared directly in the planar limit and then a subsequent limit where the worldvolume flux is large. We find that there is exact agreement between the two in the leading order.

  • 337. Könnig, F.
    et al.
    Nersisyan, H.
    Akrami, Y.
    Amendola, L.
    Zumalacárregui, Miguel
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    A spectre is haunting the cosmos: quantum stability of massive gravity with ghosts2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2016, nr 11, artikel-id 118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many theories of modified gravity with higher order derivatives are usually ignored because of serious problems that appear due to an additional ghost degree of freedom. Most dangerously, it causes an immediate decay of the vacuum. However, breaking Lorentz invariance can cure such abominable behavior. By analyzing a model that describes a massive graviton together with a remaining Boulware-Deser ghost mode we show that even ghostly theories of modified gravity can yield models that are viable at both classical and quantum levels and, therefore, they should not generally be ruled out. Furthermore, we identify the most dangerous quantum scattering process that has the main impact on the decay time and find differences to simple theories that only describe an ordinary scalar field and a ghost. Additionally, constraints on the parameters of the theory including some upper bounds on the Lorentz-breaking cutoff scale are presented. In particular, for a simple theory of massive gravity we find that a breaking of Lorentz invariance is allowed to happen even at scales above the Planck mass. Finally, we discuss the relevance to other theories of modified gravity.

  • 338.
    Lafaye, Remi
    et al.
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Plehn, Tilman
    Rauch, Michael
    Zerwas, Dirk
    Duhrssen, Michael
    Measuring the Higgs Sector2009Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 8, s. 009-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    If we find a light Higgs boson at the LHC, there should be many observable channels which we can exploit to measure the relevant parameters in the Higgs sector. We use the SFitter framework to map these measurements on the parameter space of a general weak-scale effective theory with a light Higgs state of mass 120GeV. Our analysis benefits from the parameter determination tools and the error treatment used in new-physics searches, to study individual parameters and their error bars as well as parameter correlations.

  • 339.
    Langmann, Edwin
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Szabo, R. J.
    Zarembo, K.
    Exact solution of quantum field theory on noncommutative phase spaces2004Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, s. 017-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the exact solution of a scalar field theory defined with noncommuting position and momentum variables. The model describes charged particles in a uniform magnetic field and with an interaction defined by the Groenewold-Moyal star-product. Explicit results are presented for all Green's functions in arbitrary even spacetime dimensionality. Various scaling limits of the field theory are analysed non-perturbatively and the renormalizability of each limit examined. A supersymmetric extension of the field theory is also constructed in which the supersymmetry transformations are parametrized by differential operators in an in finite-dimensional noncommutative algebra.

  • 340. Litim, Daniel F.
    et al.
    Mojaza, Matin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Sannino, Francesco
    Vacuum stability of asymptotically safe gauge-Yukawa theories2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikel-id 081Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the phase diagram and the stability of the ground state for certain four-dimensional gauge-Yukawa theories whose high-energy behaviour is controlled by an interacting fixed point. We also provide analytical and numerical results for running couplings, their crossover scales, the separatrix, and the Coleman-Weinberg effective potential. Classical and quantum stability of the vacuum is established.

  • 341.
    Marmiroli, Daniele
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    Phase structure of N=2*SYM on ellipsoids2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 6, artikel-id 035Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyse the phase structure of an N = 2 massive deformation of N = 4 SYM theory on a four-dimensional ellipsoid using recent results on supersymmetric localisation. Besides the 't Hooft coupling lambda, the relevant parameters appearing in the theory and discriminating between the different phases are the hypermultiplet mass M and the deformation (or squashing) parameter Q. Geometric deformation manifests itself as an effective mass term, thus braking the conformal invariance of the theory with massless hypermultiplets. The structure of perturbative corrections around the spherical geometry is analysed in the details and a systematic computational procedure is given, together with the first few corrections. The master field approximation of the matrix model associated to the analytically continued theory in the regime Q similar to 2 M and on the compact space is exactly solvable and does not display any phase transition, similarly to N = 2 SU(N) SYM with 2N massive hypermultiplets. In the strong coupling limit, equivalent in our settings to the decompactification of the four-dimensional ellipsoid, we find evidence that the theory undergoes an in finite number of phase transitions starting at finite coupling and accumulating at lambda = infinity. Quite interestingly, the threshold points at which transitions occur can be pushed towards the weak coupling region by drifting Q to the value 2M.

  • 342.
    Medina-Rincon, Daniel
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Tseytlin, Arkady A.
    Imperial Coll, Blackett Lab, London SW7 2AZ, England.;Lebedev Inst, Moscow, Russia..
    Zarembo, Konstantin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Precision matching of circular Wilson loops and strings in AdS(5) x S-52018Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 5, artikel-id 199Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previous attempts to match the exact N = 4 super Yang-Mills expression for the expectation value of the 1/2-BPS circular Wilson loop with the semiclassical AdS(5) x S-5 string theory prediction were not successful at the first subleading order. There was a missing prefactor similar to lambda(-3/4) which could be attributed to the unknown normalization of the string path integral measure. Here we resolve this problem by computing the ratio of the string partition functions corresponding to the circular Wilson loop and the special 1/4-supersymmetric latitude Wilson loop. The fact that the latter has a trivial expectation value in the gauge theory allows us to relate the prefactor to the contribution of the three zero modes of the "transverse" fluctuation operator in the 5-sphere directions.

  • 343.
    Melbéus, Henrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Searches for hyperbolic extra dimensions at the LHC2008Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2008, nr 08, s. 077-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate a model of large extra dimensions where the internal space has the geometry of a hyperbolic disc. Compared with the ADD model, this model provides a more satisfactory solution to the hierarchy problem between the electroweak scale and the Planck scale, and it also avoids constraints from astrophysics. In general, a novel feature of this model is that the physical results depend on the position of the brane in the internal space, and in particular, the signal almost disappears completely if the brane is positioned at the center of the disc. Since there is no known analytic form of the Kaluza-Klein spectrum for our choice of geometry, we obtain a spectrum based on a combination of approximations and numerical computations. We study the possible signatures of our model for hadron colliders, especially the LHC, where the most important processes are the production of a graviton together with a hadronic jet or a photon. We find that the signals are similar to those of the ADD model, regarding both qualitative behavior and strength. For the case of hadronic jet production, it is possible to obtain relatively strong signals, while for the case of photon production, this is much more difficult.

  • 344. Meloni, Davide
    et al.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Riad, Stella
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Effects of intermediate scales on renormalization group running of fermion observables in an SO(10) model2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, s. 052-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati-Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale.

  • 345. Meloni, Davide
    et al.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Teoretisk partikelfysik.
    Riad, Stella
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Teoretisk partikelfysik.
    Renormalization group running of fermion observables in an extended non-supersymmetric SO(10) model2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 3, artikel-id 045Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the renormalization group evolution of fermion masses, mixings and quartic scalar Higgs self-couplings in an extended non-supersymmetric SO(10) model, where the Higgs sector contains the 10(H), 120(H), and 126(H) representations. The group SO(10) is spontaneously broken at the GUT scale to the Pati-Salam group and subsequently to the Standard Model (SM) at an intermediate scale MI. We explicitly take into account the effects of the change of gauge groups in the evolution. In particular, we derive the renormalization group equations for the different Yukawa couplings. We find that the computed physical fermion observables can be successfully matched to the experimental measured values at the electroweak scale. Using the same Yukawa couplings at the GUT scale, the measured values of the fermion observables cannot be reproduced with a SM-like evolution, leading to differences in the numerical values up to around 80%. Furthermore, a similar evolution can be performed for a minimal SO(10) model, where the Higgs sector consists of the 10(H) and 126(H) representations only, showing an equally good potential to describe the low-energy fermion observables. Finally, for both the extended and the minimal SO(10) models, we present predictions for the three Dirac and Majorana CP-violating phases as well as three effective neutrino mass parameters.

  • 346. Meloni, Davide
    et al.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Winter, Walter
    Zhang, He
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory2010Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2010, nr 04, s. 041-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The impact of heavy mediators on neutrino oscillations is typically described by non-standard four-fermion interactions (NSIs) or non-unitarity (NU). We focus on leptonic dimension-six effective operators which do not produce charged lepton flavor violation. These operators lead to particular correlations among neutrino production, propagation, and detection non-standard effects. We point out that these NSIs and NU phenomenologically lead, in fact, to very similar effects for a neutrino factory, for completely different fundamental reasons. We discuss how the parameters and probabilities are related in this case, and compare the sensitivities. We demonstrate that the NSIs and NU can, in principle, be distinguished for large enough effects at the example of non-standard effects in the mu-tau-sector, which basically corresponds to differentiating between scalars and fermions as heavy mediators as leading order effect. However, we find that a near detector at superbeams could provide very synergistic information, since the correlation between source and matter NSIs is broken for hadronic neutrino production, while NU is a fundamental effect present at any experiment.

  • 347. Meloni, Davide
    et al.
    Ohlsson, Tommy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Zhang, He
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
    Exact and approximate formulas for neutrino mixing and oscillations with non-standard interactions2009Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2009, nr 04, s. 033-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present, both exactly and approximately, a complete set of mappings between the vacuum (or fundamental) leptonic mixing parameters and the effective ones in matter with non-standard neutrino interaction (NSI) effects included. Within the three-flavor neutrino framework and a constant matter density profile, a full set of sum rules is established, which enables us to reconstruct the moduli of the effective leptonic mixing matrix elements, in terms of the vacuum mixing parameters in order to reproduce the neutrino oscillation probabilities for future long-baseline experiments. Very compact, but quite accurate, approximate mappings are obtained based on series expansions in the neutrino mass hierarchy parameter eta equivalent to Delta m(21)(2)/Delta m(31)(2), the vacuum leptonic mixing parameter s(13) equivalent to sin theta(13), and the NSI parameters epsilon(alpha beta). A detailed numerical analysis about how the NSIs affect the smallest leptonic mixing angle theta(13), the deviation of the leptonic mixing angle theta(23) from its maximal mixing value, and the transition probabilities useful for future experiments are performed using our analytical results.

  • 348.
    Merle, Alexander
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Zwicky, Roman
    Explicit and spontaneous breaking of SU(3) into its finite subgroups2012Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 2, s. 128-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the breaking of SU(3) into its subgroups from the viewpoints of explicit and spontaneous breaking. A one-to-one link between these two approaches is given by the complex spherical harmonics, which form a complete set of SU(3)-representation functions. An invariant of degrees p and q in complex conjugate variables corresponds to a singlet, or vacuum expectation value, in a (p; q)-representation of SU(3). We review the formalism of the Molien function, which contains information on primary and secondary invariants. Generalizations of the Molien function to the tensor generating functions are discussed. The latter allows all branching rules to be deduced. We have computed all primary and secondary invariants for all proper finite subgroups of order smaller than 512, for the entire series of groups Delta(3n(2)), Delta(6n(2)), and for all crystallographic groups. Examples of sufficient conditions for breaking into a subgroup are worked out for the entire Tn[a]-, Delta(3n(2))-, Delta(6n(2))-series and for all crystallographic groups Sigma(X). The corresponding invariants provide an alternative definition of these groups. A Mathematica package, SUtree, is provided which allows the extraction of the invariants, Molien and generating functions, syzygies, VEVs, branching rules, character tables, matrix (p; q)(SU(3))-representations, Kronecker products, etc. for the groups discussed above.

  • 349. Mueller, Dennis
    et al.
    Muenkler, Hagen
    Plefka, Jan
    Pollok, Jonas
    Zarembo, Konstantin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Yangian symmetry of smooth Wilson loops in N=4 super Yang-Mills theory2013Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, s. 081-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that appropriately supersymmetrized smooth Maldacena-Wilson loop operators in N = 4 super Yang-Mills theory are invariant under a Yangian symmetry Y[psu(2, 2 vertical bar 4)] built upon the manifest superconformal symmetry algebra of the theory. The existence of this hidden symmetry is demonstrated at the one-loop order in the weak coupling limit as well as at leading order in the strong coupling limit employing the classical integrability of the dual AdS(5) x S-5 string description. The hidden symmetry generators consist of a canonical non-local second order variational derivative piece acting on the superpath, along with a novel local path dependent contribution. We match the functional form of these Yangian symmetry generators at weak and strong coupling and find evidence for an interpolating function. Our findings represent the smooth counterpart to the Yangian invariance of scattering superamplitudes dual to light-like polygonal super Wilson loops in the N = 4 super Yang-Mills theory.

  • 350.
    Månsson, Teresia
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    The Liegh-Strassler deformation and the quest for integrability2007Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we study the one-loop dilatation operator of the full scalar field sector of Leigh-Strassler deformed =4 SYM theory. In particular we map it onto a spin chain and find the parameter values for which the Reshetikhin integrability criteria are fulfilled. Some years ago Roiban found an integrable subsector, consisting of two holomorphic scalar fields, corresponding to the XXZ model. He was pondering about the existence of a subsector which would form generalisation of that model to an integrable q(3) model. Later Berenstein and Cherkis added one more holomorphic field and showed that the subsector obtained this way cannot be integrable except for the case when q = eiβ, β. In this work we show if we add an anti-holomorphic field to the two holomorphic ones, we get indeed an integrable q(3) subsector. We find it plausible that a direct generalisation to a q(2|3) one-loop sector will exist, and possibly beyond one-loop.

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