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  • 1. Bern, Zvi
    et al.
    Davies, Scott
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark .
    Nohle, Josh
    Low-energy behavior of gluons and gravitons from gauge invariance2014Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, nr 8, s. 084035-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that at tree level, on-shell gauge invariance can be used to fully determine the first subleading soft-gluon behavior and the first two subleading soft-graviton behaviors. Our proofs of the behaviors for n-gluon and n-graviton tree amplitudes are valid in D dimensions and are similar to Low's proof of universality of the first subleading behavior of photons. In contrast to photons coupling to massive particles, in four dimensions the soft behaviors of gluons and gravitons are corrected by loop effects. We comment on how such corrections arise from this perspective. We also show that loop corrections in graviton amplitudes arising from scalar loops appear only at the second soft subleading order. This case is particularly transparent because it is not entangled with graviton infrared singularities. Our result suggests that if we set aside the issue of infrared singularities, soft-graviton Ward identities of extended Bondi, van der Burg, Metzner and Sachs symmetry are not anomalous through the first subleading order.

  • 2. Collado, A. K.
    et al.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute University of Copenhagen Copenhagen Denmark.
    Russo, R.
    Thomas, S.
    The subleading eikonal in supergravity theories2018Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2018, nr 10, artikkel-id 38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we study the subleading contributions to eikonal scattering in (super)gravity theories with particular emphasis on the role of both elastic and inelastic scattering processes. For concreteness we focus on the scattering of various massless particles off a stack of Dp-branes in type II supergravity in the limit of large impact parameter b. We analyse the relevant field theory Feynman diagrams which naturally give rise to both elastic and inelastic processes. We show that in the case analysed the leading and subleading eikonal only depend on elastic processes, while inelastic processes are captured by a pre-factor multiplying the exponentiated leading and subleading eikonal phase. In addition to the traditional Feynman diagram computations mentioned above, we also present a novel method for computing the amplitudes contributing to the leading and subleading eikonal phases, which, in the large b limit, only involves knowledge of the onshell three and four-point vertices. The two methods are shown to give the same results. Furthermore we derive these results in yet another way, by computing various one-point amplitudes which allow us to extract the classical solution of the gravitational back reaction of the target Dp-branes. Finally we show how our expressions for the leading and subleading eikonal agree with the calculation of the metric and corresponding deflection angle for massless states moving along geodesics in the relevant curved geometry.

  • 3.
    Collado, Arnau Koemans
    et al.
    Queen Mary Univ London, Sch Phys & Astron, Ctr Res String Theory, Mile End Rd, London E1 4NS, England..
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen, Denmark.;Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Russo, Rodolfo
    Queen Mary Univ London, Sch Phys & Astron, Ctr Res String Theory, Mile End Rd, London E1 4NS, England..
    Revisiting the second post-Minkowskian eikonal and the dynamics of binary black holes2019Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, nr 6, artikkel-id 066028Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we study the two-body gravitational scattering of massive scalars with different masses in general spacetime dimensions. We focus on the Regge limit (eikonal regime) of the resulting scattering amplitudes and discuss how to extract the classical information representing the scattering of two black holes. We derive the leading eikonal and explicitly show the resummation of the first leading energy contribution up to second order in Newton's gravitational constant. We also calculate the subleading eikonal showing that in general spacetime dimensions it receives a nontrivial contribution from the box integral. From the eikonal we extract the two-body classical scattering angle between the two black holes up to the second post-Minkowskian order. Taking various probe-limits of the two-body scattering angles we are able to show agreement between our results and various results in the literature. We highlight that the box integral also has a log-divergent (in energy) contribution at subsubleading order which violates perturbative unitarity in the ultrarelativistic limit. We expect this term to play a role in the calculation of the eikonal at the third post-Minkowskian order.

  • 4.
    D'Appollonio, G.
    et al.
    Univ Cagliari, Dipartimento Fis, I-09042 Monserrato, Italy.;INFN 5 Cittadella Univ, I-09042 Monserrato, Italy..
    Di Vecchia, Pablo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Russo, R.
    Queen Mary Univ London, Mile End Rd, London E1 4NS, England.;Ecole Normale Super, Lab Phys Theor, 24 Rue Lhomond, F-75231 Paris, France..
    Veneziano, G.
    Coll France, 11 Pl M Berthelot, F-75005 Paris, France.;CERN, Div Theory, CH-1211 Geneva 23, Switzerland..
    The Leading Eikonal Operator in String-Brane Scattering at High Energy2014Inngår i: BREAKING OF SUPERSYMMETRY AND ULTRAVIOLET DIVERGENCES IN EXTENDED SUPERGRAVITY / [ed] Bellucci, S, SPRINGER-VERLAG BERLIN , 2014, s. 145-162Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present two (a priori independent) derivations of the eikonal operator in string-brane scattering. The first one is obtained by summing surfaces with any number of boundaries, while in the second one the eikonal operator is derived from the three-string vertex in a suitable light-cone gauge. This second derivation shows that the bosonic oscillators present in the leading eikonal operator are to be identified with the string bosonic oscillators in a suitable light-cone gauge, while the first one shows that it exponentiates recovering unitarity. This paper is a review of results obtained in [1, 2].

  • 5. D’Appollonio, G.
    et al.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Russo, R.
    Veneziano, G.
    Regge behavior saves string theory from causality violations2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, nr 5, artikkel-id 144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: Higher-derivative corrections to the Einstein-Hilbert action are present in bosonic string theory leading to the potential causality violations recently pointed out by Camanho et al. [1]. We analyze in detail this question by considering high-energy string-brane collisions at impact parameters b ≤ l<inf>s</inf> (the string-length parameter) with l<inf>s</inf> ≫ R<inf>p</inf> (the characteristic scale of the Dp-brane geometry). If we keep only the contribution of the massless states causality is violated for a set of initial states whose polarization is suitably chosen with respect to the impact parameter vector. Such violations are instead neatly avoided when the full structure of string theory — and in particular its Regge behavior — is taken into account.

  • 6. D'Appollonio, Giuseppe
    et al.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Russo, Rodolfo
    Veneziano, Gabriele
    A microscopic description of absorption in high-energy string-brane collisions2016Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 3, artikkel-id 030Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters - where elastic scattering and/or tidal excitations dominate - here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. As a first step, we study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose particularly simple properties are described.

  • 7. D'Appollonio, Giuseppe
    et al.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Russo, Rodolfo
    Veneziano, Gabriele
    Microscopic unitary description of tidal excitations in high-energy string-brane collisions2013Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, s. 126-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The eikonal operator was originally introduced to describe the effect A tidal excitations on higher-genus elastic string amplitudes at high energy. In this paper we provide a precise interpretation for this operator through the explicit tree-level calculation of generic inelastic transitions between closed strings as they scatter off a stack of parallel Dp-branes. We perform this analysis both in the light-cone gauge, using the Green-Schwarz vertex, and in the covariant formalism, using the Reggeon vertex operator. We also present a detailed discussion of the high-energy behaviour of the covariant string amplitudes, showing how to take into account the energy factors that enhance the contribution of the longitudinally polarized massive states in a simple way.

  • 8.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    My interaction with Stanley2017Inngår i: International Journal of Modern Physics A, ISSN 0217-751X, E-ISSN 1793-656X, Vol. 32, nr 12, artikkel-id 1740019Artikkel i tidsskrift (Fagfellevurdert)
  • 9.
    Di Vecchia, Paolo
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    My interaction with stanley2017Inngår i: Memorial Volume For Stanley Mandelstam, World Scientific Publishing Co. Pte. Ltd. , 2017, s. 137-139Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 10.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen Ø, Denmark.
    Marotta, R.
    Mojaza, Matin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Double-soft behavior for scalars and gluons from string theory2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, nr 12, s. 1-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: We compute the leading double-soft behavior for gluons and for the scalars obtained by dimensional reduction of a higher dimensional pure gauge theory, from the scattering amplitudes of gluons and scalars living in the world-volume of a Dp-brane of the bosonic string. In the case of gluons, we compute both the double-soft behavior when the two soft gluons are contiguous as well as when they are not contiguous. From our results, that are valid in string theory, one can easily get the double-soft limit in gauge field theory by sending the string tension to infinity.

  • 11.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, University of Copenhagen, Denmark.
    Marotta, R.
    Mojaza, Matin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Subsubleading soft theorems of gravitons and dilatons in the bosonic string2016Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2016, nr 6, artikkel-id 54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: Starting from the amplitude with an arbitrary number of massless closed states of the bosonic string, we compute the soft limit when one of the states becomes soft to subsubleading order in the soft momentum expansion, and we show that when the soft state is a graviton or a dilaton, the full string amplitude can be expressed as a soft theorem through subsubleading order. It turns out that there are string corrections to the field theoretical limit in the case of a soft graviton, while for a soft dilaton the string corrections vanish. We then show that the new soft theorems, including the string corrections, can be simply obtained from the exchange diagrams where the soft state is attached to the other external states through the three-point string vertex of three massless states. In the soft-limit, the propagator of the exchanged state is divergent, and at tree-level these are the only divergent contributions to the full amplitude. However, they do not form a gauge invariant subset and must be supplemented with extra non-singular terms. The requirement of gauge invariance then fixes the complete amplitude through subsubleading order in the soft expansion, reproducing exactly what one gets from the explicit calculation in string theory. From this it is seen that the string corrections at subsubleading order arise as a consequence of the three-point amplitude having string corrections in the bosonic string. When specialized to a soft dilaton, it remarkably turns out that the string corrections vanish and that the non-singular piece of the subsubleading term of the dilaton soft theorem is the generator of space-time special conformal transformation. © 2016, The Author(s).

  • 12.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    Double-soft behavior of the dilaton of spontaneously broken conformal invariance2017Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2017, nr 9, artikkel-id 001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Ward identities involving the currents associated to the spontaneously broken scale and special conformal transformations are derived and used to determine, through linear order in the two soft-dilaton momenta, the double-soft behavior of scattering amplitudes involving two soft dilatons and any number of other particles. It turns out that the double-soft behavior is equivalent to performing two single-soft limits one after the other. We confirm the new double-soft theorem perturbatively at tree-level in a D-dimensional conformal field theory model, as well as nonperturbatively by using the "gravity dual" of N = 4 super Yang-Mills on the Coulomb branch; i.e. the Dirac-Born-Infeld action on AdS(5) x S-5.

  • 13.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Complesso Univ Monte S Angelo, Sez Napoli, Ist Nazl Fis Nucl, Ed 6,Via Cintia, I-80126 Naples, Italy..
    Mojaza, Matin
    Albert Einstein Inst, Max Planck Inst Gravitat Phys, Muhlenberg 1, D-14476 Potsdam, Germany..
    Multiloop soft theorem for gravitons and dilatons in the bosonic string2019Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 1, artikkel-id 038Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We construct, in the closed bosonic string, the multiloop amplitude involving N tachyons and one massless particle with 26 - D compactified directions, and we show that at least for D > 4, the soft behaviors of the graviton and dilaton satisfy the same soft theorems as at the tree level, up to one additional term at the subsubleading order, which can only contribute to the dilaton soft behavior and which we show is zero at least at one loop. This is possible, since the infrared divergences due to the non-vanishing tachyon and dilaton tadpoles do not depend on the number of external particles and are therefore the same both in the amplitude with the soft particle and in the amplitude without the soft particle. Therefore this leaves unchanged the soft operator acting on the amplitude without the soft particle. The additional infrared divergence appearing for D 4 depend on the number of external legs and must be understood on their own.

  • 14.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Complesso Univ Monte S Angelo, Sez Napoli, Ist Nazl Fis Nucl, Edificio 6,Via Cintia, I-80126 Naples, Italy..
    Mojaza, Matin
    Max Planck Inst Gravitat Phys, Albert Einstein Inst, Muhlenberg 1, DE-14476 Potsdam, Germany..
    Multiloop soft theorem of the dilaton in the bosonic string2019Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, nr 4, artikkel-id 041902Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that by fixing the multiloop Green function in the closed bosonic string to be Arakelov's Green function, one obtains factorization of scattering amplitudes with a softly emitted dilaton to the same level as with a graviton to all loop order. This extends our previous analysis at one loop to all loop orders and confirms that some high-energy quantum symmetry in the bosonic string protects the factorization of amplitudes with softly emitted dilatons.

  • 15.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Mojaza, Matin
    Soft behavior of a closed massless state in superstring and universality in the soft behavior of the dilaton2016Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, artikkel-id 020Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the tree-level scattering amplitudes in the NS-NS (Neveu-Schwarz) massless sector of closed superstrings in the case where one external state becomes soft. We compute the amplitudes generically for any number of dimensions and any number and kind of the massless closed states through the subsubleading order in the soft expansion. We show that, when the soft state is a graviton or a dilaton, the full result can be expressed as a soft theorem factorizing the amplitude in a soft and a hard part. This behavior is similar to what has previously been observed in field theory and in the bosonic string. Differently from the bosonic string, the supersymmetric soft theorem for the graviton has no string corrections at subsubleading order. The dilaton soft theorem, on the other hand, is found to be universally free of string corrections in any string theory.

  • 16.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    Soft theorem for the graviton, dilaton and the Kalb-Ramond field in the bosonic string2015Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 5, artikkel-id 137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the behavior of the scattering amplitudes of the bosonic string involving a soft massless state (graviton, dilaton and Kalb-Ramond antisymmetric tensor) and closed string tachyons or other closed string massless states. For a soft graviton we confirm the results, obtained in ref. [37] using just gauge invariance, up to terms of O(q(1)) for external tachyons and up to terms of O(q(0)) for external massless closed string states. Furthermore, we also derive the behavior of the scattering amplitude when a dilaton or a Kalb-Ramond field becomes soft. These results are new and cannot, to our knowledge, be derived by using gauge invariance. It turns out, in the cases examined, that the soft amplitude for a dilaton or for an antisymmetric tensor is obtained by saturating the tensor, M (mu nu) , derived from gauge invariance for gravitons, with their respective polarization tensors. Thus extra terms that could have appeared in M (mu nu) in the case of a soft dilaton, in fact do not appear.

  • 17.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    Soft Theorems from String Theory2016Inngår i: Fortschritte der Physik, ISSN 0015-8208, E-ISSN 1521-3978, Vol. 64, nr 4-5, s. 389-393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soft behaviour of closed string amplitudes involving dilatons, gravitons and anti-symmetric tensors, is studied in the framework of bosonic string theory. The leading double soft limit of gluons is analysed as well, starting from scattering amplitudes computed in the open bosonic string. Field theory expressions are then obtained by sending the string tension to infinity. The presented results have been derived in the papers of Ref [1].

  • 18.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Mojaza, Matin
    The B-field soft theorem and its unification with the graviton and dilaton2017Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 10, artikkel-id 017Artikkel i tidsskrift (Fagfellevurdert)
  • 19.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Mojaza, Matin
    Nohle, Josh
    New soft theorems for the gravity dilaton and the Nambu-Goldstone dilaton at subsubleading order2016Inngår i: PHYSICAL REVIEW D, ISSN 2470-0010, Vol. 93, nr 8, artikkel-id 085015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the soft behavior of two seemingly different particles that are both referred to as dilatons in the literature, namely the one that appears in theories of gravity and in string theory and the Nambu-Goldstone boson of spontaneously broken conformal invariance. Our primary result is the discovery of a soft theorem at subsubleading order for each dilaton, which in both cases contains the operator of special conformal transformations. Interesting similarities as well as differences between the dilaton soft theorems are discussed.

  • 20.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, Denmark.
    Rossi, Giancarlo
    Veneziano, Gabriele
    Yankielowicz, Shimon
    Spontaneous CP breaking in QCD and the axion potential: an effective Lagrangian approach2017Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 12, artikkel-id 104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the well-known low-energy effective Lagrangian of QCD - valid for small (non-vanishing) quark masses and a large number of colors - we study in detail the regions of parameter space where CP is spontaneously broken/unbroken for a vacuum angle theta = pi. In the CP broken region there are first order phase transitions as one crosses theta = pi, while on the (hyper)surface separating the two regions, there are second order phase transitions signalled by the vanishing of the mass of a pseudo Nambu-Goldstone boson and by a divergent QCD topological susceptibility. The second order point sits at the end of a first order line associated with the CP spontaneous breaking, in the appropriate complex parameter plane. When the effective Lagrangian is extended by the inclusion of an axion these features of QCD imply that standard calculations of the axion potential have to be revised if the QCD parameters fall in the above mentioned CP broken region, in spite of the fact that the axion solves the strong-CP problem. These last results could be of interest for axionic dark matter calculations if the topological susceptibility of pure Yang-Mills theory falls off sufficiently fast when temperature is increased towards the QCD deconfining transition.

  • 21.
    Di Vecchia, Paolo
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, University of Copenhagen, Denmark.
    Sannino, F.
    The physics of the θ-angle for composite extensions of the standard model2014Inngår i: The European Physical Journal Plus, ISSN 2190-5444, E-ISSN 2190-5444, Vol. 129, nr 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse the θ-angle physics associated to extensions of the standard model of particle interactions featuring new strongly coupled sectors. We start by providing a pedagogical review of the θ-angle physics for Quantum Chromodynamics (QCD) including also the axion properties. We then move to analyse composite extensions of the standard model elucidating the interplay between the new θ-angle with the QCD one. We consider first QCD-like dynamics and then generalise it to consider several kinds of new strongly coupled gauge theories with fermions transforming according to different matter representations. Our analysis is of immediate use for different models of composite Higgs dynamics, composite dark matter and inflation.

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