Change search
Refine search result
1 - 15 of 15
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Bern, Zvi
    et al.
    Davies, Scott
    Di Vecchia, Paolo
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark .
    Nohle, Josh
    Low-energy behavior of gluons and gravitons from gauge invariance2014In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, no 8, p. 084035-Article in journal (Refereed)
    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. D’Appollonio, G.
    et al.
    Di Vecchia, Paolo
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Russo, R.
    Veneziano, G.
    Regge behavior saves string theory from causality violations2015In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, no 5, article id 144Article in journal (Refereed)
    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.

  • 3. D'Appollonio, Giuseppe
    et al.
    Di Vecchia, Paolo
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Russo, Rodolfo
    Veneziano, Gabriele
    A microscopic description of absorption in high-energy string-brane collisions2016In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 030Article in journal (Refereed)
    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.

  • 4. D'Appollonio, Giuseppe
    et al.
    Di Vecchia, Paolo
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Russo, Rodolfo
    Veneziano, Gabriele
    Microscopic unitary description of tidal excitations in high-energy string-brane collisions2013In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 11, p. 126-Article in journal (Refereed)
    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.

  • 5.
    Di Vecchia, Paolo
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    My interaction with Stanley2017In: International Journal of Modern Physics A, ISSN 0217-751X, E-ISSN 1793-656X, Vol. 32, no 12, article id 1740019Article in journal (Refereed)
  • 6.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen Ø, Denmark.
    Marotta, R.
    Mojaza, Matin
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Double-soft behavior for scalars and gluons from string theory2015In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, no 12, p. 1-23Article in journal (Refereed)
    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.

  • 7.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. The Niels Bohr Institute, University of Copenhagen, Denmark.
    Marotta, R.
    Mojaza, Matin
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Subsubleading soft theorems of gravitons and dilatons in the bosonic string2016In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2016, no 6, article id 54Article in journal (Refereed)
    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).

  • 8.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    Double-soft behavior of the dilaton of spontaneously broken conformal invariance2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2017, no 9, article id 001Article in journal (Refereed)
    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.

  • 9.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, 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 dilaton2016In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 12, article id 020Article in journal (Refereed)
    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.

  • 10.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    Soft theorem for the graviton, dilaton and the Kalb-Ramond field in the bosonic string2015In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, article id 137Article in journal (Refereed)
    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.

  • 11.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Copenhagen, Denmark.
    Marotta, Raffaele
    Mojaza, Matin
    Soft Theorems from String Theory2016In: Fortschritte der Physik, ISSN 0015-8208, E-ISSN 1521-3978, Vol. 64, no 4-5, p. 389-393Article in journal (Refereed)
    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].

  • 12.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Marotta, Raffaele
    Mojaza, Matin
    The B-field soft theorem and its unification with the graviton and dilaton2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 017Article in journal (Refereed)
  • 13.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, 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 order2016In: PHYSICAL REVIEW D, ISSN 2470-0010, Vol. 93, no 8, article id 085015Article in journal (Refereed)
    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.

  • 14.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, 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 approach2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 12, article id 104Article in journal (Refereed)
    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.

  • 15.
    Di Vecchia, Paolo
    et al.
    KTH, Centres, 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 model2014In: The European Physical Journal Plus, ISSN 2190-5444, E-ISSN 2190-5444, Vol. 129, no 12Article in journal (Refereed)
    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.

1 - 15 of 15
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf