Holography, conformal field theories, and lattice

Name: Holography, conformal field theories, and lattice
Start: 2016-06-27T07:45:00+01:00
End: 2016-06-30T18:00:00+01:00
Location: Higgs Centre for Theoretical Physics

27 Jun 2016, 07:45 → 30 Jun 2016, 18:00 Europe/London

Higgs Centre for Theoretical Physics

School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom

Luigi Del Debbio (The University of Edinburgh), Oliver Witzel (Higgs Centre for Theoretical Physics)

Description

Following the discovery of the Higgs boson in July 2012 at CERN, the most urgent questions in theoretical particle physics concern the nature of the Higgs particle and physics beyond the standard model related to the Higgs mechanism. Experimental results for the Run 2 of the LHC will challenge our understanding of physics at the TeV scale. There are numerous proposals for new physics beyond the Standard Model that rely on some kind of strongly coupled dynamics. They can only be addressed quantitatively by developing tools that describe the nonperturbative regime of Quantum Field Theories, thereby opening the door for numerous interesting theoretical problems. Several directions have been explored in recent years, ranging from holography and duality, to the bootstrap, conformal field theory methods, large-N methods, effective field theories, and lattice simulations. These approaches allow the exploration of complementary aspects of nonperturbative dynamics beyond the Standard Model. They are also challenging theoretical problems by themselves, which have sparked new interesting ideas and research programmes. The aim of this four day workshop on strongly coupled scenarios is to bring together practitioners in these fields, identify the most fruitful proposals, and focus on the possibility to exploit synergies between the different methods.

Monday, 27 June
- 09:00 → 10:00
  
  Registration & coffee
  
  Conformal field theory
- 10:00 → 10:55
  
  Holography, Conformal invariance and phase transitions in QCD-like theories 55m
  
  Speaker: Elias Kiritsis
  
  Slides
- 10:55 → 11:30
  
  Coffee break
- 11:30 → 12:25
  
  N=1 Euler Anomaly Flow from Dilaton Effective Action 55m
  
  We consider N=1 supersymmetric gauge theories in the conformal window. The running of the gauge coupling is absorbed into the metric by applying a suitable matter superfield- and Weyl-transformation. The computation becomes equivalent to one of a free theory in a curved background carrying the information of the renormalisation group flow. We use the techniques of conformal anomaly matching and dilaton effective action, by Komargodski and Schwimmer, to rederive the difference of the Euler anomaly coefficient Δa≡aUV−aIR for the N=1 theory. The structure of Δa is therefore in one-to-one correspondence with the Wess-Zumino dilaton action.
  
  Speaker: Roman Zwicky
  
  Slides
- 12:30 → 13:25
  
  Lunch
- 13:30 → 14:25
  
  The Quantum Simplicial Lattice for Conformal Field theory on Curved Manifolds. 55m
  
  Speaker: Richard Brower
  
  Slides
- 14:30 → 15:25
  
  Large mass hierarchies from strongly-coupled dynamics 55m
  
  Speaker: Maurizio Piai
  
  Slides
- 15:25 → 16:00
  
  Coffee break
- 16:00 → 16:55
  
  Exact results in (Super) QFT: From Asymptotic Freedom to Asymptotic Safety 55m
  
  I will present new exact results in four-dimensional quantum field theory that led to the discovery to asymptotically safe theories in four dimensions without supersymmetry. I will also discuss supersymmetric extensions and present new exact results that make use of a number of non-perturbative tools ranging from the unitary of the conformal operators to the a-theorem and maximisation. The results have far reaching consequences for the construction of novel extensions of the standard model of particle interactions.
  
  Speaker: Francesco Sannino
- 17:00 → 17:55
  
  Discussion
Tuesday, 28 June
- 09:00 → 09:55
  
  An ambitious alternative: Partial Compositeness 55m
  
  Speaker: Luca Vecchi
  
  Slides
- 10:00 → 10:55
  
  Gauge theories of partial compositeness. Scenarios for the Lattice and the LHC 55m
  
  We present a class of gauge theories in which the Higgs boson arises as a pseudo-Nambu-Goldstone boson and top-partners arise as bound states of three hyperfermions. All models have additional pNGBs in their spectrum that should be accessible at LHC, including one that can explain the current diphoton excess at 750~GeV. We discuss how the Lattice can help answering some of the questions about their strong coupling regime. Finally, we paint a broad, qualitative, picture of the kind of experimental signatures that can be expected from these models.
  
  Speaker: Gabriele Ferretti
  
  Slides
- 11:00 → 11:30
  
  Coffee break 30m
- 11:30 → 12:25
  
  Higgs Coupling measurements and UV implications 55m
  
  I will discuss the implications of recent LHC measurements for Higgs physics using effective field theory methods. On the basis of these results I will discuss the status of concrete UV scenarios, in particular composite Higgs models.
  
  Speaker: Christoph Englert
  
  Slides
- 12:25 → 13:25
  
  Lunch
- 13:30 → 14:25
  
  Composite Higgs Dynamics on the Lattice 55m
  
  We investigate the spectrum of the SU(2) gauge theory with Nf = 2 flavors of fermions in the fundamental representation, in the continuum, using Lattice simulations [1,2,3]. This model provides a minimal template which has been used for different strongly coupled extensions of the Standard Model ranging from composite (Goldstone) Higgs models [4] to intriguing types of dark matter candidates, such as the SIMPs [5]. Here we will focus on the composite Goldstone Higgs paradigm, for which this model provides a minimal UV complete realization in terms of a new strong sector with fermionic matter, as argued in [4]. After introducing the relevant Lattice methods used in our simulations, we will discuss our numerical results. We show that this model features a SU(4)/Sp(4) ~ SO(6)/SO(5) flavor symmetry breaking pattern, as expected, and estimate the value of its chiral condensate. Finally, we present our results for the mass spectrum of the lightest spin one and zero resonances, analogue to the QCD rho, a1, sigma, eta', a0 resonances, which are relevant for searches of new, exotic resonances at the LHC. Ref: [1] R. Arthur, V. Drach, M. Hansen, A Hietanen, C.Pica, F. Sannino, arXiv:1602.06559 [hep-lat] [2] R. Lewis, C. Pica, F. Sannino, arXiv:1109.3513 [hep-ph] [3] A. Hietanen, R. Lewis, C. Pica, F. Sannino, arXiv:1404.2794 [hep-lat] [4] G. Cacciapaglia, F. Sannino, arXiv:1402.0233 [hep-ph] [5] Y.Hochberg, E.Kuflik, H.Murayama, T.Volansky,and J.G.Wacker, arXiv:1411.3727.
  
  Speaker: Claudio Pica
- 14:30 → 15:25
  
  Composite Higgs model based on a conformal fixed point 55m
  
  We construct a prototype BSM model where the Higgs boson is a pseudo Nambu-Goldstone boson by combining 4 light (massless) flavors and 8 heavy flavors. In the infrared, the SU(4) chiral symmetry is spontaneously broken , while in the ultraviolet it exhibits the properties of the $N_f=12$ conformal fixed point. The running coupling of this system ``walks" and the energy range of walking can be tuned by the mass of the heavy flavors. At the same time, renormalization group considerations predict the spectrum of such a system to show hyperscaling i.e. hadron masses in units of $F_\pi$ are independent of the heavy mass. Hyperscaling is present for bound states made-up of light, heavy, or heavy and light flavors. This observation is supported by numerical observations and makes the model strongly predictive.
  
  Speaker: Anna Hasenfratz
  
  Slides
- 15:30 → 16:00
  
  Coffee break 30m
- 16:00 → 16:55
  
  Crossing the conformal window: SU(2) with 2-8 fundamental fermions 55m
  
  SU(2) gauge theory is asymptotically free with Nf <= 10 fundamental representation fermions. Above approximately 6 fermion flavours the theory is expected to have an infrared fixed point. We study the evolution of the coupling using the gradient flow step scaling mehtod, and investigate the behaviour of the hadron spectrum as we cross from the confining into the conformal region.
  
  Speaker: Kari Rummukainen
- 17:00 → 17:55
  
  Discussion
Wednesday, 29 June
- 09:00 → 09:55
  
  Theta angle, the quark mass, and the conformal window in holographic QCD 55m
  
  I discuss holographic QCD in the Veneziano limit (large N_c and N_f with x=N_f/N_c fixed) where quarks are fully backreacted to gluons. When all quark flavors are identical, QCD in this limit has two parameters in addition to Lambda_QCD, namely the quark mass and the theta angle. I demostrate how these parameters can be included in holographic QCD, and discuss the resulting phase diagram. At small quark mass the results from holography agree with effective field theory. In particular, the masses of the pion and the eta prime meson satisfy the expected relations.
  
  Speaker: Mätti Jarvinen
  
  Slides
- 10:00 → 10:55
  
  Direct test of the gauge/gravity duality for the D0-brane system at finite N 55m
  
  We test the gauge/gravity duality conjecture directly by using Monte Carlo methods to study the strongly coupled regime of the relevant gauge theory. In particular, we focus on the D0-brane system, which is described by a one-dimensional gauge theory with 16 supercharges. Extending our previous work, which confirmed the duality in the large-N limit, we investigate whether the duality holds including the 1/N corrections. On the gravity side, this corresponds to including the quantum string loop corrections. The bound state of black 0-branes becomes meta-stable due to such effects as indicated by the negative specific heat at low temperature. The meta-stability shows up also on the gauge theory side due to the flat directions of the scalar field potential. Introducing a cutoff on the value of the scalar fields and investigating the cutoff dependence carefully, we extract the internal energy of the metastable bound state as a function of temperature. The results thus obtained turn out to be consistent with the predition from the gravity side including the leading quantum string loop corrections calculated recently.
  
  Speaker: Jun Nishimura
  
  Slides
- 11:00 → 11:30
  
  Coffee break 30m
- 11:30 → 12:25
  
  Magnetically induced phenomena and Holographic QCD 55m
  
  Speaker: Umut Gürsoy
  
  Slides
- 12:30 → 13:25
  
  Lunch
- 13:30 → 14:25
  
  Recent results on large N gauge theories on the lattice 55m
  
  We review progress made recently in obtaining results on large N gauge theories using the lattice formulation together with the concept of volume independence
  
  Speaker: Tony Gonzalez-Arroyo
  
  Slides
- 14:30 → 15:25
  
  Volume independence beyond large N 55m
  
  In the limit of infinite numbers of coulours in Yang-Mills theory, the interplay between volume and group degrees of freedom has led to the concept of volume independence through Eguchi-Kawai reduction. We will discuss an attempt to extend this idea beyond the large N limit. A few non-perturbative examples will be presented, including the running of the SU(N) ’t Hooft coupling and the 2+1 dimensional glueball spectrum.
  
  Speaker: Marga Garcia-Perez
  
  Slides
- 15:30 → 16:00
  
  Coffee break 30m
- 16:00 → 16:55
  
  Large N mesons 55m
  
  Speaker: Gunnar Bali
  
  Slides
- 17:00 → 17:55
  
  Discussion
- 18:45 → 20:45
  
  Dinner 2h Amber Restaurant ()
  
  Amber Restaurant
  
  Scotch Whisky Experience 354 Castlehill The Royal Mile Edinburgh EH1 2NE
Thursday, 30 June
- 09:00 → 09:55
  
  Near-conformal composite Higgs or PNGB with partial compositeness? 55m
  
  Based on recent analysis of the LatHC collaboration I will review critical features of a minimal composite Higgs model close to the conformal window. Challenging problems of the near-conformal paradigm will be compared with PNGB based partial compositeness.
  
  Speaker: Julius Kuti
  
  Slides
- 10:00 → 10:55
  
  A Spartan model for the LHC Diphoton Excess 55m
  
  I will describe a very simple model accommodating the reported 750 GeV diphoton excess seen in the ﬁrst 13-TeV run of the LHC. It leads to testable predictions, in particular for di-lepton production, at higher integrated luminosity. A new gauge sector with its own SU(2) symmetry group is appended to the minimal standard model. A new complex doublet scalar ﬁeld provides mass for the heavy vectors and describes the 750-GeV resonance. A new global U(1) symmetry plays a key role, and current precision-electroweak constraints are respected. An adequate rate for the diphoton signals, with resonant production via photon fusion, requires the VEV of the new scalar ﬁeld to be no larger than the electroweak scale. This in turn requires the new heavy vectors to have sub-TeV masses and be relatively strongly coupled.
  
  Speaker: Tom Appelquist
  
  Slides
- 11:00 → 11:30
  
  Coffee break 30m
- 11:30 → 12:25
  
  A composite model for flavor and diphoton anomalies 55m
  
  Among all LHC results, the most exciting signs of deviations from the SM are, on the one hand, a series of hints of violation of lepton-flavor universality in various B-meson decays and, on the other hand, the excess in diphoton invariant mass distribution at 750GeV. In this talk I discuss a class of new physics models with composite dynamics aimed at addressing both sets of anomalies in a coherent framework, as well as their predictions for future LHC studies.
  
  Speaker: David Marzocca
  
  Slides
- 12:30 → 13:25
  
  Lunch
- 13:30 → 14:25
  
  Talk 6: Determining the β-function in Nf = 3 QCD 55m
  
  Speaker: Alberto Ramos
  
  Slides
- 14:30 → 15:25
  
  Lattice QCD averages from non-equilibrium transformations 55m
  
  We discuss an efficient method to compute expectation values of generic observables in lattice Monte Carlo calculations, by evaluating the work performed during a non-equilibrium transformation between configurations in different equilibrium ensembles. This technique, which relies on a theorem proven by Christopher Jarzynski in 1997, has potential applications for a broad spectrum of challenging problems in QCD and in other strongly coupled gauge theories. We present results of two benchmark studies: the computation of the free energy associated with a fluctuating interface and the determination of the equation of state of a gas of hadrons.
  
  Speaker: Marco Panero
  
  Slides
- 15:30 → 16:00
  
  Coffee break 30m
- 16:00 → 16:55
  
  Bump hunting at the LHC 55m
  
  Speaker: Christos Leonidopoulos (ATLAS)
  
  Slides

Holography, conformal field theories, and lattice

Higgs Centre for Theoretical Physics

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