List of Poster Presentations

The infrared regime of SU(2) with one adjoint Dirac flavour
Bennett, Ed (KMI, Nagoya University and Department of Physics, Swansea University)
The SU(2) gauge theory with one Dirac flavour in the adjoint representation is investigated on the lattice for a value of the bare coupling in the region connected to the continuum limit. Results for the gluonic and mesonic spectrum, string tension from Wilson and Polyakov loops, and the anomalous dimension of the fermionic condensate from the Dirac mode number are presented. From these, we see evidence that the theory does not show conventional confining behaviour, instead seeming to lie within or very near the onset of the conformal window. The anomalous dimension of the fermionic condensate is found to lie in the range 0.9 \lesssim \gamma_* \lesssim 0.95. The implications of our work for building a realistic theory of strongly interacting dynamics beyond the Standard Model are discussed, and future directions of our investigation are outlined.
Extended Mean Field Theory for complex phi^4 at finite density and temperature
de Forcrand, Philippe (ETH Zurich & CERN)
We review the Extended Mean Field Theory (EMFT) and apply it to complex, scalar phi^4 theory on the lattice. Results of this analytic approximation at finite temperature and density, together with the corresponding (T,mu) phase diagram, agree very well with recent Monte Carlo simulations.
Lattice Radial Quantization
Fleming, George (Yale University)
I present the current status of a program to formulate D-dimensional strongly-coupled relativistic quantum field theories on lattice discretizations of cylindrical manifolds whose cross-section is a (D-1)-dimensional sphere. Critical points in such theories should correspond to Conformal Field Theories (CFTs) if the full rotational symmetry of the sphere can be recovered in the continuum limit. If the formulation is successful, studying these CFTs should be numerically much less expensive that the equivalent calculations on a D-dimensional torus.
Finite size scaling of conformal theories in the presence of a near-marginal operator
Hasenfratz, Anna (University of Colorado Boulder)
The slowly evolving gauge coupling of gauge-fermion systems near the conformal window makes numerical investigations of these models challenging. We consider finite size scaling and show that in the case of 12-flavor SU(3) gauge theory this often used technique leads to inconsistent results if the leading order scaling corrections are neglected. When the corrections are included the results become consistent not only between different operators but even when data obtained at different gauge couplings or with different lattice actions are combined. Our results indicate that the SU(3) 12-fermion system is conformal with mass anomalous dimension $\gamma_m=0.235(15)$.
Running coupling from gradient flow for the $N_f=12$ SU(3) model
Hasenfratz, Anna (University of Colorado Boulder)
We investigate the renormalized running coupling defined through the Wilson gradient flow in the SU(3) 12-flavor system. We find that the step scaling function develops a zero on every lattice volume and scale change we investigated. These zeros persist even after taking the continuum limit. Using a new optimization technique we show that with our nHYP smeared staggered action the continuum extrapolations are well controlled and predict g^2_{IRFP}=6.21(25) with the c=0.2 Wilson flow.
Entropy for curvature squared gravity using surface term and auxiliary field
Hirochi, Kyosuke (Nagoya University)
We calculate the entropies of general curvature squared gravities in arbitrary dimensions by using the conserved charge and the Virasoro algebra coming from surface term. We introduce an auxiliary tensor field in order to obtain the boundary action which establishes a variational principle. For some specific models, that is, the Gauss-Bonnet, new massive gravity (NMG), and critical gravity, the known results are reproduced.
Phase structure study of SU(2) lattice gauge theory with 8 flavours
Huang, Cynthia Yu-Han (NCTU)
We present the phase structure of SU(2) lattice gauge theory with 8 flavours (staggered fermions) in fundamental representation. Average plaquette and Polyakov loop are measured and one phase transition is observed. To identify the order of this confining-deconfining phase transition, we apply different studies for plaquette and Polyakov loop. Here we present results from studies of APE smearing and effective potential for Polyakov loop. Moreover, we would like to show some preliminary results of eigenvalue density for studying the chiral condensate, being the order parameter for spontaneous chiral symmetry breaking.
Anti-evaporation in massive/bi-gravity and their extension to F(R) gravity
Katsuragawa, Taishi (Nagoya University)
It is well known that the horizon radius of the black hole usually decreases by the Hawking radiation. Bousso and Hawking, however, found a phenomenon where the black hole radius increases by the quantum correction for the specific Nariai black hole. This phenomenon is called anti-evaporation of black holes. We consider and disuss the phenomenon for black holes in massive gravity which describes a massive graviton and in bigravity which describes a massive graviton and a massless graviton. We also extend the above discussion to F(R) massive/bi-gravity.
SU(3) gauge theory with four fundamental fermions on the lattice
Kurachi, Masafumi (KMI, Nagoya University)
LatKMI collaboration has been studying SU(3) gauge theories with large numbers of fermion flavor (Nf) with the fundamental representation. Physical picture of the Nf=4 SU(3) gauge theory is considered to be qualitatively similar to the real-life QCD. To confirm whether that kind of belief is correct or not itself is interesting enough, and also it is very important to study Nf=4 physics to make a contrast to the physical picture of Nf=8, 12. In this presentation, I will present the results of our lattice simulations on the Nf=4 SU(3) gauge theory (including the preliminary results of the flavor singlet scalar mass measurement), and discuss the qualitative difference between Nf=4 and Nf=8, 12 SU(3) gauge theories.
Lattice Higgs-Yukawa Study -- large Yukawa coupling phases and higher dimensional operators
Lin, C.-J. David (National Chiao-Tung University, Taiwan)
The Higgs boson discovery at LHC with a mass of 126 GeV suggests, that the electroweak vacuum of the standard model may be metastable at high energies. However, any new physics beyond the Standard Model (BSM) can change this picture. We want to address this important question within a non-perturbative study of a chirally invariant lattice Higgs-Yukawa model as the limit of the SM. In this workshop, we present results of our ongoing project on the lattice study of the Higgs-Yukawa model, of (1) the phase structure at small and large Yukawa couplings and (2) the effect of higher dimensional operators, e.g. a $\phi^6$-term, which could originate as a remnant of BSM physics at very large scales.
The Miransky-Yamawaki phase diagram at finite temperature
Lombardo, Maria Paola (INFN)
Shortly after the discovery of the conformal phase of QCD, V. Mirasnky and K. Yamawaki proposed a lattice phase diagram in the space spanned by the flavor number and the lattice bare coupling. We extend this construction to finite temperature, and discuss the signatures of the onset for conformality and IRFP at the critical number of flavor using model calculations and lattice results.
Lattice simulation of SU(2) gauge theory with domain-wall fermions
Matsufuru, Hideo (High Energy Accelerator Research Organization (KEK))
We numerically study the SU(2) gauge theory with dynamical domain-wall fermions in the fundamental representation. For Nf=2, the meson spectra and the residual mass are measured on three lattice volumes and at two values of gauge coupling so as to investigate the finite volume effect. We show the results of the meson spectra on $16^3\time 32$ lattice with Nf=4, 6, and 8.
Glueball masses and the string tension of twelve-flavor QCD
Rinaldi, Enrico (Physics Division @ Lawrence Livermore National Laboratory)
In recent lattice studies of the SU(3) gauge theory with 12 fundamental fermions, the debate has focused on the existence of a non-trivial infrared fixed point in the chiral limit. Gluonic observables, like the string tension or glueball masses, can be measured and used together with mesonic observables in order to determine the spectrum hierarchy in the chiral limit of the theory. We measure the string tension using Polyakov loop and also rectangular Wilson loop correlators. Glueball masses with scalar quantum numbers are obtained from a variational analysis featuring a large number of interpolating operators. We discuss the results and their extrapolation to the chiral limit.
Schwinger-Dyson Study for walking/conformal dynamics with UV and IR Cutoffs
Shibata, Akihiro (KEK)
We study the UV and IR cutoff effects of the walking/conformal dynamics near critical coupling (flavor) by using Schwinger-Dyson (SD) equation for many flavor QCD with the 2-loop running coupling and the ladder approximation, because such effect to the mass deformed walking/conformal theories is still unclear. By solving SD equation numerically for various parameter space of UV- and IR cutoffs, bare fermion mass in both chiral broken and conformal phases, we investigate mainly the UV- and IR-cutoff effects for the mass anomalous dimension ($\gamma_m$), the pole mass ($M_p$) and so on. In this poster presentation, we show that IR-cutoff depresses the mass enhancement and changes the scaling relation (the possibility of obtaining a small $\gamma_m$) depending on whether $M_p$ is larger or smaller than IR-cutoff. Our study may give some interpretation for the results found in the lattice step scaling function method and the hyper scaling relation near the critical coupling. Furthermore, we derive the analytic formula for the SD-equation solution within the standing coupling and linearized approximations. The formula keeps the cutoff effects and is applicable in both symmetric and broken phases. Our study gives a firm step to our future studies on the many flavor QCD at finite temperature and density.
Exploring many-flavor QCD using two-flavor configurations
Yamada, Norikazu (KEK)
In order to discuss the feasibility of electroweak baryogenesis in technicolor scenario, it is important to know thermal properties of many flavor QCD as quantitatively as possible. However, even if we only focus on the critical endpoint, it is very demanding to determine it over the various number of flavors. We present the status report on the exploratory study surveying various Nf and fermion mass at one time.
Non-perturbative lattice study of 16-flavor QCD
Yamazaki, Takeshi (KMI, Nagoya University)
It is well known that the SU(3) gauge theory with the fundamental 16-flavor fermion is governed by a non-trivial infrared fixed point in the 2-loop perturbation theory, while the theory has not been well investigated by non-perturbative lattice simulations. We investigate properties of 16-flavor QCD by lattice simulation with highly improved actions(HISQ/tree) at several lattice spacings. We present the results for the mass of the lightest pseudoscalar meson, and its decay constant at non-zero fermion mass. We discuss finite-size hyperscaling of the quantities, the mass anomalous dimension extracted from the scaling, and comparison of the anomalous dimension with the perturbation theory.