The infrared regime of SU(2) with one adjoint Dirac flavour

Bennett, Ed (KMI, Nagoya University and Department of Physics, Swansea University)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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))

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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)

Abstract:

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.