74,083 research outputs found
Continuum EoS for QCD with Nf=2+1 flavors
We report on a continuum extrapolated result [arXiv:1309.5258] for the
equation of state (EoS) of QCD with dynamical quark flavors. In this
study, all systematics are controlled, quark masses are set to their physical
values, and the continuum limit is taken using at least three lattice spacings
corresponding to temporal extents up to . A Symanzik improved gauge and
stout-link improved staggered fermion action is used. Our results are available
online [ancillary file to arXiv:1309.5258].Comment: Conference proceedings, 7 pages, 4 figures. Talk presented at 31st
International Symposium on Lattice Field Theory (LATTICE 2013), July 29 -
August 3, 2013, Mainz, German
The light bound states of supersymmetric SU(2) Yang-Mills theory
Supersymmetry provides a well-established theoretical framework for
extensions of the standard model of particle physics and the general
understanding of quantum field theories. We summarise here our investigations
of N=1 supersymmetric Yang-Mills theory with SU(2) gauge symmetry using the
non-perturbative first-principles method of numerical lattice simulations. The
strong interactions of gluons and their superpartners, the gluinos, lead to
confinement, and a spectrum of bound states including glueballs, mesons, and
gluino-glueballs emerges at low energies. For unbroken supersymmetry these
particles have to be arranged in supermultiplets of equal masses. In lattice
simulations supersymmetry can only be recovered in the continuum limit since it
is explicitly broken by the discretisation. We present the first continuum
extrapolation of the mass spectrum of supersymmetric Yang-Mills theory. The
results are consistent with the formation of supermultiplets and the absence of
non-perturbative sources of supersymmetry breaking. Our investigations also
indicate that numerical lattice simulations can be applied to non-trivial
supersymmetric theories.Comment: 19 pages, 6 figure
Recent results on the Equation of State of QCD
We report on a continuum extrapolated result (arXiv:1309.5258) for the
equation of state (EoS) of QCD with dynamical quark flavors and
discuss preliminary results obtained with an additional dynamical charm quark
(). For all our final results, the systematics are controlled, quark
masses are set to their physical values, and the continuum limit is taken using
at least three lattice spacings corresponding to temporal extents up to
.Comment: Conference proceedings: The 32nd International Symposium on Lattice
Field Theory - Lattice 2014, June 23-28, 2014, Columbia University, New York,
New Yor
Extended investigation of the twelve-flavor -function
We report new results from high precision analysis of an important BSM gauge
theory with twelve massless fermion flavors in the fundamental representation
of the SU(3) color gauge group. The range of the renormalized gauge coupling is
extended from our earlier work {Fodor:2016zil} to probe the existence of an
infrared fixed point (IRFP) in the -function reported at two different
locations, originally in {Cheng:2014jba} and at a new location in
{Hasenfratz:2016dou}. We find no evidence for the IRFP of the -function
in the extended range of the renormalized gauge coupling, in disagreement with
{Cheng:2014jba,Hasenfratz:2016dou}. New arguments to guard the existence of the
IRFP remain unconvincing {Hasenfratz:2017mdh}, including recent claims of an
IRFP with ten massless fermion flavors {Chiu:2016uui,Chiu:2017kza} which we
also rule out. Predictions of the recently completed 5-loop QCD
-function for general flavor number are discussed in this context.Comment: 7 pages, 9 figure
Critical exponents for the long-range Ising chain using a transfer matrix approach
The critical behavior of the Ising chain with long-range ferromagnetic
interactions decaying with distance , , is investigated
using a numerically efficient transfer matrix (TM) method. Finite size
approximations to the infinite chain are considered, in which both the number
of spins and the number of interaction constants can be independently
increased. Systems with interactions between spins up to 18 sites apart and up
to 2500 spins in the chain are considered. We obtain data for the critical
exponents associated with the correlation length based on the Finite
Range Scaling (FRS) hypothesis. FRS expressions require the evaluation of
derivatives of the thermodynamical properties, which are obtained with the help
of analytical recurrence expressions obtained within the TM framework. The Van
den Broeck extrapolation procedure is applied in order to estimate the
convergence of the exponents. The TM procedure reduces the dimension of the
matrices and circumvents several numerical matrix operations.Comment: 10 pages, 2 figures, Conference NEXT Sigma Ph
Quark mass dependence of the nucleon axial-vector coupling constant
We study the quark mass expansion of the axial-vector coupling constant g_A
of the nucleon. The aim is to explore the feasibility of chiral effective field
theory methods for extrapolation of lattice QCD results - so far determined at
relatively large quark masses corresponding to pion masses larger than 0.6 GeV
- down to the physical value of the pion mass. We compare two versions of
non-relativistic chiral effective field theory: One scheme restricted to pion
and nucleon degrees of freedom only, and an alternative approach which
incorporates explicit Delta(1230) resonance degrees of freedom. It turns out
that, in order to approach the physical value of g_A in a leading-one-loop
calculation, the inclusion of the explicit Delta(1230) degrees of freedom is
crucial. With information on important higher order couplings constrained from
analyses of inelastic pion production processes, a chiral extrapolation
function for g_A is obtained, which works well from the chiral limit across the
physical point into the region of present lattice data. The resulting
enhancement of our extrapolation function near the physical pion mass is found
to arise from an interplay between long- and short- distance physics.Comment: 21 pages, LaTeX, 7 figure
- …