Extended simulation results and their analysis are reported in a strongly coupled gauge theory with twelve fermion flavors in the fundamental SU(3) color representation. The conformality of the model is probed using mass deformed... more
Extended simulation results and their analysis are reported in a strongly coupled gauge theory with twelve fermion flavors in the fundamental SU(3) color representation. The conformality of the model is probed using mass deformed conformal finite size scaling (FSS) theory driven by the fermion mass anomalous dimension. Two independent conformal FSS fitting procedures are used in the analysis. The first one deploys physics motivated scaling functions, complemented by a second fitting procedure with spline based general B-forms for the scaling functions. The results at fixed gauge coupling show unresolved problems with the conformal hypothesis.
The Yang-Mills gradient flow in finite volume is used to define a running coupling scheme. As our main result the discrete beta-function, or step scaling function, is calculated for scale change s=3/2 at several lattice spacings for SU(3)... more
The Yang-Mills gradient flow in finite volume is used to define a running coupling scheme. As our main result the discrete beta-function, or step scaling function, is calculated for scale change s=3/2 at several lattice spacings for SU(3) gauge theory coupled to N_f = 4 fundamental massless fermions. The continuum extrapolation is performed and agreement is found with the continuum perturbative results for small renormalized coupling. The case of SU(2) gauge group is briefly commented on.
Research Interests:
This White Paper has been prepared as a planning document for the Division of High Energy Physics of the U. S. Department of Energy. Recent progress in lattice-based studies of physics beyond the standard model is summarized, and major... more
This White Paper has been prepared as a planning document for the Division of High Energy Physics of the U. S. Department of Energy. Recent progress in lattice-based studies of physics beyond the standard model is summarized, and major current goals of USQCD research in this area are presented. Challenges and opportunities associated with the recently discovered 126 GeV Higgs-like particle are highlighted. Computational resources needed for reaching important goals are described. The document was finalized on February 11, 2013 with references that are not aimed to be complete, or account for an accurate historical record of the field.
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The cut-off effects of the lattice gradient flow -- often called Wilson flow -- are calculated on a periodic 4-torus at leading order in the gauge coupling. A large class of discretizations is considered which includes all frequently used... more
The cut-off effects of the lattice gradient flow -- often called Wilson flow -- are calculated on a periodic 4-torus at leading order in the gauge coupling. A large class of discretizations is considered which includes all frequently used cases in practice. It is shown how the results lead to a smoother continuum extrapolation for the beta-function of SU(3) gauge theory with N_f = 4 flavors of fermions.
The strongly coupled near-conformal gauge theory with two fermion flavors in the two-index symmetric (sextet) representation of SU(3) is potentially a minimal realization of the composite Higgs mechanism. We discuss the staggered fermion... more
The strongly coupled near-conformal gauge theory with two fermion flavors in the two-index symmetric (sextet) representation of SU(3) is potentially a minimal realization of the composite Higgs mechanism. We discuss the staggered fermion construction of baryonic states, present our first numerical results and comment on implications for dark matter.
Work in progress is reported on a particularly interesting gauge theory with a fermion doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Extending previous studies we outline our strategy as we... more
Work in progress is reported on a particularly interesting gauge theory with a fermion doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Extending previous studies we outline our strategy as we investigate Goldstone dynamics and Electroweak scale setting from chiral symmetry breaking (\chi SB), test the GMOR relation from the spectrum of the Dirac operator and the related chiral condensate, begin to develop and test mixed action based improved analysis of \chi SB with new run plans at fixed topology to cross over from the p-regime to the epsilon-regime of \chi SB, continue to pursue the light $0^{++}$ scalar and its relation to the dilaton, and probe the scale-dependent running coupling from the perturbative UV scale to the scale of chiral symmetry breaking. Our observations suggest that the model is very close to the conformal window and a light composite scalar, perhaps the Higgs impostor with or without dilaton-like interpretation, appears...
Rational Hybrid Monte Carlo (RHMC) HMC is a powerful tool to simulate dynamical fermions -global updating and exact. a conjugate momentum field π(x) is introduced, and a kinetic term, exp(-π(x) 2 /2), is added to the action to form a... more
Rational Hybrid Monte Carlo (RHMC) HMC is a powerful tool to simulate dynamical fermions -global updating and exact. a conjugate momentum field π(x) is introduced, and a kinetic term, exp(-π(x) 2 /2), is added to the action to form a fictitious Hamiltonian detailed balance and equivalence to the original system are straightforward the fermion field is replaced with a pseudofermion field ; the root is approximated by Zolotarev's (rational polynomial) method the φ and π fields are evolved according to classical equations of motion finally, the resulting φ field is accepted or rejected based on the fictitious ∆H. Fourier Acceleration Results For the case studied, FA reduces τ by up to 2 orders of magnitude. Decreasing m FA improves decorrelation, but instability arises for too small m FA . It will be interesting to test the FA on larger lattices and see how the related critical exponent is affected as in [7]. References [1-3] Z.
We report extended simulation results and their new analysis in two important gauge theories with twelve fermion flavors in the fundamental SU(3) color representation and two fermions in the sextet representation. We probe the $N_f=12$... more
We report extended simulation results and their new analysis in two important gauge theories with twelve fermion flavors in the fundamental SU(3) color representation and two fermions in the sextet representation. We probe the $N_f=12$ model with respect to the conformal window using mass deformed finite size scaling (FSS) theory driven by the fermion mass anomalous dimension. Our results at fixed gauge coupling show problems with the conformal scenario of the $N_f=12$ model. In the sextet model with two flavors, under the conformal hypothesis, we determine large values for the anomalous fermion mass dimension with $\gamma\geq 1$. Since our sextet analysis favors the chiral symmetry breaking hypothesis without conformality, the large exponent $\gamma$ could play an important role in understanding the composite Higgs mechanism. The new results discussed here include our extended data sets and exceed what was presented at the conference.
We investigate two models of much recent interest in lattice Beyond Standard Model studies: N_f=2 fermions in the 2-index symmetric (sextet) representation, and N_f=12 fermions in the fundamental representation, both with SU(3) gauge... more
We investigate two models of much recent interest in lattice Beyond Standard Model studies: N_f=2 fermions in the 2-index symmetric (sextet) representation, and N_f=12 fermions in the fundamental representation, both with SU(3) gauge symmetry. We present results at fixed lattice spacing for the static fermion potential and force as measured via lattice simulations. We show indications that both models are confining in the chiral limit and that neither theory is conformal. This is consistent with our findings for the mass spectrum, which indicate that chiral symmetry is spontaneously broken in both theories.
The frequently discussed strongly interacting gauge theory with a fermion flavor doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group is investigated. In previous studies the chiral condensate and the... more
The frequently discussed strongly interacting gauge theory with a fermion flavor doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group is investigated. In previous studies the chiral condensate and the mass spectrum were shown to be consistent with chiral symmetry breaking ($\chi$SB) at vanishing fermion mass. The recently reported $\beta$-function is not inconsistent with this observation, suggesting that the model is very close to the conformal window and a light "Higgs impostor" could emerge as a composite state. In this work we describe the methodology and preliminary results of studying the emergence of the light composite scalar with $0^{++}$ quantum numbers.
Research Interests:
Research Interests:
... elte. hu Chris Schroeder Department of Physics, University of Wuppertal, Gauss Strasse 20, D-42119, Germany E-mail: crs@ physics. ... 63. B. K. T. V. E. T. T. T. T. S. S. S. Z. Z. Z. Z. Z. Z. Z. A. A. A. A. A. L. L. F. Y. T. O. T. T.... more
... elte. hu Chris Schroeder Department of Physics, University of Wuppertal, Gauss Strasse 20, D-42119, Germany E-mail: crs@ physics. ... 63. B. K. T. V. E. T. T. T. T. S. S. S. Z. Z. Z. Z. Z. Z. Z. A. A. A. A. A. L. L. F. Y. T. O. T. T. A. X. X. D. J. E. E. M. M. A. C. U. G. C. Y. Y. Holdom, Phys. ...
Research Interests:
Recent findings on the spectrum of heavy-quark mesons from computer simulations of quarks and gluons in lattice QCD are summarized, with particular attention to quark-antiquark states bound by an excited gluon field. The validity of a... more
Recent findings on the spectrum of heavy-quark mesons from computer simulations of quarks and gluons in lattice QCD are summarized, with particular attention to quark-antiquark states bound by an excited gluon field. The validity of a Born-Oppenheimer treatment for such systems is discussed. Recent results on glueball masses, the light-quark 1-+ hybrid meson mass, and the static three-quark potential are
Research Interests:
Research Interests:
Research Interests:
The renormalized trajectory (RT) is determined from two different Monte Carlo renormalization group techniques with $\delta$-function block spin transformation in the multi-dimensional coupling parameter space of the two-dimensional... more
The renormalized trajectory (RT) is determined from two different Monte Carlo renormalization group techniques with $\delta$-function block spin transformation in the multi-dimensional coupling parameter space of the two-dimensional non-linear sigma model with O(3) symmetry. At a correlation length $\xi \approx 3$-$5$, the RT is shown to break away from the straight line of the fixed point trajectory (FPT) which is
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We report new results for lattice gauge theories with twelve fermion flavors in the fundamental representation and two fermion flavors in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Both models are... more
We report new results for lattice gauge theories with twelve fermion flavors in the fundamental representation and two fermion flavors in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Both models are important in searching for a viable composite Higgs mechanism in the Beyond the Standard Model (BSM) paradigm. We subject both models to opposite hypotheses inside and outside of the conformal window. In the first hypothesis we test chiral symmetry breaking ($\chi{\rm SB}$) with its Goldstone spectrum, $F_\pi$, the $\chi{\rm SB}$ condensate, and several composite hadron states as the fermion mass is varied in a limited range with our best effort to control finite volume effects. Supporting results for $\chi{\rm SB}$ from the running coupling based on the force between static sources is also presented. In the second test for the alternate hypothesis we probe conformal behavior driven by a single anomalous mass dimension under the assumption of unbroken c...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
... years gluon thermodynamics has been studied extensively within the framework of lat-ticequantum chromodynamics. ... 198 5 VOLUME 54, NUMBER 2 I - - PHYSICAL REVIEW LETTERSdynamic limit. ... This work was also supported by the National... more
... years gluon thermodynamics has been studied extensively within the framework of lat-ticequantum chromodynamics. ... 198 5 VOLUME 54, NUMBER 2 I - - PHYSICAL REVIEW LETTERSdynamic limit. ... This work was also supported by the National Science Foundation, the US ...
Research Interests:
The electroweak model with one Higgs doublet is investigated when the mass of the Higgs particle is larger than the weak-interaction scale. It is shown that the SU(2) Higgs sector with spontaneously broken O(4) symmetry and perturbative... more
The electroweak model with one Higgs doublet is investigated when the mass of the Higgs particle is larger than the weak-interaction scale. It is shown that the SU(2) Higgs sector with spontaneously broken O(4) symmetry and perturbative gauge coupling becomes a trivial field theory at ...
Research Interests:
Research Interests:
... Monte Carlo calculation of the deconfining phase-transition temperature in lattice quantumchromodynamics without fermions. ... The dynamics of the Polyakov loop is determined by a three-dimensional effective ... This work was... more
... Monte Carlo calculation of the deconfining phase-transition temperature in lattice quantumchromodynamics without fermions. ... The dynamics of the Polyakov loop is determined by a three-dimensional effective ... This work was supported by National Science Foundation Grants ...