scholarly journals A new method for the beta function in the chiral symmetry broken phase

2018 ◽  
Vol 175 ◽  
pp. 08027 ◽  
Author(s):  
Zoltan Fodor ◽  
Kieran Holland ◽  
Julius Kuti ◽  
Daniel Nogradi ◽  
Chik Him Wong
Keyword(s):  
Beyond Standard Model ◽  
Gauge Theory ◽  
Weak Coupling ◽  
Beta Function ◽  
New Method ◽  
Fermion Mass ◽  
Strong Coupling Regime ◽  
Composite Higgs ◽  
Perturbative Regime ◽  
Explicit Realization

We describe a new method to determine non-perturbatively the beta function of a gauge theory using lattice simulations in the p-regime of the theory. This complements alternative measurements of the beta function working directly at zero fermion mass and bridges the gap between the weak coupling perturbative regime and the strong coupling regime relevant to the mass spectrum of the theory. We apply this method to SU(3) gauge theory with two fermion flavors in the 2-index symmetric (sextet) representation. We find that the beta function is small but non-zero at the renormalized coupling value g2 = 6.7, consistent with our previous independent investigation using simulations directly at zero fermion mass. The model continues to be a very interesting explicit realization of the near-conformal composite Higgs paradigm which could be relevant for Beyond Standard Model phenomenology.

scholarly journals Construction of lattice Möbius domain wall fermions in the Schrödinger functional scheme

2018 ◽  
Vol 33 (01) ◽  
pp. 1850012
Author(s):  
Yuko Murakami ◽  
Ken-Ichi Ishikawa
Keyword(s):  
Perturbation Theory ◽  
Gauge Theory ◽  
Domain Wall ◽  
Beta Function ◽  
Boundary Operator ◽  
Tree Level ◽  
Domain Wall Fermions ◽  
Functional Scheme ◽  
Temporal Boundary ◽  
Optimal Type

In this paper, we construct the Möbius domain wall fermions (MDWFs) in the Schrödinger functional (SF) scheme for the SU(3) gauge theory by adding a boundary operator at the temporal boundary of the SF scheme setup. Using perturbation theory, we investigate the properties of several constructed MDWFs, including the optimal type domain wall, overlap, truncated domain wall, and truncated overlap fermions. We observe the universality of the spectrum of the effective four-dimensional operator at the tree-level, and fermionic contribution to the universal one-loop beta function is reproduced for MDWFs with a sufficiently large fifth-dimensional extent.

Anomalies in Strongly Coupled Harmonic Quantum Brownian Motion

2013 ◽  
Vol 20 (01) ◽  
pp. 1350002 ◽  
Author(s):  
F. Giraldi ◽  
F. Petruccione
Keyword(s):  
Time Evolution ◽  
Power Law ◽  
Weak Coupling ◽  
Inverse Power ◽  
Strong Coupling Regime ◽  
Weak Coupling Regime ◽  
Spectral Densities ◽  
Inverse Power Law ◽  
Critical Configurations ◽  
Long Time

The exact dynamics of a quantum damped harmonic oscillator coupled to a reservoir of boson modes has been formally described in terms of the coupling function, both in weak and strong coupling regime. In this scenario, we provide a further description of the exact dynamics through integral transforms. We focus on a special class of spectral densities, sub-ohmic at low frequencies, and including integrable divergencies referred to as photonic band gaps. The Drude form of the spectral densities is recovered as upper limit. Starting from special distributions of coherent states as external reservoir, the exact time evolution, described through Fox H-functions, shows long time inverse power law decays, departing from the exponential-like relaxations obtained for the Drude model. Different from the weak coupling regime, in the sub-ohmic condition, undamped oscillations plus inverse power law relaxations appear in the long time evolution of the observables position and momentum. Under the same condition, the number of excitations shows trapping of the population of the excited levels and oscillations enveloped in inverse power law relaxations. Similarly to the weak coupling regime, critical configurations give arbitrarily slow relaxations useful for the control of the dynamics. If compared to the value obtained in weak coupling condition, for strong couplings the critical frequency is enhanced by a factor 4.

PROBING TOPOLOGICAL FEATURES IN PERTURBATIVE CHERN-SIMONS GAUGE THEORY

1990 ◽  
Vol 05 (23) ◽  
pp. 1833-1839 ◽  
Author(s):  
WEI CHEN ◽  
G. W. SEMENOFF ◽  
YONG-SHI WU
Keyword(s):  
Perturbation Theory ◽  
Gauge Theory ◽  
Ward Identity ◽  
Beta Function ◽  
Dimensional Regularization ◽  
Coupling Constant ◽  
Topological Features ◽  
Chern Simons

The topological Chern-Simons gauge theory is studied in the framework of perturbation theory. Both dimensional and F2 regularizations are used. We demonstrate the vanishing of the beta function up to three loops, the absence of diffeomorphism anomaly in the calculation of two- and three-point functions, and the validity of a topological Ward identity by finite renormalization of the coupling constant. The regularization dependence of the finite renormalization and an ambiguity in the dimensional regularization are also discussed.

FRACTAL WILSON LOOP IN U(1) LATTICE GAUGE THEORY

1993 ◽  
Vol 08 (05) ◽  
pp. 445-457
Author(s):  
H. KRÖGER ◽  
S. LANTAGNE ◽  
K.J.M. MORIARTY
Keyword(s):  
Gauge Theory ◽  
Strong Coupling ◽  
Wilson Loop ◽  
Lattice Gauge Theory ◽  
Strong Coupling Regime ◽  
Lattice Gauge ◽  
Area Law

Recently, a fractal Wilson loop <FP> has been suggested to yield for non-compact SU(2) gauge theory an area law in the strong-coupling regime, while the standard Wilson loop <WP> yields a perimeter law. Here we consider non-compact U(1) gauge theory, compute the fractal Wilson loop analytically, and obtain a perimeter law for all coupling. We find that <FP> and <WP> coincide.

Boundary conditions, gauge fixing ambiguities and exact expectation values in U(1) lattice gauge theory

2016 ◽  
Vol 31 (08) ◽  
pp. 1650035
Author(s):  
Carlos Pinto
Keyword(s):  
Gauge Theory ◽  
Boundary Conditions ◽  
Weak Coupling ◽  
Lattice Gauge Theory ◽  
Exact Results ◽  
Feynman Gauge ◽  
Lattice Gauge ◽  
Coupling Approximation ◽  
Gauge Fixing ◽  
Weak Coupling Approximation

We analyze the interplay between gauge fixing and boundary conditions in two-dimensional U(1) lattice gauge theory. We show on the basis of a general argument that periodic boundary conditions result in an ill-defined weak coupling approximation but that the approximation can be made well-defined if the boundaries are fixed to zero. We confirm this result in the particular case of the Feynman gauge. We show that the zero momentum mode divergence in the propagator that appears in the Feynman gauge vanishes when the weak coupling approximation is well-defined. In addition we obtain exact results (for arbitrary coupling), including finite size corrections, for the partition function and for general one-point and two-point functions in the axial gauge under both periodic and zero boundary conditions and confirm these results numerically. The dependence of these objects on both lattice size and coupling constant is investigated using specific examples. These exact results may provide insight into similar gauge fixing issues in more complex models.

scholarly journals CONFORMAL HIGGS, OR TECHNI-DILATON — COMPOSITE HIGGS NEAR CONFORMALITY

2010 ◽  
Vol 25 (27n28) ◽  
pp. 5128-5144 ◽  
Author(s):  
KOICHI YAMAWAKI
Keyword(s):  
Goldstone Boson ◽  
Gluon Condensate ◽  
Bound State ◽  
Fermion Mass ◽  
Scale Invariant ◽  
Mass Generation ◽  
Composite Higgs ◽  
Njl Model ◽  
Holographic Approach ◽  
Intrinsic Scale

In contrast to the folklore that Technicolor (TC) is a "Higgsless theory", we shall discuss existence of a composite Higgs boson, Techni-Dilaton (TD), a pseudo-Nambu-Goldstone boson of the scale invariance in the Scale-invariant/Walking/Conformal TC (SWC TC) which generates a large anomalous dimension γm ≃ 1 in a wide region from the dynamical mass [Formula: see text] of the techni-fermion all the way up to the intrinsic scale ΛTC of the SWC TC (analogue of ΛQCD), where ΛTC is taken typically as the scale of the Extended TC scale Λ ETC : Λ TC ≃ Λ ETC ~ 103 TeV (≫ m). All the techni-hadrons have mass on the same order [Formula: see text], which in SWC TC is extremely smaller than the intrinsic scale Λ TC ≃ Λ ETC , in sharp contrast to QCD where both are of the same order. The mass of TD arises from the non-perturbative scale anomaly associated with the techni-fermion mass generation and is typically 500-600 GeV, even smaller than other techni-hadrons of the same order of [Formula: see text], in another contrast to QCD which is believed to have no scalar [Formula: see text] bound state lighter than other hadrons. We discuss the TD mass in various methods, Gauged NJL model via ladder Schwinger-Dyson (SD) equation, straightforward calculations in the ladder SD/ Bethe-Salpeter equation, and the holographic approach including techni-gluon condensate. The TD may be discovered in LHC.

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