Hierarchic chiral condensate

Akiba, Tomoya; Yanagida, Tsutomu T.

doi:10.1016/0370-2693(86)90385-0

Cited by 222 publications

(154 citation statements)

References 6 publications

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“…Moreover, the pre-conformal dynamics at flavor numbers just before the onset of conformal invariance might serve as a paradigm for the BSM model buildings that invokes non-perturbative mechanisms of electroweak symmetry breaking [3][4][5][6]. In such pre-conformal region, the coupling should vary little -should walk -with the scale, at…”

Section: B Pre-conformalitymentioning

confidence: 99%

One, two, zero: Scales of strong interactions

Lombardo

Miura

Silva

et al. 2014

Int. J. Mod. Phys. A

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We discuss our results on QCD with a number of fundamental fermions ranging from zero to sixteen. These theories exhibit a wide array of fascinating phenomena which have been under close scrutiny, especially in recent years, first and foremost is the approach to conformality. To keep this review focused, we have chosen scale generation, or lack thereof as a guiding theme, however the discussion will be set in the general framework of the analysis of the phases and phase transitions of strong interactions at zero and nonzero temperature. I. ADDING MATTER : QCD WITH AN ARBITRARY FLAVOR NUMBERUsual QCD dynamics is characterized by spontaneous symmetry breaking and dynamical mass generation, with the associated scale Λ QCD . However, when the number of flavors exceeds a critical number, an infra-red fixed point (IRFP) appears and prevents the coupling from growing large enough to break chiral symmetry. The theory is then scale invariant -even conformal invariant. In the intermediate region, the coupling 'walks' rather than runs between two typical scales -this is the phenomena of scale separation for which our results provide a preliminary evidence. From a general field theory viewpoint, the analysis of the phase diagram of strong interactions as a function of the number of flavor adds to our knowledge of the theoretical basis of strong interactions and their fundamental mechanisms. From a phenomenological viewpoint, this study deals with a class of models which might play a relevant role in model building beyond the standard model (BSM) [1][2][3][4][5][6], which explain the origin of mass using strong coupling mechanisms realized in QCD with a large number of flavors. All these topics are under active scrutiny both theoretically and experimentally A. ConformalityConformal invariance is anticipated to emerge in the non-Abelian gauge theory with many species (flavors) of fermions [59][60][61][62][63]. This is due to the IRFP for N f > N * f at a coupling which is not strong enough to break chiral symmetry: a second zero of the two-loop beta-function of a non-Abelian gauge theory implies, at least perturbatively, the appearance of IRFP conformal symmetry [59,60]. In color SU(3) gauge theory with N f massless fundamental fermions, the second zero appears at N f 8.05, before the loss of asymptotic freedom (LAF) B. Pre-conformalityThe direct inspection of theories at fixed N f is often inconclusive, especially close to the expected threshold N * f . An alternative approach to establish the existence of the conformal window is to (try to) observe directly the approach to conformality by monitoring the evolution of the results obtained in the broken phase as a function of N f .Moreover, the pre-conformal dynamics at flavor numbers just before the onset of conformal invariance might serve as a paradigm for the BSM model buildings that invokes non-perturbative mechanisms of electroweak symmetry breaking [3][4][5][6]. In such pre-conformal region, the coupling should vary little -should walk -with the scale, at

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Section: B Pre-conformalitymentioning

confidence: 99%

One, two, zero: Scales of strong interactions

Lombardo

Miura

Silva

et al. 2014

Int. J. Mod. Phys. A

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“…Walking technicolor models may overcome at least some of these obstacles, see e.g., [9][10][11][12][13][14][15][16][17] and references therein. These models exhibit an approximate scale invariance over a wide energy range as well as a proximity (in parameter space) to an infrared fixed point (IRFP).…”

Section: Jhep11(2014)035mentioning

confidence: 99%

Running coupling in the conformal window of large-Nf QCD

Hopfer

Fischer

Alkofer

2014

J. High Energ. Phys.

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Quantum Chromodynamics with a relatively large number of fundamentally charged quark flavours in the chiral limit is considered. A self-consistent solution of the quark, gluon and ghost propagator Dyson-Schwinger equations in Landau gauge exhibits a phase transition. Above the critical number of fermion flavours the non-perturbative running coupling develops a plateau over a wide momentum range, and the propagators follow a power law behaviour for these momenta. Hereby, the critical number of quark flavours depends crucially on the beyond-tree-level tensor structures of the quark-gluon vertex.

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“…(See Fig. 1.) TC with such a 'quasi' IRFP is nowadays termed as walking TC (WTC) [9,10,15]. It is expected that the quasi IRFP emerges in cases with a large number of techni-fermions in the fundamental representation or a small number of techni-fermions in the higher dimensional representations [6,16].…”

Section: Introductionmentioning

confidence: 99%

Analysis of techni-dilaton as a dark matter candidate

Choi

Hong

Matsuzaki

2012

J. High Energ. Phys.

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The almost conformal dynamics of walking technicolor (TC) implies the existence of the approximate scale invariance, which breaks down spontaneously by the condensation of anti-techni and techni-fermions. According to the Goldstone theorem, a spinless, parity-even particle, called technidilaton (TD), then emerges at low energy. If TC exhibits an extreme walking, TD mass, MTD, is parametrically much smaller than that of techni-fermions (∼ 1 TeV), while its decay constant is comparable to the cutoff scale of walking TC. We analyze the light, decoupled TD as a dark matter candidate and study cosmological productions of TD, both thermal and non-thermal, in the early Universe. The thermal population is governed dominantly by single TD production processes involving vertices breaking the scale symmetry, while the non-thermal population is by the vacuum misalignment and is accumulated via harmonic and coherent oscillations of misaligned classical TD fields. The non-thermal population turns out to be dominant and large enough to explain the abundance of presently observed dark matter, while the thermal population is highly suppressed due to the large TD decay constant. Several cosmological and astrophysical limits on the light, decoupled TD are examined to find that the mass MTD is constrained to be in a range, 0.01eV < ∼ MTD < ∼ 500 eV. From the combined constraints on cosmological productions and astrophysical observations, we find that the light, decoupled TD can be a good dark matter candidate with the mass around a few hundreds of eV for typical models of (extreme) walking TC. We finally mention possible designated experiments to detect the TD dark matter.

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Hierarchic chiral condensate

Cited by 222 publications

References 6 publications

One, two, zero: Scales of strong interactions

One, two, zero: Scales of strong interactions

Running coupling in the conformal window of large-Nf QCD

Analysis of techni-dilaton as a dark matter candidate

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