Study of the running coupling constant in 10-flavor QCD with the Schroedinger functional method

Yamada, Norikazu; Uno, S.; Takeda, Shinji; Hayakawa, Masashi; Ishikawa, K-I.; Osaki, Y.

doi:10.48550/arxiv.0910.4218

Cited by 3 publications

(4 citation statements)

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“…It is therefore interesting to ask what these criteria predict for the non-supersymmetric theories that are being investigated using lattice techniques. These theories include SU(2) and SU(3) with a 'large' number of fundamental (F) fermions [14][15][16][17][18][19], SU(2) with 2 adjoint (Adj) fermions [9][10][11][12][13], and SU(3) with 2 sextet (2S) fermions [20][21][22][23][24]. These theories are part of the larger family of theories whose properties are shown in Figs.…”

Section: Comparing With Lattice Data and Other Methodsmentioning

confidence: 99%

“…While the lower boundary of the conformal window is of theoretical interest in its own right, its current importance arises from its central role in technicolour models [4] with walking dynamics [5,6] and, in particular, of more recent models such as minimal walking technicolour [7] and conformal technicolour [8]. Therefore, a lot of effort has recently gone into exploring this region, using both lattice [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and approximate analytical [25][26][27][28][29][30][31][32][33][34][35][36][37] methods. In principle the former should provide a definitive answer: however, it has become clear, from the pioneering lattice calculations, that identifying and characterising (near-)conformal theories on a lattice is a very challenging problem.…”

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confidence: 99%

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Delineating the conformal window

2011

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We identify and characterise the conformal window in gauge theories relevant for beyond the standard model building, e.g. Technicolour, using the criteria of metric confinement and causal analytic couplings, which are known to be consistent with the phase diagram of supersymmetric QCD from Seiberg duality. Using these criteria we find perturbation theory to be consistent throughout the predicted conformal window for several of these gauge theories and we discuss recent lattice results in the light of our findings.Comment: 8 pages, 4 figure

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Section: Comparing With Lattice Data and Other Methodsmentioning

confidence: 99%

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confidence: 99%

Delineating the conformal window

2011

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“…number of simulations of QCD with N f fundamental quarks, with N f large enough that conformal or walking behaviour might be expected [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. While progress has been made, the boundary value for N f is still uncertain.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of lattice QCD with 2 flavors of color-sextet quarks: A model of walking/conformal technicolor

Kogut

Sinclair

2010

Phys. Rev. D

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QCD with two flavours of massless colour-sextet quarks is considered as a model for conformal/walking Technicolor. If this theory possess an infrared fixed point, as indicated by 2-loop perturbation theory, it is a conformal(unparticle) field theory.If, on the other hand, a chiral condensate forms on the weak-coupling side of this would-be fixed point, the theory remains confining. The only difference between such a theory and regular QCD is that there is a range of momentum scales over which the coupling constant runs very slowly (walks). In this first analysis, we simulate the lattice version of QCD with two flavours of staggered quarks at finite temperatures on lattices of temporal extent N t = 4 and 6. The deconfinement and chiral-symmetry restoration couplings give us a measure of the scales associated with confinement and chiral-symmetry breaking. We find that, in contrast to what is seen with fundamental quarks, these transition couplings are very different. β = 6/g 2 for each of these transitions increases significantly from N t = 4 and N t = 6 as expected for the finite temperature transitions of an asymptotically-free theory. This suggests a walking rather than a conformal behaviour, in contrast to what is observed with Wilson quarks. In contrast to what is found for fundamental quarks, the deconfined phase exhibits states in which the Polyakov loop is oriented in the directions of all three cube roots of unity. At very weak coupling the states with complex Polyakov loops undergo a transition to a state with a real, negative Polyakov loop.2

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“…Such theories can avoid the phenomenological problems which plague other (extended-)Technicolor theories. [3][4][5][6] While many studies have used fermions in the fundamental representation, with large numbers of flavours, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] we are concentrating on higher representations of the colour group (in particular the symmetric tensor), where conformality/walking can be achieved at much lower N f . There have been some studies with SU (2) colour with two adjoint (symmetric tensor) fermions.…”

Section: Introductionmentioning

confidence: 99%

Lattice Gauge Theory and (Quasi)-Conformal Technicolor

Sinclair

Kogut

2011

Strong Coupling Gauge Theories in LHC Era

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QCD with 2 flavours of massless colour-sextet quarks is studied as a theory which might exhibit a range of scales over which the running coupling constant evolves very slowly (walks). We simulate lattice QCD with 2 flavours of sextet staggered quarks to determine whether walks, or if it has an infrared fixed point, making it a conformal field theory. Our initial simulations are performed at finite temperatures $T=1/N_ta$ ($N_t=4$ and $N_t=6$), which allows us to identify the scales of confinement and chiral-symmetry breaking from the deconfinement and chiral-symmetry restoring transitions. Unlike QCD with fundamental quarks, these two transitions appear to be well-separated. The change in coupling constants at these transitions between the two different temporal extents $N_t$, is consistent with these being finite temperature transitions for an asymptotically free theory, which favours walking behaviour. In the deconfined phase, the Wilson Line shows a 3-state signal. Between the confinement and chiral transitions, there is an additional transition where the states with Wilson Lines oriented in the directions of the complex cube roots of unity disorder into a state with a negative Wilson Line.Comment: 7 pages Latex, 3 postscript figures. Talk presented by DKS at SCGT09, Nagoya, Japa

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Study of the running coupling constant in 10-flavor QCD with the Schroedinger functional method

Cited by 3 publications

References 0 publications

Delineating the conformal window

Delineating the conformal window

Thermodynamics of lattice QCD with 2 flavors of color-sextet quarks: A model of walking/conformal technicolor

Lattice Gauge Theory and (Quasi)-Conformal Technicolor

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