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تسجيل مستخدم جديدSpectrum of the open QCD flux tube and its effective string description
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تأليف
Bastian B. Brandt
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I perform a high precision measurement of the static quark-antiquark potential in three-dimensional ${rm SU}(N)$ gauge theory with $N=2$ to 6. The results are compared to the effective string theory for the QCD flux tube and I obtain continuum limit results for the string tension and the non-universal leading order boundary coefficient, including an extensive analysis of all types of systematic uncertainties. The magnitude of the boundary coefficient decreases with increasing $N$, but remains non-vanishing in the large-$N$ limit. I also test for the presence of possible contributions from rigidity or massive modes and compare the results for the string theory parameters to data for the excited states.
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We perform a high precision measurement of the static $qbar{q}$ potential in three-dimensional SU($N$) gauge theory with $N=2,3$ and compare the results to the potential obtained from the effective string theory. In particular, we show that the expon
ent of the leading order correction in $1/R$ is 4, as predicted, and obtain accurate results for the continuum limits of the string tension and the non-universal boundary coefficient $bar{b}_2$, including an extensive analysis of all types of systematic uncertainties. We find that the magnitude of $bar{b}_2$ decreases with increasing $N$, leading to the possibility of a vanishing $bar{b}_2$ in the large $N$ limit. In the standard form of the effective string theory possible massive modes and the presence of a rigidity term are usually not considered, even though they might give a contribution to the energy levels. To investigate the effect of these terms, we perform a second analysis, including these contributions. We find that the associated expression for the potential also provides a good description of the data. The resulting continuum values for $bar{b}_2$ are about a factor of 2 smaller than in the standard analysis, due to contaminations from an additional $1/R^4$ term. However, $bar{b}_2$ shows a similar decrease in magnitude with increasing $N$. In the course of this extended analysis we also obtain continuum results for the masses appearing in the additional terms and we find that they are around twice as large as the square root of the string tension in the continuum and compatible between SU(2) and SU(3) gauge theory. In the follow up papers we will extend our investigations to the large $N$ limit and excited states of the open flux tube.
In presence of a static pair of sources, the spectrum of low-lying states of any confining gauge theory in D space-time dimensions is described, at large source separations, by an effective string theory. Recently two important advances improved our
understanding of this effective theory. First, it was realized that the form of the effective action is strongly constrained by the requirement of the Lorentz invariance of the gauge theory, which is spontaneously broken by the formation of a long confining flux tube in the vacuum. This constraint is strong enough to fix uniquely the first few subleading terms of the action. Second, it has been realized that the first of these allowed terms - a quartic polynomial in the field derivatives - is exactly the composite field $Tbar{T}$, built with the chiral components, $T$ and $bar{T}$, of the energy-momentum tensor of the 2d QFT describing the infrared limit of the effective string. This irrelevant perturbation is quantum integrable and yields, through the thermodynamic Bethe Ansatz (TBA), the energy levels of the string which exactly coincide with the Nambu-Goto spectrum. In this talk we first review the general implications of these two results and then, as a test of the power of these methods, use them to construct the first few boundary corrections to the effective string action.
We review the current knowledge about the theoretical foundations of the effective string theory for confining flux tubes and the comparison of the predictions to pure gauge lattice data. A concise presentation of the effective string theory is provi
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The low energy excitation spectrum of the critical Wilson surface is discussed between the roughening transition and the continuum limit of lattice QCD. The fine structure of the spectrum is interpreted within the framework of two-dimensional conformal field theory.
We perform a high precision measurement of the spectrum of the QCD flux tube in three-dimensional $SU(2)$ gauge theory at multiple lattice spacings. We compare the results at large $qbar{q}$ separations $R$ to the spectrum predicted by the effective
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