Glueball masses and other physical properties of SU(N) gauge theories in D=3+1: a review of lattice results for theorists

We summarise what lattice simulations have to say about the physical properties of continuum SU(N) gauge theories in 3+1 dimensions. The quantities covered are: the glueball mass spectrum, the confining string tension, the temperature at which the theory becomes deconfined, the topological susceptibility, the value of the scale Lambda{MS-bar} that governs the rate at which the coupling runs and the r0 parameter that characterises the static quark potential at intermediate distances.Comment: LaTeX, 28 pages, not submitted for publicatio

The induced capacity and Choquet integral monotone convergece

Given a probability measure over a state space, a partial collection (sub-$\sigma$-algebra) of events whose probabilities are known, induces a capacity over the collection of all possible events. The \emph{induced capacity} of an event $F$ is the probability of the maximal (with respect to inclusion) event contained in $F$ whose probability is known. The Choquet integral with respect to the induced capacity coincides with the integral with respect to a \emph{probability specified on a sub-algebra} (Lehrer \cite{Lehrer2}). We study Choquet integral monotone convergence and apply the results to the integral with respect to the induced capacity. The paper characterizes the properties of sub-$\sigma$-algebras and of induced capacities which yield integral monotone convergence

Large Nc physics from the lattice

I summarise what lattice methods can contribute to our understanding of the phenomenology of QCD at large Nc and describe some recent work on the physics of SU(Nc) gauge theories. These non-perturbative calculations show that there is indeed a smooth Nc -> infinity limit and that it is achieved by keeping g.g.Nc fixed, confirming the usual diagrammatic analysis. The lattice calculations support the crucial assumption that the theory remains linearly confining at large Nc. Moreover we see explicitly that Nc=3 is `close to' Nc=infinity for many physical quantities. We comment on the fate of topology and the deconfining transition at large Nc. We find that multiple confining strings are strongly bound. The string tensions, K(k), of these k-strings are close to the M(-theory)QCD-inspired conjecture as well as to `Casimir scaling' with the most accurate recent calculations favouring the former. We point out that closed k-strings provide a natural way for non-perturbative effects to introduce O(1/Nc) corrections into the pure gauge theory, in contradiction to the conventional diagrammatic expectation.Comment: 10 pages. Invited talk, The Phenomenology of Large-Nc QCD, to be published Proceedings of the Institute of Nuclear Theor

Large N

I review some of the things we have learned about large N gauge theories (and QCD at N=oo) from lattice calculations in recent years. I point to some open problems.Comment: Plenary talk at Lattice 200

Universality, Scaling and Topology with a Modified Lattice Action

We examined the effect of a complete suppression of a lattice artifact, the negative plaquettes, on physical quantities, such as the critical temperature, the string tension, the topological charge, glueball masses, and their ratios.Comment: 3 pages, self unpacking uuencoded PostScript file, contribution to conference LATTICE '9

Stable and quasi-stable confining SU(N) strings in D=2+1

We investigate the low-lying spectrum of closed confining flux-tubes that wind around a spatial torus in D=2+1 and carry flux in different representations of SU(N). We focus on our most recent calculations for N=6 and {\beta}=171, where the calculated low-energy physics is very close to the continuum and large-N limits. We investigate the adjoint, 84, 120, k = 2A, 2S and k = 3A, 3M, 3S representations and show that the corresponding flux-tubes do exist. Similarly to the results for the fundamental representation, the ground state of a flux-tube with momentum along its axis appears to be well described by Nambu-Goto all the way down to very short tubes. In contrast, excited states have much larger deviations from Nambu-Goto. We discuss whether these states are non-string-like and associated with excitations of massive flux-tube modes.Comment: 7 pages, 4 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July-3 August 2013, Mainz, German

Structure and properties of the vacuum of the Twisted Eguchi-Kawai model

We investigate numerically the phase structure of the Twisted Eguchi-Kawai (TEK) model in four dimensions. In the numerical simulations of the zero temperature TEK model (using a symmetric twist) we observe the existence of new phases that break its centre symmetry at intermediate lattice couplings and for large SU(N) gauge groups. This effect can be explained by the contribution of diagonal configurations with collapsed eigenvalues, which are particular cases of ``generalised fluxons''. We also investigate finite temperature versions of the TEK model using anisotropic lattice couplings, where in particular we find van Baal fluxons contributing at large anisotropies.Comment: 7 pages, 3 figures, talk presented at Lattice 2007 (Theoretical developments), Regensburg, July 30-August 04, 2007; v2, minor changes and references adde

The pressure and a possible hidden Hagedorn transition at large-N

In the first part of this contribution we present a numerical study motivated by recent attempts to understand the nonperturbative aspects of QCD at temperatures T~ a few times the deconfinement temperature Tc. We focus on the pure gauge theory, and ask whether the deficit in pressure and entropy, with respect to their free-gas values, is particular to SU(3). We find that the deficit in SU(4),SU(8) for T>= 2Tc,1.6 Tc, respectively, is remarkably close to that of SU(3). This suggests a similar deficit for SU(oo), which is fortunate since this theory is simpler, and can serve to constrain the possible dynamics underlying the deficits. In the second part we seek for signs of a Hagedorn temperature T_H in pure lattice SU(N) gauge theories with N=8,10,12. Since one expects T_H>Tc, we measure masses of strings in the metastable confined phase above Tc, and extrapolatethem to zero to estimate T_H. For SU(12) we find that T_H/Tc=1.116(9), when we extrapolate with a critical exponentof the three dimensional XY model, which seems to be preferred over a mean field exponent by our data.Comment: 6 pages, 3 figures, Contributed to 23rd International Symposium on Lattice Field Field: Lattice 2005, Trinity College, Dublin, Ireland, 25-30 Jul 200

Glueball Spectra of SU(2) Gauge Theories in 3 and 4 Dimensions: A Comparison with the Isgur-Paton Flux Tube Model

We use the results of recent lattice calculations to obtain (part of) the mass spectrum of continuum SU(2) gauge theory in both 2+1 and 3+1 dimensions. We compare these spectra to the predictions of the Isgur-Paton flux tube model for glueballs. We use this comparison to test the reliability of different aspects of the model and also to learn which aspects of the lattice calculations it is important to improve upon.Comment: 8 pages, Plain TEX, 1 table and 3 figures on ps-files are appended as a tar-compressed, uuencoded fil

SO(2N) and SU(N) gauge theories

We present our preliminary results of SO(2N) gauge theories, approaching the large-N limit. SO(2N) theories may help us to understand QCD at finite chemical potential since there is an orbifold equivalence between SO(2N) and SU(N) gauge theories at large-N and SO(2N) theories do not have the sign problem present in QCD. We consider the string tensions, mass spectra, and deconfinement temperatures in the SO(2N) pure gauge theories in 2+1 dimensions, comparing them to their corresponding SU(N) theories.Comment: 7 pages, 6 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German