Search results for " lattice gauge theory"
showing 10 items of 23 documents
Spectrum of the QCD flux tube in 3d SU(2) lattice gauge theory
2009
Abstract Evidence from the lattice suggests that formation of a flux tube between a q q ¯ pair in the QCD vacuum leads to quark confinement. For large separations between the quarks, it is conjectured that the flux tube has a behavior similar to an oscillating bosonic string, supported by lattice data for the groundstate q q ¯ potential. We measure the excited states of the flux tube in 3d SU ( 2 ) gauge theory with three different couplings inside the scaling region. We compare our results to predictions of effective string theories.
Spectrum of SU(2) gauge theory with two fermions in the adjoint representation
2008
We present preliminary results of lattice simulations of SU(2) gauge theory with two Wilson fermions in the adjoint representation. This theory has recently attracted considerable attention because it might possess an infrared fixed point (or an almost-fixed-point), and hence be a candidate for a walking technicolor theory. In this work we study the particle spectrum of the theory, and compare it with more familiar spectrum of the theory with SU(2) gauge fields and two flavors of fundamental representation fermions.
Abelian charges in a nonabelian Yang-Mills theory from the stratification of the space of gauge potentials
1992
Abstract The Abelian charges in a non-Abelian Yang-Mills-Dirac theory arising from the reduction of the structure group are studied. They are defined by the concept of the stabilizer gauge transformations. Their properties are investigated. The relationship between the whole class of stabilizers and the stratification of the space of gauge potentials is given. The effect of the spontaneous symmetry breaking mechanism on these charges is discussed.
Spin-dependent potentials from lattice QCD
2006
The spin-dependent corrections to the static inter-quark potential are phenomenologically relevant to describing the fine and hyperfine spin splitting of the heavy quarkonium spectra. We investigate these corrections, which are represented as the field strength correlators on the quark-antiquark source, in SU(3) lattice gauge theory. We use the Polyakov loop correlation function as the quark-antiquark source, and by employing the multi-level algorithm, we obtain remarkably clean signals for these corrections up to intermediate distances of around 0.6 fm. Our observation suggests several new features of the corrections.
Quantum simulation of gauge potentials with cold atoms in optical lattices: a tunable platform for relativistic fermions and axions
2014
We offer here a brief introduction to the idea of quantum simulations with cold atomic gases, with focus on the recent efforts towards artificial gauge potentials and fields. This is mainly intended as a sort of “pedestrian guide” for people not yet working in the field, but curious to get a first contact with it; longer and deeper reviews are addressed for deeper details. As a special case, we focus here on reviewing some own previous contributions about a flexible toolbox based on bichromatic optical lattices and Raman assisted tunnelling. Such a scheme would allow good control on the mass and kinetic terms of a lattice Hamiltonian in different effective dimensions. If realized with fermi…
Hamiltonian lattice QCD at finite density: equation of state in the strong coupling limit
2001
The equation of state of Hamiltonian lattice QCD at finite density is examined in the strong coupling limit by constructing a solution to the equation of motion corresponding to an effective Hamiltonian describing the ground state of the many body system. This solution exactly diagonalizes the Hamiltonian to second order in field operators for all densities and is used to evaluate the vacuum energy density from which we obtain the equation of state. We find that up to and beyond the chiral symmetry restoration density the pressure of the quark Fermi sea can be negative indicating its mechanical instability. Our result is in qualitative agreement with continuum models and should be verifiabl…
The Higgs Mechanism and Spontaneous Symmetry Breaking
2002
As is well known all gauge bosons of a pure Yang-Mills theory are necessarily massless. This is so because any ad-hoc mass term such as $$ m_i^2 A_\mu ^{(i)} A^{(i)\mu } or \sum\limits_{ik} {M_{ik} } A_\mu ^{(i)} A^{(k)\mu } $$ is incompatible with local gauge invariance. It is saidthat W. Pauli hadd evelopednonab elian gauge theory for himself (or knew about it from the work of H. Weyl and O. Klein) before the work of C.N. Yang and R. Mills (1954) but dismissedit because he hadrealizedthat the gauge particles wouldall be massless. As there was only one massless spin-1 particle known at the time (the photon) nonabelian gauge theory was to be rejectedon physical grounds. The few facts that w…
The pinch technique at two loops
1999
It is shown that the fundamental properties of gauge-independence, gauge-invariance, unitarity, and analyticity of the $S$-matrix lead to the unambiguous generalization of the pinch technique algorithm to two loops.
Gauge-invariant proper self-energies and vertices in gauge-theories with broken symmetry
1990
Using the pinch technique, we show how to recover, from the {ital S} matrix of a spontaneously broken non-Abelian gauge theory, proper self-energies and vertices which are fully gauge invariant when one or more momenta are off shell. Explicit calculations are carried out at the one-loop level for gauge-boson self-energies and fermion--gauge-boson vertices in a simple SU(2) gauge theory with a Higgs boson. The same technique allows us to calculate, at one-loop order, a neutrino electromagnetic form factor which is gauge invariant at all photon momenta, thus resolving a long-standing problem. We show how massless Goldstone bosons, not present in the {ital S} matrix, must be introduced into Gr…
Dynamical twisted mass fermions with light quarks: simulation and analysis details
2008
In a recent paper [hep-lat/0701012] we presented precise lattice QCD results of our European Twisted Mass Collaboration (ETMC). They were obtained by employing two mass-degenerate flavours of twisted mass fermions at maximal twist. In the present paper we give details on our simulations and the computation of physical observables. In particular, we discuss the problem of tuning to maximal twist, the techniques we have used to compute correlators and error estimates. In addition, we provide more information on the algorithm used, the autocorrelation times and scale determination, the evaluation of disconnected contributions and the description of our data by means of chiral perturbation theo…