ترغب بنشر مسار تعليمي؟ اضغط هنا

Perfect Lattice Actions for Quarks and Gluons

99   0   0.0 ( 0 )
 نشر من قبل ul
 تاريخ النشر 1995
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

We use perturbation theory to construct perfect lattice actions for quarks and gluons. The renormalized trajectory for free massive quarks is identified by blocking directly from the continuum. We tune a parameter in the renormalization group transformation such that for 1-d configurations the perfect action reduces to the nearest neighbor Wilson fermion action. The fixed point action for free gluons is also obtained by blocking from the continuum. For 2-d configurations it reduces to the standard plaquette action. Classically perfect quark and gluon fields, quark-gluon composite operators and vector and axial vector currents are constructed as well. Also the quark-antiquark potential is derived from the classically perfect Polyakov loop. The quark-gluon and 3-gluon perfect vertex functions are determined to leading order in the gauge coupling. We also construct a new block factor $n$ renormalization group transformation for QCD that allows to extend our results beyond perturbation theory. For weak fields it leads to the same perfect action as blocking from the continuum. For arbitrarily strong 2-d Abelian gauge fields the Manton plaquette action is classically perfect for this transformation.



قيم البحث

اقرأ أيضاً

We consider lattice field theories with topological actions, which are invariant against small deformations of the fields. Some of these actions have infinite barriers separating different topological sectors. Topological actions do not have the corr ect classical continuum limit and they cannot be treated using perturbation theory, but they still yield the correct quantum continuum limit. To show this, we present analytic studies of the 1-d O(2) and O(3) model, as well as Monte Carlo simulations of the 2-d O(3) model using topological lattice actions. Some topological actions obey and others violate a lattice Schwarz inequality between the action and the topological charge Q. Irrespective of this, in the 2-d O(3) model the topological susceptibility chi_t = l< Q^2 >/V is logarithmically divergent in the continuum limit. Still, at non-zero distance the correlator of the topological charge density has a finite continuum limit which is consistent with analytic predictions. Our study shows explicitly that some classically important features of an action are irrelevant for reaching the correct quantum continuum limit.
57 - Peter Levai 1997
We analyze recent results of SU(3) lattice QCD calculations with a phenomenological parametrization for the quark-gluon plasma equation of state based on a quasi-particle picture with massive quarks and gluons. At high temperature we obtain a good fi t to the lattice data using perturbative thermal quark and gluon masses from an improved HTL scheme. At temperatures close to the confinement phase transition the fitted masses increase above the perturbative value, and a non-zero (but small) bag constant is required to fit the lattice data.
We study the emergence of color superconductivity in the theory of the strong interaction at supranuclear densities. To this end, we follow the renormalization group (RG) flow of dense strong-interaction matter with two massless quark flavors from th e fundamental quark and gluon degrees of freedom at high energies down to the non-perturbative low-energy regime which is found to be governed by the dynamical formation of diquark states. With the strong coupling at the initial RG scale as the only input parameter, we compute the (chirally symmetric) scalar diquark condensate and analyze its scaling behavior over a wide range of the quark chemical potential. Approximations entering our computations are critically assessed. Since our approach naturally allows us to study the scale dependence of couplings, we also monitor the strength of couplings appearing in low-energy models of dense strong-interaction matter. The observed dependence of these couplings on the quark chemical potential may help to amend model studies in the future.
In this review article, we develop the perturbative framework for the calculation of hard scattering processes. We undertake to provide both a reasonably rigorous development of the formalism of hard scattering of quarks and gluons as well as an intu itive understanding of the physics behind the scattering. We emphasize the importance of logarithmic corrections as well as power counting of the strong coupling constant in order to understand the behavior of hard scattering processes. We include rules of thumb as well as official recommendations, and where possible seek to dispel some myths. Experiences that have been gained at the Fermilab Tevatron are recounted and, where appropriate, extrapolated to the LHC.
We test a set of lattice gauge actions for QCD that suppress small plaquette values and in this way also suppress transitions between topological sectors. This is well suited for simulations in the epsilon-regime and it is expected to help in numerical simulations with dynamical quarks.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا