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@TECHREPORT{Mack:589094,
      author       = {Mack, G. and Kalkreuter, T. and Palma, G. and Speh, M.},
      title        = {{E}ffective field theories},
      number       = {hep-lat/9205013},
      reportid     = {PUBDB-2023-05051, hep-lat/9205013. DESY-92-070},
      pages        = {45},
      year         = {1992},
      note         = {Published in Proceedings of the 31th Internationale
                      Universitatswochen fur Kern- und Teilchenphysik, Schladming,
                      Austria, 1992. Edited by H. Gausterer and C.B. Lang. Berlin,
                      Germany, Springer-Verlag, 1992. (Lecture Notes in Physics,
                      409) pp. 205-250. 45 pages, 9 figs., preprint DESY 92-070
                      (figs. 3-9 added in ps format)},
      abstract     = {Effective field theories encode the predictions of a
                      quantum field theory at low energy. The effective theory has
                      a fairly low ultraviolet cutoff. As a result, loop
                      corrections are small, at least if the effective action
                      contains a term which is quadratic in the fields, and
                      physical predictions can be read straight from the effective
                      Lagrangean. Methods will be discussed how to compute an
                      effective low energy action from a given fundamental action,
                      either analytically or numerically, or by a combination of
                      both methods. Basically,the idea is to integrate out the
                      high frequency components of fields. This requires the
                      choice of a 'blockspin',i.e. the specification of a low
                      frequency field as a function of the fundamental fields.
                      These blockspins will be the fields of the effective field
                      theory. The blockspin need not be a field of the same type
                      as one of the fundamental fields, and it may be composite.
                      Special features of blockspins in nonabelian gauge theories
                      will be discussed in some detail. In analytical work and in
                      multigrid updating schemes one needs interpolation kernels
                      $\mathcal A$ from coarse to fine grid in addition to the
                      averaging kernels $C$ which determines the blockspin. A
                      neural net strategy for finding optimal kernels is
                      presented. Numerical methods are applicable to obtain
                      actions of effective theories on lattices of finite volume.
                      The constraint effective potential) is of particular
                      interest. In a Higgs model it yields the free energy,
                      considered as a function of a gauge covariant magnetization.
                      Its shape determines the phase structure of the theory. Its
                      loop expansion with and without gauge fields can be used to
                      determine finite size corrections to numerical data.},
      keywords     = {talk (INSPIRE) / field theory: Euclidean (INSPIRE) /
                      effective action (INSPIRE) / effective potential (INSPIRE) /
                      perturbation theory: higher-order (INSPIRE) /
                      renormalization group (INSPIRE) / field theory: scalar
                      (INSPIRE) / gauge field theory: Yang-Mills (INSPIRE) / block
                      spin transformation (INSPIRE) / fermion (INSPIRE) / lattice
                      field theory (INSPIRE) / Higgs model (INSPIRE) / neural
                      network (INSPIRE) / bibliography (INSPIRE)},
      cin          = {DESY(-2012)},
      cid          = {$I:(DE-H253)DESY_-2012_-20170516$},
      pnm          = {899 - ohne Topic (POF4-899)},
      pid          = {G:(DE-HGF)POF4-899},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)29},
      doi          = {10.3204/PUBDB-2023-05051},
      url          = {https://bib-pubdb1.desy.de/record/589094},
}