St-Petersburg State University Research Institute of Physics Faculty of Physics High Energy and Elementary Particles Physics
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                We   review   the  similarities
between   the   effective   chiral  Lagrangian,
relevant  for  low-energy  strong interactions,
and  the  Einstein-Hilbert action. We use these
analogies   to  suggest  a  specific  mechanism
whereby  gravitons  would  emerge  as Goldstone
bosons  of  a  global  SO(D)  X  GL(D) symmetry
broken  down  to SO(D) by fermion condensation.
We  propose a two-dimensional toy model where a
dynamical   zwei-bein   is   generated  from  a
topological  theory  without  any  pre-existing
metric  structure, the space being endowed only
with  an  affine  connection.  A metric appears
only  after  the  symmetry  breaking;  thus the
notion of distance is an induced effective one.
In  spite of several non-standard features this
simple  toy  model appears to be renormalizable
and  at  long  distances  is  described  by  an
effective  Lagrangian  that corresponds to that
of  two-dimensional gravity (Liouville theory).
The induced cosmological constant is related to
the  dynamical  mass  M acquired by the fermion
fields  in  the breaking, which also acts as an
infrared regulator. The low-energy expansion is
valid  for momenta k >M, i.e. for supra-horizon
scales.   We   briefly   discuss   a   possible
implementation  of  a similar mechanism in four
dimensions 
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March 2009