F. Darabi et al., Diffeomorphism algebra of a two-dimensional free massless scalar field with signature change, CLASS QUANT, 16(4), 1999, pp. 1417-1433
We study a model of free massless scalar fields on a two-dimensional cylind
er with a metric that admits a change of signature from a Lorentzian to a E
uclidean region. We take a long strip on the cylinder, denoted by the angle
theta, as the signature-changing region and show that, using specific junc
tion conditions, the energy spectrum depends on the angle a and in a sense
differs from the ordinary bosonic spectrum for low energies. Moreover, the
diffeomorphism algebra of the corresponding infinite conserved charges is d
ifferent from 'Virasoro' algebra and approaches it at higher energies where
as the central term, although modified, does not approach the central term
of 'Virasoro' algebra at higher energies.