2 research outputs found
On the SU(1,1) Thermal Group of Bosonic Strings and D-Branes
All possible Bogoliubov operators that generate the thermal transformations
in the Thermo Field Dynamics (TFD) form a SU(1,1) group. We discuss this
contruction in the bosonic string theory. In particular, the transformation of
the Fock space and string operators generated by the most general SU(1,1)
unitary Bogoliubov transformation and the entropy of the corresponding thermal
string are computed. Also, we construct the thermal -brane solution
generated by the SU(1,1) transformation in a constant Kalb-Ramond field and
compute its entropy.Comment: misprints correcte
Bosonic D-branes at finite temperature with an external field
Bosonic boundary states at finite temperature are constructed as solutions of
boundary conditions at for bosonic open strings with a constant gauge
field coupled to the boundary. The construction is done in the
framework of thermo field dynamics where a thermal Bogoliubov transformation
maps states and operators to finite temperature. Boundary states are given in
terms of states from the direct product space between the Fock space of the
closed string and another identical copy of it. By analogy with zero
temperature, the boundary states heve the interpretation of -brane at
finite temperature. The boundary conditions admit two different solutions. The
entropy of the closed string in a -brane state is computed and analysed. It
is interpreted as the entropy of the -brane at finite temperature.Comment: 21 pages, Latex, revised version with minor corrections and
references added, to be published in Phys. Rev.