512 research outputs found
Closed String Thermal Torus From Thermo Field Dynamics
In this Letter a topological interpretation for the string thermal vacuum in
the Thermo Field Dynamics (TFD) approach is given. As a consequence, the
relationship between the Imaginary Time and TFD formalisms is achieved when
both are used to study closed strings at finite temperature. The TFD approach
starts by duplicating the system's degrees of freedom, defining an auxiliary
(tilde) string. In order to lead the system to finite temperature a Bogoliubov
transformation is implemented. We show that the effect of this transformation
is to glue together the string and the tilde string to obtain a torus. The
thermal vacuum appears as the boundary state for this identification. Also,
from the thermal state condition, a Kubo-Martin-Schwinger condition for the
torus topology is derived.Comment: 14 pages, revtex4, changes in the text and references. Version to be
published in Physics Letters
TFD Approach to Bosonic Strings and -branes
In this work we explain the construction of the thermal vacuum for the
bosonic string, as well that of the thermal boundary state interpreted as a
-brane at finite temperature. In both case we calculate the respective
entropy using the entropy operator of the Thermo Field Dynamics Theory. We show
that the contribution of the thermal string entropy is explicitly present in
the -brane entropy. Furthermore, we show that the Thermo Field approach
is suitable to introduce temperature in boundary states.Comment: 6 pages, revtex, typos are corrected. Prepared for the Second
Londrina Winter School-Mathematical Methods in Physics, August 25-30, 2002,
Londrina-Pr, Brazil. To appear in a special issue of IJMP
General Unitary TFD Formulation for Superstrings
A generalization of the Thermo Field Dynamics (TFD) for fermionic degrees of
freedom is proposed. Such a generalization follows a previous one where the
SU(1,1) thermal group was used to obtain the closed bosonic string at finite
temperature. The SU(2) thermal group is introduced to construct a general
thermal Bogoliubov transformation to get the type IIB superstring at finite
temperature.Comment: 9 pages, revitex4, minor corrections. Contribution to Fourth
International Winter Conference on Mathematical Methods in Physics, 09 - 13
August 2004, Centro Brasileiro de Pesquisas Fisicas (CBPF/MCT), Rio de
Janeiro, Brazi
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