246 research outputs found
`Analytic Continuation' of N=2 Minimal Model
In this paper we discuss what theory should be identified as the `analytic
continuation' with of the minimal model with
the central charge . We clarify how the elliptic
genus of the expected model is written in terms of {\em holomorphic\/} linear
combinations of the `modular completions' introduced in [arXiv:1012.5721
[hep-th]] in the -supercoset theory. We further discuss how
this model could be interpreted as a kind of {\em `compactified'} model of the
-supercoset in the -sector, in which
only the discrete spectrum appears in the torus partition function and the
potential IR-divergence due to the non-compactness of target space is removed.
We also briefly argue on possible definitions of the sectors with other spin
structures.Comment: 1+29 pages, no figur
Non-geometric Backgrounds Based on Topological Interfaces
We study simple models of the world-sheet CFTs describing non-geometric
backgrounds based on the topological interfaces, the `gluing condition' of
which imposes T-duality- or analogous twists. To be more specific, we start
with the torus partition function on a target space S^1 [base] x (S^1 x S^1)
[fiber] with rather general values of radii. The fiber CFT is defined by
inserting the twist operators consisting of the topological interfaces which
lie along the cycles of the world-sheet torus according to the winding numbers
of the base circle. We construct the partition functions involving such duality
twists. The modular invariance is achieved straightforwardly, whereas
`unitarization' is generically necessary to maintain the unitarity. We
demonstrate it in the case of the equal fiber radii. The resultant models are
closely related to the CFTs with the discrete torsion. The unitarization is
also physically interpreted as multiple insertions of the twist/interface
operators along various directions.Comment: 32 pages, no figures; (v2) comments and explanations adde
On the String Actions for the Generalized Two-dimensional Yang-Mills Theories
We study the structures of partition functions of the large generalized
two-dimensional Yang-Mills theories () by recasting the higher Casimirs.
We clarify the appropriate interpretations of them and try to extend the
Cordes-Moore-Ramgoolam's topological string model describing the ordinary
\cite{CMR} to those describing . We present the expressions of
the appropriate operators to reproduce the higher Casimir terms in . The
concept of ''deformed gravitational descendants'' will be introduced for this
purpose.Comment: 12 pages, no figures, version to be published in Mod.Phys.Lett.
Non-supersymmetric D-branes with Vanishing Cylinder Amplitudes in Asymmetric Orbifolds
We study the type II string vacua with chiral space-time SUSY constructed as
asymmetric orbifolds of torus and compactifications. Despite the fact
that all the D-branes are non-BPS in any chiral SUSY vacua, we show that the
relevant non-geometric vacua of asymmetric orbifolds allow rather generally
configurations of D-branes which lead to vanishing cylinder amplitudes,
implying the bose-fermi cancellation at each mass level of the open string
spectrum. After working on simple models of toroidal asymmetric orbifolds, we
focus on the asymmetric orbifolds of , where is described by a general SCFT with defined by the
Gepner construction for . Even when the modular invariant partition
functions in the bulk remain unchanged, the spectra of such non-BPS D-branes
with the bose-fermi cancellation can vary significantly according to the choice
of orbifolding.Comment: 32 pages, no figures; (v2) comments and discussion added on
properties of D-brane
Boundary States of D-branes in AdS_3 Based on Discrete Series
We study D-branes in the Lorentzian AdS_3 background from the viewpoint of
boundary states, emphasizing the role of open-closed duality in string theory.
Employing the world sheet with Lorentzian signature, we construct the Cardy
states with the discrete series. We show that they are compatible with (1)
unitarity and normalizability, and (2) the spectral flow symmetry, in the open
string spectrum. We also discuss their brane interpretation. We further show
that in the case of superstrings on AdS_3 x S^3 x T^4, our Cardy states yield
an infinite number of physical BPS states in the open string channel, on which
the spectral flows act consistently.Comment: 27 pages, latex, no figures, v2: we discuss on the single cover of
AdS_3 rather than the universal cover, reference added, v3: Appendix B and
reference adde
Fractional Strings in (p,q) 5-brane and Quiver Matrix String Theory
We study the (p,q)5-brane dynamics from the viewpoint of Matrix string theory
in the T-dualized ALE background. The most remarkable feature in the
(p,q)5-brane is the existence of ``fractional string'', which appears as the
instanton of 5-brane gauge theory. We approach to the physical aspects of
fractional string by means of the two types of Matrix string probes: One of
which is that given in hep-th/9710065. As the second probe we present the
Matrix string theory describing the fractional string itself. We calculate the
moduli space metrics in the respective cases and argue on the specific
behaviors of fractional string. Especially, we show that the ``joining''
process of fractional strings can be realized as the transition from the
Coulomb branch to the Higgs branch of the fractional string probe. In this
argument, we emphasize the importance of some monodromies related with the
theta-angle of the 5-brane gauge theory.Comment: 21 pages, Late
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