150 research outputs found
Extended QCD(2) from dimensional projection of QCD(4)
We study an extended QCD model in (1+1) dimensions obtained from QCD in 4D by
compactifying two spatial dimensions and projecting onto the zero-mode
subspace. We work out this model in the large limit and using light cone
gauge but keeping the equal-time quantization. This system is found to induce a
dynamical mass for transverse gluons -- adjoint scalars in QCD(2), and to
undergo a chiral symmetry breaking with the full quark propagators yielding
non-tachyonic, dynamical quark masses, even in the chiral limit. We study
quark-antiquark bound states which can be classified in this model by their
properties under Lorentz transformations inherited from 4D. The scalar and
pseudoscalar sectors of the theory are examined and in the chiral limit a
massless ground state for pseudoscalars is revealed with a wave function
generalizing the so called 't Hooft pion solution.Comment: JHEP class, 16 pages, 3 figures. Change in the title, some
improvements in section 2, minors changes and comments added in introduction
and conclusions. References added. Version appearing in JHE
Linear Sigma Models of H and KK Monopoles
We propose a gauged linear sigma model of k H-monopoles. We also consider the
T-dual of this model describing KK-monopoles and clarify the meaning of
"winding coordinate" studied recently in hep-th/0507204.Comment: 13 pages, lanlmac; V3:added argument on the nature of disk instanto
Properties of Intersecting p-branes in Various Dimensions
General properties of intersecting extremal p-brane solutions of gravity
coupled with dilatons and several different d-form fields in arbitrary
space-time dimensions are considered. It is show that heuristically expected
properties of the intersecting p-branes follow from the explicit formulae for
solutions. In particular, harmonic superposition and S-duality hold for all
p-brane solutions. Generalized T-duality takes place under additional
restrictions on the initial theory parameters .Comment: 14 pages, RevTeX, misprints are corrected and more Comments are
added, information about one of the authors (M.G.I.) available at
http://www.geocities.com/CapeCanaveral/Lab/419
Thermal Partition Functions for S-branes
We calculate the thermal partition functions of open strings on the S-brane
backgrounds (the bouncing or rolling tachyon backgrounds) both in the bosonic
and superstring cases. According to hep-th/0302146, we consider the discretized
temperatures compatible with the pure imaginary periodicity of tachyon
profiles. The ``effective Hagedorn divergence'' is shown to appear no matter
how low temperature is chosen (including zero-temperature). This feature is
likely to be consistent with the large rate of open string pair production
discussed in hep-th/0209090 and also emission of closed string massive modes
hep-th/0303139. We also discuss the possibility to remove the divergence by
considering the space-like linear dilaton backgrounds as in hep-th/0306132.Comment: 33 pages, no figure; v2 typos corrected, a reference adde
Wormhole phase in the RST model
We show that the RST model describing the exactly soluble black hole model
can have a dynamical wormhole solution along with an appropriate boundary
condition. The necessary exotic matter which is usually negative energy density
is remarkably produced by the quantization of the infalling matter fields. Then
the asymptotic geometry in the past is two-dimensional anti-de Sitter(AdS),
which implies the exotic matter is negative. As time goes on, the wormhole
eventually evolves into the black hole and its Hawking radiation appears. The
throat of the static RST wormhole is lower-bounded but in the presence of
infalling matter it collapses to a black hole.Comment: v1. REVTeX3, 12 pages and 1 figure; v2. JHEP3, 10 pages and 1 figure,
version published in JHE
A silence black hole: Hawking radiation at the Hagedorn temperature
We compute semi-classically the Hawking emission for different types of black
hole in type II string theory. In particular we analyze the thermal transition
between NS5 branes and Little String Theory, finding compelling evidence for
information recovering. We find that once the near horizon limit is taken the
emission of a full family of models is exactly thermal even if back-reaction is
taken into account. Consequently these theories are non-unitary and can not
convey any information about the black hole internal states. It is argue that
this behaviour matches the string theory expectations. We suggest a plausible
reason for the vanishing of the jet-quenching parameter in such theories.Comment: 18 pages, harvma
Polyakov loop correlators from D0-brane interactions in bosonic string theory
In this paper we re-derive the effective Nambu-Goto theory result for the
Polyakov loop correlator, starting from the free bosonic string and using a
covariant quantization. The boundary conditions are those of an open string
attached to two D0-branes at spatial distance R, in a target space with compact
euclidean time. The one-loop free energy contains topologically distinct
sectors corresponding to multiple covers of the cylinder in target space
bordered by the Polyakov loops. The sector that winds once reproduces exactly
the Nambu-Goto partition function. In our approach, the world-sheet duality
between the open and closed channel is most evident and allows for an explicit
interpretation of the free energy in terms of tree level exchange of closed
strings between boundary states. Our treatment is fully consistent only in
d=26; extension to generic d may be justified for large R, and is supported by
Montecarlo data. At shorter scales, consistency and Montecarlo data seem to
suggest the necessity of taking into account the Liouville mode of Polyakov's
formulation.Comment: 17 pages, 4 figures, minor corrections, a few references added,
version accepted for publication in JHE
Superconformal Multi-Black Hole Moduli Spaces in Four Dimensions
Quantum mechanics on the moduli space of N supersymmetric Reissner-Nordstrom
black holes is shown to admit 4 supersymmetries using an unconventional
supermultiplet which contains 3N bosons and 4N fermions. A near-horizon limit
is found in which the quantum mechanics of widely separated black holes
decouples from that of strongly-interacting, near-coincident black holes. This
near-horizon theory is shown to have an enhanced D(2,1;0) superconformal
symmetry. The bosonic symmetries are SL(2,R) conformal symmetry and SU(2)xSU(2)
R-symmetry arising from spatial rotations and the R-symmetry of N=2
supergravity.Comment: 23 pages, harvmac. v2: many typos fixe
Tachyons in Compact Spaces
We discuss condensations of closed string tachyons localized in compact
spaces. Time evolution of an on-shell condensation is naturally related to the
worldsheet RG flow. Some explicit tachyonic compactifications of Type II string
theory is considered, and some of them are shown to decay into supersymmetric
theories known as the little string theories.Comment: 14 page
Orientifolds of SU(2)/U(1) WZW Models
The orientifolds of SU(2)/U(1) gauged WZW models are investigated. In
particular, we construct the new type orientifolds and identify their
geometries. We closely follow the analysis of D-branes in the SU(2)/U(1) WZW
models, which was given by Maldacena, Moore and Seiberg.Comment: 33 pages, 3 figures, the geometry of orientifolds corrected and the
spectral flow identification reconsidere
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