715 research outputs found
2-d Gravity as a Limit of the SL(2,R) Black Hole
The transformation of the black hole under a boost of the
subgroup U(1) is studied. It is found that the tachyon vertex operators of the
black hole go into those of the conformal field theory coupled to
gravity. The discrete states of the black hole also tend to the discrete states
of the 2-d gravity theory. The fate of the extra discrete states of the black
hole under boost are discussed.Comment: LaTeX file, 14 page
Vector-Chiral Equivalence in Null Gauged WZNW Theory
We consider the standard vector and chiral gauged WZNW models by their gauged
maximal null subgroups and show that they can be mapped to each other by a
special transformation. We give an explicit expression for the map in the case
of the classical Lie groups , , , , and note its
connection with the duality map for the Riemmanian globally symmetric spaces.Comment: 13 pages, LaTe
A Unified Scheme for Modular Invariant Partition Functions of WZW Models
We introuduce a unified method which can be applied to any WZW model at
arbitrary level to search systematically for modular invariant physical
partition functions. Our method is based essentially on modding out a known
theory on group manifold by a discrete group .
We apply our method to with , and to
models, and obtain all the known partition functions and some
new ones, and give explicit expressions for all of them.Comment: 30 page ,SUTDP/11/93/72 Department of Physics, Sharif University of
Technolog
Nilpotent Gauging of SL(2,R) models, and Liouville Field
We consider the gauging of WZNW model by its nilpotent subgroup
E(1). The resulting space-time of the corresponding sigma model is seen to
collapse to a one dimensional field theory of Liouville. Gauging the diagonal
subgroup of theory yields an
extremal three dimensional black string. We show that these solutions are
obtained from the two dimensional black hole of Witten and the three
dimensional black string of Horne and Horowitz by boosting the gauge group.Comment: 17 pages, late
Noncommutative SO(n) and Sp(n) Gauge Theories
We study the generalization of noncommutative gauge theories to the case of
orthogonal and symplectic groups. We find out that this is possible, since we
are allowed to define orthogonal and symplectic subgroups of noncommutative
unitary gauge transformations even though the gauge potentials and gauge
transformations are not valued in the orthogonal and symplectic subalgebras of
the Lie algebra of antihermitean matrices. Our construction relies on an
antiautomorphism of the basic noncommutative algebra of functions which
generalizes the charge conjugation operator of ordinary field theory. We show
that the corresponding noncommutative picture from low energy string theory is
obtained via orientifold projection in the presence of a non-trivial NSNS
B-field.Comment: 17 pages; considerations about fermions added and some minor change
Short communication: Occurrence of Ophidonais serpentina in Potamon persicum from Jajrood River, Iran
Crustaceans are ecologically important, because of their effective role in food web and community structure of ecosystems. Taxonomic identity of fresh water crabs has been studied in Iran representing Potamidae family as dominant fluvial crabs. In 2001 Khatami recorded an unknown oligochaete in the mantle cavity of fresh water crab Potamon persicum. The present study further separated and identified an oligochaete from Potamon persicum in Jajrood River, east of Tehran, Iran. Two hundred and fifteen specimens of Potamon persicum were collected using a trap during four seasons from Jajrood River (51° 41´ to 51° 48´N and 35° 37´ to 35° 47´E) during March to August 2004. The specimens were taken to the research laboratory, dissected after biometry
and the mantle and branchial cavities were examined for the existence of oligochaetes
Gauge Invariant Cutoff QED
A hidden generalized gauge symmetry of a cutoff QED is used to show the
renormalizability of QED. In particular, it is shown that corresponding Ward
identities are valid all along the renormalization group flow. The exact
Renormalization Group flow equation corresponding to the effective action of a
cutoff lambda phi^4 theory is also derived. Generalization to any gauge group
is indicated.Comment: V1: 18 pages, 2 figures; V2: Discussions improved. Version accepted
for publication in Physica Script
BRST Quantization of Noncommutative Gauge Theories
In this paper, the BRST symmetry transformation is presented for the
noncommutative U(N) gauge theory. The nilpotency of the charge associated to
this symmetry is then proved. As a consequence for the space-like
non-commutativity parameter, the Hilbert space of physical states is determined
by the cohomology space of the BRST operator as in the commutative case.
Further, the unitarity of the S-matrix elements projected onto the subspace of
physical states is deduced.Comment: 20 pages, LaTeX, no figures, one reference added, to appear in Phys.
Rev.
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