182 research outputs found

### Cascading Quivers from Decaying D-branes

We use an argument analogous to that of Kachru, Pearson and Verlinde to argue
that cascades in L^{a,b,c} quiver gauge theories always preserve the form of
the quiver, and that all gauge groups drop at each step by the number M of
fractional branes. In particular, we demonstrate that an NS5-brane that sweeps
out the S^3 of the base of L^{a,b,c} destroys M D3-branes.Comment: 11 pages, 1 figure; v2: references adde

### New Duality Transformations in Orbifold Theory

We find new duality transformations which allow us to construct the stress
tensors of all the twisted sectors of any orbifold A(H)/H, where A(H) is the
set of all current-algebraic conformal field theories with a finite symmetry
group H \subset Aut(g). The permutation orbifolds with H = Z_\lambda and H =
S_3 are worked out in full as illustrations but the general formalism includes
both simple and semisimple g. The motivation for this development is the
recently-discovered orbifold Virasoro master equation, whose solutions are
identified by the duality transformations as sectors of the permutation
orbifolds A(D_\lambda)/Z_\lambda.Comment: 48 pages,typos correcte

### From E_8 to F via T

We argue that T-duality and F-theory appear automatically in the E_8 gauge
bundle perspective of M-theory. The 11-dimensional supergravity four-form
determines an E_8 bundle. If we compactify on a two-torus, this data specifies
an LLE_8 bundle where LG is a centrally-extended loopgroup of G. If one of the
circles of the torus is smaller than sqrt(alpha') then it is also smaller than
a nontrivial circle S in the LLE_8 fiber and so a dimensional reduction on the
total space of the bundle is not valid. We conjecture that S is the circle on
which the T-dual type IIB theory is compactified, with the aforementioned torus
playing the role of the F-theory torus. As tests we reproduce the T-dualities
between NS5-branes and KK-monopoles, as well as D6 and D7-branes where we find
the desired F-theory monodromy. Using Hull's proposal for massive IIA, this
realization of T-duality allows us to confirm that the Romans mass is the
central extension of our LE_8. In addition this construction immediately
reproduces the conjectured formula for global topology change from T-duality
with H-flux.Comment: 25 pages, 4 eps figure

### Loop Groups, Kaluza-Klein Reduction and M-Theory

We show that the data of a principal G-bundle over a principal circle bundle
is equivalent to that of a \hat{LG} = U(1) |x LG bundle over the base of the
circle bundle. We apply this to the Kaluza-Klein reduction of M-theory to IIA
and show that certain generalized characteristic classes of the loop group
bundle encode the Bianchi identities of the antisymmetric tensor fields of IIA
supergravity. We further show that the low dimensional characteristic classes
of the central extension of the loop group encode the Bianchi identities of
massive IIA, thereby adding support to the conjectures of hep-th/0203218.Comment: 26 pages, LaTeX, utarticle.cls, v2:clarifications and refs adde

### The orbifold-string theories of permutation-type: II. Cycle dynamics and target space-time dimensions

We continue our discussion of the general bosonic prototype of the new
orbifold-string theories of permutation type. Supplementing the extended
physical-state conditions of the previous paper, we construct here the extended
Virasoro generators with cycle central charge
$\hat{c}_j(\sigma)=26f_j(\sigma)$, where $f_j(\sigma)$ is the length of cycle
$j$ in twisted sector $\sigma$. We also find an equivalent, reduced formulation
of each physical-state problem at reduced cycle central charge
$c_j(\sigma)=26$. These tools are used to begin the study of the target
space-time dimension $\hat{D}_j(\sigma)$ of cycle $j$ in sector $\sigma$, which
is naturally defined as the number of zero modes (momenta) of each cycle. The
general model-dependent formulae derived here will be used extensively in
succeeding papers, but are evaluated in this paper only for the simplest case
of the "pure" permutation orbifolds.Comment: 32 page

### The Orbifolds of Permutation-Type as Physical String Systems at Multiples of c=26 IV. Orientation Orbifolds Include Orientifolds

In this fourth paper of the series, I clarify the somewhat mysterious
relation between the large class of {\it orientation orbifolds} (with twisted
open-string CFT's at $\hat c=52$) and {\it orientifolds} (with untwisted open
strings at $c=26$), both of which have been associated to division by
world-sheet orientation-reversing automorphisms. In particular -- following a
spectral clue in the previous paper -- I show that, even as an {\it interacting
string system}, a certain half-integer-moded orientation orbifold-string system
is in fact equivalent to the archetypal orientifold. The subtitle of this
paper, that orientation orbifolds include and generalize standard orientifolds,
then follows because there are many other orientation orbifold-string systems
-- with higher fractional modeing -- which are not equivalent to untwisted
string systems.Comment: 22 pages, typos correcte

### The Orbifold-String Theories of Permutation-Type: I. One Twisted BRST per Cycle per Sector

We resume our discussion of the new orbifold-string theories of
permutation-type, focusing in the present series on the algebraic formulation
of the general bosonic prototype and especially the target space-times of the
theories. In this first paper of the series, we construct one twisted BRST
system for each cycle $j$ in each twisted sector $\sigma$ of the general case,
verifying in particular the previously-conjectured algebra
$[Q_{i}(\sigma),Q_{j}(\sigma)]_{+} =0$ of the BRST charges. The BRST systems
then imply a set of extended physical-state conditions for the matter of each
cycle at cycle central charge $\hat{c}_{j}(\sigma)=26f_{j}(\sigma)$ where
$f_{j}(\sigma)$ is the length of cycle $j$.Comment: 31 page

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