25 research outputs found
New and old N=8 superconformal field theories in three dimensions
We show that an infinite family of N=6 d=3 superconformal Chern-Simons-matter
theories has hidden N=8 superconformal symmetry and hidden parity on the
quantum level. This family of theories is different from the one found by
Aharony, Bergman, Jafferis and Maldacena, as well as from the theories
constructed by Bagger and Lambert, and Gustavsson. We also test several
conjectural dualities between BLG theories and ABJ theories by comparing
superconformal indices of these theories.Comment: 16 pages, late
Four-Dimensional Superconformal Theories with Interacting Boundaries or Defects
We study four-dimensional superconformal field theories coupled to
three-dimensional superconformal boundary or defect degrees of freedom.
Starting with bulk N=2, d=4 theories, we construct abelian models preserving
N=2, d=3 supersymmetry and the conformal symmetries under which the
boundary/defect is invariant. We write the action, including the bulk terms, in
N=2, d=3 superspace. Moreover we derive Callan-Symanzik equations for these
models using their superconformal transformation properties and show that the
beta functions vanish to all orders in perturbation theory, such that the
models remain superconformal upon quantization. Furthermore we study a model
with N=4 SU(N) Yang-Mills theory in the bulk coupled to a N=4, d=3
hypermultiplet on a defect. This model was constructed by DeWolfe, Freedman and
Ooguri, and conjectured to be conformal based on its relation to an AdS
configuration studied by Karch and Randall. We write this model in N=2, d=3
superspace, which has the distinct advantage that non-renormalization theorems
become transparent. Using N=4, d=3 supersymmetry, we argue that the model is
conformal.Comment: 30 pages, 4 figures, AMSLaTeX, revised comments on Chern-Simons term,
references adde
AdS Branes Corresponding to Superconformal Defects
We investigate an AdS_4 x L_2 D5-brane in AdS_5 x X_5 space-time, in the
context of AdS/dCFT correspondence. Here, X_5 is a Sasaki-Einstein manifold and
L_2 is a submanifold of X_5. This brane has the same supersymmetry as the
3-dimensional N=1 superconformal symmetry if L_2 is a special Legendrian
submanifold in X_5. In this case, this brane is supposed to correspond to a
superconformal wall defect in 4-dimensional N=4 super Yang-Mills theory. We
construct these new string backgrounds and show they have the correct
supersymmetry, also in the case with non-trivial gauge flux on L_2. The
simplest new example is AdS_4 x T^2 brane in AdS_5 x S^5. We construct the
brane solution expressing the RG flow between two different defects. We also
perform similar analysis for an AdS_3 x L_3 M5-brane in AdS_4 x X_7, for a weak
G_2 manifold X_7 and its submanifold L_3. This system has the same
supersymmetry as 2-dimensional N=(1,0) global superconformal symmetry, if L_3
is an associative submanifold.Comment: 22 pages, LaTeX, 3 figures. v2: typos corrected, references added.
v3: typos correcte
(De)constructing Intersecting M5-branes
We describe intersecting M5-branes, as well as M5-branes wrapping the
holomorphic curve xy=c, in terms of a limit of a defect conformal field theory
with two-dimensional (4,0) supersymmetry. This dCFT describes the low-energy
theory of intersecting D3-branes at a C^2/Z_k orbifold. In an appropriate k ->
infinity limit, two compact spatial directions are generated. By identifying
moduli of the M5-M5 intersection in terms of those of the dCFT, we argue that
the SU(2)_L R-symmetry of the (4,0) defect CFT matches the SU(2) R-symmetry of
the N =2, d=4 theory of the M5-M5 intersection. We find a 't Hooft anomaly in
the SU(2)_L R-symmetry, suggesting that tensionless strings give rise to an
anomaly in the SU(2) R-symmetry of intersecting M5-branes.Comment: latex, 25 pages, 4 figure
Holography and Defect Conformal Field Theories
We develop both the gravity and field theory sides of the Karch-Randall
conjecture that the near-horizon description of a certain D5-D3 brane
configuration in string theory, realized as AdS_5 x S^5 bisected by an AdS_4 x
S^2 "brane", is dual to N=4 Super Yang-Mills theory in R^4 coupled to an R^3
defect. We propose a complete Lagrangian for the field theory dual, a novel
"defect superconformal field theory" wherein a subset of the fields of N=4 SYM
interacts with a d=3 SU(N) fundamental hypermultiplet on the defect preserving
conformal invariance and 8 supercharges. The Kaluza-Klein reduction of wrapped
D5 modes on AdS_4 x S^2 leads to towers of short representations of OSp(4|4),
and we construct the map to a set of dual gauge-invariant defect operators O_3
possessing integer conformal dimensions. Gravity calculations of and
are given. Spacetime and N-dependence matches expectations from dCFT,
while the behavior as functions of lambda = g^2 N at strong and weak coupling
is generically different. We comment on a class of correlators for which a
non-renormalization theorem may still exist. Partial evidence for the
conformality of the quantum theory is given, including a complete argument for
the special case of a U(1) gauge group. Some weak coupling arguments which
illuminate the duality are presented.Comment: 47 pages, LaTeX, 2 figures, feynmf. v2: fixed minor errors, added
references. v3: fixed more typo
On Flux Quantization in F-Theory
We study the problem of four-form flux quantization in F-theory
compactifications. We prove that for smooth, elliptically fibered Calabi-Yau
fourfolds with a Weierstrass representation, the flux is always integrally
quantized. This implies that any possible half-integral quantization effects
must come from 7-branes, i.e. from singularities of the fourfold. We
subsequently analyze the quantization rule on explicit fourfolds with Sp(N)
singularities, and connect our findings via Sen's limit to IIB string theory.
Via direct computations we find that the four-form is half-integrally quantized
whenever the corresponding 7-brane stacks wrap non-spin complex surfaces, in
accordance with the perturbative Freed-Witten anomaly. Our calculations on the
fourfolds are done via toric techniques, whereas in IIB we rely on Sen's
tachyon condensation picture to treat bound states of branes. Finally, we give
general formulae for the curvature- and flux-induced D3 tadpoles for general
fourfolds with Sp(N) singularities.Comment: 46 page
Intersecting D3-branes and Holography
We study a defect conformal field theory describing D3-branes intersecting
over two space-time dimensions. This theory admits an exact Lagrangian
description which includes both two- and four-dimensional degrees of freedom,
has (4,4) supersymmetry and is invariant under global conformal
transformations. Both two- and four-dimensional contributions to the action are
conveniently obtained in a two-dimensional (2,2) superspace. In a suitable
limit, the theory has a dual description in terms of a probe D3-brane wrapping
an AdS_3 x S^1 slice of AdS_5 x S^5. We consider the AdS/CFT dictionary for
this set-up. In particular we find classical probe fluctuations corresponding
to the holomorphic curve wy=c\alpha^{\prime}. These fluctuations are dual to
defect fields containing massless two-dimensional scalars which parameterize
the classical Higgs branch, but do not correspond to states in the Hilbert
space of the CFT. We also identify probe fluctuations which are dual to BPS
superconformal primary operators and to their descendants. A
non-renormalization theorem is conjectured for the correlators of these
operators, and verified to order g^2.Comment: 46 pages, 5 figures, Latex, minor corrections to section 4.2, version
published in Phys. Rev.
Holographic Interface-Particle Potential
We consider two N=4 supersymmetric gauge theories connected by an interface
and the gravity dual of this system. This interface is expressed by a fuzzy
funnel solution of Nahm's equation in the gauge theory side. The gravity dual
is a probe D5-brane in AdS_5 x S^5. The potential energy between this interface
and a test particle is calculated in both the gauge theory side and the gravity
side by the expectation value of a Wilson loop. In the gauge theory it is
evaluated by just substituting the classical solution to the Wilson loop. On
the other hand it is done by the on-shell action of the fundamental string
stretched between the AdS boundary and the D5-brane in the gravity. We show the
gauge theory result and the gravity one agree with each other.Comment: 18 pages, 3 figures. v2: added discussion on perturbative corrections
in the gauge theory sid