439 research outputs found
On Higher Derivative Couplings in Theories with Sixteen Supersymmetries
We give simple arguments for new non-renormalization theorems on higher
derivative couplings of gauge theories to supergravity, with sixteen
supersymmetries, by considerations of brane-bulk superamplitudes. This leads to
some exact results on the effective coupling of D3-branes in type IIB string
theory. We also derive exact results on higher dimensional operators in the
torus compactification of the six dimensional (0, 2) superconformal theory.Comment: 31 pages, 10 figures, section 2 reconstructured, new result in
section 3.2, additional clarifications adde
(2,2) Superconformal Bootstrap in Two Dimensions
We find a simple relation between two-dimensional BPS N=2 superconformal
blocks and bosonic Virasoro conformal blocks, which allows us to analyze the
crossing equations for BPS 4-point functions in unitary (2,2) superconformal
theories numerically with semidefinite programming. We constrain gaps in the
non-BPS spectrum through the operator product expansion of BPS operators, in
ways that depend on the moduli of exactly marginal deformations through chiral
ring coefficients. In some cases, our bounds on the spectral gaps are observed
to be saturated by free theories, by N=2 Liouville theory, and by certain
Landau-Ginzburg models.Comment: 56 pages, 14 figure
Supersymmetry Constraints and String Theory on K3
We study supervertices in six dimensional (2,0) supergravity theories, and
derive supersymmetry non-renormalization conditions on the 4- and 6-derivative
four-point couplings of tensor multiplets. As an application, we obtain exact
non-perturbative results of such effective couplings in type IIB string theory
compactified on K3 surface, extending previous work on type II/heterotic
duality. The weak coupling limit thereof, in particular, gives certain
integrated four-point functions of half-BPS operators in the nonlinear sigma
model on K3 surface, that depend nontrivially on the moduli, and capture
worldsheet instanton contributions.Comment: 47 pages, 4 figure
Romans Supergravity from Five-Dimensional Holograms
We study five-dimensional superconformal field theories and their holographic
dual, matter-coupled Romans supergravity. On the one hand, some recently
derived formulae allow us to extract the central charges from deformations of
the supersymmetric five-sphere partition function, whose large N expansion can
be computed using matrix model techniques. On the other hand, the conformal and
flavor central charges can be extracted from the six-dimensional supergravity
action, by carefully analyzing its embedding into type I' string theory. The
results match on the two sides of the holographic duality. Our results also
provide analytic evidence for the symmetry enhancement in five-dimensional
superconformal field theories.Comment: 57 pages, 4 figures, 6 tables; v2: references adde
Little String Amplitudes (and the Unreasonable Effectiveness of 6D SYM)
We study tree level scattering amplitudes of four massless states in the
double scaled little string theory, and compare them to perturbative loop
amplitudes in six-dimensional super-Yang-Mills theory. The little string
amplitudes are computed from correlators in the cigar coset CFT and in N=2
minimal models. The results are expressed in terms of integrals of conformal
blocks and evaluated numerically in the alpha' expansion. We find striking
agreements with up to 2-loop scattering amplitudes of massless gluons in 6D
SU(k) SYM at a Z_k invariant point on the Coulomb branch. We comment on the
issue of UV divergence at higher loop orders in the gauge theory and discuss
the implication of our results.Comment: 58 pages, 5 figures, 3 tables, comments added, references adde
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