243 research outputs found
On four dimensional N=3 superconformal theories
In this note we study four dimensional theories with N=3 superconformal
symmetry, that do not also have N=4 supersymmetry. No examples of such theories
are known, but their existence is also not ruled out. We analyze several
properties that such theories must have. We show that their conformal anomalies
obey a=c. Using the N=3 superconformal algebra, we show that they do not have
any exactly marginal deformations preserving N=3 supersymmetry, or global
symmetries (except for their R-symmetries). Finally, we analyze the possible
dimensions of chiral operators labeling their moduli space.Comment: 11 pages. v2 : corrected statement about exactly marginal
deformations, added reference
IR Dynamics of d=2, N=(4,4) Gauge Theories and DLCQ of "Little String Theories"
We analyze the superconformal theories (SCFTs) which arise in the low-energy
limit of N=(4,4) supersymmetric gauge theories in two dimensions, primarily the
Higgs branch SCFT. By a direct field theory analysis we find a continuum of
"throat"-like states localized near the singularities of the Higgs branch. The
"throat" is similar to the "throat" found in the Coulomb branch of the same
theories, but the full superconformal field theories of the two branches are
different. A particular example is the SCFT of the R^4/Z_2 sigma model with
zero theta angle. In the application of the Higgs branch SCFTs to the DLCQ
description of "little string theories" (LSTs), the "throat" continuum is
identified with the continuum of "throat" states in the holographic description
of the LSTs. We also match the descriptions of the string interactions (in the
"throat" region) in the DLCQ and holographic descriptions of the N=(2,0) LSTs.Comment: 37 pages, harvmac. v2: very minor change
S-folds and 4d N=3 superconformal field theories
S-folds are generalizations of orientifolds in type IIB string theory, such
that the geometric identifications are accompanied by non-trivial S-duality
transformations. They were recently used by Garcia-Etxebarria and Regalado to
provide the first construction of four dimensional N=3 superconformal theories.
In this note, we classify the different variants of these N=3 preserving
S-folds, distinguished by an analog of discrete torsion, using both a direct
analysis of the different torsion classes and the compactification of the
S-folds to three dimensional M-theory backgrounds. Upon adding D3-branes, these
variants lead to different classes of N=3 superconformal field theories. We
also analyze the holographic duals of these theories, and in particular clarify
the role of discrete gauge and global symmetries in holography.Comment: 29 pages; v2: references adde
Note on the Quantum Mechanics of M Theory
We observe that the existence of black holes limits the extent to which M
Theory (or indeed any quantum theory of gravity) can be described by
conventional quantum mechanics. Although there is no contradiction with the
fundamental properties of quantum mechanics, one can prove that expectation
values of Heisenberg operators at fixed times cannot exist in an ordinary
asymptotic Lorentz frame. Only operators whose matrix elements between the
vacuum and energy eigenstates with energy greater than the Planck scale are
artificially cut off, can have conventional Green's functions. This implies a
Planck scale cutoff on the possible localization of measurements in time. A
similar behavior arises also in ``little string theories''. We argue that
conventional quantum mechanics in light cone time is compatible with the
properties of black holes if there are more than four non-compact flat
dimensions, and also with the properties of ``little string theories''. We
contrast these observations with what is known about M Theory in asymptotically
Anti-de Sitter spacetimes.Comment: JHEP latex, 16 pages; minor changes in the description of generic
little string theory state
Membrane Dynamics in M(atrix) Theory
We analyze some of the kinematical and dynamical properties of flat infinite
membrane solutions in the conjectured M theory proposed by Banks, Fischler,
Shenker and Susskind. In particular, we compute the long range potential
between membranes and anti-membranes, and between membranes and gravitons, and
compare it with the supergravity results. We also discuss membranes with finite
relative longitudinal velocities, providing some evidence for the eleven
dimensional Lorentz invariance of the theory.Comment: 20 pages, harvma
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