429 research outputs found
A New Lorentz Violating Nonlocal Field Theory From String-Theory
A four-dimensional field theory with a qualitatively new type of nonlocality
is constructed from a setting where Kaluza-Klein particles probe toroidally
compactified string theory with twisted boundary conditions. In this theory
fundamental particles are not pointlike and occupy a volume proportional to
their R-charge. The theory breaks Lorentz invariance but appears to preserve
spatial rotations. At low energies, it is approximately N=4 Super Yang-Mills
theory, deformed by an operator of dimension seven. The dispersion relation of
massless modes in vacuum is unchanged, but under certain conditions in this
theory, particles can travel at superluminal velocities.Comment: references adde
On the Twisted (2,0) and Little-String Theories
We study the compactification of the and type-II little-string
theories on , and with an R-symmetry twist that preserves half
the supersymmetry. We argue that it produces the same moduli spaces of vacua as
compactification of the theory with Wilson lines given by a
maximal embedding of SU(2). In certain limits, this reproduces the moduli space
of SU(2) with a massive adjoint hyper-multiplet. In the type-II little-string
theory case, we observe a peculiar phase transition where the strings condense.
We conjecture a generalization to more than two 5-branes which involves
instantons on non-commutative . We conclude with open questions.Comment: 27pp TeX, one eps figur
Correlators of the Global Symmetry Currents of 4D and 6D Superconformal Theories
We study the two-point correlators of the currents of the global
symmetry in the superconformal six-dimensional theory as well as in
the 4D superconformal theories upon toroidal compactification. From the
high-energy behavior of the correlator we deduce that in 4D 10 copies of the
superconformal theory with global symmetry can be coupled to an N=2
gauge theory. We present three alternative derivations for the expression for
the correlators. One from field-theory, one from M-theory and one from
F-theory.Comment: 25pp harvmac TeX with one eps figur
Classical self-dual strings in d=6, (2,0) theory from afar
We show how one can get solitonic strings in a six-dimensional (2,0)
supersymmetric theory by incorporating a nonlinear interaction term. We derive
a zero force condition between parallel strings, and compute a metric on a
moduli space which is when the strings are far apart. When compactifying
the strings on a two-torus we show that, in the limit of vanishing two-torus,
one regains the moduli space of two widely separated dyons of equal magnetic
charges in four dimensions.Comment: 13 pages, clarifications and added reference
Noncommutative Geometry from D0-branes in a Background B-field
We study D0-branes in type IIA on with a background B-field turned on.
We calculate explicitly how the background B-field modifies the D0-brane
action. The effect of the B-field is to replace ordinary multiplication with a
noncommutative product. This enables us to find the matrix model for M-theory
on with a background 3-form potential along the torus and the lightlike
circle. This matrix model is exactly the non-local 2+1 dim SYM theory on a dual
proposed by Connes, Douglas and Schwarz. We calculate the radii and the
gauge coupling for the SYM on the dual for all choices of longitudinal
momentum and membrane wrapping number on the .Comment: 13pp, harvmac with five eps figures; final version in Nuclear Physics
Index theorem for topological excitations on R^3 * S^1 and Chern-Simons theory
We derive an index theorem for the Dirac operator in the background of
various topological excitations on an R^3 \times S^1 geometry. The index
theorem provides more refined data than the APS index for an instanton on R^4
and reproduces it in decompactification limit. In the R^3 limit, it reduces to
the Callias index theorem. The index is expressed in terms of topological
charge and the eta-invariant associated with the boundary Dirac operator.
Neither topological charge nor eta-invariant is typically an integer, however,
the non-integer parts cancel to give an integer-valued index. Our derivation is
based on axial current non-conservation--an exact operator identity valid on
any four-manifold--and on the existence of a center symmetric, or approximately
center symmetric, boundary holonomy (Wilson line). We expect the index theorem
to usefully apply to many physical systems of interest, such as low temperature
(large S^1, confined) phases of gauge theories, center stabilized Yang-Mills
theories with vector-like or chiral matter (at S^1 of any size), and
supersymmetric gauge theories with supersymmetry-preserving boundary conditions
(also at any S^1). In QCD-like and chiral gauge theories, the index theorem
should shed light into the nature of topological excitations responsible for
chiral symmetry breaking and the generation of mass gap in the gauge sector. We
also show that imposing chirally-twisted boundary condition in gauge theories
with fermions induces a Chern-Simons term in the infrared. This suggests that
some QCD-like gauge theories should possess components with a topological
Chern-Simons phase in the small S^1 regime.Comment: 29 pages, refs added, published versio
A note on M(atrix) theory in seven dimensions with eight supercharges
We consider M(atrix) theory compactifications to seven dimensions with eight
unbroken supersymmetries. We conjecture that both M(atrix) theory on K3 and
Heterotic M(atrix) theory on T^3 are described by the same 5+1 dimensional
theory with N=2 supersymmetry which is broken to N=1 by the base space. The
emergence of the extra dimension follows from a recent result of
Rozali[hep-th/9702136]. We show that the seven dimensional duality between
M-theory on K3 and Heterotic string theory on T^3 is realised in M(atrix)
theory as the exchange of one of the dimensions with this new dimension.Comment: RevTeX, 8 pages, version to appear in journa
The Self-Dual String and Anomalies in the M5-brane
We study the anomalies of a charge self-dual string solution in the
Coulomb branch of M5-branes. Cancellation of these anomalies allows us to
determine the anomaly of the zero-modes on the self-dual string and their
scaling with and . The dimensional reduction of the five-brane
anomalous couplings then lead to certain anomalous couplings for D-branes.Comment: 13 pages, Harvmac, refs adde
Couplings of self-dual tensor multiplet in six dimensions
The (1,0) supersymmetry in six dimensions admits a tensor multiplet which
contains a second-rank antisymmetric tensor field with a self-dual field
strength and a dilaton. We describe the fully supersymmetric coupling of this
multiplet to Yang-Mills multiplet, in the absence of supergravity. The
self-duality equation for the tensor field involves a Chern-Simons modified
field strength, the gauge fermions, and an arbitrary dimensionful parameter.Comment: 17 pages, latex, no figure
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