18 research outputs found
Low Energy Supersymmetry From the Landscape
There has been some debate as to whether the landscape does or does not
predict low energy supersymmetry. We argue that under rather mild assumptions,
the landscape seems to favor such breaking, quite possibly at a very low scale.
Some of the issues which must be addressed in order to settle these questions
are the relative frequency with which tree level and non-perturbative effects
generate expectation values for auxillary fields and the superpotential, as
well as the likelihood of both - and non- discrete or accidental
symmetries. Alternate scenarios with warped compactifications or large extra
dimensions are also discussed.Comment: latex, 19 page
Catastrophic Decays of Compactified Space-Times
Witten long ago pointed out that the simplest Kaluza-Klein theory, without
supersymmetry, is subject to a catastrophic instability. There are a variety of
string theories which are potentially subject to these instabilities. Here we
explore a number of questions: how generic are these instabilities? what
happens when a potential is generated on the moduli space? in the presence of
supersymmetry breaking, is there still a distinction between supersymmetric and
non-supersymmetric states?Comment: Typos corrected, references adde
Evidence for Winding States in Noncommutative Quantum Field Theory
We study noncommutative field theories at finite temperature to learn more
about the degrees of freedom in the non-planar sector of these systems. We find
evidence for winding states. At temperatures for which the thermal wavelength
is smaller than the noncommutativity scale, there is a drastic reduction of the
degrees of freedom in the non-planar sector. In this regime, the non-planar
sector has thermodynamics resembling that of a 1+1 dimensional field theory.Comment: 15 pages, 3 figures. Typos corrected and minor clarifications adde
Closed String Tachyons and Their Implications for Non-Supersymmetric Strings
Closed string tachyons have long been somewhat mysterious. We note that there
is often a regime in the classical moduli space in which one can systematically
compute the effective action for such fields. In this regime, the tachyon is
light, and cannot be integrated out. Instead, one must consider the combined
dynamics of gravitons, moduli, tachyons and other light fields. We compute the
action and find that the quartic term for the tachyon is positive in the field
definition where the tachyon has no derivative coupling to the radion. We study
the evolution of isotropic, homogeneous configurations and find that typically
the system is driven to regions where the calculation is no longer under
control.Comment: 10 pages, no figures, references adde
The Exact Superconformal R-symmetry Minimizes
We present a new, general constraint which, in principle, determines the
superconformal symmetry of 4d SCFTs, and also 3d
SCFTs. Among all possibilities, the superconformal is that which
minimizes the coefficient, , of its two-point function.
Equivalently, the superconformal is the unique one with vanishing
two-point function with every non-R flavor symmetry. For 4d SCFTs,
minimization gives an alternative to a-maximization.
minimization also applies in 3d, where no condition for determining the
superconformal had been previously known. Unfortunately, this
constraint seems impractical to implement for interacting field theories. But
it can be readily implemented in the AdS geometry for SCFTs with AdS duals.Comment: 18 page
A Note on (Meta)stable Brane Configurations in MQCD
We examine the M-theory version of SQCD which is known as MQCD. In the IIA
limit, this theory appears to have a supersymmetry-breaking brane configuration
which corresponds to the meta-stable state of N=1 SU(Nc) SQCD. However, the
behavior at infinity of this non-supersymmetric brane construction differs from
that of the supersymmetric ground state of MQCD. We interpret this to mean that
it is not a meta-stable state in MQCD, but rather a state in another theory.
This provides a concrete example of the fact that, while MQCD accurately
describes the supersymmetric features of SCQD, it fails to reproduce its
non-supersymmetric features (such as meta-stable states) not only
quantitatively but also qualitatively.Comment: 30 pages, 7 figures, harvmac. v2 typo correcte
Is There A String Theory Landscape
We examine recent claims of a large set of flux compactification solutions of
string theory. We conclude that the arguments for AdS solutions are plausible.
The analysis of meta-stable dS solutions inevitably leads to situations where
long distance effective field theory breaks down. We then examine whether these
solutions are likely to lead to a description of the real world. We conclude
that one must invoke a strong version of the anthropic principle. We explain
why it is likely that this leads to a prediction of low energy supersymmetry
breaking, but that many features of anthropically selected flux
compactifications are likely to disagree with experiment.Comment: 39 pages, Latex, ``Terminology surrounding the anthropic principle
revised to conform with accepted usage. More history of the anthropic
principle included. Various references added.