227 research outputs found
Modulus Stabilization with Bulk Fields
We propose a mechanism for stabilizing the size of the extra dimension in the
Randall-Sundrum scenario. The potential for the modulus field that sets the
size of the fifth dimension is generated by a bulk scalar with quartic
interactions localized on the two 3-branes. The minimum of this potential
yields a compactification scale that solves the hierarchy problem without fine
tuning of parameters.Comment: 8 pages, LaTeX; minor typo correcte
On the strongly coupled heterotic string
We analyze in detail the anomaly cancellation conditions for the strongly
coupled heterotic string introduced by Horava and Witten and
find new features compared to the ten-dimensional Green-Schwarz mechanism. We
project onto ten dimensions the corresponding Lagrangian of the zero-mode
fields. We find that it has a simple interpretation provided by the conjectured
heterotic string/fivebrane duality. The part which originates from
eleven-dimensions is naturally described in fivebrane language. We discuss
physical couplings and scales in four dimensions.Comment: Latex, 14 pages, Misprints correcte
A Note on Marginally Stable Bound States in Type II String Theory
Spectrum of elementary string states in type II string theory contains
ultra-short multiplets that are marginally stable. -duality transformation
converts these states into bound states at threshold of -branes carrying
Ramond-Ramond charges, and wrapped around -cycles of a torus. We propose a
test for the existence of these marginally stable bound states. Using the
recent results of Polchinski and of Witten, we argue that the spectrum of bound
states of -branes is in agreement with the prediction of -duality.Comment: LaTeX file, 6 page
Fate of Kaluza-Klein Bubble
We numerically study classical time evolutions of Kaluza-Klein bubble
space-time which has negative energy after a decay of vacuum. As the zero
energy Witten's bubble space-time, where the bubble expands infinitely, the
subsequent evolutions of Brill and Horowitz's momentarily static initial data
show that the bubble will expand in terms of the area. At first glance, this
result may support Corley and Jacobson's conjecture that the bubble will expand
forever as well as the Witten's bubble. The irregular signatures, however, can
be seen in the behavior of the lapse function in the maximal slicing gauge and
the divergence of the Kretchman invariant. Since there is no appearance of the
apparent horizon, we suspect an appearance of a naked singularity as the final
fate of this space-time.Comment: 13 pages including 10 figures, RevTeX, epsf.sty. CGPG-99/12-8,
RESCEU-6/00 and DAMTP-2000-30. To appear in Phys. Rev.
Orientifold and Type II Dual Pairs
In this paper we present a symmetry of a toroidally compactified type II
string theory. This symmetry has the interpretaion that it interchanges the
left and the right-moving worldsheet coordinates and reverses the orientations
of some of the spatial coordinates. We also identify another discrete symmetry
of the type II theory which is related to the above one by a nontrivial
U-duality element of string theory. This symmetry, however, has trivial action
on the worldsheet coordinates and corresponds to an improper T-duality
rotation. We then construct examples of type II dual pairs in four dimensions
by modding out the known type II dual pairs by the above symmetries. We show
the explicit matching of the spectrum and supersymmetries in these examples.Comment: 17 page
K-Theory and S-Duality: Starting Over from Square 3
Recently Maldacena, Moore, and Seiberg (MMS) have proposed a physical
interpretation of the Atiyah-Hirzebruch spectral sequence, which roughly
computes the K-homology groups that classify D-branes. We note that in IIB
string theory, this approach can be generalized to include NS charged objects
and conjecture an S-duality covariant, nonlinear extension of the spectral
sequence. We then compute the contribution of the MMS double-instanton
configuration to the derivation d_5. We conclude with an M-theoretic
generalization reminiscent of 11-dimensional E_8 gauge theory.Comment: 27 pages, 3 figure
Hierarchies without Symmetries from Extra Dimensions
It is commonly thought that small couplings in a low-energy theory, such as
those needed for the fermion mass hierarchy or proton stability, must originate
from symmetries in a high-energy theory. We show that this expectation is
violated in theories where the Standard Model fields are confined to a thick
wall in extra dimensions, with the fermions "stuck" at different points in the
wall. Couplings between them are then suppressed due to the exponentially small
overlaps of their wave functions. This provides a framework for understanding
both the fermion mass hierarchy and proton stability without imposing
symmetries, but rather in terms of higher dimensional geography. A model
independent prediction of this scenario is non-universal couplings of the
Standard Model fermions to the ``Kaluza-Klein'' excitations of the gauge
fields. This allows a measurement of the fermion locations in the extra
dimensions at the LHC or NLC if the wall thickness is close to the TeV scale.Comment: 25 pages, 7 figure
S-Theory
The representation theory of the maximally extended superalgebra with 32
fermionic and 528 bosonic generators is developed in order to investigate
non-perturbative properties of the democratic secret theory behind strings and
other p-branes. The presence of Lorentz non-singlet central extensions is
emphasized, their role for understanding up to 13 hidden dimensions and their
physical interpretation as boundaries of p-branes is elucidated. The criteria
for a new larger set of BPS-like non-perturbative states is given and the
methods of investigation are illustrated with several explicit examples.Comment: Latex, 18 papge
Sources for Chern-Simons theories
The coupling between Chern-Simons theories and matter sources defined by
branes of different dimensionalities is examined. It is shown that the standard
coupling to membranes, such as the one found in supergravity or in string
theory, does not operate in the same way for CS theories; the only p-branes
that naturally couple seem to be those with p=2n; these p-branes break the
gauge symmetry (and supersymmetry) in a controlled and sensible manner.Comment: 17 pages, Dedicated to Claudio Bunster on the occasion of his 60th
birthday. To appear in Quantum Mechanics of Fundamental Systems: The Quest
for Beauty and Simplicit
Indirect Collider Signals for Extra Dimensions
A recent suggestion that quantum gravity may become strong near the weak
scale has several testable consequences. In addition to probing for the new
large (submillimeter) extra dimensions associated with these theories via
gravitational experiments, one could search for the Kaluza Klein towers of
massive gravitons which are predicted in these models and which can interact
with the fields of the Standard Model. Here we examine the indirect effects of
these massive gravitons being exchanged in fermion pair production in \epem
annihilation and Drell-Yan production at hadron colliders. In the latter case,
we examine a novel feature of this theory, which is the contribution of gluon
gluon initiated processes to lepton pair production. We find that these
processes provide strong bounds, up to several TeV, on the string scale which
are essentially independent of the number of extra dimensions. In addition, we
analyze the angular distributions for fermion pair production with spin-2
graviton exchanges and demonstrate that they provide a smoking gun signal for
low-scale quantum gravity which cannot be mimicked by other new physics
scenarios.Comment: Corrected typos, added table and reference
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