8,076 research outputs found
Confining Flux Tubes in a Current Algebra Approach
We describe flux tubes and their interactions in a low energy sigma model
induced by flavor symmetry breaking in
QCD. Unlike standard QCD, this model allows gauge confinement to
manifest itself in the low energy theory, which has unscreened spinor color
sources and global flux tubes. We construct the flux tubes and show how
they mediate the confinement of spinor sources. We further examine the flux
tubes' quantum stability, spectrum and interactions. We find that flux tubes
are Alice strings, despite ambiguities in defining parallel transport.
Furthermore, twisted loops of flux tube support skyrmion number, just as gauged
Alice strings form loops that support monopole charge. This model, while
phenomenologically nonviable, thus affords a perspective on both the dynamics
of confinement and on subtleties which arise for global Alice strings.Comment: 29 pages (REVTEX) plus 6 figures, two corrections in the final
section and added reference
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
Evidence for a Lattice Weak Gravity Conjecture
The Weak Gravity Conjecture postulates the existence of superextremal charged
particles, i.e. those with mass smaller than or equal to their charge in Planck
units. We present further evidence for our recent observation that in known
examples a much stronger statement is true: an infinite tower of superextremal
particles of different charges exists. We show that effective Kaluza-Klein
field theories and perturbative string vacua respect the Sublattice Weak
Gravity Conjecture, namely that a finite index sublattice of the full charge
lattice exists with a superextremal particle at each site. In perturbative
string theory we show that this follows from modular invariance. However, we
present counterexamples to the stronger possibility that a superextremal
particle exists at every lattice site, including an example in which the
lightest charged particle is subextremal. The Sublattice Weak Gravity
Conjecture has many implications both for abstract theories of quantum gravity
and for real-world physics. For instance, it implies that if a gauge group with
very small coupling exists, then the fundamental gravitational cutoff
energy of the theory is no higher than .Comment: v2: 41 pages, typos fixed, references added, substantial revisions
and clarifications (conclusions unchanged
Supercurrents on Asymmetric Orbifolds
We study -heterotic string on asymmetric orbifolds associated
with semi-simple simply-laced Lie algebras. Using the fact that -model
allows different twists, we present a new N=1 space-time supersymmetric model
whose supercurrent appears from twisted sectors but not untwisted sector.Comment: 7 pages, Latex, KOBE-TH-93-0
5D Black Holes and Matrix Strings
We derive the world-volume theory, the (non)-extremal entropy and background
geometry of black holes and black strings constructed out of the NS IIA
fivebrane within the framework of matrix theory. The CFT description of strings
propagating in the black hole geometry arises as an effective field theory.Comment: 25 pages, latex, 1 figure, extended discussion of non-extremal
entrop
A Note on Softly Broken MQCD
We consider generic MQCD configurations with matter described by semi-infinte
D4-branes and softly broken supersymmetry. We show that the matter sector does
not introduce supersymmetry breaking parameters so that the most relevant
supersymmetry breaking operator at low energies is the gaugino mass term. By
studying the run-away properties of these models in the decoupling limit of the
adjoint matter, we argue that these softly broken MQCD configurations fail to
capture the infrared physics of QCD at scales below the gaugino mass scale.Comment: 10+1 pages, TeX. V2: small comments and acknowledgements added,
conclusions unchange
BPS Quantization of the Five-Brane
We give a unified description of all BPS states of M-theory compactified on
in terms of the five-brane. We compute the mass spectrum and degeneracies
and find that the U-duality symmetry naturally arises as a
T-duality by assuming that the world-volume theory of the five-brane itself is
described by a string theory. We also consider the compactification on , and give a new explanation for its correspondence with heterotic
string theory by exhibiting its dual equivalence to M-theory on .Comment: 27 pages, latex, no figures, to be published in Nucl. Phys. B,
discussion of relation to D-brane counting adde
Spin chain sigma models with fermions
The complete one-loop planar dilatation operator of N=4 supersymmetric
Yang-Mills is isomorphic to the hamiltonian of an integrable PSU(2,2|4) quantum
spin chain. We construct the non-linear sigma models describing the continuum
limit of the SU(1|3) and SU(2|3) sectors of the complete N=4 chain. We
explicitely identify the spin chain sigma model with the one for a superstring
moving in AdS_5xS^5 with large angular momentum along the five-sphere.Comment: 16 pages. Latex. v2: Misprints corrected and references adde
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